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
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