551
FXUS61 KPHI 191138
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
638 AM EST WED FEB 19 2025
SYNOPSIS
AN AREA OF LOW PRESSURE DEVELOPS OFF THE CAROLINA COAST
LATER TODAY THEN TRACKS NORTHEASTWARD AND OUT TO SEA THROUGH
THURSDAY. HIGH PRESSURE WILL BUILD IN LATER FRIDAY INTO
SATURDAY, THEN LOW PRESSURE TRACKS ACROSS THE GREAT LAKES REGION
EARLY NEXT WEEK WITH A WEAK COLD FRONT APPROACHING OUR AREA.
NEAR TERM /THROUGH THURSDAY/
MORNING UPDATE: THE COLD WEATHER ADVISORY WAS CANCELLED AS
TEMPERATURES START TO RISE THIS MORNING. OTHERWISE FORECAST IN
GOOD SHAPE WITH CLOUDS STARTING TO FILTER IN OVER THE MID
ATLANTIC REGION THIS MORNING. PREVIOUS DISCUSSION FOLLOWS:
A LARGE ARCTIC HIGH PRESSURE SYSTEM IS LOCATED OVER THE CENTRAL
CONUS EARLY THIS MORNING, WITH A SECONDARY HIGH CENTERED OVER
DELMARVA. VERY COLD AIR IS IN PLACE, WITH TEMPERATURES RANGING
FROM THE LOWER 10S ACROSS THE POCONOS TO THE UPPER 10S AND LOWER
20S ELSEWHERE ACROSS OUR AREA. NORTHWESTERLY SURFACE FLOW ON
THE ORDER OF 10 KT OR SO IS LEADING TO EVEN COLDER WIND CHILL
VALUES, IN THE SINGLE DIGITS ACROSS MOST OF THE AREA, AND BELOW
ZERO FOR THE POCONOS. A COLD AIR ADVISORY IS IN PLACE FOR CARBON
AND MONROE COUNTIES WHERE WIND CHILLS OF -10 TO -15F WILL BE
COMMON THROUGH THE REMAINDER OF THE OVERNIGHT HOURS. TEMPERATURES
WILL CONTINUE TO FALL THROUGH DAYBREAK, THOUGH THIS MAY BE
TEMPERED SLIGHTLY BY HIGH CLOUDS APPROACHING THE SOUTHERN HALF
OF THE AREA. REGARDLESS, TEMPERATURES WILL LIKELY STILL BOTTOM
OUT IN THE MID 10S FOR AREAS SOUTH AND EAST OF THE FALL LINE,
AND IN THE SINGLE DIGITS NORTH AND EAST OF IT.
WITH THE HIGH CLOUD COVER IN PLACE ACROSS MUCH OF THE AREA AND
CONTINUED MODEST NORTHWESTERLY LOW-LEVEL FLOW, TEMPERATURES WILL
BE SLOW TO RISE. EXPECT HIGH TEMPERATURES TO BE BELOW FREEZING
AREA- WIDE.
AS WE PROGRESS INTO THE AFTERNOON HOURS, A CLOSED MID-LEVEL LOW
WILL BEGIN TO APPROACH THE AREA FROM THE WEST. IN RESPONSE, A
SURFACE LOW WILL DEVELOP OFF THE SOUTHEAST COAST AND BEGIN TO
APPROACH THE AREA BY THIS AFTERNOON. THIS WILL BRING INCREASING
CLOUD COVER TO THE ENTIRE AREA. SNOW CHANCES WILL BEGIN TO
INCREASE ACROSS PORTIONS OF EASTERN MARYLAND AND SOUTHERN
DELAWARE THIS AFTERNOON, AND EVENTUALLY INTO PORTIONS OF
SOUTHERN NEW JERSEY THIS EVENING.
OVERALL, THE FOLLOWING SNOWFALL TOTALS CAN BE EXPECTED:
LESS THAN AN INCH OVER THE SOUTHERN POCONOS, NORTHERN NEW
JERSEY, THE LEHIGH VALLEY DOWN TO THE I-95 CORRIDOR, THE
DELAWARE VALLEY AND MOST OF SOUTHERN NEW JERSEY.
1 TO 3 INCHES FOR SOUTHERN PORTIONS OF THE EASTERN SHORES OF
MARYLAND, SOUTHERN DELAWARE, AND EXTREME SOUTHEAST NEW JERSEY.
CONFIDENCE IN THE SYNOPTIC SNOW AMOUNTS IS FAIRLY HIGH IN THAT
WE'LL SEE GENERALLY LOW SNOW TOTALS BUT SOME ENSEMBLE MEMBERS
DO SHOW THE POTENTIAL FOR A HIGHER IMPACT MESOSCALE BAND TO
DEVELOP OVER PORTIONS OF SOUTHERN DELAWARE. THE WPC SNOWBAND
PROTOTYPE SHOWS AT LEAST ONE BAND FROM THE HREF MOVING INTO
SUSSEX COUNTY DE. IF THIS DOES OCCUR, RATES COULD EASILY EXCEED
1"/HOUR AND QUICKLY ACCUMULATE. IN THIS SCENARIO, NARROW SNOWFALL
AMOUNTS UP TO 6-10" WOULD BE POSSIBLE. AGAIN, THATS NOT
EXPECTED, BUT USERS SHOULD REMAIN ALERT TO CHANGES IN THE
FORECAST.
SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/
COLD AND BLUSTERY TO CLOSE OUT THE WEEK AS HIGH PRESSURE BUILDS
IN FROM THE WEST. FORTUNATELY, THE HIGH WILL BE WEAKENING AS IT
DOES SO, AND WANING COLD ADVECTION WILL ALLOW FOR SOME AIRMASS
MODIFICATION ON FRIDAY UNDER MOSTLY SUNNY SKIES.
EXPECTED AFTERNOON HIGHS ON FRIDAY TO TOP OUT IN THE MID TO
UPPER 30S IN MANY AREAS, WITH MANY AREAS SOUTH OF I-78 CLIMBING
ABOVE FREEZING FOR THE FIRST TIME SINCE MONDAY. NIGHT TIME LOWS
WILL STILL BE BELOW NORMAL, RANGING FROM THE MID TEENS TO NEAR
20 DEGREES.
FOR THURSDAY NIGHT THROUGH AT LEAST THE FIRST HALF OF FRIDAY,
CONDITIONS WILL BE QUITE BREEZY AS THE PRESSURE GRADIENT
STRENGTHENS. NORTHWEST WINDS NEAR 15-20 MPH WITH GUSTS IN THE
30-35 MPH RANGE. THE WINDS WILL PRODUCE SINGLE DIGIT WIND CHILLS
THURSDAY NIGHT, WITH MAXIMUM CHILLS ONLY IN THE 20S ON FRIDAY.
WINDS WILL BE LESSENING FOR FRIDAY NIGHT, BUT STILL A BREEZE
BLOWING WITH WIND CHILLS CLOSER TO 10 DEGREES.
LONG TERM /SATURDAY THROUGH TUESDAY/
SUMMARY...THE COLD EASES AS IT TURNS MILDER OVER THE WEEKEND
AND ESPECIALLY EARLY NEXT WEEK.
SYNOPTIC OVERVIEW...AN UPPER-LEVEL TROUGH SHIFTS TO OUR EAST
LATER FRIDAY WITH SOME WEAK RIDGING BRIEFLY SLIDING ACROSS OUR
AREA. A SHORTWAVE TROUGH THEN MOVES THROUGH SATURDAY, FOLLOWED
BY ANOTHER UPPER-LEVEL TROUGH POTENTIALLY ARRIVING DURING EARLY
NEXT WEEK. AT THE SURFACE, HIGH PRESSURE BUILDS OVER OUR AREA
LATER FRIDAY INTO SATURDAY BEFORE WEAKENING AND SHIFTING TO OUR
SOUTHWEST. A WEAK COLD FRONT OR SURFACE TROUGH MAY MOVE THROUGH
SATURDAY NIGHT INTO SUNDAY. LOW PRESSURE MOVING ACROSS THE GREAT
LAKES MONDAY INTO TUESDAY SHOULD PULL A WARM FRONT TO OUR
NORTH, WITH A SURFACE TROUGH OR WEAK COLD FRONT APPROACHING FROM
THE WEST DURING TUESDAY.
FOR SATURDAY AND SUNDAY...THE FLOW ALOFT IS MORE ZONAL SATURDAY
AND WITH SURFACE HIGH PRESSURE WEAKENING SOME AND SETTLING WELL
TO OUR SOUTHWEST, A SHORTWAVE TROUGH MAY QUICKLY SLIDE ACROSS
OUR AREA SATURDAY NIGHT. SOME GUIDANCE IS A BIT SHARPER WITH
THIS FEATURE AND THEREFORE OFFERS SOME LIGHT PRECIPITATION,
HOWEVER THERE IS SOME UNCERTAINTY WITH THIS. FOR NOW, OPTED TO
KEEP THE FORECAST DRY THROUGH THE WEEKEND. GIVEN THE CORE OF THE
COLD AIR HAS RETREATED WELL TO OUR NORTH AND NORTHEAST, A
MILDER PATTERN WILL RESULT IN HIGH TEMPERATURES INCREASING SOME
EACH DAY WITH WIDESPREAD 40S FORECAST FOR SUNDAY AFTERNOON.
FOR MONDAY AND TUESDAY...AN UPPER-LEVEL TROUGH MAY AMPLIFY
EASTWARD FROM SOUTH-CENTRAL CANADA TO THE OHIO VALLEY. THIS
WOULD SUPPORT SURFACE LOW PRESSURE IN THE VICINITY OF THE GREAT
LAKES REGION AS IT TRACKS EASTWARD. A WARM FRONT SHOULD BE
LIFTING NORTH OF OUR AREA OR ALREADY BE TO OUR NORTH, THEN A
TROUGH OR WEAK COLD FRONT MAY ARRIVE TUESDAY. AS OF NOW THIS
FEATURE MAY BE MORE OF A CLIPPER-TYPE SYSTEM WITH LIMITED
MOISTURE, HOWEVER THERE IS PLENTY OF TIME FOR THIS SCENARIO TO
CHANGE WITHIN THE SUITE OF MODEL GUIDANCE INCLUDING THE NATIONAL
BLEND OF MODELS OUTPUT. EITHER WAY, THE PATTERN LOOKS TO FAVOR
A MILDER ONE DURING THIS TIME WITH HIGH TEMPERATURES REACHING OR
TOPPING 50F BOTH AFTERNOONS FOR PORTIONS OF OUR AREA.
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH 12Z...VFR. W-NW GRADUALLY DIMINISHING TO LESS THAN 10
KT. HIGH CONFIDENCE.
TODAY...VFR. W-NW WINDS 5 TO 10 KT. HIGH CONFIDENCE.
TONIGHT...SUB-VFR LIKELY IN SN AT KMIV/KACY. OTHERWISE, VFR.
LIGHT SNOW MAY BE POSSIBLE AT ILG/PHL BUT CONFIDENCE IS LOW ON
THAT. N WINDS 5 TO 10 KT. MODERATE CONFIDENCE.
OUTLOOK...
THURSDAY...SUB-VFR POSSIBLE IN SHOW SHOWERS IN THE AFTERNOON.
NORTHWEST WINDS 10-15 KNOTS WITH 20-25 KNOTS GUSTS.
THURSDAY NIGHT AND FRIDAY...VFR. GRADUALLY DECREASING CLOUD
COVER THURSDAY NIGHT. NORTHWEST WIND GUSTS UP TO 30 KNOTS.
SATURDAY AND SUNDAY...VFR OVERALL WITH LIGHTER WINDS.
MARINE
SMALL CRAFT ADVISORY CONDITIONS IN EFFECT FOR THE OCEAN FOR
MOST OF TONIGHT FOR NW WINDS 15 TO 20 KT WITH 25 TO 30 KT GUSTS.
CONDITIONS SHOULD EVENTUALLY SUBSIDE TO SUB-SCA CRITERIA BY DAY
BREAK CONTINUING THROUGH THIS EVENING. VSBY RESTRICTIONS IN SN
DEVELOP DURING THE AFTERNOON TODAY, ESPECIALLY FOR SOUTHERN
OCEAN WATERS.
OUTLOOK...
THURSDAY...SMALL CRAFT ADVISORY CONDITIONS POSSIBLE DUE TO
NORTHWEST WINDS INCREASING TO 15-20 KNOTS WITH GUSTS UP TO 25
KNOTS.
THURSDAY NIGHT AND FRIDAY...INCREASING NORTHWEST WINDS TO NEAR
20-30 KTS WITH GUSTS OF 30-40 KTS. THE STRONGEST WINDS ARE
EXPECTED TOWARD THE SOUTH, ESPECIALLY ACROSS DELAWARE BAY AND
ADJACENT OCEAN WATERS. THE GALE WATCH WAS UPGRADED TO A GALE
WARNING FOR THESE AREAS FROM THURSDAY EVENING THROUGH FRIDAY
MORNING, AND THE WATCH REMAINS IN EFFECT ELSEWHERE. LIGHT
FREEZING SPRAY LIKELY THURSDAY NIGHT INTO FRIDAY MORNING.
SATURDAY AND SUNDAY...THE CONDITIONS ARE ANTICIPATED TO BE
BELOW SMALL CRAFT ADVISORY CRITERIA.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 6 PM EST
THURSDAY FOR DEZ003-004.
MD...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 6 PM EST
THURSDAY FOR MDZ019-020.
MARINE...GALE WARNING FROM 6 PM THURSDAY TO 10 AM EST FRIDAY FOR ANZ430-
431-453>455.
GALE WATCH FROM THURSDAY EVENING THROUGH FRIDAY MORNING FOR
ANZ450>452.
SYNOPSIS...GORSE
NEAR TERM...COOPER/DEAL
SHORT TERM...STAARMANN
LONG TERM...GORSE/STAARMANN
AVIATION...COOPER/DEAL/GORSE/MPS
MARINE...COOPER/DEAL/GORSE/MPS
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