FXUS61 KPHI 261712
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1212 PM EST THU NOV 26 2009
.SYNOPSIS...
LOW PRESSURE WILL TRACK SLOWLY EASTWARD THROUGH THE GREAT LAKES
REGION TONIGHT AND THURSDAY AS ANOTHER LOW PRESSURE SYSTEM ORGANIZES
OFF THE EAST COAST. THESE SYSTEMS WILL MERGE ACROSS EASTERN NEW
ENGLAND FRIDAY. A STRONG COLD FRONT IS FORECAST TO MOVE THROUGH OUR
AREA FRIDAY MORNING. HIGH PRESSURE WILL BUILD IN FOR THE WEEKEND AND
LAST INTO MONDAY. THE NEXT COLD FRONT WILL APPROACH FROM THE WEST BY
MONDAY NIGHT.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
OUR REGION IS BETWEEN SYSTEMS TODAY WITH ONE OVER THE GREAT LAKES
AND OHIO VALLEY AND A SECONDARY STORM OFF THE NORTH CAROLINA
COAST. THERE IS NOT MUCH LOW-LEVEL FLOW AND WHAT IS PRESENT IS
FROM THE NORTHEAST AND EAST. A COMPARISON OF THE 00Z/12Z STERLING,
VIRGINIA RAOB INDICATES THAT THE DEPTH OF THE LOW-LEVEL MOISTURE
HAS DECREASED SOME. IT APPEARS THAT SOME SUBSIDENCE ON THE
NORTHWESTERN SIDE OF THE DEVELOPING LOW OFF THE NORTH CAROLINA
COAST HAS ALLOWED ENOUGH SINKING AIR TO ERODE THE LOW CLOUDS
ACROSS NORTHERN NEW JERSEY. THIS THINNING IS NEARLY LINED UP ALONG
THE WESTERN EDGE OF THE HIGHER LEVEL CLOUD SHIELD. ELSEWHERE,
PLENTY OF LOW CLOUDS CONTINUE, HOWEVER THERE ARE SIGNS OF IT
STARTING TO THIN IN SOME AREAS. THE AREAS OF FOG, SOME LOCALLY DENSE,
HAS BEEN LIFTING QUITE A BIT OVER THE LAST HOUR OR SO, THEREFORE
WE DID NOT CARRY ANY ADDITIONAL FOG PAST THE NOON HOUR. AS SOME
DRIER AIR GRADUALLY WORKS IN, WE ARE EXPECTING SOME ADDITIONAL
BREAKS IN THE CLOUDS TO OCCUR. THE HOURLY GRIDS WERE ADJUSTED
BASED ON TRENDS SO FAR THIS MORNING AND THE HIGH TEMPERATURES WERE
ADJUSTED SLIGHTLY IN SOME AREAS.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
THE APPROACHING UPPER VORTICITY LOBE AND THE SFC LOWS ADVANCING
TOWARD THE AREA WILL BRING AN INCREASED CHANCE FOR RAIN TO THE
AREA TONIGHT. THE RAIN CHANCES WILL DECREASE FROM SOUTH TO NORTH
ON FRIDAY AS DRIER AND COLDER AIR ADVANCE OVER THE AREA. A COLD
FRONT WILL ADVANCE OVER THE AREA FRIDAY MORNING AND GUSTY WEST TO
NORTHWEST WINDS WILL DEVELOP OVER THE AREA. GUSTS AROUND OR OVER 30
MPH ARE EXPECTED. HIGH TEMPERATURES WILL GENERALLY BE IN THE 40S
BUT THE GUSTY WINDS WILL MAKE IT FEEL MUCH COLDER. OVER THE SOUTHERN
POCONOS ANY LINGERING RAIN SHOWERS MAY MIX WITH SOME SNOW SHOWERS
FRIDAY NIGHT. NO ACCUMULATIONS ARE EXPECTED ATTM.
HIGH PRESSURE WILL BUILD IN LATER FRIDAY NIGHT AND SATURDAY. THIS
SHOULD PUT AN END TO ANY REMAINING PRECIPITATION ACROSS THE NORTH.
SKIES WILL CLEAR OUT FROM SOUTH TO NORTH AS THE DAY PROGRESSES.
&&
.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
AT THE UPPER LEVELS, A TROUGH IS FORECAST TO BE LIFTING TO OUR
NORTHEAST ON SATURDAY EVENING. MEANWHILE, A RIDGE IS EXPECTED TO
EXTEND FROM THE SOUTHEASTERN STATES UP OVER THE UPPER MISSISSIPPI
RIVER VALLEY AT THAT TIME. THE RIDGE AXIS SHOULD DRIFT TO THE EAST,
PASSING OVERHEAD ON SUNDAY AFTERNOON. WE ARE FORECAST TO BE ON THE
NORTHERN EDGE OF SURFACE HIGH PRESSURE FROM SATURDAY NIGHT INTO
EARLY MONDAY, WITH DRY WEATHER AND NEAR SEASONABLE TEMPERATURES
ANTICIPATED.
AN UPPER LEVEL TROUGH IS EXPECTED TO DROP ACROSS THE GREAT LAKES AND
THE NORTHEASTERN STATES DURING THE MONDAY AND TUESDAY TIME FRAME. IT
SHOULD PUSH A COLD FRONT THROUGH OUR REGION LATE ON MONDAY NIGHT OR
EARLY ON TUESDAY. AS A RESULT, WE HAVE MENTIONED A CHANCE FOR
SHOWERS. TEMPERATURES MAY BE LOW ENOUGH FOR SOME SNOW FLAKES UP IN
THE POCONOS AND IN FAR NORTHERN NEW JERSEY.
THE SURFACE COLD FRONT IS FORECAST TO STALL OFF THE COAST.
MEANWHILE, ANOTHER UPPER RIDGE SHOULD BUILD UP FROM THE SOUTHWEST
WITH ITS AXIS PASSING OVERHEAD ON WEDNESDAY. HIGH PRESSURE IS
EXPECTED TO PASS TO OUR NORTH AT THAT TIME, BRINGING DRY WEATHER TO
OUR NORTHERN COUNTIES FROM LATE TUESDAY INTO EARLY WEDNESDAY. WITH
THE SURFACE FRONT NEARBY, WE WILL KEEP SLIGHT CHANCE OR LOW CHANCE
POPS FOR OUR SOUTHERN COUNTIES.
AN UPPER TROUGH IS EXPECTED TO BEGIN APPROACHING FROM THE SOUTHWEST
ON WEDNESDAY, ALONG WITH SURFACE LOW PRESSURE FROM THE SOUTHWEST AND
SOUTH. AS A RESULT, WE HAVE INCLUDED CHANCE POPS FOR RAIN IN THE
FORECAST.
&&
.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
THE SOON TO BE ISSUED TAFS WILL MAINTAIN A MVFR CIG AND VSBYS AT
TIMES UNTIL THE COLD FRONT MOVES THRU LATER TONIGHT AND THEN VFR
WITH WINDY CONDITIONS ON FRIDAY.
THERE IS STILL A WEAK INVERSION ALOFT AND IT LOOKS AS THOUGH THE
STRATOCU MVFR CIG IS EXPANDING AND NOT CONTRACTING UNDERNEATH IT.
ALSO SOME STRATOCU IS MOVING WEST FROM THE OCEAN. BETWEEN THE TWO
IT APPEARS IT WILL BE DIFFICULT FOR CIGS TO IMPROVE MUCH FROM
CURRENT CONDITIONS FOR THE REMAINDER OF THE AFTERNOON.
AS EVENING ARRIVES, THIS PROCESS SHOULD REVERSE AND THE 22Z-04Z
CIG IS AN AVERAGE FOR THE TIME PERIOD AS A WHOLE, SLIGHTLY HIGHER
EARLY AND LOWER LATER. WE MAINTAINED THE POSSIBILITY OF SOME MVFR
FOG REFORMING THIS EVENING AS WINDS SHOULD STILL BE LIGHT.
ABOUT A FOUR HOUR PERIOD OF SHOWERS IS FORECAST OVERNIGHT AS THE COLD
FRONT MOVES THROUGH THE REGION. PCPN INTENSITY IS NOT EXPECTED TO
GET HEAVY AND WE MAINTAINED MVFR CONDITIONS AS THIS BAND OF
SHOWERS MOVES THROUGH. ONCE THE COLD FRONT REACHES THE COAST AND
THE LOW PRESSURE SYSTEM INTENSIFIES, WINDS WILL INCREASE AND BECOME
QUITE GUSTY ON FRIDAY. THE WIND GUSTS DURING THE EARLY MORNING
FORECAST PERIOD IS MORE OF A BRIDGE TO THIS INCREASE IN GUSTINESS
AFTER THE SUN RISES. IT WILL BE PRETTY COLD ALOFT AND THIS SHOULD
MAKE IT EASY FOR CU OR STRATOCU TO BE AROUND DURING THE DAY, BUT
CURRENT EXPECTATIONS ARE FOR THE CIGS TO REMAIN VFR. WIND GUSTS FRIDAY
AFTERNOON (AS REFLECTED IN THE PHL 30 HR TAF) SHOULD REACH AROUND 35
KNOTS.
OUTLOOK...
STRONG GUSTY WINDS WITH VFR CONDITIONS SHOULD PERSIST INTO FRIDAY
NIGHT AND MOST OF SATURDAY BEFORE WINDS DIMINISH SATURDAY NIGHT.
HIGH PRESSURE SHOULD BUILD IN FROM THE WEST FOR LATE SATURDAY,
SUNDAY AND EARLY MONDAY WITH BASICALLY VFR CONDITIONS. A COLD
FRONTAL PASSAGE LATER MONDAY WOULD BRING THE NEXT CHANCE FOR
EITHER MVFR OR IFR CONDITIONS.
&&
.MARINE...
SCA HAVE BEEN ISSUED FOR LATE TONIGHT AND GALE WARNINGS HAVE BEEN
ISSUED FOR FRIDAY AND FRIDAY NIGHT.
INITIALLY WE ARE IN A LIGHT WIND SITUATION WELL AHEAD OF THE COLD
FRONT TODAY. HOWEVER, ONCE A COLD FRONT MOVES THROUGH FROM THE NW
TONIGHT, WINDS WILL INCREASE DUE TO COLDER AIR ON WARMER WATERS AS
WELL AS AN INCREASED GRADIENT. INITIALLY THE GRADIENT ONLY SUPPORTS
WINDS TO 25 KT TONIGHT, BUT ON FRIDAY, THE GRADIENT SUPPORTS GUSTS
TO 35-40 KT AND PERHAPS AS HIGH AS 45 KT FRIDAY NIGHT.
THE GALES MAY CONTINUE INTO SATURDAY. HOWEVER, THE GRADIENT SLOWLY
RELAXES AND DUE TO THAT WINDS SHOULD DECREASE DURING SATURDAY AND
ESPECIALLY SAT NIGHT. BY SUNDAY THE THE COLD AIR SHOULD HAVE MOVED
AWAY AND A SW FLOW SHOULD BE OVER THE AREA ALLOWING THE WINDS TO
DROP UNDER 25 KT. THESE WINDS ARE FORECAST TO CONTINUE THROUGH
MONDAY.
ALSO, TIDES WILL BE WELL BELOW NORMAL WITH NEGATIVE DEPARTURES OF 1
TO 2 FT ON THE OCEAN LATE FRIDAY NIGHT AND SATURDAY. HOWEVER, THESE
DEPARTURES DO NOT APPEAR LARGE ENOUGH FOR ANY LOW WATER
ADVISORIES.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 AM EST
FRIDAY FOR ANZ430-431-450>455.
GALE WARNING FROM 6 AM FRIDAY TO 6 AM EST SATURDAY FOR ANZ430-
431-450>455.
&&
$$
SYNOPSIS...O'HARA
NEAR TERM...GORSE
SHORT TERM...O'HARA
LONG TERM...IOVINO
AVIATION...GIGI
MARINE...STAUBER
