FXUS61 KPHI 142033
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
333 PM EST MON DEC 14 2009

.SYNOPSIS...
WEAK HIGH PRESSURE WILL DRIFT OFF THE COAST THIS EVENING. THIS WILL 
ALLOW LOW PRESSURE OVER THE GREAT LAKES TO MOVE INTO SOUTHERN 
QUEBEC. AS THE LOW TRACKS INTO SOUTHERN CANADA TOMORROW, IT WILL 
PULL A COLD FRONT THROUGH THE NORTHERN MID-ATLANTIC REGION. THE COLD 
FRONT WILL USHER IN SOME BREEZY CONDITIONS TUESDAY NIGHT AND 
WEDNESDAY AS WELL AS SOME COLD CANADIAN AIR.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
THE MID AND HIGH LEVEL CLOUDS OVER THE REGION THIS AFTERNOON WILL 
GRADUALLY LOWER TONIGHT WITH THE APPROACH OF A COLD FRONT. THE 
SOUTHERLY FLOW AT THE SURFACE, THE EVENING WARM ADVECTION AT H8, AND 
THE CLOUD COVER WILL ALL CONSPIRE TO KEEP TEMPERATURES ABOVE THE 
FREEZING MARK TONIGHT ACROSS THE CWA.

OVERALL UPSTREAM MOISTURE IS QUITE SHALLOW. VORTICITY IS PROGGED TO 
TRACK WELL NORTH OF THE REGION IN THE BROAD MID-LEVEL TROF. THE
SURFACE FRONT IS WEAK. CERTAINLY NOT INGREDIENTS FOR SOMETHING
BIG. THE STAT GUIDANCE ISN'T EXCITED EITHER.

WITH ALL THIS SAID, JUST SOME 20 POPS WERE THROWN INTO THE GRIDS 
ACROSS THE NORTHERN THIRD OF THE CWA FROM 05Z TONIGHT AND INTO THE 
SHORT TERM PERIOD (14Z TOMORROW).     

I HAVE EVERYTHING AS LIQUID AND LIGHT. THE SOUNDINGS CERTAINLY 
SUPPORT THIS. BUT I GUESS IF THERE IS A CONCERN WITH TONIGHT'S 
FORECAST, IT WOULD BE ACROSS THOSE SHELTERED MOUNTAIN VALLEYS IN THE 
POCONOS AND NORTHWEST JERSEY THAT FALL BELOW THE GIVEN TEMPERATURES 
AND EXPERIENCE SOME VERY LIGHT ICING. I'M NOT HEADING THIS WAY AT 
THE MOMENT. NO STATEMENTS ARE FORTHCOMING. I SUPPOSE IT'S MORE OF A 
WHAT IF SCENARIO.      

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
AS MENTIONED ABOVE, I END THE LIGHT, ALL LIQUID PRECIPITATION AT 14Z. 
THE FORECAST THEN REMAINS DRY UNTIL LATE TUESDAY NIGHT WHEN SNOW
SHOWERS ARE INTRODUCED. I HAVE THE SNOW SHOWERS GOING THROUGH
MIDDAY WEDNESDAY. IT LOOKS DRY THROUGH THE REST OF THE PERIOD.

HIGH TEMPERATURES TOMORROW WILL CLIMB ABOVE TODAY'S HIGH. IT WILL 
ONLY BE A ONE DAY WARM UP AS HIGH TEMPERATURES ON WEDNESDAY WILL 
HAVE A TOUGH TIME CLIMBING OUT OF THE 30S. IT APPEARS IT WILL BE A
FEW DEGREES COLDER ON THURSDAY. OVERNIGHT LOWS WILL BE IN THE 20S
AND 30S WEDNESDAY MORNING AND IN THE TEENS AND 20S COME THURSDAY
MORNING.

THE SOUTH WINDS WE SEE TONIGHT WILL BECOME WEST TOMORROW AND 
NORTHWEST TOMORROW NIGHT. THESE NORTHWEST WINDS AND THE COLD AIR 
ADVECTION THEY'LL RIDE IN WITH WILL BECOME GUSTY TOMORROW EVENING 
AND WILL PERSIST INTO WEDNESDAY.    

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
THE STRONG UPPER LOW TO OUR NORTH IS FORECAST TO RETROGRADE THROUGH
THE WEEKEND KEEPING US IN A COLD PATTERN. FAIR WEATHER WILL PREVAIL
THURSDAY NIGHT INTO SATURDAY AS SURFACE HIGH PRESSURE MOVES ACROSS. 
A LOBE OF VORTICITY IS THEN FORECAST TO ROTATE AROUND THE UPPER LOW.
THIS WILL CAUSE A COASTAL LOW TO FORM ALONG THE SOUTH ATLANTIC COAST.
THIS LOW IS THEN EXPECTED TO MOVE NORTHEAST WELL OFF THE COAST.
NEVER THE LESS, IT MAY GET CLOSE ENOUGH TO SPREAD SOME RAIN OR
SNOW INTO OUR SOUTHERN COASTAL AREAS LATE SATURDAY NIGHT INTO
SUNDAY NIGHT. MEANWHILE, THE UPPER TROUGH WILL BE DROPPING DOWN
ACROSS OUR AREA. THIS WILL ALSO BRING THE CHANCE FOR SOME
PRECIPITATION FOR THE SAME TIME PERIOD. ONCE THE UPPER TROUGH
MOVES OFF TO THE EAST, ANOTHER BATCH OF COLD ARCTIC AIR WILL RUSH
INTO OUR AREA LATER SUNDAY NIGHT INTO MONDAY. 

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
STRATOCUMULUS CLOUDS AROUND THE KPHL AREA AT 12Z RETREATED NORTHWARD 
DURING THE MORNING, AND ONLY CIRRUS...THIN AT TIMES...WAS OVER THE 
AREA THIS AFTERNOON AS A WEAK RIDGE OF HIGH PRESSURE WAS CRESTING 
ALONG THE COAST. HOWEVER, MODEL GUIDANCE IS UNIFORM IN SHOWING A LOW 
MOVING NORTH OF OUR AREA TONIGHT AND TUESDAY MORNING. A TRAILING 
COLD FRONT WILL PASS THROUGH THE TAF SITES TUESDAY MORNING, PROBABLY 
SHORTLY AFTER SUNRISE. LOW LEVEL MOISTURE, POOLING IN THE WEAK 
UPWARD VERTICAL MOTION AHEAD OF AND ALONG THE FRONT, IS EXPECTED TO 
FORM INTO MARGINAL VFR STRATUS EARLY TONIGHT, AND PROBABLY LOWER TO 
IFR CEILINGS OVERNIGHT. THERE COULD ALSO BE SOME LIGHT FOG; AT THIS 
POINT, THE STRATUS WAS BEEFED UP MORE SO THAN THE FOG FROM THE 
PREVIOUS FORECAST. MODELS SHOW LITTLE OR NO PRECIPITATION OCCURRING 
WITH THIS SYSTEM. 

THEN, CONDITIONS ARE FORECAST TO IMPROVE TO BROKEN MARGINAL VFR TO 
VFR STRATOCUMULUS LATER TUESDAY MORNING. WINDS ARE EXPECTED TO VEER 
FROM LIGHT SOUTH TONIGHT AND SOUTHWEST (JUST AHEAD OF THE FRONT) 
EARLY TUESDAY MORNING TO WEST LATER TUESDAY MORNING, AND THEN TO 
WEST-NORTHWEST TUESDAY AFTERNOON WITH A GUSTY CHARACTER.

OUTLOOK...
GENERALLY VFR CONDITIONS ARE FORECAST FOR MUCH OF THE REST OF THIS 
WEEK.

&&

.MARINE...
BENIGN CONDITIONS ARE FORECAST TONIGHT AND EARLY TUESDAY AHEAD OF 
THE APPROACHING WEAK COLD FRONT, SCHEDULED TO MOVE THROUGH DURING 
TUESDAY. AFTER THE FRONT MOVES BY, THE GRADIENT TIGHTENS BY TUESDAY 
EVENING AS WINDS MIX DOWN IN THE POST-FRONTAL ENVIRONMENT FROM 800 
HPA OR SO. SMALL CRAFT ADVISORY CONDITIONS ARE FORECAST BEHIND THIS 
FRONT. IN FACT, 925 HPA WINDS FROM BOTH THE NAM AND THE GFS SHOW 35 
KNOT WINDS DURING TUESDAY NIGHT. HOWEVER, WAVEWATCH SEEMS RELUCTANT 
TO BUILD SEAS MUCH TO 5 FEET IN THE OFFSHORE FLOW. FOR NOW, THE 
ADVISORY WILL BE STARTED AT 00Z WEDNESDAY, OUR THIRD PERIOD, AND 
CONTINUED THROUGH 22Z WEDNESDAY (OUR FOURTH PERIOD). THE ADVISORY 
MAY NEED TO BE EXTENDED BEYOND THAT BY LATER FORECASTERS FOR 
WEDNESDAY NIGHT AND THURSDAY.

HIGH PRESSURE IS SEEN TO BUILD OVER THE AREA SLOWLY FROM THE WEST BY 
FRIDAY.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 7 PM TUESDAY TO 6 PM EST WEDNESDAY 
     FOR ANZ430-431-450>455.

&&

$$
SYNOPSIS...KRUZDLO
NEAR TERM...KRUZDLO
SHORT TERM...KRUZDLO
LONG TERM...RPW
AVIATION.../ 
MARINE.../