NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Feb 23, 11:58 PM EST, 2 hours 2 minutes earlier.
Area forecast discussion, Feb 23, 11:58 PM EST, 2 hours 2 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1158 PM EST TUE FEB 23 2010
.SYNOPSIS...
LOW PRESSURE MOVING NORTHWARD OFF THE DELMARVA PENINSULA THIS
EVENING WILL LIFT SLOWLY INTO SOUTHERN NEW ENGLAND BY WEDNESDAY
NIGHT AND THEN WEAKEN. ANOTHER LOW IS EXPECTED TO DEVELOP OFF THE
SOUTHEASTERN U.S. COAST WEDNESDAY, THEN INTENSIFY AS IT LIFTS TO
SOUTHERN NEW ENGLAND AND STALL BY THURSDAY NIGHT AND INTO FRIDAY.
THE LOW SHOULD WEAKEN AS IT DRIFTS TO THE NORTH OVER THE WEEKEND.
HIGH PRESSURE WILL TRY TO NOSE INTO OUR REGION FROM THE WEST FOR
THE EARLY PART OF THE NEW WEEK.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
IT WAS DECIDED TO INCLUDE NORTHAMPTON COUNTY IN THE WINTER
WEATHER ADVISORY AS STRONG ECHOES SIGNIFYING A RAIN AND SNOW MIX
WERE MOVING THROUGH THE AREA AT THIS TIME. REPORTS OF RAPID SNOW
ACCRUAL WERE RECEIVED...BUT THIS HOPEFULLY WILL NOT LAST TOO LONG.
OTHERWISE MOISTURE WILL CONTINUE TO WRAP INTO OUR REGION AROUND
THE COASTAL LOW TONIGHT. THE MAIN MOISTURE FEED WILL BE DIRECTED
INTO OUR NORTHERN AND EASTERN COUNTIES.
FOR EXTREME SOUTHEASTERN PENNSYLVANIA, SOUTHERN NEW JERSEY,
DELAWARE AND NORTHEASTERN MARYLAND, ANY PRECIPITATION TONIGHT
SHOULD BE MOSTLY RAIN. THE HEAVIER RAIN SHOULD BE CONFINED TO NEW
JERSEY. IF THERE IS ANY MINOR FLOODING ALONG SMALL STREAMS OR IN
AREAS OF POOR DRAINAGE, WE WILL COVER THE SITUATION WITH FLOOD
ADVISORIES. NO FLOOD WATCH WILL BE POSTED.
FROM BERKS COUNTY ACROSS PHILADELPHIA'S NORTHERN SUBURBS TO
CENTRAL NEW JERSEY AND POINTS NORTH WE ARE ANTICIPATING A WINTRY
MIX AS COLDER AIR OOZES DOWN FROM THE NORTH. WHILE BERKS COUNTY,
PHILADELPHIA'S NORTHERN SUBURBS AND CENTRAL NEW JERSEY MAY ONLY
RECEIVE A LIGHT ACCUMULATION OF SNOW TONIGHT, THE POCONOS AND
NORTHERN NEW JERSEY COULD RECEIVE A FEW INCHES, ESPECIALLY IN THE
HIGHER ELEVATIONS. AS A RESULT, WE HAVE EXTENDED THE WINTER
WEATHER ADVISORY THROUGH THE NIGHT AND IT INCLUDES THE
PENNSYLVANIA COUNTIES OF CARBON, MONROE, AND NORTHAMPTON AND THE
NEW JERSEY COUNTIES OF SUSSEX, WARREN AND MORRIS.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
AN UPPER LEVEL SHORT WAVE WAS LOCATED OVER INDIANA AND OHIO THIS
AFTERNOON. IT WILL PROGRESS TO THE EAST AND IT SHOULD PASS
OVERHEAD ON WEDNESDAY MORNING, BRINGING AND END TO MOST OF THE
PRECIPITATION IN OUR REGION.
A LONG WAVE UPPER TROUGH WILL BE ESTABLISHED OVER THE EASTERN
STATES FOR THE SHORT TERM PERIOD, WEDNESDAY THROUGH FRIDAY.
A STRONG UPPER LEVEL SHORT WAVE WAS LOCATED OVER THE UPPER
MISSISSIPPI RIVER THIS AFTERNOON. IT WILL DROP INTO THE TROUGH AND
AN UPPER LOW SHOULD DEVELOP NEAR LAKE MICHIGAN ON WEDNESDAY. THE
FEATURE WILL LIKELY DRIFT EASTWARD AND OFF THE DELMARVA COAST LATE
ON THURSDAY. IT MAY REMAIN ALONG THE JERSEY SHORE INTO FRIDAY
BEFORE DRIFTING TO THE EAST OR NORTHEAST.
MEANWHILE, ANOTHER STRENGTHENING COASTAL LOW WILL WORK ITS WAY UP
FROM THE SOUTH. PRECIPITATION WILL LIKELY BUILD INTO OUR REGION ON
WEDNESDAY NIGHT. THE MOISTURE IS EXPECTED TO WRAP AROUND THE
STRONG LOW AND THE PRECIPITATION SHOULD LINGER INTO FRIDAY. WE ARE
ANTICIPATING MAINLY SNOW IN EASTERN PENNSYLVANIA AND NORTHERN AND
CENTRAL NEW JERSEY. ON THE COASTAL PLAIN WE MAY SEE A MIX TO SLEET
AND RAIN ON THURSDAY, ESPECIALLY NEAR THE COAST.
PRESENT INDICATIONS SUGGEST MAYBE UP TO FOUR INCHES OF SNOW IN
SOUTHERN DELAWARE, PERHAPS 6 TOR 10 INCHES IN PHILADELPHIA AND A
FOOT OR MORE IN NORTHERN NEW JERSEY AND THE POCONOS. OF COURSE,
THE AMOUNTS ARE SUBJECT TO CHANGE AS WE GET CLOSER TO THE SNOW
EVENT.
ANOTHER MAJOR CONCERN WITH THE SYSTEM IS STRONG WINDS. THE SYSTEM
WILL BE QUITE IMPRESSIVE AND WIND GUSTS IN EXCESS OF 40 MPH ARE
NOT OUT OF THE QUESTION FOR THURSDAY INTO FRIDAY.
THE PROBABILITIES GIVEN BELOW ARE BASED ON A COMBINATION OF
STATISTICAL THEORY, OUR SNOWFALL FORECASTS OVER THE PAST SEVERAL
WINTERS, AND THE MOST LIKELY SNOWFALL TOTALS FOR THIS POTENTIAL
STORM. THE PERIOD OF EXPECTED SNOWFALL IS FROM LATE WEDNESDAY
NIGHT INTO FRIDAY MORNING.
====================================================================
PROBABILITY (PERCENT) OF REACHING OR EXCEEDING
THE FOLLOWING STORM-TOTAL SNOWFALL AMOUNTS (INCHES)
====================================================================
STATION 2IN 4IN 6IN 9IN 12IN
====================================================================
MPO >95 95 90 75 50
ABE >95 90 80 60 30
PHL 90 85 75 40 20
ACY 80 70 50 20 10
GED 70 50 25 10 5
====================================================================
PROBABILITIES ARE ROUNDED TO THE NEAREST 5 PERCENT.
STATION IDENTIFIERS:
MPO - MOUNT POCONO, PA (MOUNT POCONO AIRPORT)
ABE - ALLENTOWN, PA (LEHIGH VALLEY INTERNATIONAL AIRPORT)
PHL - PHILADELPHIA, PA (PHILADELPHIA INTERNATIONAL AIRPORT)
ACY - ATLANTIC CITY, NJ (ATLANTIC CITY INTERNATIONAL AIRPORT)
GED - GEORGETOWN, DE (SUSSEX COUNTY AIRPORT)
&&
.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THE WEATHER IN THE EXTENDED REMAINS FOCUSED ON AN AREA OF LOW
PRESSURE THAT WILL BE SLOWLY DRIFTING NORTHWARD INTO NEW ENGLAND
OVER THE WEEKEND, AND SLOWLY DISSIPATING BY SUNDAY NIGHT.
PRECIPITATION CHANCES ARE NOT VERY HIGH AT THIS POINT, MOSTLY
SLIGHT CHANCE THROUGH SUNDAY. WITH THE COLD AIR ALOFT, THE
PRECIPITATION MAY BE MORE SHOWERY IN NATURE, AND DEPENDING ON
WHERE IT FALLS COULD EITHER BE RAIN OR SNOW, OR A COMBINATION OF
THE TWO. AS THE LOW DISSIPATES SUNDAY NIGHT INTO MONDAY, AND A
NORTH TO NORTHWEST FLOW DEVELOPS, PRECIPITATION CHANCES DROP OFF
THROUGH TUESDAY. TEMPERATURES THROUGH THE EXTENDED ARE EXPECTED TO
BE BELOW NORMAL, ESPECIALLY EARLY IN THE PERIOD, WITH A SLIGHT
WARMING TREND EARLY NEXT WEEK.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
IFR/MVFR CEILINGS CONTINUE THIS EVENING AS RAIN FALLS ACROSS THE TAF
SITES. THERE IS ALSO SOME SNOW AND SLEET OCCURRING IN AND AROUND
ABE, SO THIS HAS BEEN INCLUDED. RAIN, POSSIBLY RAIN/SLEET/SNOW FOR
ABE, WILL CONTINUE FOR A GOOD PORTION OF THE NIGHT, AND WHERE THE
RAIN IS HEAVY, VISIBILITIES WILL DROP TO MVFR, AND POSSIBLY IFR. THE
CEILINGS ARE EXPECTED TO REMAIN LOW OVERNIGHT, WITH SOME SLIGHT
IMPROVEMENT MAY OCCUR TOWARD LATE MORNING WITH SOME 1000 FT CEILINGS
AS THE PRECIPITATION ENDS AND CLEARS OUT. WINDS WILL BE CLOSE TO
10-15 KT FROM THE NORTH NORTHEAST ACROSS THE REGION THROUGH TONIGHT
WITH A FEW GUSTS UP TO 20 KT POSSIBLE. WINDS SHOULD DIMINISH AND
TURN MORE TO THE NORTHWEST OR WEST ON WEDNESDAY.
OUTLOOK...
LOWER CEILINGS AND VISIBILITIES ARE IN STORE FOR LATE WEDNESDAY,
THURSDAY AND INTO FRIDAY AS THE NEXT SYSTEM MOVES INTO AREA. PERIODS
OF SNOW ARE ALSO EXPECTED ALONG WITH GUSTY WINDS.
&&
.MARINE...
SMALL CRAFT CONDITIONS, MAINLY FOR 5 FT SEAS, CONTINUE ON THE WATERS
THIS EVENING AND SHOULD CONTINUE THROUGH THE OVERNIGHT HOURS.
WINDS ARE EXPECTED TO PICK UP AGAIN TONIGHT WITH GUSTS OF 25 KTS.
WINDS AND SEAS SHOULD START TO DISSIPATE SOME WEDNESDAY LATE MORNING
AND THROUGH THE AFTERNOON FROM SOUTH TO NORTH. ENDING TIME STILL
LOOKS GOOD FOR THE SCA SO NO CHANGES WERE MADE AT THIS TIME.
GALES REMAIN LIKELY FOR THURSDAY AND FRIDAY WITH GROWING CONFIDENCE
WITH THE NEXT SYSTEM AS IT INTENSIFIES AND MOVES UP THE COAST. WINDS
ARE EXPECTED TO PICK UP THURSDAY MORNING AND SEAS WILL RESPOND
SHORTLY AFTER. WE HAVE CAPPED WIND GUSTS AT 45 KT FOR NOW BUT MODEL
GUIDANCE GOES INDICATE THAT STORM FORCE WINDS COULD OCCUR FOR A
BRIEF PERIOD DURING THE STORM. HAVE OPTED TO GO WITH A GALE WATCH
FOR THURSDAY AND FRIDAY WHICH WILL ALLOW FOR ANOTHER COUPLE OF MODEL
RUNS TO NARROW DOWN THE STRENGTH OF THE WINDS.
SEAS WILL SLOWLY START TO COME DOWN, ALONG WITH THE WINDS, LATE ON
FRIDAY BUT PROBABLY WONT BE BELOW 5 FT UNTIL SOMETIME LATER IN THE
WEEKEND.
&&
.HYDROLOGY...
CURRENT THINKING IS THAT THE SOUTHERN ZONES WILL SEE ANOTHER 0.25
TO 0.50 INCH THROUGH THE OVERNIGHT. FURTHER NORTH, WE'RE THINKING
0.50 TO 1.00 INCH. THIS IS ON TOP OF THE 0.20 TO 0.60 OF RAIN THAT
HAS ALREADY FALLEN.
AFTER REVIEWING THE GUIDANCE, WE FEEL THAT THE EXPECTED RAINFALL
IN COMBINATION WITH SOME SNOWMELT WILL NOT BE ENOUGH TO CAUSE
RIVERS TO RISE ABOVE THEIR BANKS. INSTEAD, WE FEEL THAT NUISANCE
TYPE FLOODING IN LOW-LYING OR POOR DRAINAGE AREAS IS MORE LIKELY.
WITH THIS IN MIND, WE PLAN TO HANDLE ANY FLOODING THAT
MATERIALIZES THROUGH THE NIGHT WITH ADVISORIES RATHER THAN
WARNINGS. IN FACT, AN URBAN AND SMALL STREAM FLOOD ADVISORY WAS
ISSUED EARLIER FOR PORTIONS OF SOUTHEASTERN AND CENTRAL NEW
JERSEY AS WELL AS NORTHERN CHESTER...MONTGOMERY AND UPPER BUCKS
COUNTIES IN PENNSYLVANIA.
JUST AS AN FYI AND AS A CONTINGENCY, IF OUR QPF FORECAST IS
WRONG, AND IT FOLLOWS THE MORE EXPLOSIVE GFS SOLUTION (OUTLIER),
CONCERN WOULD QUICKLY SHIFT TO THE NORTHERN COASTAL PLAIN (LIKE
THE METEDECONK), THE RARITAN BASIN (LIKE THE MILLSTONE), AND THE
PASSAIC BASIN (PINE BROOK IN A COUPLE OF DAYS). WARNINGS WOULD
LIKELY BE NEEDED. WE'LL ALSO NEED TO WATCH THE RANCOCAS IN THE
COMING DAYS.
&&
.TIDES/COASTAL FLOODING...
TIDAL DEPARTURES AT SANDY HOOK WERE RUNNING OVER TWO FEET ABOVE
ASTRONOMICAL LATE THIS EVENING. FURTHER SOUTH, WHERE WINDS HAVE
COME AROUND TO OFFSHORE, THE DEPARTURES WERE SLOWLY DIMINISHING.
THE ACCENT THERE IS ON THE WORD SLOWLY. LATEST MODELS INDICATE
THAT, ALTHOUGH THE NORTHEAST WIND /PERFECT FOR POSITIVE ANOMALIES/
WILL WEAKEN OVER THE COURSE OF THE NIGHT, THEY WON'T COME AROUND
TO OFFSHORE BEFORE HIGH TIDE OCCURS /GENERALLY BETWEEN 215 AM AND
315 AM EST ALONG THE NORTHERN PART OF THE NEW JERSEY ATLANTIC
COASTLINE AND THE RARITAN BAY SHORELINE, AND A COUPLE OF HOURS
LATER ALONG ADJACENT BACK BAYS/. WE DECIDED TO ISSUE AN ADVISORY
FOR MINOR TIDAL FLOODING TONIGHT FOR THESE AREAS.
LATEST GUIDANCE INDICATES THAT MINOR TIDAL FLOODING IS POSSIBLE
WITH THE THURSDAY MORNING HIGH TIDES MAINLY ALONG THE OCEAN FRONT.
WITH THIS OUT INTO THE 3RD AND 4TH PERIODS WE WILL HOLD OFF
ISSUING ANY HEADLINES AT THIS TIME. THE NEXT TIME OF CONCERN WILL
BE BLOWOUT TIDES ON THURSDAY NIGHT INTO FRIDAY AS THE LOW WRAPS UP
AND FINALLY STARTS TO MAKE ITS MOVE AWAY FROM THE REGION.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...WINTER WEATHER ADVISORY UNTIL 8 AM EST WEDNESDAY FOR PAZ054-
055-062.
WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH FRIDAY
MORNING FOR PAZ054-055-060>062-067>071.
NJ...WINTER WEATHER ADVISORY UNTIL 8 AM EST WEDNESDAY FOR NJZ001-
007-008.
WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH FRIDAY
MORNING FOR NJZ001-007>010-012>027.
COASTAL FLOOD ADVISORY UNTIL 6 AM EST WEDNESDAY FOR NJZ012>014-
020-026.
DE...WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH FRIDAY
MORNING FOR DEZ001>004.
MD...WINTER STORM WATCH FROM LATE WEDNESDAY NIGHT THROUGH FRIDAY
MORNING FOR MDZ008-012-015-019-020.
MARINE...GALE WATCH FROM THURSDAY MORNING THROUGH FRIDAY EVENING FOR
ANZ430-431-450>455.
SMALL CRAFT ADVISORY UNTIL 6 AM EST WEDNESDAY FOR ANZ431-
452>455.
SMALL CRAFT ADVISORY UNTIL 6 PM EST WEDNESDAY FOR ANZ450-451.
&&
SYNOPSIS...IOVINO/
NEAR TERM...IOVINO/
SHORT TERM...IOVINO
LONG TERM...ROBERTSON
AVIATION...ROBERTSON/MEOLA
MARINE...ROBERTSON/MEOLA
HYDROLOGY...KRUZDLO
TIDES/COASTAL FLOODING...DELISI