138
FXUS61 KPHI 170901
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
401 AM EST MON FEB 17 2025
SYNOPSIS
HIGH PRESSURE BUILDS IN FROM THE WEST FOR THE FIRST HALF OF THE
WEEK. COASTAL LOW PRESSURE MAY AFFECT THE AREA WEDNESDAY NIGHT
THROUGH THURSDAY. HIGH PRESSURE RETURNS TO CLOSE OUT THE NEW
WEEK.
NEAR TERM /THROUGH TUESDAY/
HIGH WIND WARNING WAS CONVERTED TO A WIND ADVISORY FOR MOST
LOCATIONS WITH THE EXCEPTION OF CARBON AND MONROE COUNTIES WHERE
GUSTS TO 60 MPH WILL BE POSSIBLE THROUGH AT LEAST DAY BREAK.
OTHERWISE, PEAK WIND GUSTS THROUGH THE DAY ARE EXPECTED TO BE 40 TO
50 MPH.
WINDS WILL CONTINUE TO SLOWLY SUBSIDE THROUGH TONIGHT AS THE LOW
AND COLD FRONT GET FURTHER AWAY FROM OUR REGION. WE CONTINUE TO SEE
PRESSURE RISES RANGING FROM 2 TO 5 MB PER 3 HR, AND A 50KT+ 850 MB
JET IS EXPECTED TO REMAIN OVER OUR REGION AT LEAST FOR THE FIRST
HALF OF THE DAY. THAT BEING SAID, AS STRONG COLD AIR ADVECTION
CONTINUES, AND THE TEMPERATURE INVERSION BECOMES STRONGER, IT WILL
BE HARDER TO MIX THE STRONGEST WINDS OF THE LOW LEVEL JET DOWN TO
THE SURFACE. THE SURFACE PRESSURE GRADIENT SHOULD FURTHER RELAX
TONIGHT INTO TUESDAY AS A RIDGE BEGINS TO BUILD OVER THE REGION.
THE OTHER BIG STORY OF THIS PERIOD IS GOING TO BE TEMPERATURES. AS
MENTIONED ABOVE, STRONG COLD AIR ADVECTION WILL CONTINUE OVER OUR
REGION. AS A RESULT, MANY AREAS WERE PROBABLY AT OR VERY CLOSE TO
THEIR DAILY HIGH TEMPERATURE FOR TODAY JUST AFTER MIDNIGHT. WIND
CHILL VALUES/APPARENT TEMPERATURE WILL LIKELY BE SEVERAL DEGREES
LOWER THAN THE AIR TEMPERATURE DUE TO THE WINDY CONDITIONS.
OVERNIGHT, WINDS ARE EXPECTED TO STAY UP, AND MID LEVEL CLOUDS MAY
LINGER FOR MOST, IF NOT ALL OF THE NIGHT. CONSEQUENTLY, NOCTURNAL
RADIATIONAL COOLING WILL BE LIMITED. EVEN SO, LOWS IN THE TEENS FOR
MOST PLACES (SINGLE DIGITS FOR HIGHER TERRAIN AREAS) ARE EXPECTED.
WITH THE WIND, WE WILL BE GETTING CLOSE TO BELOW ZERO WIND CHILL
VALUES, BUT CONFIDENCE ISN'T HIGH THAT A COLD WEATHER ADVISORY WILL
BE NEEDED AS IT IS UNCERTAIN HOW STRONG THE WINDS WILL BE BY TONIGHT.
HIGH PRESSURE WILL BE IN CONTROL ON TUESDAY WITH VERY DRY, COLD, AND
BREEZY CONDITIONS.
SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/
HIGH PRESSURE CONTINUES OVER THE REGION TUESDAY NIGHT WITH WELL
BELOW NORMAL TEMPERATURES EXPECTED. GENERALLY ZONAL FLOW ALOFT
SHOULD LEAD TO QUIET SENSIBLE WEATHER WITH WESTERLY FLOW
EVENTUALLY BECOMING NORTHERLY BY WEDNESDAY EVENING. THE WEST
NORTHWEST FLOW COMBINED WITH THE COLD TEMPERATURES WILL LEAD TO
WIND CHILLS ON TUESDAY EVENING AS LOW AS THE MID TEENS BELOW 0
FOR THE HIGHER ELEVATIONS OF THE POCONOS AND IN THE SINGLE
DIGITS ACROSS THE REST OF SOUTHEASTERN PA, NJ AND THE DELMARVA
PENINSULA.
BY WEDNESDAY AFTERNOON HIGH PRESSURE WILL START TO DEPART AS AN
UPPER LEVEL LOW DEVELOPS SOUTH OF THE GREAT LAKES. THIS WILL RESULT
IN AN INCREASE IN CLOUD COVER OVER THE REGION AHEAD OF A LOW
PRESSURE SYSTEM THAT STARTS TO INITIATE WELL TO OUR SOUTH.
TRENDS IN THE EC ENSEMBLE LOW TRACKS AND GEFS LOW TRACKS CONTINUE TO
SHOW THE MOST LIKELY SCENARIO WITH THE LOW IS THAT IS DEVELOPS WELL
TO THE SOUTH AND DOESN'T STRENGTHEN UNTIL THE LOW IS WELL OFFSHORE.
THE 00Z EC SUBSTANTIALLY JUMPED SOUTH BUT THE EC ENSEMBLE SYSTEM WAS
FAIRLY CONSISTENT WITH A SLIGHT SOUTHERN SHIFT RELATIVE THE TO 18Z
SUITE. GIVEN THAT CONSISTENCY IN A MORE SOUTHERN TRACK, THE FORECAST
HAS BEEN SHIFTED FURTHER SOUTH WITH THE SNOW TOTALS HIGHEST
OVER SOUTHERN DELAWARE. BASED ON THE 17/00Z SUITE OF GUIDANCE,
SNOW IS STILL FORECAST TO MOVE OVER PORTIONS OF CENTRAL AND
SOUTHERN JERSEY HOWEVER IF THE 00Z EC PANS OUT, WE MAY SEE A
MOSTLY DRY EVENT.
LONG TERM /THURSDAY THROUGH SUNDAY/
WHILE THE STRONGEST FORCING FOR SNOW WILL BE DURING THE
OVERNIGHT HOURS WEDNESDAY NIGHT INTO THURSDAY MORNING, GUIDANCE
DOES POINT TO A REINFORCING SHOT OF COLD AIR AS THE UPPER LEVEL
CLOSED LOW DIGS INTO THE MID ATLANTIC. THIS SHOULD LEAD TO SOME
LIGHT SHOW FOR PORTIONS OF THE REGION WITH THE SNOW CLEARING
THROUGH THE DAY. BEHIND THE SYSTEM CONDITIONS ACROSS THE MID
ATLANTIC SHOULD BE FAIRLY BENIGN WITH A GRADUAL WARMING TREND
FROM BELOW NORMAL ON THURSDAY TOWARDS NEAR NORMAL SUNDAY AND
MONDAY.
HIGH PRESSURE BUILDS IN FROM THE WEST BEHIND THE DEPARTING
STORM AND WILL EVENTUALLY BUILD OVER THE AREA BY NEXT WEEKEND.
TEMPERATURES WILL SEE A A GRADUAL WARMING TREND FROM AROUND 10
DEGREES BELOW NORMAL ON THURSDAY TOWARDS NEAR NORMAL SUNDAY AND
MONDAY.
AVIATION /09Z MONDAY THROUGH FRIDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
THROUGH TODAY...VFR WITH SCATTERED TO BROKEN MID LEVEL CLOUDS
BETWEEN 4000 AND 6000 FT AGL. WESTERLY WINDS GUSTING NEAR 40KT
ESPECIALLY EARLY IN THE DAY.
TONIGHT...VFR. WESTERLY WINDS GRADUALLY DIMINISHING.
OUTLOOK...
TUESDAY...VFR.
WEDNESDAY THROUGH THURSDAY...SUB-VFR LIKELY IN SN. IMPROVING
CONDITIONS THURSDAY AFTERNOON.
THURSDAY NIGHT THROUGH FRIDAY...VFR.
MARINE
WINDS HAVE BEGUN TO DIMINISH SLOWLY. CONSEQUENTLY, THE STORM WARNING
WAS CONVERTED TO A GALE WARNING. GALES SHOULD CONTINUE AT LEAST
THROUGH THE DAY TIME HOURS TODAY. MAY SEE GALES CONTINUE INTO THE
OVERNIGHT, ESPECIALLY FOR THE COASTAL WATERS ADJACENT TO CENTRAL AND
NORTHERN NEW JERSEY, BUT CONFIDENCE IS LOWER IN HOW LONG THEY WILL
LINGER. ONCE WINDS DROP BELOW GALE FORCE, EXPECT SCA CONDITIONS TO
LINGER THROUGH THE DAY ON TUESDAY.
THE OTHER TWO WEATHER CONCERNS FOR MARINE NAVIGATION ARE FREEZING
SPRAY (PRIMARILY TONIGHT INTO TUESDAY) AND LOW WATER AT THE TIMES OF
LOW TIDE (THROUGH TUESDAY).
OUTLOOK...
TUESDAY AND TUESDAY NIGHT...GENERALLY SCA CONDITIONS WITH A
CHANCE FOR FREEZING SPRAY DUE TO THE STRONG WINDS AND COLD AIR
TEMPERATURES SPREADING OVER THE WATERS.
WEDNESDAY THROUGH WEDNESDAY NIGHT...SUB-SCA CONDITIONS. VSBY
RESTRICTIONS IN SN STARTING WEDENSDAY AFTERNOON.
THURSDAY THROUGH THURSDAY NIGHT...SCA CONDITIONS. VSBY
RESTRICTIONS IN SN THROUGH THURSDAY AFTERNOON.
FRIDAY...LINGERING SCA CONDITIONS POSSIBLE INTO FRIDAY
AFTERNOON.
PHI WATCHES/WARNINGS/ADVISORIES
PA...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR PAZ060>062-070-
071-101>106.
HIGH WIND WARNING UNTIL 6 PM EST THIS EVENING FOR PAZ054-055.
NJ...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR NJZ001-007>010-
012>027.
DE...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR DEZ001>004.
MD...WIND ADVISORY UNTIL 6 PM EST THIS EVENING FOR MDZ012-015-019-
020.
MARINE...GALE WARNING UNTIL 6 PM EST THIS EVENING FOR ANZ430-431-
453>455.
GALE WARNING UNTIL 6 AM EST TUESDAY FOR ANZ450>452.
LOW WATER ADVISORY UNTIL 8 AM EST THIS MORNING FOR ANZ450.
SYNOPSIS...MPS
NEAR TERM...JOHNSON
SHORT TERM...DEAL
LONG TERM...DEAL
AVIATION...DEAL/JOHNSON/MPS
MARINE...DEAL/JOHNSON/MPS
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