FXUS61 KPHI 072207
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
507 PM EST MON DEC 7 2009

.SYNOPSIS...
HIGH PRESSURE WILL DRIFT EAST INTO THE ATLANTIC ON TUESDAY. MEANWHILE,
A LARGE LOW PRESSURE SYSTEM IN THE PLAINS STATES WILL SPREAD A SHIELD
OF MIXED PRECIPITATION TO THE MID ATLANTIC REGION TUESDAY NIGHT, AND
PRECIPITATION WILL CONTINUE INTO WEDNESDAY. THE PRECIPITATION WILL BE
A MIXTURE OF RAIN, SLEET, SNOW AND PERHAPS SOME FREEZING RAIN ON
TUESDAY NIGHT AND WILL CHANGE OVER TO ALL RAIN WEDNESDAY AND IT WILL
BE HEAVY AT TIMES. THE SYSTEM WILL BLOW THROUGH ON WEDNESDAY NIGHT 
WITH COLD GUSTY WINDS INVADING THE REGION. 

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
THICK DECK OF SC AT 3,000 FT AND ALTO CU TOPPING OFF AT 16,000 FT
IS MOIST ENOUGH TO DEPOSIT SOME FINE GRAINS OF SLEET ACROSS NEW
JERSEY. A WEST TO EAST VORT MAX IS MOVING THROUGH. 

SNOW REMAINS IN AREAS TO THE NORTH AND WEST OF THE DELAWARE VALLEY
AND WE'RE LOOKING AT MORE OVER THE NEXT TWO DAYS. IT'S A CHILLY ONE
OUT THERE AND THE DEW POINTS ARE IN THE TWENTIES MOST AREAS EXCEPT
OVER OUR DELMARVA ZONES WHERE THE TEMPERATURES AND DEWPOINTS
BENEFITTED FROM THE COMPARATIVELY WARM CHESAPEAKE BAY. 80H WINDS
WILL USHER IN MORE COLD AIR ADVECTION TONIGHT AND SET THE STAGE
FOR WHAT IS ON THE WAY FOR TUESDAY NIGHT. BUT FIRST, OVERNIGHT
WILL BE MAINLY CLOUDY ACROSS THE NORTH AND SOME CLOUDS DOWN
ACROSS OUR SOUTHERN AREAS. TEMPERATURES DOWN TO 20 UP NORTH AND
MAYBE LOW 30S ON THE EASTERN SHORE. THE COLD AIR IS NOT ONLY
DROPPING SLOWLY DOWN THE APPALACHIANS INTO VIRGINIA BUT SURGING
DOWN THE FRONT RANGE OF THE ROCKIES TO REMIND US THAT IT IS GOING
TO GET COLD LONG BEFORE THE ASTRONOMICAL WINTER GETS HERE.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
THE NOSE OF THE SURFACE HIGH WILL BE INTO THE WESTERN ATLANTIC AND
EXTEND NORTHWEST TO THE GREAT LAKES. A HEALTHY SOUTHWEST WIND ALOFT
WILL BRING OVERRUNNING PRECIPITATION TO THE REGION WITH PLENTY OF
MOISTURE TAPING INTO THIS SYSTEM BEFORE IT IS ALL SAID AND DONE.
BUT THE DONE PART SHOULD BE RAIN HEAVY AT TIMES AND NOT SNOW HEAVY
AT TIMES FOR US. WE HAVE BEEN DEALING WITH THE SPLIT FLOWS AND
THIS IS ANOTHER CASE AS THE SOUTHERN BRANCH REACHES DEEP INTO THE
MOISTURE SOURCE OF THE GULF OF MEXICO AND CARRIES IT NORTHEAST INTO
OUR WESTERN ZONES BEFORE DARK ON TUESDAY. THE EARLIEST HYDROMETERS
SHOULD BE IN THE FORM OF RAIN CREEPING UP FROM SOUTHERN DELAWARE
AND OUR MARYLAND EASTERN SHORE ZONE OF TALBOT. THAT WOULD BE
AROUND 4PM TUESDAY. THEN THE OVERRUNNING RUNS WILD AND QUICKLY
OVERSPREAD THE ENTIRE FORECAST AREA BY SEVEN. THIS WILL BE JUST
PAST THE EVENING RUSH HOUR BUT THERE WILL PROBABLY BE SOME
PRECIPITATION IN A LITTLE EARLIER AND THAT COULD BE A MINOR MESS
FOR COMMUTERS. WHILE TEMPERATURES WILL BE IN THE LOW TO MID 30S IN
THE NORTHWEST SUBURBS, THE WILL BE IN THE MID 30S ACROSS THE
DELAWARE AND SOUTH WHICH LOOKS LIKE AN ALL RAIN EVENT. HOWEVER,
YOU DON'T WANT TO GET TOO CUTE WITH DEMARCATION LINES THIS FAR OUT
SO BE PREPARED INTO THE EVENT THE TEMPERATURES STUMBLE ON
THEIR WAY TO SAFELY REACHING THE MID TO UPPER 30S. AS WE GET INTO
THE OVERNIGHT HOURS, THE LINE BETWEEN ALL LIQUID AND MIXED RAIN
SNOW AND SLEET WILL VERY SLOWLY LIFT NORTHWEST AWAY FROM THE
DELAWARE VALLEY AS THE WARM AIR BEGINS TO SEEP INTO THE LOWER
LEVELS. ONE CONCERN WILL BE THE AMOUNT OF FREEZING RAIN THAT COULD
OCCUR IF THE COLD AIR LINGER WITH THE STRONG SOUTHEAST WARM JET. HOWEVER
WE ARE LOOKING AT ABOUT A TEN TO TWELVE HOUR OF MIXED PRECIPITATION
AND IT WILL BE A MESS IN THE NORTHWESTERN SUBURBS UP THROUGH THE
POCONOS WHERE ALL SNOW WILL FALL.

THE MODELS ARE CONSISTENT WITH THE SECONDARY SMALL LOW FORMING
OVER THE CHESAPEAKE BAY BY WEDNESDAY 12Z. THE RAPID WARM-UP WITH
THE 80H 60 KT JET WILL HOPEFULLY SCOUR OUT THE COLD AIR IN ALL BUT
THE MOST STUBBORN VALLEYS OVER LEIGH AND POCONOS TO PREVENT A
DANGEROUS EPISODE OF FREEZING RAIN. 

TEMPERATURES THROUGH THIS PERIOD ARE NOT HARSH, BUT FOLLOWING THE
SYSTEMS PUSH INTO THE ATLANTIC AND A COLD RETURN FLOW...TEMPERATURES
REALLY BOTTOM OUT BUT THAT WILL BE COVERED IN OUR LONG TERM
SECTION.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
HIGH PRESSURE WILL CONTINUE TO BUILD IN FROM THE WEST THURSDAY NIGHT 
AND WILL LAST THROUGH THE EARLY PART OF THE WEEKEND.

ANOTHER SYSTEM LOOKS TO DEVELOP OFF OF THE CAROLINA COAST LATE IN 
THE WEEK AND MOVE NORTHEASTWARD ON SATURDAY. PRECIPITATION CHANCES 
LOOK GREATEST IN THE SOUTHERN AND COASTAL AREAS AS THE SYSTEM 
REMAINS OFFSHORE. WITH TEMPERATURES FALLING INTO THE 20S AND 30S
ON SATURDAY NIGHT/SUNDAY MORNING, PRECIPITATION MAY BEGIN AS SNOW
BEFORE MIXING WITH RAIN ON SUNDAY MORNING. ALSO, A LOW WELL OFF TO
OUR NORTH MAY DRAG A COLD FRONT ACROSS THE REGION ON SUNDAY. THE
FRONT DOES NOT LOOK TO HAVE AS MUCH OF AN IMPACT AS THE COASTAL
LOW AT THIS TIME BUT UNCERTAINTY WITHIN THIS PERIOD REMAINS HIGH.
A RETURN TO HIGH PRESSURE IS THEN EXPECTED FOR THE START OF THE
WEEK.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, 
KMIV, KACY AND SURROUNDING AREAS.

VFR FLYING WEATHER IS EXPECTED AT THE TERMINALS TONIGHT AND TUESDAY 
MORNING. A WEAK DISTURBANCE IS MOVING BY TO THE NORTH AND IT HAS 
CREATED A WEALTH OF MID AND HIGH LEVEL CLOUDINESS ACROSS MUCH OF THE 
REGION. LIMITED LOW LEVEL SC IS TO THE WEST OF THE DELAWARE VALLEY 
EARLY THIS AFTERNOON WITH A TEMPO GROUP FOR SOME SC ACROSS KABE AND 
KRDG OVER THE NEXT FEW HOURS. A COLD FRONT WILL CROSS THE AREA THIS 
EVENING AND MUCH OF THE MID LEVEL CLOUDS WILL MOVE AWAY AFTER THIS. 
WINDS WHICH WILL BE SOUTHWEST THIS AFTERNOON AND EARLY EVENING WILL 
VEER TO NW OVERNIGHT. VFR TUE MORNING WITH SCT-BKN HI CLOUDS. 

OUTLOOK...
THE HIGH PRESSURE SYSTEM WILL MOVE ACROSS OUR AREA TUESDAY AND
SLIDE OFF TO OUR EAST EARLY TUESDAY NIGHT. AS THE HIGH MOVES OFF,
A STRONG LOW PRESSURE SYSTEM WILL MOVE IN FROM THE SOUTHWEST AND
WEST LATE TUESDAY NIGHT AND WEDNESDAY. THE MAIN STORM CENTER IS
FORECAST TO MOVE NORTHEAST ACROSS THE GREAT LAKES WITH A WEAK
SECONDARY LOW CROSSING OUR AREA WEDNESDAY. RAIN AND WINDY CONDITIONS
WILL ACCOMPANY THIS SYSTEM WITH REDUCED CIGS AND VSBYS. SOME SNOW
OR MIXED PRECIPITATION COULD OCCUR IN OUR NORTHERN AREAS AT THE
ONSET TUESDAY NIGHT. THE RAIN WILL END AND CONDITIONS WILL BEGIN
TO IMPROVE WEDNESDAY NIGHT AS THE LOWS MOVE OFF TO THE NORTH AND
NORTHEAST. HIGH PRESSURE PUSHING IN FROM THE WEST WILL BRING
FAIR WEATHER WITH VFR CONDITIONS THURSDAY THROUGH FRIDAY.

&&

.MARINE...
WEAK LOW PRESSURE WILL PASS TO THE EAST OF THE WATER TONIGHT WHILE 
HIGH PRESSURE BUILDS IN FROM THE OHIO VALLEY. THE SOUTHWEST WINDS 
OVER THE WATERS THIS AFTERNOON WILL VEER TO WEST THIS EVENING AND 
THEN GO TO NORTHWEST TONIGHT. WINDS SPEEDS MAY INCREASE A LITTLE BUT 
NO FLAG WILL BE NEEDED FOR WIND OR SEAS TONIGHT OR TUESDAY. 

DEEP LOW PRESSURE WILL ADVANCE TO THE WEST DURING THE MID-WEEK 
PERIOD WHILE A SECONDARY SFC LOW WILL MOVE TOWARD OUR WATERS FOR 
WED. AN INCREASE IN WINDS AND SEAS TUE NIGHT WILL LIKELY BRING AT 
LEAST SCA CONDITIONS THEN WHICH SHOULD LAST INTO WED NIGHT (AT 
LEAST). WE WILL ISSUE THE SCA FLAG FOR THIS 3RD AND 4TH PERIOD EVENT 
NOW SINCE CONFIDENCE OF IT OCCURRING IS FAIRLY HIGH. MODEL SOUNDINGS 
INDICATE THE POSSIBILITY OF LOW END GALES AT THE BEGINNING OT THE 
4TH PERIOD. I WILL NOT ISSUE A GALE WATCH AT THIS POINT. A BETTER 
CHC FOR GALES WILL ARRIVE BEHIND THE DEPARTING LOW WED NGT INTO THU. 
ENHANCED WIND AND WAVES LOOK TO CONTINUE INTO THE EARLY PART OF THE 
WEEKEND. HIGH PRESSURE WILL BUILD IN SAT...BUT ANOTHER LOW COULD 
MOVE TOWARD THE WATERS FOR SUNDAY.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 11 PM TUESDAY TO 6 PM EST WEDNESDAY 
     FOR ANZ430-431-450>455.

&&

$$
SYNOPSIS...EBERWINE/DELISI
NEAR TERM...EBERWINE
SHORT TERM...EBERWINE
LONG TERM...MEOLA
AVIATION...O'HARA
MARINE...O'HARA