FXUS61 KPHI 030108
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
808 PM EST WED DEC 2 2009
.SYNOPSIS...
LOW PRESSURE OVER THE LOWER OHIO VALLEY WILL MOVE NORTHEAST
REACHING NEW YORK STATE THURSDAY MORNING. THE COLD FRONT
ASSOCIATED WITH THE LOW WILL CROSS OUR AREA LATE TONIGHT. THE LOW
PRESSURE SYSTEM WILL CONTINUE RAPIDLY NORTHEASTWARD AND AWAY FROM
OUR REGION DURING THURSDAY. HIGH PRESSURE WILL GRADUALLY BUILD IN
FRIDAY AND FRIDAY NIGHT. AN AREA OF LOW PRESSURE IS THEN EXPECTED
TO DEVELOP OFF THE SOUTHEASTERN UNITED STATES COAST AND TRACK OFF
THE MID ATLANTIC COAST SATURDAY AND SATURDAY NIGHT. HIGH PRESSURE
WILL BEGIN PUSHING IN FROM THE WEST SUNDAY AND DOMINATE OUR
WEATHER THROUGH EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
THE GFS LOOKS TO HAVE VERIFIED BETTER THAN THE WRF-NMM FROM THE
SFC UP TO 850MB AS OF THE 00Z RAOBS AND SFC OBSERVATIONS. ITS QPF
FIELDS WERE BETTER, NOT PERFECT WITH CONVECTION, BUT NO MODEL EVER
IS. IT DID PARTICULARLY BETTER THAN THE WRF-NMM OVER SERN GA/SRN
SC AND NERN FL. THIS IS PARTICULARLY IMPORTANT TO US BECAUSE TO
THE LEFT OF THIS CONVECTION THE 18Z WRF-NMM TAKES A 65 KT JET ALG
THE GA/FL BORDER AND INCREASES IT TO 102 KTS AS IT PASSES E OF NJ
AT 12Z THU MORNING. ITS CORRESPONDING 925MB JET IS ALSO MORE
ROBUST THAN EITHER THE LATEST RUC OR 18Z GFS. WE WILL CONTINUE TO
MONITOR THE OBSERVATIONS IN THE SE AS WE FOLLOW THIS ALONG.
CLOSER TO HOME THE FORECAST 850MB AND 925MB WIND FIELDS ARE
VERIFYING PRETTY GOOD AND WE ARE SEEING APPROXIMATELY ABOUT A 50
PERCENT TRANSFER OF THESE WIND SPEEDS TO REACH THE SFC. WE WOULD
EXPECT THIS PERCENTAGE TO INCREASE ACROSS THE EASTERN ZONES AS
THEY EITHER GET CLOSE TO OR INTO THE WARM SECTOR. THE FORECAST
MODELS THOUGH KEEP SOME SEMBLANCE OF A WEAK PCPN INDUCED
INVERSION. ALSO, WHILE THE CONVECTION IS GOING TO TOWN IN SC AND
GA, THE TRAJ WOULD HAVE THIS PASS TO OUR E. IN FACT THERE IS NO
SFC BASED INSTABILITY FORECAST ALG OUR EASTERN CWA. ELSEWHERE THE
MODELS ARE FORECASTING A POCKET OF INSTABILITY ASSOCIATED WITH THE
STRONG SHORT WAVE IN THE TENNESSEE VALLEY TO MOVE ACROSS OUR CWA.
THIS REMAINS OUR PRIMARY REASON FOR KEEPING THUNDER IN THE
FORECAST FOR OVERNIGHT.
BECAUSE OF THE LACK OF SFC BASED CONVECTION FARTHER TO THE EAST
AND THE SLIGHTLY MORE OFFSHORE POSN (EVEN THE 18Z 100 KT WRF) OF
THE 925MB AND 850MB JETS BY THE MODELS WE HAVE KEPT THE WIND ADVY
AREA AS IS. ONLY CHANGE WE MADE BECAUSE THE GFS TIMING IS BETTER
THAN THE WRF-NMM AT 00Z, WE SPED THE END OF THE CATEGORICAL PCPN
UP BY A FEW HOURS AND LOWERED POPS ON THU MRNG. ANY TWEAKS TO
TEMPS AND DEW POINTS WERE DONE BASED ON CURRENT CONDITIONS AND
LATEST LAPS GUIDANCE. THE GENERAL GIST OF TEMPS RISING AND
POSSIBLY FALLING RIGHT AT DAWN LOOKS GOOD.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
WITH THE RAPID MOVEMENT OF THE LOW PRESSURE SYSTEM, DRY AIR
WRAPPING AROUND THE BACK SIDE OF THE STORM WILL BE MOVING INTO OUR
AREA AROUND DAYBREAK. THE THREAT FOR MEASURABLE RAIN WILL BE OVER
THROUGHOUT THE REGION BY MID MORNING. WINDS WILL SWING AROUND TO
SOUTHWEST BY DAYBREAK AND THEN TO WEST TOWARD NOON. WILL STILL SEE
GUSTS TO 25 OR 30 MPH THROUGH MUCH OF THE DAY. THE GUSTINESS WILL
DROP OFF LATE IN THE DAY AND CONTINUE TO DIMINISH THURSDAY NIGHT.
AS THE DRY AIR PUSHES IN, SKIES WILL BEGIN TO CLEAR AND WE SHOULD
SEE PLENTY OF SUNSHINE FROM MID TO LATE MORNING ON. TEMPERATURES
WILL BE ON THE MILD SIDE THURSDAY WITH HIGHS IN THE MID 50S TO MID
60S.HIGH PRESSURE PUSHING IN FROM THE WEST WILL BRING FAIR WEATHER
THURSDAY NIGHT THROUGH FRIDAY NIGHT. COLDER AIR WILL BEGIN MOVING
IN THURSDAY NIGHT. LOWS WILL DROP INTO THE 30S. HIGHS FRIDAY IN
THE 40S TO LOWER 50S. LOWS FRIDAY NIGHT WILL RANGE FROM THE MID
20S TO THE MID 30S. CLOUDS MOVING IN FROM THE SOUTH WILL ACTUALLY
KEEP TEMPERATURES FROM DROPPING LOWER. THE CLOUDS WILL BE RUNNING
OUT AHEAD OF A DEVELOPING LOW PRESSURE SYSTEM OFF THE SOUTHEAST
COAST. THIS LOW WILL INTENSIFY AND MOVE NORTHEAST SATURDAY. AT
THIS TIME IT APPEARS THAT THE TRACK OF THE LOW WILL BE FAR ENOUGH
OFF THE COAST SO THAT OUR REGION WILL BE ON THE NORTHWEST FRINGE.
EVEN SO, MUCH OF OUR AREA WILL SEE SOME PRECIPITATION SATURDAY.
THE PRECIPITATION WILL BE IN THE FORM OF INTERMITTENT RAIN OR
SNOW, WITH THE HEAVIEST OVER OUR SOUTHERN AND COASTAL SECTIONS
WHERE TEMPERATURES WILL BE THE WARMEST. TEMPERATURES THROUGHOUT
MOST OF OUR REGION WILL REMAIN IN THE 30S FOR MUCH OF SATURDAY. SO
EVEN IF THE PRECIPITATION FALLS AS MOSTLY SNOW, IT SHOULD BE
RELATIVELY LIGHT AND IS NOT EXPECTED TO ACCUMULATE ON ROADWAYS.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
THE PERIOD BEGINS WITH THE DEPARTURE OF THE LOW WELL OFFSHORE AND
THE ARRIVAL OF SURFACE HIGH PRESSURE. THIS HIGH WILL DOMINATE OUR
WEATHER SUNDAY, WEAKEN A BIT ON MONDAY, AND REESTABLISH ITSELF ON
TUESDAY. WEDNESDAY LOOKS WET AT THE MOMENT AS SOME SOUTHERN JET
ENERGY REACHES THE MID-ATLANTIC COAST.
TEMPERATURES ARE EXPECTED TO BE IN THE NORMAL RANGE DURING THE
PERIOD. BUT BECAUSE NOVEMBER WAS AS WARM AS IT WAS (+3.8, 7TH
WARMEST ON RECORD), IT'S GOING TO FEEL COOL IF NOT COLD. HIGH
TEMPERATURES, FROM SUNDAY THROUGH WEDNESDAY ARE ONLY GOING TO
SETTLE IN THE 40S. PHILADELPHIA HAS ONLY HAD FOUR DAY THUS FAR THIS
FALL WHERE THE TEMPERATURE HASN'T HIT AT LEAST 50. LOWS ACROSS THE
REGION ARE GOING TO BE IN THE 20S AND 30S.
WITH THE COOLER/COLDER AIR, MIXED PRECIPITATION CAN BE EXPECTED
ACROSS PORTIONS OF THE CWA WITH BOTH THE SATURDAY SYSTEM AND THE
TUESDAY NIGHT/WEDNESDAY SYSTEM.
&&
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
THE FOLLOWING
DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY
AND SURROUNDING AREAS.
AREA OBSERVATIONS IDICATE THAT WE'RE LOSING OUR VFR CONDITIONS,
ESPECIALLY ACROSS THE WESTERN TERMINALS. MVFR AND IFR CONDITIONS
WILL CONTINUE TO SETTLE IN THE NEXT COUPLE OF HOURS AND THEN PERSIST
THROUGH THE NIGHT.
WINDS ALOFT WILL BE QUITE STRONG CAUSING SOME WIND SHEAR. SPEEDS AT
2K FT WILL BE IN THE 40-45 KT. HEAVY SHOWERS OR THUNDERSTORMS
OVERNIGHT COULD ALSO MIX THESE WINDS DOWN TO THE SURAFCE.
A WARM FRONT WILL MOVE THROUGH FROM THE SOUTH TOWARD DAYBREAK. THIS
WILL BE FOLLOWED QUICKLY BY A COLD FRONT FROM THE WEST. CIGS AND
VSBYS WILL IMPROVE RAPIDLY TO MVFR AROUND SUNRISE AND THEN TO VFR
2-3 HRS LATER. HOWEVER, WINDS WILL REMAIN GUSTY WITH SUSTAINED
SPEEDS AROUND 15 KT AND GUSTS TO 30 KT. WINDS SHOULD DIMINISH SLOWLY
DURING THURSDAY AFTERNOON.
OUTLOOK...
THE NEXT CHANCE FOR PRECIPITATION IS ON SATURDAY AS A LOW PRESSURE
SYSTEM IS EXPECTED TO MOVE EAST WELL OFF THE COAST.
&&
.MARINE...
GALE FORCE WIND GUSTS ARE EXPECTED TO DEVELOP BEFORE MIDNIGHT IN
RESPONSE TO THE RAPIDLY INTENSIFYING LOW PRESSURE COMING OUT TO THE
TENNESSEE VALLEY. THIS SLOW RACE TO NEW YORK STATE BY EARLY THURSDAY
ALLOWING A TRAILING COLD FRONT TO MOVE THROUGH THE AREA WATERS.
WINDS SHOULD GUST UP TO 45 KT LATE TONIGHT. THE GUSTY WINDS SHOULD
CONTINUE THURSDAY MORNING BEHIND THE COLD FRONT, BUT DIMINISH DURING
THE DAY AND DROP BELOW GALE DURING THE AFTERNOON AS THE GRADIENT
WEAKENS.
HIGH PRESSURE WILL THEN BUILD OVER THE AREA THURSDAY AFTERNOON
THROUGH THE WEEKEND. DUE TO THIS HIGH, WINDS SHOULD BECOME MORE
TRANQUIL AND DROP BELOW SCA FRIDAY. EVEN SO, A LOW PRESSURE
SYSTEM WILL ALSO MOVE BY TO THE EAST ON SATURDAY AND COULD BRING AN
INCREASE IN THE WINDS BEGINNING FRIDAY NIGHT AND THE CHANCE OF RAIN
AND/OR SNOW SHOWERS SAT AND SAT NIGHT. MORE TRANQUIL CONDITIONS
SHOULD DEVELOP SUNDAY AND MONDAY.
&&
.TIDES/COASTAL FLOODING...
WE HAVE CONTINUED THE COASTAL FLOOD ADVISORY FOR MINOR TIDAL
FLOODING. HOWEVER, DEPARTURES SHOULD ONLY BE UP TO 1 FT. THIS MEANS
THAT FLOODING IS NOT EXPECTED TO BE WIDESPREAD OR SEVERE. HOWEVER,
IN AREAS WHERE WE HAVE LOST BEACHES AND DUNES DUE TO PREVIOUS
STORMS, THERE COULD BE A BIT MORE OF AN EFFECT FROM THE TIDES. ONE
PIECE OF GOOD NEWS IS THAT THE WINDS SHOULD SHIFT TO SW JUST BEFORE
HIGH TIDE OCCURS AND MAY LESSEN THE DEPARTURE JUST BEFORE HIGH TIDE.
HIGH TIDE OCCURS ON THE OCEAN FRONT BETWEEN 7 AND 830 AM. ALSO HAVE
ISSUED IT FOR THE NJ SIDE OF THE DELAWARE BAY FOR THE EAST POINT
AREA WHERE THE HIGH TIDE IS BETWEEN 8 AND 9 AM.
GALE FORCE SE AND THEN S WINDS ON THE OCEAN SHOULD KICK UP THE SEAS
TONIGHT AND FOR THAT REASON THE PREVIOUS ISSUED SURF ADVISORY WILL
BE CONTINUED.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...WIND ADVISORY FROM MIDNIGHT TONIGHT TO 6 AM EST THURSDAY FOR
NJZ014-026.
COASTAL FLOOD ADVISORY FROM 1 AM TO 10 AM EST THURSDAY FOR
NJZ014-021-023>026.
HIGH SURF ADVISORY FROM 1 AM TO 10 AM EST THURSDAY FOR NJZ021-
023>026.
WIND ADVISORY UNTIL 6 AM EST THURSDAY FOR NJZ024-025.
DE...COASTAL FLOOD ADVISORY FROM 1 AM TO 10 AM EST THURSDAY FOR
DEZ003-004.
HIGH SURF ADVISORY FROM 1 AM TO 10 AM EST THURSDAY FOR DEZ004.
WIND ADVISORY UNTIL 6 AM EST THURSDAY FOR DEZ004.
MD...NONE.
MARINE...GALE WARNING UNTIL 1 PM EST THURSDAY FOR ANZ430-431-450>455.
&&
$$
SYNOPSIS...RPW
NEAR TERM...GIGI/RPW
SHORT TERM...RPW
LONG TERM...KRUZDLO
AVIATION...KRUZDLO/STAUBER
MARINE...STAUBER
TIDES/COASTAL FLOODING...STAUBER
