Forecast Discussions mentioning "ACARS", "MDCRS", "AIRCRAFT", "TAMDAR", or "AMDAR" received at FSL on 07/20/08

AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
130 PM PDT SAT JUL 19 2008 .SYNOPSIS... INCREASING MOISTURE IN SOUTHEAST FLOW ALOFT WILL BRING A CHANCE OF THUNDERSTORMS TO THE MOUNTAINS AND DESERTS LATE TODAY THROUGH EARLY NEXT WEEK. A FEW STORMS COULD DRIFT WEST OF THE MOUNTAINS SUNDAY AND MONDAY. THE MARINE LAYER AND ONSHORE FLOW WILL CONTINUE COASTAL LOW CLOUDS AND FOG DURING THE NIGHTS AND MORNINGS...EXTENDING LOCALLY INLAND. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... MDCRS SOUNDINGS THIS AFTERNOON CONTINUE TO SHOW THE DEPTH OF THE MARINE LAYER TO BE AROUND 2500 FEET. STRATUS IS HOLDING SOLID ALONG THE COAST WITH ONLY PARTIAL CLEARING EXPECTED THROUGH THE AFTERNOON BEFORE MOVING BACK INLAND. THE EARLIER SURGE OF MOISTURE INTO THE SOUTHERN DESERTS WAS SHOWING SIGNS OF DIMINISHING WITH DEW POINTS BACK DOWN INTO THE LOW 60S AT PALM SPRINGS AND THERMAL. SOME MOISTURE IS EXPECTED TO MOVE INTO THE SOUTHERN DESERTS LATER TONIGHT INTO SUNDAY MORNING. HAVE MOSTLY FOLLOWED THE 12Z NAM GUIDANCE ALTHOUGH THE 12Z GFS MOS GUIDANCE GOES ALONG WITH THE NAM SOLUTION. 12Z MODELS CONTINUE TO BRING AN INCREASE IN MID AND HIGH LEVEL MOISTURE TO THE AREA FROM THE SOUTHEAST LATE TONIGHT INTO SUNDAY AND MONDAY...SIMILAR TO EARLIER MODEL RUNS. 12Z NAM POS BUOYANCY ENERGY GRAPHICS INDICATE VERY UNSTABLE FOR THE MOUNTAINS AND EASTERN DESERTS EARLY SUNDAY MORNING WITH ENERGY APPROACHING 1500 J/KG BY 18Z AND LIFTED INDECIES BETWEEN MINUS 4 AND MINUS 6 DURING THE PERIOD. LATER SHIFTS MAY NEED TO ISSUE A FLASH FLOOD WATCH FOR THE MOUNTAINS AND EASTERN DESERT AREAS FOR SUNDAY. MONDAY DOES NOT APPEAR TO BE AS ACTIVE WITH MOST ACTIVITY SHIFTING NORTH TO THE NORTHERN MOUNTAIN AREAS BUT STILL EXPECT SOME CONVECTION ON MONDAY. A FURTHER DECREASE IN ACTIVITY IS EXPECTED ON TUESDAY. FOR THE EXTENDED PERIOD...MODELS CONTINUE TO KEEP A RIDGE OVER THE SOUTHWEST WITH A BROAD TROUGH ALONG THE PACIFIC NORTHWEST COAST THROUGH THE PERIOD. THE RIDGE SHOULD KEEP THE AREA UNDER A SOUTHERLY FLOW ALOFT WHICH SHOULD CONTINUE TO ALLOW AFTERNOON CONVECTION OVER THE MOUNTAINS DURING THE PERIOD. TEMPERATURES SHOULD BE NEAR SEASONAL DURING THE PERIOD. ANOTHER INCREASE IN MID AND HIGH LEVEL MOISTURE IS EXPECTED LATE IN THE WEEK. && .AVIATION... 192030Z...AREAS OF BROKEN STRATUS ALONG THE IMMEDIATE COAST WILL CONTINUE THIS AFTERNOON WITH SOME AFTERNOON CUMULUS CLOUDS OVER THE MTNS AND DESERTS. SUBTROPICAL MOISTURE INCREASES TONIGHT WITH THE POTENTIAL FOR THUNDERSTORMS OVER THE MTNS AND DESERTS LATE TONIGHT AND SUN. THUNDERSTORMS WOULD PRODUCE HEAVY RAIN LOWERING VISBY AS WELL AS HAIL AND STRONG GUSTY WINDS. ON SUN THE MARINE LAYER WILL BECOME DISRUPTED BY THE INCREASING MOISTURE ALOFT AND STRATUS SHOULD CLEAR FROM COASTAL AIRPORTS BETWEEN 15-17Z. MM && .MARINE... 192030Z...A MODERATE SOUTH SWELL WILL INCREASE THROUGH SUN WITH A PERIOD OF 16 SECONDS. SURF ALONG ORANGE CO BEACHES IS FORECAST TO BE 5 TO 7 FEET WITH SETS AS HIGH AS 9 FEET. THERE WILL BE STRONG AND DANGEROUS RIP CURRENTS THROUGH EARLY NEXT WEEK. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...HIGH SURF ADVISORY FROM 9 PM THIS EVENING TO 2 AM PDT TUESDAY FOR ORANGE COUNTY COASTAL AREAS. PZ...NONE. && $$ PUBLIC...HORTON AVIATION/MARINE...MM NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
1050 AM PDT SAT JUL 19 2008 ...UPDATED AVIATION DISCUSSION... .SHORT TERM...(TODAY-MONDAY) LOW CLOUD REGIME VERY SIMILAR TO 24-HOURS AGO. LATEST ACARS SOUNDING NEAR KLAX INDICATED MARINE LAYER NEAR 1100 FT DEEP. WITH EDDY IN PLACE...EXPECT MARINE LAYER TO DEEPEN TO AT LEAST 1500 FT LATER THIS MORNING. STRATUS ALREADY ACROSS LA COUNTY VALLEYS AND PORTIONS OF THE VENTURA COUNTY VALLEYS. CURRENT LAX-DAG SFC GRAD IS ALSO SIMILAR TO YESTERDAY...HOWEVER WRF MODEL STRENGTHENS ONSHORE GRAD TO NEAR +8.9 MB THIS AFTERNOON AND A WEAK UPPER LVL LOW OFF THE SO CAL COAST WILL HELP TO REINFORCE LOW CLOUDS ACROSS THE LA/VTU/SBA COASTAL AND VALLEY AREAS. WITH A RELATIVE STRONG INVERSION IN PLACE...LOW CLOUDS SHOULD BURNOFF BY MID MORNING IN VALLEY LOCATIONS...THEN BY MID AFTERNOON ACROSS THE COASTAL PLAIN. HOWEVER...THE BEACHES COULD REMAIN MOSTLY CLOUDY MOST OF THE DAY. TEMPS SHOULD BE A DEGREE OR TWO COOLER TODAY IN MOST AREAS WITH STRONGER ONSHORE PUSH. THE WEAK CUTOFF LOW OFF THE SO CAL COAST FILLS IN QUICKLY THIS AFTERNOON AS A BROADER TROF TO THE NORTHWEST PULLS IT IN. THERE WILL CONTINUE TO BE A STRONG MARINE INFLUENCE ACROSS THE COASTAL AREAS ON SUNDAY AS THERMAL TROF STRENGTHENS ACROSS THE EASTERN CAL DESERTS. TO THE EAST...UPPER LVL HIGH BEGINS TO RE-ESTABLISH ACROSS THE 4-CORNERS REGION TODAY WHICH SHOULD OPEN THE GATEWAY FOR MID-LVL MOISTURE TO PUSH IN FROM AZ/MEXICO. GFS/WRF/ECMWF INDICATED ABUNDANT 500-700 MB MOISTURE MOVING INTO SE CAL LATE TODAY. NOT EXPECTING ANY CONVECTION ACROSS THE FORECAST AREA AS THE BULK OF MOISTURE STAYS TO THE EAST TODAY. HOWEVER ON SUNDAY...MONSOONAL FRONT (850 MB DEWPOINTS OVER 8 DEGREES C) BEGIN TO MOVE ACROSS ERN LA COUNTY. PWAT VALUES OF 1.5" WILL BE IN PLACE ACROSS LA COUNTY AS WELL. IT IS TOO EARLY TO INDICATE ANY INVERTED TROFS OR DEFORMATION ZONES MOVING AROUND THE HIGH TO HELP KICK OFF TSTMS...BUT AFTERNOON CONVECTIVE TEMPS SHOULD INITIATE SOME STORMS ACROSS THE MTNS OF LA/VTU COUNTIES AND THE ANTELOPE VALLEY. EXPECT THE SAME PATTERN ON MONDAY...WITH A BETTER CHANCE OF TSTMS ACROSS VTU/SBA COUNTY MTNS AS WELL. ONE CAVEAT...IF TOO MUCH MID LVL CLOUDINESS OCCURS...SFC HEATING COULD BE LIMITED AND TSTMS WILL HAVE A TOUGH TIME GETTING STARTED. WITH HIGH PWAT VALUES...AND WEAK STEERING WINDS AT 500MB...THERE COULD BE A THREAT OF FLASH FLOODING ACROSS PORTIONS OF THE MTNS AND ANTELOPE VALLEY SUN AND MON. LATER SHIFTS WILL MONITOR AS NEW MODEL RUNS COME IN. .LONG TERM...(TUE-FRI) BOTH THE GFS AND ECMWF ARE IN AGREEMENT AS UPPER LVL TROF MOVES EAST WHILE THE UPPER HIGH ACROSS THE 4-CORNERS REGION PERSISTS FOR THE MOST PART. TEMPS SHOULD BE SLIGHTLY COOLER ACROSS THE NRN PART OF THE FORECAST AREA DUE TO TROF PASSING TO THE NORTH. BY WED...IT IS DIFFICULT TO SAY HOW THE FLOW AROUND THE HIGH WILL AFFECT THE FORECAST AREA AS THE MODELS BEGIN TO GET OUT OF PHASE A BIT. BOTH MODELS DO ELONGATE THE HIGH TO PUSH FARTHER WEST OVER THE ERN PAC. THIS COULD POTENTIALLY SHUT DOWN THE MONSOONAL FLOW FOR A SHORT TIME BUT AS WE SAW LAST WEEK...SOME RESIDUAL MOISTURE AND SUNNY SKIES COULD POP UP A FEW TSTMS WED-FRI. EXPECT INLAND TEMPS TO REMAIN NEAR NORMAL WITH A FEW DEGREES OF WARMING BY THU-FRI AS THICKNESS LVLS RISE A BIT. TEMPS SHOULD REMAIN RELATIVELY NORMAL ACROSS THE COASTAL AREAS AS WELL DUE TO CONTINUED MARINE INFLUENCE ACROSS THE COASTAL SECTIONS. LOW CLOUDS FROM THE MARINE LAYER COULD BE DISRUPTED THROUGH THE PERIOD DUE TO MID LEVEL MOISTURE MOVING WESTWARD. && .AVIATION...19/1750Z. MARINE LAYER UP TO 022 THIS MORNING...WITH SOLID MVFR STRATUS DECK OVER MOST OF THE COASTAL SIDE OF THE MTNS. MOST SITES SHOULD SEE CLEARING BY 20Z...BUT LOW CONFIDENCE OF CLEARING AT IMMEDIATE COASTAL SITES LIKE KLAX KOXR AND KSBA. THESE SITES SHOULD SEE A FEW OBS OF VFR BETWEEN 20Z AND 02Z...BUT STRATUS SHOULD SURGE IN TO STAY EARLIER THAN LAST NIGHT. MID LEVEL MOISTURE WILL BEGIN TO STREAM IN OVERNIGHT...WHICH WILL LIKELY ALTER THE STRATUS...BUT LOW CONFIDENCE IF IT IS ENOUGH TO BREAK IT UP. SHOULD IMPROVE FLIGHT CATS A BIT FROM LAST NIGHT NONETHELESS. KLAX...MODERATE CONFIDENCE OF MVFR CIGS THROUGH 20Z...WITH LOW CONFIDENCE FOR IMPROVEMENT BETWEEN 20Z AND 02Z. STRATUS SHOULD SURGE BACK IN EARLY TONIGHT...WITH AN ONSET WINDOW BETWEEN 23Z AND 04Z. KBUR...MODERATE CONFIDENCE IN VFR BY 20Z...BUT HZ MAY LINGER AN HOUR OR TWO LATER. VFR SHOULD PREVAIL AFTERWARD THROUGH THE EVENING. STRATUS SHOULD THEN RETURN INITIALLY AT IFR...WITH AN ONSET TIME BETWEEN 06Z AND 12Z. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXCWFLOX). HIGH RIP CURRENT RISK (SEE LAXSRFLOX). && $$ PUBLIC...KAPLAN AVIATION...KITTELL WWW.WEATHER.GOV/LOSANGELES
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
900 AM PDT FRI JUL 18 2008 .SHORT TERM...(TODAY-SUNDAY) FORECAST IN GOOD SHAPE THIS MORNING. MARINE LAYER HAS DEEPENED TO NEARLY 1500 FT...AS STRATUS WAS ABLE TO SURGE INTO THE LA AND SALINAS VALLEYS THIS MORNING. THIS DEEPER MARINE LAYER SHOULD HELP TEMPS COOL A BIT FROM YESTERDAY OVER THE COASTAL AND VALLEY AREAS...BUT WITH UNCHANGED THICKS THE MTNS AND DESERTS SHOULD RUN ABOUT THE SAME. WIND-WISE...WE DID HAVE SOME BREEZY NORTHERLY WINDS OVER THE LA/VTU MTNS LAST NIGHT...AND THAT SHOULD RETURN TONIGHT...ALBEIT WEAKER. OVER SBA COUNTY...12Z MODELS HAVE BACKED OFF ON THE SBA-SMX GRAD QUITE A BIT. THE GRAD CURRENTLY IS STRONGER THAN 24 HRS AGO...SO DID ADJUST THE WINDS DOWN A BIT...BUT NOT AS LOW AS THE NAM IS SUGGESTING. ...FROM PREVIOUS DISCUSSION... EXPECT THE WARMEST TEMPS ACROSS THE ANTELOPE VALLEY REACHING LOWER TRIPLE DIGITS ONCE AGAIN TODAY. WARMEST VALLEY LOCATIONS SHOULD REMAIN IN THE UPPER 90S OVER THE NEXT FEW DAYS. MARINE LAYER INFLUENCE WILL KEEP THE COASTAL AREAS AND VALLEYS NEAR NORMAL OVER THE NEXT FEW DAYS. EXPECT CONTINUED LOW CLOUDS AND FOG REGIME ACROSS THE COASTAL AREAS WITH SOME PATCHY LOW CLOUDS POSSIBLY CREEPING IN THE COASTAL VALLEYS THROUGH SUNDAY. TEMPS WILL BE A DEGREE OR TWO COOLER ON SUNDAY AS BOUNDARY LAYER TEMPS DROP SLIGHTLY AND MODERATE ONSHORE FLOW CONTINUES THROUGH SUNDAY. BY SUNDAY...THE UPPER HIGH THAT WAS OVER THE EASTERN PAC BEGINS TO GET PUSHED EASTWARD AHEAD OF AN UPPER TROF PUSHING ACROSS NRN CAL. AS THIS OCCURS...HIGH PRESSURE BUILDS BACK OVER THE 4 CORNERS REGION WHICH WILL OPEN THE CHANCE OF MID LEVEL MOISTURE TO ADVECT IN ACROSS THE LOWER COLORADO RIVER VALLEY BRINGING A SLIGHT CHANCE TO THE LA COUNTY MTNS. WENT AHEAD AND ADDED 20 PERCENT POPS TO THE LA/VTU COUNTY MOUNTAIN ZONES. WITH BETTER 700 MB MOISTURE ON MON-WED...MORE CONFIDENCE FOR CONVECTION ACROSS THE MOUNTAINS AND ANTELOPE VALLEY BY EARLY NEXT WEEK. .LONG TERM...(MONDAY-THURSDAY) BOTH GFS AND ECMWF ARE IN DECENT AGREEMENT THAT THE UPPER HIGH ACROSS THE 4 CORNERS WILL PERSIST THROUGH MID WEEK. BOTH GFS AND ECMWF ADVERTISE PLENTY OF 700 MB MOISTURE MONDAY AND TUE. THE GFS THEN PUSHES MOST OF THE MOISTURE TO THE EAST...BUT THE ECM CONTINUES TO BRING PLENTY OF 700 MB MOISTURE ACROSS OUR AREA THROUGH THU. THEREFORE THERE WILL BE A DECENT CHANCE OF THUNDERSTORMS ONCE AGAIN ACROSS THE LA/VTU/SBA COUNTY MOUNTAINS...ANTELOPE VALLEY AND POSSIBLY THE VALLEYS IF UPPER STEERING WINDS CAN PUSH STORMS INTO VALLEYS. WENT AHEAD AND ONLY PUT SLIGHT CHANCE WORDING THROUGH TUE EVENING SINCE LATER MODEL RUNS COULD BACK-OFF CONVECTION PATTERN LATE IN WEEK. ONLY SLIGHT FLUCTUATIONS IN HIGH TEMPS THROUGH THE PERIOD...BUT MONSOONAL MOISTURE COULD MAKE NIGHT TIME TEMPS UNCOMFORTABLE ACROSS INLAND AREAS INCLUDING THE FOOTHILLS ADJACENT TO THE LA/VTU COUNTY VALLEYS. LOW CLOUDS WOULD LIKELY ONLY AFFECT THE COASTAL AREAS AS MONSOONAL FLOW COULD DISRUPT MARINE LAYER THROUGH THE PERIOD. && .AVIATION...18/1200Z LATEST AMDAR SOUNDINGS INDICATE MARINE INVERISON AROUND 1400 FEET THIS MORNING. SATELLITE/SURFACE OBS INDICATE WIDESPREAD STRATUS/FOG ACROSS KSBP/KSMX/KPRB. SOUTH OF POINT CONCEPTION...STRATUS IS FILLING IN NICELY ACROSS COASTAL AREAS OF LAX/VTU COUNTIES. ANY MARINE LAYER THAT DEVELOPS IS EXPECTED TO BURNOFF BY LATE MORNING. KLAX...HIGH CONFIDENCE IN 12Z TAF PACKAGE. THERE IS A SLIGHT CHANCE THAT THE IFR CIGS/VSBYS COULD BREAKOUT BEFORE 18Z. KBUR...MODERATE CONFIDENCE IN 12Z TAF AS STRATUS IS POISED JUST SOUTH OF THE AIRFIELD. THERE IS A CHANCE THAT IFR/LIFR CONDS COULD AFFECT THE AIRFIELD AROUND SUNRISE. IF ANY STRATUS WOULD GET INTO THE AIRFIELD...IT WOULD BE EXPECTED TO BURN OFF VERY QUICKLY LATER THIS MORNING. LOW CONFIDENCE IN 08Z RETURN OF MARINE LAYER TONIGHT. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXCWFLOX). && $$ PUBLIC...KITTELL/KAPLAN AVIATION...THOMPSON WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION...CORRECTION
NWS SAN DIEGO CA
853 AM PDT FRI JUL 18 2008 .SYNOPSIS... THE MARINE LAYER DEPTH WAS NEAR 2200 FEET AND A STRONG INVERSION WILL KEEP THE CLOUDS FROM CLEARING ALONG THE COAST UNTIL LATE MORNING TODAY. A MOSTLY SUNNY AND THUNDERSTORM FREE DAY IS EXPECTED ELSEWHERE ACROSS SOUTHWEST CALIFORNIA. A STRONG SURGE OF MONSOON MOISTURE IS LIKELY THIS WEEKEND WITH A RETURN OF THUNDERSTORMS OVER THE MOUNTAINS AND DESERTS BY SUNDAY AND CONTINUING THROUGH THE MIDDLE EARLY NEXT WEEK. SOME OF THESE MAY MOVE WEST ACROSS THE VALLEYS ON SUNDAY. THE MARINE LAYER DEPTH WILL SHRINK TO 1200 FEET AND LOW CLOUDS AND FOG SHOULD BE CONFINED TO THE COASTS AND LOWER WESTERN VALLEYS DURING THE LATE NIGHT AND EARLY MORNING HOURS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (TODAY THROUGH SUNDAY)... THREE WEATHER CONCERNS DURING THIS PERIOD...THE DEPTH OF THE MARINE LAYER AND STRATUS BURN OFF/RETURN TIMES...THE RENEWED SURGE OF MONSOON MOISTURE...AND THE BUILDING SOUTH SWELL. MARINE LAYER HAS INCREASED SLIGHTLY FROM YESTERDAY...WHEN IT WAS CLOSE TO 2000 FEET DEEP...TO AROUND 2200 FEET DEEP THIS MORNING PER MORNING SOUNDING FROM KNKX AND THE MESONET OBSERVATIONS FROM FOOTHILLS AND UPPER VALLEYS. PIREP W OF ONTARIO 2200 FEET AGREES WITH SOUNDING. VISIBLE SATELLITE IMAGERY OVER SAN DIEGO COUNTY INDICATES STRATUS COVERING TERRAIN BELOW 1900 FEET ELEVATION. METARS SHOWING FAIRLY UNIFORM CLOUD BASES AROUND 1000 FT SO NORTH ISLAND RULE OF THUMB WOULD SAY CLEARING AT THE COAST BETWEEN 1030 AND NOON PDT BASED ON 1 HOUR AFTER SUNRISE FOR EVERY 200 FEET OF CLOUD THICKNESS. THIS LATER CLEARING WOULD ALSO BE SUPPORTED BY THE STRONGER SUBSIDENCE INVERSION THIS MORNING. ABOVE THE MARINE LAYER THERE HAS BEEN SIGNIFICANT DRYING IN THE 2500-10000 FOOT LAYER. THERE ARE ALSO SOME UPPER LEVEL CONVECTIVE DEBRIS CLOUDS PRESENT ABOVE THIS LAYER MOVING SOUTHWEST ACROSS RIVERSIDE COUNTY AND THEN SOUTHEASTWARD ACROSS SAN DIEGO COUNTY DUE TO THE CIRCULATION AROUND THE UPPER TROUGH/LOW THAT MOVED NORTHEAST AND EAST ACROSS THE REGION YESTERDAY/LAST NIGHT. THE HIGH PRESSURE RIDGE..WHOSE AXIS IS STILL TO THE NORTHWEST OF THE AREA WILL SHIFT SOUTHWARD ACROSS THE AREA TODAY/TONIGHT WHICH SHOULD CAUSE THE THE SUBSIDENCE INVERSION TO LOWER TODAY/TONIGHT AND STRENGTHEN A LITTLE MORE BEFORE WEAKENING ON SATURDAY. BASED ON NAM12 MODEL CROSS SECTION TRENDS AFTER BASELINING TO THIS MORNINGS OBSERVATIONS...MARINE LAYER DEPTH SHOULD LOWER TO 1500 FEET THIS AFTERNOON/EVENING AND TO AROUND 1000 FEET BY SATURDAY MORNING. CROSS SECTIONS SHOW LAYER MEAN RH 96-100 PERCENT SO THICK STRATUS CLOUD LAYER LIKELY WITH MORE OF THE LOWER VALLEYS/COASTAL MESAS IMPACTED BY DENSE FOG LATE EVENING/OVERNIGHT. FOR SATURDAY NIGHT/SUNDAY MOIST UNSTABLE AIR MASS ALOFT EXPECTED TO INHIBIT STRATUS FORMATION...SEE BELOW. THE NEXT WEATHER PROBLEM TO ADDRESS IS THE RETURN OF MONSOON MOISTURE THIS WEEKEND. A MONSTER MESOSCALE CONVECTIVE COMPLEX MOVED SOUTHWEST ACROSS THE MEXICAN STATES OF SOUTHERN SONORA AND SINALOA LAST NIGHT AND THE REMNANTS ARE SITTING OVER THE SOUTHERN GULF OF CALIFORNIA THIS MORNING. WITH THE UPPER TROUGH APPROACHING THE NORTHERN/CENTRAL CALIFORNIA COAST TODAY AND PUSHING SLOWLY INLAND SATURDAY AND SUNDAY...A CLEFT IN THE RIDGE IS MADE WITH SOUTHEAST DEVELOPING ALOFT ON SATURDAY AND STRONG SOUTHEAST FLOW...25-40 KTS...IN THE LOW LEVELS UP THE GULF OF CALIFORNIA. STAGE APPEARS SET FOR A STRONG SURGE OF MONSOON MOISTURE PUSHING UP SALTON SEA/COACHELLA VALLEY/MORONGO VALLEY/YUCCA VALLEY AND INTO JOHNSON/LUCERNE VALLEYS SATURDAY EVENING. ONLY THING THAT MIGHT INHIBIT CONVECTION ON SUNDAY WOULD BE EXTENSIVE DEBRIS CLOUDS FROM SATURDAY NIGHTS CONVECTION. WILL PROBABLY TWEAK CURRENT WEATHER GRIDS TO ADD CHANCE OF THUNDERSHOWERS FOR SATURDAY EVENING OVER LOWER DESERT AREAS AND SPRINKLES FOR EARLY SUNDAY MORNING OVER MOUNTAINS/DESERTS FOR DISSIPATING OVERNIGHT CONVECTION...AS WELL AS UP POPS OVER INLAND EMPIRE/SAN DIEGO COUNTY VALLEYS FOR SUNDAY EVENING/MONDAY. THIRD PROBLEM...WAMIII MODEL IS KNOWN FOR FLATTENING AMPLITUDE AND MISSING TIMING OF ARRIVING SOUTHERN HEMISPHERE SWELLS. IT USUALLY GETS THE DIRECTION AND THE PERIOD CORRECT THOUGH. THE RELATIVELY STEEP APPROACH ANGLE...190 DEGREES...MEANS ORANGE COUNTY AND ONLY A FEW PARTS OF SAN DIEGO COUNTY WILL BE AFFECTED. THE LONG PERIOD INDICATES A SIGNIFICANT AMOUNT OF SHOALING WILL OCCUR WITH SURF HEIGHTS EASILY DOUBLE THE SWELL HEIGHT ON BEACHES WITH STEEP SLOPE AND DIRECTLY FACING THE ARRIVING SWELL. RELAYING STRICTLY ON MODEL GUIDANCE WILL LIKELY RESULT IN UNDERFORECASTING OF SURF HEIGHTS AT THESE BEACHES BUT PROBABLY OVERFORECASTING AT THE WEST FACING BEACHES SINCE MOST OF THE SWELL ENERGY WILL PASS BY TO THE NORTH AND ONLY A THIRD TO A QUARTER OF IT WILL BE REFRACTED TOWARDS THESE BEACHES. && .LONG TERM MONDAY THROUGH THURSDAY... AFTER THAT MIGHT BE OVERFORECASTING CONTINUOUS THREAT OF THUNDERSTORMS OVER THE MOUNTAINS/DESERTS INTO THURSDAY. IT APPEARS THE PATTERN IS NOT TOTALLY ANALOGOUS TO RECENT PROLONGED BOUT OF THUNDERSTORMS OVER MOUNTAINS/DESERTS. GFS MODEL FOR AT LEAST LAST THREE RUNS IS SHOWING DRYING SOUTHWEST FLOW RETURNING TUESDAY AND WEDNESDAY IN THE 850-700 MB LAYER. AFTER WHICH SOUTHEAST FLOW RETURNS AS ANOTHER TROPICAL WAVE PASSES BY TO THE SOUTH. IF TIME PERMITS AND 12Z GFS MODEL CONTINUES SUPPORT FOR THIS DRYING PERIOD...WILL MODIFY TUESDAY/WEDNESDAY WEATHER/POPS/SKY COVER GRIDS ACCORDINGLY. FROM PREVIOUS DISCUSSION...A SHALLOW MARINE LAYER WILL BRING AREAS OF NIGHT AND MORNING COASTAL LOW CLOUDS AND FOG EXTENDING LOCALLY INLAND. COVERAGE EARLY IN THE WEEK MAY BE FAIRLY PATCHY AT TIMES DUE TO THE DISRUPTIVE EFFECTS OF THE MONSOONAL MOISTURE. && .FIRE WEATHER... HAD ISSUED AN EARLIER CORRECTION TO THE DISCUSSION IN THE FIRE WEATHER FORECAST. THE STRONG DRYING TREND IN THE 2500-10000 FOOT LAYER MENTIONED IN THE FIRST PARAGRAPH ABOVE AS WELL AS THE LOWERING OF THE SUBSIDENCE INVERSION TO 1000 FEET TONIGHT...MEANS MUCH LOWER HUMIDITY TODAY AND SATURDAY WITH VERY POOR RECOVERY TONIGHT OVER THE MOUNTAINS. THE CURRENT RH GRIDS DO HAVE A DRYING TREND BUT MIGHT NOT BE NOT STRONG ENOUGH. WILL ADJUST THE DEWPOINT AND RH GRIDS LATER THIS MORNING AND ISSUE AN THE AFTERNOON NARRATIVE FIRE WEATHER FORECAST A LITTLE EARLIER THAN USUAL...BY 1300 PDT TO GET THESE CHANGES OUT TO THE DISPATCH CENTERS. THIS DRYING TREND IS RELATIVELY SHORT LIVED...BASICALLY TODAY THROUGH SATURDAY...AFTER WHICH A SIGNIFICANT MOISTENING TREND OCCURS DUE TO THE STRONG SURGE OF MONSOON MOISTURE MENTIONED IN PARAGRAPH TWO ABOVE. MOST IF NOT ALL OF THESE THUNDERSTORMS EXPECTED TO BE ACCOMPANIED BY WETTING RAINS. && .AVIATION... 181430Z...MDCRS SOUNDINGS THIS MORNING PLACE THE MARINE LAYER DEPTH AROUND 1800 FEET...SLIGHTLY LOWER THAN ON THURSDAY. EXPECT LITTLE CHANGE IN THE MARINE LAYER DEPTH THROUGH THE WEEKEND. A WEAK COASTAL EDDY SHOULD HELP MAINTAIN THE MARINE LAYER THROUGH THE WEEKEND. STRATUS WITH BASES AROUND 1000 FEET MSL SHOULD PULL BACK TO THE COAST BETWEEN 15Z AND 17Z. LIMITED BREAKUP OF THE STRATUS ALONG THE IMMEDIATE COAST IS EXPECTED TODAY. STRATUS SHOULD SPREAD BACK INLAND OVER THE COASTAL VALLEY AND MESAS BETWEEN SUNSET AND 06Z AND THE WESTERN INLAND VALLEY AREAS BETWEEN MIDNIGHT AND 10Z. STRATUS IS NOT EXPECTED TO REACH KONT TONIGHT BUT COULD GET TO KCNO. ABOVE THE MARINE LAYER...EXCEPT FOR SOME AFTERNOON CU/TCU OVER THE MOUNTAINS DURING THE AFTERNOONS...A MOSTLY CLEAR SKY WITH UNRESTRICTED VISIBILITIES WILL CONTINUE THROUGH SATURDAY. MID AND HIGH LEVEL MOISTURE MOVING IN FROM THE SOUTHEAST ON SUNDAY COULD BRING TSTMS TO THE MOUNTAINS AND DESERTS ON SUNDAY. MAX TEMPS FOR KPSP AND KTRM FOR TODAY AND SAT...42 TO 44C. HORTON && .MARINE... A MODERATE SOUTH SWELL WILL BEGIN TO MOVE INTO THE COASTAL AREAS TODAY...INCREASING THROUGH SUNDAY. THE PERIOD WILL INCREASE TO 19 SECONDS ON SATURDAY WITH THE PEAK OF THE SWELL EXPECTED ON SUNDAY WITH A PERIOD DROPPING TO 16 SECONDS BY SUNDAY AFTERNOON. SURF IS FORECAST TO BE UP TO 3 TO 6 FEET ON SATURDAY WITH SETS TO 7 FEET OR HIGHER MAINLY IN ORANGE COUNTY SUNDAY. THERE WILL BE STRONG AND DANGEROUS RIP CURRENTS DURING THE WEEKEND. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC/FIRE WEATHER...BALFOUR AVIATION/MARINE...HORTON NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION...CORRECTION
NWS SAN DIEGO CA
85 AM PDT FRI JUL 18 2008 .SYNOPSIS... THE MARINE LAYER DEPTH WAS NEAR 2200 FEET AND A STRONG INVERSION WILL KEEP THE CLOUDS FROM CLEARING ALONG THE COAST UNTIL LATE MORNING TODAY. A MOSTLY SUNNY AND THUNDERSTORM FREE DAY IS EXPECTED ELSEWHERE ACROSS SOUTHWEST CALIFORNIA. A STRONG SURGE OF MONSOON MOISTURE IS LIKELY THIS WEEKEND WITH A RETURN OF THUNDERSTORMS OVER THE MOUNTAINS AND DESERTS BY SUNDAY AND CONTINUING THROUGH THE MIDDLE EARLY NEXT WEEK. SOME OF THESE MAY MOVE WEST ACROSS THE VALLEYS ON SUNDAY. THE MARINE LAYER DEPTH WILL SHRINK TO 1200 FEET AND LOW CLOUDS AND FOG SHOULD BE CONFINED TO THE COASTS AND LOWER WESTERN VALLEYS DURING THE LATE NIGHT AND EARLY MORNING HOURS. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (TODAY THROUGH SUNDAY)... THREE WEATHER CONCERNS DURING THIS PERIOD...THE DEPTH OF THE MARINE LAYER AND STRATUS BURN OFF/RETURN TIMES...THE RENEWED SURGE OF MONSOON MOISTURE...AND THE BUILDING SOUTH SWELL. MARINE LAYER HAS INCREASED SLIGHTLY FROM YESTERDAY...WHEN IT WAS CLOSE TO 2000 FEET DEEP...TO AROUND 2200 FEET DEEP THIS MORNING PER MORNING SOUNDING FROM KNKX AND THE MESONET OBSERVATIONS FROM FOOTHILLS AND UPPER VALLEYS. PIREP W OF ONTARIO 2200 FEET AGREES WITH SOUNDING. VISIBLE SATELLITE IMAGERY OVER SAN DIEGO COUNTY INDICATES STRATUS COVERING TERRAIN BELOW 1900 FEET ELEVATION. METARS SHOWING FAIRLY UNIFORM CLOUD BASES AROUND 1000 FT SO NORTH ISLAND RULE OF THUMB WOULD SAY CLEARING AT THE COAST BETWEEN 1030 AND NOON PDT BASED ON 1 HOUR AFTER SUNRISE FOR EVERY 200 FEET OF CLOUD THICKNESS. THIS LATER CLEARING WOULD ALSO BE SUPPORTED BY THE STRONGER SUBSIDENCE INVERSION THIS MORNING. ABOVE THE MARINE LAYER THERE HAS BEEN SIGNIFICANT DRYING IN THE 2500-10000 FOOT LAYER. THERE ARE ALSO SOME UPPER LEVEL CONVECTIVE DEBRIS CLOUDS PRESENT ABOVE THIS LAYER MOVING SOUTHWEST ACROSS RIVERSIDE COUNTY AND THEN SOUTHEASTWARD ACROSS SAN DIEGO COUNTY DUE TO THE CIRCULATION AROUND THE UPPER TROUGH/LOW THAT MOVED NORTHEAST AND EAST ACROSS THE REGION YESTERDAY/LAST NIGHT. THE HIGH PRESSURE RIDGE..WHOSE AXIS IS STILL TO THE NORTHWEST OF THE AREA WILL SHIFT SOUTHWARD ACROSS THE AREA TODAY/TONIGHT WHICH SHOULD CAUSE THE THE SUBSIDENCE INVERSION TO LOWER TODAY/TONIGHT AND STRENGTHEN A LITTLE MORE BEFORE WEAKENING ON SATURDAY. BASED ON NAM12 MODEL CROSS SECTION TRENDS AFTER BASELINING TO THIS MORNINGS OBSERVATIONS...MARINE LAYER DEPTH SHOULD LOWER TO 1500 FEET THIS AFTERNOON/EVENING AND TO AROUND 1000 FEET BY SATURDAY MORNING. CROSS SECTIONS SHOW LAYER MEAN RH 96-100 PERCENT SO THICK STRATUS CLOUD LAYER LIKELY WITH MORE OF THE LOWER VALLEYS/COASTAL MESAS IMPACTED BY DENSE FOG LATE EVENING/OVERNIGHT. FOR SATURDAY NIGHT/SUNDAY MOIST UNSTABLE AIR MASS ALOFT EXPECTED TO INHIBIT STRATUS FORMATION...SEE BELOW. THE NEXT WEATHER PROBLEM TO ADDRESS IS THE RETURN OF MONSOON MOISTURE THIS WEEKEND. A MONSTER MESOSCALE CONVECTIVE COMPLEX MOVED SOUTHWEST ACROSS THE MEXICAN STATES OF SOUTHERN SONORA AND SINALOA LAST NIGHT AND THE REMNANTS ARE SITTING OVER THE SOUTHERN GULF OF CALIFORNIA THIS MORNING. WITH THE UPPER TROUGH APPROACHING THE NORTHERN/CENTRAL CALIFORNIA COAST TODAY AND PUSHING SLOWLY INLAND SATURDAY AND SUNDAY...A CLEFT IN THE RIDGE IS MADE WITH SOUTHEAST DEVELOPING ALOFT ON SATURDAY AND STRONG SOUTHEAST FLOW...25-40 KTS...IN THE LOW LEVELS UP THE GULF OF CALIFORNIA. STAGE APPEARS SET FOR A STRONG SURGE OF MONSOON MOISTURE PUSHING UP SALTON SEA/COACHELLA VALLEY/MORONGO VALLEY/YUCCA VALLEY AND INTO JOHNSON/LUCERNE VALLEYS SATURDAY EVENING. ONLY THING THAT MIGHT INHIBIT CONVECTION ON SUNDAY WOULD BE EXTENSIVE DEBRIS CLOUDS FROM SATURDAY NIGHTS CONVECTION. WILL PROBABLY TWEAK CURRENT WEATHER GRIDS TO ADD CHANCE OF THUNDERSHOWERS FOR SATURDAY EVENING OVER LOWER DESERT AREAS AND SPRINKLES FOR EARLY SUNDAY MORNING OVER MOUNTAINS/DESERTS FOR DISSIPATING OVERNIGHT CONVECTION...AS WELL AS UP POPS OVER INLAND EMPIRE/SAN DIEGO COUNTY VALLEYS FOR SUNDAY EVENING/MONDAY. THIRD PROBLEM...WAMIII MODEL IS KNOWN FOR FLATTENING AMPLITUDE AND MISSING TIMING OF ARRIVING SOUTHERN HEMISPHERE SWELLS. IT USUALLY GETS THE DIRECTION AND THE PERIOD CORRECT THOUGH. THE RELATIVELY STEEP APPROACH ANGLE...190 DEGREES...MEANS ORANGE COUNTY AND ONLY A FEW PARTS OF SAN DIEGO COUNTY WILL BE AFFECTED. THE LONG PERIOD INDICATES A SIGNIFICANT AMOUNT OF SHOALING WILL OCCUR WITH SURF HEIGHTS EASILY DOUBLE THE SWELL HEIGHT ON BEACHES WITH STEEP SLOPE AND DIRECTLY FACING THE ARRIVING SWELL. RELAYING STRICTLY ON MODEL GUIDANCE WILL LIKELY RESULT IN UNDERFORECASTING OF SURF HEIGHTS AT THESE BEACHES BUT PROBABLY OVERFORECASTING AT THE WEST FACING BEACHES SINCE MOST OF THE SWELL ENERGY WILL PASS BY TO THE NORTH AND ONLY A THIRD TO A QUARTER OF IT WILL BE REFRACTED TOWARDS THESE BEACHES. && .LONG TERM MONDAY THROUGH THURSDAY... AFTER THAT MIGHT BE OVERFORECASTING CONTINUOUS THREAT OF THUNDERSTORMS OVER THE MOUNTAINS/DESERTS INTO THURSDAY. IT APPEARS THE PATTERN IS NOT TOTALLY ANALOGOUS TO RECENT PROLONGED BOUT OF THUNDERSTORMS OVER MOUNTAINS/DESERTS. GFS MODEL FOR AT LEAST LAST THREE RUNS IS SHOWING DRYING SOUTHWEST FLOW RETURNING TUESDAY AND WEDNESDAY IN THE 850-700 MB LAYER. AFTER WHICH SOUTHEAST FLOW RETURNS AS ANOTHER TROPICAL WAVE PASSES BY TO THE SOUTH. IF TIME PERMITS AND 12Z GFS MODEL CONTINUES SUPPORT FOR THIS DRYING PERIOD...WILL MODIFY TUESDAY/WEDNESDAY WEATHER/POPS/SKY COVER GRIDS ACCORDINGLY. FROM PREVIOUS DISCUSSION...A SHALLOW MARINE LAYER WILL BRING AREAS OF NIGHT AND MORNING COASTAL LOW CLOUDS AND FOG EXTENDING LOCALLY INLAND. COVERAGE EARLY IN THE WEEK MAY BE FAIRLY PATCHY AT TIMES DUE TO THE DISRUPTIVE EFFECTS OF THE MONSOONAL MOISTURE. && .FIRE WEATHER... HAD ISSUED AN EARLIER CORRECTION TO THE DISCUSSION IN THE FIRE WEATHER FORECAST. THE STRONG DRYING TREND IN THE 2500-10000 FOOT LAYER MENTIONED IN THE FIRST PARAGRAPH ABOVE AS WELL AS THE LOWERING OF THE SUBSIDENCE INVERSION TO 1000 FEET TONIGHT...MEANS MUCH LOWER HUMIDITY TODAY AND SATURDAY WITH VERY POOR RECOVERY TONIGHT OVER THE MOUNTAINS. THE CURRENT RH GRIDS DO HAVE A DRYING TREND BUT MIGHT NOT BE NOT STRONG ENOUGH. WILL ADJUST THE DEWPOINT AND RH GRIDS LATER THIS MORNING AND ISSUE AN THE AFTERNOON NARRATIVE FIRE WEATHER FORECAST A LITTLE EARLIER THAN USUAL...BY 1300 PDT TO GET THESE CHANGES OUT TO THE DISPATCH CENTERS. THIS DRYING TREND IS RELATIVELY SHORT LIVED...BASICALLY TODAY THROUGH SATURDAY...AFTER WHICH A SIGNIFICANT MOISTENING TREND OCCURS DUE TO THE STRONG SURGE OF MONSOON MOISTURE MENTIONED IN PARAGRAPH TWO ABOVE. MOST IF NOT ALL OF THESE THUNDERSTORMS EXPECTED TO BE ACCOMPANIED BY WETTING RAINS. && .AVIATION... 181430Z...MDCRS SOUNDINGS THIS MORNING PLACE THE MARINE LAYER DEPTH AROUND 1800 FEET...SLIGHTLY LOWER THAN ON THURSDAY. EXPECT LITTLE CHANGE IN THE MARINE LAYER DEPTH THROUGH THE WEEKEND. A WEAK COASTAL EDDY SHOULD HELP MAINTAIN THE MARINE LAYER THROUGH THE WEEKEND. STRATUS WITH BASES AROUND 1000 FEET MSL SHOULD PULL BACK TO THE COAST BETWEEN 15Z AND 17Z. LIMITED BREAKUP OF THE STRATUS ALONG THE IMMEDIATE COAST IS EXPECTED TODAY. STRATUS SHOULD SPREAD BACK INLAND OVER THE COASTAL VALLEY AND MESAS BETWEEN SUNSET AND 06Z AND THE WESTERN INLAND VALLEY AREAS BETWEEN MIDNIGHT AND 10Z. STRATUS IS NOT EXPECTED TO REACH KONT TONIGHT BUT COULD GET TO KCNO. ABOVE THE MARINE LAYER...EXCEPT FOR SOME AFTERNOON CU/TCU OVER THE MOUNTAINS DURING THE AFTERNOONS...A MOSTLY CLEAR SKY WITH UNRESTRICTED VISIBILITIES WILL CONTINUE THROUGH SATURDAY. MID AND HIGH LEVEL MOISTURE MOVING IN FROM THE SOUTHEAST ON SUNDAY COULD BRING TSTMS TO THE MOUNTAINS AND DESERTS ON SUNDAY. MAX TEMPS FOR KPSP AND KTRM FOR TODAY AND SAT...42 TO 44C. HORTON && .MARINE... A MODERATE SOUTH SWELL WILL BEGIN TO MOVE INTO THE COASTAL AREAS TODAY...INCREASING THROUGH SUNDAY. THE PERIOD WILL INCREASE TO 19 SECONDS ON SATURDAY WITH THE PEAK OF THE SWELL EXPECTED ON SUNDAY WITH A PERIOD DROPPING TO 16 SECONDS BY SUNDAY AFTERNOON. SURF IS FORECAST TO BE UP TO 3 TO 6 FEET ON SATURDAY WITH SETS TO 7 FEET OR HIGHER MAINLY IN ORANGE COUNTY SUNDAY. THERE WILL BE STRONG AND DANGEROUS RIP CURRENTS DURING THE WEEKEND. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC/FIRE WEATHER...BALFOUR AVIATION/MARINE...HORTON NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
525 AM PDT FRI JUL 18 2008 .SHORT TERM...(TODAY-SUNDAY) A MODERATELY STRONG INVERSION NEAR 1000 FT DEEP SHOULD ALLOW FOR SOME LOW CLOUDS TO PUSH ACROSS PORTIONS OF THE LA COUNTY VALLEYS THIS MORNING. EDDY SPUN UP EARLY LAST EVENING HELPING TO PUSH LOW CLOUDS IN FROM THE SOUTH TO NORTH. LATEST FOG PRODUCT IMAGERY INDICATED STRATUS ACROSS THE ENTIRE LA COASTAL PLAIN AND ACROSS THE SAN GABRIEL VALLEY AND EASTERN SAN FERNANDO VALLEY. STRATUS SHOULD CONTINUE TO PUSH NORTHWARD ACROSS THE VENTURA COASTAL PLAIN AS WELL. AREAS N OF POINT CONCEPTION CONTINUE TO EXPERIENCE CATEGORICAL LOW CLOUDS AND FOG ACROSS THE CENTRAL COAST THIS MORNING. EXPECT LOW CLOUDS TO BURN OFF MID TO LATE MORNING HOURS ACROSS THE COAST AND A FEW HOURS EARLIER IN VALLEYS. NOT MUCH CHANGE ACROSS THE FORECAST AREA COMPARED TO YESTERDAY AS THICKNESS AND ONSHORE GRADS ARE SIMILAR TO YESTERDAY. THE ONE CHANGE WILL BE LACK OF MONSOONAL MID LEVEL MOISTURE OVER THE REGION. THE MAJORITY OF CONVECTION WILL REMAIN TO THE EAST OF THE AREA AS THE UPPER HIGH OVER THE 4 CORNERS REGION IS BEING PUSHED FARTHER EAST BY ANOTHER HIGH PRESSURE SYSTEM DEVELOPING ALONG THE EASTERN PACIFIC. THIS SHOULD KEEP ANY CONVECTION WELL EAST OF THE REGION INTO NEVADA/AZ. THERE HAS BEEN SOME LOCALIZED NW TO N WINDS ACROSS THE SBA/VTU AND LA COUNTY MOUNTAINS THIS MORNING...BUT WELL BELOW WIND ADVISORY THRESHOLDS. WINDS SHOULD DIMINISH LATER THIS MORNING. THERE COULD BE A WEAK SUNDOWNER ONCE AGAIN THIS AFTERNOON AFFECTING PORTIONS OF THE SANTA BARBARA S. COAST AND ADJACENT FOOTHILLS THIS AFTERNOON THROUGH THE EVENING HOURS WITH WIND GUSTS TO 35 MPH POSSIBLE NEAR GAVIOTA AND THE FOOTHILLS OF MONTECITO LATE EVENING HOURS. EXPECT THE WARMEST TEMPS ACROSS THE ANTELOPE VALLEY REACHING LOWER TRIPLE DIGITS ONCE AGAIN TODAY. WARMEST VALLEY LOCATIONS SHOULD REMAIN IN THE UPPER 90S OVER THE NEXT FEW DAYS. MARINE LAYER INFLUENCE WILL KEEP THE COASTAL AREAS AND VALLEYS NEAR NORMAL OVER THE NEXT FEW DAYS. EXPECT CONTINUED LOW CLOUDS AND FOG REGIME ACROSS THE COASTAL AREAS WITH SOME PATCHY LOW CLOUDS POSSIBLY CREEPING IN THE COASTAL VALLEYS THROUGH SUNDAY. TEMPS WILL BE A DEGREE OR TWO COOLER ON SUNDAY AS BOUNDARY LAYER TEMPS DROP SLIGHTLY AND MODERATE ONSHORE FLOW CONTINUES THROUGH SUNDAY. BY SUNDAY...THE UPPER HIGH THAT WAS OVER THE EASTERN PAC BEGINS TO GET PUSHED EASTWARD AHEAD OF AN UPPER TROF PUSHING ACROSS NRN CAL. AS THIS OCCURS...HIGH PRESSURE BUILDS BACK OVER THE 4 CORNERS REGION WHICH WILL OPEN THE CHANCE OF MID LEVEL MOISTURE TO ADVECT IN ACROSS THE LOWER COLORADO RIVER VALLEY BRINGING A SLIGHT CHANCE TO THE LA COUNTY MTNS. WENT AHEAD AND ADDED 20 PERCENT POPS TO THE LA/VTU COUNTY MOUNTAIN ZONES. WITH BETTER 700 MB MOISTURE ON MON-WED...MORE CONFIDENCE FOR CONVECTION ACROSS THE MOUNTAINS AND ANTELOPE VALLEY BY EARLY NEXT WEEK. .LONG TERM...(MON-THU) BOTH GFS AND ECMWF ARE IN DECENT AGREEMENT THAT THE UPPER HIGH ACROSS THE 4 CORNERS WILL PERSIST THROUGH MID WEEK. BOTH GFS AND ECMWF ADVERTISE PLENTY OF 700 MB MOISTURE MONDAY AND TUE. THE GFS THEN PUSHES MOST OF THE MOISTURE TO THE EAST...BUT THE ECM CONTINUES TO BRING PLENTY OF 700 MB MOISTURE ACROSS OUR AREA THROUGH THROUGH THU. THEREFORE THERE WILL BE A DECENT CHANCE OF THUNDERSTORMS ONCE AGAIN ACROSS THE LA/VTU/SBA COUNTY MOUNTAINS...ANTELOPE VALLEY AND POSSIBLY THE VALLEYS IF UPPER STEERING WINDS CAN PUSH STORMS INTO VALLEYS. WENT AHEAD AND ONLY PUT SLIGHT CHANCE WORDING THROUGH TUE EVENING SINCE LATER MODEL RUNS COULD BACK-OFF CONVECTION PATTERN LATE IN WEEK. ONLY SLIGHT FLUCTUATIONS IN HIGH TEMPS THROUGH THE PERIOD...BUT MONSOONAL MOISTURE COULD MAKE NIGHT TIME TEMPS UNCOMFORTABLE ACROSS INLAND AREAS INCLUDING THE FOOTHILLS ADJACENT TO THE LA/VTU COUNTY VALLEYS. LOW CLOUDS WOULD LIKELY ONLY AFFECT THE COASTAL AREAS AS MONSOONAL FLOW COULD DISRUPT MARINE LAYER THROUGH THE PERIOD. && .AVIATION...18/1200Z LATEST AMDAR SOUNDINGS INDICATE MARINE INVERISON AROUND 1400 FEET THIS MORNING. SATELLITE/SURFACE OBS INDICATE WIDESPREAD STRATUS/FOG ACROSS KSBP/KSMX/KPRB. SOUTH OF POINT CONCEPTION...STRATUS IS FILLING IN NICELY ACROSS COASTAL AREAS OF LAX/VTU COUNTIES. ANY MARINE LAYER THAT DEVELOPS IS EXPECTED TO BURNOFF BY LATE MORNING. KLAX...HIGH CONFIDENCE IN 12Z TAF PACKAGE. THERE IS A SLIGHT CHANCE THAT THE IFR CIGS/VSBYS COULD BREAKOUT BEFORE 18Z. KBUR...MODERATE CONFIDENCE IN 12Z TAF AS STRATUS IS POISED JUST SOUTH OF THE AIRFIELD. THERE IS A CHANCE THAT IFR/LIFR CONDS COULD AFFECT THE AIRFIELD AROUND SUNRISE. IF ANY STRATUS WOULD GET INTO THE AIRFIELD...IT WOULD BE EXPECTED TO BURN OFF VERY QUICKLY LATER THIS MORNING. LOW CONFIDENCE IN 08Z RETURN OF MARINE LAYER TONIGHT. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXCWFLOX). && $$ PUBLIC...KAPLAN AVIATION...THOMPSON WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION FOR THE FLORIDA KEYS
NWS KEY WEST FL
235 PM EDT SAT JUL 19 2008 .DISCUSSION... .CURRENTLY... KBYX DETECTS NO PRECIPITATION ECHOES IN THE FORECAST AREA. SKIES OVER THE ISLAND CHAIN ARE VARIABLY CLOUDY. WINDS OVER LAND ARE EAST TO SOUTHEAST AT 10 TO 15 MPH. C-MAN WINDS...ON AVERAGE...ARE EAST AT 10 TO 15 KNOTS. TEMPERATURES ARE NEAR 90 DEGREES. ONLY ABOUT SEVEN DEGREES OF COOLING IS EXPECTED TONIGHT DUE TO MODERATE EAST SURFACE WINDS OVER WATER WITH TEMPERATURES IN THE MID TO UPPER 80S. .SHORT TERM (TONIGHT THROUGH TUESDAY)... A STRONG TROPICAL WAVE...WHICH COULD DEVELOP INTO A TROPICAL CYCLONE ANYTIME...WILL MOVE TO THE WEST-NORTHWEST THROUGH THE WESTERN CARIBBEAN SEA THIS WEEKEND. AS A MATTER OF FACT...SFMR DATA FROM AN AIR FORCE RECONNAISSANCE AIRCRAFT INDICATES TROPICAL STORM FORCE WINDS...BUT THE AIRCRAFT DOES NOT SEEM TO BE ABLE TO FIND A CLOSED CIRCULATION AT THIS TIME. AT ANY RATE...ATMOSPHERIC MOISTURE WILL INCREASE TONIGHT AS THE STRONG TROPICAL WAVE PASSES SOUTH OF CENTRAL CUBA. BY SUNRISE SUNDAY...PRECIPITABLE WATER (PWAT) VALUES SHOULD BE JUST ABOVE TWO INCHES. INCREASING ATMOSPHERIC MOISTURE WILL LEAD TO INCREASING RAIN CHANCES TONIGHT. THE GFS NUMERICAL MODEL HAS BACKED OFF ON PREVIOUS DEPICTIONS OF LARGE SCALE LIFT OVER THE FLORIDA KEYS SUNDAY. BE THAT AS IT MAY...ABUNDANT MOISTURE AND ADEQUATE ATMOSPHERIC INSTABILITY IS ENOUGH TO SUPPORT MIDDLE OF THE ROAD CHANCE POPS FOR SUNDAY. PWAT VALUES MAY NOT FALL BELOW TWO INCHES UNTIL LATE SUNDAY NIGHT. BE THAT AS IT MAY...LACK OF LARGE SCALE LIFT SHOULD LIMIT POPS TO LOW CHANCE CATEGORY SUNDAY NIGHT. ATMOSPHERIC MOISTURE SHOULD DECREASE CONSIDERABLY MONDAY. BY SUNSET MONDAY...PWAT VALUES COULD BE JUST UNDER ONE AND ONE HALF OF AN INCH...WHICH IS WELL BELOW NORMAL FOR THIS TIME OF YEAR. THIS VERY DIR AIR MASS SHOULD LINGER OVER THE FLORIDA KEYS MONDAY NIGHT AND TUESDAY. NO MORE THAN SLIGHT CHANCE POPS ARE NEEDED FOR MONDAY THROUGH TUESDAY. .LONG TERM (TUESDAY NIGHT THROUGH SATURDAY)... IN THE LOW TO MID LEVELS OF THE ATMOSPHERE...AN ATLANTIC RIDGE OF HIGH PRESSURE WILL EXTEND ACROSS THE FLORIDA PENINSULA TUESDAY NIGHT THROUGH SATURDAY. IN THE UPPER LEVELS OF THE ATMOSPHERE...AN ANTICYCLONE WILL BE CENTERED IN THE VICINITY OF THE NORTHWEST GULF OF MEXICO TUESDAY NIGHT THROUGH SATURDAY. NO CHANGES ANTICIPATED TO THE LONG TERM PORTION OF THE ZONE FORECASTS FOR THE FLORIDA KEYS. && .MARINE... SMALL CRAFT ARE URGED TO EXERCISE CAUTION ON ATLANTIC WATERS TONIGHT THROUGH AT LEAST MONDAY NIGHT DUE TO SUSTAINED EAST TO SOUTHEAST SURFACE WINDS OF 15 TO 20 KNOTS. EAST TO SOUTHEAST SURFACE WINDS OF 15 TO 20 KNOTS ARE POSSIBLE ON ATLANTIC WATERS TUESDAY. FOR NOW... WIND SPEEDS WILL BE ADVERTISED JUST BELOW 15 TO 20 KNOTS ON ATLANTIC WATERS FOR TUESDAY. NO ADVISORIES OR CAUTIONARY STATEMENTS EXPECTED TUESDAY NIGHT THROUGH THURSDAY. && .AVIATION... TONIGHT...DRY WEATHER WILL CONTINUE FOR MUCH OF THE NIGHT. THE KEYS WILL REMAIN BENEATH AN AREA OF HIGH PRESSURE WEDGED BETWEEN TROPICAL STORM CRISTOBAL OFF THE SOUTHEAST COAST AND A STRONG TROPICAL WAVE NOW ENTERING THE WESTERN CARIBBEAN. AS A RESULT...THE PRESSURE GRADIENT WILL ALLOW FOR EAST TO SOUTHEAST SURFACE WINDS TO INCREASE FROM 10 TO 15 KNOTS TO AROUND 15 KNOTS TOWARDS MORNING. ISOLATED SHOWERS AND THUNDERSTORMS WILL IMPACT THE KEYW AND KMTH ISLAND TERMINALS...MAINLY AFTER 10Z TO 12Z. && .CLIMATE... ON THIS DATE IN KEYS WEATHER HISTORY...IN 1967...THE LOW TEMPERATURE IN KEY WEST WAS ONLY 85 DEGREES. THIS SET THE DAILY RECORD FOR WARMEST LOW TEMPERATURE MEASURED IN KEY WEST ON JULY 19TH...A RECORD WHICH STILL STANDS 41 YEARS LATER. IN ADDITION...THIS LOW TEMPERATURE OF 85 DEGREES IS TIED AS THE WARMEST LOW TEMPERATURE EVER RECORDED IN KEY WEST DURING THE MONTH OF JULY. && .PRELIMINARY POINT TEMPS/POPS... KEY WEST 82 89 82 90 / 30 40 30 20 MARATHON 82 91 82 92 / 30 40 30 20 && .KEY WATCHES/WARNINGS/ADVISORIES... FL...NONE. GM...NONE. && $$ PUBLIC/MARINE/FIRE/CLIMATE/DIGITAL...BS AVIATION/NOWCASTS....................FUTTERMAN DATA ACQUISITION.....................DR VISIT US ON THE WEB AT WWW.WEATHER.GOV/KEYWEST
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
314 AM CDT FRI JUL 18 2008 .DISCUSSION... 324 PM CDT SHORT TERM FORECAST PROBLEM IS ONCE AGAIN POTENTIAL OF TS CURRENTLY MOVING ACROSS SE WI AND NORTHERN IA TO MAKE IT S AND ACROSS THE WI BORDER THIS EVE. PAIR OF SHORT WAVES MOVING THRU ZONAL FLOW WITH FIRST PUSHING ACROSS NW WI WHILE SECOND IS CROSSING SOUTHERN WI AND NORTHERN IA. MORE SOUTHERN WAVE TO CONTINUE EASTWARD ACROSS SOUTHERN WI TONIGHT AND EXPECTED TO MAINTAIN TS. WHILE FORECAST SOUNDINGS INDICATED THAT CAP TO BE ALL BUT GONE BY 18Z TODAY...ORD ACARS DATA SHOWING IT PERSISTS AT MID AFTERNOON. WHILE OUTFLOW FROM SW WI CONVECTION MAY PUSH INTO THE FAR NW PORTION OF THE FA THIS EVE...FEEL THAT THE PERSISTENT CAP WILL INHIBIT ANY TS FROM BEING INITIATED MUCH FURTHER S THAN THE WI LINE. MULTIPLE MID LEVEL CIRCULATIONS UPSTREAM WITH NEXT MOVING FROM SE SASKATCHEWAN INTO SOUTHERN MANITOBA. THIS FEATURE TO CROSS ONTARIO W TO E DURING THE DAY FRI. WITH ITS PASSAGE THE SURFACE BOUNDARY ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST TO MOVE SOMEWHAT SOUTHWARD TO SOUTHERN WI AND ALONG THE MN-IA BORDER BY 00Z SAT. WITH BOUNDARY CLOSER TO THE FA AND ANOTHER SHORT WAVE TROF PROGGED TO BE MOVING E FROM THE CENTRAL PLAINS FRI NIGHT HAVE POPS GRADUALLY INCREASING ACROSS THE WESTERN AND NORTHERN PORTIONS OF THE FA. WEAKENING FRONT STILL TO BE NEAR THE WI-IL BORDER ON SAT BUT A STRENGTHENING FRONT FORECAST TO EXTEND ACROSS THE MID MS VALLEY INTO CENTRAL AND SOUTHERN PORTION OF NORTHERN IL BY AFTERNOON WITH 25-35 KT SW H8 WINDS PRODUCING DECENT LOW LEVEL CONVERGENCE THUS LIKELY POPS ACROSS NORTHERN AND CENTRAL FA WITH CHC POPS ACROSS THE S. SURFACE BOUNDARY TO REMAIN ACROSS THE FA THRU SAT NIGHT INTO SUN SO HAVE CONTINUED CHC POPS AS ANOTHER SHORT WAVE TROF DROPS SE ACROSS THE UPPER MIDWEST. QUESTION ON HOW LONG IT WILL TAKE FOR THE FRONT TO CLEAR THE FA AND BE LOCATED FAR ENOUGH S OF THE AREA TO ALLOW DRY AIR TO OVERSPREAD THE FA. FRONT LOOKS TO BE INTO CENTRAL IL BY SUN NIGHT BUT DEW POINTS BLO 60F DO NOT ARRIVE UNTIL DURING THE DAY MON. WITH CYCLONIC FLOW ALOFT AND COOLING OF MID LEVELS APPEARS TO BE A CONTINUED CHC OF SHRA/TSRA WITH DAYTIME HEATING. VERY WARM TO MARGINALLY HOT TEMPS AND ELEVATED HUMIDITIES TO PERSIST TIL FROPA...THO INCREASED CLOUDINESS AND COOLING FROM TS OUTFLOWS EXPECTED TO CUT INTO THE TEMPERATURES ACROSS THE NW PORTION OF THE FA TOMORROW...AND THE NW THRU N PORTIONS SAT. TRS && .AVIATION... 1255 AM CDT 0600 UTC TAFS...CHANCES OF SHOWERS/THUNDERSTORMS WILL BE THE MAIN FORECAST ISSUE FOR TODAY/TONIGHT. SUBJECTIVE SURFACE ANALYSIS FROM 05Z STILL SUGGESTING MAIN SURFACE BOUNDARY EXTENDING FROM SOUTHWEST MINNESOTA INTO WEST CENTRAL WISCONSIN WITH ANOTHER SURFACE TROUGH ACROSS SOUTHERN WISCONSIN INTO NORTHWEST ILLINOIS. CONVECTIVE SYSTEM ACROSS EASTERN IOWA HAS BEEN SHOWING A STEADY DECREASING INTENSITY TREND OVER THE PAST FEW HOURS AS IT ENCOUNTERS A PROGRESSIVELY LESS UNSTABLE ENVIRONMENT SOUTH OF THESE BOUNDARIES. DO HAVE SOME CONCERN OVERNIGHT FOR THE POSSIBILITY THAT SOME OF THESE SHOWERS MAY AFFECT NORTHWEST ILLINOIS AND POSSIBLY INTO THE ROCKFORD AREA AFTER 08Z AS MOISTER LOW LEVEL AIR IS ADVECTED EASTWARD ACROSS FAR NORTHERN ILLINOIS. DID INCLUDE MENTION OF SOME RAIN SHOWERS AT RFD IN THE 08Z-11Z TIME PERIOD. SOME MVFR VSBYS WITH HZ POSSIBLE AFTER 08Z OR 09Z...ESPECIALLY AT RFD/DPA. QUESTION FOR THIS AFTERNOON WILL BE ON THE POTENTIAL ON SHOWER/THUNDERSTORM REDEVELOPMENT. IT DOES APPEAR AS THOUGH A CONVECTIVELY ENHANCED VORT MAX FROM EASTERN IOWA CONVECTION WILL MOVE ACROSS NORTHERN ILLINOIS LATE THIS MORNING/EARLY THIS AFTERNOON WITH INSTABILITY PROGS A BIT MORE IMPRESSIVE TODAY GIVEN INCREASING LOW LEVEL MOISTURE AND SLIGHT SOUTHWARD SHIFT OF MID LEVEL THERMAL RIDGE INTO CENTRAL ILLINOIS. ALTHOUGH PRIMARY SFC BOUNDARY WILL REMAIN NORTH OF THE AREA TODAY...EXPECTING DIURNALLY ENHANCED INSTABILITY TO PROVIDE CHANCE OF ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON...ESPECIALLY ACROSS FAR NORTHERN ILLINOIS. GIVEN SOME QUESTIONS AS TO MAGNITUDE OF INSTABILITY ACROSS NORTHEAST ILLINOIS TERMINALS...WILL KEEP MENTION TO VCTS AND PROB30 FOR SHRA FOR ORD/MDW/DPA. SOUTHWEST WINDS AROUND 10 KNOTS OVERNIGHT WILL VEER SLIGHTLY TO THE WEST SOUTHWEST THIS AFTERNOON IN ADVANCE OF THE SURFACE FRONT WITH SOME GUSTS UP TO AROUND 15 KNOTS THIS AFTERNOON. WITH LOSS OF MIXING THIS EVENING...EXPECTING TO WINDS TO FLOP BACK MORE TO SOUTHWESTERLY DIRECTION THIS WITH SPEEDS LESS THAN 10 KNOTS FOR FRIDAY EVENING. MARSILI && .MARINE... 312 AM CDT SOUTH TO SOUTHWEST WINDS WILL CONTINUE ACROSS LAKE MICHIGAN TODAY. A WEAK AREA OF LOW PRESSURE ACROSS WESTERN LAKE SUPERIOR WILL MOVE ACROSS THE NORTHERN GREAT LAKES TODAY...AND INTO SOUTHERN QUEBEC BY THIS EVENING. A FRONTAL BOUNDARY EXTENDING WESTWARD FROM THIS LOW PRESSURE WILL SLOWLY SAG SOUTHWARD TONIGHT...SETTING UP NORTHEAST WINDS ACROSS THE NORTHERN HALF OF LAKE MICHIGAN FOR LATE TONIGHT. THIS FRONT WILL THEN STALL OUT OVER THE SOUTHERN HALF OF LAKE MICHIGAN ON SATURDAY. ANOTHER LOW PRESSURE AREA WILL DEVELOP ALONG THIS FRONT SATURDAY NIGHT AND TRACK ACROSS SOUTHERN LAKE MICHIGAN...ALLOWING THE FRONT TO DROP SOUTH OF THE LAKE ON SUNDAY. AS A RESULT...NORTHWEST WINDS ARE EXPECTED ACROSS LAKE MICHIGAN ON SUNDAY ALTHOUGH SPEEDS ARE EXPECTED TO REMAIN 10 KNOTS OR LESS. MAIN QUESTIONS IN THIS FORECAST CENTER ON WIND DIRECTIONS FOR THE EARLY PART OF NEXT WEEK WITH SOME CONFLICTING SIGNALS SHOWING UP IN NUMERICAL GUIDANCE WITH REGARDS TO STRENGTH/PLACEMENT OF SURFACE HIGH MOVING INTO THE WESTERN GREAT LAKES. FOR NOW HAVE CONTINUED IDEA OF MAINTAINING WEST/NORTHWEST WINDS MON/TUE AS RIDGE AXIS SLOWLY BUILDS INTO THE WESTERN GREAT LAKES. THE WEAK SURFACE GRADIENT ACROSS THE AREA SHOULD CONTINUE TO PROMOTE WAVE HEIGHTS ON THE LOW SIDE...GENERALLY 2 FEET OR LESS FROM TONIGHT THROUGH THE EARLY PART OF NEXT WEEK. MARSILI && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
100 AM CDT FRI JUL 18 2008 .DISCUSSION... 324 PM CDT SHORT TERM FORECAST PROBLEM IS ONCE AGAIN POTENTIAL OF TS CURRENTLY MOVING ACROSS SE WI AND NORTHERN IA TO MAKE IT S AND ACROSS THE WI BORDER THIS EVE. PAIR OF SHORT WAVES MOVING THRU ZONAL FLOW WITH FIRST PUSHING ACROSS NW WI WHILE SECOND IS CROSSING SOUTHERN WI AND NORTHERN IA. MORE SOUTHERN WAVE TO CONTINUE EASTWARD ACROSS SOUTHERN WI TONIGHT AND EXPECTED TO MAINTAIN TS. WHILE FORECAST SOUNDINGS INDICATED THAT CAP TO BE ALL BUT GONE BY 18Z TODAY...ORD ACARS DATA SHOWING IT PERSISTS AT MID AFTERNOON. WHILE OUTFLOW FROM SW WI CONVECTION MAY PUSH INTO THE FAR NW PORTION OF THE FA THIS EVE...FEEL THAT THE PERSISTENT CAP WILL INHIBIT ANY TS FROM BEING INITIATED MUCH FURTHER S THAN THE WI LINE. MULTIPLE MID LEVEL CIRCULATIONS UPSTREAM WITH NEXT MOVING FROM SE SASKATCHEWAN INTO SOUTHERN MANITOBA. THIS FEATURE TO CROSS ONTARIO W TO E DURING THE DAY FRI. WITH ITS PASSAGE THE SURFACE BOUNDARY ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST TO MOVE SOMEWHAT SOUTHWARD TO SOUTHERN WI AND ALONG THE MN-IA BORDER BY 00Z SAT. WITH BOUNDARY CLOSER TO THE FA AND ANOTHER SHORT WAVE TROF PROGGED TO BE MOVING E FROM THE CENTRAL PLAINS FRI NIGHT HAVE POPS GRADUALLY INCREASING ACROSS THE WESTERN AND NORTHERN PORTIONS OF THE FA. WEAKENING FRONT STILL TO BE NEAR THE WI-IL BORDER ON SAT BUT A STRENGTHENING FRONT FORECAST TO EXTEND ACROSS THE MID MS VALLEY INTO CENTRAL AND SOUTHERN PORTION OF NORTHERN IL BY AFTERNOON WITH 25-35 KT SW H8 WINDS PRODUCING DECENT LOW LEVEL CONVERGENCE THUS LIKELY POPS ACROSS NORTHERN AND CENTRAL FA WITH CHC POPS ACROSS THE S. SURFACE BOUNDARY TO REMAIN ACROSS THE FA THRU SAT NIGHT INTO SUN SO HAVE CONTINUED CHC POPS AS ANOTHER SHORT WAVE TROF DROPS SE ACROSS THE UPPER MIDWEST. QUESTION ON HOW LONG IT WILL TAKE FOR THE FRONT TO CLEAR THE FA AND BE LOCATED FAR ENOUGH S OF THE AREA TO ALLOW DRY AIR TO OVERSPREAD THE FA. FRONT LOOKS TO BE INTO CENTRAL IL BY SUN NIGHT BUT DEW POINTS BLO 60F DO NOT ARRIVE UNTIL DURING THE DAY MON. WITH CYCLONIC FLOW ALOFT AND COOLING OF MID LEVELS APPEARS TO BE A CONTINUED CHC OF SHRA/TSRA WITH DAYTIME HEATING. VERY WARM TO MARGINALLY HOT TEMPS AND ELEVATED HUMIDITIES TO PERSIST TIL FROPA...THO INCREASED CLOUDINESS AND COOLING FROM TS OUTFLOWS EXPECTED TO CUT INTO THE TEMPERATURES ACROSS THE NW PORTION OF THE FA TOMORROW...AND THE NW THRU N PORTIONS SAT. TRS && .AVIATION... 1255 AM CDT 0600 UTC TAFS...CHANCES OF SHOWERS/THUNDERSTORMS WILL BE THE MAIN FORECAST ISSUE FOR TODAY/TONIGHT. SUBJECTIVE SURFACE ANALYSIS FROM 05Z STILL SUGGESTING MAIN SURFACE BOUNDARY EXTENDING FROM SOUTHWEST MINNESOTA INTO WEST CENTRAL WISCONSIN WITH ANOTHER SURFACE TROUGH ACROSS SOUTHERN WISCONSIN INTO NORTHWEST ILLINOIS. CONVECTIVE SYSTEM ACROSS EASTERN IOWA HAS BEEN SHOWING A STEADY DECREASING INTENSITY TREND OVER THE PAST FEW HOURS AS IT ENCOUNTERS A PROGRESSIVELY LESS UNSTABLE ENVIRONMENT SOUTH OF THESE BOUNDARIES. DO HAVE SOME CONCERN OVERNIGHT FOR THE POSSIBILITY THAT SOME OF THESE SHOWERS MAY AFFECT NORTHWEST ILLINOIS AND POSSIBLY INTO THE ROCKFORD AREA AFTER 08Z AS MOISTER LOW LEVEL AIR IS ADVECTED EASTWARD ACROSS FAR NORTHERN ILLINOIS. DID INCLUDE MENTION OF SOME RAIN SHOWERS AT RFD IN THE 08Z-11Z TIME PERIOD. SOME MVFR VSBYS WITH HZ POSSIBLE AFTER 08Z OR 09Z...ESPECIALLY AT RFD/DPA. QUESTION FOR THIS AFTERNOON WILL BE ON THE POTENTIAL ON SHOWER/THUNDERSTORM REDEVELOPMENT. IT DOES APPEAR AS THOUGH A CONVECTIVELY ENHANCED VORT MAX FROM EASTERN IOWA CONVECTION WILL MOVE ACROSS NORTHERN ILLINOIS LATE THIS MORNING/EARLY THIS AFTERNOON WITH INSTABILITY PROGS A BIT MORE IMPRESSIVE TODAY GIVEN INCREASING LOW LEVEL MOISTURE AND SLIGHT SOUTHWARD SHIFT OF MID LEVEL THERMAL RIDGE INTO CENTRAL ILLINOIS. ALTHOUGH PRIMARY SFC BOUNDARY WILL REMAIN NORTH OF THE AREA TODAY...EXPECTING DIURNALLY ENHANCED INSTABILITY TO PROVIDE CHANCE OF ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS THIS AFTERNOON...ESPECIALLY ACROSS FAR NORTHERN ILLINOIS. GIVEN SOME QUESTIONS AS TO MAGNITUDE OF INSTABILITY ACROSS NORTHEAST ILLINOIS TERMINALS...WILL KEEP MENTION TO VCTS AND PROB30 FOR SHRA FOR ORD/MDW/DPA. SOUTHWEST WINDS AROUND 10 KNOTS OVERNIGHT WILL VEER SLIGHTLY TO THE WEST SOUTHWEST THIS AFTERNOON IN ADVANCE OF THE SURFACE FRONT WITH SOME GUSTS UP TO AROUND 15 KNOTS THIS AFTERNOON. WITH LOSS OF MIXING THIS EVENING...EXPECTING TO WINDS TO FLOP BACK MORE TO SOUTHWESTERLY DIRECTION THIS WITH SPEEDS LESS THAN 10 KNOTS FOR FRIDAY EVENING. MARSILI && .MARINE... 1258 PM CDT A WEAK FRONTAL BOUNDARY EXTENDS FROM THE NORTHERN PLAINS...ACROSS THE CENTRAL PORTION OF LAKE MICHIGAN...TO LAKE HURON. THIS FRONT WILL LIFT NORTH INTO NORTHERN LAKE MICHIGAN THIS AFTERNOON...THEN SAG SOUTH AGAIN LATE FRIDAY AFTER THIS LOW PASSAGE. STORMS WILL LIKELY ACCOMPANY THESE WAVES ALONG THIS FRONTAL BOUNDARY. ANOTHER WAVE MOVING ACRS WI AND NRN LK MICHIGAN SAT NIGHT INTO SUNDAY WILL DROP THIS BOUNDARY SOUTH THRU LK MICHIGAN SUN NGT INTO MONDAY... REVERTING WINDS FROM A SOUTH FLOW TO A NORTHERLY FLOW TUESDAY. RIDGING OVER THE LAKE WED AND THUR WILL ACCOUNT FOR QUITE VARIABLE FLOW OVER THE LAKE AND THUS LITTLE WAVE ACTION. RLB && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS LAKE CHARLES LA
345 PM CDT SAT JUL 19 2008 .SHORT TERM... ANOTHER SUMMER DAY...ANOTHER ROUND OF SCATTERED SHOWERS AND THUNDERSTORMS. RADAR IMAGERY SHOWING WIDELY SCATTERED CONVECTION STRETCHING IN AN ARC FROM INTERIOR SOUTHEAST TEXAS DOWN INTO THE SOUTHEASTERN PORTION OF THE CWA. AREA SURFACE OBSERVATIONS ALSO INDICATING ANOTHER HOT DAY WITH TEMPS HAVING REACHED THE MID TO UPPER 90S OUTSIDE OF AREAS WITH RAIN-COOLED AIR. MAIN FORECAST STORY OVER THE WEEKEND WILL BE THE HEAT. GFS AND ECMWF BOTH INDICATE HEIGHTS WILL RAPIDLY BUILD OVER THE AREA TONIGHT INTO TOMORROW AS MID LEVEL RIDGE CONSOLIDATES OVER THE SOUTHERN CONUS THROUGH EARLY NEXT WEEK. THIS WILL HELP TO SUPPRESS CONVECTION ACROSS THE AREA BOTH SUNDAY AND MONDAY WITH THUNDERSTORM COVERAGE EXPECTED TO BE MUCH LESS THAN TODAY. IN ADDITION...TEMPS ARE EXPECTED TO BE WARMER...WITH ALL LOCATIONS SEEING HIGHS IN THE MID TO UPPER 90S. A FEW LOCATIONS IN INTERIOR SOUTHEAST TEXAS AND CENTRAL LOUISIANA MAY EVEN REACH THE 100 DEGREE MARK. && .LONG TERM... IN ADDITION TO THE HEAT...ALL EYES WILL BE ON A STRONG TROPICAL WAVE CURRENTLY PASSING JAMAICA IN THE CARIBBEAN SEA...WHICH WILL BE ENTERING THE SOUTHWESTERN GULF OF MEXICO ON MONDAY. RECONNAISSANCE AIRCRAFT HAVE FOUND WINDS TO TROPICAL STORM FORCE IN THE WAVE THIS AFTERNOON...BUT NO WELL DEFINED LOW LEVEL CIRCULATION. BOTH THE GFS AND ECMWF INDICATE POTENTIAL TROPICAL CYCLONE DEVELOPMENT OF THIS SYSTEM AS IT HEADS ACROSS THE NORTHWESTERN CARIBBEAN INTO THE GULF OF MEXICO...WITH MODELS TAKING IT WELL TO THE WEST OF OUR CWA AND GENERALLY IN THE DIRECTION OF NORTHERN MEXICO OR FAR SOUTHERN TEXAS. REGARDLESS OF WHETHER THE TROPICAL WAVE DEVELOPS OR NOT...MODELS HAVE BEEN VERY CONSISTENT ON A LARGE SLUG OF TROPICAL MOISTURE SPREADING INTO THE CWA BEGINNING ON TUESDAY. WITH PWATS PROGGED TO RISE OVER 2 INCHES...SHOWERS AND THUNDERSTORMS WILL BECOME INCREASINGLY LIKELY BY MIDWEEK. HAVE MAINTAINED THE HIGH CHANCE POPS OVER THE CWA...BUT THESE MAY NEED TO BE RAISED INTO THE LIKELY CATEGORY CLOSER TO MEX GUIDANCE. THE INCREASE IN CLOUD COVER AND MOISTURE WILL ALSO RESULT IN LOWER TEMPS AREAWIDE...WITH TEMPS CLOSER TO CLIMATOLOGICAL NORMS. TOWARDS THE END OF THE PERIOD...MODELS HAVE NOT SHOWN MUCH CONSISTENCY LATER NEXT WEEK...WITH NOW INDICATIONS OF A STRONG RIDGE REBUILDING OVER THE SOUTHERN CONUS. FOR NOW HAVE KEPT TEMPS AND PRECIP NEAR OR SLIGHTLY ABOVE CLIMO FOR THE END OF THE WEEK. && .AVIATION... VCTS AT ALL TERMINALS THROUGH 00Z WITH TSRA MOST LIKELY TO AFFECT KARA AND KLFT. VFR CEILINGS WITH HIGH-BASED CUMULUS AROUND 5K FEET BUT ALL CLOUDS AND PRECIP SHOULD DIMINISH RAPIDLY AFTER 00Z. BRIEF MVFR VISIBILITIES POSSIBLE ONCE AGAIN AT ALL TAF SITES FROM 9-13Z IN THE MORNING. && .MARINE... LIGHT WINDS AND SEAS WITH ISOLATED SHOWERS AND STORMS WILL CONTINUE THROUGH MONDAY. BY MIDWEEK...THE TROPICAL WAVE MOVING ACROSS THE WESTERN GULF MAY RESULT IN AN INCREASE IN WINDS AND SEAS ESPECIALLY OVER THE OUTER COASTAL WATERS. A SCA MAY BE POSSIBLE DEPENDING ON THE EXACT TRACK AND ANY DEVELOPMENT OF THE TROPICAL WAVE. && .PRELIMINARY POINT TEMPS/POPS... KLCH 74 95 75 95 75 / 10 20 10 20 20 KBPT 74 95 75 95 75 / 10 20 10 20 20 KAEX 73 99 74 99 75 / 10 20 10 20 10 KLFT 74 96 76 96 76 / 10 20 10 20 10 && .LCH WATCHES/WARNINGS/ADVISORIES... LA...NONE. TX...NONE. GM...NONE. && $$ SHAMBURGER
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
306 PM EDT SAT JUL 19 2008 .SYNOPSIS... HIGH PRESSURE WILL INFLUENCE THE REGIONS WEATHER INTO MONDAY...AS TROPICAL STORM CRISTOBAL MOVES NORTHEAST FROM THE SOUTH CAROLINA COAST INTO THE WESTERN ATLANTIC. A COLD FRONT WILL KICK OFF A ROUND OF SHOWERS AND THUNDERSTORMS TUESDAY. HIGH PRESSURE WILL BUILD BACK FOR THE SECOND HALF OF THE WEEK. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/... WATER VAPOR LOOP SHOWS A RIDGE FROM THE SOUTHWEST CONUS EAST INTO THE MID ATLANTIC. A SYSTEM WAS OFF THE GEORGIA COAST...WITH THE MEAN FLOW RESIDING ALONG THE CANADIAN BORDER. ACARS 400-250MB WIND OBSERVATIONS SHOW A 80-110KT JET FROM THE PACIFIC NORTHWEST EAST NORTHEAST OVER THE UPPER GREAT LAKES AND NEW ENGLAND. LIGHT WINDS RESIDED OVER THE SOUTHEAST CONUS. 11Z SURFACE ANALYSIS PLACED A 1010MB CYCLONE OFF THE GEORGIA COAST. 1019MB ANTICYCLONE DOMINATED THE CENTRAL APPALACHIANS...WELL AHEAD OF THE COLD FRONT STALLED ACROSS THE UPPER MIDWEST AND GREAT LAKES REGION. A TROUGH WAS NOTED IN THE LEE OF THE CENTRAL APPALACHIANS. COMBINATION OF WARM SUMMER TEMPERATURES AND RETURN OF MOISTURE FROM THE SOUTHEAST SHOULD YIELD HEAT INDEX VALUES NEAR 100F THIS AFTERNOON ALONG AND EAST OF INTERSTATE 95. IT WILL BE MOST NOTABLE IN URBAN AREAS AND ALONG THE BAY. COMBINATION OF SUBSIDENCE AND DRY ATMOSPHERE SHOULD KEEP ANYTHING OTHER THAN A STRAY LIGHT SHOWER FROM MAKING IT INTO THE SOUTHERN ZONES THIS EVENING. GIVEN DEVELOPING SUBSIDENCE INVERSION...CUMULUS FIELD FROM THE SOUTH MAY TAKE A BIT OF TIME TO DISSIPATE TONIGHT. DEWPOINT VALUES HAVE INCREASED...PARTICULARLY ACROSS THE EASTERN ZONES...BUT THINK DEWPOINT DEPRESSION VALUES WILL NOT NEAR ZERO FOR A SIGNIFICANT PERIOD OF TIME TONIGHT AS TEMPERATURES REMAIN RATHER WARM. EXPECT PATCHY FOG WHICH MAY BE A BIT MORE PRONOUNCED THAN LAST NIGHT... HOWEVER PROBABLY NOT EVEN A WORTH A MENTION IN GRIDS/TEXT PRODUCTS. && .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY NIGHT/... WITH TROPICAL STORM CRISTOBAL FORECAST TO MOVE NORTHEAST AWAY FROM THE CAROLINA COAST TOMORROW...FORECAST AREA REMAINS IN THE SUBSISTENT ZONE BETWEEN THE STORM AND WESTERLIES TO THE NORTH. AS LOW LEVEL CONVERGENCE INCREASES IN THE PRESENCE OF RICH LOW LEVEL MOISTURE...ISOLATED SHOWERS ANTICIPATED ACROSS LOWER SOUTHERN MARYLAND. ELSEWHERE...WHILE CANT RULE OUT A STRAY SHOWER...DO NOT HAVE ENOUGH CONFIDENCE TO PLACE MENTIONABLE POPS. WITH SIMILAR TEMPERATURES AND DEW POINTS IN THE FORECAST FOR TOMORROW...HEAT INDEX ONCE AGAIN EXPECTED TO NEAR 100 DEGREES ALONG AND EAST OF INTERSTATE 95...PARTICULARLY IN URBAN LOCATIONS SUCH AS BALTIMORE AND WASHINGTON DC...AND ALONG PORTIONS OF THE WESTERN SHORE OF THE CHESAPEAKE BAY. NEWLY NAMED CRISTOBAL WL BE THE KEY TO THE FCST SUN NGT-MON AS WELL. OFFICIAL FCSTS TAKE THE CYCLONE TO THE NE...NOT AFFECTING CWFA. INSTEAD...THE REGION WL REMAIN IN THE RING OF SUBSIDENCE...W/ RATHER LOW MEAN LYR RH VALUES DVLPG. CDFNT STILL SINKING SEWD FM GRTLKS/NEW ENGLND...BUT A TRAFFIC JAM DVLPS...SHEARING FNT APART. HV THUS RMVD POPS FM FCST MON. THERE ARE A CPL PLACES WHERE PCPN MAY DVLP THO-- SUN NGT IN CNVGNC ZN NEAR BAY...AND PERHAPS ALNG APPCHN RDGLN... AND AGN LT MON DUE TO TRRN CIRCULATIONS INVOF FNT. CONFIDENCE/CVRG CONCERNS PRECLUDE POP MNTN. BY TUE...THE SFC BNDRY WL STILL BE NEARBY...THE TRPCL LOW SHUD EJECT WELL NE...AND ATMOS VRBLS WL BE MORE FVRBL FOR THE DVLPMNT OF TSRA. SO...WL PIN POPS TO THE DIURNAL CYCLE THAT DAY. DAYTIME TEMPS SHUD GRDLY RECEDE AS HGTS DROP AND CLDS BUILD. NAM SOLN MATCHES TRACK FCST MORE CLOSELY...SO HV LEANED ON MET MIN-T FCST FAIRLY HVLY. TEMPS SHUD BE ABLE TO HOLD UP IN A TRPCL ENVIRONMENT. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... CDFNT SHUD BE STALLED JUST S OF CWFA THRU XTNDD FCST PDS...W/ VARIOUS WV/S RIDING ALNG BNDRY. TIMING EACH OF THESE IMPULSES ALWAYS PROBLEMATIC...AS IS DRAWING PRECISELY WHERE CDFNT WL END UP. FOR THE GRIDS...HV NOTED AREAS MOST SUSCEPTIBLE TO TSRA SPATIALLY...AND HV CONFINED POPS TO THE CLIMO FAVORED DIURNAL CYCLE TEMPORALLY. CHC POPS THEN/THERE...DRY ELSW. THAT WL MAKE WED THE BEST DAY...RELATIVELY SPEAKING...BEFORE EVERYTHING SHIFTS NWD AGN. XPCT AMPLE CLDS...INHIBITING MAXT. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... PATCHY MVFR FOG DEVELOPS TONIGHT ACROSS OUTLYING AREAS...UNDER SCATTERED MID DECK. SOUTHERLY FLOW CONTINUES TOMORROW...WITH A FEW SHOWERS DEVELOPING SOUTH OF KDCA AS CONVERGENCE ZONE EXTENDING FROM THE TROPICAL STORM CROSSES THE REGION. VFR CONDS SHUD PREVAIL THRU MON. LCL MVFR-IFR PSBL INVOF TSRA TUE AFTN-EVE...BUT RESTRICTIONS SHUD BE SHORT LIVED. && .MARINE... A SMALL CRAFT ADVISORY FOR THE MID BAY AND LOWER TIDAL POTOMAC RIVER REMAINS IN EFFECT THIS EVENING. EXPECT SOUTHERLY CHANNELING TO DEVELOP LATE THIS AFTERNOON AND EVENING...WITH GUSTS AROUND 20 KNOTS. A SIMILAR SCENARIO IS POSSIBLE TOMORROW EVENING...HOWEVER WILL AWAIT UPDATED GUIDANCE AS IT LOOKS LIKE ANOTHER MARGINAL EVENT. OTRW...NO FLAGS OR HAZARDS XPCTD ON THE WATERS THRU TUE MRNG. SCT TSRA PSBL TUE AFTN-EVE W/ LCLLY HIER WNDS/WVS AND LTNG. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 11 PM EDT THIS EVENING FOR ANZ532>534-537. && $$ SYNOPSIS...HTS NEAR TERM...ROGOWSKI SHORT TERM...ROGOWSKI/HTS LONG TERM...HTS AVIATION...ROGOWSKI/HTS MARINE...ROGOWSKI/HTS
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
1111 AM EDT FRI JUL 18 2008 .SYNOPSIS... HIGH PRESSURE OVER THE MID ATLANTIC WILL DRIFT INTO THE WESTERN ATLANTIC BY SATURDAY. HUMIDITY WILL GRADUALLY INCREASE OVER THE WEEKEND. THE HEAT AND HUMIDITY WILL BRING THE CHANCE FOR SHOWERS AND THUNDERSTORMS SUNDAY THROUGH THE BEGINNING OF NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... ...HOT AND MUGGY TODAY... WATER VAPOR LOOP SHOWS A RIDGE FROM THE SOUTHWEST CONUS EAST INTO THE MID ATLANTIC. A SYSTEM WAS OFF THE GEORGIA COAST...WITH THE MEAN FLOW RESIDING ALONG THE CANADIAN BORDER. ACARS 400-250MB WIND OBSERVATIONS SHOW A 80-120KT JET FROM THE PACIFIC NORTHWEST EAST NORTHEAST OVER THE UPPER GREAT LAKES AND NEW ENGLAND. LIGHT WINDS RESIDED OVER THE SOUTHEAST CONUS. 11Z SURFACE ANALYSIS PLACED A 1012MB CYCLONE OFF THE GEORGIA COAST. 1021MB ANTICYCLONE DOMINATED THE CENTRAL APPALACHIANS...WELL AHEAD OF THE COLD FRONT ACROSS THE UPPER MIDWEST. SUBSIDENCE WITH RIDGING ALOFT WILL YIELD DEEP MIXING WITH TEMPERATURES IN THE MIDDLE 90S. WHILE THE DEEP MIXING SHOULD MIX SOME DRIER AIR TO THE SURFACE...LOCALLY POOLING OF HIGHER DEWPOINTS NEAR THE CITIES AND ALONG THE WATER IS POSSIBLE. HEAT INDEX WILL NEAR 100F IN SOME LOCATIONS. WILL BE SENDING OUT A SPECIAL WEATHER STATEMENT AS MANY FOLKS ARE OUT AND ABOUT. SUBSIDENCE EXPECTED TO KEEP MID LEVEL CAPPING IN PLACE...HOWEVER WEAK FLOW THROUGH THE COLUMN IS A GOOD ENVIRONMENT FOR TERRAIN CIRCULATION. ANTICIPATE A FEW SHOWERS OR THUNDERSTORMS ON THE WESTERN RIDGELINE DEVELOPING MID TO LATE AFTERNOON. WHILE STORM MOTIONS ARE 10 KNOTS OR LESS...LACK OF SHEAR SHOULD MAKE INDIVIDUAL STORM LIFE CYCLES RATHER SHORT...WITH NEW DEVELOPMENT ON GUST FRONTS (LOWERING RISK OF LOCALIZED HEAVY RAINFALL UNLESS A STORM IS ABLE TO REMAIN TERRAIN LOCKED). && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... ANOTHER WARM NIGHT WITH HIGH PRESSURE IN PLACE. WITH INCREASING MOISTURE...PATCH FOG IS EXPECTED ALONG AND WEST OF THE BLUE RIDGE. && .LONG TERM /SATURDAY THROUGH THURSDAY/... SATURDAY...ISOLATED TERRAIN STORMS COULD FIRE IN THE AFTERNOON OTHERWISE SATURDAY LOOKS LIKE A DRY DAY WITH HEAT AND HUMIDITY UNDER 500 MB HEIGHTS CLOSE TO 590DM. HIGH TEMPERATURES IN THE MID 90S AND DEWPOINTS IN THE MID TO PERHAPS UPPER 60S WOULD COMBINE TO PRODUCE HEAT INDEX VALUES NEAR 100 DEGF IN SOME AREAS. MODELS KEEP MOST OF THE CONVECTION LINKED TO LOW PRESSURE OVER FLORIDA TO OUR SOUTHEAST THROUGH THE WEEKEND. IT STILL BEARS WATCHING. ATMOSPHERE WILL BE HOT AND HUMID...AND NAM12 DEVELOPS CONVECTION NEAR A LEE TROUGH IN THE AFTERNOON AND PROPAGATES THUNDERSTORMS EAST THROUGH THE EVENING. HAVE CHC POPS FOR A GOOD CHUNK OF THE CWA. STILL BELIEVE CONVECTIVE CHANCES WILL CONTINUE INTO EARLY NEXT WEEK. MODELS SHOW MOISTURE AND INSTABILITY...ALONG WITH HEIGHT FALLS AS THE RIDGE BREAKS DOWN AND OUR CWA IS SOMEWHAT INFLUENCED BY A GREAT LAKES/NORTHEAST TROUGH. THIS MAY ALLOW A BOUNDARY TO SINK SOUTH INTO THE CWA EARLY NEXT WEEK AS WELL. THEREFORE...WILL ALLOW FOR DIURNAL CONVECTION THROUGH TUESDAY. CONFIDENCE DECREASES DURING THE MID WEEK. IF A BOUNDARY IS STALLED OVER THE CWA...THEN CONVECTION CHANCES MAY CONTINUE. BUT THERES ENOUGH UNCERTAINTY AND DISAGREEMENT TO NOT MAKE ANY CHANGES TO THE FORECAST WEDNESDAY-THURSDAY ATTM. && .AVIATION /15Z FRIDAY THROUGH TUESDAY/... HIGH RH/S OVRNGHT GRADLY DROPPING VSBYS INTO AT LEAST MVFR AND LOCALIZED IFR COND/S. CALM WINDS AND CLR SKIES AIDING IN THE PROCESS. KMRB/KCHO SHLD REMAIN IN THE 3-5SM RANGE W/ ONLY BRIEF INTERVALS OF LESS THAN 3SM COND/S. SFC HIGH PRES AREA WILL CONT MOVING OFFSHORE...DEVELOPING A 5-10KT SW-S/RLY SFC WIND DRNG THE AFTN HRS. IF CUMULUS FIELD DEVELOPS THIS AFTN...ONLY A STORM OR TWO EXPTD /AND SHORT LIVED/. NO OTHER CONCERNS THRU THE TAF PERIOD. WITH DEWPOINTS ON THE INCREASE...TERMINALS MAY CONTEND WITH MORNING FOG BY SUNDAY MORNING. AFTERNOON/EVENING THUNDERSTORM CHANCES WILL ALSO INCREASE SUNDAY INTO EARLY NEXT WEEK. && .MARINE... WEAK S/RLY CHANNELING W/ SFC HIGH DRIFTING OFFSHORE. NO OTHER CONCERNS ACROSS THE WATERS TODAY. WEAK PRESSURE GRADIENT SHOULD KEEP WINDS BELOW SMALL CRAFT CRITERIA DURING MUCH OF THE LONG TERM. WILL HAVE TO WATCH SOUTHERLY FLOW OVER THE WEEKEND WHICH COMBINED WITH SMALLER SCALE CHANNELING EFFECTS COULD ALLOW WINDS TO INCREASE CLOSE TO SMALL CRAFT ADVISORY CRITERIA. AFTERNOON/EVENING THUNDERSTORM CHANCES WILL ALSO INCREASE SUNDAY INTO EARLY NEXT WEEK. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE. && $$ SYNOPSIS...GMS NEAR TERM...ROGOWSKI SHORT TERM...ROGOWSKI LONG TERM...BPP AVIATION...ROGOWSKI/BPP MARINE...ROGOWSKI/BPP
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
845 PM EDT SAT JUL 19 2008 UPDATED FOR 00Z AVIATION DISCUSSION .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED NEARLY ZONAL FLOW ACROSS THE NORTHERN U.S.. WITHIN THE FLOW THERE ARE A FEW FEATURES OF INTEREST. TWO SHRTWVS ARE APPARENT OVER MN...ONE IN NW AND ANOTHER IN THE CENTRAL PORTION OF THE STATE. THE CENTRAL ONE APPEARS MORE FORMIDABLE...AS NOTED BY A DRIER DRY SLOT IN ITS WAKE. DPVA FROM THESE TWO SHRTWVS...COMBINED WITH RIGHT ENTRANCE REGION FORCING FROM A 60-80KT JET IN FAR WRN ONTARIO IS AIDING IN SHOWERS ACROSS NRN AND EAST CENTRAL MN. A FEW STORMS HAVE ALSO POPPED UP IN EAST CENTRAL MN WITH DAYTIME HEATING. A BREAK IN THE PCPN EXISTS OVER MUCH OF NORTH DAKOTA...EXCEPT IN THE NW PORTION OF THE STATE INTO ERN SASKATCHEWAN WHERE DPVA AHEAD OF A SHRTWV TROUGH/UPPER LOW IS SUPPORTING PCPN THERE. BACK CLOSER TO HOME...A SURFACE HIGH PRESSURE AREA IS OVER NRN ONTARIO. ALTHOUGH THE LOCATION IS USUALLY FAVORABLE FOR DRY AIR ADVECTION...DEWPOINTS STILL AT LEAST REMAIN IN THE 50S. 60S DEWPOINTS CAN BE SEEN OVER WRN/SRN WI AND CENTRAL/SRN MN...WHICH IS WHERE A WARM FRONTAL BOUNDARY EXISTS. DUE TO THE HIGH LOW LEVEL MOISTURE...PLENTY OF DIURNAL CUMULUS HAS DEVELOPED. A CAP SEEN AT 775MB ON THE 18Z TAMDAR SOUNDING FROM SAW IS HELPING TO PREVENT ANY CUMULUS FROM GROWING INTO SHOWERS...DESPITE LOW LEVEL CONVERGENCE FROM LAKE BREEZES. WITH THE 50S DEWPOINTS AROUND...FOG AND STRATUS THAT DEVELOPED ON LAKE SUPERIOR A FEW DAYS AGO HAS GONE NOWHERE...SINCE THE DEWPOINTS ARE AT LEAST 10 DEGREES F HIGHER THAN THE BUOY WATER TEMPS. DAYTIME MIXING HAS HELD THE FOG/STRATUS TO THE NEARSHORE AREAS THIS AFTN. && .SHORT TERM (TONIGHT AND SUNDAY)... 12Z NAM/REGIONAL CANADIAN APPEAR TO HAVE THE BEST HANDLE ON THE TWO SHRTWVS OVER MN...IN ADDITION TO THE CURRENT PCPN FALLING...AND THEREFORE THE FORECAST FOR THE SHORT TERM LEANS TOWARD THERE SOLUTIONS. DID NOT USE THE 12Z GFS/ECMWF DUE TO CONVECTIVE FEEDBACK...WHILE THE UKMET SEEMED WAY TOO WEAK WITH THE SHRTWVS. OUR 12Z LOCAL WRF-ARW RUN DID NOT HAVE A GOOD HANDLE ON THE PCPN...BUT THE NEW 18Z RUN APPEARS TO BE DOING BETTER...IN FACT LOOKING SIMILAR TO THE NAM. THE TWO SHRTWVS MOVE ACROSS THE CWA BY 06Z...BRINGING THE PCPN OVER AT LEAST NRN MN ACROSS. PCPN SHOULD MOVE INTO THE WESTERN U.P....AIDED BY PERSISTENT DPVA AND RIGHT ENTRANCE REGION FORCING. HOWEVER...THE PCPN WILL LIKELY WEAKEN AS IT SPREADS INTO THE CENTRAL SECTIONS WHERE DRIER AIR IS PRESENT (SAW TAMDAR SOUNDING HAD NEARLY A 40C DEWPOINT DEPRESSION AT 650MB). FOCUS THEN SHIFTS BACK TO THE SW WITH CONVECTION DEVELOPING JUST TO THE NORTH OF THE TWIN CITIES. ALL MODELS...EVEN THOSE WITH CONVECTIVE FEEDBACK...SEEM TO SUGGEST AN MCS DEVELOPING OUT OF THIS CONVECTION. THE TRACK OF THIS MCS WOULD BRING IT ACROSS NE WI...PERHAPS SRN UPPER MI AND INTO NRN LOWER MI. HAVE RAISED POPS IN THE SRN U.P. TO LIKELY WITH THAT AREA BEING ON THE NORTH SIDE OF THE MCS. ADDED SOME THUNDER IN THE FORECAST GIVEN UPSTREAM LIGHTNING. THIS PCPN SHOULD EXIT OUT OF THE CWA EARLY SUN MORNING. ONLY SLIGHT ADJUSTMENTS MADE TO LOW TEMPS...WHICH GENERALLY SEEM REASONABLE. HARD TO SAY WHAT IS GOING TO OCCUR ON SUN. THE SHRTWV TROUGH/UPPER LOW IN ALBERTA/SASKATCHEWAN IS PROGGED TO BE MOVING ACROSS CENTRAL CANADA AT THIS TIME. THE LEAD SHRTWV AIDING IN THE PCPN IN SE SASKATCHEWAN LOOKS TO MOVE INTO THE CWA DURING THE AFTN...WHICH WITH SOME LAKE BREEZES EXPECTED MEANS SOME SHOWERS AND POSSIBLY A COUPLE OF THUNDERSTORMS SHOULD DEVELOP. THEREFORE...HIGHEST POPS ARE CONFINED TO THE AFTN...AND THE STRONGEST AREA OF CONVERGENCE WHICH IS LOCATED IN THE EASTERN U.P.. PLENTY OF CLOUDS...ALONG WITH ONSHORE WINDS...MAY MAKE IT DIFFICULT FOR LAKESHORE LOCATIONS TO RISE MUCH. THEREFORE...HAVE COOLED READINGS NEAR THE SHORE. INLAND TEMPS SEEMED REASONABLE...WHERE AT LEAST SOME PARTIAL SUNSHINE SHOULD OCCUR. REGARDING THE FOG/STRATUS ON LAKE SUPERIOR...WITH THE LACK OF ANY SIGNIFICANT DRY AIR AROUND...THE FOG/STRATUS WILL MOVE AROUND THE LAKE BASED ON THE LOW LEVEL WIND DIRECTION. FOLLOWED GENERALLY THE 950MB RH/WIND FIELDS FROM NAM AND LOCAL WRF-ARW RUN WHICH SEEM TO HAVE A GOOD HANDLE ON THE FOG/STRATUS. BASICALLY...LOW LEVEL WIND FIELDS DO NOT CHANGE MUCH...SO ONCE DIURNAL COOLING SETS IN...SOME FOG SHOULD REDEVELOP ON THE KEWEENAW. SOME FOG COULD REDEVELOP TOO IN THE EASTERN U.P....AIDED BY THE MOIST ONSHORE FLOW OFF LAKE SUPERIOR AND ANY RADIATIONAL COOLING THAT CAN OCCUR THERE. EVENING/MIDNIGHT SHIFTS WILL NEED TO MONITOR POSSIBILITY OF DENSE FOG ON THE KEWEENAW. FOG ON LAND WILL DISSIPATE BY NOON AS DAYTIME HEATING HELPS MIX IT OUT. && .LONG TERM (SUN NIGHT THROUGH NEXT SAT)... NAM SHOWING A 500 MB TROUGH IN THE UPPER GREAT LAKES 00Z MON AND THIS DIGS SE MON AND REMAINS INTO TUE WITH THE TROUGH AXIS EAST OF THE AREA BY THEN. NAM BRINGS IN SOME 850-500 MB Q-VECTOR CONVERGENCE WITH SOME MOISTURE SUN NIGHT AND MON. GFS KEEPS IT DRY WITH PCPN STAYING TO THE SOUTH AND WEST. OTHER MODELS INCLUDING THE ECMWF GO MORE TOWARDS THE NAM AND KEEP PCPN IN FOR SUN NIGHT AND MON...SO KEPT IN LOW CHANCE POPS FOR SUN NIGHT AND MON MORNING AND THEN SLIGHT CHANCE POPS IN THE AFTERNOON. OVERALL...DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST FOR WEATHER OR FOR TEMPERATURES. IN THE EXTENDED...FOLLOWED CLOSE TO 00Z ECMWF FOR THIS FORECAST WHICH SHOWS AN UPPER LEVEL 500 MB RIDGE IN CONTROL FOR MOST OF THE PERIOD. THERE IS A SHORTWAVE THAT MOVES THROUGH THE RIDGE AND MOVES ACROSS SOUTHERN ONTARIO AND MANITOBA THU NIGHT THROUGH FRI NIGHT AND PUT IN CHANCE POPS AS A DIEING COLD FRONT MOVES THROUGH THE AREA. OTHERWISE...IT WILL BE DRY WITH TEMPERATURES NEAR NORMAL. DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST. && .AVIATION (FOR THE 00Z TAF ISSUANCE)... FOG/STRATUS AGAIN IS THE MAIN CONCERN FOR THE TAFS AS FOG PRESISTS OVER LAKE SUPERIOR. WITH EASTERLY UPSLOPE WINDS EXPECTED AT KCMX LOOK FOR CONDITIONS TO LOWER TO LIFR LATER THIS EVENING AND REMAIN THAT WAY UNTIL LATE SUN MORNING. AT KSAW...WITH A LIGHT NE WIND EXPECTED LOOK FOR SOME MVFR VIS AND IFR CIGS JUST AFTER MIDNIGHT AS LAKE STRATUS MOVES IN. AT BOTH SITES...CIGS/VSBYS SHOULD IMPROVE SUN MORNING AS DAYTIME HEATING GRADUALLY LIFTS THE BASES OF THE LOW CLOUDS. EXPECT LIGHT RAIN AHEAD OF AN UPR DISTURBANCE TO DISSIPATE SOME AS IT MOVES E INTO DRIER AIR IN PLACE OVER THE UPR GREAT LAKES. HOWEVER...WOULD STILL EXPECT SOME LIGHT RAIN TO REACH KCMX BY 03Z AND KSAW AROUND 09Z. LIGHT SHOWERS WILL LIKELY END BY LATE MORNING AT BOTH TAF SITES AS SFC RIDGE BEGINS TO BUILD IN FROM THE WEST. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... LACK OF DRY AIR AROUND LAKE SUPERIOR MEANS FOG WILL HANG AROUND FOR AWHILE...SHIFTING AROUND THE LAKE BASED ON WIND DIRECTION. HAVE EXTENDED MOST DENSE FOG ADVISORIES THROUGH SUNDAY...BUT MAY HAVE TO BE EXTENDED INTO MONDAY AS WELL...DEPENDING ON TIMING OF WHEN DRIER AIR CAN COME SOUTH OUT OF NORTHERN ONTARIO. ALTHOUGH FOG IS PROBLEMATIC...GENERAL LIGHT PRESSURE GRADIENT EXPECTED ACROSS LAKE SUPERIOR THROUGH THE FORECAST MEANS WIND SPEEDS SHOULD STAY AT 20 KT OR LESS. STRONGEST WINDS EXPECTED TONIGHT INTO TOMORROW OVER FAR WESTERN LAKE SUPERIOR...DUE TO FUNNELING NE FLOW BTWN HIGH PRESSURE IN NORTHERN ONTARIO AND LOW PRESSURE CROSSING WI. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR... DENSE FOG ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR LSZ251-267. DENSE FOG ADVISORY UNTIL 8 PM EDT /7 PM CDT/ SUNDAY FOR LSZ162- 243>250-263>266. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...GJM AVIATION...VOSS MARINE...AJ
AREA FORECAST DISCUSSION
NWS MARQUETTE MI
409 PM EDT SAT JUL 19 2008 .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED NEARLY ZONAL FLOW ACROSS THE NORTHERN U.S.. WITHIN THE FLOW THERE ARE A FEW FEATURES OF INTEREST. TWO SHRTWVS ARE APPARENT OVER MN...ONE IN NW AND ANOTHER IN THE CENTRAL PORTION OF THE STATE. THE CENTRAL ONE APPEARS MORE FORMIDABLE...AS NOTED BY A DRIER DRY SLOT IN ITS WAKE. DPVA FROM THESE TWO SHRTWVS...COMBINED WITH RIGHT ENTRANCE REGION FORCING FROM A 60-80KT JET IN FAR WRN ONTARIO IS AIDING IN SHOWERS ACROSS NRN AND EAST CENTRAL MN. A FEW STORMS HAVE ALSO POPPED UP IN EAST CENTRAL MN WITH DAYTIME HEATING. A BREAK IN THE PCPN EXISTS OVER MUCH OF NORTH DAKOTA...EXCEPT IN THE NW PORTION OF THE STATE INTO ERN SASKATCHEWAN WHERE DPVA AHEAD OF A SHRTWV TROUGH/UPPER LOW IS SUPPORTING PCPN THERE. BACK CLOSER TO HOME...A SURFACE HIGH PRESSURE AREA IS OVER NRN ONTARIO. ALTHOUGH THE LOCATION IS USUALLY FAVORABLE FOR DRY AIR ADVECTION...DEWPOINTS STILL AT LEAST REMAIN IN THE 50S. 60S DEWPOINTS CAN BE SEEN OVER WRN/SRN WI AND CENTRAL/SRN MN...WHICH IS WHERE A WARM FRONTAL BOUNDARY EXISTS. DUE TO THE HIGH LOW LEVEL MOISTURE...PLENTY OF DIURNAL CUMULUS HAS DEVELOPED. A CAP SEEN AT 775MB ON THE 18Z TAMDAR SOUNDING FROM SAW IS HELPING TO PREVENT ANY CUMULUS FROM GROWING INTO SHOWERS...DESPITE LOW LEVEL CONVERGENCE FROM LAKE BREEZES. WITH THE 50S DEWPOINTS AROUND...FOG AND STRATUS THAT DEVELOPED ON LAKE SUPERIOR A FEW DAYS AGO HAS GONE NOWHERE...SINCE THE DEWPOINTS ARE AT LEAST 10 DEGREES F HIGHER THAN THE BUOY WATER TEMPS. DAYTIME MIXING HAS HELD THE FOG/STRATUS TO THE NEARSHORE AREAS THIS AFTN. && .SHORT TERM (TONIGHT AND SUNDAY)... 12Z NAM/REGIONAL CANADIAN APPEAR TO HAVE THE BEST HANDLE ON THE TWO SHRTWVS OVER MN...IN ADDITION TO THE CURRENT PCPN FALLING...AND THEREFORE THE FORECAST FOR THE SHORT TERM LEANS TOWARD THERE SOLUTIONS. DID NOT USE THE 12Z GFS/ECMWF DUE TO CONVECTIVE FEEDBACK...WHILE THE UKMET SEEMED WAY TOO WEAK WITH THE SHRTWVS. OUR 12Z LOCAL WRF-ARW RUN DID NOT HAVE A GOOD HANDLE ON THE PCPN...BUT THE NEW 18Z RUN APPEARS TO BE DOING BETTER...IN FACT LOOKING SIMILAR TO THE NAM. THE TWO SHRTWVS MOVE ACROSS THE CWA BY 06Z...BRINGING THE PCPN OVER AT LEAST NRN MN ACROSS. PCPN SHOULD MOVE INTO THE WESTERN U.P....AIDED BY PERSISTENT DPVA AND RIGHT ENTRANCE REGION FORCING. HOWEVER...THE PCPN WILL LIKELY WEAKEN AS IT SPREADS INTO THE CENTRAL SECTIONS WHERE DRIER AIR IS PRESENT (SAW TAMDAR SOUNDING HAD NEARLY A 40C DEWPOINT DEPRESSION AT 650MB). FOCUS THEN SHIFTS BACK TO THE SW WITH CONVECTION DEVELOPING JUST TO THE NORTH OF THE TWIN CITIES. ALL MODELS...EVEN THOSE WITH CONVECTIVE FEEDBACK...SEEM TO SUGGEST AN MCS DEVELOPING OUT OF THIS CONVECTION. THE TRACK OF THIS MCS WOULD BRING IT ACROSS NE WI...PERHAPS SRN UPPER MI AND INTO NRN LOWER MI. HAVE RAISED POPS IN THE SRN U.P. TO LIKELY WITH THAT AREA BEING ON THE NORTH SIDE OF THE MCS. ADDED SOME THUNDER IN THE FORECAST GIVEN UPSTREAM LIGHTNING. THIS PCPN SHOULD EXIT OUT OF THE CWA EARLY SUN MORNING. ONLY SLIGHT ADJUSTMENTS MADE TO LOW TEMPS...WHICH GENERALLY SEEM REASONABLE. HARD TO SAY WHAT IS GOING TO OCCUR ON SUN. THE SHRTWV TROUGH/UPPER LOW IN ALBERTA/SASKATCHEWAN IS PROGGED TO BE MOVING ACROSS CENTRAL CANADA AT THIS TIME. THE LEAD SHRTWV AIDING IN THE PCPN IN SE SASKATCHEWAN LOOKS TO MOVE INTO THE CWA DURING THE AFTN...WHICH WITH SOME LAKE BREEZES EXPECTED MEANS SOME SHOWERS AND POSSIBLY A COUPLE OF THUNDERSTORMS SHOULD DEVELOP. THEREFORE...HIGHEST POPS ARE CONFINED TO THE AFTN...AND THE STRONGEST AREA OF CONVERGENCE WHICH IS LOCATED IN THE EASTERN U.P.. PLENTY OF CLOUDS...ALONG WITH ONSHORE WINDS...MAY MAKE IT DIFFICULT FOR LAKESHORE LOCATIONS TO RISE MUCH. THEREFORE...HAVE COOLED READINGS NEAR THE SHORE. INLAND TEMPS SEEMED REASONABLE...WHERE AT LEAST SOME PARTIAL SUNSHINE SHOULD OCCUR. REGARDING THE FOG/STRATUS ON LAKE SUPERIOR...WITH THE LACK OF ANY SIGNIFICANT DRY AIR AROUND...THE FOG/STRATUS WILL MOVE AROUND THE LAKE BASED ON THE LOW LEVEL WIND DIRECTION. FOLLOWED GENERALLY THE 950MB RH/WIND FIELDS FROM NAM AND LOCAL WRF-ARW RUN WHICH SEEM TO HAVE A GOOD HANDLE ON THE FOG/STRATUS. BASICALLY...LOW LEVEL WIND FIELDS DO NOT CHANGE MUCH...SO ONCE DIURNAL COOLING SETS IN...SOME FOG SHOULD REDEVELOP ON THE KEWEENAW. SOME FOG COULD REDEVELOP TOO IN THE EASTERN U.P....AIDED BY THE MOIST ONSHORE FLOW OFF LAKE SUPERIOR AND ANY RADIATIONAL COOLING THAT CAN OCCUR THERE. EVENING/MIDNIGHT SHIFTS WILL NEED TO MONITOR POSSIBILITY OF DENSE FOG ON THE KEWEENAW. FOG ON LAND WILL DISSIPATE BY NOON AS DAYTIME HEATING HELPS MIX IT OUT. && .LONG TERM (SUN NIGHT THROUGH NEXT SAT)... NAM SHOWING A 500 MB TROUGH IN THE UPPER GREAT LAKES 00Z MON AND THIS DIGS SE MON AND REMAINS INTO TUE WITH THE TROUGH AXIS EAST OF THE AREA BY THEN. NAM BRINGS IN SOME 850-500 MB Q-VECTOR CONVERGENCE WITH SOME MOISTURE SUN NIGHT AND MON. GFS KEEPS IT DRY WITH PCPN STAYING TO THE SOUTH AND WEST. OTHER MODELS INCLUDING THE ECMWF GO MORE TOWARDS THE NAM AND KEEP PCPN IN FOR SUN NIGHT AND MON...SO KEPT IN LOW CHANCE POPS FOR SUN NIGHT AND MON MORNING AND THEN SLIGHT CHANCE POPS IN THE AFTERNOON. OVERALL...DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST FOR WEATHER OR FOR TEMPERATURES. IN THE EXTENDED...FOLLOWED CLOSE TO 00Z ECMWF FOR THIS FORECAST WHICH SHOWS AN UPPER LEVEL 500 MB RIDGE IN CONTROL FOR MOST OF THE PERIOD. THERE IS A SHORTWAVE THAT MOVES THROUGH THE RIDGE AND MOVES ACROSS SOUTHERN ONTARIO AND MANITOBA THU NIGHT THROUGH FRI NIGHT AND PUT IN CHANCE POPS AS A DIEING COLD FRONT MOVES THROUGH THE AREA. OTHERWISE...IT WILL BE DRY WITH TEMPERATURES NEAR NORMAL. DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... FOG/STRATUS AGAIN IS THE MAIN CONCERN FOR THE TAFS. FOG IS QUITE EXPANSIVE ON LAKE SUPERIOR...AND WITH THE LACK OF ANY DRY AIR TO HELP MIX THE LAKE SUPERIOR FOG OUT DURING THE NEXT 24 HOURS (IN FACT SOME RAIN MAY MOVE ACROSS TO MAINTAIN FOG)...THE FOG SHOULD JUST SHIFT AROUND THE LAKE BY THE LOW LEVEL WINDS. THEREFORE...WITH EASTERLY UPSLOPE WINDS EXPECTED TO PERSIST AT CMX THROUGH THE NEXT 24 HOURS...HAVE WENT MORE PESSIMISTIC...BRINGING VSBYS/CIGS DOWN THIS EVNG. THE LOWERING VSBYS AND CIGS WILL ALSO BE AIDED BY NOCTURNAL COOLING. HAVE WENT AS LOW AS LIFR ON BOTH...BUT WOULD NOT BE SURPRISED IF THEY NEED TO BE LOWERED TO VLIFR. AT SAW...LOW LEVEL WIND FIELD A LITTLE MORE TRICKY TO FORECAST...WITH POSSIBILITIES OF NE TO SE. GIVEN THAT HIGH PRESSURE STAYS TO THE NORTH OVER NORTHERN ONTARIO AND LOW PRESSURE IS PROGGED TO CROSS WI AND LOWER MI...A NE WIND WOULD BE FAVORED. THEREFORE...HAVE BROUGHT IN SOME MVFR VIS AND IFR CIGS JUST AFTER MIDNIGHT AS LAKE STRATUS MOVES IN. AT BOTH SITES...CIGS/VSBYS SHOULD IMPROVE DURING THE MORNING AS DAYTIME HEATING GRADUALLY MIXES THE BASES OF THE LOW CLOUDS UP...SIMILAR TO TODAY. REGARDING PCPN...SHOWERS ACROSS CENTRAL MN ASSOCIATED WITH AN UPPER LEVEL DISTURBANCE SHOULD CONTINUE MAKING THERE MARCH NE...PROBABLY MOVING INTO CMX AROUND MIDNIGHT AND EXITING SOMETIME LATE TONIGHT. SAW COULD BE SPLIT BETWEEN TWO DIFFERENT PCPN AREAS...THE ONE NEAR CMX AND ANOTHER CROSSING THE SRN U.P.. THEREFORE HAVE NOT INCLUDED ANY PCPN IN THE TAF THERE. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... LACK OF DRY AIR AROUND LAKE SUPERIOR MEANS FOG WILL HANG AROUND FOR AWHILE...SHIFTING AROUND THE LAKE BASED ON WIND DIRECTION. HAVE EXTENDED MOST DENSE FOG ADVISORIES THROUGH SUNDAY...BUT MAY HAVE TO BE EXTENDED INTO MONDAY AS WELL...DEPENDING ON TIMING OF WHEN DRIER AIR CAN COME SOUTH OUT OF NORTHERN ONTARIO. ALTHOUGH FOG IS PROBLEMATIC...GENERAL LIGHT PRESSURE GRADIENT EXPECTED ACROSS LAKE SUPERIOR THROUGH THE FORECAST MEANS WIND SPEEDS SHOULD STAY AT 20 KT OR LESS. STRONGEST WINDS EXPECTED TONIGHT INTO TOMORROW OVER FAR WESTERN LAKE SUPERIOR...DUE TO FUNNELING NE FLOW BTWN HIGH PRESSURE IN NORTHERN ONTARIO AND LOW PRESSURE CROSSING WI. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR... DENSE FOG ADVISORY UNTIL 6 PM EDT THIS AFTERNOON FOR LSZ251-267. DENSE FOG ADVISORY UNTIL 8 PM EDT /7 PM CDT/ SUNDAY FOR LSZ162- 243>250-263>266. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...GJM AVIATION...AJ MARINE...AJ
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
149 PM EDT SAT JUL 19 2008 UPDATED AVIATION DISCUSSION FOR 18Z TAF ISSUANCE .UPDATE... ISSUED AT 1158 AM EDT... FOG OFF LAKE SUPERIOR CONTINUES TO BE AN ISSUE...THOUGH IT APPEARS DAYTIME HEATING IS DOING ITS JOB IN BRINGING VISIBILITIES UP ON LAND AREAS...EVEN ON THE KEWEENAW WITH UPSLOPING WINDS AT CMX. 15Z TAMDAR SOUNDING FROM SAW INDICATES TOO WHY THE FOG IS DISSIPATING WITH DRY AIR ABOVE 900MB STARTING TO MIX DOWN. THEREFORE DENSE FOG ADVISORIES HAVE BEEN CANCELLED OVER LAND. WEBCAMS STILL INDICATE THE FOG ON LAKE SUPERIOR IS DENSE...AND COVERS MUCH OF THE U.S. WATERS OF LAKE SUPERIOR. HAVE EXPANDED THE DENSE FOG ADVISORY INTO FAR WESTERN LAKE SUPERIOR WITH A SHIP REPORT NEAR DEVILS ISLAND INDICATING VSBYS LESS THAN 1/4SM. FOG MAY BE ABLE TO DISSIPATE SOME THIS AFTERNOON AS DOWNSLOPING DRIER AIR COMES OFF NE ONTARIO...AS INDICATED BY NAM 950MB RH FIELDS WHICH CONTINUE TO HAVE THE BEST REPRESENTATION OF THE FOG. OTHER ISSUE THIS AFTERNOON IS POSSIBLE LAKE BREEZE CONVERGENCE CONVECTION DEVELOPING OVER THE SOUTHERN U.P.. OUR LOCAL WRF-ARW RUN WITH THE KF SCHEME AND THE RUC DEVELOP SOME ISOLATED STORMS LATE THIS AFTN. HOWEVER...SOUNDINGS SEEM A LITTLE SUSPICIOUS... PARTICULARLY WITH THE AVAILABLE LOW LEVEL MOISTURE. MODIFYING THE 15Z TAMDAR SOUNDING FROM SAW AND A 12Z NAM SOUNDING SUGGESTS SOME CAP AS DEWPOINTS MIX DOWN INTO THE MID/UPPER 50S. THEREFORE HAVE NOT INCLUDED ANY POPS AT THIS TIME. WILL BE MONITORING FOG THIS AFTERNOON. IF IT DOES NOT DISSIPATE AS MUCH AS THE NAM IS SUGGESTING...WE MAY NEED DENSE FOG ADVISORIES AGAIN FOR AT LEAST THE KEWEENAW ONCE DIURNAL COOLING SETS IN. WILL ALSO HAVE TO WATCH FOG ON CENTRAL LAKE MICHIGAN AS A WEBCAM IN ALGOMA WI SHOWS DENSE FOG THERE...AND WITH ESE WINDS DEVELOPING IN THE LOW LEVELS TONIGHT...THIS COULD GET ADVECTED TOWARDS SE UPPER MI. PREVIOUS UPDATE ISSUED AT 911 AM EDT... ADDED EASTERN ALGER...SCHOOLCRAFT AND LUCE COUNTIES TO THE DENSE FOG ADVISORY PER ERY AND ISQ OBS...IN ADDITION TO LATEST WEBCAM AT SENEY. HOWEVER...FOG THERE SHOULD NOT LAST AS LONG AS DOWNSLOPING NE WIND ASSISTS WITH THE SUN TO HELP MIX IT OUT. IN ADDITION...ADDED A FEW EXTRA MARINE AREAS TO THE DENSE FOG ADVISORY WITH A REPORT OF 1/4SM AT TWO HEART AND WEBCAM OFF EAGLE HARBOR SHOWING FOG JUST OFFSHORE. ANOTHER DENSE FOG ADVISORY MAY BE NEEDED FOR FAR WESTERN LAKE SUPERIOR GIVEN VISIBLE SATELLITE TRENDS. WILL INCREASE FOG COVERAGE THERE FOR NOW. PREVIOUS UPDATE ISSUED AT 815 AM EDT... DENSE FOG THAT DEVELOPED OVER THE COLD WATERS OF LAKE SUPERIOR LAST NIGHT IS BEING ADVECTED SOUTH IN A HURRY AS WEAK HIGH PRES CENTER NORTH OF LAKE SUPERIOR DROPS SOUTH. NOT MUCH TO GO ON FM OBSERVATION STANDPOINT...BUT LAST VIS/FOG IMAGERY OF NIGHT SHOWED THE STRATUS/FOG SHIFTING SOUTH AND WEB CAMS FM EAGLE RIVER...COPPER HARBOR...AND AT CENTRAL IN HIGHER TERRAIN OF KEWEENAW COUNTY ALL SHOWED NEAR ZERO VSBY WITHIN LAST HR. FOLLOWED LOW LEVEL RH PROGS FM NAM AS IT HAD A GOOD HANDLE. INDICATIONS ARE THAT THE FOG WILL AFFECT KEWEENAW ALL DAY...ONLY BOLSTERED BY AN INCREASINGLY FAVORABLE EASTERLY UPSLOPE WIND. WENT WITH DENSE FOG ADVY ALL DAY THERE AND ALSO OVR ALL OF CNTRL LK SUPERIOR AND ADJACENT NSH ZONES FM TIP OF KEWEENAW TO GRAND MARAIS. ELSEWHERE...ALONG LAKE SUPERIOR EAST OF KEWEENAW TO NORTHERN LUCE COUNTY...EXPECT FOG TO BE DENSE THIS MORNING BUT THEN TO TRY TO MIX OUT THIS AFTN WITH LOW LEVEL MIXING OVR LAND. THUS...DID NOT GO WITH DENSE FOG ADVY AWAY FM THE KEWEENAW. ONCE WE GET A HANDLE ON HOW THE FOG IS UNFOLDING THIS MORNING...FURTHER DENSE FOG ADVYS MAY BE NEEDED. MADE APPROPRIATE ADJUSTMENTS TO SKY/WX AND LOWERED TEMPS SOME MORE ALONG THE SHORE WITH PERSISTENT ONSHORE FLOW. && .DISCUSSION... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW ZONAL FLOW OVER THE NRN TIER CONUS. QUIET NGT OVER THE CWA WITH SFC RDG OVER ONTARIO NOSING TOWARD THE FA AND STABLE AIRMASS WITH WELL DEFINED CAP ARND H7 AS SHOWN ON 00Z INL RAOB/TAMDAR SDNG FM SAW. CONVECTION THAT IMPACTED THE SE ZNS ALG TROF EARLIER IN THE EVNG HAVE WEAKENED/ PUSHED TO THE S WITH THAT TROF. SINCE LLVLS NEVER DRIED SGNFTLY IN THE WAKE OF THE TROF...SOME FOG HAS DVLPD. A PAIR OF SHRTWVS OF INTERNEST NOTED UPSTREAM. THE FIRST OF THESE IS PUSHING INTO THE NRN PLAINS AND CAUSING QUITE A BIT OF SHRA/TSRA IN THE DAKOTAS. HI CLDS IN ADVANCE OF THESE SHRA ARE PUSHING INTO MN. ANOTHER TRAILING SHRTWV IS MOVING EWD ALG THE CNDN BORDER JUST N OF MT. MAIN FCST CONCERNS THIS PACKAGE ARE PCPN CHCS THIS WEEKEND INTO EARLY NEXT WEEK ASSOCIATED WITH COMPLEX INTERACTION OF PAIR OF SHRTWVS UPSTREAM. FOR TDAY...SHRTWV RDG/SFC HI PRES RDG AXIS IS FCST TO BE OVHD THIS MRNG. EXPECT ANY FOG TO BURN OFF QUICKLY WITH RETURN OF DIURNAL HTG. SHRTWV NOW MOVING INTO THE NRN PLAINS IS PROGGED TO REACH NRN MN BY 00Z SUN. LATEST MODEL GUIDANCE HAS TRENDED SLOWER TO BRING DEEP MSTR EWD WITH MORE RESILIENT HI PRES/MID LVL DRY AIR. WL RESTRICT MENTION OF SCHC POPS TO AFT 21Z AND OVER ONLY WRN LK SUP WHERE 12Z ECMWF/00Z GFS SHOW SOME UPR DVGC/DEEP LYR H85-3 QVECTOR CNVGC ARRIVING IN ADVANCE OF THE SHRTWV BY 00Z. OTRW...MIXING TO H775 OR SO ON GFS/NAM FCST SDNGS YIELDS HI TEMPS IN THE MID-UPR 70S AWAY FM LK MODERATION THAT WL BE MAXIMIZED IN AREAS FAVORED BY E-NE WINDS S OF HI PRES CENTER IN ONTARIO. FOR TNGT...00Z NAM/GFS/UKMET SHOW INITIAL SHRTWV APRCHG FM THE W SPLITTING WITH SRN PIECE SUPPORTING MORE SUPPRESSED WARM FNT/SFC LO TRACKING THRU WI THAT WOULD RESULT IN INTERCEPTION OF MOST SGNFT MSTR S OF THE CWA. 00Z CNDN MODEL MORE SIMILAR TO THE 12Z ECMWF SHOWING A MORE COHESIVE SHRTWV COMING RIGHT AT THE FA WITH HIGHER QPF OVER ALL BUT THE ERN ZNS...WHICH ALL GUIDANCE EXCEPT 12Z ECMWF INDICATE WL STAY DRY. DESPITE ITS HIER QPF...EVEN THE 12Z ECMWF HINTS AT WARM FNT WELL TO THE S...WITH APRNT RELIANCE ON UPR DVGC IN RRQ OF SUBTLE H3 JET MAX IN SE CAN TO GENERATE PCPN OVER THE FA WELL N OF THIS BNDRY. OVERALL...CUT POPS A BIT ESPECIALLY OVER E...WHERE EVEN THE STRONGER CNDN MODEL IS DRY THRU 12Z SUN AND ELY FLOW OUT OF DRY HUDSON BAY HI PRES WOULD FURTHER REDUCE PCPN CHCS. SINCE EVEN THE MOISTER ECWMF SHOWS SSI GREATER THAN 0 OVER THE ENTIRE FA... REMOVED ALL MENTION OF TS. TRAILING SHRTWV NOW JUST N OF MT PROGGED TO REACH NRN MN BY 00Z MON. THE APRCH OF THIS SYS WL MAINTAIN UPR TROFFINESS...BUT GUIDANCE (INCLUDING THE 12Z ECMWF) SHOWS MORE OF AN ACYC FLOW TO THE N OF A WEAKER...MORE SUPPRESSED LO FARTHER S. THE 00Z CNDN IS THE ONLY MODEL SHOWING A DEEPER LO FARTHER N WITH A WELL DEFINED CYC NE FLOW. OPTED TO GO WITH A BLANKET 30 POP THRU THE ENTIRE DAY AND ADD A SCHC OF AFTN TS INLAND FM LK MODERATION DESPITE RATHER MODEST LAPSE RATES SHOWN BY GFS FCST SDNGS. NAM FCST DWPTS INTO THE MID 60S SEEM UNRSNBL CONSIDERING PLACEMENT OF WARM FNT TO THE S AND LACK OF ANY STRG LLVL ADVCTN WITH HUDSON BAY HI STILL LINGERING. WL MAINTAIN GOING 30 POP SUN NGT AS SHRTWV/HINT OF H5 THERMAL TROF SWINGS SE ACRS THE UPR LKS... ALBEIT IN ABSENCE OF DIURNAL HTG. HGTS BEGIN TO RISE SLOWLY ON MON ONCE SHRTWV PULLS TO THE E...BUT SLOWED DOWN DEPARTURE OF CHC POPS ON MON TO REFLECT MORE PERSISTENT MID LVL MSTR/LOWER H5 TEMPS SHOWN BY 00Z NAM/GFS/UKMET THRU THE DAY. WL MAINTAINED DRY FCST FOR MON NGT WITH DEPARTURE OF UPR TROF AND DEEP MSTR/LACK OF DIURNAL HTG. COORDINATED WITH DLH/GRB/LOT/APX. && .AVIATION (FOR THE 18Z TAF ISSUANCE)... FOG/STRATUS AGAIN IS THE MAIN CONCERN FOR THE TAFS. FOG IS QUITE EXPANSIVE ON LAKE SUPERIOR...AND WITH THE LACK OF ANY DRY AIR TO HELP MIX THE LAKE SUPERIOR FOG OUT DURING THE NEXT 24 HOURS (IN FACT SOME RAIN MAY MOVE ACROSS TO MAINTAIN FOG)...THE FOG SHOULD JUST SHIFT AROUND THE LAKE BY THE LOW LEVEL WINDS. THEREFORE...WITH EASTERLY UPSLOPE WINDS EXPECTED TO PERSIST AT CMX THROUGH THE NEXT 24 HOURS...HAVE WENT MORE PESSIMISTIC...BRINGING VSBYS/CIGS DOWN THIS EVNG. THE LOWERING VSBYS AND CIGS WILL ALSO BE AIDED BY NOCTURNAL COOLING. HAVE WENT AS LOW AS LIFR ON BOTH...BUT WOULD NOT BE SURPRISED IF THEY NEED TO BE LOWERED TO VLIFR. AT SAW...LOW LEVEL WIND FIELD A LITTLE MORE TRICKY TO FORECAST...WITH POSSIBILITIES OF NE TO SE. GIVEN THAT HIGH PRESSURE STAYS TO THE NORTH OVER NORTHERN ONTARIO AND LOW PRESSURE IS PROGGED TO CROSS WI AND LOWER MI...A NE WIND WOULD BE FAVORED. THEREFORE...HAVE BROUGHT IN SOME MVFR VIS AND IFR CIGS JUST AFTER MIDNIGHT AS LAKE STRATUS MOVES IN. AT BOTH SITES...CIGS/VSBYS SHOULD IMPROVE DURING THE MORNING AS DAYTIME HEATING GRADUALLY MIXES THE BASES OF THE LOW CLOUDS UP...SIMILAR TO TODAY. REGARDING PCPN...SHOWERS ACROSS CENTRAL MN ASSOCIATED WITH AN UPPER LEVEL DISTURBANCE SHOULD CONTINUE MAKING THERE MARCH NE...PROBABLY MOVING INTO CMX AROUND MIDNIGHT AND EXITING SOMETIME LATE TONIGHT. SAW COULD BE SPLIT BETWEEN TWO DIFFERENT PCPN AREAS...THE ONE NEAR CMX AND ANOTHER CROSSING THE SRN U.P.. THEREFORE HAVE NOT INCLUDED ANY PCPN IN THE TAF THERE. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... FOG IS STUBBORN TO DISSIPATE...BUT IS MOST RESILIENT OVR COOLER WATERS OF ERN LAKE SUPERIOR. EXPECT THE FOG TO GRADUALLY LIFT THROUGH THE DAY WITH INCREASING WINDS AND MIXING. STRONGEST WINDS THROUGH NEXT COUPLE DAYS OCCUR OVR FAR WEST LAKE SUPERIOR WITH NE WINDS FUNNELING DOWN TOWARD HEAD OF LAKE SUPERIOR AS WAVE OF LOW PRESSURE SLIDES BY JUST TO THE SOUTH. SINCE RIDGE OVR LAKE SUPERIOR IS FAIRLY WEAK LEADING TO A WEAKER PRESSURE GRADIENT...WINDS SHOULD NOT EXCEED 20 KNOTS. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR... DENSE FOG ADVISORY UNTIL 6 PM EDT /5 PM CDT/ THIS AFTERNOON FOR LSZ162-243>251-263>267. LAKE MICHIGAN...NONE. && $$ UPDATE...JLA/AJ DISCUSSION...KC AVIATION...AJ MARINE...JLA
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
800 AM EDT FRI JUL 18 2008 UPDATED AVIATION DISCUSSION FOR 12Z TAFS .DISCUSSION (405 AM EDT)... 00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW ZONAL FLOW ACRS THE NRN TIER CONUS ON NRN FLANK OF SUMMER-TIME RDG OVER THE SRN STATES. DISTURBANCE RESPONSIBLE FOR THE SHRA/TSRA YDAY IS NOW SHIFTING E THRU SE CAN AND HAS TAKEN THE BULK OF THE DEEP MSTR/ PCPN WITH IT. ALTHOUGH DRIER AIR IS SPRDG IN ALF FM THE W...LLVL MSTR LINGERS AHEAD OF ANOTHER SHRTWV NOW JUST E OF LK WINNIPEG AND ITS ATTENDANT COOL FNT PRESSING EWD THRU MN. SO SOME FOG AND ST HAS DVLPD OVER THE FA UNDER THE MID LVL DRYING. ISOLD SHRA/TSRA NOTED AHEAD OF THE COOL FNT MOVING IN FM THE W...BUT THIS ACTIVITY APPEARS TO BE WANING WITH THE LOSS OF DIURNAL HTG AND SOME MID LVL DRYING/CAPPING NOTED ON THE 00Z MPX/INL RAOBS. SKIES ARE MOCLR OVER THE NRN PLAINS UNDER HI PRES RDG TO THE W OF LK WINNIPEG SHRTWV AND WHERE H7/5 DEWPT DEPRESSIONS ARE 10 TO 20C. NEXT SHRTWVS OF CONCERN EMBEDDED WITHIN ZONAL FLOW ARE OVER THE PAC NW/BRITISH COLUMBIA. MAIN FCST CONCERNS TDAY ARE FOG/ST TRENDS THIS MRNG ALONG WITH ANY CHC OF SHRA ASSOCIATED WITH LK WINNIPEG SHRTWV. FOCUS SHIFTS TO MAINLY TEMPS TNGT/SAT AND THEN TO TIMING NEXT CHC OF PCPN ACCOMPANYING SHRTWVS NOW IN THE PAC NW. FOR TDAY...EXPECT FOG THIS MRNG TO BURN OFF WITH RETURN OF DIURNAL HTG. OTRW...SHRTWV NOW OVER LK WINNIPEG PROGGED TO REACH NRN LK SUP AT 18Z TDAY AND THEN THE QUEBEC/ONTARIO BORDER BY 00Z SAT. CONCERN IS THAT THERE MAY BE ENUF INSOLATION TO POP SOME CNVCTN OVER THE SCNTRL AND E WHERE PASSING COOL FNT MAY INTERACT WITH LK BREEZES IN SPITE OF DNVA/DRYING ALF IN THE WAKE OF DEPARTING SHRTWV OVERWHELMS ANY SB INSTABILITY. LOCAL WRF-ARW MODEL RUN WITH KF CONVECTION SCHEME AND NAM HINT ISOLD SHRA/TSRA WL DVLP THIS AFTN OVER THE SCNTRL AND/OR E. MODIFIED SDNG NEAR ESC FOR 80/65 YIELDS SB CAPE NEAR 1100 J/KG. BUT WL GO NO MORE THAN A 20 POP GIVEN MODEST LAPSE RATES/HINT AT SOME MID LVL CAPPING/KINX FCST ARND 25. HI PRES RDG/DRY AIR WL DOMINATE UNDER SHRTWV RDGING...SO EXPECT A TRANQUIL NGT WITH NOTHING MORE THAN SOME HI CLD SPILLING INTO THE UPR GRT LKS IN ZONAL FLOW ALF. VARIOUS MODEL MOS FCSTS ARE SIMILAR SHOWING THE MERCURY BOTTOMING OUT NEAR 50 OVER THE INTERIOR...AND THIS SEEMS RSNBL. WL THROW IN PTCHY FOG ACRS THE INTERIOR AREAS. SGFNT MODEL DIFFERENCES BCM APRNT ON SAT AS 00Z NAM FOLLOWS LEAD OF 12Z ECMWF AND BRINGS A SHRTWV NOW IN THE PAC NW QUICKLY E WITH FAIRLY SHARP DPVA/DEEP LYR QVECTOR CNVGC/DEEP MSTR MOVING INTO THE W LATE IN THE DAY. THE GFS ON THE OTHER HAND IS MUCH WEAKER WITH THIS SHRTWV AND FARTHER S SO THAT SFC HI PRES/DRY AIR IS MORE RESILIENT. SINCE THE 00Z CNDN/UKMET MODELS SUPPORT THE NAM SOLN...WL TEND TOWARD THAT SCENARIO...WHICH IS CLOSER TO GOING FCST ALBEIT A BIT SLOWER WITH ARRIVAL OF DYNAMICS/DEEP MSTR/QPF. SINCE ALL GUIDANCE IS DRY THRU 18Z...CUT ALL POPS IN THAT TIME PD AND LOWERED THE NUMBERS IN THE 18Z-24Z TIME PD AS WELL...MAINTAINING SCHC POPS ONLY OVER WRN LK SUP/WI BORDER. FAVORED 00Z NAM/UKMET/CNDN AND 12Z ECMWF MODELS SHOW UPR DVGC/DPVA/ DEEP LYR QVECTOR CNVGC/DEEP MSTR IN LEFT EXIT OF SUPPORTING JET MAX OF SHRTWV SHIFTING EWD ACRS THE FA SAT NGT. BUMPED UP POPS ABOUT 10 PERCENT FOR NOW WITH THE HIER POPS ACRS THE SRN COUNTIES CLOSER TO WHERE NAM/UKMET SHOW H85 WARM FNT. WENT NO HIER THAN CHC POPS FOR NOW GIVEN DRY GFS FCST...BUT LATER SHIFTS WL LIKELY HAVE TO RAISE POPS IF THE NAM/UKMET/CNDN MODELS MAINTAIN CONTINUITY. ALTHOUGH RESPONSIBLE SHRTWV FOR SAT NGT PCPN CHCS DRIFTS TO THE E ON SUN...SHRTWV NOW OVER BRITISH COLUMBIA FCST TO FOLLOW INTO THE UPR GRT LKS AND MAINTAIN UPR TROFFING AND SEMBLANCE OF CYC NE FLOW OVER THE UPR LKS. MAINTAINED CHC POPS INTO SUN NGT TO REFLECT PERSISTENCE OF THE TROFFING/CYC FLOW. THEN ENDED POPS FASTER W-E ON MON PER CNDN MODEL SHOWING DEPARTING UPR TROF TO TRANSITION TO GOING DRY FCST ON MON NGT. COORDINATED WITH GRB/DLH. && .AVIATION (FOR THE 12Z TAF ISSUANCE)... SFC TROUGH STRADDLING CNTRL UPR MI CONTINUES TO DRIFT SLOWLY EAST. RESULT IS LGT WEST WIND DEVELOPING AT BOTH TAF SITES AS TROUGH HAS MOVED THROUGH. THE GIVEN WIND DIRECTION FAVORS MAINTAINING FOG AT CMX BUT IS MORE OF A DOWNSLOPING WIND AT KSAW. OBSERVATIONS FM LAST COUPLE OF HOURS AT CMX/SAW HAVE FOLLOWED SUIT WITH VSBY IMPROVING AT SAW BUT STAYING 1/4SM AT CMX. LOCAL CLIMATOLOGY...WHICH DID OKAY WITH FOG TRENDS AT CMX OVERNIGHT...SUGGESTS LOW VSBY THROUGH 14Z THEN RAPID IMPROVEMENT INTO EARLY AFTN. AT SAW...NW/N WIND AND MOISTURE TO 5KFT PER 10Z TAMDAR SOUNDING SUPPORTS KEEPING IFR/MVFR CIGS IN THROUGH MUCH OF THE MORNING WITH SKIES SCATTERING OUT BY EARLY AFTN. AFTER VFR CONDITIONS THIS AFTN/EVENING...THE COMBINATION OF LIGHT WINDS...LINGERING LOW LEVEL MOISTURE...AND SFC BASED INVERSION COULD LEAD TO MORE FOG TONIGHT AT SAW. ATTM...THINK THERE IS ENOUGH OF AN UNFAVORABLE S WIND JUST OFF SFC TO PROHIBIT FOG AT CMX TONIGHT. && .MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)... EXPECT FOG TO PERSIST THROUGH MUCH OF THE DAY ON THE LAKE DUE TO LIGHT WINDS AND ABUNDANT LOW LEVEL MOISTURE. DRIER AIR PUSHING ACROSS THE LAKE TONIGHT SHOULD SCOUR OUT THE FOG...OR AT LEAST MAKE IT LESS WIDESPREAD. EAST TO NORTHEAST WINDS EXPECTED TO START THE WEEKEND AS LOW PRESSURE DEVELOPS IN THE PLAINS AND A HIGH PRESSURE RIDGE IS PRESENT OVER THE UPPER GREAT LAKES. NORTHEAST WINDS MAY REACH 25 KNOTS ON SUNDAY AS THE LOW PUSHES INTO THE CNTRL GREAT LAKES...THEN AGAIN MONDAY INTO TUESDAY...THIS TIME FROM THE NORTHWEST...AS THE LOW SLOWLY EXITS THE GREAT LAKES REGION. && .MQT WATCHES/WARNINGS/ADVISORIES...NONE. && $$ DISCUSSION...KC AVIATION...JLA MARINE...JLA
AREA FORECAST DISCUSSION...UPDATED
NWS MORRISTOWN TN
1005 AM EDT FRI JUL 18 2008 .DISCUSSION... ACARS SOUNDINGS AND MODEL FORECAST SOUNDINGS INDICATE A COUPLE INVERSIONS AND WARMING MIDLEVEL TEMPERATURES THAT WILL PREVENT ANY DEEP CONVECTION THIS AFTERNOON. TEMPERATURES AND DEWPOINTS ARE ON TRACK...SO NO UPDATE WILL BE NEEDED. && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DGS
AREA FORECAST DISCUSSION
NWS BROWNSVILLE TX
157 PM CDT SAT JUL 19 2008 .DISCUSSION... ... CONTINUE TO MONITOR STRONG TROPICAL WAVE IN THE CARIBBEAN ... IN THE SHORT TERM FOR TODAY ... A FEW SHOWERS ARE POSSIBLE OVER DEEP SOUTH TEXAS. MID LEVEL CLOUDS SHOW THE UPPER LEVEL LOW OVER SOUTH TEXAS WITH A BROAD CIRCULATION OVER THE WESTERN GULF. TEMPERATURES WILL CONTINUE VERY WARM INTO MONDAY. AN AIR FORCE RECONNAISSANCE AIRCRAFT IS CURRENTLY INVESTIGATING THE TROPICAL WAVE IN THE CARIBBEAN TO DETERMINE IF A CLOSED CIRCULATION HAS FORMED. SHOWERS AND THUNDERSTORMS CONTINUE TO FLARE ON THE SOUTH SIDE OF THE WAVE AT THE PRESENT TIME. UPDATED THE FORECAST TO TAKE INTO ACCOUNT THE NEW GFS GUIDANCE FROM NOW THROUGH TUESDAY. NO CHANGES WERE DONE TO THE PRECIPITATION GRIDS BEFORE TUESDAY. AFTER TUESDAY THE POPS WERE INCREASED BETWEEN 10-20 PERCENT OVER THE 06Z MODEL RUN TO ACCOUNT FOR THE POSSIBILITY OF HEAVY RAINS. AT THE PRESENT TIME HPC SHOWS A HEAVY RAIN EVENT FOR THE END OF THE FORECAST PERIOD. AS CONFIDENCE INCREASES...AND THE SYSTEM GETS CLOSER TO THE WESTERN GULF...IT IS LIKELY WE MAY SEE AROUND TWO INCHES AS INDICATED BY HPC. 12Z MODEL RUN SHOWS A SIMILAR FORECAST TO THE 06Z RUN...HOWEVER A SLIGHT SOUTHWARD MOVEMENT AFTER 96 HOURS IS OBSERVED SHOWING A BROAD AREA OF LOW PRESSURE OVER THE WESTERN GULF. BOTH MODEL RUNS TRACK THE FEATURE OVER THE NORTHERN TIP OF THE YUCATAN PENINSULA BEFORE IT ENTERS THE WESTERN GULF BY 96 HOURS. THE 12Z MODEL RUN MAY HINT...ALTHOUGH WITH A LOT OF UNCERTAINTY...THAT THE SHOWER ACTIVITY OVER DEEP SOUTH TEXAS WITH THE CURRENT FORECAST TRACK OF THIS SYSTEM MAY NOT END AFTER THE PASSAGE OF THE SYSTEM. AN UPPER LEVEL HIGH PRESSURE TO THE NORTH OVER NORTHERN TEXAS WITH E-NE WINDS ALOFT AND NE WINDS OVER THE GULF COULD ENHANCE THE SHOWER ACTIVITY OVER DEEP SOUTH TEXAS DUE TO DIFFLUENCE ALOFT. PLENTY OF TROPICAL MOISTURE WILL BE PRESENT OVER DEEP SOUTH TEXAS. GFS FORECAST SOUNDINGS INDICATE THAT PRECIPITABLE WATER WILL REACH 2.30 FOR THE MIDDLE OF THE WEEK BEGINNING TUESDAY AFTERNOON. THE FORECAST PRECIPITABLE WATER DOES NOT GET BELOW 2.00 INCHES UNTIL FRIDAY BUT THE ATMOSPHERE CONTINUES TO BE VERY MOIST. WILL CONTINUE TO MONITOR POSSIBLE TROPICAL DEVELOPMENT OVER THE WESTERN CARIBBEAN. PLEASE REFER TO THE NATIONAL HURRICANE CENTER LATER ON TODAY FOR FUTURE UPDATES WITH THIS CARIBBEAN WAVE ... CURRENTLY STILL ANALYZED AS A STRONG TROPICAL WAVE. && .MARINE...BUOY020 CURRENTLY REPORTS SEAS LESS THAN 2 FT WITH A SOUTH WIND AT 10 KTS. MTRPIL ALSO CHECKS IN WITH A S WIND AROUND 10 KTS. THE PGF WILL REMAIN PRETTY RELAXED OVER THE LOWER TX COASTLINE AS WEAK SURFACE RIDGING PERSISTS OVER THE GULF OF MEX THROUGH MON. THE STRONG TROPICAL WAVE IN THE WESTERN CARIB SEA WILL REMAIN A LARGE AREA OF CONCERN FOR THE LATER PORTIONS OF THE MARINE FORECAST AS IT CONTINUES TO MOVE WNW AT AROUND 15 MPH. OVERALL WINDS AND SEAS AFTER MON FOR THE LOWER TX COASTLINE WILL BE HIGHLY DEPENDENT ON THE OVERALL TRACK AND DEVELOPMENT OF THE TROPICAL WAVE AS IT MOVES OUT OVER THE SOUTHWESTERN GULF OF MEX. EVEN IF THIS THE DEVELOPMENT OF THIS FEATURE REMAINS LIMITED AS IT CROSSES THE SOUTHWESTERN GULF... INCREASED SWELL ACTIVITY WILL BE LIKELY ALONG THE LOWER TEXAS COASTLINE LATER IN THE CWF PERIOD DUE TO A STRONGER PGF. HAVE MADE SOME ADJUSTMENTS TO THE CWF SWELL WORDING TO HOLD THE LARGER SWELLS IN A LITTLE BIT LONGER NEXT WEEK. HAVE ALSO MADE SOME ADJUSTMENTS TO EXPECTED WINDS TO REFLECT A MORE E-NE SURFACE FLOW WITH THE APPROACH OF THE CARIB TROPICAL WAVE. ONCE AGAIN... THE OVERALL WIND FIELDS ON AND AFTER TUES MAY BE QUITE VARIABLE DEPENDING ON THE FINAL TRACK OF THE TROPICAL FEATURE. MARINERS ALONG THE LOWER TX COASTLINE SHOULD CONTINUE TO CLOSELY MONITOR THE LATEST NWS MARINE FORECASTS AND THE LATEST STATEMENTS AND OUTLOOKS FROM NHC CONCERNING THIS TROPICAL FEATURE. && .AVIATION...VSBL SATL IMAGERY SHOWS SOME LOW LEVEL CU DECKS BUILDING OVER THE BRO CWA AREA. THE KBRO REFLECTIVITY SHOWS NO CONV DEVELOPMENT THIS AFTERNOON DUE TO THE DRIER AND MORE STABLE NATURE OF THE ATMS OVER THE REGION. EXPECT OVERALL VFR CONDITIONS TO PREVAIL THROUGHOUT THE NIGHT INTO TOMORROW AROUND THE LOWER RGV AIRPORTS. && .PREV DISCUSSION... /ISSUED 933 AM CDT SAT JUL 19 2008/ DISCUSSION... .. A STRONG TROPICAL WAVE IN THE CARIBBEAN WILL BE MONITORED OVER THE NEXT FEW DAYS FOR POSSIBLE TROPICAL DEVELOPMENT ... THE WEATHER SYNOPSIS CONTINUES TO SHOW AN UPPER LEVEL LOW PRESSURE AREA LOCATED OVER THE NORTHWESTERN GULF WITH NO CLEAR AREAS OF UPPER LEVEL DIFLUENCE. OVER THE GULF OF MEXICO AND THE CARIBBEAN SEA THE FOLLOWING FEATURES ARE PRESENT. AN UPPER LEVEL LOW PRESSURE IS OVER CUBA LOCATED WEST OF A STRONG TROPICAL WAVE LOCATED AT 75W AND 21N WITH A 1009 MB SURFACE LOW ASSOCIATED WITH IT. BETWEEN THESE TWO UPPER LEVEL LOW PRESSURES AN UPPER LEVEL RIDGE IS PRESENT OVER THE CENTRAL GULF OF MEXICO. THE UPPER LEVEL LOW OVER CUBA IS PROVIDING 20-30 KTS OF SHEAR WITH THE WATER VAPOR SATELLITE SHOWING DRY AIR IN THE UPPER AND MID LEVELS OF THE ATMOSPHERE EXTENDING FROM NORTHERN FLORIDA TO SOUTHWESTERN CUBA. THE UPPER LEVEL LOW OVER THE NW GULF SHOWS A SHEAR OF 30 KTS. THE STRONG WAVE LOCATED AT 75W AND 21N IS FORECAST TO DRIFT WEST NORTHWEST. IT IS TOO EARLY TO KNOW WHAT TYPE OF DEVELOPMENT THIS WAVE WILL UNDERGO. THE SYSTEM HAS THE POTENTIAL TO DEVELOP INTO A TROPICAL DEPRESSION OVER THE NEXT DAY OR TWO AS IT MOVES TOWARD THE WEST NORTHWEST. THERE ARE SEVERAL FACTORS THAT COULD INTERACT WITH THIS WAVE AND POSSIBLE FUTURE DEVELOPMENT. THE DRY AIR AND SHEAR WEST OF IT COULD INHIBIT THE SYSTEM FROM DEVELOPING INTO A STRONG SYSTEM IN THE SHORT TERM. ALSO THE ENCOUNTER OF THE SYSTEM WITH THE NORTHERN THIRD OF THE YUCATAN PENINSULA WILL ALSO BE AN FACTOR FOR FUTURE DEVELOPMENT. THE MOST FAVORABLE AREA FOR DEVELOPMENT IS PRESENTLY IN THE SOUTHERN PORTION OF THE WAVE FURTHEST AWAY FROM THE DRY AIR AND WHERE SHEAR IS LOWER. THE STRENGTH AND LOCATION OF THE HIGH PRESSURE SYSTEM OVER THE GULF OF MEXICO BETWEEN CUBA AND THE NORTHWESTERN GULF WILL PLAY AN IMPORTANT FACTOR WITH THE MOVEMENT AND DEVELOPMENT OF THIS FEATURE BETWEEN NOW AND THE MIDDLE OF THIS COMING WEEK. ONCE THE FEATURE PASSES THE YUCATAN PENINSULA OR THE YUCATAN CHANNEL IT IS FORECAST TO MOVE TOWARD THE RIO GRANDE RIVER WITH THE ECMWF MODEL PLACING IT SOUTH OF THE RIO GRANDE RIVER AND THE GFS PLACING IT OVER DEEP SOUTH TEXAS. THERE IS A LOT OF UNCERTAINTY ON WHAT KIND OF SYSTEM WE COULD BE DEALING WITH. AT THE PRESENT TIME WE HAVE INCLUDED MORE THAN A 40 PERCENT OF SHOWERS AND THUNDERSTORMS AFTER TUESDAY. AS TIME GOES BY FUTURE MODEL RUNS WILL PROVIDE FURTHER INFORMATION. PLEASE REFER TO THE NATIONAL HURRICANE CENTER FOR FURTHER UPDATES ABOUT THIS TROPICAL FEATURE. THE GRIDS HAVE BEEN UPDATED TO REFLECT THE POSSIBLE INCREASE IN POPS FOR THIS COMING WEEK. IN THE SHORT TERM ONLY A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS IS EXPECTED FOR TODAY. && .PRELIMINARY POINT TEMPS/POPS... BAYVIEW/PORT ISABEL 92 78 92 76 / 10 10 10 0 BROWNSVILLE 94 77 93 76 / 10 10 10 0 HARLINGEN 95 75 95 74 / 10 10 10 0 MCALLEN 97 76 96 76 / 10 10 10 0 RIO GRANDE CITY 97 77 96 76 / 10 10 10 0 SOUTH PADRE ISLAND 89 79 88 79 / 10 10 10 0 && .BRO WATCHES/WARNINGS/ADVISORIES... TX...NONE. GM...NONE. && $$ THIS PRODUCT IS ALSO AVAILABLE ON THE WEB AT: HTTP://WWW.WEATHER.GOV/BROWNSVILLE 53/60
AREA FORECAST DISCUSSION...UPDATE
NWS MARQUETTE MI
125 AM EDT SUN JUL 20 2008 UPDATED FOR 06Z AVIATION DISCUSSION .SYNOPSIS... 20Z WATER VAPOR LOOP AND RUC 500MB HEIGHT ANALYSIS SHOWED NEARLY ZONAL FLOW ACROSS THE NORTHERN U.S.. WITHIN THE FLOW THERE ARE A FEW FEATURES OF INTEREST. TWO SHRTWVS ARE APPARENT OVER MN...ONE IN NW AND ANOTHER IN THE CENTRAL PORTION OF THE STATE. THE CENTRAL ONE APPEARS MORE FORMIDABLE...AS NOTED BY A DRIER DRY SLOT IN ITS WAKE. DPVA FROM THESE TWO SHRTWVS...COMBINED WITH RIGHT ENTRANCE REGION FORCING FROM A 60-80KT JET IN FAR WRN ONTARIO IS AIDING IN SHOWERS ACROSS NRN AND EAST CENTRAL MN. A FEW STORMS HAVE ALSO POPPED UP IN EAST CENTRAL MN WITH DAYTIME HEATING. A BREAK IN THE PCPN EXISTS OVER MUCH OF NORTH DAKOTA...EXCEPT IN THE NW PORTION OF THE STATE INTO ERN SASKATCHEWAN WHERE DPVA AHEAD OF A SHRTWV TROUGH/UPPER LOW IS SUPPORTING PCPN THERE. BACK CLOSER TO HOME...A SURFACE HIGH PRESSURE AREA IS OVER NRN ONTARIO. ALTHOUGH THE LOCATION IS USUALLY FAVORABLE FOR DRY AIR ADVECTION...DEWPOINTS STILL AT LEAST REMAIN IN THE 50S. 60S DEWPOINTS CAN BE SEEN OVER WRN/SRN WI AND CENTRAL/SRN MN...WHICH IS WHERE A WARM FRONTAL BOUNDARY EXISTS. DUE TO THE HIGH LOW LEVEL MOISTURE...PLENTY OF DIURNAL CUMULUS HAS DEVELOPED. A CAP SEEN AT 775MB ON THE 18Z TAMDAR SOUNDING FROM SAW IS HELPING TO PREVENT ANY CUMULUS FROM GROWING INTO SHOWERS...DESPITE LOW LEVEL CONVERGENCE FROM LAKE BREEZES. WITH THE 50S DEWPOINTS AROUND...FOG AND STRATUS THAT DEVELOPED ON LAKE SUPERIOR A FEW DAYS AGO HAS GONE NOWHERE...SINCE THE DEWPOINTS ARE AT LEAST 10 DEGREES F HIGHER THAN THE BUOY WATER TEMPS. DAYTIME MIXING HAS HELD THE FOG/STRATUS TO THE NEARSHORE AREAS THIS AFTN. && .SHORT TERM (TONIGHT AND SUNDAY)... 12Z NAM/REGIONAL CANADIAN APPEAR TO HAVE THE BEST HANDLE ON THE TWO SHRTWVS OVER MN...IN ADDITION TO THE CURRENT PCPN FALLING...AND THEREFORE THE FORECAST FOR THE SHORT TERM LEANS TOWARD THERE SOLUTIONS. DID NOT USE THE 12Z GFS/ECMWF DUE TO CONVECTIVE FEEDBACK...WHILE THE UKMET SEEMED WAY TOO WEAK WITH THE SHRTWVS. OUR 12Z LOCAL WRF-ARW RUN DID NOT HAVE A GOOD HANDLE ON THE PCPN...BUT THE NEW 18Z RUN APPEARS TO BE DOING BETTER...IN FACT LOOKING SIMILAR TO THE NAM. THE TWO SHRTWVS MOVE ACROSS THE CWA BY 06Z...BRINGING THE PCPN OVER AT LEAST NRN MN ACROSS. PCPN SHOULD MOVE INTO THE WESTERN U.P....AIDED BY PERSISTENT DPVA AND RIGHT ENTRANCE REGION FORCING. HOWEVER...THE PCPN WILL LIKELY WEAKEN AS IT SPREADS INTO THE CENTRAL SECTIONS WHERE DRIER AIR IS PRESENT (SAW TAMDAR SOUNDING HAD NEARLY A 40C DEWPOINT DEPRESSION AT 650MB). FOCUS THEN SHIFTS BACK TO THE SW WITH CONVECTION DEVELOPING JUST TO THE NORTH OF THE TWIN CITIES. ALL MODELS...EVEN THOSE WITH CONVECTIVE FEEDBACK...SEEM TO SUGGEST AN MCS DEVELOPING OUT OF THIS CONVECTION. THE TRACK OF THIS MCS WOULD BRING IT ACROSS NE WI...PERHAPS SRN UPPER MI AND INTO NRN LOWER MI. HAVE RAISED POPS IN THE SRN U.P. TO LIKELY WITH THAT AREA BEING ON THE NORTH SIDE OF THE MCS. ADDED SOME THUNDER IN THE FORECAST GIVEN UPSTREAM LIGHTNING. THIS PCPN SHOULD EXIT OUT OF THE CWA EARLY SUN MORNING. ONLY SLIGHT ADJUSTMENTS MADE TO LOW TEMPS...WHICH GENERALLY SEEM REASONABLE. HARD TO SAY WHAT IS GOING TO OCCUR ON SUN. THE SHRTWV TROUGH/UPPER LOW IN ALBERTA/SASKATCHEWAN IS PROGGED TO BE MOVING ACROSS CENTRAL CANADA AT THIS TIME. THE LEAD SHRTWV AIDING IN THE PCPN IN SE SASKATCHEWAN LOOKS TO MOVE INTO THE CWA DURING THE AFTN...WHICH WITH SOME LAKE BREEZES EXPECTED MEANS SOME SHOWERS AND POSSIBLY A COUPLE OF THUNDERSTORMS SHOULD DEVELOP. THEREFORE...HIGHEST POPS ARE CONFINED TO THE AFTN...AND THE STRONGEST AREA OF CONVERGENCE WHICH IS LOCATED IN THE EASTERN U.P.. PLENTY OF CLOUDS...ALONG WITH ONSHORE WINDS...MAY MAKE IT DIFFICULT FOR LAKESHORE LOCATIONS TO RISE MUCH. THEREFORE...HAVE COOLED READINGS NEAR THE SHORE. INLAND TEMPS SEEMED REASONABLE...WHERE AT LEAST SOME PARTIAL SUNSHINE SHOULD OCCUR. REGARDING THE FOG/STRATUS ON LAKE SUPERIOR...WITH THE LACK OF ANY SIGNIFICANT DRY AIR AROUND...THE FOG/STRATUS WILL MOVE AROUND THE LAKE BASED ON THE LOW LEVEL WIND DIRECTION. FOLLOWED GENERALLY THE 950MB RH/WIND FIELDS FROM NAM AND LOCAL WRF-ARW RUN WHICH SEEM TO HAVE A GOOD HANDLE ON THE FOG/STRATUS. BASICALLY...LOW LEVEL WIND FIELDS DO NOT CHANGE MUCH...SO ONCE DIURNAL COOLING SETS IN...SOME FOG SHOULD REDEVELOP ON THE KEWEENAW. SOME FOG COULD REDEVELOP TOO IN THE EASTERN U.P....AIDED BY THE MOIST ONSHORE FLOW OFF LAKE SUPERIOR AND ANY RADIATIONAL COOLING THAT CAN OCCUR THERE. EVENING/MIDNIGHT SHIFTS WILL NEED TO MONITOR POSSIBILITY OF DENSE FOG ON THE KEWEENAW. FOG ON LAND WILL DISSIPATE BY NOON AS DAYTIME HEATING HELPS MIX IT OUT. && .LONG TERM (SUN NIGHT THROUGH NEXT SAT)... NAM SHOWING A 500 MB TROUGH IN THE UPPER GREAT LAKES 00Z MON AND THIS DIGS SE MON AND REMAINS INTO TUE WITH THE TROUGH AXIS EAST OF THE AREA BY THEN. NAM BRINGS IN SOME 850-500 MB Q-VECTOR CONVERGENCE WITH SOME MOISTURE SUN NIGHT AND MON. GFS KEEPS IT DRY WITH PCPN STAYING TO THE SOUTH AND WEST. OTHER MODELS INCLUDING THE ECMWF GO MORE TOWARDS THE NAM AND KEEP PCPN IN FOR SUN NIGHT AND MON...SO KEPT IN LOW CHANCE POPS FOR SUN NIGHT AND MON MORNING AND THEN SLIGHT CHANCE POPS IN THE AFTERNOON. OVERALL...DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST FOR WEATHER OR FOR TEMPERATURES. IN THE EXTENDED...FOLLOWED CLOSE TO 00Z ECMWF FOR THIS FORECAST WHICH SHOWS AN UPPER LEVEL 500 MB RIDGE IN CONTROL FOR MOST OF THE PERIOD. THERE IS A SHORTWAVE THAT MOVES THROUGH THE RIDGE AND MOVES ACROSS SOUTHERN ONTARIO AND MANITOBA THU NIGHT THROUGH FRI NIGHT AND PUT IN CHANCE POPS AS A DIEING COLD FRONT MOVES THROUGH THE AREA. OTHERWISE...IT WILL BE DRY WITH TEMPERATURES NEAR NORMAL. DID NOT MAKE TOO MANY CHANGES TO THE GOING FORECAST. && .AVIATION (FOR THE 06Z TAF ISSUANCE)... FOG/STRATUS AGAIN IS THE MAIN CONCERN FOR THE TAFS AS FOG PRESISTS OVER LAKE SUPERIOR. WITH EASTERLY UPSLOPE WINDS EXPECTED AT KCMX LOOK FOR LIFR CONDITIONS TO PERSIST INTO SUN MORNING. A LIGHT NE WIND HAS ALSO BROUGHT IFR TO LIFR CONDITIONS INTO KSAW THIS EVENING AND I EXPECT THESE TO PERSIST THROUGH MUCH OF THE NIGHT. AT BOTH SITES...CIGS/VSBYS SHOULD IMPROVE SUN MORNING AS DAYTIME HEATING GRADUALLY LIFTS THE BASES OF THE LOW CLOUDS AND FOG MIXES OUT. LIGHT RAIN ASSOC WITH AN UPR DISTURBANCE HAS GENERALLY DISSIPATED OVER THE WRN HALF OF UPR MI THIS EVENING DUE TO DRY AIR IN PLACE OVER THE REGION. KEPT A TEMPO GROUP FOR LIGHT RAIN OVER KCMX FOR THE EARLY OVERNIGHT BUT OTHERWISE EXPECT DRY CONDITIONS. LOOK FOR SOME POSSIBLE SHRA DEVELOPMENT AT KSAW SUN AFTERNOON AS ANOTHER DISTURBANCE APPROACHES FROM THE WEST. && .MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)... LACK OF DRY AIR AROUND LAKE SUPERIOR MEANS FOG WILL HANG AROUND FOR AWHILE...SHIFTING AROUND THE LAKE BASED ON WIND DIRECTION. HAVE EXTENDED MOST DENSE FOG ADVISORIES THROUGH SUNDAY...BUT MAY HAVE TO BE EXTENDED INTO MONDAY AS WELL...DEPENDING ON TIMING OF WHEN DRIER AIR CAN COME SOUTH OUT OF NORTHERN ONTARIO. ALTHOUGH FOG IS PROBLEMATIC...GENERAL LIGHT PRESSURE GRADIENT EXPECTED ACROSS LAKE SUPERIOR THROUGH THE FORECAST MEANS WIND SPEEDS SHOULD STAY AT 20 KT OR LESS. STRONGEST WINDS EXPECTED TONIGHT INTO TOMORROW OVER FAR WESTERN LAKE SUPERIOR...DUE TO FUNNELING NE FLOW BTWN HIGH PRESSURE IN NORTHERN ONTARIO AND LOW PRESSURE CROSSING WI. && .MQT WATCHES/WARNINGS/ADVISORIES... UPPER MICHIGAN...NONE. LAKE SUPERIOR... DENSE FOG ADVISORY UNTIL 8 PM EDT /7 PM CDT/ TODAY FOR LSZ162- 243>250-263>266. LAKE MICHIGAN...NONE. && $$ SYNOPSIS/SHORT TERM...AJ LONG TERM...GJM AVIATION...VOSS MARINE...AJ
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
346 AM CDT SUN JUL 20 2008 .DISCUSSION... TSTM CHANCES AND TEMPERATURES WILL CONTINUE TO BE THE MAIN CONCERNS FOR THE NEXT FEW DAYS. 00Z UPPER AIR CHARTS SHOWED THE FOLLOWING... A DECENT AMOUNT OF MOISTURE WAS IN PLACE AT 850 MB WITH DEWPOINTS IN THE TEENS C FROM WRN KS INTO NE AND IA. AT 700 MB...TEMPERATURES WERE QUITE WARM FROM NE WESTWARD. THE 10 DEGREE C ISOTHERM WAS LOCATED FROM SRN SD INTO CNTRL IA. STORMS LAST EVENING AND EARLY THIS MORNING HAD A HARD TIME DEVELOPING ANY FARTHER SOUTH THAN THE 11 C LINE AT 700 MB IN OUR AREA. AT 500 MB...TEMPERATURES WERE ALSO QUITE WARM...GENERALLY -5 TO -7 C. THERE WAS A THERMAL TROUGH FROM SASK INTO NERN MT. AT 300 MB...STRONGEST WINDS WERE NOTED FROM OR AND ID ACROSS SRN MT/NRN WY...THROUGH SD AND SRN MN. A JET SEGMENT OF 80 KTS WAS REPORTED BY AIRCRAFT ALONG THE MT/WY BORDER. THIS MAY COME INTO PLAY LATER TODAY. WATER VAPOR LOOP SHOWED FAIRLY DRY AIR IN PLACE IN THE MID LEVELS ACROSS OUR AREA...WITH LOTS OF MONSOONAL MOISTURE FROM MEXICO INTO THE SRN AND CNTRL ROCKIES. PRECIPITABLE WATER VALUES OF 1.50 OR MORE WERE NOTED FROM ERN TX...LA AND MS NWD INTO ERN NE...IA AND SRN MN. 08Z SURFACE ANALYSIS SHOWED A WEAK FRONTAL BOUNDARY FROM NERN IA INTO SWRN IA...ACROSS SRN NE AND INTO LOW PRESSURE OVER SERN WY. MODELS ARE HAVING A HARD TIME WITH THIS PATTERN...BUT THE 00Z NAM SEEMED SOMEWHAT REASONABLE. WEAK SURFACE BOUNDARY OVER OUR AREA WILL TRY TO LIFT NWD TODAY. MAIN FOCUS FOR TSTM ACTIVITY SHOULD BE NORTH OF THE FRONT...WHERE MID LEVEL TEMPERATURES ARE A LITTLE COOLER. THIS IS ALSO WHERE THE CHANCE OF SEVERE STORMS IS THE HIGHEST... WITH BULK SHEAR OF 30 KTS OR MORE. MIXED LAYER CAPE VALUES FROM THE 06Z NAM ALSO REACH 3000-4500 J/KG IN THAT AREA. HAVE HIGHS TODAY RANGING FROM THE LOWER 90S NORTH TO THE UPPER 90S SOUTH. MODELS SHOW UPPER LEVEL JET STREAK MOVING INTO MN AND WI BY LATE THIS AFTN/EVENING...PUTTING PARTS OF NE AND IA IN THE RIGHT ENTRANCE REGION FOR TONIGHT. STORMS MAY HAVE A TENDENCY TO DEVELOP SWD DURING THE NIGHT. KEPT BEST CHANCE OF TSTMS ACROSS THE NORTH... WITH POPS RANGING TO 14 OR LESS ALONG THE KS BORDER. LOWS WILL BE IN THE UPPER 60S NORTH TO LOWER 70S SOUTH. FARTHER OUT...DID NOT MAKE MANY CHANGES. WE GENERALLY REMAIN IN NW FLOW ALOFT EARLY IN THE WEEK WITH RIDGE AXIS TO OUR WEST. TROUGHS WILL BE IN PLACE OVER THE WRN U.S. AND OVER THE ERN STATES. FLOW DOES TEND TO FLATTEN LATER IN THE WEEK...BUT THEN THE GFS BUILDS A STRONG 500 MB RIDGE BY THE WEEKEND. THE ECMWF IS SIMILAR. THAT PATTERN WOULD TEND TO BE HOT AND MAINLY DRY FOR OUR AREA...WITH LOWS AROUND 70 AND HIGHS 90 TO 95. && .AVIATION... FOR TAF SITES KOMA/KLNK/KOFK WEAK SURFACE BOUNDARY EXPECTED TO REMAIN ACROSS THE AREA TODAY WITH POTENTIAL FOR THUNDERSTORMS AGAIN MAINLY AFTER 20Z. UNCERTAINTY IN TIMING AND LOCATION OF DEVELOPMENT PRECLUDES MENTION AT THIS TIME. OTHERWISE...VFR CONDITIONS THROUGH MOST OF THE PERIOD. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ DISCUSSION...MILLER AVIATION...FOBERT
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
509 AM PDT SUN JUL 20 2008 .SHORT TERM (TODAY AND MONDAY)...MIDDLE LEVEL MOISTURE IS ARRIVING OVER THE AREA THIS MORNING...MAKING FOR A DIFFICULT FORECAST ESPECIALLY FOR MARINE LAYER. SATELLITE AND RADAR IMAGERY ARE BEING WATCHED CLOSELY THIS MORNING FOR POSSIBLE DEVELOPMENT...BUT SO FAR IT APPEARS JUST MIDDLE AND LEVEL HIGH CLOUDINESS. DESPITE THE MARINE LAYER BEING SO DEEP THIS MORNING PUSHING INTO THE SANTA CLARITA VALLEY AND LOWER COASTAL SLOPES THIS MORNING...SOME CONCERN EXISTS THAT MOISTURE COULD SPILL OVER INTO THE LOS ANGELES COUNTY COASTS AND VALLEYS THIS AFTERNOON...BRINGING A POSSIBILITY OF CONVECTIVE STORMS. NAM 600 MB AND 700 MB RELATIVE HUMIDITIES ARE RATHER AGGRESSIVE WITH THE MOISTURE...AND 850-700 MB RELATIVE HUMIDITY AND WIND INDICATES A TRAJECTORY FOR THE LOS ANGELES AND VENTURA COUNTY COASTS AND VALLEYS. HOWEVER...NAM-WRF LIFTED INDICES AND 700 MB OMEGA INDICATE STABLE AIR IN PLACE. THIS WOULD KEEP CONVECTION IF IT DEVELOPS OVER THE MOUNTAINS AND DESERTS THIS AFTERNOON AND EVENING. WITH GFS AND OTHER MODELS LACKING AGREEMENT WITH NAM- WRF...FOR NOW...MONITORING SATELLITE AND RADAR DEVELOPMENT APPEARS TO BE APPROACH. MARINE LAYER CLOUDINESS COULD BE DIFFICULT TO CLEAR AGAIN...BUT A LITTLE EARLIER CLEARING SHOULD OCCUR. LATEST ACARS SOUNDING FROM KLAX INDICATE MARINE LAYER DEPTH AROUND 1600 FEET WITH NOT QUITE AS STRONG OF AN INVERSION OVER THE AREA AS THIS TIME LAST NIGHT. CLEARING COULD DEFINITELY OCCUR EARLIER IF MID-LEVEL MOISTURE BECOMES INVOLVED IN THE SCENARIO. DISAGREEMENT IN MONSOONAL MOISTURE STILL OCCURS INTO MONDAY AS GFS IS MORE PROGRESSIVE WITH THE TROUGH OFF THE COAST...AND THUS IS MORE QUICK IN EJECTING OUT THE MOISTURE AND BRINGING A DRYING TREND. NAM-WRF IS STILL QUITE AGGRESSIVE IN KEEPING MOISTURE OVER THE AREA FOR MONDAY AFTERNOON. NAM-WRF STILL KEEPS ABUNDANT MOISTURE IN PLACE WITH 850 MB DEWPOINTS AROUND 15 DEGREES CELSIUS...AND 850-700 MB DEWPOINTS AROUND 13 DEGREES CELSIUS. SLIGHT CHANCE POPS REMAIN FOR MONDAY...BUT DRYING TREND SHOULD BE EXPECTED FOR MIDWEEK. .LONG TERM (TUESDAY-SATURDAY)...GOOD AGREEMENT EXISTS BEYOND TUESDAY IN THE PACKAGE AT THE CURRENT TIME. WARMING TREND WILL START TO TAKE PLACE FOR MIDWEEK...WITH 850 MB TEMPERATURES AND 1000-500 MB THICKNESSES INCREASING. WARMING TREND WILL PERSIST INTO WEDNESDAY AND THURSDAY...WITH GOOD AGREEMENT BETWEEN THE GFS AND ECMWF. WARMING TREND SHOULD TOP OUT ON THURSDAY WHEN THICKNESSES ARE DEEPEST AND 850 MB TEMPERATURES TOP OUT. BUT...THINGS SHOULD START CHANGING FOR NEXT WEEKEND. GFS AND ECMWF BOTH INCREASE MOISTURE AGAIN OVER THE AREA FROM FRIDAY THROUGH THE WEEKEND. ECMWF AND GFS INDICATE MONSOONAL MOISTURE SURGING BACK INTO THE AREA FOR THE WEEKEND WITH 850 MB MIXING RATIOS NEARING 10 G/KG OVER THE AREA. && .AVIATION...20/1200Z. MARINE LAYER DEPTH CURRENTLY AROUND 1800 FT AND EXPECTED TO KEEP DEEPENING AS THE MORNING PROGRESSES...WITH SOLID COVERAGE INTO ALL LA AND VTU VALLEYS AND COASTAL SLOPES. N OF POINT CONCEPTION... BURNOFF EXPECTED BY 18Z...WITH A SIMILAR RETURN OF IFR CIGS AND VSBYS EXPECTED TONIGHT. LOW IFR CONDS ARE FLIRTING WITH KPRB RIGHT NOW...AND MODERATE CONFIDENCE THAT THEY WILL REACH THE AIRFIELD BEFORE SUNRISE. S OF POINT CONCEPTION...BURNOFF SEEMS TRICKY AND HAVE MODERATE CONFIDENCE THAT IFR CONDS WILL LINGER THROUGH MOST OF THE AFTERNOON AT COASTAL SITES. TSTMS ARE POSSIBLE DURING THE LATE AFTERNOON HOURS IN THE VICINITY OF KPMD AND KWJF...WHICH IS ALREADY REFLECTED IN CURRENT TAF PACKAGE. SLIGHT CHANCE OF TSTMS MEANDERING INTO THE LA VALLEYS...BUT CONFIDENCE IS TOO LOW TO PUT IN KBUR AND KVNY TAFS. KLAX...LOW CONFIDENCE IN CURRENT PACKAGE. UNSURE OF BURNOFF IF AT ALL THIS AFTERNOON. KBUR...MODERATE CONFIDENCE IN CURRENT PACKAGE. BURNOFF EXPECTED BY 18Z. SLIGHT CHANCE OF SHOWER DRIFTING OFF OF MTNS INTO THE AREA. LOW CONFIDENCE IN RETURN OF MARINE LAYER TONIGHT. && .LOX WATCHES/WARNINGS/ADVISORIES... HIGH RIP CURRENT RISK (SEE LAXSRFLOX). COASTAL FLOOD STATEMENT (SEE LAXCFWLOX). && $$ PUBLIC...HALL AVIATION...MEIER WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
335 AM PDT SUN JUL 20 2008 .SYNOPSIS... A SURGE OF MONSOONAL MOISTURE FROM THE SOUTHEAST WILL BRING HIGHER HUMIDITIES AND COOLER DAYTIME TEMPERATURES TO INLAND AREAS THROUGH MONDAY ALONG WITH A CHANCE OF MAINLY AFTERNOON AND EVENING SHOWERS AND THUNDERSTORMS. MODEST DRYING WILL DECREASE THUNDERSTORM CHANCES MIDWEEK WITH INCREASING CHANCES LATE IN THE WEEK AS ANOTHER INFLUX OF MOISTURE ARRIVES FROM THE SOUTHEAST. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... .SHORT TERM (TODAY THROUGH TUESDAY)... WEAK CYCLONIC CIRCULATION CENTER OFF THE NORTHERN BAJA COAST WILL HELP TO DRAW INCREASING AMOUNTS OF MONSOONAL MOISTURE INTO SOUTHWEST CALIFORNIA TODAY WITH THE MOISTURE CENTERED AROUND 700 MB. SURFACE DEWPOINTS IN THE COACHELLA VALLEY HAVE INCREASE INTO THE LOWER 70S AND INTO THE MID 70S IN PORTIONS OF IMPERIAL COUNTY. SOUTHWEST CALIFORNIA MAY BE CLOSE ENOUGH TO THE FRINGES OF THE MORE SUBSTANTIAL MOISTURE TO THE EAST AND WITHOUT TOO MUCH HIGHER LEVEL MOISTURE THAT WOULD INHIBIT DAYTIME HEATING AND INSTABILITY TO ALLOW FOR THUNDERSTORMS WITH A GREATER POTENTIAL FOR FLASH FLOODING TO DEVELOP IN THE MOUNTAINS AND DESERTS FROM LATE MORNING THROUGH EARLY EVENING TODAY. TOO MUCH MOISTURE OR MOISTURE WITH A LESS OPTIMAL VERTICAL DISTRIBUTION WOULD REDUCE FLOODING POTENTIAL FROM THUNDERSTORMS WITH SCATTERED SHOWERS AND SMALLER ISOLATED THUNDERSTORMS INSTEAD. GIVEN THE LEVEL OF CERTAINTY AND THE POTENTIAL FOR FLOOD PRODUCING THUNDERSTORMS...THE CURRENT FLASH FLOOD WATCH FOR THE MOUNTAINS AND DESERTS FOR LATE MORNING THROUGH MID EVENING TODAY LOOKS FINE. THERE IS ENOUGH EASTERLY COMPONENT TO THE STEERING LEVEL FLOW...MAINLY FROM THE SOUTH SOUTHEAST...FOR A FEW THUNDERSTORMS TO DRIFT INTO THE INLAND VALLEYS...MAINLY PORTIONS OF THE INLAND EMPIRE. FOR MONDAY...SOME DRYING BEGINS TO OCCUR LATE IN THE DAY AS THE NORTHERN BAJA CIRCULATION MOVES INLAND TO THE NORTHEAST AND DRYING SOUTH SOUTHWEST TO SOUTHWEST LOWER AND MID LEVEL FLOW BEGINS TO DEVELOP. THIS SHOULD KEEP AFTERNOON AND EVENING THUNDERSTORMS CONFINED TO THE MOUNTAINS AND DESERTS WITH GREATEST CHANCES IN THE SAN BERNARDINO COUNTY MOUNTAIN AND DESERT AREAS. DRYING WILL CONTINUE INTO TUESDAY WITH ONLY MINIMAL CHANCES FOR AFTERNOON THUNDERSTORMS...MAINLY IN THE SAN BERNARDINO COUNTY MOUNTAIN AND DESERT AREAS. INLAND AREAS WILL BE COOLER TODAY...THEN WILL SLOWLY WARM MONDAY AND TUESDAY AS DRYING OCCURS. A RECENT ACARS SOUNDING FROM LAX SHOWS THE BASE OF THE MARINE LAYER AROUND 2000 FEET WITH AN EXTENSIVE COASTAL STRATUS FIELD EXTENDING INLAND INTO THE LOWER COASTAL VALLEYS. MONSOONAL MOISTURE HAS NOT YET SPREAD FAR ENOUGH WEST TO HAVE MUCH IMPACT ON THE MARINE LAYER. MODELS SHOW THE MONSOONAL MOISTURE NOT GETTING MUCH FARTHER WEST THAN THE MOUNTAINS AND DESERTS. THIS MAY RESULT IN LESS DISRUPTION TO THE MARINE LAYER THAN PREVIOUSLY THOUGHT. THE GREATER DEPTH OF THE MARINE LAYER AND GREATER INITIAL INLAND EXTENT OF THE STRATUS MAY RESULT IN ANOTHER DAY OF SLOWER CLEARING FOR SAN DIEGO COUNTY COASTAL AREAS. && .LONG TERM (WEDNESDAY THROUGH SATURDAY)... SLOW DRYING WILL CONTINUE INTO WEDNESDAY...THEN INCREASING MOISTURE IN SOUTHEAST FLOW ALOFT WILL BRING INCREASING CHANCES FOR AFTERNOON AND EVENING THUNDERSTORMS IN THE MOUNTAINS AND DESERTS LATE IN THE WEEK. && .AVIATION... 200800Z...MARINE LAYER ABOUT 2300 FT IN THE SOUTH TO 1800 FT IN THE NORTH. BASES ABOUT 1800 FT MSL IN THE SOUTH TO AROUND 1400 FT MSL IN THE NORTH. LOCAL VSBY 3-5SM WITH ISOLATED BELOW 3SM IN THE MORNING. COASTAL EDDY FORECAST TO CONTINUE TODAY AND THEN WEAKEN OR DISSIPATE TONIGHT. EXPECT STRATUS TO CLEAR TO THE COAST BY 18-19Z. STRATUS EXPECTED TO RETURN BY LATE AFTERNOON AND EVENING BUT CLEAR EARLIER MONDAY AND WITH LESS COVERAGE MONDAY NIGHT. SOME BROKEN STATUS THIS AFTERNOON ALONG THE COAST WITH BETTER CLEARING MONDAY. INCREASING SUBTROPICAL MOISTURE WITH LOTS OF MID AND HIGH CLOUDS OVER THE AREA TODAY. SCATTERED SHOWERS AND THUNDERSTORMS ARE FORECAST TO DEVELOP OVER THE MOUNTAINS AND DESERTS THIS AFTERNOON THROUGH EVENING WITH THUNDERSTORMS POSSIBLE IN THE INLAND VALLEYS. SOME SHOWERS AND THUNDERSTORMS POSSIBLE IN THE MOUNTAINS AND DESERTS EARLY THIS MORNING. BASES AROUND 8K FT TO 35-40K. THUNDERSTORMS MAY HAVE HEAVY RAIN...HAIL AND STRONG GUSTY WINDS. CHANCES FOR SHOWERS AND THUNDERSTORMS DECREASING MONDAY. && .MARINE... 200800Z...A MODERATE SOUTH SWELL WILL CONTINUE THROUGH MONDAY NIGHT. A PERIOD OF 16 SECONDS TODAY WILL DROP TO 14 SECONDS BY MONDAY AFTERNOON. THE SURF IS NOT EXPECTED TO BE AS HIGH AS PREVIOUSLY EXPECTED...WITH THE LARGEST SURF IN ORANGE COUNTY UP TO 6 FEET AND UP TO 4 TO 5 FEET IN SAN DIEGO COUNTY. THERE WILL BE A HIGH RIP CURRENT RISK FOR THE NEXT FEW DAYS. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...FLASH FLOOD WATCH FROM 11 AM PDT THIS MORNING THROUGH THIS EVENING FOR APPLE AND LUCERNE VALLEYS-COACHELLA VALLEY- RIVERSIDE COUNTY MOUNTAINS-SAN BERNARDINO COUNTY MOUNTAINS- SAN DIEGO COUNTY DESERTS-SAN DIEGO COUNTY MOUNTAINS. PZ...NONE. && $$ PUBLIC...MARTIN AVIATION/MARINE...WHITLOW NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
648 AM CDT SUN JUL 20 2008 .DISCUSSION... 415 AM CDT MAIN FOCUS REMAINS ON CONVECTIVE TRENDS NEXT 24-48 HOURS. MCS HAS MOVED THROUGH CWA EARLY THIS MORNING...WITH REMNANT MCV NOW OVER SOUTHERN LAKE MICHIGAN. THIS FEATURE TO CONTINUE TO PROPAGATE TO THE EAST THIS MORNING...WHILE LOW LEVEL OUTFLOW HAS SPREAD INTO CENTRAL IL AND NORTHERN IND AND LIKELY WILL BE EFFECTIVE FRONTAL BOUNDARY. REGIONAL WIND PROFILERS DEPICT 25 KNOT WESTERLY LOW LEVEL JET ORIENTED ACROSS SOUTHERN IA/NORTHERN MO INTO IL...THOUGH ADDITIONAL ELEVATED DEVELOPMENT HAS BEEN WEAK AND CONTAINED TO WESTERN/CENTRAL IA WHERE RUC MESOANALYSIS FIELDS INDICATE MUCAPE AXIS. PROFILER/RUC/WATER VAPOR COMBO DEPICTS MINOR AMPLITUDE SHORT WAVE TRANSLATING ACROSS IA/MN WHICH WILL MOVE EAST TODAY...THOUGH CURRENT THINKING IS THAT MORNING HOURS SHOULD BE FAIRLY TRANQUIL ACROSS FORECAST AREA GIVEN STABILIZED BOUNDARY LAYER IN WAKE OF OVERNIGHT CONVECTION. TRENDS INTO THIS AFTERNOON SOMEWHAT MUDDLED...THOUGH SUSPECT OUTFLOW BOUNDARY WILL MIX BACK NORTHWARD TOWARD SOUTHERN PORTIONS OF CWA AS BOUNDARY LAYER MIXES...AND WEAK SURFACE PRESSURE FALLS DEVELOP ACROSS THE PLAINS IN RESPONSE TO MORE VIGOROUS MID LEVEL WAVE DIGGING ACROSS THE NORTHERN CONUS. RUC/NAM FORECAST SOUNDINGS INDICATE FAIRLY UNSTABLE CONDITIONS BY AFTERNOON WITH SBCAPES OF 1300-1500 J/KG AND LITTLE/NO CIN. DIFFUSE PRESSURE GRADIENT AND WEAK LOW LEVEL WIND FIELD SUGGEST LOW CONFIDENCE IN DETAILING THUNDERSTORM LOCATION AT THIS TIME...THOUGH HAVE GENERALLY GONE WITH SLIGHT CHANCE ACROSS NORTH AND A LITTLE HIGHER CHANCE POP ACROSS SOUTHERN COUNTIES WHICH WILL BE IN CLOSER PROXIMITY TO RETREATING OUTFLOW BOUNDARY. THUNDERSTORM PROBABILITIES APPEAR TO INCREASE TONIGHT...AS UPPER MIDWEST TROUGH CONTINUES TO DIG SOUTHEAST AND 25-30 KNOT SOUTHWEST LOW LEVEL JET DEVELOPS LIFT ACROSS LOW LEVEL BOUNDARY. GUIDANCE IN RELATIVELY DECENT AGREEMENT IN DEPICTING PRECIPITATION DEVELOPING ACROSS SOUTHERN IOWA AND SPREADING EAST/SOUTHEAST INTO NORTHERN/CENTRAL ILLINOIS OVERNIGHT WITH MAIN FOCUS ACROSS SOUTH/SOUTHWESTERN HALF OF CWA. POTENTIAL FOR LOCALLY HEAVY RAINFALL AMOUNTS EXIST WITH NAM/GFS BOTH DEPICTING PRECIPITABLE WATER AMOUNTS AROUND 2 INCHES. WHILE NORTHWEST/NORTH CENTRAL IL HAVE RECEIVED SOME HEAVY RAIN OVER PAST FEW DAYS...EXPECTED PRECIP AXIS A LITTLE FARTHER TO THE SOUTH. MODEL TRENDS AND THUNDERSTORM DEVELOPMENT TO OUR WEST LATER TODAY WILL HAVE TO BE MONITORED FOR FURTHER DETAIL OF WHERE HEAVIEST RAIN WILL LINE UP... WITH SOME CONCERN FOR NEED OF A FLOOD WATCH HEADLINE TONIGHT. AREA ALSO INCLUDED IN SPC DAY 1 OUTLOOK FOR SEVERE MCS POTENTIAL TONIGHT. THUNDERSTORMS EXPECTED TO LINGER INTO MONDAY ACROSS THE AREA...BEFORE AMPLIFICATION OF UPPER TROUGH ACROSS GREAT LAKES AND EASTERN NOAM FINALLY ALLOW FRONT TO SETTLE OFF TO THE SOUTH MONDAY NIGHT. RATZER && .AVIATION... 645 AM CDT 1200 UTC TAFS...SHORT TERM CONCERN IS ON POTENTIAL OF LIFR AND IFR CIGS THIS MORNING. SATELLITE IMAGERY HAS BEEN INDICATING EXPANDING LOW CLOUD DECK WHICH DEVELOPED APPROX FROM KJOT TO KDPA...AND HAS SHIFTED EASTWARD TO ORD/MDW BETWEEN 11Z AND 12Z WITH SOME IFR/LIFR CIGS. FURTHER TO THE NORTH CLOSER TO THE ILLINOIS WISCONSIN STATELINE...LOW CLOUDS ARE MORE EXTENSIVE BUT GENERALLY BEING REPORTED ABOVE 600 FT. ANTICIPATING ABOUT 2 TO 3 HOURS OF THESE LIFR/IFR CIGS BEFORE BETTER MIXING BY MID MORNING. OTHERWISE...SOUTHWEST WINDS OF 5 TO 10 KNOTS THIS MORNING SHOULD GRADUALLY BECOME WESTERLY TOWARD MIDDAY WITH ACARS SOUNDINGS SHOWING WEST WINDS OF 10 TO 15 KNOTS JUST OFF THE SURFACE. DESPITE WEAK SURFACE GRADIENT...AM EXPECTING THAT THE WEST WINDS MIXED DOWN SHOULD LIMIT ANY EASTERLY COMPONENT CLOSER TO THE ILLINOIS LAKE MICHIGAN SHORELINE WITH POTENTIAL WEAK LAKE BREEZE. THUS...HAVE KEPT IN WEST WINDS THROUGH THE DAY ACROSS ALL TERMINALS. POTENTIAL OF MORE THUNDERSTORMS RETURNS FOR TONIGHT WITH NOCTURNAL JET REDEVELOPING AND A SHEARED VORT MAX APPROACHING THE MID MS VALLEY. PRESENT INDICATIONS WOULD SUGGEST BEST CHANCE FOR NIGHTTIME CONVECTIVE SYSTEM SOUTH OF THE TERMINALS...AND AT THIS FORECAST DISTANCE CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE PRECIP MENTION AT THIS TIME. SFC GRADIENT SHOULD CONTINUE TO SUPPORT WEAK WEST NORTHWEST WINDS OF AROUND 5 KNOTS TONIGHT. MARSILI && .MARINE... 326 AM CDT LOW PRESSURE WILL MOVE ACROSS THE WESTERN GREAT LAKES REGION TODAY. ALTHOUGH WINDS ARE DISTURBED ACROSS LAKE MICHIGAN FROM OVERNIGHT CONVECTION...SHOULD SEE LIGHT SOUTH WINDS IN ADVANCE OF THIS LOW PRESSURE TODAY BECOME WEST/NORTHWEST TOWARD EVENING AS THE LOW PRESSURE AREA MOVES INTO LOWER MICHIGAN. CANADIAN HIGH PRESSURE WILL THEN SLOWLY BUILD INTO THE WESTERN GREAT LAKES REGION LATE TONIGHT INTO TUESDAY PROVIDING NORTH WINDS. SOME GUSTS TO 15 TO 20 KNOTS ARE POSSIBLE TUESDAY ACROSS THE SOUTH HALF BEFORE THIS RIDGE BUILDS IN...BUT WINDS SHOULD THEN DIMINISH TUESDAY NIGHT INTO WEDNESDAY AS THE RIDGE OF HIGH PRESSURE CONTINUES TO BUILD SOUTHWARD. MARSILI && .LOT WATCHES/WARNINGS/ADVISORIES... IL...NONE. IN...NONE. LM...NONE. && $$
AREA FORECAST DISCUSSION
NWS BALTIMORE MD/WASHINGTON DC
946 AM EDT SUN JUL 20 2008 .SYNOPSIS... HIGH PRESSURE WILL CONTROL THE WEATHER PATTERN INTO MONDAY BRINGING WARM AND HUMID CONDITIONS. TROPICAL STORM CRISTOBAL WILL MOVE OUT TO SEA BY TUESDAY. A COLD FRONT WILL BRING A CHANCE FOR SHOWERS AND THUNDERSTORMS TUESDAY. THIS FRONT WILL STALL OUT JUST TO OUR SOUTH FOR THE MIDDLE OF THIS WEEK WITH WEAK HIGH PRESSURE NEARBY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... ...ANOTHER HOT AND HUMID DAY... WATER VAPOR LOOP SHOWS A RIDGE ACROSS THE WESTERN CONUS AND PLAINS. TROPICAL STORM CRISTOBAL WAS OFF THE SOUTH CAROLINA COAST...WITH AN UPPER LOW NEAR LAKE WINNIPEG TRAVERSING THE MEAN FLOW RESIDING ALONG THE CANADIAN BORDER. A POSSIBLE MCV WAS LOCATED NEAR OVER THE LOWER GREAT LAKES. ACARS 400-250MB WIND OBSERVATIONS SHOW A 80-110KT JET FROM THE PACIFIC NORTHWEST EAST NORTHEAST OVER THE UPPER GREAT LAKES AND NEW ENGLAND. LIGHT WINDS RESIDED OVER THE SOUTHEAST CONUS. 11Z SURFACE ANALYSIS PLACED A TROPICAL STORM CRISTOBAL OFF THE SOUTH CAROLINA COAST. A TROUGH EXTENDED NORTHWARD INTO THE CHESAPEAKE BAY...WITH A SECOND TROUGH IN THE LEE OF THE CENTRAL APPALACHIANS. THE NEXT BAROCLINIC ZONE STRETCHED FROM THE NORTHERN PLAINS EAST NORTHEAST ACROSS THE LOWER GREAT LAKES AND NEW ENGLAND. 12Z KIAD RAOB INDICATES VERY LITTLE THERMAL CHANGES IN VERTICAL PROFILE DURING THE PAST 24 HOURS...WITH SLIGHT WARMING IN THE MID LEVELS. THIS WILL TEND TO CAP CONVECTION TODAY. CONVECTIVE DEVELOPMENT MAY OCCUR ACROSS LOWER SOUTHERN MARYLAND WHICH IS WITHIN A CONVERGENCE ZONE NORTH OF THE TROPICAL STORM...AND WILL RETAIN RICH DEW POINTS. THIS CONVECTION MAY END UP BEING CAPPED AND MAY NOT END UP PRODUCING ENOUGH CHARGE SEPARATION FOR LIGHTNING. OTHERWISE...RUC HRRR WRF-ARW3 CONFIRMS THINKING THAT CONVECTION DEVELOPS ON TAIL OF LOWER GREAT LAKES MCV THIS AFTERNOON...APPROACHING THE MOUNTAINS LATE IN THE DAY. THIS ACTIVITY WILL BE HEADING INTO A LESS FAVORABLE CAPPED ENVIRONMENT SO BELIEVE IT WILL WEAKEN ACROSS THE MOUNTAINS THIS EVENING. MODIFIED KRNK RAOB INDICATED MUCH LESS INSTABILITY THAN FURTHER EAST...AND A MORE PRONOUNCED MID LEVEL CAP. OTHERWISE CUMULUS DEVELOPS DURING THE AFTERNOON AS TEMPERATURES ONCE AGAIN WARM WELL INTO THE 90S. SOUTHEASTERLY FLOW AHEAD OF THE LEE TROUGH ACROSS EASTERN ZONES SHOULD SERVE TO RETAIN HIGHER DEW POINTS AND 100 DEGREE HEAT INDEX VALUES (MOST NOTABLE IN URBAN AREAS AND ALONG THE BAY). WILL ISSUE A SPECIAL WEATHER STATEMENT LATER THIS MORNING PERTAINING TO HEAT INDEX VALUES. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... THE FRONTAL BOUNDARY WILL CONTINUE TO CREEP SOUTHWARD TOWARDS THE CWFA...WHILE CRISTOBAL CONTINUES ITS SLOW NORTH-NORTHEAST MOVEMENT OUT TO SEA OVERNIGHT. GENERALLY FAIR CONDITIONS...WITH CONTINUED ABOVE NORMAL TEMPERATURES EXPECTED. && .LONG TERM /MONDAY THROUGH SATURDAY/... A COOL FRONT WILL MOVE INTO THE REGION MONDAY WHILE CRISTOBAL CONTINUES TO MOVE OUT INTO THE ATLANTIC. WILL CONTINUE TO FAVOR THE GLOBAL GUIDANCE AS FAR AS TRACK AND TIMING OF CRISTOBAL. THIS WOULD KEEP US IN THE SUBSIDENCE REGION AS IT MOVES OUT TO SEA ON MONDAY. THE COOL FRONT IS STILL EXPECTED TO MOVE INTO THE REGION...BUT IT WILL BE QUITE WEAK WITH LITTLE TO NO FORCING OR TEMPERATURE GRADIENT. IN FACT...A DOWNSLOPING WESTERLY WIND MAY ACTUALLY ALLOW FOR SOME LOCATIONS TO TURN OUT A COUPLE DEGREES WARMER THAN SUNDAY. MAX TEMPS MONDAY WILL RANGE FROM THE MIDDLE 80S IN THE HIGHEST ELEVATIONS TO THE LOWER AND MIDDLE 90S ACROSS MOST OTHER LOCATIONS. WILL CONTINUE TO KEEP MONDAY DRY FOR NOW. COULDN`T RULE OUT A STRAY SHOWER/T-STORM DURING THE AFTERNOON/EVENING...BUT SINCE THIS SYSTEM APPEARS TO BE WEAK AND WE WILL REMAIN IN AN AREA OF SUBSIDENCE...DID NOT WANT TO BLANKET THE CWA WITH POPS. THE COOL FRONT WILL STALL OUT JUST TO OUR SOUTH TUESDAY WHILE A STRONGER WAVE OF LOW PRESSURE RIDES ALONG THE FRONT BRINGING A CHANCE FOR SHOWERS AND THUNDERSTORMS. WILL KEEP POPS DURING THE AFTERNOON/EVENING HOURS FOR NOW...DESPITE THE UNCERTAINTY IN THE TIMING OF THIS SYSTEM. DECENT HEIGHT FALLS ARE EXPECTED AS THIS SYSTEM PASSES THROUGH. GFS BUFKIT DOES SHOW UP TO 2000 J/KG OF MLCAPE ALONG WITH STEEP LOW/MID-LEVEL LAPSE RATES. IF TIMING OF THE DISTURBANCE DOES COME THROUGH DURING PEAK HEATING...THEN GUSTY WINDS AND HAIL WILL BE A THREAT FOR SOME THUNDERSTORMS. THE COOL FRONT WILL SETTLE JUST TO OUR SOUTH FOR THE MIDDLE PART OF THE WEEK WITH ITS EXACT LOCATION STILL UNCERTAIN AT THIS TIME. GUIDANCE DOES CONTINUE TO SHOW THE FRONT RETURNING NORTH AS A WARM FRONT BY THE END OF THE WEEK INTO THE WEEKEND. WILL KEEP POPS ACROSS THE SOUTHERN CWA FOR THE MIDDLE PORTION OF THE WEEK AND THEN GRADUALLY SHIFT THEM NORTHWARD BY THE WEEKEND. ANY SHOWER/T-STORM ACTIVITY DURING THIS TIME WOULD LIKELY BE CONFINED TO THE AFTERNOON AND EVENING HOURS. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/... SOUTH-SOUTHWEST WINDS RESIDE TODAY UNDER BUILDING CUMULUS AND A FEW MID CLOUDS. A FEW SHOWERS POSSIBLE NORTH OF THE TROPICAL STORM IN LOWER SOUTHERN MARYLAND...AND APPROACHING THE MOUNTAINS FROM THE OHIO VALLEY LATE DURING THE DAY. ALONG THE BAY...FLOW EXPECTED TO BECOME ONSHORE BY AFTERNOON. THE MID AND UPPER LEVEL CIGS WILL CONTINUE INTO THE OVERNIGHT HOURS. VFR CONDITIONS EXPECTED MONDAY AND MONDAY NIGHT. A DISTURBANCE WILL BRING A CHANCE FOR SHOWERS AND THUNDERSTORMS TUESDAY AFTERNOON/EVENING. THIS MAY BRING PERIODS OF SUBVFR CIGS AND VSBYS. GENERALLY VFR CONDITIONS ARE EXPECTED WEDNESDAY AND THURSDAY...BUT AN AFTERNOON/EVENING T-STORM CANNOT BE RULED OUT...MAINLY TOWARDS KCHO. && .MARINE... A SMALL CRAFT ADVISORY FOR THE MID BAY AND LOWER TIDAL POTOMAC RIVER REMAINS IS IN EFFECT FROM THE MID AFTERNOON THROUGH THIS EVENING. EXPECT SOUTHERLY CHANNELING TO DEVELOP THIS AFTERNOON WELL AHEAD OF TROPICAL STORM CRISTOBAL...WITH GUSTS AROUND 20 KNOTS. A FEW SHOWERS OR THUNDERSTORMS POSSIBLE IN THE ADVISORY AREA AS WELL THIS AFTERNOON. WIND GUSTS ASSOCIATED WITH A COOL FRONT MAY APPROACH SCA CRITERIA MONDAY AFTERNOON...BUT BUFKIT MOMENTUM TRANSFER SUGGESTS WIND GUSTS AROUND 15 KTS. NO FLAGS EXPECTED TUESDAY THROUGH THURSDAY. THERE IS A CHANCE FOR SHOWERS/T-STORMS TUESDAY AFTERNOON AND EVENING. && .TIDES/COASTAL FLOODING... WATER LEVELS ARE RUNNING AROUND ONE THIRD TO ONE HALF FOOT ABOVE NORMAL WITH THE FULL MOON. CRISTOBAL LOOKS TO REMAIN WELL SOUTH OF THE FORECAST AREA. HIGHEST TIDAL DEPARTURES SHOULD BE SUNDAY NIGHT AS THE SYSTEM TRACKS SOUTHEAST OF THE CHESAPEAKE BAY MOUTH. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO MIDNIGHT EDT TONIGHT FOR ANZ532>534-537. && $$ SYNOPSIS...LASORSA NEAR TERM...ROGOWSKI SHORT TERM...LISTEMAA LONG TERM...LASORSA AVIATION...ROGOWSKI/LASORSA MARINE...ROGOWSKI/LASORSA TIDES/COASTAL FLOODING...ROGOWSKI
AREA FORECAST DISCUSSION
NWS OMAHA/VALLEY NE
653 AM CDT SUN JUL 20 2008 .UPDATE... UPDATED FORECAST EARLIER TO ACCOUNT FOR ISOLATED TSTMS OVER A LARGER AREA THAN EXPECTED EARLIER. && .DISCUSSION... ISOLATED TSTMS CONTINUE TO POP UP FROM SOUTH OF KOLU TO WEST OF KOFK AND TO NEAR KONL. THIS SEEMS TO BE DUE TO ISENTROPIC UPGLIDE AROUND 315 K. STORMS MAY CONTINUE TO DEVELOP EWD THROUGH 18Z. && .PREV DISCUSSION... /ISSUED 346 AM CDT SUN JUL 20 2008/ DISCUSSION... TSTM CHANCES AND TEMPERATURES WILL CONTINUE TO BE THE MAIN CONCERNS FOR THE NEXT FEW DAYS. 00Z UPPER AIR CHARTS SHOWED THE FOLLOWING... A DECENT AMOUNT OF MOISTURE WAS IN PLACE AT 850 MB WITH DEWPOINTS IN THE TEENS C FROM WRN KS INTO NE AND IA. AT 700 MB...TEMPERATURES WERE QUITE WARM FROM NE WESTWARD. THE 10 DEGREE C ISOTHERM WAS LOCATED FROM SRN SD INTO CNTRL IA. STORMS LAST EVENING AND EARLY THIS MORNING HAD A HARD TIME DEVELOPING ANY FARTHER SOUTH THAN THE 11 C LINE AT 700 MB IN OUR AREA. AT 500 MB...TEMPERATURES WERE ALSO QUITE WARM...GENERALLY -5 TO -7 C. THERE WAS A THERMAL TROUGH FROM SASK INTO NERN MT. AT 300 MB...STRONGEST WINDS WERE NOTED FROM OR AND ID ACROSS SRN MT/NRN WY...THROUGH SD AND SRN MN. A JET SEGMENT OF 80 KTS WAS REPORTED BY AIRCRAFT ALONG THE MT/WY BORDER. THIS MAY COME INTO PLAY LATER TODAY. WATER VAPOR LOOP SHOWED FAIRLY DRY AIR IN PLACE IN THE MID LEVELS ACROSS OUR AREA...WITH LOTS OF MONSOONAL MOISTURE FROM MEXICO INTO THE SRN AND CNTRL ROCKIES. PRECIPITABLE WATER VALUES OF 1.50 OR MORE WERE NOTED FROM ERN TX...LA AND MS NWD INTO ERN NE...IA AND SRN MN. 08Z SURFACE ANALYSIS SHOWED A WEAK FRONTAL BOUNDARY FROM NERN IA INTO SWRN IA...ACROSS SRN NE AND INTO LOW PRESSURE OVER SERN WY. MODELS ARE HAVING A HARD TIME WITH THIS PATTERN...BUT THE 00Z NAM SEEMED SOMEWHAT REASONABLE. WEAK SURFACE BOUNDARY OVER OUR AREA WILL TRY TO LIFT NWD TODAY. MAIN FOCUS FOR TSTM ACTIVITY SHOULD BE NORTH OF THE FRONT...WHERE MID LEVEL TEMPERATURES ARE A LITTLE COOLER. THIS IS ALSO WHERE THE CHANCE OF SEVERE STORMS IS THE HIGHEST... WITH BULK SHEAR OF 30 KTS OR MORE. MIXED LAYER CAPE VALUES FROM THE 06Z NAM ALSO REACH 3000-4500 J/KG IN THAT AREA. HAVE HIGHS TODAY RANGING FROM THE LOWER 90S NORTH TO THE UPPER 90S SOUTH. MODELS SHOW UPPER LEVEL JET STREAK MOVING INTO MN AND WI BY LATE THIS AFTN/EVENING...PUTTING PARTS OF NE AND IA IN THE RIGHT ENTRANCE REGION FOR TONIGHT. STORMS MAY HAVE A TENDENCY TO DEVELOP SWD DURING THE NIGHT. KEPT BEST CHANCE OF TSTMS ACROSS THE NORTH... WITH POPS RANGING TO 14 OR LESS ALONG THE KS BORDER. LOWS WILL BE IN THE UPPER 60S NORTH TO LOWER 70S SOUTH. FARTHER OUT...DID NOT MAKE MANY CHANGES. WE GENERALLY REMAIN IN NW FLOW ALOFT EARLY IN THE WEEK WITH RIDGE AXIS TO OUR WEST. TROUGHS WILL BE IN PLACE OVER THE WRN U.S. AND OVER THE ERN STATES. FLOW DOES TEND TO FLATTEN LATER IN THE WEEK...BUT THEN THE GFS BUILDS A STRONG 500 MB RIDGE BY THE WEEKEND. THE ECMWF IS SIMILAR. THAT PATTERN WOULD TEND TO BE HOT AND MAINLY DRY FOR OUR AREA...WITH LOWS AROUND 70 AND HIGHS 90 TO 95. AVIATION... FOR TAF SITES KOMA/KLNK/KOFK WEAK SURFACE BOUNDARY EXPECTED TO REMAIN ACROSS THE AREA TODAY WITH POTENTIAL FOR THUNDERSTORMS AGAIN MAINLY AFTER 20Z. UNCERTAINTY IN TIMING AND LOCATION OF DEVELOPMENT PRECLUDES MENTION AT THIS TIME. OTHERWISE...VFR CONDITIONS THROUGH MOST OF THE PERIOD. && .OAX WATCHES/WARNINGS/ADVISORIES... NE...NONE. IA...NONE. && $$ DISCUSSION...MILLER AVIATION...FOBERT
AREA FORECAST DISCUSSION...UPDATED
NWS MORRISTOWN TN
1001 AM EDT SUN JUL 20 2008 .DISCUSSION... ACARS SOUNDINGS THIS MORNING IN THE TN VALLEY SHOW THAT THE MIDLEVEL INVERSION IS STILL IN PLACE. HOWEVER...UPSTREAM RAOBS TO THE NORTH AND WEST INDICATE A WEAKER CAP...AND MODEL FORECAST SOUNDINGS SHOW THAT THE CAP WILL GRADUALLY WEAKEN THIS AFTERNOON. SURFACE DEWPOINTS ARE QUITE A BIT HIGHER TODAY...SO WITH ADDITIONAL MOISTURE AND A WEAKER CAP...EXPECT BETTER CHANCES OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON. FOR THE UPDATE...WILL INCREASE POPS TO SCATTERED IN THE PLATEAU. FORECAST HIGH TEMPS LOOK GOOD. && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DGS