Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 04/04/08

AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
230 PM PDT THU APR 3 2008 .SYNOPSIS...A SLOWLY DRYING AIRMASS WILL RESULT IN PARTLY CLOUDY SKIES NEAR THE BEACHES AND MOSTLY CLOUDY SKIES REMAINING AREAS FROM THE COASTAL SLOPES OF THE MOUNTAINS WESTWARD THROUGH THIS EVENING. A NIGHT AND MORNING LOW CLOUDS AND FOG PATTERN WILL PREVAIL THROUGH THE WEEKEND INTO NEXT WEEK...WITH THE MOST PERSISTENT CLOUDINESS ON THE WEEKEND...THEN AGAIN AROUND THE MIDDLE OF NEXT WEEK. THERE COULD BE SOME DRIZZLE OVER THE WEEKEND...AND MAYBE SOME SHOWERS DURING THE MIDDLE OF NEXT WEEK. MOSTLY CLEAR AND BREEZY AT TIMES HIGHER MOUNTAIN AREAS AS WELL AS DESERT AREAS. && .DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO... ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES. .SHORT TERM (TONIGHT-SUN)... THE REGION HAS BEEN EXPERIENCING A REVERSE CLEARING PATTERN TODAY WITH THE TRANSFER TO A CONVECTIVE REGIME KEEPING INLAND AREAS CLOUDY. THE COOLER MARINE AIR HAS CREPT INTO THE COASTAL AREAS AND HAS STABILIZED THE ATMOSPHERE THERE TO KILL THE CONVECTION AND ALLOW MUCH SUNSHINE. TONIGHT WILL BE A BIT TRICKY WITHOUT A DECENT INVERSION TO WORK WITH AS THE MARINE LAYER INVERSION MAKES AN ATTEMPT TO RE-ESTABLISH ITSELF AT A MORE NORMAL LEVEL. THIS SHOULD LOWER THE CLOUDS THAT ARE ABLE TO FORM TONIGHT. THERE SHOULD BE AMPLE SUNSHINE FRIDAY UNDER INCREASING HIGH PRESSURE SURFACE AND ALOFT BEHIND THE LOW. THIS SHOULD ALLOW TEMPERATURES TO WARM UP SOME OVER TODAYS VALUES MOST AREAS. BY SATURDAY THE SCENARIO GOES THE OTHER WAY AS AN UPPER LEVEL TROUGH OF LOW PRESSURE SLIPS SOUTH OVER THE INTERIOR WEST WITH INCREASING ONSHORE FLOW. THIS SHOULD RAPIDLY DEEPEN THE MARINE LAYER ON SATURDAY...WITH POSSIBLY SOME DRIZZLE DURING THE NIGHT AND MORNING HOURS. THE SUNDAY SCENARIO SHOULD STILL CONTAIN A DEEP MORNING MARINE LAYER...BUT THE CLEARING SHOULD BE BETTER. ONSHORE FLOW SHOULD ALSO STRENGTHEN SAT AND COMBINED WITH STRONGER WINDS ALOFT WILL CAUSE GUSTY WINDS IN THE MOUNTAINS AND DESERTS...BUT THEY SHOULD REMAIN BELOW ADVISORY STRENGTH WITH LOCAL GUSTS TO AROUND 40 MPH. THE WINDS SHOULD PICK UP AGAIN AROUND THE MIDDLE OF NEXT WEEK. && .LONG TERM (SUN-WED)...SLIGHT WARMING IS EXPECTED UNDER WEAK UPPER RIDGING SUNDAY AFTERNOON INTO EARLY NEXT WEEK. AN UPPER TROUGH APPROACHING FROM THE NW WILL BRING MORE CLOUDS AND COOLING WITH GUSTY WINDS IN THE MOUNTAINS AND DESERTS TOWARD THE MIDDLE OF NEXT WEEK. THIS LOW MAY CAUSE A SMALL CHANCE OF PRECIP TOWARD LATE TUE OR EARLY WED. && .AVIATION... 031915Z...TOP REPORTS AND LATE MORNING MDCRS SOUNDINGS INDICATE THE MOISTURE DEPTH OVER THE AREA HAS LOWERED TO AROUND 6000 FEET SINCE THIS EARLY THIS MORNING. EXPECT FURTHER LOWERING TO AROUND 4000 FEET TONIGHT. MULTIPLE BROKEN STRATOCU LAYERS OVER THE AREA WITH BASES BETWEEN 2500 AND 4500 FEET MSL WILL CONTINUE TO COVER THE INLAND AREAS THROUGH THE AFTERNOON WITH THE COASTAL SLOPES OF THE MOUNTAINS REMAINING OBSCURED. THE COASTAL AREAS SHOULD SCATTER OUT DURING THE AFTERNOON UNDER A REVERSE CLEARING PATTERN. EXPECT THE STRATOCU TO FILL IN ALONG THE COAST THIS EVENING WITH BASES BETWEEN 2500 AND 3000 FEET MSL. STRATOCU SHOULD BREAK UP DURING THE LATE MORNING HOURS ON FRIDAY. THE DESERT AREAS SHOULD REMAIN MOSTLY CLEAR WITH UNRESTRICTED VISIBILITIES THROUGH FRIDAY. && .SGX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC...SMALL AVIATION...HORTON
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
715 PM EDT THU APR 3 2008 .SYNOPSIS... LOW PRESSURE DEVELOPING OVER THE MISSISSIPPI VALLEY THIS EVENING WILL MOVE ACROSS PENNSYLVANIA ON FRIDAY AND SEND A SERIES OF FRONTS ACROSS THE AREA. THE FRONT WILL SETTLE TO THE SOUTH FRIDAY NIGHT AND THEN ANOTHER LOW PRESSURE SYSTEM WILL MOVE ALONG IT SATURDAY. DRIER WEATHER WILL ARRIVE SUNDAY AND REMAIN INTO EARLY NEXT WEEK. && .NEAR TERM /TONIGHT/... THE REGIONAL RADAR LOOP SHOWS THAT THE RAIN IS STEADILY MOVING TOWARD THE AREA FROM THE SOUTH AND WEST. DEW POINTS ACROSS EASTERN PENNSYLVANIA HAVE FALLEN TODAY AND THE DRY AIR MASS WILL REMAIN IN PLACE AS THE RAIN ARRIVES. IT IS POSSIBLE THAT A PERIOD OF SLEET MAY OCCUR AT THE ONSET ACROSS EASTERN PENNSYLVANIA AND NORTHERN NEW JERSEY. I HAVE INCLUDED THIS IN THE GRIDS AND TEXT FORECASTS. THE LOW TEMPERATURES WILL OCCUR SHORTLY AFTER THE RAIN AND OR SLEET BEGINS AND THE EVAPORATIONAL COOLING FACTOR REACHES ITS MAX. THE POCONOS AND SUSSEX COUNTY NEW JERSEY MAY HAVE A MORE PROLONGED PERIOD OF SLEET OR PERHAPS SOME SNOW. I WAS UNWILLING TO CHANGE THE PREVIOUS FORECAST OF UP TO AN INCH OF ACCUMULATION, SO I CHOSE TO KEEP THESE GRIDS AS THEY WERE AND LET THEM GO. QPF TONIGHT OF ONE THIRD TO TWO THIRDS OF AN INCH IS EXPECTED WITH STEADY RAINS CONTINUING FRIDAY MORNING. FLOODING CONCERNS NIL IN THE SHORT TERM. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... A WET PERIOD FOR SURE ! DEBATED WHETHER I SHOULD JUST WRITE RAIN...RAIN...RAIN IN THE ZONES, BUT OPTED JUST TO TWEAK THE COMPUTER WORDS FOR NOW. THE FIRST WAVE WILL PRODUCE STEADY RAINS AS IT MOVES BY FRIDAY AND THEN THE COLD FRONT WILL MOVE JUST OFFSHORE FRIDAY NIGHT. ANOTHER WAVE WILL MOVE ALONG IT SATURDAY AND BRING A RENEWAL OF RAINS DURING SATURDAY. WHILE I AM NOT EXPECTING A GREAT DEAL OF CONVECTION FRIDAY OR SATURDAY, I WILL LEAVE THE CHC FOR THUNDER IN THE SOUTHERN ZONES GIVING A NOD TO THE PREVIOUS GRIDS AND THE DAY2 SPC WHICH HAS A GENERAL T-STORM OUTLOOK FOR THE SRN AREAS. QPF FOR THE SHORT TERM PERIOD WILL BE FAIRLY SIGNIFICANT WITH THE LATEST SHORT TERM MODELS OFFERING (STORM TOTAL QPF OF) ONE TO TWO INCHES TOTALS NORTH AND PERHAPS 2 OR 3 INCHES SOUTH. THE SOUTHERN AREAS CAN HANDLE ANY EXTRA RAINFALL TO A GREATER DEGREE CONSIDERING THE SOIL TYPE AND CURRENT DROUGHT CONDITIONS. THE AREAS MORE SUSCEPTIBLE TO FLOODING ARE FURTHER NORTH ACROSS THE LEHIGH AND RARITAN VALLEYS. SINCE ANY FLOODING CONCERNS WILL TAKE PLACE LATER SATURDAY OR SATURDAY NIGHT AT THE EARLIEST, WE DECIDED NOT TO ISSUE ANY FLOOD WATCH AT THIS TIME. WE WILL LOOK AT THIS AGAIN ON FRIDAY. && .LONG TERM /SUNDAY THROUGH THURSDAY/... ONCE AGAIN, THIS IS A FAIRLY LOW CONFIDENCE FCST. THE GFS INDICATES THE COLD FRONT WILL BE THROUGH THE AREA AND SUNDAY WOULD BE PREDOMINANTLY DRY, AS HIGH PRESSURE BUILD IN. THE ECMWF BRINGS ANOTHER WAVE THROUGH THE AREA ON SUNDAY, WHICH WOULD KEEP MOST OF SUNDAY WET. THE CANADIAN IS SOMEWHERE IN THE MIDDLE. FOR NOW, WILL KEEP LATER SUNDAY DRY, BUT WILL NEED TO WATCH THIS. HIGH PRESSURE WILL THEN BUILD TO THE N, KEEPING E TO NE FLOW OVER THE REGION, POPS LOOK TO VERY LOW ON MONDAY AND SOME SCHC ON TUESDAY ATTM. THE GFS AND ECMWF ARE IN DECENT AGREEMENT ON THESE TOW DAYS. BY WEDNESDAY, BOTH MODELS BRING A LOW ACROSS THE UPR MS VLY AND A WARM FRONT WILL CROSS THE REGION, FOLLOWED BY A WEAK CDFNT ON THURSDAY. CHC POPS WILL REMAIN IN THE FCST ON THURSDAY WITH THE FRONT. TEMPS LOOK TO BE AOA NORMAL, WITH HIGHS MAINLY IN THE UPPER 50S TO 60S THRU THE PD. && .AVIATION /00Z FRIDAY THROUGH TUESDAY/... WITH THE CURRENT TAFS ABOUT TO BE ISSUED POOR CIGS AND VSBYS ARE EXPECTED TO OCCUR THROUGHOUT THE TAF FCST PERIOD. WE ARE EXPECTING IFR CONDITIONS TO DEVELOP TONIGHT AND CONTINUE INTO FRIDAY MORNING AT THE LEAST. THE LATEST ACARS SOUNDINGS FROM AROUND THE LOCAL AREA STILL SUPPORT THE POTENTIAL FOR SLEET AS THEY ARE CLOSE TO MODEL FORECAST SOUNDINGS WITH CONSIDERABLE DRY AIR JUST ABOVE THE SURFACE. AS THE COLUMN OF THE AIR MASS CONTINUES TO BE MOISTENED BY THE FALLING PRECIPITATION, WE EXPECT WIDESPREAD IFR CONDITIONS TO DEVELOP. RIGHT NOW WE DID NOT CARRY ANY LLWS IN THE TERMINAL FORECASTS AS THE FCST LLJ IS BELOW CRITERIA. THE KACY AND KMIV TERMINALS ARE THE MOST SUSCEPTIBLE BECAUSE OF THEIR CLOSER PROXIMITY TO THE STRONGER FORECAST JET. THE FORECAST MODELS ARE FORECASTING THE WARM FRONT TO LIFT NORTH THROUGH THE TERMINALS ON FRIDAY. PROBABLY NOT IN TIME TO PREVENT IFR CONDITIONS FROM OCCURRING DURING THE MORNING COMMUTE. THE LEAST CONFIDENCE ABOUT THIS OCCURRING ARE AT KRDG AND KABE. THAT IS THE REASON WE LEFT PRECIPITATION IN THROUGH THE END OF THE TAF FORECAST PERIOD. ELSEWHERE WHILE WE CAN NOT RULE OUT SOME PRECIPITATION, BELIEVE OVER HALF OF THAT FORECAST PERIOD WILL BE DRY. WITH THOSE TERMINALS EXPECTED TO BE IN THE WARM SECTOR WE DID SHOW IMPROVEMENT IN CIGS AND VSBYS ABOVE GUIDANCE TO MVFR LEVELS. OUTLOOK... LOW CIGS/VSBYS WILL LIKELY CONTINUE THROUGH SATURDAY WITH IMPROVING CONDITIONS ON SUNDAY. GENERALLY VFR CONDITIONS THEN INTO EARLY NEXT WEEK. && .MARINE... SMALL CRAFT ADVISORY FOR THE COASTAL WATERS BEGINNING TONIGHT AT 200 AM AND CONTINUING INTO ALL OF FRIDAY NIGHT. LATEST NAM AND GFS SUPPORT WINDS STRONG ENOUGH TO BUILD SEAS TO SCA CRITERIA. LATEST WAVEWATCH HAS WAVES UP TO 7 FT. EXPECT CONDITIONS TO REMAIN JUST BELOW SCA CRITERIA FOR THE BAY...THIS WILL NEED TO BE MONITORED. MAY NEED TO EXTEND SCA INTO SATURDAY DEPENDING ON HOW STRONG WINDS ARE POST FRONTAL PASSAGE. SEAS STAY RELATIVELY HIGH (NEAR SCA CONDITIONS) INTO EARLY NEXT WEEK WITH PROLONGED PERIOD OF ONSHORE FLOW WITH A LONG FETCH. USED WAVEWATCH GUIDANCE FOR WAVE GRIDS WILL LITTLE MODIFICATION. WAVES ON DE BAY BASED ON WIND FORECAST. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FROM 2 AM FRIDAY TO 6 AM EDT SATURDAY FOR ANZ450>455. && $$ SYNOPSIS...O`HARA NEAR TERM...O`HARA SHORT TERM...O`HARA LONG TERM...NIERENBERG AVIATION...GIGI/GSZAT MARINE...GSZAT
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
807 PM EDT THU APR 3 2008 .UPDATE/AVIATION... SIG EXPANSION OF CONVN ONGOING ATTM FM SE MO INTO WRN KY IN RESPONSE TO INCREASING LARGE SCALE ASCENT AHD OF LEAD SW TROUGH LIFTING QUICKLY EWD OUT OF ERN IA. HWVR THIS HAVING A DETRIMENTAL EFFECT SO FAR ON NWD MSTR TRANSPORT IN OTHERWISE FVRBL LOW-MID LVL WAA PATTN AND DENOTED AS SUCH W/LACK OF PCPN ECHOES ACRS NRN IN AND CERTAINLY ACCENTUATED BY LAST VESTIGE OF OLD POLAR RIDGE AND EXTREMELY DRY SUB CLOUD LYR IN PLACE. NONETHELESS XPC INCREASING LL SATURATION THROUGH MID EVENING W/INCREASING LARGE SCALE ASCENT AHD OF EJECTING VIGOROUS MID LVL TROUGH W/RECENT EXPANSION OF ECHOES ACRS CNTRL/NRN IL ON NOSE OF LL JET WITHIN SHARP LL THETA-E GRADIENT. BTR COMBINATION OF MODEST MID LVL LAPSE RATES AND THETA-E SUGGEST ANY ISOLD THUNDER THREAT THIS EVENING WILL REMAIN ACRS THE FAR SOUTH AND WILL DROP MENTION ACRS THE NORTH. MAIN CHG WRT TO GOING GRIDS WAS TO BACKUP CAT MENTION EARLIER THIS EVENING WHILE RAMPING THINGS DOWN QUICKLY FM 06-12Z AND DROPPING MENTION ALTOGETHER AFT 12Z XCP FAR SE EARLY GIVEN LOOK AT 18Z GUIDANCE AND TRENDS. VFR CONDS TO START WILL QUICKLY SPIRAL DOWNWARD INTO AT LEAST MVFR CIGS TWD MIDNIGHT AND LIKELY LWR BEYOND THAT ESP AT KFWA GIVEN MORE APPRECIABLE LL MSTR FLUX THERE. && .SHORT TERM (TONIGHT THROUGH FRIDAY AFTERNOON)... SUNNY TO PARTLY SUNNY DAY WITH TEMPS NEARING NORMAL COMING TO A CLOSE AS CLOUDS WILL START TO INVADE THE FORECAST AREA LATE THIS AFTERNOON INTO THE EVENING AHEAD OF THE NEXT SYSTEM DEVELOPING ACROSS THE SOONER STATE. SLIGHT TIMING/POSITION DIFFERENCES BETWEEN THE MAJOR AMERICAN MODELS GFS/NAM12. 12Z RUNS SHOWS GFS SLIGHTLY FASTER (3-6HRS) THAN THE 12Z NAM12/09Z SREF/12Z UKMET AND 12Z NGM. WILL LEAN TOWARDS THE CONSENSUS AND THE 09Z SREF WHICH BLENDS OUT SOME OF THOSE SLIGHT TIMING AND STRENGTH DIFFERENCES BUT HOLDS CLOSER TO THE NAM GROUPING. SFC BOUNDARY NEAR THE OH RIVER...WITH DEWPOINTS IN THE 20S ACROSS THE REGION WITH DEWPTS IN THE UPPER 40S AND 50S SOUTH OF THE BOUNDARY. ACARS SOUNDINGS FROM THIS MORNING SHOW DEEP AND IMMENSE LAYER OF DRY AIR FROM AROUND 925 TO 700MB. SFC DEPRESSIONS ACROSS THE REGION ARE MORE THAN 20 TO 30 DEGREES AT MOST SITES...IT WILL TAKE SOME TIME FOR THE LOWER LEVELS TO MOISTEN AND HAVE HELD OFF ANY SIGNIFICANT CHCS FOR POPS UNTIL THIS EVENING...MOST LIKELY AFTER 02-04Z AS THE FIRST SFC WAVE MOVES EAST ALONG THE BOUNDARY TOWARDS THE OHIO VALLEY PULLING MOISTURE FROM THE GULF INTO THE REGION. MODEST ISENT LIFT IN THE 290-295K SFCS AFT 00Z...WITH STRONG CONVERGENCE SEEN IN THE H850 AND H700 LVLS ACROSS THE REGION THRU ABOUT 06-08Z. VERY STRONG UPPER LVL JET OF 130-140 KTS WITH THE AREA POSSIBLY IN THE PREFERRED RIGHT ENTRANCE THRU ABOUT 12-15Z. ONE FINAL INGREDIENT IS POSSIBLE CSI/SLANTWISE INSTABILITY OR WEAK ELEVATED CAPE SEEN THROUGH THE 03-08Z TIMEFRAME ACROSS THE REGION WHICH WILL ALLOW FOR CHC OF THUNDER. HAVE KEPT VERY HIGH CAT POPS...BUT HAVE THEM MAINLY IN THE 03-08Z TIMEFRAME WITH CHC POPS ELSEWHERE. AS THE SIGNIFICANT MOISTENING OF THE LOWER LEVELS OCCURS THE CIGS WILL DROP THRU THE NIGHT...WEAK LIFT WILL REMAIN WITH THE JET SUPPORT MENTIONED EARLIER AND THE WEAKENING DEFORMATION AREA MOVING THRU...-DZ AND LIGHT RAIN WILL BE POSSIBLE THRU THE MORNING.AS EVERYTHING STARTS TO PULL FURTHER EAST THE CLOUDS MAY START TO LIFT AND BREAK SLIGHTLY BY LATE AFTERNOON. TEMPS WILL DROP INTO THE UPPER 30S OR LOWER 40S OVERNIGHT...AND WITH THICK CLOUD COVER MOST OF THE DAY ALONG WITH POSSIBLE LIGHT RAIN OR DZ AND NORTHERLY WINDS...LITTLE DIURNAL BUMP WILL HAPPEN FRIDAY WITH AFTN HIGHS BELOW NORMAL IN THE MID AND MAYBE UPPER 40S. && .LONG TERM... FRIDAY NIGHT THROUGH SATURDAY VERY ACTIVE PATTERN IN STORE FOR NEXT WEEK...AS SEVERAL STRONG MID LEVEL WAVES TAKE AIM AT THE REGION. WATER VAPOR AND VISIBLE SATELLITE CONFIRM NUMEROUS MID LEVEL WAVES OVER THE PACIFIC WITH THE SEMI-PERMANENT ALEUTIAN LOW CONTINUALLY AIDING IN PROPAGATION AND DEEPENING OF TRANSIENT WAVES TO THE SOUTH. PATTERN SHIFT IS EXPECTED AS THE SEEMINGLY ANCHORED UPPER LEVEL HIGH OVER GREENLAND WILL BREAK DOWN AND ALLOW A SHIFT IN TROUGHING TO THAT REGION. THIS FLOW SHIFT WILL PUSH THE HUDSON BAY VORTEX EAST ALLOWING EASTERN CONUS RIDGING AND EVENTUAL WEST COAST TROUGHING TO DEVELOP. THIS PATTERN SHIFT IS HIGHLIGHTED BY MEAN GFS ENSEMBLE PNA PROGS...WHICH CONTINUE TO SUPPORT A NEGATIVE PNA TENDENCY INTO THE LONG TERM PERIOD. THIS WILL SPELL AN ACTIVE PATTERN FOR THE REGION AS A SERIES OF MODERATE TO POTENT UPPER LEVEL WAVES WILL TRAVERSE THE GREAT LAKES IN MEAN SOUTHWEST FLOW...LENDING TO A PROPENSITY FOR RAIN AND THUNDERSTORMS. GIVEN THE AMPLIFIED NATURE OF THE FLOW NEXT WEEK...WOULD NOT RULE OUT A SEVERE WEATHER EVENT SOMEWHERE ACROSS THE MIDWEST...AS HEAT AND MOISTURE WILL BE SHIFTING NORTH. WITH A SHIFT TO EASTERN CONUS RIDGING WILL COME WARMER TEMPS AS HIGHS IN THE 60S WILL BE LIKELY WITH 70S POSSIBLE. OF COURSE FORECAST MODELS AND ENSEMBLES VARY GREATLY ON EVOLUTION OF THIS PATTERN SHIFT WITH NUMEROUS DISCREPANCIES IN SYSTEM STRENGTH/SPEED/TRACK AND QPF AS EXPECTED WITH THE HUGELY COMPLICATED FLOW REGIME IN PLACE OVER THE PACIFIC. THERE ARE A FEW CONSISTENT SIGNALS PRESENT IN THE MODEL SOLUTIONS WITH SOME AGREEMENT NOTED ON THE PASSAGE OF A SYSTEM SUN NIGHT AND THE EVENTUAL EJECTION OF THE DEEP WESTERN US TROUGH THU INTO FRIDAY. ALTHOUGH MODELS ARE STILL INCONSISTENT WITH HOW THIS TROUGH WILL EJECT...EITHER IN TWO STAGES WITH A PRIMARY DIGGING WAVE TUES-WED OR A WEAK PRIMARY WAVE AND STRONGER LONG WAVE TROUGH EJECTION ON THURS. SAT AND SUNDAY...BOTH WEEKEND DAYS LOOK EXCELLENT AS WEAK HIGH PRESSURE WILL DOMINATE THE WEATHER. TEMPS IN THE 50S/LOWER 60S LOOK GOOD ESPECIALLY AWAY FROM THE LAKE AS WEAK WAA WILL BE ONGOING THROUGH THE PERIOD PER INCREASING H85 TEMPS. HAVE ADJUSTED TEMPS NEAR LAKE MICHIGAN SATURDAY GIVEN WEAK FLOW AND FAIRLY STRONG DAYTIME HEATING. EXPECTING A LAKE GRAVITY CURRENT TO DEVELOP AND HOLD TEMPS IN THE 40S ALONG THE LAKE SHORE. SUN NIGHT INTO MONDAY...RETAINED PRECIP CHANCES WITH A NORTHERN STREAM WAVE STILL LOOKING GOOD ACROSS THE REGION. ALTHOUGH FORECAST MODELS HAVE BEEN TRENDING THIS SYSTEM FATHER NORTH. TUESDAY THROUGH THURSDAY...THE GFS AND ECMWF HAVE CONTINUED TO DISPLAY A RATHER POTENT SW TROUGH ADVECTING THROUGH THE FLOW TUES INTO WED. HAVE ADDED POPS TO TUESDAY WITH RAIN/THUNDER CHANCES POSSIBLE ALONG THE WARM FRONT AND AHEAD OF THE COLD FRONT IN THE AFTERNOON. THURSDAY STILL LOOKS QUITE INTERESTING AS THE WESTERN TROUGH IS STILL PROGGED TO EJECT INTO THE MIDWEST. MODELS AND ENSEMBLES HAVE BEEN INCONSISTENT WITH THE AMPLIFICATION AND TIMING OF THIS WAVE. HAVE HELD OFF FROM ANY MAJOR DEVIATIONS FROM CLIMO THROUGH THIS PERIOD...WITH ONLY A POSITIVE TREND TO TEMPS GIVEN PROGGED H85 TEMPS AND H5 HEIGHTS. THIS SYSTEM WILL HAVE TO BE MONITORED AS IT WILL BE A HIGH IMPACT SYSTEM FOR THE EASTERN CONUS. QUESTION WILL BE WHERE...GIVEN THE HIGH SHEAR AND INSTABILITY PRESENT. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...SCHOTT LONG TERM...CHAMBERLAIN UPDATE/AVIATION...HOLSTEN
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
418 PM EDT THU APR 3 2008 .SHORT TERM (TONIGHT THROUGH FRIDAY AFTERNOON)... SUNNY TO PARTLY SUNNY DAY WITH TEMPS NEARING NORMAL COMING TO A CLOSE AS CLOUDS WILL START TO INVADE THE FORECAST AREA LATE THIS AFTERNOON INTO THE EVENING AHEAD OF THE NEXT SYSTEM DEVELOPING ACROSS THE SOONER STATE. SLIGHT TIMING/POSITION DIFFERENCES BETWEEN THE MAJOR AMERICAN MODELS GFS/NAM12. 12Z RUNS SHOWS GFS SLIGHTLY FASTER (3-6HRS) THAN THE 12Z NAM12/09Z SREF/12Z UKMET AND 12Z NGM. WILL LEAN TOWARDS THE CONSENSUS AND THE 09Z SREF WHICH BLENDS OUT SOME OF THOSE SLIGHT TIMING AND STRENGTH DIFFERENCES BUT HOLDS CLOSER TO THE NAM GROUPING. SFC BOUNDARY NEAR THE OH RIVER...WITH DEWPOINTS IN THE 20S ACROSS THE REGION WITH DEWPTS IN THE UPPER 40S AND 50S SOUTH OF THE BOUNDARY. ACARS SOUNDINGS FROM THIS MORNING SHOW DEEP AND IMMENSE LAYER OF DRY AIR FROM AROUND 925 TO 700MB. SFC DEPRESSIONS ACROSS THE REGION ARE MORE THAN 20 TO 30 DEGREES AT MOST SITES...IT WILL TAKE SOME TIME FOR THE LOWER LEVELS TO MOISTEN AND HAVE HELD OFF ANY SIGNIFICANT CHCS FOR POPS UNTIL THIS EVENING...MOST LIKELY AFTER 02-04Z AS THE FIRST SFC WAVE MOVES EAST ALONG THE BOUNDARY TOWARDS THE OHIO VALLEY PULLING MOISTURE FROM THE GULF INTO THE REGION. MODEST ISENT LIFT IN THE 290-295K SFCS AFT 00Z...WITH STRONG CONVERGENCE SEEN IN THE H850 AND H700 LVLS ACROSS THE REGION THRU ABOUT 06-08Z. VERY STRONG UPPER LVL JET OF 130-140 KTS WITH THE AREA POSSIBLY IN THE PREFERRED RIGHT ENTRANCE THRU ABOUT 12-15Z. ONE FINAL INGREDIENT IS POSSIBLE CSI/SLANTWISE INSTABILITY OR WEAK ELEVATED CAPE SEEN THROUGH THE 03-08Z TIMEFRAME ACROSS THE REGION WHICH WILL ALLOW FOR CHC OF THUNDER. HAVE KEPT VERY HIGH CAT POPS...BUT HAVE THEM MAINLY IN THE 03-08Z TIMEFRAME WITH CHC POPS ELSEWHERE. AS THE SIGNIFICANT MOISTENING OF THE LOWER LEVELS OCCURS THE CIGS WILL DROP THRU THE NIGHT...WEAK LIFT WILL REMAIN WITH THE JET SUPPORT MENTIONED EARLIER AND THE WEAKENING DEFORMATION AREA MOVING THRU...-DZ AND LIGHT RAIN WILL BE POSSIBLE THRU THE MORNING.AS EVERYTHING STARTS TO PULL FURTHER EAST THE CLOUDS MAY START TO LIFT AND BREAK SLIGHTLY BY LATE AFTERNOON. TEMPS WILL DROP INTO THE UPPER 30S OR LOWER 40S OVERNIGHT...AND WITH THICK CLOUD COVER MOST OF THE DAY ALONG WITH POSSIBLE LIGHT RAIN OR DZ AND NORTHERLY WINDS...LITTLE DIURNAL BUMP WILL HAPPEN FRIDAY WITH AFTN HIGHS BELOW NORMAL IN THE MID AND MAYBE UPPER 40S. && .LONG TERM... FRIDAY NIGHT THROUGH SATURDAY VERY ACTIVE PATTERN IN STORE FOR NEXT WEEK...AS SEVERAL STRONG MID LEVEL WAVES TAKE AIM AT THE REGION. WATER VAPOR AND VISIBLE SATELLITE CONFIRM NUMEROUS MID LEVEL WAVES OVER THE PACIFIC WITH THE SEMI-PERMANENT ALEUTIAN LOW CONTINUALLY AIDING IN PROPAGATION AND DEEPENING OF TRANSIENT WAVES TO THE SOUTH. PATTERN SHIFT IS EXPECTED AS THE SEEMINGLY ANCHORED UPPER LEVEL HIGH OVER GREENLAND WILL BREAK DOWN AND ALLOW A SHIFT IN TROUGHING TO THAT REGION. THIS FLOW SHIFT WILL PUSH THE HUDSON BAY VORTEX EAST ALLOWING EASTERN CONUS RIDGING AND EVENTUAL WEST COAST TROUGHING TO DEVELOP. THIS PATTERN SHIFT IS HIGHLIGHTED BY MEAN GFS ENSEMBLE PNA PROGS...WHICH CONTINUE TO SUPPORT A NEGATIVE PNA TENDENCY INTO THE LONG TERM PERIOD. THIS WILL SPELL AN ACTIVE PATTERN FOR THE REGION AS A SERIES OF MODERATE TO POTENT UPPER LEVEL WAVES WILL TRAVERSE THE GREAT LAKES IN MEAN SOUTHWEST FLOW...LENDING TO A PROPENSITY FOR RAIN AND THUNDERSTORMS. GIVEN THE AMPLIFIED NATURE OF THE FLOW NEXT WEEK...WOULD NOT RULE OUT A SEVERE WEATHER EVENT SOMEWHERE ACROSS THE MIDWEST...AS HEAT AND MOISTURE WILL BE SHIFTING NORTH. WITH A SHIFT TO EASTERN CONUS RIDGING WILL COME WARMER TEMPS AS HIGHS IN THE 60S WILL BE LIKELY WITH 70S POSSIBLE. OF COURSE FORECAST MODELS AND ENSEMBLES VARY GREATLY ON EVOLUTION OF THIS PATTERN SHIFT WITH NUMEROUS DISCREPANCIES IN SYSTEM STRENGTH/SPEED/TRACK AND QPF AS EXPECTED WITH THE HUGELY COMPLICATED FLOW REGIME IN PLACE OVER THE PACIFIC. THERE ARE A FEW CONSISTENT SIGNALS PRESENT IN THE MODEL SOLUTIONS WITH SOME AGREEMENT NOTED ON THE PASSAGE OF A SYSTEM SUN NIGHT AND THE EVENTUAL EJECTION OF THE DEEP WESTERN US TROUGH THU INTO FRIDAY. ALTHOUGH MODELS ARE STILL INCONSISTENT WITH HOW THIS TROUGH WILL EJECT...EITHER IN TWO STAGES WITH A PRIMARY DIGGING WAVE TUES-WED OR A WEAK PRIMARY WAVE AND STRONGER LONG WAVE TROUGH EJECTION ON THURS. SAT AND SUNDAY...BOTH WEEKEND DAYS LOOK EXCELLENT AS WEAK HIGH PRESSURE WILL DOMINATE THE WEATHER. TEMPS IN THE 50S/LOWER 60S LOOK GOOD ESPECIALLY AWAY FROM THE LAKE AS WEAK WAA WILL BE ONGOING THROUGH THE PERIOD PER INCREASING H85 TEMPS. HAVE ADJUSTED TEMPS NEAR LAKE MICHIGAN SATURDAY GIVEN WEAK FLOW AND FAIRLY STRONG DAYTIME HEATING. EXPECTING A LAKE GRAVITY CURRENT TO DEVELOP AND HOLD TEMPS IN THE 40S ALONG THE LAKE SHORE. SUN NIGHT INTO MONDAY...RETAINED PRECIP CHANCES WITH A NORTHERN STREAM WAVE STILL LOOKING GOOD ACROSS THE REGION. ALTHOUGH FORECAST MODELS HAVE BEEN TRENDING THIS SYSTEM FATHER NORTH. TUESDAY THROUGH THURSDAY...THE GFS AND ECMWF HAVE CONTINUED TO DISPLAY A RATHER POTENT SW TROUGH ADVECTING THROUGH THE FLOW TUES INTO WED. HAVE ADDED POPS TO TUESDAY WITH RAIN/THUNDER CHANCES POSSIBLE ALONG THE WARM FRONT AND AHEAD OF THE COLD FRONT IN THE AFTERNOON. THURSDAY STILL LOOKS QUITE INTERESTING AS THE WESTERN TROUGH IS STILL PROGGED TO EJECT INTO THE MIDWEST. MODELS AND ENSEMBLES HAVE BEEN INCONSISTENT WITH THE AMPLIFICATION AND TIMING OF THIS WAVE. HAVE HELD OFF FROM ANY MAJOR DEVIATIONS FROM CLIMO THROUGH THIS PERIOD...WITH ONLY A POSITIVE TREND TO TEMPS GIVEN PROGGED H85 TEMPS AND H5 HEIGHTS. THIS SYSTEM WILL HAVE TO BE MONITORED AS IT WILL BE A HIGH IMPACT SYSTEM FOR THE EASTERN CONUS. QUESTION WILL BE WHERE...GIVEN THE HIGH SHEAR AND INSTABILITY PRESENT. && .AVIATION (18Z TAFS)... VFR CONDITIONS WITH START TO DETERIORATE AFT 02-04Z AS LOWER VSBYS AND DEVELOPING LOW CIGS WILL OCCUR WITH -SHRA AND A FEW TSTMS MOVING INTO THE REGION. WINDS WILL BACK FROM THE SOUTHEAST TO THE EAST AROUND 23-00Z THIS EVENING...AND THEN TO THE NORTH BY DAYBREAK FRIDAY. AS THE PRECIP MOVES INTO THE REGION AFTER 02-04Z VSBYS AS LOW AS 3-5 SM WILL BE LIKELY WITH CIGS NEARING 1K FT...MORE SO ACROSS THE SOUTH BEFORE 08Z. HAVE ADDED CB TO BOTH TERMINAL SITES...FWA AND SBN...WITH TSRA MENTIONED AT FWA 03-06Z. AFTER 08-09Z CIGS WILL DROP WITH LOW LEVELS SATURATED TO AROUND 500 TO 800 FT AND SOME -DZ/-RA POSSIBLE ACROSS THE REGION. PRECIP MAY START TO END AND CLOUDS LIFT SLIGHTLY DURING THE AFTERNOON ON FRIDAY. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...SCHOTT LONG TERM...CHAMBERLAIN AVIATION...SCHOTT
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
1031 PM EDT THU APR 3 2008 .UPDATE... FOG POTENTIAL REMAINS THE ISSUE FOR THE OVERNIGHT HOURS...AND HAS BECOME MORE UNCERTAIN DUE TO CLOUD ISSUES AND DRY AIR OVER THE CWA. FIRST AREA OF CLOUDS...MOSTLY CIRROSTRATUS...STRETCHES FROM CENTRAL WI ACROSS THE EAST HALF OF UPPER MI INTO NORTHERN LOWER MI. THIS AREA OF CLOUDS IS BEING SUPPORTED BY RIGHT ENTRANCE REGION FORCING UNDER A 100 KT JET IN EASTERN ONTARIO. THE SECOND AREA OF CLOUDS IS ALTOCUMULUS OVER WESTERN UPPER MI...ASSOCIATED WITH A WEAK SHRTWV TROUGH. SATELLITE TRENDS SHOW THE CIRROSTRATUS MOVING MUCH QUICKER TO THE EAST THAN THE ALTOCUMULUS...BUT WITH BOTH CLOUD FEATURES AROUND...TEMPERATURES ARE SLOW TO DROP. THE RUC ONLY SHIFTS THE ALTOCUMULUS INTO THE CENTRAL U.P. BY 12Z. ALSO...TAMDAR SOUNDINGS FROM CMX AND SAW INDICATE A LOT OF DRY AIR BELOW THE CLOUD BASE...LIKELY DUE TO STRONG MIXING THAT OCCURRED DURING THE DAY (MIXING HEIGHTS WERE UP TO 750MB). THE COMBINATION OF THE DRIER AIR AND THESE CLOUDS SHOULD KEEP ANY RADIATION FOG DEVELOPMENT LOCALIZED...AND THEREFORE HAVE DECREASED THE COVERAGE TO PATCHY. ALSO...WITH A FEW MORE CLOUDS AROUND...RAISED LOW TEMPS SLIGHTLY. && .SYNOPSIS... DESPITE DEEP SNOWPACK OVER MUCH OF UPR MI...STRONG APRIL SUNSHINE AND STEADY SW WINDS HELPING TO WARM TEMPS TO AROUND 50 IN MANY AREAS THIS AFTN. WARM TEMPS AND SOME H9-H7 MOISTURE ALONG WITH CONVECTIVE TEMPS NEAR 50 ALLOWED WIDESPREAD CU TO DEVELOP OVR WEST HALF THIS AFTN. THERE IS A HINT OF A SHORTWAVE PASSING ACROSS NORTHERN LAKE SUPERIOR SO SOME LIFT WITH THE INSTABILITY COULD RESULT IN ISOLD RAIN SHOWERS OVER THE NORTH CENTRAL EARLY THIS EVENING. RADAR LOOP WITH SOME ENHANCED ECHOES POINTS TO THIS POTENTIAL. NEXT ITEM OF CONCERN IS COLD FRONT AND SOME LIGHT PCPN COMING ACROSS UPR MI FRI NIGHT. AFTER A PRETTY QUIET WEEKEND...LONGWAVE PATTERN TURNS MUCH MORE ACTIVE NEXT WEEK WITH AT LEAST THREE CHANCES FOR SIGNIFICANT PCPN EVENTS. && .SHORT TERM (TONIGHT AND FRIDAY)... MAIN CONCERN IS FOG POTENTIAL LATE TONIGHT. SFC RIDGE OVER AREA SLOWLY SLIDES TO THE EAST THROUGH FRIDAY. DO NOT EXPECT NOTHING MORE THAN ISOLD SHOWERS THROUGH 00Z TONIGHT. COVERAGE IS HELD DOWN DUE TO DRY AIR SEEN BLO H8 ON 18Z TAMDAR FM KSAW. LOSS OF DAYTIME HEATING ALLOWS THE CU TO FADE BY LATE EVENING. ALSO...CI OVER SOUTHERN AREAS WILL SINK AWAY FM THE CWA. LOWER NEAR SFC LAYER OF MOISTURE WILL BE ON THE INCREASE DUE TO MELTING SNOW. LIGHT WINDS...THE ADDED MOISTURE...AND TEMPS COOLING INTO THE 20S SHOULD ALLOW SOME FOG TO DEVELOP OVER CNTRL AND ERN CWA LATE TONIGHT. GFS REMAINS PERSISTENT ON GENERATING SOME LIGHT QPF OVR WESTERN CWA AFT 18Z. GFS BUFKIT SOUNDINGS INDICATED SBCAPES NEAR 150J/KG AT 18Z TOMORROW...BUT IT ALSO SHOWS A SFC TD NEAR 40 WHICH SEEMS TOO HIGH. MODIFYING A SOUNDING FOR T/TD OF 47/30 GIVES CAPES BLO 50J/KG WHICH SEEMS MORE REASONABLE. NO OTHER GUIDANCE DEPICTS ANY QPF...BUT NO OTHER GUIDANCE DEPICTED QPF TODAY EITHER. RIGHT NOW THOUGH THINKING THERE WILL JUST BE A BUILD UP OF CU WITH NO PCPN. ANOTHER REASON FOR DRY FCST ON FRIDAY IS FACT THAT ONLY PCPN TIED TO FRONT RIGHT NOW IS OCCURRING ON COLD SIDE OF THE BOUNDARY. SINCE FRONT DOES NOT ARRIVE OVR CWA UNTIL FRI NIGHT RESTRICTED SMALL CHANCES FOR RAIN TO JUST WESTERN LAKE SUPERIOR FRIDAY AFTN. H9-H85 TEMPS SLIGHTLY WARMER THAN TODAY AND CLOUDS NOT INCREASING UNTIL LATE DAY SUGGEST MAX TEMPS AWAY FM LAKE MICHIGAN WILL BE NEAR 50 AGAIN. .LONG TERM (FRI NIGHT THROUGH NEXT THU)... FIRST ITEM OF CONCERN IS THE COLD FRONT FOR FRI NIGHT. NAM SHOWING IT COMING THROUGH THEN BASED ON 1000-500 MB THICKNESS PACKING. THERE IS ALSO SOME 850-500 MB Q-VECTOR CONVERGENCE FOR FRI NIGHT WITH THE COLD FRONT ALONG WITH SOME MOISTURE TO WORK WITH WHICH IS A NARROW RIBBON ACCORDING TO THE NAM. WILL CONTINUE WITH SLIGHT CHANCE TO LOW CHANCE POPS AS THE COLD FRONT COMES THROUGH. NAM SHOWS 850-500 MB Q-VECTOR CONVERGENCE RETURNING SAT NIGHT AND SUN...BUT MOISTURE STAYING TO THE NORTH AND WEST. ECMWF HAS IT DRY...WHILE CANADIAN HAS QPF COMING IN LATE SAT NIGHT. GFS APPEARS TOO FAST AND IS AN OUTLIER AND DID NOT USE. USED THE ECMWF FOR THIS FORECAST AS IT HAS SOME CONTINUITY TO IT WITH SOME HELP FROM THE CANADIAN GLBL GEM. WENT WITH SLIGHT CHANCE POPS ACROSS THE WEST LATE SAT NIGHT AND THEN CHANCE POPS ON SUNDAY. SUNDAY COULD BE WET AND WENT WITH HIGH CHANCE POPS FOR NOW. AS EVENT DRAWS CLOSER...POPS CAN BE INCREASED. TEMPERATURES LOOK TO BE WARM ENOUGH FOR RAIN ON SUNDAY RIGHT NOW WITH RAIN/SNOW FOR SUN NIGHT. DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST FOR TEMPERATURES. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL SHOW A NEGATIVELY TILTED 500 MB TROUGH AFFECTING THE AREA 00Z MON. THIS TROUGH THEN CONTINUES TO AFFECT THE AREA THROUGH MON. ANOTHER TROUGH COMES IN FOR 00Z WED AND ALSO BECOMES NEGATIVELY TILTED WITH MORE TROUGHING FOR THU. LOOKS TO BE FAIRLY ACTIVE THIS NEXT WEEK. ONE CONCERN IS WITH STORMS FOR SUN INTO MON...TUE NIGHT INTO WED AND THEN FOR FRI. THE TUE NIGHT AND FRI SYSTEMS HAVE AN OPEN GULF OF MEXICO SOURCE AND SIGNIFICANT DEEP MOISTURE COULD MAKE IT UP HERE. CONCERN IS THAT WITH SNOWPACK ON GROUND COMBINED WITH UP TO 4 INCHES OF ADDITIONAL PCPN POSSIBLE NEXT WEEK WHICH IS WITHIN THE REALM OF POSSIBILITIES...THE SNOWPACK/SNOWMELT COULD BECOME A HYDROLOGY PROBLEM ESPECIALLY IF A BIG WARMUP OCCURS AFTER NEXT WEEK. NO BIG WARMUPS LOOK POSSIBLE FOR NOW. ONLY THING WOULD BE PRIMING THE SNOWPACK/SNOWMELT WITH NEXT WEEKS SYSTEMS. WILL PASS ON TO LATER SHIFTS OF THIS POSSIBILITY AND MENTION IN ESF PRODUCT. TEMPERATURES LOOK TO BE NEAR NORMAL AND DID NOT MAKE TOO MANY CHANGES TO THE GOING TEMPERATURES. PCPN TYPES WILL BE TRICKY...BUT TOO FAR OUT YET TO WORRY ABOUT. WENT RAIN/SNOW MOSTLY FOR THIS EXTENDED FORECAST. WENT CLOSE TO ADJMOS TEMPERATURES. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... MAIN ISSUE REMAINS THE POTENTIAL FOR FOG FORMATION LATE TONIGHT... WHICH HAS BECOME MORE UNCERTAIN WITH THIS ISSUANCE. HIGH BASED CUMULUS CLOUDS DEVELOPED LATE THIS AFTN AHEAD OF A WEAK TROUGH CROSSING LAKE SUPERIOR AND MN. THESE CLOUDS OVER THE PAST TWO HOURS DO NOT APPEAR TO BE DISSIPATING MUCH...MEANING THAT THEY MAY NOT BE DIRECTLY RELATED TO DAYTIME HEATING. IF THAT IS INDEED THE CASE AND SINCE MODELS ARE VERY SLOW TO PROGRESS THESE CLOUDS EASTWARD...THE DEVELOPMENT OF RADIATION FOG WILL BE DIFFICULT. IN ADDITION...TAMDAR SOUNDING FROM CMX AT 21Z ALONG WITH SURFACE OBSERVATIONS DEPICT A LOT OF DRY AIR BELOW THE CLOUD BASE...ALSO UNFAVORABLE FOR RADIATION FOG FORMATION. FOR NOW HAVE TRENDED UPWARD AT BOTH SITES FOR VSBY AND CIG...AND FURTHER IMPROVEMENT MAY BE NECESSARY UPON THE NEXT TAF ISSUANCE IF THE CLOUDS DO INDEED HOLD TOGETHER. OTHERWISE...VFR CONDITIONS ARE EXPECTED THROUGH FRI...WITH A BKN HIGH STRATUS DECK MOVING IN LATE FRI ASSOCIATED WITH A COLD FRONT DROPPING SOUTH FROM NW ONTARIO. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... POTENTIAL FOR WINDS ABOVE 25 KNOTS FRIDAY NIGHT AHEAD OF COLD FRONT AND ALSO ON SATURDAY MORNING IN WAKE OF THE FRONT. A COUPLE OF LOW PRESSURE SYSTEMS LIFTING INTO THE UPPER GREAT LAKES FM THE SOUTHWEST MAY RESULT IN WINDS TO 30 KNOTS SUNDAY INTO TUESDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...AJ SHORT TERM...JLA LONG TERM...GJM AVIATION...AJ MARINE...JLA
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
742 PM EDT THU APR 3 2008 UPDATED AVIATION DISCUSSION FOR 00Z TAF ISSUANCE .SYNOPSIS... DESPITE DEEP SNOWPACK OVER MUCH OF UPR MI...STRONG APRIL SUNSHINE AND STEADY SW WINDS HELPING TO WARM TEMPS TO AROUND 50 IN MANY AREAS THIS AFTN. WARM TEMPS AND SOME H9-H7 MOISTURE ALONG WITH CONVECTIVE TEMPS NEAR 50 ALLOWED WIDESPREAD CU TO DEVELOP OVR WEST HALF THIS AFTN. THERE IS A HINT OF A SHORTWAVE PASSING ACROSS NORTHERN LAKE SUPERIOR SO SOME LIFT WITH THE INSTABILITY COULD RESULT IN ISOLD RAIN SHOWERS OVER THE NORTH CENTRAL EARLY THIS EVENING. RADAR LOOP WITH SOME ENHANCED ECHOES POINTS TO THIS POTENTIAL. NEXT ITEM OF CONCERN IS COLD FRONT AND SOME LIGHT PCPN COMING ACROSS UPR MI FRI NIGHT. AFTER A PRETTY QUIET WEEKEND...LONGWAVE PATTERN TURNS MUCH MORE ACTIVE NEXT WEEK WITH AT LEAST THREE CHANCES FOR SIGNIFICANT PCPN EVENTS. && .SHORT TERM (TONIGHT AND FRIDAY)... MAIN CONCERN IS FOG POTENTIAL LATE TONIGHT. SFC RIDGE OVER AREA SLOWLY SLIDES TO THE EAST THROUGH FRIDAY. DO NOT EXPECT NOTHING MORE THAN ISOLD SHOWERS THROUGH 00Z TONIGHT. COVERAGE IS HELD DOWN DUE TO DRY AIR SEEN BLO H8 ON 18Z TAMDAR FM KSAW. LOSS OF DAYTIME HEATING ALLOWS THE CU TO FADE BY LATE EVENING. ALSO...CI OVER SOUTHERN AREAS WILL SINK AWAY FM THE CWA. LOWER NEAR SFC LAYER OF MOISTURE WILL BE ON THE INCREASE DUE TO MELTING SNOW. LIGHT WINDS...THE ADDED MOISTURE...AND TEMPS COOLING INTO THE 20S SHOULD ALLOW SOME FOG TO DEVELOP OVER CNTRL AND ERN CWA LATE TONIGHT. GFS REMAINS PERSISTENT ON GENERATING SOME LIGHT QPF OVR WESTERN CWA AFT 18Z. GFS BUFKIT SOUNDINGS INDICATED SBCAPES NEAR 150J/KG AT 18Z TOMORROW...BUT IT ALSO SHOWS A SFC TD NEAR 40 WHICH SEEMS TOO HIGH. MODIFYING A SOUNDING FOR T/TD OF 47/30 GIVES CAPES BLO 50J/KG WHICH SEEMS MORE REASONABLE. NO OTHER GUIDANCE DEPICTS ANY QPF...BUT NO OTHER GUIDANCE DEPICTED QPF TODAY EITHER. RIGHT NOW THOUGH THINKING THERE WILL JUST BE A BUILD UP OF CU WITH NO PCPN. ANOTHER REASON FOR DRY FCST ON FRIDAY IS FACT THAT ONLY PCPN TIED TO FRONT RIGHT NOW IS OCCURRING ON COLD SIDE OF THE BOUNDARY. SINCE FRONT DOES NOT ARRIVE OVR CWA UNTIL FRI NIGHT RESTRICTED SMALL CHANCES FOR RAIN TO JUST WESTERN LAKE SUPERIOR FRIDAY AFTN. H9-H85 TEMPS SLIGHTLY WARMER THAN TODAY AND CLOUDS NOT INCREASING UNTIL LATE DAY SUGGEST MAX TEMPS AWAY FM LAKE MICHIGAN WILL BE NEAR 50 AGAIN. .LONG TERM (FRI NIGHT THROUGH NEXT THU)... FIRST ITEM OF CONCERN IS THE COLD FRONT FOR FRI NIGHT. NAM SHOWING IT COMING THROUGH THEN BASED ON 1000-500 MB THICKNESS PACKING. THERE IS ALSO SOME 850-500 MB Q-VECTOR CONVERGENCE FOR FRI NIGHT WITH THE COLD FRONT ALONG WITH SOME MOISTURE TO WORK WITH WHICH IS A NARROW RIBBON ACCORDING TO THE NAM. WILL CONTINUE WITH SLIGHT CHANCE TO LOW CHANCE POPS AS THE COLD FRONT COMES THROUGH. NAM SHOWS 850-500 MB Q-VECTOR CONVERGENCE RETURNING SAT NIGHT AND SUN...BUT MOISTURE STAYING TO THE NORTH AND WEST. ECMWF HAS IT DRY...WHILE CANADIAN HAS QPF COMING IN LATE SAT NIGHT. GFS APPEARS TOO FAST AND IS AN OUTLIER AND DID NOT USE. USED THE ECMWF FOR THIS FORECAST AS IT HAS SOME CONTINUITY TO IT WITH SOME HELP FROM THE CANADIAN GLBL GEM. WENT WITH SLIGHT CHANCE POPS ACROSS THE WEST LATE SAT NIGHT AND THEN CHANCE POPS ON SUNDAY. SUNDAY COULD BE WET AND WENT WITH HIGH CHANCE POPS FOR NOW. AS EVENT DRAWS CLOSER...POPS CAN BE INCREASED. TEMPERATURES LOOK TO BE WARM ENOUGH FOR RAIN ON SUNDAY RIGHT NOW WITH RAIN/SNOW FOR SUN NIGHT. DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST FOR TEMPERATURES. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL SHOW A NEGATIVELY TILTED 500 MB TROUGH AFFECTING THE AREA 00Z MON. THIS TROUGH THEN CONTINUES TO AFFECT THE AREA THROUGH MON. ANOTHER TROUGH COMES IN FOR 00Z WED AND ALSO BECOMES NEGATIVELY TILTED WITH MORE TROUGHING FOR THU. LOOKS TO BE FAIRLY ACTIVE THIS NEXT WEEK. ONE CONCERN IS WITH STORMS FOR SUN INTO MON...TUE NIGHT INTO WED AND THEN FOR FRI. THE TUE NIGHT AND FRI SYSTEMS HAVE AN OPEN GULF OF MEXICO SOURCE AND SIGNIFICANT DEEP MOISTURE COULD MAKE IT UP HERE. CONCERN IS THAT WITH SNOWPACK ON GROUND COMBINED WITH UP TO 4 INCHES OF ADDITIONAL PCPN POSSIBLE NEXT WEEK WHICH IS WITHIN THE REALM OF POSSIBILITIES...THE SNOWPACK/SNOWMELT COULD BECOME A HYDROLOGY PROBLEM ESPECIALLY IF A BIG WARMUP OCCURS AFTER NEXT WEEK. NO BIG WARMUPS LOOK POSSIBLE FOR NOW. ONLY THING WOULD BE PRIMING THE SNOWPACK/SNOWMELT WITH NEXT WEEKS SYSTEMS. WILL PASS ON TO LATER SHIFTS OF THIS POSSIBILITY AND MENTION IN ESF PRODUCT. TEMPERATURES LOOK TO BE NEAR NORMAL AND DID NOT MAKE TOO MANY CHANGES TO THE GOING TEMPERATURES. PCPN TYPES WILL BE TRICKY...BUT TOO FAR OUT YET TO WORRY ABOUT. WENT RAIN/SNOW MOSTLY FOR THIS EXTENDED FORECAST. WENT CLOSE TO ADJMOS TEMPERATURES. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... MAIN ISSUE REMAINS THE POTENTIAL FOR FOG FORMATION LATE TONIGHT... WHICH HAS BECOME MORE UNCERTAIN WITH THIS ISSUANCE. HIGH BASED CUMULUS CLOUDS DEVELOPED LATE THIS AFTN AHEAD OF A WEAK TROUGH CROSSING LAKE SUPERIOR AND MN. THESE CLOUDS OVER THE PAST TWO HOURS DO NOT APPEAR TO BE DISSIPATING MUCH...MEANING THAT THEY MAY NOT BE DIRECTLY RELATED TO DAYTIME HEATING. IF THAT IS INDEED THE CASE AND SINCE MODELS ARE VERY SLOW TO PROGRESS THESE CLOUDS EASTWARD...THE DEVELOPMENT OF RADIATION FOG WILL BE DIFFICULT. IN ADDITION...TAMDAR SOUNDING FROM CMX AT 21Z ALONG WITH SURFACE OBSERVATIONS DEPICT A LOT OF DRY AIR BELOW THE CLOUD BASE...ALSO UNFAVORABLE FOR RADIATION FOG FORMATION. FOR NOW HAVE TRENDED UPWARD AT BOTH SITES FOR VSBY AND CIG...AND FURTHER IMPROVEMENT MAY BE NECESSARY UPON THE NEXT TAF ISSUANCE IF THE CLOUDS DO INDEED HOLD TOGETHER. OTHERWISE...VFR CONDITIONS ARE EXPECTED THROUGH FRI...WITH A BKN HIGH STRATUS DECK MOVING IN LATE FRI ASSOCIATED WITH A COLD FRONT DROPPING SOUTH FROM NW ONTARIO. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... POTENTIAL FOR WINDS ABOVE 25 KNOTS FRIDAY NIGHT AHEAD OF COLD FRONT AND ALSO ON SATURDAY MORNING IN WAKE OF THE FRONT. A COUPLE OF LOW PRESSURE SYSTEMS LIFTING INTO THE UPPER GREAT LAKES FM THE SOUTHWEST MAY RESULT IN WINDS TO 30 KNOTS SUNDAY INTO TUESDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...JLA LONG TERM...GJM AVIATION...AJ MARINE...JLA
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
423 PM EDT THU APR 3 2008 .SYNOPSIS... DESPITE DEEP SNOWPACK OVER MUCH OF UPR MI...STRONG APRIL SUNSHINE AND STEADY SW WINDS HELPING TO WARM TEMPS TO AROUND 50 IN MANY AREAS THIS AFTN. WARM TEMPS AND SOME H9-H7 MOISTURE ALONG WITH CONVECTIVE TEMPS NEAR 50 ALLOWED WIDESPREAD CU TO DEVELOP OVR WEST HALF THIS AFTN. THERE IS A HINT OF A SHORTWAVE PASSING ACROSS NORTHERN LAKE SUPERIOR SO SOME LIFT WITH THE INSTABILITY COULD RESULT IN ISOLD RAIN SHOWERS OVER THE NORTH CENTRAL EARLY THIS EVENING. RADAR LOOP WITH SOME ENHANCED ECHOES POINTS TO THIS POTENTIAL. NEXT ITEM OF CONCERN IS COLD FRONT AND SOME LIGHT PCPN COMING ACROSS UPR MI FRI NIGHT. AFTER A PRETTY QUIET WEEKEND...LONGWAVE PATTERN TURNS MUCH MORE ACTIVE NEXT WEEK WITH AT LEAST THREE CHANCES FOR SIGNIFICANT PCPN EVENTS. && .SHORT TERM (TONIGHT AND FRIDAY)... MAIN CONCERN IS FOG POTENTIAL LATE TONIGHT. SFC RIDGE OVER AREA SLOWLY SLIDES TO THE EAST THROUGH FRIDAY. DO NOT EXPECT NOTHING MORE THAN ISOLD SHOWERS THROUGH 00Z TONIGHT. COVERAGE IS HELD DOWN DUE TO DRY AIR SEEN BLO H8 ON 18Z TAMDAR FM KSAW. LOSS OF DAYTIME HEATING ALLOWS THE CU TO FADE BY LATE EVENING. ALSO...CI OVER SOUTHERN AREAS WILL SINK AWAY FM THE CWA. LOWER NEAR SFC LAYER OF MOISTURE WILL BE ON THE INCREASE DUE TO MELTING SNOW. LIGHT WINDS...THE ADDED MOISTURE...AND TEMPS COOLING INTO THE 20S SHOULD ALLOW SOME FOG TO DEVELOP OVER CNTRL AND ERN CWA LATE TONIGHT. GFS REMAINS PERSISTENT ON GENERATING SOME LIGHT QPF OVR WESTERN CWA AFT 18Z. GFS BUFKIT SOUNDINGS INDICATED SBCAPES NEAR 150J/KG AT 18Z TOMORROW...BUT IT ALSO SHOWS A SFC TD NEAR 40 WHICH SEEMS TOO HIGH. MODIFYING A SOUNDING FOR T/TD OF 47/30 GIVES CAPES BLO 50J/KG WHICH SEEMS MORE REASONABLE. NO OTHER GUIDANCE DEPICTS ANY QPF...BUT NO OTHER GUIDANCE DEPICTED QPF TODAY EITHER. RIGHT NOW THOUGH THINKING THERE WILL JUST BE A BUILD UP OF CU WITH NO PCPN. ANOTHER REASON FOR DRY FCST ON FRIDAY IS FACT THAT ONLY PCPN TIED TO FRONT RIGHT NOW IS OCCURRING ON COLD SIDE OF THE BOUNDARY. SINCE FRONT DOES NOT ARRIVE OVR CWA UNTIL FRI NIGHT RESTRICTED SMALL CHANCES FOR RAIN TO JUST WESTERN LAKE SUPERIOR FRIDAY AFTN. H9-H85 TEMPS SLIGHTLY WARMER THAN TODAY AND CLOUDS NOT INCREASING UNTIL LATE DAY SUGGEST MAX TEMPS AWAY FM LAKE MICHIGAN WILL BE NEAR 50 AGAIN. LONG TERM...00Z SAT ONWARD FIRST ITEM OF CONCERN IS THE COLD FRONT FOR FRI NIGHT. NAM SHOWING IT COMING THROUGH THEN BASED ON 1000-500 MB THICKNESS PACKING. THERE IS ALSO SOME 850-500 MB Q-VECTOR CONVERGENCE FOR FRI NIGHT WITH THE COLD FRONT ALONG WITH SOME MOISTURE TO WORK WITH WHICH IS A NARROW RIBBON ACCORDING TO THE NAM. WILL CONTINUE WITH SLIGHT CHANCE TO LOW CHANCE POPS AS THE COLD FRONT COMES THROUGH. NAM SHOWS 850-500 MB Q-VECTOR CONVERGENCE RETURNING SAT NIGHT AND SUN...BUT MOISTURE STAYING TO THE NORTH AND WEST. ECMWF HAS IT DRY...WHILE CANADIAN HAS QPF COMING IN LATE SAT NIGHT. GFS APPEARS TOO FAST AND IS AN OUTLIER AND DID NOT USE. USED THE ECMWF FOR THIS FORECAST AS IT HAS SOME CONTINUITY TO IT WITH SOME HELP FROM THE CANADIAN GLBL GEM. WENT WITH SLIGHT CHANCE POPS ACROSS THE WEST LATE SAT NIGHT AND THEN CHANCE POPS ON SUNDAY. SUNDAY COULD BE WET AND WENT WITH HIGH CHANCE POPS FOR NOW. AS EVENT DRAWS CLOSER...POPS CAN BE INCREASED. TEMPERATURES LOOK TO BE WARM ENOUGH FOR RAIN ON SUNDAY RIGHT NOW WITH RAIN/SNOW FOR SUN NIGHT. DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST FOR TEMPERATURES. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL SHOW A NEGATIVELY TILTED 500 MB TROUGH AFFECTING THE AREA 00Z MON. THIS TROUGH THEN CONTINUES TO AFFECT THE AREA THROUGH MON. ANOTHER TROUGH COMES IN FOR 00Z WED AND ALSO BECOMES NEGATIVELY TILTED WITH MORE TROUGHING FOR THU. LOOKS TO BE FAIRLY ACTIVE THIS NEXT WEEK. ONE CONCERN IS WITH STORMS FOR SUN INTO MON...TUE NIGHT INTO WED AND THEN FOR FRI. THE TUE NIGHT AND FRI SYSTEMS HAVE AN OPEN GULF OF MEXICO SOURCE AND SIGNIFICANT DEEP MOISTURE COULD MAKE IT UP HERE. CONCERN IS THAT WITH SNOWPACK ON GROUND COMBINED WITH UP TO 4 INCHES OF ADDITIONAL PCPN POSSIBLE NEXT WEEK WHICH IS WITHIN THE REALM OF POSSIBILITIES...THE SNOWPACK/SNOWMELT COULD BECOME A HYDROLOGY PROBLEM ESPECIALLY IF A BIG WARMUP OCCURS AFTER NEXT WEEK. NO BIG WARMUPS LOOK POSSIBLE FOR NOW. ONLY THING WOULD BE PRIMING THE SNOWPACK/SNOWMELT WITH NEXT WEEKS SYSTEMS. WILL PASS ON TO LATER SHIFTS OF THIS POSSIBILITY AND MENTION IN ESF PRODUCT. TEMPERATURES LOOK TO BE NEAR NORMAL AND DID NOT MAKE TOO MANY CHANGES TO THE GOING TEMPERATURES. PCPN TYPES WILL BE TRICKY...BUT TOO FAR OUT YET TO WORRY ABOUT. WENT RAIN/SNOW MOSTLY FOR THIS EXTENDED FORECAST. WENT CLOSE TO ADJMOS TEMPERATURES. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... HIGH PRESSURE RIDGE OVERHEAD LEADS TO VFR CONDITIONS THROUGH THIS EVENING. WARM TEMPERATURES AND MELTING SNOW SHOULD LEAD TO ADDED MOISTURE IN LOWEST 1-2KFT. AS TEMPS FALL...EXPECT THIS MOISTURE TO AID IN FOG DEVELOPMENT LATE TONIGHT INTO EARLY FRIDAY. FOG SHOULD BE SHALLOW BUT COULD REDUCE VSBY AND/OR CIGS TO LIFR. BEST CHANCE FOR DENSE FOG WOULD BE AT KSAW. BY MID MORNING FRIDAY...EXPECT VFR CONDITIONS. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... POTENTIAL FOR WINDS ABOVE 25 KNOTS FRIDAY NIGHT AHEAD OF COLD FRONT AND ALSO ON SATURDAY MORNING IN WAKE OF THE FRONT. A COUPLE OF LOW PRESSURE SYSTEMS LIFTING INTO THE UPPER GREAT LAKES FM THE SOUTHWEST MAY RESULT IN WINDS TO 30 KNOTS SUNDAY INTO TUESDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ SHORT TERM...JLA LONG TERM...GJM AVIATION...JLA MARINE...JLA
AREA FORECAST DISCUSSION
NWS DETROIT/PONTIAC MI
1253 AM EDT WED APR 2 2008 .AVIATION... WITH THE BULK OF THE CLOUDS SOON TO BE EAST OF THE AREA...VFR CONDITIONS WILL PREVAIL AT THE TAF SITES THROUGH THE PERIOD AS HIGH PRESSURE DRIFTS ACROSS THE SOUTHERN GREAT LAKES REGION. WINDS WILL CONTINUE TO DIMINISH...BECOMING LIGHT BY 10Z. && .PREV DISCUSSION...ISSUED 305 PM EDT TUE APR 1 2008 SHORT TERM...TONIGHT AN ACARS FLIGHT OUT OF DTW SHOWED A WELL MIXED BOUNDARY LAYER (AROUND 825 MB) THIS AFTERNOON...WHICH HAS ALLOWED WINDS TO CONTINUE TO GUST IN THE 35 TO 45 MPH RANGE...ALTHOUGH ISOLATED 50 MPH WIND GUSTS ARE STILL OCCURRING (49 MPH AT PTK WITHIN THE LAST HOUR). WILL THUS BE MAINTAINING THE WIND ADVISORY UNTIL 5 PM. THE PRESSURE GRADIENT WILL SLOWLY BE DIMINISHING LATE THIS AFTERNOON WITH THE CONTINUED COOLING AND SHRINKING OF THE BOUNDARY LAYER DEPTH AS THE SUN BEGINS TO SET. LARGE AREA OF HIGH PRESSURE BUILDING INTO SOUTHERN LOWER MICHIGAN TONIGHT SHOULD ALLOW SKIES TO CLEAR (CLEARING LINE NOTED UPSTREAM PUSHING INTO LAKE MICHIGAN)...WITH WINDS DIMINISHING OVERNIGHT. ALTHOUGH...WITH WINDS STAYING UP THROUGH MUCH OF THE NIGHT...EXPECTING MINS TO HOLD IN THE LOW TO MID 20S...OTHERWISE WE COULD SNEAK INTO THE UPPER TEENS WITH THE NORMAL DIURNAL SWING (AROUND 20 DEGREES) OFF THE CURRENT READINGS. LONG TERM...WEDNESDAY THROUGH MONDAY. HIGH PRESSURE FIRMLY IN CONTROL ON WEDNESDAY. DRY AIRMASS AND GENERAL SUBSIDENCE WILL PROVIDE FULL SUNSHINE...AND ALLOW THE AIRMASS TO BEGIN MODIFYING. STILL A RELATIVELY COOL AIRMASS TO WORK WITH BASED ON PROJECTED 850MB TEMPS LESS THAN -5C...SO EXPECT HIGHS TO REMAIN BELOW NORMAL IN THE MID/UPPER 40S DESPITE GOOD SOLAR HEATING. MODELS COMING IN TO BETTER AGREEMENT IN RESOLVING A PROGRESSIVE SPLIT UPPER LEVEL FLOW FOR THE END OF THE WEEK. ALTHOUGH THERE REMAINS SOME SUBTLE DIFFERENCES...A GFS/ECMWF/CANADIAN CONSENSUS NOW PHASES TWO SEPARATE SYSTEMS EMBEDDED WITHIN THE FLOW OVER THE SOUTHERN PLAINS/ROCKIES. SFC CYCLOGENESIS WILL DEVELOP THURSDAY IN RESPONSE TO THE RAPID HEIGHT FALLS...LIFTING NORTHEAST THROUGH THE SOUTHERN OHIO VALLEY BY EARLY FRIDAY. INITIAL PERIOD OF ISENTROPIC ACCENT NOT OVERLY IMPRESSIVE...BUT STILL SUFFICIENT TO EVENTUALLY OVERCOME THE DRIER LOWER LAYERS AND BRING LGT PRECIP TO THE SOUTHERN HALF LATE THURSDAY. WILL MAINTAIN LIKELY POPS FROM I-69 SOUTHWARD THURSDAY NIGHT/EARLY FRIDAY...AS THE LARGE SCALE ACCENT/DIVERGENCE INCREASES WITHIN THE RIGHT ENTRANCE REGION OF A 130+ KT JET AND ALONG THE MAIN DEFORMATION AXIS. GFS SLIGHTLY MORE ROBUST NOW WITH THE QPF ON FRIDAY ACROSS THE NORTHERN HALF...PERHAPS CONTRIBUTED TO A HINT OF CONVECTIVE INSTABILITY...AND WILL MONITOR THIS NORTHWARD TREND IN THE MOISTURE FIELDS. SOUNDINGS STILL SUGGEST ALL RAIN... ALTHOUGH THE POTENTIAL APPEARS THERE FOR SNOW TO MIX IN FRIDAY (MAINLY NORTH) AS COLDER AIR DRAINS BACK IN BEHIND THE DEPARTING SFC LOW. UPPER LEVEL PATTERN FOR THE WEEKEND AND BEYOND WILL EVOLVE INTO BROAD TROUGHING ACROSS MUCH OF THE CONUS. SEVERAL SHORTWAVES EMBEDDED WITHIN THIS FLOW WILL DICTATE CONDITIONS LOCALLY THROUGH THIS TIME. FIRST IMPULSE WILL SHEAR ACROSS THE US/CANADIAN BORDER FRIDAY/FRI NGT...DRAGGING A WEAK COLD FRONT INTO THE CENTRAL GREAT LAKES ON SATURDAY. AVAILABLE MOISTURE AND DEEP FORCING WILL BE LACKING...BUT LOW LEVEL CONVERGENCE ALONG THE BOUNDARY WILL BE SUFFICIENT TO WARRANT A LOW POP FOR SATURDAY AFTERNOON/EVENING. PARTIAL INSOLATION AT LEAST EARLY IN THE DAY WILL HELP MODIFY THE AIRMASS...WITH AFTERNOON HIGHS CREEPING UP TO NEAR OR JUST BELOW NORMAL (UPPER 40S NORTH/LOWER 50S SOUTH). FRONTAL BOUNDARY QUICKLY LIFTS BACK NORTH INTO THE UPPER PENINSULA ON SUNDAY AS THE NEXT SHORTWAVE AND ASSOCIATED SFC LOW EJECT INTO THE PLAINS. WILL DROP POPS SUNDAY FROM FLINT SOUTH...AND MAY NEED TO EVENTUALLY PULL THEM OVER ALL LOCALES DEPENDING ON WHERE THE BOUNDARY SETS UP...WITH NO OTHER FORCING MECHANISM IN PLAY WITHIN THE MODERATING WARM SECTOR. THE DRY CONDITIONS...WARM AIR ADVECTION AND PARTIAL INSOLATION WILL ALLOW TEMPERATURES TO CLIMB INTO THE 50S ON SUNDAY. MARINE... WIND GUSTS TO AROUND 40 KNOT GALES HAVE OCCURRED ACROSS ALL MARINE WATERS THIS AFTERNOON. STRONG LOW PRESSURE OVER SOUTHERN QUEBEC WILL CONTINUE TO TRACK NORTHEAST...WITH HIGH PRESSURE BUILDING INTO SOUTHERN LOWER MICHIGAN TONIGHT. THIS WILL ALLOW WINDS TO SLOWLY DIMINISH THROUGH TONIGHT. THIS HIGH IS EXPECTED TO STAY IN CONTROL THROUGH THURSDAY BEFORE THE NEXT LOW PRESSURE SYSTEM ARRIVES ON FRIDAY. WINDS ARE EXPECTED TO REMAIN BELOW 25 KNOTS DURING THIS TIME. && .DTX WATCHES/WARNINGS/ADVISORIES... MI...NONE. LAKE HURON... GALE WARNING...LHZ361-LHZ362-LHZ363...UNTIL 5 AM WEDNESDAY. SMALL CRAFT ADVISORY...OUTER SAGINAW BAY...UNTIL 5 AM WEDNESDAY. SMALL CRAFT ADVISORY...NEARSHORE WATERS FROM PORT AUSTIN TO PORT HURON...UNTIL 11 AM WEDNESDAY. LAKE ST CLAIR... SMALL CRAFT ADVISORY...UNTIL 5 AM WEDNESDAY. MI WATERS OF LAKE ERIE... SMALL CRAFT ADVISORY...UNTIL 5 AM WEDNESDAY. && $$ AVIATION.....SC SHORT TERM...SF LONG TERM....MR MARINE.......SF YOU CAN OBTAIN YOUR LATEST NATIONAL WEATHER SERVICE FORECASTS ONLINE AT WWW.WEATHER.GOV/DETROIT (ALL LOWER CASE).
AREA FORECAST DISCUSSION...UPDATED
NWS DULUTH MN
859 PM CDT THU APR 3 2008 .UPDATE...UPDATED MIN TEMPS AS TEMPS ARE SLOW TO COOL. WITH COLD FRONT N OF THE INTERNATIONAL BORDER...AND EXPECTED SLOW MOVEMENT...WILL JUST SEE CLOUDS ON THE INCREASE...ESPECIALLY IN THE NORTHERN THIRD OF THE FA. MID CLOUDS IN NW WI DUE TO A VORT MAX MOVING THROUGH CENTRAL MN ATTM. TAMDAR SOUNDINGS FROM NW WI INDICATE A VERY DRY ATMOSPHERE IN PLACE...SO NO PCPN. THESE CLOUDS ALSO HELPING KEEP TEMPS UP IN NW WI. && .PREV DISCUSSION... /ISSUED 240 PM CDT THU APR 3 2008/ DISCUSSION...SHORT TERM FOCUS FOR FORECAST IS CLOUDS AND PRECIP FRIDAY AND FRIDAY NIGHT. MAIN FOCUS FOR FORECAST PERIOD IS MAJOR WEATHER SYSTEM OCCURRING SAT NIGHT THROUGH SUN NIGHT. SHORT TERM...CURRENT SURFACE ANALYSIS INDICATE MAINLY SUNNY SKIES ACROSS THE FORECAST AREA. FOR TONIGHT...A COLD FRONT WILL DROP SOUTH OUT OF CANADA INTO AREA NEAR THE INTERNATIONAL BORDER. AS THE FRONT MOVES SOUTH INTO MINNESOTA...RAIN AND/OR SNOW SHOWERS WILL DEVELOP ALONG AND AHEAD OF THE FRONT. THE GFS IS MORE AGGRESSIVE WITH THE SOUTHERN EXTENT AND PRECIP AMOUNT THAN THE NAM. WILL LEAN TOWARD THE NAM FOR FORECAST FOR FRIDAY AND FRIDAY NIGHT. WILL GO WITH CHC POPS FOR PRECIP ACROSS NORTHERN FORECAST AREA FOR FRIDAY AND TAKE POPS FURTHER SOUTH FRIDAY NIGHT. EXTENDED...A DEEPENING LOW PRESSURE SYSTEM LOOKS TO AFFECT THE AREA LATE SATURDAY THROUGH SUNDAY NIGHT. MODELS ARE MERGING TOWARD A SOLUTION...BUT WE PREFERRED A BLEND OF THE ECMWF AND GFS. THE EXTENT TO WHICH AN ARCTIC BOUNDARY AND CANADIAN HIGH PRESSURE DIP SOUTH ON SATURDAY WILL PLAY A SIGNIFICANT ROLE IN THE ULTIMATE TRACK OF THE SURFACE LOW. STILL...WE HAVE MORE CONFIDENCE THAT A MAJOR SYSTEM WILL AFFECT AT LEAST THE SOUTHERN ONE THIRD OF THE AREA LATE IN THE WEEKEND. FORECAST SOUNDINGS POINT AT AN EXTENDED PERIOD OF MIXED PRECIPITATION...PERHAPS TRANSITIONING TO ALL SNOW TOWARD THE END OF THE EVENT. AS THE AFOREMENTIONED COLD FRONT TURNS STATIONARY ON SATURDAY NIGHT...IT WILL GRADUALLY TRANSITION TO A WARM FRONT. A ROBUST LOW LEVEL JET...IMPRESSIVE OMEGA...AND SOME UPPER LEVEL DIVERGENCE CERTAINLY RAISE THE RISK FOR HEAVIER PRECIPITATION. THE GFS CONTINUES TO BE THE FURTHEST SOUTH...WHILE THE NAM AND ECMWF ARE FARTHER NORTH. CERTAINLY LOOKS LIKE A STRONG SYSTEM...FUTURE MODEL RUNS WILL BE ABLE TO BETTER PINPOINT THE EXACT TRACK AND PRECIPITATION TYPES. AVIATION... VFR CONDITIONS TO PREVAIL THROUGH TONIGHT...BUT AS WINDS DIMINISH AND LOW LEVEL MOISTURE INCREASES...IN PART DUE TO CONSIDERABLE SNOW MELT...AREAS OF FOG MAY ONCE AGAIN DEVELOP FROM ROUGHLY 06Z-14Z. WINDS WILL REMAIN GENERALLY WEST TO SOUTHWEST THROUGH MIDDAY FRIDAY. A WEAK COLD FRONT WILL PUSH SOUTHEAST FROM CANADA EARLY FRIDAY MORNING...AND BRING SOME INCREASE IN CLOUDS AND PERHAPS SOME LIGHT SNOW...ESPECIALLY AT KINL...AFTER ABOUT 15Z. AVIATION... && POINT TEMPS/POPS... DLH 28 48 27 42 / 0 20 20 10 INL 27 45 21 39 / 0 30 20 10 BRD 28 54 27 44 / 0 20 20 20 HYR 26 53 28 49 / 0 20 20 10 ASX 27 53 28 44 / 0 20 20 10 && .DLH WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. LS...NONE. $$ GSF
AREA FORECAST DISCUSSION
NWS EL PASO TX/SANTA TERESA NM
304 PM MDT THU APR 3 2008 .SYNOPSIS... AN UPPER LEVEL TROUGH OF LOW PRESSURE EMBEDDED IN A STRONG JET STREAM ALOFT WILL MOVE ACROSS SOUTHERN NEW MEXICO THURSDAY EVENING. BREEZY TO GUSTY WINDS ASSOCIATED WITH THIS SYSTEM WILL GRADUALLY DIMINISH AFTER MIDNIGHT. TEMPERATURES WILL RUN AROUND 3 TO 5 DEGREES COOLER FRIDAY AFTERNOON ALONG WITH LIGHTER NORTH TO NORTHWEST WINDS. DRY CONDITIONS WITH ABOVE SEASONAL TEMPERATURES WILL CONTINUE THIS WEEKEND INTO NEXT WEEK...WITH BREEZY CONDITIONS AGAIN ON SATURDAY. WE WILL CONTINUE TO SEE BREEZY TO WINDY CONDITIONS JUST ABOUT EVERY DAY NEXT WEEK...ESPECIALLY BY MIDWEEK. && .DISCUSSION... OVERALL FCST CONDS ON SCHEDULE. EXPECT SHORT WAVE TROUGH PASSAGE AROUND 06Z. 19Z AIRCRAFT REPORT AT 37K MSL HAD WINDS OF 250/117KT WITH ABOUT 20 DEG OF VEERING FROM THIS MORNING. EPZ HAD LIMITING ANGLES ON THE 12Z RUN THUS NO WINDS ABOVE H3. GFS WINDS ALOFT FORECAST PROFILE HAD 60 KTS OF VERTICAL SHEAR FCST FROM H5 TO H4 THIS EVENING OVER EL PASO POSSIBLE WHICH CUD TRANSLATE INTO SVR TURBC. WATER VAPOR SHOWS DUAL TRACKS OF SUBTROPICAL JET SOUTH AND POLAR FRONT JET NORTH OF ERL PASO...HENCE...ENHANCED STRONG JET STREAM WINDS SLOWLY TRANSLATING EAST. IF YOU CONTOUR THE COLD AIR CUMULUS FIELD ON THE 20Z VISIBLE SATELLITE THE TROUGH AXIS IS ON THE MEX/AZ BORDER SO MODELS APPEAR ON TARGET. RED FLAGS SHOULD EXPIRE AT 02Z. MIGHT AS WELL JUST DECLARE NEXT WEEK "BREEZY TO WINDY" WEEK IN EL PASO WITH EXTENDED MOS GUIDANCE GIVING EVERY DAY A MINIMUM CATEGORY OF BREEZY CONDS. GFS AND ECMWF HIT US HARD WED AND THU WITH A LARGE AMPLITUDE TROUGH AND GFS AT THIS TIMES BRINGS THE MAX WIND FIELD INTO EL PASO BETWEEN 18Z/WED AND 06Z THURSDAY WITH 40KT H8...50KT H7...AND 80KT H5 WHICH IF IT HOLDS TRUE = HIGH WIND WARNING. NOT TIMING WILL BE THE DRIVER HERE AS THE PHYSICS IS PRETTY MUCH CONSISTENT ON PRODUCING HIGH WINDS BUT ANY CHANGE IN THE FREQUENCY OF THIS WAVE WILL DICTATE A LARGE CHANGE IN THE IMPACT IF FOR EXAMPLE THE SPEED MAX ARRIVAL TIME IS 12 HOURS LATER OR EARLIER. ECMWF IS MORE AGGRESSIVE ON THE QPF THAN THE GFS AND SUGGESTS POSSIBLE SHOWERS IN THE NORTHERN TIER OF THE CWA THEN. DID NOT CHANGE PREVIOUS PKG`S POPS AND KEPT THEM BELOW 10 PCT AT THIS TIME PENDING MORE FORECAST ITERATIONS. MEDIA OUTLETS MAY WANT TO RE EMPHASIZE THE CONTINUED HIGH (PLUS) FIRE DANGER CONTINUING IN ALL ZONES WHICH JUST GETS REAGGRAVATED WITH EACH ADDTIONAL SHORT WAVE. && AVIATION...VALID 04/00Z - 05/00Z VFR CONDITIONS THROUGH THE PERIOD...SCT CIRRUS 150-250 AGL. BREEZY TO WINDY CONDITIONS THROUGHOUT THE PERIOD WILL CAUSE MODERATE OR GREATER LOW LEVEL MECHANICAL TURBULENCE WEDNESDAY AFTERNOON AND THROUGH THURSDAY ESPECIALLY OVER AND EAST OF MOUNTAINS. && .FIRE WEATHER.. A DISTURBANCE IN THE STRONG WESTERLY FLOW ALOFT PASSING OVER THE AREA EARLY THIS EVENING WILL CONTINUE TO KEEP MOST AREAS DRY...BREEZY AND WINDY IN SOME AREAS. WITH RELATIVE HUMIDITIES ALREADY AS LOW AS THE SINGLE DIGITS FOR MANY LOWLAND LOCALES...EXPECT RED FLAG CONDITIONS TO CONTINUE THROUGH EARLY THIS EVENING. WE SHOULD SEE A BREAK FROM THE WINDS FRIDAY AS HIGH PRESSURE ALOFT BUILDS ACROSS THE REGION. DRY SPRING LIKE WEATHER WILL CONTINUE OVER THE WEEKEND AND INTO NEXT WEEK...WITH BREEZY TO WINDY CONDITIONS TO RETURN EACH AFTERNOON. THIS WILL LIKELY BRING CONDITIONS BACK NEAR OR ABOVE RED FLAG CRITERIA...ESPECIALLY MIDDLE OF NEXT WEEK WHERE A LARGE TROUGH COULD BRING VERY WINDY CONDITIONS ACROSS OUR FIRE WEATHER ZONES. && .PRELIMINARY POINT TEMPS/POPS... EL PASO 48 75 45 81 52 / 0 0 0 0 0 SIERRA BLANCA TX 46 75 43 81 45 / 0 0 0 0 0 LAS CRUCES 45 74 42 80 46 / 0 0 0 0 0 ALAMOGORDO 44 75 41 81 46 / 0 0 0 0 0 CLOUDCROFT 32 52 30 60 33 / 0 0 0 0 0 TRUTH OR CONSEQUENCES 43 73 40 79 45 / 0 0 0 0 0 SILVER CITY 38 66 37 71 40 / 0 0 0 0 0 DEMING 44 74 41 80 46 / 0 0 0 0 0 LORDSBURG 44 75 41 81 46 / 0 0 0 0 0 && .EPZ WATCHES/WARNINGS/ADVISORIES... NM...RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR NMZ111>113. TX...RED FLAG WARNING UNTIL 8 PM MDT THIS EVENING FOR TXZ055-056. && $$ 20/22 NOVLAN
AREA FORECAST DISCUSSION
NWS HOUSTON/GALVESTON TX
946 AM CDT WED APR 2 2008 .DISCUSSION... DIFFUSE FRONTAL BOUNDARY SITTING ACROSS SRN PARTS OF THE AREA SHOULD HEAD BACK NORTH AS A WARM FRONT LATER TODAY. MORNING SOUNDINGS AND AIRCRAFT SOUNDINGS INDICATE A NOTICEABLE CAP THAT SHOULD BE PRETTY TOUGH TO OVERCOME. WOULD NEED TO WARM TO 84+ FOR THIS TO OCCUR. THINK ISOLATED POPS ALREADY IN THE FCST SHOULD COVER THAT WELL. TEMPS ALSO LOOK GOOD. TWEAKED THE CLOUD COVER & WINDS IN THE GRIDDED DATA BASED ON LATEST CONDITIONS/OBS. DON`T THINK IT`LL RESULT IN MANY CHANGES IN THE TEXT PRODUCTS BUT WILL GO AHEAD AND RUN THEM AND SHIP THEM OUT ANYWAYS. 47 && .PRELIMINARY POINT TEMPS/POPS... COLLEGE STATION (CLL) 78 67 80 63 72 / 20 10 10 40 40 HOUSTON (IAH) 81 67 82 66 74 / 20 10 10 20 50 GALVESTON (GLS) 78 69 77 68 76 / 20 10 10 10 50 && .HGX WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
330 AM PDT FRI APR 4 2008 .SYNOPSIS...THE MARINE LAYER AND ONSHORE FLOW WILL BRING LOW CLOUDS...LOCAL FOG AND DRIZZLE WEST OF THE MOUNTAINS DURING THE NIGHTS AND MORNINGS. PARTIAL AFTERNOON CLEARING THIS WEEKEND. LOCAL GUSTY WINDS IN THE MOUNTAINS AND DESERTS AT TIMES. OTHERWISE...FAIR THROUGH EARLY NEXT WEEK. UPPER LEVEL LOW PRESSURE WILL CAUSE A SLIGHT CHANCE OF SHOWERS TOWARD WEDNESDAY. FAIR AND WARMER DURING THE END OF NEXT WEEK UNDER HIGH PRESSURE. && .DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO... ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES. .SHORT TERM (TODAY-SUN)...THERE WERE AREAS OF LOW CLOUDS AND FOG IN THE COASTAL SECTION AND SAN DIEGO INLAND VALLEYS THIS MORNING. THERE WERE ALSO A FEW HIGH CLOUDS. EARLY MORNING ACARS SOUNDINGS INDICATED AN INVERSION BASED NEAR 1000 FT N AND 3000 FT S WITH MODERATELY STRONG NW WINDS ALOFT. ONSHORE GRADIENTS WITH ABOUT 5 MB SAN-IPL. WEAK UPPER RIDGING TODAY WILL GIVE WAY TO FLAT OR WEAKLY CYCLONIC FLOW ALOFT SAT AND SUN WITH A COUPLE OF SHORT WAVES TROUGHS MOVING PAST TO THE N. AN EDDY IS EXPECTED TO DEVELOP TONIGHT AND CONTINUE THROUGH SUN. THIS WILL DEEPEN THE MARINE LAYER TONIGHT TO 3000-4000 FT DEEP WITH LITTLE CHANGE SAT NIGHT. THERE COULD BE LOCAL DRIZZLE FROM THE DEEPER MARINE LAYER AND ONLY PARTIAL AFTERNOON CLEARING W OF THE MOUNTAINS. PATCHY DENSE FOG NEAR THE INLAND EXTENT OF THE STRATUS AND ON HIGHER COASTAL TERRAIN. THERE WILL ALSO BE VARIABLE HIGH CLOUDINESS. MODERATELY STRONG ONSHORE GRADIENTS AND WINDS ALOFT WILL CAUSE LOCAL GUSTY WINDS...MAINLY IN THE MOUNTAINS AND DESERTS DURING THE AFTERNOONS AND EVENINGS. WINDS SHOULD REMAIN BELOW ADVISORY STRENGTH WITH LOCAL GUSTY 30 TO 40 MPH. WARMER TODAY THEN COOLER SAT AND SUN. && .LONG TERM (MON-THU)...WEAK UPPER RIDGING WILL CAUSE A SHALLOWER MARINE LAYER...A LITTLE WARMING AND LESS WIND EARLY NEXT WEEK. ANOTHER TROUGH SHOULD BRING MORE CLOUDS AND COOLING TOWARD MID WEEK WITH A SMALL CHANCE OF LIGHT SHOWERS. LOCAL GUSTY WINDS WILL ALSO RETURN TO THE MOUNTAINS AND DESERT WITH THE PASSING TROUGH. A BUILDING UPPER RIDGE IS EXPECTED TO BRING FAIR AND WARMER WEATHER TOWARD THE END OF NEXT WEEK. && .AVIATION... 041000Z...THE HEIGHT OF THE MARINE INVERSION RANGES FROM AROUND 1200 FEET AT LOS ANGELES TO 1500 FEET AT SAN DIEGO. STRATUS WILL EXTEND INLAND TO THE LOWER COASTAL VALLEYS WITH AREAS OF CEILINGS OF 1000 TO 1500 FEET WITH LOCAL CEILINGS OF 400 TO 800 FEET. AREAS OF VISIBILITIES OF 3 TO 5 STATUTE MILES FROM THE COAST INLAND TO THE LOWER COASTAL VALLEYS WITH LOCAL VISIBILITIES OF 1 TO 3 STATUTE MILES. THE STRATUS WILL CLEAR BACK TO THE COAST BY AROUND 17Z. STRATUS WILL BEGIN TO SPREAD BACK IN SLOWLY AFTER 02Z WITH AREAS OF STRATUS SPREADING FROM THE COAST INLAND TO THE LOWER COASTAL VALLEYS BETWEEN 06Z AND 12Z SATURDAY. THE MARINE LAYER IS EXPECTED TO DEEPEN SLIGHTLY TONIGHT WITH LITTLE CHANGE IN CEILINGS AND VISIBILITIES. PATCHY DRIZZLE IS POSSIBLE AFTER 10Z. CONTINUED VFR FOR THE MOUNTAINS AND DESERTS. MARTIN && .SGX WATCHES/WARNINGS/ADVISORIES...NONE. && $$ PUBLIC...DA AVIATION...MARTIN
AREA FORECAST DISCUSSION
NWS MOUNT HOLLY NJ
133 AM EDT FRI APR 4 2008 .SYNOPSIS... LOW PRESSURE DEVELOPING OVER THE MISSISSIPPI VALLEY WILL MOVE ACROSS PENNSYLVANIA ON FRIDAY AND SEND A SERIES OF FRONTS ACROSS THE AREA. THE FRONT WILL SETTLE TO THE SOUTH FRIDAY NIGHT AND THEN ANOTHER LOW PRESSURE SYSTEM WILL MOVE ALONG IT SATURDAY. DRIER WEATHER WILL ARRIVE SUNDAY AND REMAIN INTO EARLY NEXT WEEK. && .NEAR TERM /THROUGH TODAY/... EVAPORATIVE COOLING HAS CAUSED TEMPERATURES TO DROP DOWN TO FREEZING (OR JUST UNDER) OVER THE HILLS OF THE NORTHERN 3 ZONES. SO, A WINTER WEATHER ADVISORY WAS ISSUED FOR THE OVERNIGHT PERIOD UNTIL TEMPERATURES AND DEW POINTS RISE TOWARD MORNING. SOME SPOTTY FREEZING RAIN WAS BEING REPORTED AT KMPO. EVEN THOUGH GROUND TEMPERATURES HAVE BEEN WARM, IT WAS FELT THAT AN ADVISORY WOULD BE PRUDENT FOR A FEW HOURS OVERNIGHT. SLEET HAD OCCURRED AT MANY PLACE OVER OUR WESTERN ZONES EARLIER. OTHERWISE, THE REGIONAL RADAR LOOP SHOWS THAT THE RAIN IS STEADILY MOVING OVER THE AREA FROM THE SOUTH AND WEST, ALTHOUGH THERE ARE SOME BREAKS AND PRECIPITATION MAY BECOME SPOTTY AT TIMES. QPF TONIGHT OF ONE THIRD TO TWO THIRDS OF AN INCH IS EXPECTED WITH STEADY RAINS CONTINUING FRIDAY MORNING. FLOODING CONCERNS ARE NIL IN THE SHORT TERM. && .SHORT TERM /TONIGHT THROUGH 6 PM SATURDAY/... A WET PERIOD FOR SURE! DEBATED WHETHER I SHOULD JUST WRITE RAIN...RAIN...RAIN IN THE ZONES, BUT OPTED JUST TO TWEAK THE COMPUTER WORDS FOR NOW. THE FIRST WAVE WILL PRODUCE STEADY RAINS AS IT MOVES BY FRIDAY AND THEN THE COLD FRONT WILL MOVE JUST OFFSHORE FRIDAY NIGHT. ANOTHER WAVE WILL MOVE ALONG IT SATURDAY AND BRING A RENEWAL OF RAINS DURING SATURDAY. WHILE I AM NOT EXPECTING A GREAT DEAL OF CONVECTION FRIDAY OR SATURDAY, I WILL LEAVE THE CHC FOR THUNDER IN THE SOUTHERN ZONES GIVING A NOD TO THE PREVIOUS GRIDS AND THE DAY2 SPC WHICH HAS A GENERAL T-STORM OUTLOOK FOR THE SRN AREAS. QPF FOR THE SHORT TERM PERIOD WILL BE FAIRLY SIGNIFICANT WITH THE LATEST SHORT TERM MODELS OFFERING (STORM TOTAL QPF OF) ONE TO TWO INCHES TOTALS NORTH AND PERHAPS 2 OR 3 INCHES SOUTH. THE SOUTHERN AREAS CAN HANDLE ANY EXTRA RAINFALL TO A GREATER DEGREE CONSIDERING THE SOIL TYPE AND CURRENT DROUGHT CONDITIONS. THE AREAS MORE SUSCEPTIBLE TO FLOODING ARE FURTHER NORTH ACROSS THE LEHIGH AND RARITAN VALLEYS. SINCE ANY FLOODING CONCERNS WILL TAKE PLACE LATER SATURDAY OR SATURDAY NIGHT AT THE EARLIEST, WE DECIDED NOT TO ISSUE ANY FLOOD WATCH AT THIS TIME. WE WILL LOOK AT THIS AGAIN ON FRIDAY. && .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/... ONCE AGAIN, THIS IS A FAIRLY LOW CONFIDENCE FCST. THE GFS INDICATES THE COLD FRONT WILL BE THROUGH THE AREA AND SUNDAY WOULD BE PREDOMINANTLY DRY, AS HIGH PRESSURE BUILD IN. THE ECMWF BRINGS ANOTHER WAVE THROUGH THE AREA ON SUNDAY, WHICH WOULD KEEP MOST OF SUNDAY WET. THE CANADIAN IS SOMEWHERE IN THE MIDDLE. FOR NOW, WILL KEEP LATER SUNDAY DRY, BUT WILL NEED TO WATCH THIS. HIGH PRESSURE WILL THEN BUILD TO THE N, KEEPING E TO NE FLOW OVER THE REGION, POPS LOOK TO VERY LOW ON MONDAY AND SOME SCHC ON TUESDAY ATTM. THE GFS AND ECMWF ARE IN DECENT AGREEMENT ON THESE TOW DAYS. BY WEDNESDAY, BOTH MODELS BRING A LOW ACROSS THE UPR MS VLY AND A WARM FRONT WILL CROSS THE REGION, FOLLOWED BY A WEAK CDFNT ON THURSDAY. CHC POPS WILL REMAIN IN THE FCST ON THURSDAY WITH THE FRONT. TEMPS LOOK TO BE AOA NORMAL, WITH HIGHS MAINLY IN THE UPPER 50S TO 60S THRU THE PD. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... WITH THE CURRENT TAFS ABOUT TO BE ISSUED POOR CIGS AND VSBYS ARE EXPECTED TO OCCUR THROUGHOUT THE TAF FCST PERIOD. WE ARE EXPECTING IFR CONDITIONS TO DEVELOP TONIGHT AND CONTINUE INTO FRIDAY MORNING AT THE LEAST. THE LATEST ACARS SOUNDINGS FROM AROUND THE LOCAL AREA STILL SUPPORT THE POTENTIAL FOR SLEET AS THEY ARE CLOSE TO MODEL FORECAST SOUNDINGS WITH CONSIDERABLE DRY AIR JUST ABOVE THE SURFACE. AS THE COLUMN OF THE AIR MASS CONTINUES TO BE MOISTENED BY THE FALLING PRECIPITATION, WE EXPECT WIDESPREAD IFR CONDITIONS TO DEVELOP. RIGHT NOW WE DID NOT CARRY ANY LLWS IN THE TERMINAL FORECASTS AS THE FCST LLJ IS BELOW CRITERIA. THE KACY AND KMIV TERMINALS ARE THE MOST SUSCEPTIBLE BECAUSE OF THEIR CLOSER PROXIMITY TO THE STRONGER FORECAST JET. THE FORECAST MODELS ARE FORECASTING THE WARM FRONT TO LIFT NORTH THROUGH THE TERMINALS ON FRIDAY. PROBABLY NOT IN TIME TO PREVENT IFR CONDITIONS FROM OCCURRING DURING THE MORNING COMMUTE. THE LEAST CONFIDENCE ABOUT THIS OCCURRING ARE AT KRDG AND KABE. THAT IS THE REASON WE LEFT PRECIPITATION IN THROUGH THE END OF THE TAF FORECAST PERIOD. ELSEWHERE WHILE WE CAN NOT RULE OUT SOME PRECIPITATION, BELIEVE OVER HALF OF THAT FORECAST PERIOD WILL BE DRY. WITH THOSE TERMINALS EXPECTED TO BE IN THE WARM SECTOR WE DID SHOW IMPROVEMENT IN CIGS AND VSBYS ABOVE GUIDANCE TO MVFR LEVELS. OUTLOOK... LOW CIGS/VSBYS WILL LIKELY CONTINUE THROUGH SATURDAY WITH IMPROVING CONDITIONS ON SUNDAY. GENERALLY VFR CONDITIONS THEN INTO EARLY NEXT WEEK. && .MARINE... SMALL CRAFT ADVISORY FOR THE COASTAL WATERS BEGINNING TONIGHT AT 200 AM AND CONTINUING INTO ALL OF FRIDAY NIGHT. LATEST NAM AND GFS SUPPORT WINDS STRONG ENOUGH TO BUILD SEAS TO SCA CRITERIA. LATEST WAVEWATCH HAS WAVES UP TO 7 FT. EXPECT CONDITIONS TO REMAIN JUST BELOW SCA CRITERIA FOR THE BAY...THIS WILL NEED TO BE MONITORED. MAY NEED TO EXTEND SCA INTO SATURDAY DEPENDING ON HOW STRONG WINDS ARE POST FRONTAL PASSAGE. SEAS STAY RELATIVELY HIGH (NEAR SCA CONDITIONS) INTO EARLY NEXT WEEK WITH PROLONGED PERIOD OF ONSHORE FLOW WITH A LONG FETCH. USED WAVEWATCH GUIDANCE FOR WAVE GRIDS WILL LITTLE MODIFICATION. WAVES ON DE BAY BASED ON WIND FORECAST. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...WINTER WEATHER ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR PAZ054-055. NJ...WINTER WEATHER ADVISORY UNTIL 6 AM EDT EARLY THIS MORNING FOR NJZ001. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT SATURDAY FOR ANZ450>455. && $$ SYNOPSIS...O`HARA NEAR TERM.../ O`HARA SHORT TERM...O`HARA LONG TERM...NIERENBERG AVIATION...GIGI/GSZAT MARINE...GIGI/GSZAT
AREA FORECAST DISCUSSION
NWS NORTHERN INDIANA
116 AM EDT FRI APR 4 2008 .AVIATION... SFC LOW MOVG INTO MID MS VALLEY WITH WARM FRONT EXTENDING TO ITS EAST ACROSS SRN INDIANA. OCNL +SHRA AND LIFR/IFR CONDITIONS HAVE DEVELOPED NORTH OF THE WARM FRONT OVER NRN INDIANA. STRONG FORCING AND SHRA WILL MOVE EAST OF THE TERMINALS AROUND 06Z... HOWEVER SATURATED LOW LEVELS AND DEVELOPING LOW LEVEL CAA AS THE LOW MOVES EAST OVERNIGHT SHOULD RESULT IN CONTINUED OCNL -RA/DZ AND LOW CIGS. FLYING CONDITIONS WILL SLOWLY IMPROVE DURING THE DAY/EVENING AS SFC RIDGE BUILDS INTO THE AREA FROM THE WEST. && .PREV DISCUSSION... /ISSUED 807 PM EDT THU APR 3 2008/ UPDATE... SIG EXPANSION OF CONVN ONGOING ATTM FM SE MO INTO WRN KY IN RESPONSE TO INCREASING LARGE SCALE ASCENT AHD OF LEAD SW TROUGH LIFTING QUICKLY EWD OUT OF ERN IA. HWVR THIS HAVING A DETRIMENTAL EFFECT SO FAR ON NWD MSTR TRANSPORT IN OTHERWISE FVRBL LOW-MID LVL WAA PATTN AND DENOTED AS SUCH W/LACK OF PCPN ECHOES ACRS NRN IN AND CERTAINLY ACCENTUATED BY LAST VESTIGE OF OLD POLAR RIDGE AND EXTREMELY DRY SUB CLOUD LYR IN PLACE. NONETHELESS XPC INCREASING LL SATURATION THROUGH MID EVENING W/INCREASING LARGE SCALE ASCENT AHD OF EJECTING VIGOROUS MID LVL TROUGH W/RECENT EXPANSION OF ECHOES ACRS CNTRL/NRN IL ON NOSE OF LL JET WITHIN SHARP LL THETA-E GRADIENT. BTR COMBINATION OF MODEST MID LVL LAPSE RATES AND THETA-E SUGGEST ANY ISOLD THUNDER THREAT THIS EVENING WILL REMAIN ACRS THE FAR SOUTH AND WILL DROP MENTION ACRS THE NORTH. MAIN CHG WRT TO GOING GRIDS WAS TO BACKUP CAT MENTION EARLIER THIS EVENING WHILE RAMPING THINGS DOWN QUICKLY FM 06-12Z AND DROPPING MENTION ALTOGETHER AFT 12Z XCP FAR SE EARLY GIVEN LOOK AT 18Z GUIDANCE AND TRENDS. SHORT TERM (TONIGHT THROUGH FRIDAY AFTERNOON)... SUNNY TO PARTLY SUNNY DAY WITH TEMPS NEARING NORMAL COMING TO A CLOSE AS CLOUDS WILL START TO INVADE THE FORECAST AREA LATE THIS AFTERNOON INTO THE EVENING AHEAD OF THE NEXT SYSTEM DEVELOPING ACROSS THE SOONER STATE. SLIGHT TIMING/POSITION DIFFERENCES BETWEEN THE MAJOR AMERICAN MODELS GFS/NAM12. 12Z RUNS SHOWS GFS SLIGHTLY FASTER (3-6HRS) THAN THE 12Z NAM12/09Z SREF/12Z UKMET AND 12Z NGM. WILL LEAN TOWARDS THE CONSENSUS AND THE 09Z SREF WHICH BLENDS OUT SOME OF THOSE SLIGHT TIMING AND STRENGTH DIFFERENCES BUT HOLDS CLOSER TO THE NAM GROUPING. SFC BOUNDARY NEAR THE OH RIVER...WITH DEWPOINTS IN THE 20S ACROSS THE REGION WITH DEWPTS IN THE UPPER 40S AND 50S SOUTH OF THE BOUNDARY. ACARS SOUNDINGS FROM THIS MORNING SHOW DEEP AND IMMENSE LAYER OF DRY AIR FROM AROUND 925 TO 700MB. SFC DEPRESSIONS ACROSS THE REGION ARE MORE THAN 20 TO 30 DEGREES AT MOST SITES...IT WILL TAKE SOME TIME FOR THE LOWER LEVELS TO MOISTEN AND HAVE HELD OFF ANY SIGNIFICANT CHCS FOR POPS UNTIL THIS EVENING...MOST LIKELY AFTER 02-04Z AS THE FIRST SFC WAVE MOVES EAST ALONG THE BOUNDARY TOWARDS THE OHIO VALLEY PULLING MOISTURE FROM THE GULF INTO THE REGION. MODEST ISENT LIFT IN THE 290-295K SFCS AFT 00Z...WITH STRONG CONVERGENCE SEEN IN THE H850 AND H700 LVLS ACROSS THE REGION THRU ABOUT 06-08Z. VERY STRONG UPPER LVL JET OF 130-140 KTS WITH THE AREA POSSIBLY IN THE PREFERRED RIGHT ENTRANCE THRU ABOUT 12-15Z. ONE FINAL INGREDIENT IS POSSIBLE CSI/SLANTWISE INSTABILITY OR WEAK ELEVATED CAPE SEEN THROUGH THE 03-08Z TIMEFRAME ACROSS THE REGION WHICH WILL ALLOW FOR CHC OF THUNDER. HAVE KEPT VERY HIGH CAT POPS...BUT HAVE THEM MAINLY IN THE 03-08Z TIMEFRAME WITH CHC POPS ELSEWHERE. AS THE SIGNIFICANT MOISTENING OF THE LOWER LEVELS OCCURS THE CIGS WILL DROP THRU THE NIGHT...WEAK LIFT WILL REMAIN WITH THE JET SUPPORT MENTIONED EARLIER AND THE WEAKENING DEFORMATION AREA MOVING THRU...-DZ AND LIGHT RAIN WILL BE POSSIBLE THRU THE MORNING.AS EVERYTHING STARTS TO PULL FURTHER EAST THE CLOUDS MAY START TO LIFT AND BREAK SLIGHTLY BY LATE AFTERNOON. TEMPS WILL DROP INTO THE UPPER 30S OR LOWER 40S OVERNIGHT...AND WITH THICK CLOUD COVER MOST OF THE DAY ALONG WITH POSSIBLE LIGHT RAIN OR DZ AND NORTHERLY WINDS...LITTLE DIURNAL BUMP WILL HAPPEN FRIDAY WITH AFTN HIGHS BELOW NORMAL IN THE MID AND MAYBE UPPER 40S. LONG TERM... FRIDAY NIGHT THROUGH SATURDAY VERY ACTIVE PATTERN IN STORE FOR NEXT WEEK...AS SEVERAL STRONG MID LEVEL WAVES TAKE AIM AT THE REGION. WATER VAPOR AND VISIBLE SATELLITE CONFIRM NUMEROUS MID LEVEL WAVES OVER THE PACIFIC WITH THE SEMI-PERMANENT ALEUTIAN LOW CONTINUALLY AIDING IN PROPAGATION AND DEEPENING OF TRANSIENT WAVES TO THE SOUTH. PATTERN SHIFT IS EXPECTED AS THE SEEMINGLY ANCHORED UPPER LEVEL HIGH OVER GREENLAND WILL BREAK DOWN AND ALLOW A SHIFT IN TROUGHING TO THAT REGION. THIS FLOW SHIFT WILL PUSH THE HUDSON BAY VORTEX EAST ALLOWING EASTERN CONUS RIDGING AND EVENTUAL WEST COAST TROUGHING TO DEVELOP. THIS PATTERN SHIFT IS HIGHLIGHTED BY MEAN GFS ENSEMBLE PNA PROGS...WHICH CONTINUE TO SUPPORT A NEGATIVE PNA TENDENCY INTO THE LONG TERM PERIOD. THIS WILL SPELL AN ACTIVE PATTERN FOR THE REGION AS A SERIES OF MODERATE TO POTENT UPPER LEVEL WAVES WILL TRAVERSE THE GREAT LAKES IN MEAN SOUTHWEST FLOW...LENDING TO A PROPENSITY FOR RAIN AND THUNDERSTORMS. GIVEN THE AMPLIFIED NATURE OF THE FLOW NEXT WEEK...WOULD NOT RULE OUT A SEVERE WEATHER EVENT SOMEWHERE ACROSS THE MIDWEST...AS HEAT AND MOISTURE WILL BE SHIFTING NORTH. WITH A SHIFT TO EASTERN CONUS RIDGING WILL COME WARMER TEMPS AS HIGHS IN THE 60S WILL BE LIKELY WITH 70S POSSIBLE. OF COURSE FORECAST MODELS AND ENSEMBLES VARY GREATLY ON EVOLUTION OF THIS PATTERN SHIFT WITH NUMEROUS DISCREPANCIES IN SYSTEM STRENGTH/SPEED/TRACK AND QPF AS EXPECTED WITH THE HUGELY COMPLICATED FLOW REGIME IN PLACE OVER THE PACIFIC. THERE ARE A FEW CONSISTENT SIGNALS PRESENT IN THE MODEL SOLUTIONS WITH SOME AGREEMENT NOTED ON THE PASSAGE OF A SYSTEM SUN NIGHT AND THE EVENTUAL EJECTION OF THE DEEP WESTERN US TROUGH THU INTO FRIDAY. ALTHOUGH MODELS ARE STILL INCONSISTENT WITH HOW THIS TROUGH WILL EJECT...EITHER IN TWO STAGES WITH A PRIMARY DIGGING WAVE TUES-WED OR A WEAK PRIMARY WAVE AND STRONGER LONG WAVE TROUGH EJECTION ON THURS. SAT AND SUNDAY...BOTH WEEKEND DAYS LOOK EXCELLENT AS WEAK HIGH PRESSURE WILL DOMINATE THE WEATHER. TEMPS IN THE 50S/LOWER 60S LOOK GOOD ESPECIALLY AWAY FROM THE LAKE AS WEAK WAA WILL BE ONGOING THROUGH THE PERIOD PER INCREASING H85 TEMPS. HAVE ADJUSTED TEMPS NEAR LAKE MICHIGAN SATURDAY GIVEN WEAK FLOW AND FAIRLY STRONG DAYTIME HEATING. EXPECTING A LAKE GRAVITY CURRENT TO DEVELOP AND HOLD TEMPS IN THE 40S ALONG THE LAKE SHORE. SUN NIGHT INTO MONDAY...RETAINED PRECIP CHANCES WITH A NORTHERN STREAM WAVE STILL LOOKING GOOD ACROSS THE REGION. ALTHOUGH FORECAST MODELS HAVE BEEN TRENDING THIS SYSTEM FATHER NORTH. TUESDAY THROUGH THURSDAY...THE GFS AND ECMWF HAVE CONTINUED TO DISPLAY A RATHER POTENT SW TROUGH ADVECTING THROUGH THE FLOW TUES INTO WED. HAVE ADDED POPS TO TUESDAY WITH RAIN/THUNDER CHANCES POSSIBLE ALONG THE WARM FRONT AND AHEAD OF THE COLD FRONT IN THE AFTERNOON. THURSDAY STILL LOOKS QUITE INTERESTING AS THE WESTERN TROUGH IS STILL PROGGED TO EJECT INTO THE MIDWEST. MODELS AND ENSEMBLES HAVE BEEN INCONSISTENT WITH THE AMPLIFICATION AND TIMING OF THIS WAVE. HAVE HELD OFF FROM ANY MAJOR DEVIATIONS FROM CLIMO THROUGH THIS PERIOD...WITH ONLY A POSITIVE TREND TO TEMPS GIVEN PROGGED H85 TEMPS AND H5 HEIGHTS. THIS SYSTEM WILL HAVE TO BE MONITORED AS IT WILL BE A HIGH IMPACT SYSTEM FOR THE EASTERN CONUS. QUESTION WILL BE WHERE...GIVEN THE HIGH SHEAR AND INSTABILITY PRESENT. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...NONE. MI...NONE. OH...NONE. LM...NONE. && $$ SHORT TERM...CHAMBERLAIN LONG TERM...SCHOTT AVIATION...JT UPDATE...HOLSTEN
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
415 AM EDT FRI APR 4 2008 .DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW SPLIT FLOW OVER NAMERICA WITH UPR GRT LKS BTWN ARCTIC BRANCH VORTEX CENTERED OVER NRN MANITOBA AND MORE ACTIVE POLAR/SUBTROPICAL FLOW ACRS THE SCNTRL CONUS. QUITE A BIT OF MID/HI CLD PERSISTS OVER THE FA IN THE RRQ OF H3 JET IN THE CONFLUENCE ZN BTWN THE BRANCHES AND TO THE N OF SRN BRANCH LO PRES MOVING THRU THE OH VALLEY. BUT 00Z GRB/INL/BIS/MPX RAOBS SHOW VERY DRY LLVL AIR IN PLACE OVER THE NRN TIER...SO NO LO CLDS ARE PRESENT DURING DIURNAL COOLING TIME/UNDER WEAK SFC RDG AXIS. NEXT SYS TO BE CONCERNED ABOUT IS A RATHER WEAK SHRWTV DROPPING ESEWD ACRS SRN SASKATCHEWAN OVER A FNT SEPARATING FAIRLY WARM AIR IN THE NRN PLAINS FM MUCH COLDER AIR FARTHER N IN MANITOBA...00Z H85 TEMP -17C AT YQD VS +3C AT BIS. BUT THE 00Z YQD SDNG IS ALSO BONE DRY... WITH PWAT JUST 0.06 INCH. BUT SOME LGT PCPN HAS BEEN FALLING FARTHER W IN SCNTRL SASKATCHEWAN CLOSE TO THE SHRTWV TRACK ON THE COLD SIDE OF FNTL BNDRY. ANOTHER POTENT SHRTWV IS CLOSING IN ON THE PAC NW. MAIN FCST CONCERNS THIS PACKAGE ARE PCPN CHCS ASSOCIATED WITH SHRTWV AND FNTL ZN TO THE NW AND HOW FAR S THE FNT WL PUSH OVER THE WEEKEND/IMPACT ON TEMPS. FOR TDAY...NAM/GFS SHOW SHRWTV NOW OVER SASKATCHEWAN MOVING INTO ONTARIO JUST NW OF LK SUP BY 00Z SAT...WITH ASSOCIATED SFC COLD FNT NEARING THE W END OF LK SUP AT THAT TIME. CONSIDERING THE DRYNESS OF AIR DEPICTED ON THE 00Z INL/BIS SDNGS...WL FOLLOW THE DRY NAM FCST EVEN THOUGH THAT MODEL (AS WELL AS GFS) SHOWS SFC DWPTS REACHING AN UNREALISTIC 40. EVEN MOS DWPTS IN THE MID 20S SEEM A BIT HI SINCE FULL MIXING OF 00Z MPX/INL/BIS SDNGS WOULD SUPPORT DWPTS FALLING TO 20F/15F/5F. OTRW...WITH UPR JET AXIS SHIFTING TO THE S...EXPECT MID/HI CLD NOW OVER THE FA TO GRDLY DRIFT IN THAT DIRECTION AS WELL. GIVEN DRY NATURE OF INCOMING AIRMASS AND DEEP MIXED LYRS SHOWN UPSTREAM...WL TEND TOWARD THE HI END OF MOS GUIDANCE. DEEP MIXING ON UPSTREAM SDNGS TO H7 WOULD SUPPORT HI TEMPS IN THE 50 TO 55 RANGE. PRESENCE OF RATHER FLAT PRES GRADIENT AND SFC HTG INLAND SUGS LK BREEZES WL DVLP AND KEEP COASTAL AREAS COOLER. AS SHRTWV/ACCOMPANYING SFC LO JUST NW OF LK SUP AT 00Z LIFT NEWD THRU ONTARIO TNGT...GFS/NAM PROG ATTENDANT COLD FNT TO SWING INTO THE NW ZNS BY 12Z SAT. GFS DEPICTS A MUCH SHARPER COLD FNT WITH BAND OF PCPN OVER WRN LK SUP BTWN 06Z-12Z UNDER SHARP H8-6 FGEN CLIPPING THE WRN ZNS. NAM SHOWS THIS FEATURE AS WELL BUT IS WEAKER...WITH ONLY A SML QPF OVER THE KEWEENAW BY 12Z. SHARP H85 THERMAL CONTRAST OBSVD UPSTREAM AT 00Z SUPPORTS THE GFS SCENARIO...BUT OVERALL DRYNESS WOULD SUG THE NAM IS MORE ON TRACK. WL TEND TO COMPROMISE AT THIS POINT WITH A CHC POP AFT 06Z OVER THE NW ZNS. NAM/GFS OFFER SGNFT DIFFERENCES AS TO THE WX THE REST OF THE WEEKEND. THE GFS SETTLES THE COLD FNT FARTHER S THAN THE NAM (AND THE UKMET) SO THAT WHEN THE SHRTWV NOW CLOSING IN ON THE PAC NW APRCHS LATE SAT INTO SUN...A RATHER SUBSTANTIAL SN/MIXED PCPN EVENT WOULD BE ON TAP FOR SAT NGT INTO SUN OVER THE NW ZNS WITH A MORE SUBSTANTIAL COLD AIRMASS TO BE OVERRUN/VERY SHARP H8-7 FGEN. NAM/ UKMET ON THE OTHER HAND HAVE THE MAIN OVERRNG SFC SETTING UP FARTHER NW WITH THE QPF MAX FOCUSED TO THE NW WITH THE ATMOSPHERE WARM ENUF FOR MAINLY RA EXCEPT AT THE ONSET OVER THE NW. CONSIDERING THE PERSISTENT NATURE OF BLOCKING UPR RDG OVER GREENLAND (NEGATIVE NAO)...THE CHILL OF THE AIRMASS TO THE NW...AND THE COLD WATERS OF LK SUP...WL TEND TOWARD THE GFS FCST WITH LOWER TEMPS/HIER POPS ESPECIALLY OVER THE NW HALF OF THE FA EVEN THOUGH THE 12Z/00Z ECMWF ALSO SUPPORT THE 00Z NAM/UKMET. IF THE GFS VERIFIES...PCPN TYPE LOOKS LIKE IT COULD BE A MAJOR HEADACHE WITH RATHER SHALLOW COLD AIR INFUSION OFFERING THE POTENTIAL FOR SOME FZRA/PL SAT NGT DURING DIURNAL MIN HTG TIME ON THE SE EDGE OF THE MAINLY SN AREA OVER THE KEWEENAW WITH SHARP FGEN ENHANCING THE AGEOSTROPHIC ADVECTION OF THE LLVL COLD AIR NOW TO THE NW INTO THE UPR GRT LKS. THE GFS SCENARIO WOULD REQUIRE A HEADLINE FOR THE NW...BUT CONSIDERING THE GREAT UNCERTAINTY AND THE MAJORITY OF THE MODEL GUIDANCE STACKED AGAINST THE GFS...WL HOLD OFF ON ANY MENTION OF HEADLINE AT THIS TIME FOR A POTENTIAL 4TH PD EVENT ESPECIALLY SINCE COORDINATION WITH NCEP HINTS THE GFS IS TOO QUICK TO BRING THE SHRTWV/DYNAMICS EWD (WHICH WOULD GIVE THE FNT MORE TIME TO SLIP BACK TO THE NW). COORDINATED WITH GRB/APX/DLH/NCEP. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... MAIN ISSUE REMAINS THE POTENTIAL FOR FOG FORMATION LATE TONIGHT... WHICH REMAINS UNCERTAIN. HIGH BASED CUMULUS CLOUDS OVER THE WESTERN U.P. ARE GRADUALLY DISSIPATING NOW...SO THEY MAY NOT BE AS MUCH OF A CONCERN AS PREVIOUSLY THOUGHT. IN ADDITION...HIGH CLOUDS CROSSING OVER SAWYER SHOULD CONTINUE TO THIN OUT THROUGH THE NIGHT... RESULTING IN A PERIOD OF CLEAR SKIES. WITH LIGHT WINDS... TEMPERATURES SHOULD DROP THROUGH THE DEWPOINTS...BUT THE PROBLEM OF FOG FORMATION MAY BE JUST THE DRY AIRMASS OVER THE AREA AS SEEN ON TAMDAR SOUNDINGS. FOR NOW HAVE FOLLOWED THE PREVIOUS FORECAST WITH VISIBILITIES NOT DROPPING BELOW MVFR AND CIGS STAYING VFR. FOG FORMATION WILL NEED TO BE MONITORED THROUGH THE NIGHT. OTHERWISE... VFR CONDITIONS ARE EXPECTED THROUGH FRI EVENING WITH DRY AIR HOLDING STRONG. A COLD FRONT WILL BE APPROACHING THE AREA...BUT JUST SOME MID CLOUDS ARE EXPECTED AT THIS TIME. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... WINDS WILL BE LESS THAN 20 KNOTS THROUGH SATURDAY AHEAD OF COLD FRONT. THE WINDS WILL INCREASE TO 30 KNOTS SATURDAY NIGHT IN THE WAKE OF THE FRONT. A COUPLE OF LOW PRESSURE SYSTEMS LIFTING INTO THE UPPER GREAT LAKES FROM THE SOUTHWEST MAY RESULT IN WINDS UP TO 30 KNOTS ON SUNDAY AND MONDAY. FOLLOWING THE LOW...WIND WILL DIMINISH TO 20 KNOTS OR LESS ON TUESDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...KC AVIATION...AJ MARINE...DLG
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
126 AM EDT FRI APR 4 2008 UPDATED AVIATION SECTION FOR 06Z TAF ISSUANCE. .UPDATE (ISSUED AT 1031 PM EDT THU APR 3)... FOG POTENTIAL REMAINS THE ISSUE FOR THE OVERNIGHT HOURS...AND HAS BECOME MORE UNCERTAIN DUE TO CLOUD ISSUES AND DRY AIR OVER THE CWA. FIRST AREA OF CLOUDS...MOSTLY CIRROSTRATUS...STRETCHES FROM CENTRAL WI ACROSS THE EAST HALF OF UPPER MI INTO NORTHERN LOWER MI. THIS AREA OF CLOUDS IS BEING SUPPORTED BY RIGHT ENTRANCE REGION FORCING UNDER A 100 KT JET IN EASTERN ONTARIO. THE SECOND AREA OF CLOUDS IS ALTOCUMULUS OVER WESTERN UPPER MI...ASSOCIATED WITH A WEAK SHRTWV TROUGH. SATELLITE TRENDS SHOW THE CIRROSTRATUS MOVING MUCH QUICKER TO THE EAST THAN THE ALTOCUMULUS...BUT WITH BOTH CLOUD FEATURES AROUND...TEMPERATURES ARE SLOW TO DROP. THE RUC ONLY SHIFTS THE ALTOCUMULUS INTO THE CENTRAL U.P. BY 12Z. ALSO...TAMDAR SOUNDINGS FROM CMX AND SAW INDICATE A LOT OF DRY AIR BELOW THE CLOUD BASE...LIKELY DUE TO STRONG MIXING THAT OCCURRED DURING THE DAY (MIXING HEIGHTS WERE UP TO 750MB). THE COMBINATION OF THE DRIER AIR AND THESE CLOUDS SHOULD KEEP ANY RADIATION FOG DEVELOPMENT LOCALIZED...AND THEREFORE HAVE DECREASED THE COVERAGE TO PATCHY. ALSO...WITH A FEW MORE CLOUDS AROUND...RAISED LOW TEMPS SLIGHTLY. && .SYNOPSIS... DESPITE DEEP SNOWPACK OVER MUCH OF UPR MI...STRONG APRIL SUNSHINE AND STEADY SW WINDS HELPING TO WARM TEMPS TO AROUND 50 IN MANY AREAS THIS AFTN. WARM TEMPS AND SOME H9-H7 MOISTURE ALONG WITH CONVECTIVE TEMPS NEAR 50 ALLOWED WIDESPREAD CU TO DEVELOP OVR WEST HALF THIS AFTN. THERE IS A HINT OF A SHORTWAVE PASSING ACROSS NORTHERN LAKE SUPERIOR SO SOME LIFT WITH THE INSTABILITY COULD RESULT IN ISOLD RAIN SHOWERS OVER THE NORTH CENTRAL EARLY THIS EVENING. RADAR LOOP WITH SOME ENHANCED ECHOES POINTS TO THIS POTENTIAL. NEXT ITEM OF CONCERN IS COLD FRONT AND SOME LIGHT PCPN COMING ACROSS UPR MI FRI NIGHT. AFTER A PRETTY QUIET WEEKEND...LONGWAVE PATTERN TURNS MUCH MORE ACTIVE NEXT WEEK WITH AT LEAST THREE CHANCES FOR SIGNIFICANT PCPN EVENTS. && .SHORT TERM (TONIGHT AND FRIDAY)... MAIN CONCERN IS FOG POTENTIAL LATE TONIGHT. SFC RIDGE OVER AREA SLOWLY SLIDES TO THE EAST THROUGH FRIDAY. DO NOT EXPECT NOTHING MORE THAN ISOLD SHOWERS THROUGH 00Z TONIGHT. COVERAGE IS HELD DOWN DUE TO DRY AIR SEEN BLO H8 ON 18Z TAMDAR FM KSAW. LOSS OF DAYTIME HEATING ALLOWS THE CU TO FADE BY LATE EVENING. ALSO...CI OVER SOUTHERN AREAS WILL SINK AWAY FM THE CWA. LOWER NEAR SFC LAYER OF MOISTURE WILL BE ON THE INCREASE DUE TO MELTING SNOW. LIGHT WINDS...THE ADDED MOISTURE...AND TEMPS COOLING INTO THE 20S SHOULD ALLOW SOME FOG TO DEVELOP OVER CNTRL AND ERN CWA LATE TONIGHT. GFS REMAINS PERSISTENT ON GENERATING SOME LIGHT QPF OVR WESTERN CWA AFT 18Z. GFS BUFKIT SOUNDINGS INDICATED SBCAPES NEAR 150J/KG AT 18Z TOMORROW...BUT IT ALSO SHOWS A SFC TD NEAR 40 WHICH SEEMS TOO HIGH. MODIFYING A SOUNDING FOR T/TD OF 47/30 GIVES CAPES BLO 50J/KG WHICH SEEMS MORE REASONABLE. NO OTHER GUIDANCE DEPICTS ANY QPF...BUT NO OTHER GUIDANCE DEPICTED QPF TODAY EITHER. RIGHT NOW THOUGH THINKING THERE WILL JUST BE A BUILD UP OF CU WITH NO PCPN. ANOTHER REASON FOR DRY FCST ON FRIDAY IS FACT THAT ONLY PCPN TIED TO FRONT RIGHT NOW IS OCCURRING ON COLD SIDE OF THE BOUNDARY. SINCE FRONT DOES NOT ARRIVE OVR CWA UNTIL FRI NIGHT RESTRICTED SMALL CHANCES FOR RAIN TO JUST WESTERN LAKE SUPERIOR FRIDAY AFTN. H9-H85 TEMPS SLIGHTLY WARMER THAN TODAY AND CLOUDS NOT INCREASING UNTIL LATE DAY SUGGEST MAX TEMPS AWAY FM LAKE MICHIGAN WILL BE NEAR 50 AGAIN. .LONG TERM (FRI NIGHT THROUGH NEXT THU)... FIRST ITEM OF CONCERN IS THE COLD FRONT FOR FRI NIGHT. NAM SHOWING IT COMING THROUGH THEN BASED ON 1000-500 MB THICKNESS PACKING. THERE IS ALSO SOME 850-500 MB Q-VECTOR CONVERGENCE FOR FRI NIGHT WITH THE COLD FRONT ALONG WITH SOME MOISTURE TO WORK WITH WHICH IS A NARROW RIBBON ACCORDING TO THE NAM. WILL CONTINUE WITH SLIGHT CHANCE TO LOW CHANCE POPS AS THE COLD FRONT COMES THROUGH. NAM SHOWS 850-500 MB Q-VECTOR CONVERGENCE RETURNING SAT NIGHT AND SUN...BUT MOISTURE STAYING TO THE NORTH AND WEST. ECMWF HAS IT DRY...WHILE CANADIAN HAS QPF COMING IN LATE SAT NIGHT. GFS APPEARS TOO FAST AND IS AN OUTLIER AND DID NOT USE. USED THE ECMWF FOR THIS FORECAST AS IT HAS SOME CONTINUITY TO IT WITH SOME HELP FROM THE CANADIAN GLBL GEM. WENT WITH SLIGHT CHANCE POPS ACROSS THE WEST LATE SAT NIGHT AND THEN CHANCE POPS ON SUNDAY. SUNDAY COULD BE WET AND WENT WITH HIGH CHANCE POPS FOR NOW. AS EVENT DRAWS CLOSER...POPS CAN BE INCREASED. TEMPERATURES LOOK TO BE WARM ENOUGH FOR RAIN ON SUNDAY RIGHT NOW WITH RAIN/SNOW FOR SUN NIGHT. DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST FOR TEMPERATURES. IN THE EXTENDED...GFS...ECMWF AND CANADIAN ALL SHOW A NEGATIVELY TILTED 500 MB TROUGH AFFECTING THE AREA 00Z MON. THIS TROUGH THEN CONTINUES TO AFFECT THE AREA THROUGH MON. ANOTHER TROUGH COMES IN FOR 00Z WED AND ALSO BECOMES NEGATIVELY TILTED WITH MORE TROUGHING FOR THU. LOOKS TO BE FAIRLY ACTIVE THIS NEXT WEEK. ONE CONCERN IS WITH STORMS FOR SUN INTO MON...TUE NIGHT INTO WED AND THEN FOR FRI. THE TUE NIGHT AND FRI SYSTEMS HAVE AN OPEN GULF OF MEXICO SOURCE AND SIGNIFICANT DEEP MOISTURE COULD MAKE IT UP HERE. CONCERN IS THAT WITH SNOWPACK ON GROUND COMBINED WITH UP TO 4 INCHES OF ADDITIONAL PCPN POSSIBLE NEXT WEEK WHICH IS WITHIN THE REALM OF POSSIBILITIES...THE SNOWPACK/SNOWMELT COULD BECOME A HYDROLOGY PROBLEM ESPECIALLY IF A BIG WARMUP OCCURS AFTER NEXT WEEK. NO BIG WARMUPS LOOK POSSIBLE FOR NOW. ONLY THING WOULD BE PRIMING THE SNOWPACK/SNOWMELT WITH NEXT WEEKS SYSTEMS. WILL PASS ON TO LATER SHIFTS OF THIS POSSIBILITY AND MENTION IN ESF PRODUCT. TEMPERATURES LOOK TO BE NEAR NORMAL AND DID NOT MAKE TOO MANY CHANGES TO THE GOING TEMPERATURES. PCPN TYPES WILL BE TRICKY...BUT TOO FAR OUT YET TO WORRY ABOUT. WENT RAIN/SNOW MOSTLY FOR THIS EXTENDED FORECAST. WENT CLOSE TO ADJMOS TEMPERATURES. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... MAIN ISSUE REMAINS THE POTENTIAL FOR FOG FORMATION LATE TONIGHT... WHICH REMAINS UNCERTAIN. HIGH BASED CUMULUS CLOUDS OVER THE WESTERN U.P. ARE GRADUALLY DISSIPATING NOW...SO THEY MAY NOT BE AS MUCH OF A CONCERN AS PREVIOUSLY THOUGHT. IN ADDITION...HIGH CLOUDS CROSSING OVER SAWYER SHOULD CONTINUE TO THIN OUT THROUGH THE NIGHT... RESULTING IN A PERIOD OF CLEAR SKIES. WITH LIGHT WINDS... TEMPERATURES SHOULD DROP THROUGH THE DEWPOINTS...BUT THE PROBLEM OF FOG FORMATION MAY BE JUST THE DRY AIRMASS OVER THE AREA AS SEEN ON TAMDAR SOUNDINGS. FOR NOW HAVE FOLLOWED THE PREVIOUS FORECAST WITH VISIBILITIES NOT DROPPING BELOW MVFR AND CIGS STAYING VFR. FOG FORMATION WILL NEED TO BE MONITORED THROUGH THE NIGHT. OTHERWISE... VFR CONDITIONS ARE EXPECTED THROUGH FRI EVENING WITH DRY AIR HOLDING STRONG. A COLD FRONT WILL BE APPROACHING THE AREA...BUT JUST SOME MID CLOUDS ARE EXPECTED AT THIS TIME. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... POTENTIAL FOR WINDS ABOVE 25 KNOTS FRIDAY NIGHT AHEAD OF COLD FRONT AND ALSO ON SATURDAY MORNING IN WAKE OF THE FRONT. A COUPLE OF LOW PRESSURE SYSTEMS LIFTING INTO THE UPPER GREAT LAKES FM THE SOUTHWEST MAY RESULT IN WINDS TO 30 KNOTS SUNDAY INTO TUESDAY. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ UPDATE...AJ SHORT TERM...JLA LONG TERM...GJM AVIATION...AJ MARINE...JLA
AREA FORECAST DISCUSSION
NWS RALEIGH NC
340 AM EDT FRI APR 4 2008 .SYNOPSIS...COOL HIGH PRESSURE OVER THE AREA WILL GIVE WAY TO A COASTAL FRONT PUSHING INLAND THIS MORNING. AS THIS FRONT SHIFTS TO OUR NORTH AS A WARM FRONT... A SOUTHWEST FLOW WILL PUMP WARMER AIR INTO THE AREA. A COLD FRONT WILL MOVE INTO OUR REGION LATE FRIDAY NIGHT... AND PUSH SLOWLY EAST THROUGH THE AREA LATE SATURDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 150 AM FRIDAY... THE PARENT HIGH FOR THIS COLD AIR DAMMING EVENT HAS SHIFTED OFFSHORE AND HAS NO MID LEVEL ANCHORING OR STRENGTHENING SUPPORT... BUT IT HAS LEFT AN IMPRESSIVE RESIDUAL COOL POOL OVER MUCH OF THE CWA. THE MODEL PERFORMANCE OF THIS MESOSCALE FEATURE IS WORRISOME: THE LATEST TEMPS IN THE TRIAD AREA ARE ONLY AROUND 40... AND EVEN THE MOST RECENT MOS GUIDANCE TEMPS THERE FOR THE CURRENT NIGHT ONLY BOTTOM THEM OUT IN THE MID 40S. AMDAR AIRCRAFT SOUNDINGS OVER THE LAST FEW HOURS ARE COLDER THAN GFS/NAM BUFR SOUNDINGS AT THE SURFACE AT BOTH GSO AND RDU. THE COASTAL FRONT HAS WORKED THROUGH THE COASTAL AREA LAST EVENING AND MID 60S ARE COMMON TO ITS EAST... HOWEVER THIS FRONT IS LIKELY TO BE SLOW HEADING INLAND. THE 925-850 MB FLOW TYPICALLY NEEDS TO HAVE A SIGNIFICANT ONSHORE-DIRECTED COMPONENT TO HELP SHOVE THE WEDGE FRONT INLAND... AND SUCH A COMPONENT IS LACKING HERE WITH FLOW IN THIS LAYER HAVING GONE MORE SRLY TO SWRLY. SO IT WILL LIKELY TAKE INSOLATION ATOP THE COOL STABLE DOME TO ERODE THE WEDGE REGIME... RESULTING IN SLOW DRAINING OF THE WEDGE AND A GRADUAL EROSION FROM THE EDGES. EROSION COULD BE DELAYED FURTHER IF THE WARM ADVECTION NEAR THE TOP OF THE INVERSION SERVES TO STRENGTHEN THE STABILITY BY INCREASING THE VERTICAL TEMP DIFFERENTIAL. THE NET RESULT WILL BE A SLOWING OF THE WARMING IN THE PIEDMONT TODAY FROM THE CURRENT FORECAST... ESPECIALLY IN THE PIEDMONT. EXPECT HIGHS OF 65-78 NW-SE... WITH HIGHS OCCURRING VERY LATE IN THE PIEDMONT. REGARDING PRECIP... ISENTROPIC UPGLIDE AROUND 285-300K HAS WANED CONSIDERABLY AND THE MEAN FLOW IS NOW ORIENTED ROUGHLY PARALLEL TO THE ISENTROPES. OTHER LIFT MECHANISMS ARE WEAK TO NONEXISTENT MUCH OF TODAY ACCORDING TO LATEST MODEL GUIDANCE... WITH A GENERALLY FLAT SWRLY MID LEVEL FLOW WITH NO DISCERNIBLE PERTURBATIONS AND UPPER JET FORCING HOLDING TO OUR WEST UNTIL AFTER SUNDOWN. LOW LEVEL MOISTURE FLUX CONVERGENCE DOES IMPROVE TODAY BUT IS FOCUSED MAINLY OVER EASTERN NC. THE LATEST WRF-ARW DEPICTS MINIMAL PATCHY RAIN THROUGH THE DAY CWA-WIDE... A TREND NOTED ON THE NAM/GFS AS WELL. HAVE REDUCED POPS THROUGH EARLY EVENING TO A 30-50% CHANCE... LOWER THIS MORNING TRENDING HIGHER LATE IN THE DAY. HAVE KEPT IN A CHANCE OF THUNDER EVERYWHERE WITH INCREASING LOW LEVEL THETA-E... LOW LEVEL JETTING INCREASING TO 40-50 KTS AT 850 MB... AND MUCAPE OF 800-1000 J/KG LATE THIS AFTERNOON OVER THE FAR SOUTHERN CWA... HOWEVER IF THE LOW LEVEL STABLE POOL HOLDS ON MUCH LONGER THAN THE MODELS INDICATE... SIGNIFICANT BUOYANCY MAY BE TOUGHER TO COME BY. -GIH && .SHORT TERM /TONIGHT THROUGH SUNDAY/... AS OF 300 AM FRIDAY... FOR TONIGHT: THE COLD FRONT IS EXPECTED TO SLOWLY EASE EASTWARD TOWARD THE WRN MOUNTAINS SLOPES. CONVECTIVE CHANCES APPEAR TO PEAK NEAR AND JUST AFTER SUNSET... DURING THE EARLY-MID EVENING... WITH MUCAPES REACHING CLOSE TO 1000 J/KG... INCREASING UPPER DIVERGENCE... AND CURVED HODOGRAPHS WITH 850 MB WINDS REACHING 40-50 KTS AROUND 00-06Z. WILL INCLUDE SCATTERED STORMS THROUGH THE EVENING... TAPERING TO MAINLY SHOWERS OVERNIGHT WITH THE HIGHER CATEGORICAL POPS IN THE WEST CLOSER TO THE ENCROACHING COLD FRONT AND LOWER CHANCES EAST. THE THREAT OF SOME MODERATE TO HEAVY RAIN APPEARS TO RISE OVERNIGHT AS FACTORS FAVORING WARM RAIN PROCESSES IMPROVE... INCLUDING A DEEPENING LCL-TO- FREEZING-LEVEL TO 3.5 KM AND PRECIPITABLE WATER INCREASING TO 250% OF NORMAL. EXPECT LOWS TONIGHT TO RUN 59-66... WELL ABOVE MOS GUIDANCE LOWS WHICH ARE TYPICALLY A LITTLE TOO COOL JUST AHEAD OF COLD FRONTS. A GREATER RISK OF HEAVY RAIN WILL BE ON SATURDAY AS THE WAVY FRONT PUSHES SLOWLY EAST THROUGH THE AREA. THE SLOWER FRONTAL MOVEMENT OF THE ECWMF IS PREFERRED... GIVEN THAT THE MID LEVEL FLOW BECOMES NEARLY PARALLEL TO THE SURFACE FRONT WITH NO STRONG PUSH OF COLD AIR OVER THE MOUNTAINS UNTIL AFTER DARK WHEN THE MID LEVEL SHORTWAVE TROUGH NOW DIVING INTO THE WESTERN PLAINS FINALLY PUSHES INTO THE CENTRAL/SRN APPALACHIANS. PRECIPITABLE WATER VALUES NEARLY 300% OF NORMAL AND POSSIBLE TRAINING CELLS OR BANDS COULD PUSH LOCAL RAIN TOTALS TO 1-2 INCHES. THE OPERATIONAL MODELS HAVE NOT DONE WELL PREDICTING PRECIP AMOUNTS IN RECENT WEEKS... SO CONFIDENCE IN PRECISE PLACEMENT OF THE HEAVY RAIN RISK IS NOT HIGH. DESPITE THE DROUGHT WE`RE STILL IN... SOILS HAVE MOISTENED A BIT WITH THE LAST COUPLE OF RAIN EVENTS... AND MANY AREAS WITH STILL-HARDENED GROUND COULD SEE RAPID RUNOFF INTO CREEKS AND POOR DRAINAGE AREAS. WILL INCLUDE THIS THREAT IN THE HAZARDOUS WEATHER OUTLOOK. REGARDING THE SEVERE RISK... A SLUG OF UPPER DIVERGENCE WITHIN THE RIGHT ENTRANCE REGION OF THE JET WILL ACCOMPANY DECENT 700-500 MB LAPSE RATES NEAR 6.5 C/KM AND MODERATE MID LEVEL HEIGHT FALLS... AND IF THE COLD FRONT IS INDEED DELAYED LIKE THE ECMWF DEPICTS OVER THE FASTER GFS AND ESPECIALLY NAM... THE LOW LEVELS WILL BE MORE UNSTABLE THAN NAM/GFS FORECAST SOUNDINGS DEPICT. THIS SHORTWAVE DOES DAMPEN QUITE A BIT AS IT ENCOUNTERS THE ATLANTIC RIDGE HOWEVER AND MAY NOT CONTRIBUTE MUCH TO BROAD LIFT. WIND FIELDS LOOK GOOD WITH NEARLY 50 KTS OF 0-6 KM SHEAR AHEAD OF THE FRONT ALTHOUGH THE LOW LEVEL JET CORE WILL BE SHIFTING INTO THE COASTAL SECTIONS. THE PRIMARY THREAT STILL APPEARS TO BE FROM STRAIGHT LINE DAMAGING WINDS ESPECIALLY EAST OF HIGHWAY 1 WHERE THE NAM GIVES A MUCAPE OF 1000-1500 J/KG. EXISTING HIGHS OF 68-76 STILL LOOK REASONABLE WITH STRONG WARM ADVECTION AHEAD OF THE FRONT. AS THE FRONT SHIFTS EASTWARD SATURDAY NIGHT AS INDICATED BY THE PREFERRED ECMWF... SHOWER/STORM CHANCES WILL DIMINISH FROM WEST TO EAST BUT SIGNIFICANT CLEARING WILL LIKELY HOLD OFF UNTIL SUNDAY. LOWS SATURDAY NIGHT 46-55. THE SURFACE RIDGE THAT WILL BECOME CENTERED OVER EASTERN CANADA WILL RIDGE NARROWLY SOUTHWARD DOWN THROUGH THE PIEDMONT SUNDAY... AND THIS SHOULD KEEP ENOUGH ATLANTIC MOISTURE PUMPING ACROSS THE VA/NC COAST FOR VARIABLE CLOUD COVER EAST/PARTLY CLOUDY WEST THROUGH SUNDAY. EXPECT BELOW NORMAL HIGHS SUNDAY OF 60-68... COOLER NORTHEAST... WITH PERIODS OF CLOUDS AND WITH THICKNESSES STARTING NEAR NORMAL BUT LIKELY TO HOLD STEADY OR FALL THROUGH THE DAY. -GIH && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 340 AM FRIDAY... THIS APPEARS TO BE A RELATIVELY QUIET WEATHER PERIOD. A MID LEVEL VORTEX TRACKING NE THROUGH THE NRN GREAT LAKES ON MONDAY SERVES TO BUILD UP MID LEVEL RIDGING ATOP THE SURFACE RIDGE EXTENDING FROM FAR ERN CANADA DOWN THROUGH THE CAROLINAS. THE NARROW NOSE OF COOLER TEMPERATURES SHOULD PERSIST OVER THE CWA MONDAY YIELDING BELOW NORMAL HIGHS IN THE LOW-MID 60S. ABUNDANT BOUNDARY LAYER MOISTURE WITH A LINGERING FLUX OF ATLANTIC MOISTURE SHOULD KEEP SKIES PARTLY TO MOSTLY CLOUDY THROUGH TUESDAY... AND WHILE BRIEF PERIODS OF ISENTROPIC UPGLIDE ARE POSSIBLE... THE LACK OF OTHER LIFT MECHANISMS AND THE UNCERTAINTY OF THE DEGREE OF FORCING PROVIDED BY ANY SUCH LIFT PRECLUDES INCLUDING A POP THROUGH TUESDAY. ANOTHER MID LEVEL VORTEX TRACKS NE THROUGH THE GREAT LAKES WEDNESDAY/WEDNESDAY NIGHT RESULTING IN BUILDING RIDGING OVER THE SOUTHEAST. WILL CONTINUE WITH MODIFYING TEMPERATURES SURPASSING NORMALS BY 1-2 CATEGORIES BY THURSDAY AS THICKNESSES REACH 20-30 M ABOVE NORMAL. -GIH && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 225 AM FRIDAY... WARM... MOIST FLOW OVERRUNNING COOL... NORTH TO NORTHEAST FLOW AT THE SURFACE WILL RESULT IN LIFR CONDITIONS IN LOW CLOUDS...LIGHT RAIN... DRIZZLE AND FOG EARLY THIS FRIDAY MORNING. CONDITIONS WILL GRADUALLY IMPROVE FROM THE EAST DURING THE LATE MORNING TO EARLY AFTERNOON AS A WARM FRONT WORKS WESTWARD FROM THE COAST. CONDITIONS WILL LIFT TO MVFR RWI...RDU...FAY BETWEEN 15 AND 17Z AND OVER GSO AND INT AFTER 18Z. AS THE ATMOSPHERE MIXES... AFTERNOON HEATING WILL COMBINE WITH WARM... SOUTHERLY FLOW TO GIVE A CHANCE OF SHOWERS AND THUNDERSTORMS LATE TODAY AND TONIGHT. A COLD FRONT WILL APPROACH AND MOVE ACROSS THE REGION SATURDAY. WE CAN EXPECT MVFR TO IFR CONDITIONS IN SHOWERS AND SCATTERED THUNDERSTORMS. THE COLD FRONT WILL LINGER ALONG THE COAST LATE SATURDAY THROUGH EARLY SUNDAY... RESULTING IN AS SLOW IMPROVEMENT OVER THE EASTERN TAFS THROUGH THE NIGHT. HIGH PRESSURE WILL BUILD OVER THE AREA DURING THE DAY SUNDAY AND REMAIN THROUGH TUESDAY. WE CAN EXPECT VFR CONDITIONS AS DRY AIR TAKES HOLD OF THE REGION. -RHJ && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...RHJ
AREA FORECAST DISCUSSION
NWS RALEIGH NC
305 AM EDT FRI APR 4 2008 .SYNOPSIS...COOL HIGH PRESSURE OVER THE AREA WILL GIVE WAY TO A COASTAL FRONT PUSHING INLAND THIS MORNING. AS THIS FRONT SHIFTS TO OUR NORTH AS A WARM FRONT... A SOUTHWEST FLOW WILL PUMP WARMER AIR INTO THE AREA. A COLD FRONT WILL MOVE INTO OUR REGION LATE FRIDAY NIGHT... AND PUSH SLOWLY EAST THROUGH THE AREA LATE SATURDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 150 AM FRIDAY... THE PARENT HIGH FOR THIS COLD AIR DAMMING EVENT HAS SHIFTED OFFSHORE AND HAS NO MID LEVEL ANCHORING OR STRENGTHENING SUPPORT... BUT IT HAS LEFT AN IMPRESSIVE RESIDUAL COOL POOL OVER MUCH OF THE CWA. THE MODEL PERFORMANCE OF THIS MESOSCALE FEATURE IS WORRISOME: THE LATEST TEMPS IN THE TRIAD AREA ARE ONLY AROUND 40... AND EVEN THE MOST RECENT MOS GUIDANCE TEMPS THERE FOR THE CURRENT NIGHT ONLY BOTTOM THEM OUT IN THE MID 40S. AMDAR AIRCRAFT SOUNDINGS OVER THE LAST FEW HOURS ARE COLDER THAN GFS/NAM BUFR SOUNDINGS AT THE SURFACE AT BOTH GSO AND RDU. THE COASTAL FRONT HAS WORKED THROUGH THE COASTAL AREA LAST EVENING AND MID 60S ARE COMMON TO ITS EAST... HOWEVER THIS FRONT IS LIKELY TO BE SLOW HEADING INLAND. THE 925-850 MB FLOW TYPICALLY NEEDS TO HAVE A SIGNIFICANT ONSHORE-DIRECTED COMPONENT TO HELP SHOVE THE WEDGE FRONT INLAND... AND SUCH A COMPONENT IS LACKING HERE WITH FLOW IN THIS LAYER HAVING GONE MORE SRLY TO SWRLY. SO IT WILL LIKELY TAKE INSOLATION ATOP THE COOL STABLE DOME TO ERODE THE WEDGE REGIME... RESULTING IN SLOW DRAINING OF THE WEDGE AND A GRADUAL EROSION FROM THE EDGES. EROSION COULD BE DELAYED FURTHER IF THE WARM ADVECTION NEAR THE TOP OF THE INVERSION SERVES TO STRENGTHEN THE STABILITY BY INCREASING THE VERTICAL TEMP DIFFERENTIAL. THE NET RESULT WILL BE A SLOWING OF THE WARMING IN THE PIEDMONT TODAY FROM THE CURRENT FORECAST... ESPECIALLY IN THE PIEDMONT. EXPECT HIGHS OF 65-78 NW-SE... WITH HIGHS OCCURRING VERY LATE IN THE PIEDMONT. REGARDING PRECIP... ISENTROPIC UPGLIDE AROUND 285-300K HAS WANED CONSIDERABLY AND THE MEAN FLOW IS NOW ORIENTED ROUGHLY PARALLEL TO THE ISENTROPES. OTHER LIFT MECHANISMS ARE WEAK TO NONEXISTENT MUCH OF TODAY ACCORDING TO LATEST MODEL GUIDANCE... WITH A GENERALLY FLAT SWRLY MID LEVEL FLOW WITH NO DISCERNIBLE PERTURBATIONS AND UPPER JET FORCING HOLDING TO OUR WEST UNTIL AFTER SUNDOWN. LOW LEVEL MOISTURE FLUX CONVERGENCE DOES IMPROVE TODAY BUT IS FOCUSED MAINLY OVER EASTERN NC. THE LATEST WRF-ARW DEPICTS MINIMAL PATCHY RAIN THROUGH THE DAY CWA-WIDE... A TREND NOTED ON THE NAM/GFS AS WELL. HAVE REDUCED POPS THROUGH EARLY EVENING TO A 30-50% CHANCE... LOWER THIS MORNING TRENDING HIGHER LATE IN THE DAY. HAVE KEPT IN A CHANCE OF THUNDER EVERYWHERE WITH INCREASING LOW LEVEL THETA-E... LOW LEVEL JETTING INCREASING TO 40-50 KTS AT 850 MB... AND MUCAPE OF 800-1000 J/KG LATE THIS AFTERNOON OVER THE FAR SOUTHERN CWA... HOWEVER IF THE LOW LEVEL STABLE POOL HOLDS ON MUCH LONGER THAN THE MODELS INDICATE... SIGNIFICANT BUOYANCY MAY BE TOUGHER TO COME BY. -GIH && .SHORT TERM /TONIGHT THROUGH SUNDAY/... AS OF 300 AM FRIDAY... FOR TONIGHT: THE COLD FRONT IS EXPECTED TO SLOWLY EASE EASTWARD TOWARD THE WRN MOUNTAINS SLOPES. CONVECTIVE CHANCES APPEAR TO PEAK NEAR AND JUST AFTER SUNSET... DURING THE EARLY-MID EVENING... WITH MUCAPES REACHING CLOSE TO 1000 J/KG... INCREASING UPPER DIVERGENCE... AND CURVED HODOGRAPHS WITH 850 MB WINDS REACHING 40-50 KTS AROUND 00-06Z. WILL INCLUDE SCATTERED STORMS THROUGH THE EVENING... TAPERING TO MAINLY SHOWERS OVERNIGHT WITH THE HIGHER CATEGORICAL POPS IN THE WEST CLOSER TO THE ENCROACHING COLD FRONT AND LOWER CHANCES EAST. THE THREAT OF SOME MODERATE TO HEAVY RAIN APPEARS TO RISE OVERNIGHT AS FACTORS FAVORING WARM RAIN PROCESSES IMPROVE... INCLUDING A DEEPENING LCL-TO- FREEZING-LEVEL TO 3.5 KM AND PRECIPITABLE WATER INCREASING TO 250% OF NORMAL. EXPECT LOWS TONIGHT TO RUN ABOVE MOS GUIDANCE LOWS WHICH ARE TYPICALLY A LITTLE TOO COOL JUST AHEAD OF COLD FRONTS. A GREATER RISK OF HEAVY RAIN WILL BE ON SATURDAY AS THE WAVY FRONT PUSHES SLOWLY EAST THROUGH THE AREA. THE SLOWER FRONTAL MOVEMENT OF THE ECWMF IS PREFERRED... GIVEN THAT THE MID LEVEL FLOW BECOMES NEARLY PARALLEL TO THE SURFACE FRONT WITH NO STRONG PUSH OF COLD AIR OVER THE MOUNTAINS UNTIL AFTER DARK WHEN THE MID LEVEL SHORTWAVE TROUGH NOW DIVING INTO THE WESTERN PLAINS FINALLY PUSHES INTO THE CENTRAL/SRN APPALACHIANS. PRECIPITABLE WATER VALUES NEARLY 300% OF NORMAL AND POSSIBLE TRAINING CELLS OR BANDS COULD PUSH LOCAL RAIN TOTALS TO 1-2 INCHES. THE OPERATIONAL MODELS HAVE NOT DONE WELL PREDICTING PRECIP AMOUNTS IN RECENT WEEKS... SO CONFIDENCE IN PRECISE PLACEMENT OF THE HEAVY RAIN RISK IS NOT HIGH. DESPITE THE DROUGHT WE`RE STILL IN... SOILS HAVE MOISTENED A BIT WITH THE LAST COUPLE OF RAIN EVENTS... AND MANY AREAS WITH STILL-HARDENED GROUND COULD SEE RAPID RUNOFF INTO CREEKS AND POOR DRAINAGE AREAS. WILL INCLUDE THIS THREAT IN THE HAZARDOUS WEATHER OUTLOOK. REGARDING THE SEVERE RISK... A SLUG OF UPPER DIVERGENCE WITHIN THE RIGHT ENTRANCE REGION OF THE JET WILL ACCOMPANY DECENT 700-500 MB LAPSE RATES NEAR 6.5 C/KM AND MODERATE MID LEVEL HEIGHT FALLS... AND IF THE COLD FRONT IS INDEED DELAYED LIKE THE ECMWF DEPICTS OVER THE FASTER GFS AND ESPECIALLY NAM... THE LOW LEVELS WILL BE MORE UNSTABLE THAN NAM/GFS FORECAST SOUNDINGS DEPICT. THIS SHORTWAVE DOES DAMPEN QUITE A BIT AS IT ENCOUNTERS THE ATLANTIC RIDGE HOWEVER AND MAY NOT CONTRIBUTE MUCH TO BROAD LIFT. WIND FIELDS LOOK GOOD WITH NEARLY 50 KTS OF 0-6 KM SHEAR AHEAD OF THE FRONT ALTHOUGH THE LOW LEVEL JET CORE WILL BE SHIFTING INTO THE COASTAL SECTIONS. THE PRIMARY THREAT STILL APPEARS TO BE FROM STRAIGHT LINE DAMAGING WINDS ESPECIALLY EAST OF HIGHWAY 1 WHERE THE NAM GIVES A MUCAPE OF 1000-1500 J/KG. EXISTING HIGHS OF 68-76 STILL LOOK REASONABLE WITH STRONG WARM ADVECTION AHEAD OF THE FRONT. AS THE FRONT SHIFTS EASTWARD SATURDAY NIGHT AS INDICATED BY THE PREFERRED ECMWF... SHOWER/STORM CHANCES WILL DIMINISH FROM WEST TO EAST BUT SIGNIFICANT CLEARING WILL LIKELY HOLD OFF UNTIL SUNDAY. THE SURFACE RIDGE THAT WILL BECOME CENTERED OVER EASTERN CANADA WILL RIDGE NARROWLY SOUTHWARD DOWN THROUGH THE PIEDMONT SUNDAY... AND THIS SHOULD KEEP ENOUGH ATLANTIC MOISTURE PUMPING ACROSS THE VA/NC COAST FOR VARIABLE CLOUD COVER EAST/PARTLY CLOUDY WEST THROUGH SUNDAY. EXPECT BELOW NORMAL HIGHS SUNDAY WITH PERIODS OF CLOUDS AND WITH THICKNESSES STARTING NEAR NORMAL BUT LIKELY TO HOLD STEADY OR FALL THROUGH THE DAY. -GIH && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 245 PM... HIGH PRESSURE NOSES SOUTH FROM VIRGINIA INTO OUR AREA BEHIND THE SATURDAY FRONT. RETURN FLOW DOES NOT BECOME EAST TO SOUTHEAST UNTIL AT LEAST WEDNESDAY... AND FLOW EVEN THEN IS WEAK. THUS WILL KEEP THIS PERIOD DRY. SOME MODELS ATTEMPT TO DEVELOP A COASTAL LOW LATE IN THE PERIOD. THIS IS BY NO MEANS CERTAIN AND SUCH DEVELOPMENT AS MIGHT OCCUR APPEARS TO BE FAR ENOUGH EAST TO LEAVE CENTRAL NORTH CAROLINA DRY. AFTERNOON TEMPERATURES GENERALLY MID 60S TO LOWER 70S. MORNING LOWS 45 TO 55. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 225 AM FRIDAY... WARM... MOIST FLOW OVERRUNNING COOL... NORTH TO NORTHEAST FLOW AT THE SURFACE WILL RESULT IN LIFR CONDITIONS IN LOW CLOUDS...LIGHT RAIN... DRIZZLE AND FOG EARLY THIS FRIDAY MORNING. CONDITIONS WILL GRADUALLY IMPROVE FROM THE EAST DURING THE LATE MORNING TO EARLY AFTERNOON AS A WARM FRONT WORKS WESTWARD FROM THE COAST. CONDITIONS WILL LIFT TO MVFR RWI...RDU...FAY BETWEEN 15 AND 17Z AND OVER GSO AND INT AFTER 18Z. AS THE ATMOSPHERE MIXES... AFTERNOON HEATING WILL COMBINE WITH WARM... SOUTHERLY FLOW TO GIVE A CHANCE OF SHOWERS AND THUNDERSTORMS LATE TODAY AND TONIGHT. A COLD FRONT WILL APPROACH AND MOVE ACROSS THE REGION SATURDAY. WE CAN EXPECT MVFR TO IFR CONDITIONS IN SHOWERS AND SCATTERED THUNDERSTORMS. THE COLD FRONT WILL LINGER ALONG THE COAST LATE SATURDAY THROUGH EARLY SUNDAY... RESULTING IN AS SLOW IMPROVEMENT OVER THE EASTERN TAFS THROUGH THE NIGHT. HIGH PRESSURE WILL BUILD OVER THE AREA DURING THE DAY SUNDAY AND REMAIN THROUGH TUESDAY. WE CAN EXPECT VFR CONDITIONS AS DRY AIR TAKES HOLD OF THE REGION. -RHJ && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...HARTFIELD LONG TERM...RLH AVIATION...RHJ
AREA FORECAST DISCUSSION
NWS RALEIGH NC
150 AM EDT FRI APR 4 2008 .SYNOPSIS...COOL HIGH PRESSURE OVER THE AREA WILL GIVE WAY TO A COASTAL FRONT PUSHING INLAND THIS MORNING. AS THIS FRONT SHIFTS TO OUR NORTH AS A WARM FRONT... A SOUTHWEST FLOW WILL PUMP WARMER AIR INTO THE AREA. A COLD FRONT WILL MOVE INTO OUR REGION LATE FRIDAY NIGHT... AND PUSH SLOWLY EAST THROUGH THE AREA LATE SATURDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 150 AM FRIDAY... THE PARENT HIGH FOR THIS COLD AIR DAMMING EVENT HAS SHIFTED OFFSHORE AND HAS NO MID LEVEL ANCHORING OR STRENGTHENING SUPPORT... BUT IT HAS LEFT AN IMPRESSIVE RESIDUAL COOL POOL OVER MUCH OF THE CWA. THE MODEL PERFORMANCE OF THIS MESOSCALE FEATURE IS WORRISOME: THE LATEST TEMPS IN THE TRIAD AREA ARE ONLY AROUND 40... AND EVEN THE MOST RECENT MOS GUIDANCE TEMPS THERE FOR THE CURRENT NIGHT ONLY BOTTOM THEM OUT IN THE MID 40S. AMDAR AIRCRAFT SOUNDINGS OVER THE LAST FEW HOURS ARE COLDER THAN GFS/NAM BUFR SOUNDINGS AT THE SURFACE AT BOTH GSO AND RDU. THE COASTAL FRONT HAS WORKED THROUGH THE COASTAL AREA LAST EVENING AND MID 60S ARE COMMON TO ITS EAST... HOWEVER THIS FRONT IS LIKELY TO BE SLOW HEADING INLAND. THE 925-850 MB FLOW TYPICALLY NEEDS TO HAVE A SIGNIFICANT ONSHORE-DIRECTED COMPONENT TO HELP SHOVE THE WEDGE FRONT INLAND... AND SUCH A COMPONENT IS LACKING HERE WITH FLOW IN THIS LAYER HAVING GONE MORE SRLY TO SWRLY. SO IT WILL LIKELY TAKE INSOLATION ATOP THE COOL STABLE DOME TO ERODE THE WEDGE REGIME... RESULTING IN SLOW DRAINING OF THE WEDGE AND A GRADUAL EROSION FROM THE EDGES. EROSION COULD BE DELAYED FURTHER IF THE WARM ADVECTION NEAR THE TOP OF THE INVERSION SERVES TO STRENGTHEN THE STABILITY BY INCREASING THE VERTICAL TEMP DIFFERENTIAL. THE NET RESULT WILL BE A SLOWING OF THE WARMING IN THE PIEDMONT TODAY FROM THE CURRENT FORECAST... ESPECIALLY IN THE PIEDMONT. EXPECT HIGHS OF 65-78 NW-SE... WITH HIGHS OCCURRING VERY LATE IN THE PIEDMONT. REGARDING PRECIP... ISENTROPIC UPGLIDE AROUND 285-300K HAS WANED CONSIDERABLY AND THE MEAN FLOW IS NOW ORIENTED ROUGHLY PARALLEL TO THE ISENTROPES. OTHER LIFT MECHANISMS ARE WEAK TO NONEXISTENT MUCH OF TODAY ACCORDING TO LATEST MODEL GUIDANCE... WITH A GENERALLY FLAT SWRLY MID LEVEL FLOW WITH NO DISCERNIBLE PERTURBATIONS AND UPPER JET FORCING HOLDING TO OUR WEST UNTIL AFTER SUNDOWN. LOW LEVEL MOISTURE FLUX CONVERGENCE DOES IMPROVE TODAY BUT IS FOCUSED MAINLY OVER EASTERN NC. THE LATEST WRF-ARW DEPICTS MINIMAL PATCHY RAIN THROUGH THE DAY CWA-WIDE... A TREND NOTED ON THE NAM/GFS AS WELL. HAVE REDUCED POPS THROUGH EARLY EVENING TO A 30-50% CHANCE... LOWER THIS MORNING TRENDING HIGHER LATE IN THE DAY. HAVE KEPT IN A CHANCE OF THUNDER EVERYWHERE WITH INCREASING LOW LEVEL THETA-E... LOW LEVEL JETTING INCREASING TO 40-50 KTS AT 850 MB... AND MUCAPE OF 800-1000 J/KG LATE THIS AFTERNOON OVER THE FAR SOUTHERN CWA... HOWEVER IF THE LOW LEVEL STABLE POOL HOLDS ON MUCH LONGER THAN THE MODELS INDICATE... SIGNIFICANT BUOYANCY MAY BE TOUGHER TO COME BY. -GIH && .SHORT TERM /TONIGHT THROUGH SUNDAY/... AS OF 245 PM... THIRTY TO FORTY-FIVE KNOT SOUTHWEST WINDS AT 850 MILLIBARS WILL KEEP GULF MOISTURE PUMPING INTO NORTH CAROLINA INTO SATURDAY. THERE ARE NO SIGNIFICANT DYNAMICS FRIDAY. HOWEVER MODELS INDICATE THE ATMOSPHERE BECOMING UNSTABLE ENOUGH TO HAVE SCATTERED SHOWERS BREAK OUT WITH THE HEATING OF THE DAY. EXPECT ENOUGH CLOUDS TO INHIBIT FULL SUN HIGH TEMPERATURES AND SET HIGHS AT 70 TO 76 FRIDAY. SIMILAR TEMPERATURES SATURDAY. GUSTY SOUTHWEST WINDS FORECAST FOR FRIDAY WILL DIMINISH ONLY SLIGHTLY IN THE HOURS AFTER MIDNIGHT FRIDAY NIGHT. APPROACHING FRONT SHOULD BE CLOSE ENOUGH TO BRING SHOWERS TO THE WESTERN PIEDMONT BEFORE SUNRISE SATURDAY WITH PERHAPS SOME PATCHY RAIN EAST. FRONT MOVES THROUGH CENTRAL NORTH CAROLINA SATURDAY. AVAILABLE ENERGY IN THE AIR COLUMN IS PAPER THIN AND LESS THAN 1000 J/KG SOUTHWEST WINDS IN EXCESS OF 50 KNOTS DEVELOP BELOW 5000 FEET. FREEZING LEVEL SEEMS TO STAY ABOVE 11000 FEET. ANY SEVERE THREAT WOULD SEEM TO BE MAINLY WIND AND NOT VERY EXTENSIVE. THIS APPEARS TO BE A VERY SIGNIFICANT RAINFALL EVENT. HAVE FORECAST AROUND ONE INCH...WITH LOCALLY HEAVIER AMOUNTS. THE NORTHWEST AND NORTH MAY BE SLIGHTLY FAVORED OVER THE SOUTHEAST. CURRENT MODEL TIMING SUGGESTS ANY SIGNIFICANT RAINS ENDING IN THE NORTHWEST SATURDAY EVENING... AND BEFORE MIDNIGHT FURTHER EAST. OVERNIGHT LOWS 59 TO 63 FRIDAY NIGHT... AND UPPER 40S TO MID 50S SATURDAY NIGHT. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 245 PM... HIGH PRESSURE NOSES SOUTH FROM VIRGINIA INTO OUR AREA BEHIND THE SATURDAY FRONT. RETURN FLOW DOES NOT BECOME EAST TO SOUTHEAST UNTIL AT LEAST WEDNESDAY... AND FLOW EVEN THEN IS WEAK. THUS WILL KEEP THIS PERIOD DRY. SOME MODELS ATTEMPT TO DEVELOP A COASTAL LOW LATE IN THE PERIOD. THIS IS BY NO MEANS CERTAIN AND SUCH DEVELOPMENT AS MIGHT OCCUR APPEARS TO BE FAR ENOUGH EAST TO LEAVE CENTRAL NORTH CAROLINA DRY. AFTERNOON TEMPERATURES GENERALLY MID 60S TO LOWER 70S. MORNING LOWS 45 TO 55. && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 745 PM THU... AN APPROACHING WARM FRONT FROM THE SOUTH AND ASSOCIATED MOIST FLOW WILL OVERRIDE COOLER AIR AT THE SURFACE LEADING TO WIDESPREAD IFR AND LIFR CONDITIONS IN STRATUS...RAIN...DRIZZLE AND FOG OVERNIGHT. RAIN WILL DIMINISH BEFORE DAYBREAK...BUT IFR/LIFR CONDITIONS WILL BE SLOW TO IMPROVE AS THE WARM FRONT MOVES NORTHWEST ACROSS CENTRAL NC FRI MORNING AND MIDDAY. CONDITIONS WILL LIFT TO MVFR AT KFAY AND KRWI BY 15Z...KRDU BY 17Z...AND KGSO AND KINT BY 20Z. WITH HEATING IN THE AFTERNOON AND MOIST SWLY FLOW...SCATTERED SHOWERS AND ISOLATED TSTMS ARE EXPECTED LATE FRI INTO FRI NIGHT. FRI NIGHT AND SAT...A COLD FRONT WILL APPROACH FROM THE WEST AND SLOWLY CROSS CENTRAL NC SAT MIDDAY AND AFTERNOON. NUMEROUS SHOWERS AND SCATTERED TSTMS ARE EXPECTED WITH FQT MVFR AND POSSIBLE IFR CONDITIONS. SAT NIGHT THROUGH TUE...THE COLD FRONT WILL EXIT THE AREA SAT NIGHT BUT LOW PRESSURE ALONG THE COAST AND A SHALLOW COOL MOIST AIRMASS IN THE WAKE OF THE LOW MAY KEEP MVFR AND IFR CIGS AND VSBY OVER CENTRAL NC THROUGH DAYBREAK SUN...IMPROVING TO VFR DURING THE DAY. HIGH PRESSURE SHOULD STRENGTHEN ALONG THE EAST COAST LATE SUN THROUGH TUE MAINTAINING A DRY AIRMASS OVER THE REGION AND VFR CONDITIONS OVER CENTRAL NC DURING THE PERIOD. -RFG && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...RLH LONG TERM...RLH AVIATION...RFG
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
952 AM EDT FRI APR 4 2008 .SYNOPSIS... A SERIES OF LOW PRESSURE SYSTEMS WILL TRACK ACROSS THE REGION TODAY THROUGH SATURDAY ENHANCING PRECIPITATION CHANCES. GENERALLY ONE TO THREE INCHES OF RAIN CAN BE EXPECTED BY SATURDAY EVENING. HIGH PRESSURE WILL BUILD IN FOR SUNDAY AND HOLD THROUGH THE MIDDLE OF NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... WATER VAPOR LOOP SHOWS A POSITIVELY TILTED TROUGH CROSSING THE CENTRAL CONUS...WITH DEEP LAYER MOISTURE ADVECTING FROM THE WESTERN GULF OF MEXICO NORTHEAST INTO THE CENTRAL APPALACHIANS. ACARS 400-250MB WIND OBSERVATIONS SHOW A 125-165KT ANTICYCLONICALLY CURVED JET FROM THE MIDDLE MISSISSIPPI RIVER VALLEY THROUGH THE EASTERN GREAT LAKES AND NEW ENGLAND. 11Z SURFACE ANALYSIS PLACE A 1005MB CYCLONE NEAR INDIANAPOLIS. A WARM/STATIONARY BOUNDARY SNAKED SOUTHEAST TO THE APPALACHIANS...THEN ALONG THE MOUNTAINS TO ATLANTA...BEFORE CURVING EAST TO THE ATLANTIC COAST AND PARALLELING THE COAST NORTH TO THE DELMARVA. THE COLD FRONT STRETCHED SOUTHWEST BISECTING ARKANSAS AND TEXAS. A 1020MB ANTICYCLONE DOMINATES THE PLAINS. POSITIONING OF THE UPPER LEVEL JET AXIS SUPPORTS BEST CHANCES OF RAIN ACROSS WESTERN AND NORTHERN FORECAST AREA...WITH METRO AREAS SERVING AS A TRANSITION ZONE TO DRIER CONDITIONS TO THE SOUTHEAST. INTERMITTENT LIGHTNING WITHIN WARM SECTOR ACROSS OHIO VALLEY IS FORECAST TO CONTINUE TO DIMINISH OVER THE MOUNTAINS FURTHER REMOVED FROM INSTABILITY. 1235Z KIAD ASCENT ACARS SOUNDING SHOWS COOL POOL IS ABOUT 1KFT THICK...WITH +14C AT 881MB. EXPECT A FEW BREAKS TO DEVELOP ACROSS HIGHER TERRAIN OF SOUTHWEST ZONES...WHERE MIXING COULD TAKE TEMPERATURES WELL INTO THE 60S. FURTHER NORTH ALONG THE PENNSYLVANIA BORDER...THINK DAMMING WILL REMAIN TOUGHEST AND HAVE DECREASED TEMPERATURES BELOW GUIDANCE. IN BETWEEN...INCLUDING THE GREATER BALTIMORE/WASHINGTON METRO AREAS...IS THE TOUGHEST AREA TO FORECAST...SIDING WITH A RELATIVELY SMOOTH TRANSITION. IN REALITY...A BREAK TO EITHER SCENARIO WOULD BE MORE EXTREME WITH TEMPERATURES COOLER OR WARMER THAN CURRENTLY FORECAST. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... NEXT WAVE OVER INDIANA WILL TRACK ACROSS SRN PA THIS EVENING PUSHING A CDFNT THRU THE AREA TONIGHT. ADDITIONAL WAVES OF LOW PRES ARE EXPECTED TO RIDE ALG THE FRONT ENHANCING CHANCES OF PRECIPITATION. AXIS OF HEAVIEST RAINFALL EXPECTED ACROSS THE SRN HALF OF THE FCST AREA. CHANCE FOR TSTMS ONLY SRN MD AND THE NRN PIEDMONT OF VA PER NEGATIVE SHOWALTER INDICES BASED OF THE 00Z GFS. ONE TO TWO INCHES OF RAIN APPEAR LIKELY ACROSS THAT AREA THRU 12Z SAT. THESE AMTS SHOULD NOT CAUSE ANY FLOODING PROBLEMS ESPECIALLY SINCE THE RAIN WILL FALL OVER A RELATIVELY LONG PERIOD OF TIME. ALL IN ALL THESE SHOULD BE BENEFICIAL RAINS AS AREAS FROM FAUQUIER COUNTY SWD WERE RECENTLY UPGRADED TO SEVERE DROUGHT. && .LONG TERM /SATURDAY THROUGH THURSDAY/... THRU THE OVERNIGHT HRS FRI NIGHT...A DISSIPATING CONVECTIVE REGION WILL SLIDE NE ACROSS THE SRN APLCHNS W/ AN ELONGATED FRONTAL BNDRY STRETCHED ACROSS THE I-81 CRDR. EARLY SAT MRNG...THIS FRONTAL ZONE LOOKS TO HAVE ENOUGH SUPPORT FROM THE ENTRANCE REGION OF A +120KT JET MAX TO SUPPORT REDEVELOPMENT OUT INTO THE PIEDMONT REGION EAST OF THE MTNS. THE CONVECTIVE COMPLEX WILL PUSH NE INTO CNTRL VA...W/ A BRIEF REDEVELOPMENT PERIOD AS IT NEARS THE MD SIDE OF THE CHSPKE BAY OVERNIGHT. NAM PUSHES THIS FEATURE OFFSHORE SLIGHTLY FASTER THAN THE GFS. EITHER WAY...A RELATIVELY THIN BUT POTENT REGION OF HIGHER QPFS WILL BE POSSIBLE W/ THIS COMPLEX...MAINLY EXPTD TO BE MOD/HEAVY RAINFALL ACTIVITY AND BRIEF GUSTY WINDS...SVR NOT EXPTD. AFT THIS CONVECTIVE BATCH SLIDES OFFSHORE...MUCH OF THE REGION WILL DRY OUT THRU LATE AFTN...W/ ONLY RESIDUAL PRECIP LINGERING NORTH OF THE RETREATING FRONTAL SYSTEM...SLOWLY PUSHING SOUTH AND EAST. BY EARLY EVNG SAT...ANOTHER STRATIFORM REGION WILL DEVELOP ON THE NORTHERN EDGE OF A CONVECTIVE COMPLEX ACROSS THE ERN CAROLINAS... SPREADING UP INTO CNTRL VA AND SRN MD. SEVERAL BRIEF WAVES OF THIS TYPE OF MODERATE PRECIP ACTIVITY EXPTD TO PUSH INTO SRN PORTIONS OF THE CWA THRUOUT THE EVNG HRS AND POSSIBLY OVERNIGHT...THO MAINLY ACROSS THE VA TIDEWATER REGION. EARLY SUN MRNG...THE FLATTENING UPPER TROF AXIS WILL PUSH THE ACTIVITY OFF THE CAROLINA COAST. HIGH PRESSURE TAKING PRESSURE TAKING RESIDENCE OFF THE ST. LAWRENCE INLET WILL BEGIN TO DEVELOP A WEAK CAD SCENARIO /COLD AIR IN A RELATIVE SENSE/. E/RLY FLOW AND A DEVELOPING MARINE LAYER OVERNIGHT SUN INTO EARLY MON. THE MRNG AND EARLY AFTN HRS OF MONDAY HAVE THE STRONGEST SIGNALS OF A HEALTHY MARINE LAYER DEVELOPING ACROSS THE MID ATLNC...UP TO THE BLUE RIDGE /POSBLY INTO THE SHENDH VALLEY W/ A WEAK WEDGING SCENARIO/. AN APPROACHING UPPER TROF AXIS WILL PUSH WEAK S/RLY WINDS INTO THE REGION...POSBLY HELPING TO ERODE THE MARINE LAYER ON TUES. THE UPPER TROF AXIS GETS ABSORBED INTO THE UPPER FLOW...AS THE OFFSHORE HIGH RECONVENES SLIDING MARINE E/RLY FLOW INTO THE MID ATLNC LATE TUES THRU WED...AHEAD OF YET ANOTHER UPPER WAVE. THIS UPPER LOW WILL STAY ACROSS THE UPPER MIDWEST AND GREAT LAKES AREA...INTO HUDSON BAY...W/ LITTLE MORE THAN DISSIPATING -SHRA ACTIVITY FOR THE MID ATLNC EARLY THURS. FROM THERE...THE GFS IS NOW BRINGING IT/S INTENSE CNTRL PLAINS STORM SYSTEM FURTHER SOUTH AND EAST THAN PREV RUNS...W/ MORE INUNDATING RAINS FOR THE CNTRL MS VALLEY REGION IF THIS SOLN PANS OUT. ECMWF NOT W/ THE TIMING...SLIDING A WEAK FEATURE ACROSS THE GREAT LAKES A DAY IN ADVANCE...THO KEEPING A FAIRLY ACTIVE PATTERN W/ A DEEPENING UPPER WAVE OVER THE SRN PLAINS THAT WOULD AFFECT THE ERN SEABOARD INTO THE NEXT WEEK. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... IFR CEILINGS AND FOG EXPECTED TO ABATE THIS AFTERNOON IN FAVOR OF VFR CONIDITIONS BY THE AFTERNOON PUSH. CONDITIONS DETERIOTE THIS EVENING AS MOISTUERE CHANNELS INTO THE REGION AHEAD OF A COLD FRONT. THE MRNG HRS OF SAT WILL SEE A BRIEF AREA OF HEAVIER SHRA ACTIVITY SLIDING THRU THE REGION...MAINLY THE I-95 CRDR W/ A GRADL EXIT OFFSHORE INTO THE LATE MRNG. DRYING OUT THRU THE DAY...W/ MORE PSBLE SHRA/S LATER IN THE EVNG BUT ALL OF THIS EXITING BY EARLY SUNDAY. MONDAY LOOKS TO BE SOCKED IN W/ A MARINE LAYER AND LOW CIGS/VSBYS...AFFECTING ESPC THE NEAR CHESPKE BAY REGION. TUES/WED A WEAKER SCENARIO THO STILL HAVING SOME LINGERING EFFECTS OF THIS REGIME...CLEARING OUT BY THURS. && .MARINE... WINDS FORECAST TO BECOME SOUTHERLY AND STREGTHEN TO NEAR SMALL CRAFT CRITERIA LATE THIS AFTERNOON...SOME GUSTS MAY NEAR 25 KT. THE MID BAY AND LOWER POTOMAC RIVER HAS THE BEST CHANCE OF SMALL CRAFT WINDS OVERNGIHT DUE TO POSITION OF THE WARM FRONT. WARM FRONT WILL BE FLIRTING WITH THE REGION FRIDAY NIGHT...BEFORE PRESSING TO OUR SOUTHEAST AS A COLD FRONT SATURDAY. A SMALL CRAFT ADVISORY MAY BE NEEDED FRIDAY NIGHT SOUTH OF THOMAS POINT LIGHT...AND ACROSS THE LOWER TIDAL POTOMAC RIVER. HIGH PRESSURE BUILDS IN SUNDAY INTO THE EARLY WORK WEEK. && .HYDROLOGY... AT 11Z THIS MORNING...MULTISENSOR PRECIPITATION ESTIMATE INDICATED A HALF INCH TO INCH OF RAINFALL OCCURRED ACROSS MOST OF THE FORECAST AREA LAST NIGHT...WITH TOTALS CLOSER TO A QUARTER TO HALF INCH ACROSS THE NORTHWEST FORECAST AREA. WE WILL MONITOR FORECAST RAINFALL FOR THE AFTERNOON PACKAGE. && .EQUIPMENT... TECHS CONTINUE TO WORK ON THE PROBLEM WITH THE UPPER AIR EQUIPMENT. NO RESOLUTION TIME IS KNOWN AT THIS TIME. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 11 PM EDT THIS EVENING FOR ANZ530>533-535-536. SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 6 AM EDT SATURDAY FOR ANZ534-537. && $$ SYNOPSIS...LFR NEAR TERM...ROGOWSKI SHORT TERM...LFR LONG TERM...GMS AVIATION...ROGOWSKI/GMS MARINE...ROGOWSKI/GMS EQUIPMENT...ROGOWSKI HYDROLOGY...ROGOWSKI
AREA FORECAST DISCUSSION
NWS RALEIGH NC
1211 PM EDT FRI APR 4 2008 .SYNOPSIS... COOL HIGH PRESSURE OVER THE AREA WILL GIVE WAY TO A COASTAL FRONT PUSHING INLAND THIS AFTERNOON. AS THIS FRONT SHIFTS TO OUR NORTH AS A WARM FRONT...A SOUTHWEST FLOW WILL PUMP WARMER AIR INTO THE AREA. A COLD FRONT WILL MOVE INTO OUR REGION LATE TONIGHT...AND PUSH SLOWLY EAST THROUGH THE AREA LATE SATURDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 1000 AM FRIDAY... SFC ANALYSIS THIS MORNING SHOWS A HYBRID COLD AIR DAMMING WEDGE PERSISTING ACROSS ALL OF CENTRAL NC THIS MORNING...WITH A WARM FRONT CURRENTLY ALONG THE CAROLINA COAST. TEMPS ACROSS CENTRAL NC WERE IN THE 40S...WHILE TEMPS ALONG THE IMMEDIATE COAST WERE IN THE 60S. IN THE UPPER LEVELS...SOUTHWEST FLOW ALOFT WAS PRESENT ACROSS THE MID-ATLANTIC AND SOUTHEAST CONUS (DOWNSTREAM OF AN UPPER TROUGH ACROSS THE MIDWEST CONUS). OVERVIEW: PRIMARY FORECAST PROBLEM TODAY WILL REVOLVE AROUND THE DISSIPATION OF THE REMNANT HYBRID COLD AIR DAMMING WEDGE LOCKED IN ACROSS CENTRAL NC. THE FORECAST MODELS WERE APPARENTLY TOO EAGER IN BRINGING THE WARM FRONT IN FROM THE COAST DURING THE OVERNIGHT PERIOD...AS IT REMAINS PINNED ALMOST DIRECTLY ALONG THE COAST AS OF 13Z THIS MORNING. THE TIMING OF THE EROSION OF THE WEDGE WILL DIRECTLY AFFECT THE TEMPERATURE FORECAST THROUGH THE NEAR TERM PERIOD. TONIGHT...THE WEDGE SHOULD BE COMPLETELY ERODED AND CENTRAL NC WILL BE IN THE WARM SECTOR OF THE ELONGATED FRONTAL ZONE APPROACHING FROM THE WEST. TEMPERATURES: TEMPS ACROSS CENTRAL NC CURRENTLY RANGE FROM THE LOWER 40S IN THE TRIAD/NW PIEDMONT TO THE LOWER 50S IN THE SOUTHEAST COASTAL PLAIN. PREVIOUS GUIDANCE FOR HIGH TEMPS TODAY WERE INDICATING THE UPPER 70S TO NEAR 80F...HOWEVER...WITH THE DELAYED EROSION OF THE WEDGE... HIGH TEMPS WILL BE MUCH LOWER THIS AFTERNOON...FROM THE 50S IN THE NW PIEDMONT TO MID 70S POTENTIALLY IN PORTIONS OF THE COASTAL PLAIN. THE 12Z GSO SOUNDING SHOWED THE WEDGE WAS 3 KFT DEEP IN THE NW PIEDMONT...A 12Z AIRCRAFT SOUNDING FROM RDU SHOWED THE WEDGE WAS 2 KFT DEEP IN THE TRIANGLE AREA...AND THERE WAS NO WEDGE EVIDENT ON THE 12Z MHX SOUNDING ALONG THE COAST. THE DOMINANT WEDGE EROSION MECHANISM TODAY ACROSS CENTRAL NC APPEARS TO BE DIURNAL HEATING... GIVEN THAT FLOW ALOFT IS GENERALLY FROM THE SOUTHWEST (PARALLEL TO THE WARM FRONT ALONG THE COAST) AND THE SOUTHERN EXTENT OF THE WEDGE IS STILL IN CENTRAL GEORGIA. THIS WOULD POINT TO A GRADUAL EROSION OF THE WEDGE FROM EAST TO WEST (SHALLOW END TO DEEP END) LATE MORNING THROUGH THIS AFTERNOON...THEN FROM THE SOUTH AS WELL LATER ON THIS AFTERNOON AND EVENING AS SOUTHERLY FLOW STRENGTHENS. COULD SEE WIND GUSTS UP TO 30 MPH LATER THIS AFTERNOON IN LOCATIONS THAT HAVE BEEN WARM SECTORED GIVEN 25-30 KNOT FLOW PROGGED IN THE MIXED LAYER. EXPECT NEARLY STEADY TEMPS IN THE 40S IN THE WEST/NW PIEDMONT THROUGH MUCH OF THE DAY...FINALLY INCREASING THROUGH THE 50S LATER THIS AFTERNOON. LOCATIONS FURTHER TO THE EAST WILL BEGIN TO WARM UP EARLIER ON...WITH FAY/CTZ/GSB/RWI POSSIBLY SEEING TEMPS RISE INTO THE 60S BY 16-18Z THIS AFTERNOON. TONIGHT...TEMPS SHOULD BE NEARLY STEADY IN THE UPPER 50S TO MID 60S ACROSS ALL OF CENTRAL NC IN ADVANCE OF THE COLD FRONT APPROACHING FROM THE WEST. TEMPS MAY SLOWLY RISE IN SOME LOCATIONS...PARTICULARLY BEFORE MORE WIDESPREAD RAIN ARRIVES FROM THE WEST LATER TONIGHT AND SAT MORNING. PRECIPITATION: ISENTROPIC LIFT HAS SIGNIFICANTLY DECREASED ACROSS THE AREA...WITH THE FLOW BECOMING MORE PARALLEL TO THE ISENTROPES. ANY LIFT TODAY WILL BE CONFINED TO THE LOWER LEVELS...IN THE FORM OF WARM ADVECTION AND LOW LEVEL CONVERGENCE ALONG THE WARM FRONT AS IT PROGRESSES INTO THE AREA FROM THE EAST AND SOUTH. THE GFS/NAM DO NOT SHOW MUCH IN THE WAY OF PRECIP THROUGH THE AFTERNOON AND EVENING HOURS...ON THE ORDER OF A FEW HUNDREDTHS OF AN INCH. EXPECT POCKETS OF DRIZZLE OR SPRINKLES THROUGHOUT THE DAY IN LOCATIONS SOCKED IN THE WEDGE...WITH A CHANCE OF CONVECTIVE SHOWERS (AND POSSIBLY ISOLD THUNDERSTORMS) LATER THIS AFTERNOON...PRIMARILY ALONG AND EAST OF HIGHWAY 1...WITH THE BEST CHANCE ALONG/EAST OF INTERSTATE 95 WHERE FCST SOUNDINGS ARE SHOWING UP TO 1500 J/KG OF SFC BASED CAPE WITH TEMPS IN THE LOWER 70S AND DEWPOINTS IN THE MID 60S. PRECIP CHANCES WILL ALSO BE INCREASING FROM THE WEST LATER THIS AFTERNOON/EVENING AS A LINE OF CONVECTION APPROACHES CENTRAL NC FROM THE WEST AHEAD OF THE APPROACHING FRONTAL ZONE. SO...BASICALLY...PRECIP CHANCES WILL INCREASE THROUGHOUT THE DAY...BECOMING LIKELY OVERNIGHT FROM WEST TO EAST AS THE FRONTAL ZONE SHIFTS CLOSER TO THE AREA. RAINFALL AMOUNTS WILL BE GENERALLY LIGHT THROUGH THE DAY TODAY...LESS THAN A TENTH OF AN INCH...ALTHOUGH LOCALLY HIGHER AMOUNTS WILL BE POSSIBLE WITH ANY ISOLATED CONVECTIVE ACTIVITY THAT MAY DEVELOP THIS AFTERNOON IN LOCATIONS THAT HAVE BEEN WARM SECTORED. THE POSSIBILITY OF MORE SUBSTANTIAL RAINFALL WILL BEGIN LATER TONIGHT AND EARLY SAT MORNING IN ASSOC/W THE APPROACHING FRONTAL ZONE AND INCREASING UPPER LEVEL DIVERGENCE AHEAD OF THE APPROACHING UPPER LEVEL TROUGH. CANNOT RULE OUT ISOLATED THUNDERSTORMS OVERNIGHT GIVEN FCST SOUNDINGS SHOWING PWAT VALUES INCREASING TO AROUND 1.50" WITH 500-1000 J/KG OF MUCAPE...AND THEREFORE WILL ALSO KEEP A CHANCE OF THUNDERSTORMS IN THE FORECAST TONIGHT. -VINCENT/STARK && .SHORT TERM /SATURDAY THROUGH SUNDAY/... AS OF 630 AM FRIDAY... BASED ON CONSENSUS OF 06Z GFS AND ITS PREVIOUS TRENDS AND THE 00Z ECMWF INDICATING A MUCH SLOWER FRONTAL PASSAGE... HAVE RAISED POPS THROUGH SATURDAY NIGHT. STORM TOTAL RAINFALL AMOUNTS ARE LIKELY TO BE HIGHER... WIDESPREAD 1-2 INCHES WITH LOCALLY HIGHER AMOUNTS. GRIDDED AND TEXT FORECASTS WERE UPDATED ACCORDINGLY. A GREATER RISK OF HEAVY RAIN WILL BE ON SATURDAY AS THE WAVY FRONT PUSHES SLOWLY EAST THROUGH THE AREA. THE SLOWER FRONTAL MOVEMENT OF THE ECMWF IS PREFERRED... GIVEN THAT THE MID LEVEL FLOW BECOMES NEARLY PARALLEL TO THE SURFACE FRONT WITH NO STRONG PUSH OF COLD AIR OVER THE MOUNTAINS UNTIL AFTER DARK WHEN THE MID LEVEL SHORTWAVE TROUGH NOW DIVING INTO THE WESTERN PLAINS FINALLY PUSHES INTO THE CENTRAL/SRN APPALACHIANS. PRECIPITABLE WATER VALUES NEARLY 300% OF NORMAL AND POSSIBLE TRAINING CELLS OR BANDS WILL LIKELY PUSH RAIN TOTALS TO 1-2 INCHES AND POSSIBLY HIGHER. THE OPERATIONAL MODELS HAVE NOT DONE WELL PREDICTING PRECIP AMOUNTS IN RECENT WEEKS... SO CONFIDENCE IN PRECISE PLACEMENT OF THE HEAVY RAIN RISK IS NOT HIGH. DESPITE THE DROUGHT WE`RE STILL IN... SOILS HAVE MOISTENED A BIT WITH THE LAST COUPLE OF RAIN EVENTS... AND MANY AREAS WITH STILL-HARDENED GROUND COULD SEE RAPID RUNOFF INTO CREEKS AND POOR DRAINAGE AREAS. WILL INCLUDE THIS THREAT IN THE HAZARDOUS WEATHER OUTLOOK. REGARDING THE SEVERE RISK... A SLUG OF UPPER DIVERGENCE WITHIN THE RIGHT ENTRANCE REGION OF THE JET WILL ACCOMPANY DECENT 700-500 MB LAPSE RATES NEAR 6.5 C/KM AND MODERATE MID LEVEL HEIGHT FALLS... AND IF THE COLD FRONT IS INDEED DELAYED LIKE THE ECMWF DEPICTS OVER THE FASTER GFS AND ESPECIALLY NAM... THE LOW LEVELS WILL BE MORE UNSTABLE THAN NAM/GFS FORECAST SOUNDINGS DEPICT. THIS SHORTWAVE DOES DAMPEN QUITE A BIT AS IT ENCOUNTERS THE ATLANTIC RIDGE HOWEVER AND MAY NOT CONTRIBUTE MUCH TO BROAD LIFT. WIND FIELDS LOOK GOOD WITH NEARLY 50 KTS OF 0-6 KM SHEAR AHEAD OF THE FRONT ALTHOUGH THE LOW LEVEL JET CORE WILL BE SHIFTING INTO THE COASTAL SECTIONS. THE PRIMARY THREAT STILL APPEARS TO BE FROM STRAIGHT LINE DAMAGING WINDS ESPECIALLY EAST OF HIGHWAY 1 WHERE THE NAM GIVES A MUCAPE OF 1000-1500 J/KG. EXISTING HIGHS OF 68-76 STILL LOOK REASONABLE WITH STRONG WARM ADVECTION AHEAD OF THE FRONT. AS THE FRONT SHIFTS EASTWARD LATE SATURDAY NIGHT AS INDICATED BY THE PREFERRED SLOWER ECMWF... SHOWER/STORM CHANCES WILL DIMINISH GRADUALLY FROM WEST TO EAST BUT SIGNIFICANT CLEARING WILL LIKELY HOLD OFF UNTIL SUNDAY. LOWS SATURDAY NIGHT 46-55. THE SURFACE RIDGE THAT WILL BECOME CENTERED OVER EASTERN CANADA WILL RIDGE NARROWLY SOUTHWARD DOWN THROUGH THE PIEDMONT SUNDAY... AND THIS SHOULD KEEP ENOUGH ATLANTIC MOISTURE PUMPING ACROSS THE VA/NC COAST FOR VARIABLE CLOUD COVER EAST/PARTLY CLOUDY WEST THROUGH SUNDAY. EXPECT BELOW NORMAL HIGHS SUNDAY OF 60-68... COOLER NORTHEAST... WITH PERIODS OF CLOUDS AND WITH THICKNESSES STARTING NEAR NORMAL BUT LIKELY TO HOLD STEADY OR FALL THROUGH THE DAY. -GIH && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 340 AM FRIDAY... THIS APPEARS TO BE A RELATIVELY QUIET WEATHER PERIOD. A MID LEVEL VORTEX TRACKING NE THROUGH THE NRN GREAT LAKES ON MONDAY SERVES TO BUILD UP MID LEVEL RIDGING ATOP THE SURFACE RIDGE EXTENDING FROM FAR ERN CANADA DOWN THROUGH THE CAROLINAS. THE NARROW NOSE OF COOLER TEMPERATURES SHOULD PERSIST OVER THE CWA MONDAY YIELDING BELOW NORMAL HIGHS IN THE LOW-MID 60S. ABUNDANT BOUNDARY LAYER MOISTURE WITH A LINGERING FLUX OF ATLANTIC MOISTURE SHOULD KEEP SKIES PARTLY TO MOSTLY CLOUDY THROUGH TUESDAY... AND WHILE BRIEF PERIODS OF ISENTROPIC UPGLIDE ARE POSSIBLE... THE LACK OF OTHER LIFT MECHANISMS AND THE UNCERTAINTY OF THE DEGREE OF FORCING PROVIDED BY ANY SUCH LIFT PRECLUDES INCLUDING A POP THROUGH TUESDAY. ANOTHER MID LEVEL VORTEX TRACKS NE THROUGH THE GREAT LAKES WEDNESDAY/WEDNESDAY NIGHT RESULTING IN BUILDING RIDGING OVER THE SOUTHEAST. WILL CONTINUE WITH MODIFYING TEMPERATURES SURPASSING NORMALS BY 1-2 CATEGORIES BY THURSDAY AS THICKNESSES REACH 20-30 M ABOVE NORMAL. -GIH && .AVIATION /18Z FRIDAY THROUGH TUESDAY/... AS OF 1200 PM FRIDAY... WIDESPREAD IFR/LIFR CONDITIONS ARE EXPECTED TO IMPROVE TO MVFR BY 00Z THIS AFTERNOON AS THE REMNANT HYBRID COLD AIR DAMMING WEDGE ERODES FROM EAST TO WEST. CONDITIONS WILL FIRST IMPROVE AT RWI/FAY...FOLLOWED BY RDU...AND FINALLY GSO/INT. ONCE THE WARM FRONT PASSES BY ANY GIVEN LOCATION AND TEMPS RISE/MIXING DEEPENS...WINDS ARE EXPECTED TO PICK UP OUT OF THE SOUTHWEST AT 10-15 KNOTS...WITH GUSTS UP TO 25 KNOTS POSSIBLE BASED ON FCST SOUNDINGS WHICH SHOW 25-30 KNOTS IN THIS MIXED LAYER. A COLD FRONT WILL APPROACH THE AREA FROM THE WEST TONIGHT...AND EXPECT WIDESPREAD SHOWERS TO INCREASE FROM WEST TO EAST OVERNIGHT AHEAD OF THE FRONT...WITH ASSOC IFR/LIFR CONDITIONS. AN ISOLATED THUNDERSTORM IS NOT OUT OF THE QUESTION DURING THE OVERNIGHT HOURS. WIDESPREAD MODERATE TO HEAVY RAIN IS EXPECTED IN ASSOC/W THE FRONT AS IT SLOWS DOWN TO A CRAWL AND STALLS ACROSS CENTRAL NC DURING THE DAY SATURDAY. IFR/LIFR CONDITIONS IN SHOWER ACTIVITY ARE EXPECTED THROUGHOUT THE DAY...WITH A CHANCE OF THUNDERSTORMS EVERYWHERE... ALTHOUGH THE BEST CHANCE WILL BE IN THE COASTAL PLAIN (RWI/FAY TAF SITES). IFR/LIFR CONDITIONS ARE EXPECTED TO PERSIST INTO SATURDAY NIGHT AND SUNDAY MORNING AS A WAVE OF LOW PRESSURE DEVELOPS ALONG THE STALLED FRONT ACROSS THE AREA. CONDITIONS ARE EXPECTED TO IMPROVE TO MVFR BY NOON SUNDAY...WITH VFR CONDITIONS BY SUNSET SUNDAY EVENING/NIGHT AS HIGH PRESSURE BUILDS INTO THE AREA FROM THE NORTH. IFR/MVFR CEILINGS MAY BE POSSIBLE SUNDAY NIGHT AND MONDAY NIGHT WITH A NORTHEAST LOW LEVEL FLOW...ALTHOUGH VFR CONDITIONS ARE GENERALLY EXPECTED FROM SUNDAY NIGHT THROUGH TUESDAY WITH HIGH PRESSURE RIDGING INTO THE AREA FROM THE NORTH AND A LIMITED FLOW OF MOISTURE INTO THE AREA. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT/STARK SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...VINCENT
AREA FORECAST DISCUSSION
NWS RALEIGH NC
1024 AM EDT FRI APR 4 2008 .SYNOPSIS... COOL HIGH PRESSURE OVER THE AREA WILL GIVE WAY TO A COASTAL FRONT PUSHING INLAND THIS AFTERNOON. AS THIS FRONT SHIFTS TO OUR NORTH AS A WARM FRONT...A SOUTHWEST FLOW WILL PUMP WARMER AIR INTO THE AREA. A COLD FRONT WILL MOVE INTO OUR REGION LATE TONIGHT...AND PUSH SLOWLY EAST THROUGH THE AREA LATE SATURDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 1000 AM FRIDAY... SFC ANALYSIS THIS MORNING SHOWS A HYBRID COLD AIR DAMMING WEDGE PERSISTING ACROSS ALL OF CENTRAL NC THIS MORNING...WITH A WARM FRONT CURRENTLY ALONG THE CAROLINA COAST. TEMPS ACROSS CENTRAL NC WERE IN THE 40S...WHILE TEMPS ALONG THE IMMEDIATE COAST WERE IN THE 60S. IN THE UPPER LEVELS...SOUTHWEST FLOW ALOFT WAS PRESENT ACROSS THE MID-ATLANTIC AND SOUTHEAST CONUS (DOWNSTREAM OF AN UPPER TROUGH ACROSS THE MIDWEST CONUS). OVERVIEW: PRIMARY FORECAST PROBLEM TODAY WILL REVOLVE AROUND THE DISSIPATION OF THE REMNANT HYBRID COLD AIR DAMMING WEDGE LOCKED IN ACROSS CENTRAL NC. THE FORECAST MODELS WERE APPARENTLY TOO EAGER IN BRINGING THE WARM FRONT IN FROM THE COAST DURING THE OVERNIGHT PERIOD...AS IT REMAINS PINNED ALMOST DIRECTLY ALONG THE COAST AS OF 13Z THIS MORNING. THE TIMING OF THE EROSION OF THE WEDGE WILL DIRECTLY AFFECT THE TEMPERATURE FORECAST THROUGH THE NEAR TERM PERIOD. TONIGHT...THE WEDGE SHOULD BE COMPLETELY ERODED AND CENTRAL NC WILL BE IN THE WARM SECTOR OF THE ELONGATED FRONTAL ZONE APPROACHING FROM THE WEST. TEMPERATURES: TEMPS ACROSS CENTRAL NC CURRENTLY RANGE FROM THE LOWER 40S IN THE TRIAD/NW PIEDMONT TO THE LOWER 50S IN THE SOUTHEAST COASTAL PLAIN. PREVIOUS GUIDANCE FOR HIGH TEMPS TODAY WERE INDICATING THE UPPER 70S TO NEAR 80F...HOWEVER...WITH THE DELAYED EROSION OF THE WEDGE... HIGH TEMPS WILL BE MUCH LOWER THIS AFTERNOON...FROM THE 50S IN THE NW PIEDMONT TO MID 70S POTENTIALLY IN PORTIONS OF THE COASTAL PLAIN. THE 12Z GSO SOUNDING SHOWED THE WEDGE WAS 3 KFT DEEP IN THE NW PIEDMONT...A 12Z AIRCRAFT SOUNDING FROM RDU SHOWED THE WEDGE WAS 2 KFT DEEP IN THE TRIANGLE AREA...AND THERE WAS NO WEDGE EVIDENT ON THE 12Z MHX SOUNDING ALONG THE COAST. THE DOMINANT WEDGE EROSION MECHANISM TODAY ACROSS CENTRAL NC APPEARS TO BE DIURNAL HEATING... GIVEN THAT FLOW ALOFT IS GENERALLY FROM THE SOUTHWEST (PARALLEL TO THE WARM FRONT ALONG THE COAST) AND THE SOUTHERN EXTENT OF THE WEDGE IS STILL IN CENTRAL GEORGIA. THIS WOULD POINT TO A GRADUAL EROSION OF THE WEDGE FROM EAST TO WEST (SHALLOW END TO DEEP END) LATE MORNING THROUGH THIS AFTERNOON...THEN FROM THE SOUTH AS WELL LATER ON THIS AFTERNOON AND EVENING AS SOUTHERLY FLOW STRENGTHENS. COULD SEE WIND GUSTS UP TO 30 MPH LATER THIS AFTERNOON IN LOCATIONS THAT HAVE BEEN WARM SECTORED GIVEN 25-30 KNOT FLOW PROGGED IN THE MIXED LAYER. EXPECT NEARLY STEADY TEMPS IN THE 40S IN THE WEST/NW PIEDMONT THROUGH MUCH OF THE DAY...FINALLY INCREASING THROUGH THE 50S LATER THIS AFTERNOON. LOCATIONS FURTHER TO THE EAST WILL BEGIN TO WARM UP EARLIER ON...WITH FAY/CTZ/GSB/RWI POSSIBLY SEEING TEMPS RISE INTO THE 60S BY 16-18Z THIS AFTERNOON. TONIGHT...TEMPS SHOULD BE NEARLY STEADY IN THE UPPER 50S TO MID 60S ACROSS ALL OF CENTRAL NC IN ADVANCE OF THE COLD FRONT APPROACHING FROM THE WEST. TEMPS MAY SLOWLY RISE IN SOME LOCATIONS...PARTICULARLY BEFORE MORE WIDESPREAD RAIN ARRIVES FROM THE WEST LATER TONIGHT AND SAT MORNING. PRECIPITATION: ISENTROPIC LIFT HAS SIGNIFICANTLY DECREASED ACROSS THE AREA...WITH THE FLOW BECOMING MORE PARALLEL TO THE ISENTROPES. ANY LIFT TODAY WILL BE CONFINED TO THE LOWER LEVELS...IN THE FORM OF WARM ADVECTION AND LOW LEVEL CONVERGENCE ALONG THE WARM FRONT AS IT PROGRESSES INTO THE AREA FROM THE EAST AND SOUTH. THE GFS/NAM DO NOT SHOW MUCH IN THE WAY OF PRECIP THROUGH THE AFTERNOON AND EVENING HOURS...ON THE ORDER OF A FEW HUNDREDTHS OF AN INCH. EXPECT POCKETS OF DRIZZLE OR SPRINKLES THROUGHOUT THE DAY IN LOCATIONS SOCKED IN THE WEDGE...WITH A CHANCE OF CONVECTIVE SHOWERS (AND POSSIBLY ISOLD THUNDERSTORMS) LATER THIS AFTERNOON...PRIMARILY ALONG AND EAST OF HIGHWAY 1...WITH THE BEST CHANCE ALONG/EAST OF INTERSTATE 95 WHERE FCST SOUNDINGS ARE SHOWING UP TO 1500 J/KG OF SFC BASED CAPE WITH TEMPS IN THE LOWER 70S AND DEWPOINTS IN THE MID 60S. PRECIP CHANCES WILL ALSO BE INCREASING FROM THE WEST LATER THIS AFTERNOON/EVENING AS A LINE OF CONVECTION APPROACHES CENTRAL NC FROM THE WEST AHEAD OF THE APPROACHING FRONTAL ZONE. SO...BASICALLY...PRECIP CHANCES WILL INCREASE THROUGHOUT THE DAY...BECOMING LIKELY OVERNIGHT FROM WEST TO EAST AS THE FRONTAL ZONE SHIFTS CLOSER TO THE AREA. RAINFALL AMOUNTS WILL BE GENERALLY LIGHT THROUGH THE DAY TODAY...LESS THAN A TENTH OF AN INCH...ALTHOUGH LOCALLY HIGHER AMOUNTS WILL BE POSSIBLE WITH ANY ISOLATED CONVECTIVE ACTIVITY THAT MAY DEVELOP THIS AFTERNOON IN LOCATIONS THAT HAVE BEEN WARM SECTORED. THE POSSIBILITY OF MORE SUBSTANTIAL RAINFALL WILL BEGIN LATER TONIGHT AND EARLY SAT MORNING IN ASSOC/W THE APPROACHING FRONTAL ZONE AND INCREASING UPPER LEVEL DIVERGENCE AHEAD OF THE APPROACHING UPPER LEVEL TROUGH. CANNOT RULE OUT ISOLATED THUNDERSTORMS OVERNIGHT GIVEN FCST SOUNDINGS SHOWING PWAT VALUES INCREASING TO AROUND 1.50" WITH 500-1000 J/KG OF MUCAPE...AND THEREFORE WILL ALSO KEEP A CHANCE OF THUNDERSTORMS IN THE FORECAST TONIGHT. -VINCENT/STARK && .SHORT TERM /SATURDAY THROUGH SUNDAY/... AS OF 630 AM FRIDAY... BASED ON CONSENSUS OF 06Z GFS AND ITS PREVIOUS TRENDS AND THE 00Z ECMWF INDICATING A MUCH SLOWER FRONTAL PASSAGE... HAVE RAISED POPS THROUGH SATURDAY NIGHT. STORM TOTAL RAINFALL AMOUNTS ARE LIKELY TO BE HIGHER... WIDESPREAD 1-2 INCHES WITH LOCALLY HIGHER AMOUNTS. GRIDDED AND TEXT FORECASTS WERE UPDATED ACCORDINGLY. A GREATER RISK OF HEAVY RAIN WILL BE ON SATURDAY AS THE WAVY FRONT PUSHES SLOWLY EAST THROUGH THE AREA. THE SLOWER FRONTAL MOVEMENT OF THE ECMWF IS PREFERRED... GIVEN THAT THE MID LEVEL FLOW BECOMES NEARLY PARALLEL TO THE SURFACE FRONT WITH NO STRONG PUSH OF COLD AIR OVER THE MOUNTAINS UNTIL AFTER DARK WHEN THE MID LEVEL SHORTWAVE TROUGH NOW DIVING INTO THE WESTERN PLAINS FINALLY PUSHES INTO THE CENTRAL/SRN APPALACHIANS. PRECIPITABLE WATER VALUES NEARLY 300% OF NORMAL AND POSSIBLE TRAINING CELLS OR BANDS WILL LIKELY PUSH RAIN TOTALS TO 1-2 INCHES AND POSSIBLY HIGHER. THE OPERATIONAL MODELS HAVE NOT DONE WELL PREDICTING PRECIP AMOUNTS IN RECENT WEEKS... SO CONFIDENCE IN PRECISE PLACEMENT OF THE HEAVY RAIN RISK IS NOT HIGH. DESPITE THE DROUGHT WE`RE STILL IN... SOILS HAVE MOISTENED A BIT WITH THE LAST COUPLE OF RAIN EVENTS... AND MANY AREAS WITH STILL-HARDENED GROUND COULD SEE RAPID RUNOFF INTO CREEKS AND POOR DRAINAGE AREAS. WILL INCLUDE THIS THREAT IN THE HAZARDOUS WEATHER OUTLOOK. REGARDING THE SEVERE RISK... A SLUG OF UPPER DIVERGENCE WITHIN THE RIGHT ENTRANCE REGION OF THE JET WILL ACCOMPANY DECENT 700-500 MB LAPSE RATES NEAR 6.5 C/KM AND MODERATE MID LEVEL HEIGHT FALLS... AND IF THE COLD FRONT IS INDEED DELAYED LIKE THE ECMWF DEPICTS OVER THE FASTER GFS AND ESPECIALLY NAM... THE LOW LEVELS WILL BE MORE UNSTABLE THAN NAM/GFS FORECAST SOUNDINGS DEPICT. THIS SHORTWAVE DOES DAMPEN QUITE A BIT AS IT ENCOUNTERS THE ATLANTIC RIDGE HOWEVER AND MAY NOT CONTRIBUTE MUCH TO BROAD LIFT. WIND FIELDS LOOK GOOD WITH NEARLY 50 KTS OF 0-6 KM SHEAR AHEAD OF THE FRONT ALTHOUGH THE LOW LEVEL JET CORE WILL BE SHIFTING INTO THE COASTAL SECTIONS. THE PRIMARY THREAT STILL APPEARS TO BE FROM STRAIGHT LINE DAMAGING WINDS ESPECIALLY EAST OF HIGHWAY 1 WHERE THE NAM GIVES A MUCAPE OF 1000-1500 J/KG. EXISTING HIGHS OF 68-76 STILL LOOK REASONABLE WITH STRONG WARM ADVECTION AHEAD OF THE FRONT. AS THE FRONT SHIFTS EASTWARD LATE SATURDAY NIGHT AS INDICATED BY THE PREFERRED SLOWER ECMWF... SHOWER/STORM CHANCES WILL DIMINISH GRADUALLY FROM WEST TO EAST BUT SIGNIFICANT CLEARING WILL LIKELY HOLD OFF UNTIL SUNDAY. LOWS SATURDAY NIGHT 46-55. THE SURFACE RIDGE THAT WILL BECOME CENTERED OVER EASTERN CANADA WILL RIDGE NARROWLY SOUTHWARD DOWN THROUGH THE PIEDMONT SUNDAY... AND THIS SHOULD KEEP ENOUGH ATLANTIC MOISTURE PUMPING ACROSS THE VA/NC COAST FOR VARIABLE CLOUD COVER EAST/PARTLY CLOUDY WEST THROUGH SUNDAY. EXPECT BELOW NORMAL HIGHS SUNDAY OF 60-68... COOLER NORTHEAST... WITH PERIODS OF CLOUDS AND WITH THICKNESSES STARTING NEAR NORMAL BUT LIKELY TO HOLD STEADY OR FALL THROUGH THE DAY. -GIH && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 340 AM FRIDAY... THIS APPEARS TO BE A RELATIVELY QUIET WEATHER PERIOD. A MID LEVEL VORTEX TRACKING NE THROUGH THE NRN GREAT LAKES ON MONDAY SERVES TO BUILD UP MID LEVEL RIDGING ATOP THE SURFACE RIDGE EXTENDING FROM FAR ERN CANADA DOWN THROUGH THE CAROLINAS. THE NARROW NOSE OF COOLER TEMPERATURES SHOULD PERSIST OVER THE CWA MONDAY YIELDING BELOW NORMAL HIGHS IN THE LOW-MID 60S. ABUNDANT BOUNDARY LAYER MOISTURE WITH A LINGERING FLUX OF ATLANTIC MOISTURE SHOULD KEEP SKIES PARTLY TO MOSTLY CLOUDY THROUGH TUESDAY... AND WHILE BRIEF PERIODS OF ISENTROPIC UPGLIDE ARE POSSIBLE... THE LACK OF OTHER LIFT MECHANISMS AND THE UNCERTAINTY OF THE DEGREE OF FORCING PROVIDED BY ANY SUCH LIFT PRECLUDES INCLUDING A POP THROUGH TUESDAY. ANOTHER MID LEVEL VORTEX TRACKS NE THROUGH THE GREAT LAKES WEDNESDAY/WEDNESDAY NIGHT RESULTING IN BUILDING RIDGING OVER THE SOUTHEAST. WILL CONTINUE WITH MODIFYING TEMPERATURES SURPASSING NORMALS BY 1-2 CATEGORIES BY THURSDAY AS THICKNESSES REACH 20-30 M ABOVE NORMAL. -GIH && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 225 AM FRIDAY... WARM...MOIST FLOW OVERRUNNING COOL...NORTH TO NORTHEAST FLOW AT THE SURFACE WILL RESULT IN LIFR CONDITIONS IN LOW CLOUDS...LIGHT RAIN... DRIZZLE AND FOG EARLY THIS FRIDAY MORNING. CONDITIONS WILL GRADUALLY IMPROVE FROM THE EAST DURING THE LATE MORNING TO EARLY AFTERNOON AS A WARM FRONT WORKS WESTWARD FROM THE COAST. CONDITIONS WILL LIFT TO MVFR RWI...RDU...FAY BETWEEN 15 AND 17Z AND OVER GSO AND INT AFTER 18Z. AS THE ATMOSPHERE MIXES... AFTERNOON HEATING WILL COMBINE WITH WARM... SOUTHERLY FLOW TO GIVE A CHANCE OF SHOWERS AND THUNDERSTORMS LATE TODAY AND TONIGHT. A COLD FRONT WILL APPROACH AND MOVE ACROSS THE REGION SATURDAY. WE CAN EXPECT MVFR TO IFR CONDITIONS IN SHOWERS AND SCATTERED THUNDERSTORMS. THE COLD FRONT WILL LINGER ALONG THE COAST LATE SATURDAY THROUGH EARLY SUNDAY... RESULTING IN AS SLOW IMPROVEMENT OVER THE EASTERN TAFS THROUGH THE NIGHT. HIGH PRESSURE WILL BUILD OVER THE AREA DURING THE DAY SUNDAY AND REMAIN THROUGH TUESDAY. WE CAN EXPECT VFR CONDITIONS AS DRY AIR TAKES HOLD OF THE REGION. -RHJ && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT/STARK SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...RHJ
AREA FORECAST DISCUSSION
NWS RALEIGH NC
953 AM EDT FRI APR 4 2008 .SYNOPSIS... COOL HIGH PRESSURE OVER THE AREA WILL GIVE WAY TO A COASTAL FRONT PUSHING INLAND THIS AFTERNOON. AS THIS FRONT SHIFTS TO OUR NORTH AS A WARM FRONT...A SOUTHWEST FLOW WILL PUMP WARMER AIR INTO THE AREA. A COLD FRONT WILL MOVE INTO OUR REGION LATE TONIGHT...AND PUSH SLOWLY EAST THROUGH THE AREA LATE SATURDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 1000 AM FRIDAY... SFC ANALYSIS THIS MORNING SHOWS A HYBRID COLD AIR DAMMING WEDGE PERSISTING ACROSS ALL OF CENTRAL NC THIS MORNING...WITH A WARM FRONT CURRENTLY ALONG THE CAROLINA COAST. TEMPS ACROSS CENTRAL NC WERE IN THE 40S...WHILE TEMPS ALONG THE IMMEDIATE COAST WERE IN THE 60S. IN THE UPPER LEVELS...SOUTHWEST FLOW ALOFT WAS PRESENT ACROSS THE MID-ATLANTIC AND SOUTHEAST CONUS (DOWNSTREAM OF AN UPPER TROUGH ACROSS THE MIDWEST CONUS). OVERVIEW: PRIMARY FORECAST PROBLEM TODAY WILL REVOLVE AROUND THE DISSIPATION OF THE REMNANT HYBRID COLD AIR DAMMING WEDGE LOCKED IN ACROSS CENTRAL NC. THE FORECAST MODELS WERE APPARENTLY TOO EAGER IN BRINGING THE WARM FRONT IN FROM THE COAST DURING THE OVERNIGHT PERIOD...AS IT REMAINS PINNED ALMOST DIRECTLY ALONG THE COAST AS OF 13Z THIS MORNING. THE TIMING OF THE EROSION OF THE WEDGE WILL DIRECTLY AFFECT THE TEMPERATURE FORECAST THROUGH THE NEAR TERM PERIOD. TONIGHT...THE WEDGE SHOULD BE COMPLETELY ERODED AND CENTRAL NC WILL BE IN THE WARM SECTOR OF THE ELONGATED FRONTAL ZONE APPROACHING FROM THE WEST. TEMPERATURES: TEMPS ACROSS CENTRAL NC CURRENTLY RANGE FROM THE LOWER 40S IN THE TRIAD/NW PIEDMONT TO THE LOWER 50S IN THE SOUTHEAST COASTAL PLAIN. PREVIOUS GUIDANCE FOR HIGH TEMPS TODAY WERE INDICATING THE UPPER 70S TO NEAR 80F...HOWEVER...WITH THE DELAYED EROSION OF THE WEDGE... HIGH TEMPS WILL BE MUCH LOWER THIS AFTERNOON...FROM THE 50S IN THE NW PIEDMONT TO MID 70S POTENTIALLY IN PORTIONS OF THE COASTAL PLAIN. THE 12Z GSO SOUNDING SHOWED THE WEDGE WAS 3 KFT DEEP IN THE NW PIEDMONT...A 12Z AIRCRAFT SOUNDING FROM RDU SHOWED THE WEDGE WAS 2 KFT DEEP IN THE TRIANGLE AREA...AND THERE WAS NO WEDGE EVIDENT ON THE 12Z MHX SOUNDING ALONG THE COAST. THE DOMINANT WEDGE EROSION MECHANISM TODAY ACROSS CENTRAL NC APPEARS TO BE DIURNAL HEATING... GIVEN THAT FLOW ALOFT IS GENERALLY FROM THE SOUTHWEST (PARALLEL TO THE WARM FRONT ALONG THE COAST) AND THE SOUTHERN EXTENT OF THE WEDGE IS STILL IN CENTRAL GEORGIA. THIS WOULD POINT TO A GRADUAL EROSION OF THE WEDGE FROM EAST TO WEST (SHALLOW END TO DEEP END) LATE MORNING THROUGH THIS AFTERNOON...THEN FROM THE SOUTH AS WELL LATER ON THIS AFTERNOON AND EVENING AS SOUTHERLY FLOW STRENGTHENS. EXPECT NEARLY STEADY TEMPS IN THE 40S IN THE WEST/NW PIEDMONT THROUGH MUCH OF THE DAY...FINALLY INCREASING THROUGH THE 50S LATER THIS AFTERNOON. LOCATIONS FURTHER TO THE EAST WILL BEGIN TO WARM UP EARLIER ON...WITH FAY/CTZ/GSB/RWI POSSIBLY SEEING TEMPS RISE INTO THE 60S BY 16-18Z THIS AFTERNOON. TONIGHT...TEMPS SHOULD BE NEARLY STEADY IN THE UPPER 50S TO MID 60S ACROSS ALL OF CENTRAL NC IN ADVANCE OF THE COLD FRONT APPROACHING FROM THE WEST. TEMPS MAY SLOWLY RISE IN SOME LOCATIONS...PARTICULARLY BEFORE MORE WIDESPREAD RAIN ARRIVES FROM THE WEST LATER TONIGHT AND SAT MORNING. PRECIPITATION: ISENTROPIC LIFT HAS SIGNIFICANTLY DECREASED ACROSS THE AREA...WITH THE FLOW BECOMING MORE PARALLEL TO THE ISENTROPES. ANY LIFT TODAY WILL BE CONFINED TO THE LOWER LEVELS...IN THE FORM OF WARM ADVECTION AND LOW LEVEL CONVERGENCE ALONG THE WARM FRONT AS IT PROGRESSES INTO THE AREA FROM THE EAST AND SOUTH. THE GFS/NAM DO NOT SHOW MUCH IN THE WAY OF PRECIP THROUGH THE AFTERNOON AND EVENING HOURS...ON THE ORDER OF A FEW HUNDREDTHS OF AN INCH. EXPECT POCKETS OF DRIZZLE OR SPRINKLES THROUGHOUT THE DAY IN LOCATIONS SOCKED IN THE WEDGE...WITH A CHANCE OF CONVECTIVE SHOWERS (AND POSSIBLY ISOLD THUNDERSTORMS) LATER THIS AFTERNOON...PRIMARILY ALONG AND EAST OF HIGHWAY 1...WITH THE BEST CHANCE ALONG/EAST OF INTERSTATE 95 WHERE FCST SOUNDINGS ARE SHOWING UP TO 1500 J/KG OF SFC BASED CAPE WITH TEMPS IN THE LOWER 70S AND DEWPOINTS IN THE MID 60S. PRECIP CHANCES WILL ALSO BE INCREASING FROM THE WEST LATER THIS AFTERNOON/EVENING AS A LINE OF CONVECTION APPROACHES CENTRAL NC FROM THE WEST AHEAD OF THE APPROACHING FRONTAL ZONE. SO...BASICALLY...PRECIP CHANCES WILL INCREASE THROUGHOUT THE DAY...BECOMING LIKELY OVERNIGHT FROM WEST TO EAST AS THE FRONTAL ZONE SHIFTS CLOSER TO THE AREA. RAINFALL AMOUNTS WILL BE GENERALLY LIGHT THROUGH THE DAY TODAY...LESS THAN A TENTH OF AN INCH...ALTHOUGH LOCALLY HIGHER AMOUNTS WILL BE POSSIBLE WITH ANY ISOLATED CONVECTIVE ACTIVITY THAT MAY DEVELOP THIS AFTERNOON IN LOCATIONS THAT HAVE BEEN WARM SECTORED. THE POSSIBILITY OF MORE SUBSTANTIAL RAINFALL WILL BEGIN LATER TONIGHT AND EARLY SAT MORNING IN ASSOC/W THE APPROACHING FRONTAL ZONE AND INCREASING UPPER LEVEL DIVERGENCE AHEAD OF THE APPROACHING UPPER LEVEL TROUGH. CANNOT RULE OUT ISOLATED THUNDERSTORMS OVERNIGHT GIVEN FCST SOUNDINGS SHOWING PWAT VALUES INCREASING TO AROUND 1.50" WITH 500-1000 J/KG OF MUCAPE...AND THEREFORE WILL ALSO KEEP A CHANCE OF THUNDERSTORMS IN THE FORECAST TONIGHT. -VINCENT && .SHORT TERM /SATURDAY THROUGH SUNDAY/... AS OF 630 AM FRIDAY... BASED ON CONSENSUS OF 06Z GFS AND ITS PREVIOUS TRENDS AND THE 00Z ECMWF INDICATING A MUCH SLOWER FRONTAL PASSAGE... HAVE RAISED POPS THROUGH SATURDAY NIGHT. STORM TOTAL RAINFALL AMOUNTS ARE LIKELY TO BE HIGHER... WIDESPREAD 1-2 INCHES WITH LOCALLY HIGHER AMOUNTS. GRIDDED AND TEXT FORECASTS WERE UPDATED ACCORDINGLY. A GREATER RISK OF HEAVY RAIN WILL BE ON SATURDAY AS THE WAVY FRONT PUSHES SLOWLY EAST THROUGH THE AREA. THE SLOWER FRONTAL MOVEMENT OF THE ECMWF IS PREFERRED... GIVEN THAT THE MID LEVEL FLOW BECOMES NEARLY PARALLEL TO THE SURFACE FRONT WITH NO STRONG PUSH OF COLD AIR OVER THE MOUNTAINS UNTIL AFTER DARK WHEN THE MID LEVEL SHORTWAVE TROUGH NOW DIVING INTO THE WESTERN PLAINS FINALLY PUSHES INTO THE CENTRAL/SRN APPALACHIANS. PRECIPITABLE WATER VALUES NEARLY 300% OF NORMAL AND POSSIBLE TRAINING CELLS OR BANDS WILL LIKELY PUSH RAIN TOTALS TO 1-2 INCHES AND POSSIBLY HIGHER. THE OPERATIONAL MODELS HAVE NOT DONE WELL PREDICTING PRECIP AMOUNTS IN RECENT WEEKS... SO CONFIDENCE IN PRECISE PLACEMENT OF THE HEAVY RAIN RISK IS NOT HIGH. DESPITE THE DROUGHT WE`RE STILL IN... SOILS HAVE MOISTENED A BIT WITH THE LAST COUPLE OF RAIN EVENTS... AND MANY AREAS WITH STILL-HARDENED GROUND COULD SEE RAPID RUNOFF INTO CREEKS AND POOR DRAINAGE AREAS. WILL INCLUDE THIS THREAT IN THE HAZARDOUS WEATHER OUTLOOK. REGARDING THE SEVERE RISK... A SLUG OF UPPER DIVERGENCE WITHIN THE RIGHT ENTRANCE REGION OF THE JET WILL ACCOMPANY DECENT 700-500 MB LAPSE RATES NEAR 6.5 C/KM AND MODERATE MID LEVEL HEIGHT FALLS... AND IF THE COLD FRONT IS INDEED DELAYED LIKE THE ECMWF DEPICTS OVER THE FASTER GFS AND ESPECIALLY NAM... THE LOW LEVELS WILL BE MORE UNSTABLE THAN NAM/GFS FORECAST SOUNDINGS DEPICT. THIS SHORTWAVE DOES DAMPEN QUITE A BIT AS IT ENCOUNTERS THE ATLANTIC RIDGE HOWEVER AND MAY NOT CONTRIBUTE MUCH TO BROAD LIFT. WIND FIELDS LOOK GOOD WITH NEARLY 50 KTS OF 0-6 KM SHEAR AHEAD OF THE FRONT ALTHOUGH THE LOW LEVEL JET CORE WILL BE SHIFTING INTO THE COASTAL SECTIONS. THE PRIMARY THREAT STILL APPEARS TO BE FROM STRAIGHT LINE DAMAGING WINDS ESPECIALLY EAST OF HIGHWAY 1 WHERE THE NAM GIVES A MUCAPE OF 1000-1500 J/KG. EXISTING HIGHS OF 68-76 STILL LOOK REASONABLE WITH STRONG WARM ADVECTION AHEAD OF THE FRONT. AS THE FRONT SHIFTS EASTWARD LATE SATURDAY NIGHT AS INDICATED BY THE PREFERRED SLOWER ECMWF... SHOWER/STORM CHANCES WILL DIMINISH GRADUALLY FROM WEST TO EAST BUT SIGNIFICANT CLEARING WILL LIKELY HOLD OFF UNTIL SUNDAY. LOWS SATURDAY NIGHT 46-55. THE SURFACE RIDGE THAT WILL BECOME CENTERED OVER EASTERN CANADA WILL RIDGE NARROWLY SOUTHWARD DOWN THROUGH THE PIEDMONT SUNDAY... AND THIS SHOULD KEEP ENOUGH ATLANTIC MOISTURE PUMPING ACROSS THE VA/NC COAST FOR VARIABLE CLOUD COVER EAST/PARTLY CLOUDY WEST THROUGH SUNDAY. EXPECT BELOW NORMAL HIGHS SUNDAY OF 60-68... COOLER NORTHEAST... WITH PERIODS OF CLOUDS AND WITH THICKNESSES STARTING NEAR NORMAL BUT LIKELY TO HOLD STEADY OR FALL THROUGH THE DAY. -GIH && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 340 AM FRIDAY... THIS APPEARS TO BE A RELATIVELY QUIET WEATHER PERIOD. A MID LEVEL VORTEX TRACKING NE THROUGH THE NRN GREAT LAKES ON MONDAY SERVES TO BUILD UP MID LEVEL RIDGING ATOP THE SURFACE RIDGE EXTENDING FROM FAR ERN CANADA DOWN THROUGH THE CAROLINAS. THE NARROW NOSE OF COOLER TEMPERATURES SHOULD PERSIST OVER THE CWA MONDAY YIELDING BELOW NORMAL HIGHS IN THE LOW-MID 60S. ABUNDANT BOUNDARY LAYER MOISTURE WITH A LINGERING FLUX OF ATLANTIC MOISTURE SHOULD KEEP SKIES PARTLY TO MOSTLY CLOUDY THROUGH TUESDAY... AND WHILE BRIEF PERIODS OF ISENTROPIC UPGLIDE ARE POSSIBLE... THE LACK OF OTHER LIFT MECHANISMS AND THE UNCERTAINTY OF THE DEGREE OF FORCING PROVIDED BY ANY SUCH LIFT PRECLUDES INCLUDING A POP THROUGH TUESDAY. ANOTHER MID LEVEL VORTEX TRACKS NE THROUGH THE GREAT LAKES WEDNESDAY/WEDNESDAY NIGHT RESULTING IN BUILDING RIDGING OVER THE SOUTHEAST. WILL CONTINUE WITH MODIFYING TEMPERATURES SURPASSING NORMALS BY 1-2 CATEGORIES BY THURSDAY AS THICKNESSES REACH 20-30 M ABOVE NORMAL. -GIH && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 225 AM FRIDAY... WARM...MOIST FLOW OVERRUNNING COOL...NORTH TO NORTHEAST FLOW AT THE SURFACE WILL RESULT IN LIFR CONDITIONS IN LOW CLOUDS...LIGHT RAIN... DRIZZLE AND FOG EARLY THIS FRIDAY MORNING. CONDITIONS WILL GRADUALLY IMPROVE FROM THE EAST DURING THE LATE MORNING TO EARLY AFTERNOON AS A WARM FRONT WORKS WESTWARD FROM THE COAST. CONDITIONS WILL LIFT TO MVFR RWI...RDU...FAY BETWEEN 15 AND 17Z AND OVER GSO AND INT AFTER 18Z. AS THE ATMOSPHERE MIXES... AFTERNOON HEATING WILL COMBINE WITH WARM... SOUTHERLY FLOW TO GIVE A CHANCE OF SHOWERS AND THUNDERSTORMS LATE TODAY AND TONIGHT. A COLD FRONT WILL APPROACH AND MOVE ACROSS THE REGION SATURDAY. WE CAN EXPECT MVFR TO IFR CONDITIONS IN SHOWERS AND SCATTERED THUNDERSTORMS. THE COLD FRONT WILL LINGER ALONG THE COAST LATE SATURDAY THROUGH EARLY SUNDAY... RESULTING IN AS SLOW IMPROVEMENT OVER THE EASTERN TAFS THROUGH THE NIGHT. HIGH PRESSURE WILL BUILD OVER THE AREA DURING THE DAY SUNDAY AND REMAIN THROUGH TUESDAY. WE CAN EXPECT VFR CONDITIONS AS DRY AIR TAKES HOLD OF THE REGION. -RHJ && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...RHJ
AREA FORECAST DISCUSSION
NWS RALEIGH NC
640 AM EDT FRI APR 4 2008 .SYNOPSIS...COOL HIGH PRESSURE OVER THE AREA WILL GIVE WAY TO A COASTAL FRONT PUSHING INLAND THIS MORNING. AS THIS FRONT SHIFTS TO OUR NORTH AS A WARM FRONT... A SOUTHWEST FLOW WILL PUMP WARMER AIR INTO THE AREA. A COLD FRONT WILL MOVE INTO OUR REGION LATE FRIDAY NIGHT... AND PUSH SLOWLY EAST THROUGH THE AREA LATE SATURDAY. && .NEAR TERM /THROUGH TODAY/... AS OF 150 AM FRIDAY... THE PARENT HIGH FOR THIS COLD AIR DAMMING EVENT HAS SHIFTED OFFSHORE AND HAS NO MID LEVEL ANCHORING OR STRENGTHENING SUPPORT... BUT IT HAS LEFT AN IMPRESSIVE RESIDUAL COOL POOL OVER MUCH OF THE CWA. THE MODEL PERFORMANCE OF THIS MESOSCALE FEATURE IS WORRISOME: THE LATEST TEMPS IN THE TRIAD AREA ARE ONLY AROUND 40... AND EVEN THE MOST RECENT MOS GUIDANCE TEMPS THERE FOR THE CURRENT NIGHT ONLY BOTTOM THEM OUT IN THE MID 40S. AMDAR AIRCRAFT SOUNDINGS OVER THE LAST FEW HOURS ARE COLDER THAN GFS/NAM BUFR SOUNDINGS AT THE SURFACE AT BOTH GSO AND RDU. THE COASTAL FRONT HAS WORKED THROUGH THE COASTAL AREA LAST EVENING AND MID 60S ARE COMMON TO ITS EAST... HOWEVER THIS FRONT IS LIKELY TO BE SLOW HEADING INLAND. THE 925-850 MB FLOW TYPICALLY NEEDS TO HAVE A SIGNIFICANT ONSHORE-DIRECTED COMPONENT TO HELP SHOVE THE WEDGE FRONT INLAND... AND SUCH A COMPONENT IS LACKING HERE WITH FLOW IN THIS LAYER HAVING GONE MORE SRLY TO SWRLY. SO IT WILL LIKELY TAKE INSOLATION ATOP THE COOL STABLE DOME TO ERODE THE WEDGE REGIME... RESULTING IN SLOW DRAINING OF THE WEDGE AND A GRADUAL EROSION FROM THE EDGES. EROSION COULD BE DELAYED FURTHER IF THE WARM ADVECTION NEAR THE TOP OF THE INVERSION SERVES TO STRENGTHEN THE STABILITY BY INCREASING THE VERTICAL TEMP DIFFERENTIAL. THE NET RESULT WILL BE A SLOWING OF THE WARMING IN THE PIEDMONT TODAY FROM THE CURRENT FORECAST... ESPECIALLY IN THE PIEDMONT. EXPECT HIGHS OF 65-78 NW-SE... WITH HIGHS OCCURRING VERY LATE IN THE PIEDMONT. REGARDING PRECIP... ISENTROPIC UPGLIDE AROUND 285-300K HAS WANED CONSIDERABLY AND THE MEAN FLOW IS NOW ORIENTED ROUGHLY PARALLEL TO THE ISENTROPES. OTHER LIFT MECHANISMS ARE WEAK TO NONEXISTENT MUCH OF TODAY ACCORDING TO LATEST MODEL GUIDANCE... WITH A GENERALLY FLAT SWRLY MID LEVEL FLOW WITH NO DISCERNIBLE PERTURBATIONS AND UPPER JET FORCING HOLDING TO OUR WEST UNTIL AFTER SUNDOWN. LOW LEVEL MOISTURE FLUX CONVERGENCE DOES IMPROVE TODAY BUT IS FOCUSED MAINLY OVER EASTERN NC. THE LATEST WRF-ARW DEPICTS MINIMAL PATCHY RAIN THROUGH THE DAY CWA-WIDE... A TREND NOTED ON THE NAM/GFS AS WELL. HAVE REDUCED POPS THROUGH EARLY EVENING TO A 30-50% CHANCE... LOWER THIS MORNING TRENDING HIGHER LATE IN THE DAY. HAVE KEPT IN A CHANCE OF THUNDER EVERYWHERE WITH INCREASING LOW LEVEL THETA-E... LOW LEVEL JETTING INCREASING TO 40-50 KTS AT 850 MB... AND MUCAPE OF 800-1000 J/KG LATE THIS AFTERNOON OVER THE FAR SOUTHERN CWA... HOWEVER IF THE LOW LEVEL STABLE POOL HOLDS ON MUCH LONGER THAN THE MODELS INDICATE... SIGNIFICANT BUOYANCY MAY BE TOUGHER TO COME BY. -GIH && .SHORT TERM /TONIGHT THROUGH SUNDAY/... AS OF 630 AM FRIDAY... BASED ON CONSENSUS OF 06Z GFS AND ITS PREVIOUS TRENDS AND THE 00Z ECMWF INDICATING A MUCH SLOWER FRONTAL PASSAGE... HAVE RAISED POPS THROUGH SATURDAY NIGHT. STORM TOTAL RAINFALL AMOUNTS ARE LIKELY TO BE HIGHER... WIDESPREAD 1-2 INCHES WITH LOCALLY HIGHER AMOUNTS. GRIDDED AND TEXT FORECASTS WERE UPDATED ACCORDINGLY. FOR TONIGHT: THE COLD FRONT IS EXPECTED TO SLOWLY EASE EASTWARD TOWARD THE WRN MOUNTAINS SLOPES. CONVECTIVE CHANCES APPEAR TO PEAK NEAR AND JUST AFTER SUNSET... DURING THE EARLY-MID EVENING... WITH MUCAPES REACHING CLOSE TO 1000 J/KG... INCREASING UPPER DIVERGENCE... AND CURVED HODOGRAPHS WITH 850 MB WINDS REACHING 40-50 KTS AROUND 00-06Z. WILL INCLUDE SCATTERED STORMS THROUGH THE EVENING... TAPERING TO MAINLY SHOWERS OVERNIGHT WITH THE HIGHER CATEGORICAL POPS IN THE WEST CLOSER TO THE ENCROACHING COLD FRONT AND LOWER CHANCES EAST. THE THREAT OF SOME MODERATE TO HEAVY RAIN APPEARS TO RISE OVERNIGHT AS FACTORS FAVORING WARM RAIN PROCESSES IMPROVE... INCLUDING A DEEPENING LCL-TO-FREEZING-LEVEL TO 3.5 KM AND PRECIPITABLE WATER INCREASING TO 250% OF NORMAL. EXPECT LOWS TONIGHT TO RUN 59-66... WELL ABOVE MOS GUIDANCE LOWS WHICH ARE TYPICALLY A LITTLE TOO COOL JUST AHEAD OF COLD FRONTS. A GREATER RISK OF HEAVY RAIN WILL BE ON SATURDAY AS THE WAVY FRONT PUSHES SLOWLY EAST THROUGH THE AREA. THE SLOWER FRONTAL MOVEMENT OF THE ECWMF IS PREFERRED... GIVEN THAT THE MID LEVEL FLOW BECOMES NEARLY PARALLEL TO THE SURFACE FRONT WITH NO STRONG PUSH OF COLD AIR OVER THE MOUNTAINS UNTIL AFTER DARK WHEN THE MID LEVEL SHORTWAVE TROUGH NOW DIVING INTO THE WESTERN PLAINS FINALLY PUSHES INTO THE CENTRAL/SRN APPALACHIANS. PRECIPITABLE WATER VALUES NEARLY 300% OF NORMAL AND POSSIBLE TRAINING CELLS OR BANDS WILL LIKELY PUSH RAIN TOTALS TO 1-2 INCHES AND POSSIBLY HIGHER. THE OPERATIONAL MODELS HAVE NOT DONE WELL PREDICTING PRECIP AMOUNTS IN RECENT WEEKS... SO CONFIDENCE IN PRECISE PLACEMENT OF THE HEAVY RAIN RISK IS NOT HIGH. DESPITE THE DROUGHT WE`RE STILL IN... SOILS HAVE MOISTENED A BIT WITH THE LAST COUPLE OF RAIN EVENTS... AND MANY AREAS WITH STILL-HARDENED GROUND COULD SEE RAPID RUNOFF INTO CREEKS AND POOR DRAINAGE AREAS. WILL INCLUDE THIS THREAT IN THE HAZARDOUS WEATHER OUTLOOK. REGARDING THE SEVERE RISK... A SLUG OF UPPER DIVERGENCE WITHIN THE RIGHT ENTRANCE REGION OF THE JET WILL ACCOMPANY DECENT 700-500 MB LAPSE RATES NEAR 6.5 C/KM AND MODERATE MID LEVEL HEIGHT FALLS... AND IF THE COLD FRONT IS INDEED DELAYED LIKE THE ECMWF DEPICTS OVER THE FASTER GFS AND ESPECIALLY NAM... THE LOW LEVELS WILL BE MORE UNSTABLE THAN NAM/GFS FORECAST SOUNDINGS DEPICT. THIS SHORTWAVE DOES DAMPEN QUITE A BIT AS IT ENCOUNTERS THE ATLANTIC RIDGE HOWEVER AND MAY NOT CONTRIBUTE MUCH TO BROAD LIFT. WIND FIELDS LOOK GOOD WITH NEARLY 50 KTS OF 0-6 KM SHEAR AHEAD OF THE FRONT ALTHOUGH THE LOW LEVEL JET CORE WILL BE SHIFTING INTO THE COASTAL SECTIONS. THE PRIMARY THREAT STILL APPEARS TO BE FROM STRAIGHT LINE DAMAGING WINDS ESPECIALLY EAST OF HIGHWAY 1 WHERE THE NAM GIVES A MUCAPE OF 1000-1500 J/KG. EXISTING HIGHS OF 68-76 STILL LOOK REASONABLE WITH STRONG WARM ADVECTION AHEAD OF THE FRONT. AS THE FRONT SHIFTS EASTWARD LATE SATURDAY NIGHT AS INDICATED BY THE PREFERRED SLOWER ECMWF... SHOWER/STORM CHANCES WILL DIMINISH GRADUALLY FROM WEST TO EAST BUT SIGNIFICANT CLEARING WILL LIKELY HOLD OFF UNTIL SUNDAY. LOWS SATURDAY NIGHT 46-55. THE SURFACE RIDGE THAT WILL BECOME CENTERED OVER EASTERN CANADA WILL RIDGE NARROWLY SOUTHWARD DOWN THROUGH THE PIEDMONT SUNDAY... AND THIS SHOULD KEEP ENOUGH ATLANTIC MOISTURE PUMPING ACROSS THE VA/NC COAST FOR VARIABLE CLOUD COVER EAST/PARTLY CLOUDY WEST THROUGH SUNDAY. EXPECT BELOW NORMAL HIGHS SUNDAY OF 60-68... COOLER NORTHEAST... WITH PERIODS OF CLOUDS AND WITH THICKNESSES STARTING NEAR NORMAL BUT LIKELY TO HOLD STEADY OR FALL THROUGH THE DAY. -GIH && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... AS OF 340 AM FRIDAY... THIS APPEARS TO BE A RELATIVELY QUIET WEATHER PERIOD. A MID LEVEL VORTEX TRACKING NE THROUGH THE NRN GREAT LAKES ON MONDAY SERVES TO BUILD UP MID LEVEL RIDGING ATOP THE SURFACE RIDGE EXTENDING FROM FAR ERN CANADA DOWN THROUGH THE CAROLINAS. THE NARROW NOSE OF COOLER TEMPERATURES SHOULD PERSIST OVER THE CWA MONDAY YIELDING BELOW NORMAL HIGHS IN THE LOW-MID 60S. ABUNDANT BOUNDARY LAYER MOISTURE WITH A LINGERING FLUX OF ATLANTIC MOISTURE SHOULD KEEP SKIES PARTLY TO MOSTLY CLOUDY THROUGH TUESDAY... AND WHILE BRIEF PERIODS OF ISENTROPIC UPGLIDE ARE POSSIBLE... THE LACK OF OTHER LIFT MECHANISMS AND THE UNCERTAINTY OF THE DEGREE OF FORCING PROVIDED BY ANY SUCH LIFT PRECLUDES INCLUDING A POP THROUGH TUESDAY. ANOTHER MID LEVEL VORTEX TRACKS NE THROUGH THE GREAT LAKES WEDNESDAY/WEDNESDAY NIGHT RESULTING IN BUILDING RIDGING OVER THE SOUTHEAST. WILL CONTINUE WITH MODIFYING TEMPERATURES SURPASSING NORMALS BY 1-2 CATEGORIES BY THURSDAY AS THICKNESSES REACH 20-30 M ABOVE NORMAL. -GIH && .AVIATION /06Z FRIDAY THROUGH TUESDAY/... AS OF 225 AM FRIDAY... WARM... MOIST FLOW OVERRUNNING COOL... NORTH TO NORTHEAST FLOW AT THE SURFACE WILL RESULT IN LIFR CONDITIONS IN LOW CLOUDS...LIGHT RAIN... DRIZZLE AND FOG EARLY THIS FRIDAY MORNING. CONDITIONS WILL GRADUALLY IMPROVE FROM THE EAST DURING THE LATE MORNING TO EARLY AFTERNOON AS A WARM FRONT WORKS WESTWARD FROM THE COAST. CONDITIONS WILL LIFT TO MVFR RWI...RDU...FAY BETWEEN 15 AND 17Z AND OVER GSO AND INT AFTER 18Z. AS THE ATMOSPHERE MIXES... AFTERNOON HEATING WILL COMBINE WITH WARM... SOUTHERLY FLOW TO GIVE A CHANCE OF SHOWERS AND THUNDERSTORMS LATE TODAY AND TONIGHT. A COLD FRONT WILL APPROACH AND MOVE ACROSS THE REGION SATURDAY. WE CAN EXPECT MVFR TO IFR CONDITIONS IN SHOWERS AND SCATTERED THUNDERSTORMS. THE COLD FRONT WILL LINGER ALONG THE COAST LATE SATURDAY THROUGH EARLY SUNDAY... RESULTING IN AS SLOW IMPROVEMENT OVER THE EASTERN TAFS THROUGH THE NIGHT. HIGH PRESSURE WILL BUILD OVER THE AREA DURING THE DAY SUNDAY AND REMAIN THROUGH TUESDAY. WE CAN EXPECT VFR CONDITIONS AS DRY AIR TAKES HOLD OF THE REGION. -RHJ && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...HARTFIELD LONG TERM...HARTFIELD AVIATION...RHJ