373
FXUS61 KPHI 211527
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1027 AM EST SAT DEC 21 2024
SYNOPSIS
LOW PRESSURE OFF LONG ISLAND WILL LIFT NORTH INTO THE CANADIAN MARITIMES
BY TONIGHT. MEANWHILE, ARCTIC HIGH PRESSURE OVER CENTRAL CANADA WILL
TRACK EAST THIS WEEKEND, EVENTUALLY BUILDING OVER NEW YORK STATE AND
THE NORTHEAST SUNDAY NIGHT INTO MONDAY MORNING. THIS HIGH DEPARTS
MONDAY NIGHT, AND THEN WEAK LOW PRESSURE PASSES THROUGH THE REGION
ON CHRISTMAS EVE. HIGH PRESSURE RETURNS TO CLOSE OUT THE WEEK.
NEAR TERM /THROUGH TONIGHT/
LIGHT SNOW EXITING THE AREA EARLY TODAY, THEN TURNING MUCH
COLDER, DRIER, AND BREEZY.
THE DISTURBANCE THAT BROUGHT THE SNOW ACROSS THE AREA YESTERDAY
AND OVERNIGHT CONTINUES TO MOVE AWAY FROM OUR AREA. AN UPPER
TROUGH LINGERS OVER THE AREA, SO SOME LINGERING SNOW SHOWERS
CONTINUE TO MOVE NW TO SE ACROSS THE LEHIGH VALLEY, METRO
PHILADELPHIA AND INTO NJ. THESE SNOW SHOWERS WILL NOT ADD ANY
SIGNIFICANT ACCUMULATIONS TO WHAT HAS ALREADY FALLEN. GUSTY
WINDS MAY BLOW THE SNOW AROUND A BIT AT TIMES WITH BRIEFLY LOWER
VISIBILITIES ON SOME ROADS. THE REMAINING SNOW SHOWERS WILL
LIKELY BE DONE BY MID-AFTERNOON.
THE MAIN WEATHER STORY FOR THE NEAR TERM WILL BE THE IMPRESSIVE
COLD ADVECTION INTO TONIGHT. ARCTIC HIGH PRESSURE WILL BUILD
ACROSS SOUTHERN ONTARIO TODAY INTO TONIGHT, ADVECTING A VERY
COLD AND DRY AIRMASS INTO OUR REGION. 850 MB TEMPERATURES LOOK
TO FALL TO NEAR -15C (GIVE OR TAKE A COUPLE DEGREES). THIS WILL
TRANSLATE TO MUCH BELOW NORMAL TEMPERATURES TODAY, AND ESPECIALLY
TONIGHT INTO SUNDAY. HIGH TEMPERATURES TODAY WILL RANGE FROM
THE 20S NORTH OF I-78, TO THE LOW TO MID 30S SOUTH OF I-78.
IN ADDITION TO THE COLD DAYTIME TEMPERATURES TODAY, IT WILL
ALSO BE QUITE BLUSTERY. 925 AND 850 MB WINDS WILL INCREASE TO
AROUND 25-30 KTS BETWEEN THE STRENGTHENING STORM OFFSHORE AND
STRONG HIGH PRESSURE TO OUR NORTHWEST TODAY. EXPECT SUSTAINED
WINDS NEAR 15-20 MPH WITH PEAK GUSTS AROUND 30-35 MPH MUCH OF
THE DAY. WIND CHILLS WILL TOP OUT ONLY AROUND 15-25 DEGREES
TODAY. COLD ADVECTION PEAKS NEAR 00Z, SO THE WINDS SHOULD
SUBSIDE SOME AND BECOME LESS GUSTY INTO TONIGHT. HOWEVER, THE
MODEST GRADIENT IN PLACE WILL KEEP WINDS ELEVATED AROUND 10-15
MPH MUCH OF THE NIGHT.
THE PERSISTENT BREEZE TONIGHT COMBINED WITH TEMPERATURES
FALLING TO THE LOW TO MID 10S ACROSS MUCH OF THE AREA (SINGLE
DIGITS IN THE HIGHER TERRAIN OF THE SOUTHERN POCONOS AND NW NJ)
WILL PRODUCE BITTERLY COLD WIND CHILLS IN THE SINGLE DIGITS
ACROSS MUCH OF THE AREA, AND BELOW ZERO IN THE HIGHER TERRAIN.
ACROSS THE POCONO PLATEAU, WIND CHILLS WILL BE AS LOW AS -12
DEGREES. A COLD WEATHER ADVISORY REMAINS IN EFFECT THERE FOR
TONIGHT THROUGH SUNDAY MORNING.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/
1036+ MB ARCTIC HIGH PRESSURE WILL BE OVER THE EASTERN GREAT
LAKES SUNDAY MORNING BEFORE BUILDING TO THE SOUTH AND EAST
SUNDAY NIGHT THROUGH MONDAY MORNING. HIGH PRESSURE MOVES
OFFSHORE AND DEPARTS MONDAY NIGHT.
A BITTERLY COLD AIRMASS WILL SPREAD INTO THE REGION DURING THIS
TIME WITH HIGHS ONLY IN THE TEENS IN THE SOUTHERN POCONOS, AND
OTHERWISE IN THE MID TO UPPER 20S, WHICH ARE SOME 20 DEGREES
BELOW NORMAL FOR THIS TIME OF THE YEAR. THE COLDEST TEMPERATURES
IN QUITE SOME TIME WILL BE FELT SUNDAY NIGHT WITH LOWS
GENERALLY IN THE SINGLE DIGITS TO AS LOW AS 5 BELOW IN THE
SOUTHERN POCONOS. IN FACT, THE LAST TIME THE LOW TEMPERATURE WAS
LESS THAN 10 DEGREES AT PHILADELPHIA INTERNATIONAL AIRPORT WAS
DECEMBER 24, 2022 WHEN THE LOW WAS 7. IT WILL COME CLOSE TO THIS
SUNDAY NIGHT.
TEMPERATURES WARM UP BY ABOUT 5 DEGREES ON MONDAY COMPARED TO
SUNDAY, TOPPING OFF IN THE UPPER 20S TO LOW 30S, EXCEPT FOR
SOUTHEAST NEW JERSEY AND SOUTHERN DELMARVA, WHERE HIGHS WILL BE
IN THE MID TO UPPER 30S.
A CLIPPER SYSTEM APPROACHES MONDAY NIGHT FROM THE WEST. LIGHT
SNOW WILL MOVE INTO THE REGION FROM WEST TO EAST AFTER MIDNIGHT,
AND UP TO A QUICK QUARTER OF AN INCH OF SNOW IS POSSIBLE,
MAINLY FOR THE SOUTHERN POCONOS, LEHIGH VALLEY, AND NORTHERN NEW
JERSEY.
LONG TERM /TUESDAY THROUGH FRIDAY/
CLIPPER SYSTEM PASSES THROUGH THE REGION ON CHRISTMAS EVE,
PRODUCING MINIMAL SNOW ACCUMULATION, BUT GENERALLY A QUARTER OF
AN INCH OR SO IN THE NORTHERN AREAS. SNOW MIXES WITH AND CHANGES
TO RAIN IN THE SOUTHERN HALF OF THE FORECAST AREA BEFORE
TAPERING OFF.
HIGH PRESSURE BUILDS OVER THE AREA ON CHRISTMAS DAY WITH HIGHS
WARMING BACK CLOSER TO NORMAL, BUT STILL A FEW DEGREES SHY OF
NORMAL FOR THIS TIME OF THE YEAR.
ALTHOUGH HIGH PRESSURE WILL DOMINATE THE AREA INTO THE END OF
THE WEEK, THERE MAY BE A FEW WEAK MID-LEVEL IMPULSES THAT COULD
PRODUCE SOME LIGHT RAIN OR SNOW ON THURSDAY AND FRIDAY. POPS
WILL BE CAPPED AT SLIGHT CHANCE FOR BOTH DAYS. TEMPERATURES WARM
BACK TO NORMAL WITH HIGHS IN THE LOW TO MID 40S.
AVIATION /15Z SATURDAY THROUGH WEDNESDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TODAY...VFR EXPECTED. A FEW SNOW SHOWERS WITH SHORT PERIODS OF
LOWER VSBY POSSIBLE KPNE,KACY,KABE. NORTHWEST WINDS 15-20 KTS
WITH GUSTS UP TO 30 KTS. HIGH CONFIDENCE.
TONIGHT...VFR. NORTHWEST WINDS NEAR 10 KTS. HIGH CONFIDENCE.
OUTLOOK...
SUNDAY THROUGH MONDAY...VFR/NSW.
MONDAY NIGHT THROUGH TUESDAY...MVFR OR IFR CONDITIONS IN SN,
POSSIBLY MIXING WITH AND CHANGING TO RA BEFORE ENDING TUESDAY
AFTERNOON.
WEDNESDAY...VFR/NSW.
MARINE
NORTHWEST WINDS INCREASING TO AROUND 25-30 KTS TODAY, SUBSIDING
GRADUALLY INTO TONIGHT. A FEW BRIEF GALE FORCE GUSTS NEAR 35
KTS POSSIBLE, BUT THESE ARE NOT EXPECTED TO PREVAIL. WIND GUSTS
UP TO 25 KTS POSSIBLE THROUGH TONIGHT. SEAS 4-6 FEET,
DIMINISHING GRADUALLY TONIGHT. SMALL CRAFT ADVISORY REMAINS IN
EFFECT FOR ALL ATLANTIC AND DELAWARE BAY COASTAL WATERS TODAY
THROUGH TONIGHT.
PERIODS OF SNOW REDUCING VISIBILITY TO 1-3 NM AT TIMES NORTH OF
BARNEGAT LIGHT THROUGH MID MORNING.
OUTLOOK...
SUNDAY THROUGH WEDNESDAY...WILL EXTEND THE SCA FOR THE OCEAN
WATERS INTO SUNDAY AFTERNOON. SUB-SCA CONDITIONS THEN THROUGH
WEDNESDAY.
PHI WATCHES/WARNINGS/ADVISORIES
PA...COLD WEATHER ADVISORY FROM 8 PM THIS EVENING TO 9 AM EST
SUNDAY FOR PAZ054-055.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 AM EST SUNDAY FOR ANZ430-431.
SMALL CRAFT ADVISORY UNTIL 1 PM EST SUNDAY FOR ANZ450>455.
SYNOPSIS...MPS
NEAR TERM...STAARMANN/PO
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...MPS/STAARMANN/PO
MARINE...MPS/STAARMANN
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