FXUS61 KPHI 031351
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
851 AM EST THU DEC 3 2009

.SYNOPSIS...
HIGH PRESSURE SETTLING INTO THE CENTRAL AND SOUTHERN PLAINS
WILL GRADUALLY BUILD EASTWARD INTO OUR AREA. AS ENERGY MOVES
ACROSS THE GULF OF MEXICO, ANOTHER LOW PRESSURE SYSTEM IS FORECAST
TO DEVELOP AND TRACK NORTHEASTWARD. THE TRACK OF THIS SYSTEM IS A
LITTLE UNCERTAIN, HOWEVER AT LEAST SOME PRECIPITATION LOOKS TO
OVERSPREAD THE AREA SATURDAY AND SATURDAY NIGHT. HIGH PRESSURE
WILL THEN BUILD IN SUNDAY AND GRADUALLY SLIDE EASTWARD THROUGH
EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE SHOWERS AND EARLY MORNING CONVECTION HAVE MOVED COMPLETELY OUT
OF THE REGION. COOLER DRIER AIR HAS BEGUN TO SEEP INTO THE CWA
BEHIND THE COLD FRONT PASSAGE. SOME LOCALES HAVE DROPPED 5 TO 6
DEGREES IN THE PAST 3 HOURS BUT FEELING IS THAT THIS TREND WILL
NOT CONTINUE INTO THE AFTERNOON HOURS. ALTHOUGH THE EARLY DECEMBER
SUN ANGLE IS VERY WEAK, THERE WILL STILL BE PLENTY OF SUNSHINE
UNDER CLEAR SKIES TODAY AND WE MAY BE ABLE TO WARM A COUPLE OF
DEGREES FROM WHERE WE STAND NOW. 

WESTERLY WINDS WILL KICK IN OVER THE NEXT FEW HOURS AND WILL
REMAIN GUSTY AT TIMES AS MIXING CONTINUES THROUGHOUT THE EARLY
AFTERNOON HOURS. A FEW AREAS OF STRATOCUMULUS MAY POP UP THIS
AFTERNOON BUT LOOKING AT THE AVAILABLE MOISTURE, THEY WILL REMAIN
SCATTERED AT BEST.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
THE STRONG AREA OF LOW PRESSURE WILL BE QUICKLY MOVING THROUGH THE 
CANADIAN MARITIMES TONIGHT. THE CYCLONIC LOW-LEVEL FLOW WILL 
GRADUALLY WEAKEN AS THE PRESSURE GRADIENT RELAXES. THE UPPER-LEVEL 
PATTERN THEN LOOKS TO RELOAD AS A SOUTHWEST FLOW ALOFT IS EXPECTED 
TO CONTINUE TONIGHT THROUGH FRIDAY AS ENERGY DROPS SOUTHEASTWARD 
ACROSS THE CENTRAL AND SOUTHERN PLAINS. THIS ENERGY WILL ENERGIZE A 
BAROCLINIC ZONE FROM THE GULF OF MEXICO TO OFF THE SOUTHEASTERN 
UNITED STATES COAST. MEANWHILE, THE CORE OF THE UPPER-LEVEL TROUGH 
WILL BE NEAR HUDSON BAY AND TRYING TO SETTLE SOUTHWARD SOME. 

DRIER AIR WILL CONTINUE TO SETTLE INTO OUR AREA TONIGHT WITH ANY 
LINGERING CLOUDS ON THE DECREASE. GIVEN THE SOUTHWESTERLY FLOW ALOFT 
HOWEVER, WE MAY KEEP SOME HIGH LEVEL CLOUDINESS. THE CENTER OF 
HIGH PRESSURE IN THE CENTRAL/SOUTHERN PLAINS FRIDAY WILL BUILD 
EASTWARD TO THE MID ATLANTIC. THIS SURFACE HIGH WILL THEN TEND TO 
TRANSLATE NORTHEASTWARD AS THE UPPER-LEVEL TROUGH AMPLIFIES SOME 
ACROSS THE OHIO AND TENNESSEE VALLEYS. THERE APPEARS TO BE PLENTY OF 
MOISTURE CONVERGENCE NEAR THE GULF COAST STATES AS THE BAROCLINIC 
ZONE BECOMES ACTIVE AND AS A SURFACE LOW DEVELOPS. THE TRAJECTORY OF 
THE MID TO UPPER-LEVEL WINDS WILL TEND TO PULL AT LEAST HIGH LEVEL 
MOISTURE OUR WAY DURING FRIDAY. AS A RESULT, WE WILL BEGIN TO SEE AN 
INCREASE IN CLOUDS, ESPECIALLY LATER IN THE DAY AND AT NIGHT. THINGS 
THEN BEGIN TO TURN MORE INTERESTING.

DURING THE PAST FEW DAYS, THE MODEL GUIDANCE HAS BEEN SHOWING SHORT 
WAVE ENERGY DROPPING SOUTHEASTWARD AND ENERGIZING A BAROCLINIC ZONE 
FROM NEAR THE GULF COAST AREA TO THE SOUTHEASTERN UNITED STATES 
COAST. A SURFACE LOW IS FORECAST TO DEVELOP ALONG THIS BOUNDARY AND 
THEN WAS SHUNTED NORTHEASTWARD AND WELL TO OUR EAST, PLACING OUR 
AREA ON THE WESTERN FRINGE OF THE PRECIPITATION SHIELD. THE MODEL 
GUIDANCE APPEARS TO BE SHOWING MORE SHARPENING OF THE UPPER-LEVEL 
TROUGH FROM THE OHIO AND TENNESSEE VALLEYS. THIS TENDS TO PULL THE 
SURFACE LOW TRACK A BIT FARTHER TO THE WEST, ALLOWING THE 
PRECIPITATION SHIELD ALSO TO BE PULLED BACK WESTWARD. THE GFS, 
NAM/WRF AND UKMET DO SHOW THIS MORE SHARPENING OCCURRING, ALTHOUGH 
THE SURFACE LOW ATTM IS NOT FORECAST TO REALLY RAMP UP AS IT TRACKS 
EAST OF OUR REGION. THIS WOULD LIMIT THE WAA FROM ARRIVING INTO OUR 
AREA FROM THE EAST, AND THE FORECAST SOUNDING INDICATE A MORE 
NORTHERLY WIND COMPONENT TO THE WIND. THE ECMWF ALSO APPEARS A BIT 
SHARPER WITH THE UPPER-LEVEL TROUGH. INTERESTING TO NOTE THAT THE 
WEDNESDAY GFS ENSEMBLES ARE MORE OFFSHORE ALTHOUGH THERE ARE SOME 
MEMBERS THAT ARE A CLOSE CALL. THE FORECAST SOUNDINGS AND ALSO THE 
MODEL PLAN VIEWS OF THE THERMAL FIELDS INDICATE THAT PERHAPS 
BOUNDARY LAYER TEMPERATURES MAY NOT BE A PROBLEM IN MANY AREAS, 
REGARDING FROZEN PRECIPITATION FALLING. THE TIMING OF THIS SYSTEM
ALSO HAS SLOWED SOME PROBABLY DUE TO THE FACT THAT THE TROUGH IS A 
BIT SHARPER NOW. THIS WOULD PLACE THE BULK OF THE PRECIPITATION 
OCCURRING LATER SATURDAY AND SATURDAY NIGHT. THE FORECAST SOUNDINGS 
DO SHOW LITTLE EVAPORATIONAL COOLING TAKING PLACE INITIALLY, AND 
PERHAPS THE LOW-LEVEL TEMPERATURES MAY BE A BIT COLD GIVEN CLOUDS ON 
THE INCREASE FRIDAY NIGHT. IF THE CLOUDS HOLD OFF AND WE CAN GET 
DECENT RADIATIONAL COOLING FOR AWHILE FRIDAY NIGHT, THEN THE CLOUDS 
ROLL IN, THAT LOW-LEVEL COLDER AIR PERHAPS CAN GET TRAPPED. AN 
EXAMINATION OF THE SURFACE THERMAL FIELDS OF THE GFS AND NAM/WRF, DO 
INDICATE COLD ENOUGH TEMPERATURES TO SUPPORT SNOW ALTHOUGH STILL 
THINK SOME RAIN WILL EITHER START OR MIX IN ESPECIALLY CLOSER TO THE 
COAST. GIVEN THE TRACK OF THE STORM, WE WILL STAY CLOSE TO 
CONTINUITY WITH MOSTLY SLIGHT CHC POPS ACROSS THE FAR NORTHWEST AND 
CHC SOUTHEASTWARD. WE DID EDGE UP THE POPS SOME ACROSS THE EASTERN 
AND SOUTHERN AREAS BUT KEPT THEM NO HIGHER THAN CHC ATTM. WE ALSO 
CHANGED THE SNOW/RAIN SHOWER WORDING TO SNOW AND/OR RAIN GIVEN THE 
FORECAST PRECIPITATION SHIELD. IF SNOW DOES OCCUR, ACCUMULATIONS 
COULD BE TOUGHER AS SURFACE TEMPERATURES MAY BE AT OR ABOVE FREEZING 
DURING THE DURATION AND INTENSITY COULD BE ON THE LIGHT SIDE. 
ALTHOUGH THIS COULD CHANGE ESPECIALLY IF A SLOWER ARRIVAL OF THE 
PRECIPITATION OCCURS AND IT FALLS MOSTLY AT NIGHT. STAY TUNED. WE 
WILL ADD A MENTION IN THE HAZARDOUS WEATHER OUTLOOK TO ALLOW FOR 
MORE ADVERTISEMENT OF THIS POTENTIAL STORM.

AS FOR TEMPERATURES, WE MOSTLY UTILIZED AN EVENLY WEIGHTED BLEND OF 
THE GFS AND NAM MOS. HOWEVER, DID LEAN CLOSER TO THE COOLER NAM MOS 
FOR SATURDAY GIVEN THE INCREASED CLOUDS AND NORTHERLY FLOW.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
THIS TIME FRAME BEGINS WITH THE GRADUAL DEPARTURE OF THE LOW 
PRESSURE SYSTEM FROM THE SHORT TERM WELL OFFSHORE AND THE ARRIVAL OF 
SURFACE HIGH PRESSURE. THIS HIGH WILL DOMINATE OUR WEATHER SUNDAY, 
THEN GRADUALLY SHIFT EASTWARD MONDAY INTO TUESDAY. AS UPPER-LEVEL 
TROUGHING AMPLIFIES INTO THE EAST WEDNESDAY, A SURFACE LOW IS 
FORECAST TO DIVE SOUTHEASTWARD WITH A WARM FRONT TO OUR SOUTH. WE 
WILL HAVE TO SEE IF THIS TROUGH CAN SHARPEN UP AND ALLOW THE SURFACE 
LOW TO DEVELOP FURTHER SOUTH AND POTENTIALLY TURN UP THE COAST.

WITH THE COOLER/COLDER AIR, SNOW AND/OR RAIN IS FORECAST ACROSS THE 
CWA SATURDAY NIGHT AS THE SYSTEM PULLS AWAY FROM THE AREA. THEN 
PERHAPS SOME MIXED PRECIPITATION WITH THE TUESDAY NIGHT/WEDNESDAY 
SYSTEM. WE CHANGED THE SNOW/RAIN SHOWERS WORDING SATURDAY NIGHT TO 
SNOW/RAIN WORDING TO MESH WITH THE END OF THE SHORT TERM TIME FRAME. 
OTHERWISE, NO SIGNIFICANT CHANGES WERE MADE, ALTHOUGH WE BLENDED IN 
A SMALL PERCENTAGE OF THE 00Z MOSGUIDE FOR SOME FIELDS TO INTRODUCE 
SOME NEWER GUIDANCE INTO THE FORECAST.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, 
KMIV, KACY AND SURROUNDING AREAS.

SKIES HAVE CLEARED IN MOST AREAS BY 13Z. SOME AREAS STILL HAD 
SCATTERED STRATOCU AND AS COLD AIR ARRIVES FROM THE WEST THIS 
AFTERNOON, THE CLOUDS MAY GO BKN AT TIMES AT RDG/ABE.

WINDS HAVE ALSO COME DOWN QUITE A BIT FROM LAST NIGHT. ALTHOUGH WE 
WERE IN A TRANQUIL PERIOD THIS MORNING, GUSTY WINDS ARE FORECAST TO 
REDEVELOP THIS AFTERNOON WITH POSSIBLE GUSTS TO 30 KT.

FOR TONIGHT THE SKY IS FORECAST TO BECOME CLEAR AND THE WEST WIND 
SHOULD DIMINISH TO LESS THAN 10 KNOTS.

OUTLOOK...
DRY WEATHER IS EXPECTED FOR FRIDAY AND FRIDAY NIGHT. LOW PRESSURE 
OFF THE COAST MAY BRING SOME RAIN AND SNOW TO OUR REGION FROM 
SATURDAY INTO SATURDAY NIGHT. DRY WEATHER SHOULD RETURN FOR SUNDAY 
AND MONDAY.

&&

.MARINE...
GALES HAVE BEEN REPLACED BY SCA ON ALL WATERS AS WINDS HAVE
DROPPED BELOW GALE FORCE EVEN IN GUSTS. HOWEVER, GUST WINDS UP TO
30 KT WILL STILL OCCUR INTO THE EVENING DUE TO COLD AIR RETURNING
FROM THE WEST.

TONIGHT...WINDS WILL CONTINUE TO DECREASE AS WE LOSE ANY WINDS ALOFT 
THAT COULD MIX DOWN TO THE WATERS AND SPEEDS SHOULD BE BELOW 25 KT 
BY MIDNIGHT.

OTHERWISE...HIGH PRESSURE IS FORECAST TO NOSE IN FROM THE WEST FOR 
FRIDAY AND FRIDAY NIGHT, BRINGING A BRIEF PERIOD OF RELATIVELY 
TRANQUIL CONDITIONS.

LOW PRESSURE IS EXPECTED TO DEVELOP OFF THE SOUTHEAST COAST ON 
FRIDAY NIGHT AND SATURDAY. THE LOW SHOULD MOVE TO THE NORTHEAST, 
PASSING WELL TO THE EAST OF DELAWARE AND NEW JERSEY ON SATURDAY 
NIGHT OR SUNDAY MORNING. SMALL CRAFT ADVISORY CONDITIONS ARE LIKELY 
OVER THE WEEKEND.

&&

.TIDES/COASTAL FLOODING...
THE COASTAL FLOOD ADVISORY HAS BEEN DISCONTINUED FOR THE COAST AND
DELAWARE BAY AREAS. HOWEVER, A COASTAL FLOOD ADVISORY HAS BEEN
ISSUED FOR THE LOWER DELAWARE RIVER THAT IS TIDAL. SOME OF THE
PUSH OF WATER FROM THE SOUTH HAS MOVED NORTHWARD INTO THE TIDAL
PARTS OF THE DELAWARE RIVER AND THIS SHOULD CAUSE MINOR FLOODING
AROUND HIGH TIDE LATE THIS MORNING AND EARLY THIS AFTERNOON.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...COASTAL FLOOD ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR 
     PAZ070-071.
NJ...COASTAL FLOOD ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR 
     NJZ016>018.
DE...COASTAL FLOOD ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR 
     DEZ001.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 10 PM EST THIS EVENING FOR ANZ430-
     431-450>455.

&&

$$
SYNOPSIS...GORSE
NEAR TERM...GORSE/HEAVENER
SHORT TERM...GORSE
LONG TERM...GORSE/KRUZDLO
AVIATION...IOVINO/STAUBER
MARINE...IOVINO/STAUBER
TIDES/COASTAL FLOODING...