FXUS61 KPHI 160812
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
312 AM EST WED DEC 16 2009
.SYNOPSIS...
STRONG HIGH PRESSURE WILL BUILD IN FROM THE NORTH AND WEST AND
THEN WEAKEN THROUGH THE WORK WEEK. A SYSTEM THAT WILL DEVELOP
NEAR THE GULF OF MEXICO AND MOVE OUT OVER THE ATLANTIC MAY HAVE
SOME EFFECT ON US LATE IN THE WEEKEND.
&&
.NEAR TERM /THROUGH TODAY/...
THE FLURRIES THAT WERE MOVING ACROSS OUR AREA EARLY THIS MORNING
WERE ASSOCIATED WITH A VORT MAX ROTATING THROUGH. THAT VORT MAX
WAS FORECAST TO BE OFF THE COAST BY 12Z, AND SIMPLY TIMING THE
MOVEMENT OF OUR WIDELY SCATTERED ACTIVITY ALSO HAD IT OFF THE COAST
BY THEN. WE THEREFORE CONFINED ANY FLURRY ACTIVITY AFTER DAYBREAK
TO THE FAR NORTHWEST, AND THAT WAS DUE PRETTY MUCH TO THE COLD
FETCH OFF THE GREAT LAKES. THE FAR NORTHWEST HAD SOME MOISTURE
PROGGED IN THE SNOW GROWTH REGION WITHIN THE MIXED LAYER, BUT
MODEL SOUNDINGS ONLY MIXED US UP TO 3K OR 4K. WE NOTED A FAIR
AMOUNT OF FLURRY ACTIVITY FROM CENTRAL PA WEST EARLY THIS MORNING
/A POSSIBLE FLY IN THE FORECAST OINTMENT/, BUT WE WERE THINKING
THAT DOWNSLOPING WOULD KEEP THAT FROM MAKING IT HERE. AS WE MOVED
FURTHER SOUTHEAST TODAY, WE TRENDED TOWARD LESS IN THE WAY OF
CLOUDS.
THE NORMAL DIURNAL TREND ARGUED FOR INCREASING WINDS AFTER
DAYBREAK, BUT THE EXITING VORT MAX ARGUED THE OTHER WAY. WE
MAINTAINED WINDS AT PRE-DAWN LEVELS INTO THE EARLY AFTERNOON AND
HAD THEM DIMINISH SOME THEREAFTER. GUIDANCE TEMPERATURES WERE IN
PRETTY GOOD AGREEMENT WITH CONTINUITY AND WERE ACCEPTED.
&&
.SHORT TERM /TONIGHT THROUGH FRIDAY/...
ANOTHER VORT MAX MOVES ACROSS THE AREA TONIGHT WITH SOME
REINFORCING COLD AIR. THE ATMOSPHERE LOOKS TO BE DRIER, SO WE ARE
CONFINING SNOW FLURRIES TO THE NORTHWEST AND GOING MOSTLY CLEAR
ELSEWHERE FOR NOW. WINDS MAY PICK UP SOME AS THE SECONDARY PUSH
OCCURS. GUIDANCE TEMPS AGAIN ARE IN GOOD AGREEMENT WITH CONTINUITY
AND ARE ACCEPTED.
THURSDAY THROUGH FRIDAY LOOKS DRY, ALTHOUGH WARM AIR ADVECTION
ALOFT AND AN UPPER JET MAY BRING SOME MID AND HIGH CLOUDINESS INTO
THE AREA THURSDAY NIGHT INTO FRIDAY. WINDS SHOULD BE DIMINISHING
THROUGH THE PERIOD, AND WERE IT NOT FOR THE POSSIBILITY OF CLOUDS
WE WOULD HAVE UNDERCUT GUIDANCE MINS ON THURSDAY NIGHT WITH
EXCELLENT RADIATING CONDITIONS. AS IT IS, WE CONTINUED TO WALK A
GUIDANCE-CONTINUITY LINE, WHICH HAS WORKED REASONABLY WELL.
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THE MODELS CONTINUE TO DIFFER AS TO HOW THEY HANDLE THE ROTATING
UPPER LOW TO OUR NORTH ALONG WITH THE ASSOCIATED SHARPENING TROUGH.
AT THE SURFACE, ALL MODELS DEVELOP A LOW ALONG THE SE COAST AND
HEAD IT NE. MOST OF THE MODELS KEEP IT FAR ENOUGH S AND E OF OUR
AREA SO THAT IT JUST BRUSHES OUR SE SECTIONS. THE OUTLIER AT THIS
TIME IS THE ECMWF WHICH SHARPENS THE TROUGH AND DEVELOPS AN INTENSE
EAST COAST STORM. IT IS ALSO MUCH FASTER THAN THE REST OF THE MODELS
AND WOULD HAVE THE BIGGEST IMPACT LATE SATURDAY AND SATURDAY NIGHT
RATHER THAN LATE SATURDAY NIGHT AND SUNDAY. FOR NOW WE WILL GO WITH
THE MAJORITY AND BRING INCREASING CLOUDINESS IN LATE SATURDAY INTO
SATURDAY NIGHT AND CALL FOR A CHANCE OF SNOW INLAND AND RAIN OR SNOW
ALONG THE COAST LATE SATURDAY NIGHT AND SUNDAY. ONCE THE LOW MOVES
OFF TO THE NE, HIGH PRESSURE WILL BRING ANOTHER BATCH OF COLD AIR
INTO OUR AREA FOR THE BEGINNING OF NEXT WEEK.
&&
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
STRONG HIGH PRESSURE WILL BUILD INTO THE REGION THROUGH FRIDAY,
BRINGING VFR CONDS TO THE AREA. NWLY SFC FLOW WILL BE QUITE STRONG
AND GUSTY TODAY AND GUSTS TO 25 KT ARE FCST. THE WIND SHOULD REMAIN
GUSTY TONIGHT AND WE SHUD LOSE SOME OF THE GUSTINESS ON THURSDAY,
WITH A GRADUAL DECREASE IN WIND SPEED. THE NW FLOW WILL ALSO CARRY
SOME MOISTURE FROM THE GRTLKS RESULTING IN SOME STREAMERS OF SCT/BKN
LOW CLDS AGAIN TODAY MORE LIKELY AT RDG/ABE. A BRIEF -SHSN HIT KABE
EARLIER TONIGHT AND DROPPED VSBY AND CIGS SUBSTANTIALLY. HOWEVER,
AS THIS FIRST DISTURBANCE MOVES THROUGH, MOST OF THE UPR LVL SUPPORT
FOR CONTINUED SNOW SHOWERS WILL DIMINISH.
OUTLOOK...
GENERALLY VFR CONDITIONS ARE FORECAST FOR MUCH OF THE REST OF THIS
WEEK.
&&
.MARINE...
STRONG NWLY FLOW HAS HIT THE AREA WATERWAYS AN WINDS AND SEAS HAVE
CLIMBED AS A RESULT. AS A S/WV PASSES THROUGH, GUSTS ARE
APPROACHING 35 KT AS THE COLD AIR MOVES OVER THE WARMER WATER.
GUSTS ARE EXPECTED TO DECREASE AS THE VORT EXITS THE REGION LATER.
THE CURRENT SCA WILL BE EXTENDED UNTIL 18/00Z, MAINLY FOR WINDS AS
THE NWLY FLOW REMAINS QUITE GUSTY. ATTM, IT APPEARS THAT ANY GUSTS
TO GALE WOULD BE SHORT-LIVED AND NOT WIDESPREAD AND THE
PREPONDERANCE OF THE GUIDANCE INDICATES THAT A GLW IS NOT NEEDED
ATTM.
WINDS AND SEAS WILL DECREASE BY LATE WEEK AS STRONG HIGH PRESSURE
BUILDS EASTWARD OVER THE WATERS. BY FRIDAY AFTN, AN AREA OF LOW PRES
IS EXPECTED TO EJECT OUT OF THE GLFMEX AND MOVE OFF THE SERN CONUS
CST. THE MAJORITY OF THE MDLS KEEP THE LOW WELL E OF THE NJ/DE CST,
BUT THE ECMWF CONTINUES TO BE A BIT FURTHER N AND W. DEPENDING ON
WHERE THIS LOW GOES, AS WELL AS ITS STRENGTH, THERE COULD BE SOME
WINDS AND PRECIP TO DEAL WITH SATURDAY NIGHT INTO SUNDAY, ESPECIALLY
OVER THE SRN WATERS.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 7 PM EST THURSDAY FOR ANZ430-431-
450>455.
&&
$$
SYNOPSIS...DELISI
NEAR TERM...DELISI
SHORT TERM...DELISI
LONG TERM...RPW
AVIATION...NIERENBERG
MARINE...NIERENBERG
