724
FXUS61 KPHI 172031
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
331 PM EST MON FEB 17 2025
SYNOPSIS
HIGH PRESSURE BUILDS IN FROM THE WEST BEFORE SLIDING SOUTH AND
EAST OF THE REGION TUESDAY NIGHT. LOW PRESSURE APPROACHES THE
MID-ATLANTIC AND MOVES OFFSHORE WEDNESDAY THROUGH THURSDAY.
HIGH PRESSURE RETURNS FOR THE END OF THE WEEK AND THIS WEEKEND.
NEAR TERM /THROUGH TUESDAY/
ARCTIC AIR CONTINUES TO POUR INTO OUR REGION THROUGH TUESDAY
ALONG WITH GUSTY WINDS.
AN UPPER-LEVEL TROUGH IS ELONGATED FROM THE CANADIAN MARITIMES,
WHERE THE MAIN PORTION OF IT RESIDES, WESTWARD ACROSS SOUTHERN
CANADA. INTENSE SURFACE LOW PRESSURE, CENTRAL PRESSURE NEAR 960
MB, WILL CONTINUE TO MOVE INTO THE CANADIAN MARITIMES WHERE IT
STALLS INTO TUESDAY. THIS HAS RESULTED IN STRONG ZONAL FLOW ON
THE SOUTHERN FLANK OF THE TROUGH. COLD AIR ADVECTION WILL
CONTINUE THROUGH TONIGHT AS ARCTIC AIR POURS ACROSS THE AREA.
THE COMBINATION OF THE INTENSE SURFACE LOW WELL TO OUR
NORTHEAST AND STRONG HIGH PRESSURE IN THE NORTHERN PLAINS TO THE
MISSISSIPPI VALLEY IS MAINTAINING A TIGHT PRESSURE GRADIENT
ACROSS OUR AREA. THIS SETUP IS RESULTING IN DEEP VERTICAL MIXING
AS 925 MB WINDS ARE AROUND 40 KNOTS. THE FLOW BELOW 850 MB
ESPECIALLY WILL GRADUALLY WEAKEN THROUGH TUESDAY, HOWEVER IT
WILL STILL BE STRONG ENOUGH TO KEEP BREEZY CONDITIONS. THERE MAY
BE AT LEAST SOME PARTIAL DECOUPLING TONIGHT ESPECIALLY FOR THE
MORE SHELTERED LOCATIONS. THERE HAS BEEN A NOTABLE DOWNWARD
TREND IN THE WINDS THIS AFTERNOON ACROSS NEARLY THE ENTIRE AREA
WITH GUSTS MOSTLY BELOW CRITERIA. WHILE IT STILL REMAINS GUSTY
THE OVERALL RISK OF DAMAGING WINDS HAS PASSED AND THEREFORE
CANCELLED THE WIND ADVISORY AND HIGH WIND WARNING. A NOTABLE
BREEZE SHOULD STILL BE MAINTAINED THROUGH THE NIGHT ACROSS THE
AREA. THE EXTENT OF THE WIND WILL DETERMINE HOW LOW THE WIND
CHILLS GET THROUGH THE NIGHT. MOST AREAS DROP INTO THE SINGLE
DIGITS, HOWEVER AREAS NORTH AND WEST OF I-95 DROP TO ZERO OR A
LITTLE BELOW AT TIMES. THE POCONO REGION HOWEVER GETS AS LOW AS
15 BELOW, AND THEREFORE ISSUED A COLD WEATHER ADVISORY FOR
CARBON AND MONROE COUNTIES ONLY.
AS WE GO THROUGH TUESDAY, THE SYNOPTIC SETUP IS SIMILAR WITH
MORE ZONAL FLOW ACROSS OUR AREA. THE PRESSURE GRADIENT WILL
WEAKEN SOME WITH TIME AS DOES THE FLOW IN THE MIXING LAYER,
HOWEVER A GUSTY BREEZE WILL STILL CONTINUE GIVEN THE COLD AIR
ADVECTION AND DECENT MIXING HEIGHTS. THE WINDS ARE EXPECTED TO
BE NOT AS STRONG AS THE LAST TWO DAYS, GENERALLY SUSTAINED 15-20
MPH WITH GUSTS 25-35 MPH. THE WIND SHOULD TEND TO DIMINISH
QUICKER LATER IN THE AFTERNOON. IT WILL BE A VERY COLD DAY WITH
MOST IF NOT ALL OF OUR AREA NOT GETTING ABOVE FREEZING FOR HIGH
TEMPERATURES. WIND CHILLS IMPROVE SOME, BUT STILL IN THE TEENS
DURING THE AFTERNOON WITH SINGLE DIGITS TO ZERO FOR THE I-80
CORRIDOR. THE COLD WEATHER ADVISORY GOES UNTIL 10 AM TUESDAY FOR
CARBON AND MONROE COUNTIES.
SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/
HIGH PRESSURE REMAINS OVER THE AREA TUESDAY NIGHT WITH
CONTINUED WELL BELOW NORMAL TEMPERATURES. THE PRESSURE GRADIENT
WILL REMAIN TIGHT ENOUGH FOR WINDS TO AVERAGE 10 TO 15 MPH WITH
GUSTS UP TO 20 MPH FOR MOST OF THE NIGHT, AND THIS SHOULD BE
ENOUGH FOR OPTIMAL RADIATIONAL COOLING CONDITIONS TO DEVELOP,
ALLOWING TEMPERATURES TO DROP FURTHER. STILL QUITE COLD WITH
LOWS IN THE SINGLE DIGITS IN THE SOUTHERN POCONOS AND FAR
NORTHWEST NEW JERSEY, AND IN THE TEENS MOST ELSEWHERE. ALONG
WITH THE ELEVATED WINDS, THIS WILL YIELD WIND CHILL VALUES
POSSIBLY AS LOW AS -15 IN THE HIGHER ELEVATIONS OF THE SOUTHERN
POCONOS, BUT OTHERWISE IN THE SINGLE DIGITS.
HIGH PRESSURE WILL BE OFFSHORE BY WEDNESDAY MORNING.
A CLOSED H5 LOW WILL DIVE INTO THE MIDWEST ON WEDNESDAY,
CARVING OUT AN UPPER TROUGH THAT WILL DIG DOWN INTO THE GULF
COAST STATES. SURFACE LOW PRESSURE WILL DEVELOP OUT AHEAD OF THE
BASE OF THE TROUGH, AND THIS LOW WILL LIFT TOWARDS THE MID-
ATLANTIC WEDNESDAY NIGHT.
MODELS TRENDS WITH THE TRACK OF THE LOW CONTINUE TO REMAIN
SOUTH AND EAST OF NEW JERSEY, RESULTING IN THE BULK OF THE SNOW
FALLING OVER SOUTHERN PORTIONS OF DELAWARE AND THE EASTERN
SHORES OF MARYLAND, AND MINIMAL SNOW ACCUMULATIONS FOR THE
MAJORITY OF THE FORECAST AREA. THE LOW LOOKS TO BE OFF THE
VIRGINIA-NORTH CAROLINA COAST LATE WEDNESDAY NIGHT, AND THEN
SOME 350 TO 400 MILES EAST OF ATLANTIC CITY BY THURSDAY
AFTERNOON.
SNOWFALL ACCUMULATIONS EXPECTED, FROM WEDNESDAY AFTERNOON
THROUGH THURSDAY:
LESS THAN AN INCH OVER THE SOUTHERN POCONOS, NORTHERN NEW
JERSEY, AND THE LEHIGH VALLEY DOWN TO THE I-95 CORRIDOR.
1 TO 2 INCHES FOR THE DELAWARE VALLEY, MOST OF SOUTHERN NEW
JERSEY AND COASTAL NEW JERSEY.
2 TO 4 INCHES FOR SOUTHERN PORTIONS OF THE EASTERN SHORES OF
MARYLAND, SOUTHERN DELAWARE, AND EXTREME SOUTHEAST NEW JERSEY
WITH UP TO 5 INCHES POSSIBLE IN PORTIONS OF SOUTHERN DELWARE.
THE 13Z/17 NBM SHOWS A 0 TO 5 PERCENT PROBABILITY OF GREATER
THAN 4 INCHES OF SNOW FOR THE SOUTHERN POCONOS, LEHIGH VALLEY,
AND NORTHERN NEW JERSEY AND DOWN TO THE I-95 CORRIDOR FROM
PHILADELPHIA TO WILMINGTON, A 15 TO 20 PERCENT PROBABILITY FOR
GREATER THAN 4 INCHES OF SNOW FOR MOST OF SOUTHERN NEW JERSEY
AND THE DELAWARE VALLEY, AND A 20 TO 40 PERCENT PROBABILITY FOR
GREATER THAN 4 INCHES OF SNOW FOR SOUTHERN DELMARVA AND EXTREME
SOUTHEAST NEW JERSEY IN THE 48 HOUR PERIOD FROM 7 PM TUESDAY
THROUGH 7 PM THURSDAY.
WILL GO AHEAD AND ISSUE A WINTER STORM WATCH FOR SUSSEX COUNTY
(DE) FOR WEDNESDAY AFTERNOON THROUGH THURSDAY. WINTER WEATHER
ADVISORIES MAY BE NEEDED FOR PORTIONS OF MARYLAND, DELAWARE, AND
EXTREME SOUTHERN NEW JERSEY. IT IS ALSO POSSIBLE FOR THIS WATCH
TO BE CONVERTED TO AN ADVISORY IF LOWER TOTALS ARE EXPECTED IN
SUSSEX COUNTY (DE).
TRENDS CONTINUE TO KEEP TAKING THE LOW SOUTH AND EAST FROM THE
LOCAL AREA, SO THESE TOTALS MAY GO DOWN FURTHER.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
LOW PRESSURE CONTINUES TO DEPART THURSDAY EVENING, AND
LINGERING SNOW WILL ROTATE BACK TOWARDS THE JERSEY SHORE,
RESULTING IN MINIMAL, AT BEST, ADDITIONAL SNOW ACCUMULATIONS.
FROM THERE, HIGH PRESSURE WILL DOMINATE INTO THE START OF THE
NEW WEEK. SURFACE HIGH PRESSURE OF 1040 MB WILL BE CENTERED OVER
THE CENTRAL PLAINS THURSDAY NIGHT BEFORE PROPAGATING OVER THE
OHIO AND TENNESSEE VALLEYS BY FRIDAY, THEN SLIDING OFF THE MID-
ATLANTIC COAST OVER THE WEEKEND.
TEMPERATURES WILL REMAIN BELOW SEASONAL AVERAGES FRIDAY AND
SATURDAY BEFORE MODERATING BACK TO THE SEASONAL AVERAGES BY
SUNDAY AND MONDAY.
AVIATION /20Z MONDAY THROUGH SATURDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
REST OF THIS AFTERNOON...VFR. WEST-NORTHWEST WINDS 15-25 KNOTS
WITH GUSTS TO AROUND 35 KNOTS. MODERATE CONFIDENCE.
TONIGHT...VFR. WEST-NORTHWEST WINDS DIMINISHING TO 12-15 KNOTS
WITH GUSTS 20-30 KNOTS. SOME TERMINALS HOWEVER MAY LOSE THE
GUSTS FOR A WHILE. MODERATE CONFIDENCE.
TUESDAY...VFR. WEST-NORTHWEST WINDS 15-20 KNOTS WITH GUSTS UP
TO 30 KNOTS. MODERATE CONFIDENCE.
OUTLOOK...
TUESDAY NIGHT...VFR.
WEDNESDAY THROUGH THURSDAY...SUB-VFR CONDITIONS LIKELY IN SN
FOR KMIV/KACY, AND A SUB-VFR CONDITIONS POSSIBLE IN SN FOR THE
REST OF THE TERMINALS.
THURSDAY NIGHT THROUGH SATURDAY...VFR.
MARINE
THE STRONG WINDS CONTINUE TO DIMINISH SOME FROM SOUTH TO NORTH,
AND THEREFORE THE GALE WARNING HAS BEEN REPLACED WITH A SMALL
CRAFT ADVISORY FOR ALL AREAS EXCEPT THE NORTHERN NEW JERSEY
ATLANTIC COASTAL WATERS. THE ADVISORY GOES THROUGH THE DAY
TUESDAY. THE GALE WARNING FOR THE TWO NORTHERN NEW JERSEY ZONES
GOES THROUGH TONIGHT, HOWEVER THIS MAY COME DOWN SOONER. SEAS
5-7 FEET WILL GRADUALLY SUBSIDE THROUGH TUESDAY GIVEN THE STRONG
OFFSHORE WIND.
AS THE COLD AIR CONTINUES TO POUR IN ACROSS OUR AREA THROUGH
TUESDAY, GUSTY WINDS COMBINED WITH WAVE ACTION WILL RESULT IN
AREAS OF LIGHT FREEZING SPRAY DEVELOPING TONIGHT INTO TUESDAY.
AS OF NOW, LIGHT ICE ACCRETION RATES ARE ANTICIPATED AND
THEREFORE NO ADVISORY HAS BEEN ISSUED.
OUTLOOK...
TUESDAY NIGHT...SCA CONDITIONS. THERE IS A CHANCE FOR FREEZING
SPRAY.
WEDNESDAY THROUGH WEDNESDAY NIGHT...SUB-SCA CONDITIONS. VSBY
RESTRICTIONS IN SN POSSIBLE STARTING LATE WEDNESDAY AFTERNOON.
THURSDAY THROUGH THURSDAY NIGHT...SCA CONDITIONS. VSBY
RESTRICTIONS IN SN THURSDAY.
FRIDAY THROUGH FRIDAY NIGHT...SCA CONDITIONS FRIDAY, SUBSIDING
FRIDAY NIGHT.
SATURDAY...SUB-SCA CONDITIONS.
PHI WATCHES/WARNINGS/ADVISORIES
PA...COLD WEATHER ADVISORY FROM 10 PM THIS EVENING TO 10 AM EST
TUESDAY FOR PAZ054-055.
NJ...NONE.
DE...WINTER STORM WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
AFTERNOON FOR DEZ003-004.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST TUESDAY FOR ANZ430-431-
452>455.
GALE WARNING UNTIL 6 AM EST TUESDAY FOR ANZ450-451.
SYNOPSIS...MPS
NEAR TERM...GORSE
SHORT TERM...MPS
LONG TERM...MPS
AVIATION...GORSE/MPS
MARINE...GORSE/MPS
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