FXUS61 KPHI 262038
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
338 PM EST SAT DEC 26 2009

.SYNOPSIS...
HIGH PRESSURE OVER THE CANADIAN MARITIMES WILL MOVE SOUTHEAST 
OVERNIGHT AS LOW PRESSURE OVER THE SOUTHERN DELMARVA MOVES 
NORTHEAST. A COLD FRONT IS EXPECTED TO CROSS THE ARA SUNDAY NIGHT, 
WITH ANOTHER COLD FRONT EXPECTED MONDAY NIGHT. HIGH PRESSURE FROM 
THE MIDWEST WILL THEN BUILD OVER THE REGION TUESDAY, THEN MOVE TO 
THE COAST ON WEDNESDAY. LOW PRESSURE MAY DEVELOP ALONG THE SOUTHEAST 
COAST ON THURSDAY BEFORE MOVING NORTHEAST ON FRIDAY.
&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
EAST WINDS IN THE 15 TO 20 MPH RANGE AND GUSTS OVER 25 MPH WILL 
SLOWLY DECREASE DURING THE EVENING HOURS AS THE PRESSURE GRADIENT 
BETWEEN A LOW JUST TO OUR SOUTH AND HIGH PRESSURE OVER THE CANADIAN 
MARITIMES MOVES NORTHEAST. PRECIPITATION WITH THE LOW WILL ALSO END 
DURING THE EVENING AND OVERNIGHT HOURS, FROM SOUTH TO NORTH. 
RESIDUAL CLOUDINESS WILL TAKE A LITTLE LONGER TO EXIT STAGE RIGHT, 
BUT MAINLY CLEAR SKIES ARE EXPECTED BY DAWN. TEMPERATURES OVERNIGHT 
ARE EXPECTED TO REMAIN ABOVE FREEZING IN SOUTHEAST PA/CENTRAL NEW 
JERSEY AND ALL POINTS FURTHER SOUTH, WITH SUB-FREEZING TEMPERATURES 
EXPECTED IN NORTHERN THIRD OF NEW JERSEY, THE LEHIGH VALLEY, 
SOUTHERN POCONOS AND BERKS COUNTY, AND WATER COULD FREEZE OVER ON 
ROADWAYS IN THESE AREAS.
&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
SUNDAY LOOKS LIKE A DECENT DAY WITH ABOVE NORMAL TEMPERATURES AND 
MAINLY SUNNY SKIES. THEN A COLD FRONT WILL CROSS THE REGION LATE 
SUNDAY NIGHT, BRINGING WITH IT THE SOME LIGHT SNOW IN THE NORTH, 
RAIN CHANGING TO LIGHT SNOW IN THE PHL METRO AREA, AND LIGHT RAIN TO 
THE SOUTH. PRECIP TOTALS ARE NOT IMPRESSIVE WITH THIS SYSTEM, BUT 
THERE COULD BE ENOUGH MOISTURE AROUND TO MAKE THE MONDAY MORNING 
COMMUTE A LITTLE TRICKY IN THE NORTH.  ANOTHER FRONT IS EXPECTED TO 
CROSS THE REGION MONDAY NIGHT. TEMPERATURES WILL BE COLD ENOUGH WITH 
THIS SYSTEM TO PRODUCE ALL SNOW, BUT THERE WON'T BE MUCH MOISTURE, 
SO ANY SNOW THAT DOES FALL WILL ACCUMULATE LESS THAN ONE INCH. THEN 
COLD AND BLUSTERY, BUT DRY CONDITIONS ARE EXPECTED ON TUESDAY WITH 
HIGH TEMPERATURES MAINLY IN THE 30S, EXCEPT MID 20S IN THE POCONOS.
&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
A LARGE AREA OF HIGH PRESSURE WILL BE OVER THE EASTERN THIRD OF THE 
NATION EARLY IN THE EXTENDED PERIOD, SO EXPECT DRY AND COOL WX WITH 
TEMPS REMAINING AOB NORMAL.  THE HIGH PRESSURE SYSTEM SHIFTS EWD ON 
WEDNESDAY, THEN ALL EYES TURN TO A STORM SYSTEM WHICH IS FCST TO 
DEVELOP IN THE GLFMEX.

ONCE AGAIN, THERE ARE SIGNIFICANT MDL DIFFS WRT THE EXPECTED 
DEVELOPMENT.  THE GFS AND CMC DEVELOP A LOW AND THEN MOVE IT TO THE 
NC CST AND THEN BASICALLY MOVE IT ENEWD AND OUT TO SEA.  WITH LAST 
WEEKEND'S SNOWSTORM, THE GFS WAS CONSISTENTLY TOO FAR S AND E.  

MEANWHILE, THE ECMWF HAS BEEN MUCH FURTHER N AND W AND MUCH STRONGER 
WITH THIS SYSTEM.  IT IS ALSO IMPORTANT TO NOTE THAT THE ECMWF WAS 
SO FAR OUT IN FRONT OF LAST WEEK'S STORM, IT PRACTICALLY PUT THE 
OTHER MODELS TO SHAME.  THE ECMWF ALSO TENDS TO BE ONE OF THE MORE 
RELIABLE MDLS. WHEN I SEE ONLY ONE MODEL DOING SOMETHING AND ALL THE 
OTHERS ARE INDICATING SOMETHING ELSE, I OFTEN TEND TO WRITE THE ONE 
MODEL OFF AS AN OUTLIER.  HOWEVER, IT IS THE ECMWF WITH THE 
DIFFERING SOLN AND WITH ITS TRACK RECORD, I CAN NOT RULE IT OUT.  
WITH THAT SAID, IT HAS MADE A SIGNIFICANT NWWD SHIFT WITH ITS 12Z 
RUN. AS A RESULT, ITS CURRENT SOLN WOULD INDICATE A PREDOMINANTLY 
RAIN EVENT FOR THE AREA.  BUT OF COURSE, A RAPIDLY DEVELOPING LOW 
CLOSER TO THE COAST HAS THE POTENTIAL TO CREATE COASTAL PROBS AS 
WELL, ESPECIALLY SINCE THERE IS A FULL MOON ON DECEMBER 31.  IT ALSO 
HAS BEEN OBSERVED FOR MOST OF THE LAST FEW MONTHS, THAT ACTUAL LOW 
POSITIONS TEND TO BE FURTHER N AND W THEN WHERE THEY APPEAR IN THE 
EXTENDD, SO IF THAT TREND WERE TO CONTINUE, AN EVEN MORE WWD SOLN 
CAN NOT BE RULED OUT.

NEVERTHELESS, WITH THE STORM AT LEAST 4 TO 5 DAYS AWAY, IT IS 
ENTIRELY TOO EARLY TO KNOW ANY DETAILS WITH ANY DEGREE OF 
CERTAINTY.  THE POTENTIAL DOES EXIST FOR YET ANOTHER SIGNIFICANT 
COASTAL STORM.  HOWEVER, EXACTLY WHO GETS WHAT AND HOW MUCH IS FAR 
FROM CERTAIN AT THIS TIME AND MAY CONTINUE TO BE UNCERTAIN FOR EVEN 
A FEW MORE DAYS.   

NEEDLESS TO SAY, I DID NOT MAKE MANY CHANGES TO THE EXTENDD AS 
TEMPS, WINDS, POPS ETC WILL ULTIMATELY BE BASE ON WHERE THE 
DEVELOPING STORM IS AND ITS STRENGTH AT ANY GIVEN TIME.  ONCE AGAIN, 
STAY TUNED.
&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, 
KMIV, KACY AND SURROUNDING AREAS.

WIDESPREAD IFR CONDITIONS CONTINUE AT THE TAF SITES THIS AFTERNOON. 
THE SLOW MOVING LOW PRESSURE SYSTEM WILL MAINTAIN THESE LOW 
CONDITIONS THROUGH MUCH OF THE NIGHT WITH IMPROVEMENT TOWARDS 
DAYBREAK. LIGHT RAIN WILL TAPER OFF THIS EVENING...BUT A PERIOD OF 
DRIZZLE IS EXPECTED UNTIL AROUND MIDNIGHT. TEMPERATURES WILL REMAIN 
WARM ENOUGH FOR ALL LIQUID PRECIPITATION. WINDS WILL DECREASE FROM 
THE EAST OR SOUTHEAST THROUGH EARLY TONIGHT...THEN BECOME LIGHT AND 
VARIABLE FOR AWHILE...THEN BECOME WESTERLY LATE TONIGHT. VFR 
CONDITIONS EXPECTED AFTER DAYBREAK SUN AND THROUGH THE DAY. 

OUTLOOK...
A COLD FRONT AND UPPER DISTURBANCE WILL CROSS THE AREA MON. BRIEFLY 
LOWER CONDITIONS POSSIBLE IN ANY SHOWERS. GENERALLY FAIR WEATHER 
EXPECTED TUE-WED WITH DECENT WEST TO NORTHWEST WINDS. &&
&&

.MARINE...
THE SFC LOW IS MOVING SLUGGISHLY THIS AFTERNOON AND IT REMAINS SOUTH 
OF OUR WATERS. THE DECENT GRADIENT ACROSS THE NORTHERN COASTAL 
WATERS SHOULD PERSIST PAST THE ORIGINAL 4PM EXPIRATION TIME FOR THE 
GALE FLAG. I WILL EXTEND THE EXPIRATION TIME OUT TO 00Z FOR NOW. THE 
44025 AND 44066 BUOYS HAVE BEEN REPORTING G35 FOR SEVERAL HOURS NOW. 
ELSEWHERE...THE GRADIENT HAS DECREASED AS THE LOW NEARS AND A SCA 
FLAG WILL BE KEPT OVERNIGHT FOR NOW. THE WINDS ACROSS THE UPPER BAY 
SHOULD DECREASE EARLY TONIGHT...SO THE FLAG MAY BE DROPPED THERE 
WITH THE EVENING UPDATE. SEAS ACROSS THE OCEAN WILL PROBABLY REMAIN 
ABOVE 5 FT INTO SUN. 

A PERIOD OF FAIRLY QUIET WEATHER SUN NGT-MON. MORE SCA, OR GALE, 
CONDITIONS FOLLOWING A COLD FROPA MON AFTERNOON. 
&&

.TIDES/COASTAL FLOODING...
THE SLOW MOVING LOW PRESSURE SYSTEM HAS CAUSED TIDAL FLOODING
ALONG THE CHESAPEAKE BAY TODAY. THE SOUTHEAST TO EAST FLOW IS NOW
BEGINNING TO CAUSE HIGHER WATER LEVELS IN THE DELAWARE BAY. A
COASTAL FLOODING ADVISORY WILL BE ISSUED FOR THE DELAWARE BAY AND
RIVER. MINOR TIDAL FLOODING IS EXPECTED IN THESES AREAS TONIGHT.

THE CFW (ADVISORY) FOR THE CHESAPEAKE BAY WILL EXPIRE AT 5 PM. 
&&

.HYDROLOGY...
RAIN AND SNOWMELT ARE COMBINING TO PRODUCE SIGNIFICANT RISES ON
SMALL STREAMS...ESPECIALLY IN SOUTHEAST PA, NORTHERN DELAWARE AND
SOUTHERN NEW JERSEY. WARNINGS ARE BEING ISSUED WHERE NECESSARY. NO
FLOODING IS EXPECTED ON THE DELAWARE, SCHUYLKILL OR LEHIGH RIVERS.

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...COASTAL FLOOD ADVISORY UNTIL 11 PM EST THIS EVENING FOR PAZ070-
     071.
NJ...COASTAL FLOOD ADVISORY UNTIL 11 PM EST THIS EVENING FOR 
     NJZ016>019-021.
DE...COASTAL FLOOD ADVISORY UNTIL 11 PM EST THIS EVENING FOR 
     DEZ001>003.
MD...COASTAL FLOOD ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR 
     MDZ008-012-015-019-020.
MARINE...GALE WARNING UNTIL 7 PM EST THIS EVENING FOR ANZ450>452.
     SMALL CRAFT ADVISORY UNTIL 6 AM EST SUNDAY FOR ANZ430-431-
     453>455.

&&

$$
SYNOPSIS...MIKETTA
NEAR TERM...MIKETTA
SHORT TERM...MIKETTA
LONG TERM...NIERENBERG
AVIATION...O'HARA
MARINE...O'HARA
HYDROLOGY...
TIDES/COASTAL FLOODING...