769
FXUS61 KPHI 250720
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
220 AM EST SUN JAN 25 2026
WHAT HAS CHANGED
SNOWFALL TOTALS WERE NUDGED UP SLIGHTLY, MAYBE AN INCH OR SO IN
MOST SPOTS. IMPACTS REMAIN UNCHANGED. A MAJOR WINTER STORM
CONTINUES TO UNFOLD.
KEY MESSAGES
1. A MAJOR WINTER STORM WILL IMPACT OUR ENTIRE AREA THROUGH
TONIGHT THIS STORM WILL BRING SIGNIFICANT SNOW AND ICE
ACCUMULATIONS TO THE ENTIRE AREA.
2. ARCTIC AIR REMAINS IN PLACE WITH TEMPERATURES BELOW FREEZING
THROUGH NEXT WEEKEND.
DISCUSSION
KEY MESSAGE 1...A MAJOR WINTER STORM WILL IMPACT OUR ENTIRE
AREA THROUGH TONIGHT THIS STORM WILL BRING SIGNIFICANT SNOW AND
ICE ACCUMULATIONS TO THE ENTIRE AREA.
A WINTER STORM THAT HAS RESULTED IN WINTER WEATHER ALERTS FROM
ARIZONA TO MAINE IS FINALLY MOVING INTO OUR REGION THIS MORNING.
A MASSIVE RIBBON OF LARGE SCALE ASCENT ASSOCIATED WITH JET
DYNAMICS AND LOW PRESSURE WILL OVERSPREAD THROUGH THE MORNING.
AS THIS EVENT CONTINUES TO GET UNDERWAY, WARM AIR ADVECTION
AROUND THE 700 MB LEVEL WILL DRIVE INCREASING ASCENT FROM SOUTH
TO NORTH. THIS WILL RESULT IN A QUICKLY EXPANDING SNOW SHIELD
FROM SOUTH TO NORTH AND EAST TO WEST AS THE MORNING GOES ON.
INCOMING IMPRESSIVE 700-850 MB FRONTOGENESIS WILL BRING
INCREASING SNOWFALL RATES FROM SOUTH TO NORTH THIS MORNING INTO
EARLY SUNDAY AFTERNOON. MODEL CROSS SECTIONS SHOW DEEP LIFT
CROSSING THE PRIME SNOW GROWTH AREA FOR ABOUT A 4-7 HOUR WINDOW
FROM SOUTH TO NORTH. IT IS DURING THIS PERIOD OF TIME WHERE THE
SNOW WILL BE FALLING AT LEAST 1-2 INCHES PER HOUR. THIS WILL
RESULT IN QUICK ACCUMULATIONS DURING THE MORNING HOURS, AND
LINGERING INTO THE AFTERNOON HOURS ESPECIALLY NEAR AND
NORTH/WEST OF I-95.
AS ONE SURFACE LOW TRACKS UP THE OHIO VALLEY TODAY WITH ARCTIC
HIGH PRESSURE NEAR NORTHERN NEW ENGLAND, A NEW LOW IS FORECAST
TO DEVELOP OFF THE MID-ATLANTIC COAST. THE TRACK SHOULD END UP
INSIDE THE BENCHMARK (40N, 70 W), WHICH USUALLY BRINGS A MIXED
PRECIPITATION STORM (AND A FORECASTING HEADACHE). THE TRACK
CLOSER TO THE COAST WILL RESULT IN A STRONG EASTERLY JET NEAR
700 MB ADVECTING IN MILDER AIR. THIS MILDER AIR MASS WILL
INITIALLY BE ABOVE THE ARCTIC AIR, HOWEVER CLOSER TO THE COAST
THE MILDER AIR SHOULD WIN OUT AND EDGE SURFACE TEMPERATURES
ABOVE FREEZING FOR A TIME THIS AFTERNOON AND EVENING. ABOVE
FREEZING SURFACE TEMPERATURES SHOULD GET RIGHT UP I- 95/I-295/NJ
TURNPIKE. THIS WILL ALSO TRANSLATE TO SNOW MIXING WITH AND
CHANGING TO SLEET AND THEN FREEZING RAIN, ESPECIALLY FROM I-95
SOUTH AND EAST. HOWEVER, SOME SLEET LOOKS LIKE IT WILL MAKE IT
ALL THE WAY TO NEAR THE I-80 CORRIDOR DURING THE PEAK OF THE
STORM THIS AFTERNOON OR EVENING. CLOSER TO THE COAST, AS LONG AS
SURFACE TEMPERATURES RISE ABOVE FREEZING THEN JUST PLAIN RAIN
OCCURS.
THE FORECAST CHALLENGE CONTINUES TO BE THE EVOLUTION OF THIS
WARM LAYER ALOFT AND THUS THE CHANGING PRECIPITATION TYPES. THIS
TIMING WILL SIGNIFICANTLY DETERMINE HOW MUCH SNOW ACCUMULATES
PRIOR TO ANY MIXING OR CHANGEOVER. THE MODEL SOUNDINGS SHOW THE
WARM LAYER ALOFT INITIALLY BEING NOT ALL THAT DEEP, THEREFORE IF
THE PRECIPITATION INTENSITY IS HEAVY ENOUGH AND LONGER THEN IT
WOULD BE ENOUGH TO COOL THAT LAYER TO KEEP SNOW GOING LONGER.
THIS MAY OCCUR ESPECIALLY THE FARTHER NORTHWEST ONE GOES ACROSS
OUR AREA, HOWEVER THIS IS OF LOWER CONFIDENCE. THERE WILL ALSO
BE A ZONE OF FREEZING RAIN WHERE THE TRANSITION OCCURS, AND THIS
LOOKS TO BE CENTERED RIGHT NEAR THE I-95 CORRIDOR. MESOANALYSIS
WILL BE KEY TO WATCH THIS IN REAL TIME AND MAKE ANY LATE
ADJUSTMENTS IN THE FORECAST AS NEEDED.
NO SIGNIFICANT CHANGES WERE MADE TO THE FORECAST SNOW AND ICE
TOTALS OTHER THAN A SLIGHT UPTICK IN SNOW BY ABOUT AN INCH OR
SO. THIS CHANGE IS MINOR AND WILL RESULT IN NO CHANGE TO THE
IMPACTS. WE ARE STILL HITTING WARNING CRITERIA FOR ALL AREAS AT
THIS POINT AND THEREFORE WILL MAINTAIN THE WINTER STORM WARNINGS
THROUGH TOMORROW MORNING.
SNOW RATIOS WILL BE HIGH TO START GIVEN THE ARCTIC AIR MASS IN
PLACE, HOWEVER THESE WILL THEN DECREASE QUITE A BIT FROM SOUTH
TO NORTH AS THE EVENT CONTINUES TODAY INTO TONIGHT. THIS WILL
CHANGE THE CONSISTENCY OF THE SNOW FROM A DRY AND FLUFFY TYPE TO
A MORE MOIST/WET TYPE. IN AREAS THAT HAVE A MIX OR CHANGE TO
SLEET AND/OR FREEZING RAIN WILL HAVE AN ICE LAYER ON TOP OF THE
SNOW WHICH WILL MAKE CONDITIONS MORE DIFFICULT. NOT A LOT OF
CHANGE REGARDING ICE AMOUNTS FROM FREEZING RAIN. THE AMOUNT OF
FREEZING RAIN REALIZED WILL DEPEND ON SMALL TEMPERATURE CHANGES
ALOFT WHETHER IT IS SLEET OR FREEZING RAIN. THE COMBINATION OF
SNOW, SLEET AND FREEZING RAIN WILL RESULT IN MAJOR IMPACTS
ACROSS THE REGION. THERE IS AN INCREASING CONCERN THAT SOME
AREAS WILL HAVE A PROLONGED PERIOD OF ACCUMULATING SLEET.
THE PRECIPITATION TAPERS OFF SUNDAY EVENING WITH SOME DRIZZLE
OR EVEN FREEZING DRIZZLE POSSIBLE. SOME GUIDANCE HAS HINTED AT
SOME LIGHT SNOW OCCURRING AGAIN SUNDAY NIGHT INTO EARLY MONDAY
MORNING BEFORE ENDING. THIS IS OF LOWER CONFIDENCE, BUT IF IT
WERE TO OCCUR ANY ADDITIONAL AMOUNTS LOOK TO BE ON THE LIGHT
SIDE. NORTHEAST WINDS WILL BE INCREASING SOME DURING SUNDAY AND
WHERE THE SNOW REMAINS DRIER COULD LEAD TO SOME BLOWING AND
DRIFTING SNOW.
KEY MESSAGE 2...ARCTIC AIR REMAINS IN PLACE WITH TEMPERATURES
BELOW FREEZING THROUGH THE START OF NEXT WEEKEND.
A DEEP LONGWAVE TROUGH WILL REMAIN SITUATED OVER THE EASTERN
CONUS THROUGH THE THE START OF NEXT WEEKEND, AND SEVERAL
SHORTWAVES EMBEDDED WITHIN IT WILL BRING SEVERAL REINFORCING
SHOTS OF COLD ARCTIC AIR TO THE REGION. AT THE SURFACE, STRONG
ARCTIC HIGH PRESSURE SETTLES OVER THE NORTHERN GULF COAST
THROUGH WEDNESDAY, WHEREAS A COUPLE OF COLD FRONTS ARE ALSO
PROGGED TO TRACK THROUGH THE AREA AS WELL.
IN WAKE OF DEPARTING LOW COASTAL STORM AND HIGH PRESSURE
BUILDING OVER THE DEEP SOUTH, THE RETURN OF VERY COLD AIR IS
ANTICIPATED TO BEGIN MONDAY NIGHT INTO TUESDAY MORNING. A COLD
FRONT IS THEN PROJECTED TO CROSS THROUGH THE AREA TUESDAY NIGHT
INTO WEDNESDAY MORNING, FOLLOWED BY ANOTHER COLD FRONT WEDNESDAY
NIGHT INTO THURSDAY MORNING. ALL IN ALL, PERIODS OF WINDY
CONDITIONS ARE EXPECTED THROUGHOUT THE WEEK WITH GUSTS UP TO
30-35 MPH AT TIMES. HIGH TEMPERATURES WILL LARGELY REMAIN IN THE
TEENS AND 20S WITH LOWS IN THE SINGLE DIGITS TO EVEN SEVERAL
DEGREES BELOW ZERO THROUGHOUT THE COURSE OF THE WEEK.
AS A RESULT, WIND CHILLS WILL MAINLY RANGE IN THE SINGLE DIGITS
TO TEENS DURING THE DAY. MORE IMPORTANTLY AT NIGHT, WIND CHILLS
WILL BECOME DANGEROUSLY COLD GENERALLY RANGING BETWEEN 0 TO -10
DEGREES IN MOST AREAS. FOR THE AREAS NORTH AND WEST OF I-95 AND
ESPECIALLY IN THE HIGHER TERRAIN WHERE SNOW PACK IS DEEPER,
WIND CHILLS MAY RANGE BETWEEN -10 TO -25 DEGREES AT TIMES.
OVERALL, THIS WILL BE A PROLONGED PERIOD OF COLD WEATHER, WHERE
COLD WEATHER HEADLINES WILL LIKELY BE WARRANTED IN THE COMING
DAYS.
WITH SUCH A LONG DURATION OF BELOW FREEZING TEMPS, DO NOT
EXPECT THE NEW SNOW PACK TO MELT MUCH. ASIDE FOR A SLIGHT CHANCE
OF SNOW ON THURSDAY WITH LOW DEVELOPING OFFSHORE, DRY WEATHER
IS EXPECTED.
AVIATION /07Z SUNDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS...
TODAY... WIDESPREAD IFR/LIFR EXPECTED AS SNOW OVERSPREADS THE
AREA BEFORE DAWN. WARMER AIR ALOFT WILL CHANGE SNOW TO SLEET
THEN FREEZING RAIN AS THE MORNING/AFTERNOON PROGRESSES. THE
LATEST TAFS (06Z) SAW ONLY MINOR TIMING CHANGES TO THE PREVIOUS
FCST. SLOW IMPROVEMENT POSSIBLE AFTER 00Z FROM SW TO NE AS
PRECIP ENDS. LOW CLOUDS WILL LINGER HOWEVER. EAST TO NORTHEAST
WINDS 10 TO 20 KTS. CONFID IN CATEGORY CHANGES IS LOW/MEDIUM.
TONIGHT... PRECIP (-SN OR -DZ) ENDS BUT LOW CLOUDS REMAIN. IFR
PROBABLE BUT LIFR NOT OUT OF THE QUESTION. SLOW IMPROVEMENT IN
CONDITIONS AFTER MIDNIGHT FROM SW TO NE POSSIBLE. WINDS SWITCH
TO NW OVERNIGHT. LOW/MEDIUM CONFID.
OUTLOOK...
MONDAY... EXCEPT FOR SOME MORNING CLOUDS, MAINLY VFR EXPECTED.
A FEW SNOW SHOWERS KMPO VCNTY.
MONDAY NIGHT THRU FRIDAY...GENERALLY VFR EXPECTED THRU THE
PERIOD.
MARINE
THE CONDITIONS CONTINUE TO DIMINISH THIS AFTERNOON AS ARCTIC
HIGH PRESSURE BUILDS NEARBY. AS LOW PRESSURE DEVELOPS NEAR OUR
MARINE AREA DURING SUNDAY, NORTHEASTERLY WINDS WILL INCREASE. A
PERIOD OF GALE FORCE WIND GUSTS LOOK PROBABLE ESPECIALLY FOR THE
NEW JERSEY ATLANTIC COASTAL WATERS. IT MAY BE MORE MARGINAL
SOUTH OF THERE INCLUDING DELAWARE BAY. GIVEN THAT IT IS CLOSE,
WENT AHEAD AND UPGRADED THE GALE WATCH TO A WARNING FOR SUNDAY
INTO SUNDAY EVENING.
OUTLOOK...
MONDAY NIGHT...GALES POSSIBLE ALL WATERS IN THE EVENING,
DIMINISHING LATE TO SCA LEVEL GUSTS. SEAS OF 6-9 FEET. FREEZING
SPRAY POSSIBLE.
TUESDAY THROUGH TUESDAY NIGHT...SCA CONDITIONS PROBABLE. WIND
GUSTS UP TO 20-25 KT AND SEAS OF 3-6 FEET. FREEZING SPRAY
POSSIBLE.
WEDNESDAY THROUGH WEDNESDAY NIGHT...SCA CONDITIONS EARLY
WEDNESDAY, THEN NO HEADLINES ANTICIPATED. WINDS UP TO 25 KTS
EARLY, THEN 20 KT OR LESS AND SEAS OF 2-4 FEET.
THURSDAY THROUGH THURSDAY NIGHT...SCA CONDITIONS PROBABLE
THURSDAY, POSSIBLY REACHING GALES THURSDAY NIGHT. WIND GUSTS UP
TO 25-30 KT DURING THE DAY, INCREASING UP TO 35 KTS AT NIGHT
WITH SEAS OF 2-4 FEET, INCREASING TO 3-6 FEET.
CLIMATE
AN IMPACTFUL WINTER STORM BRINGING SIGNIFICANT SNOW
ACCUMULATIONS TO THE AREA IS EXPECTED TODAY. HERE ARE THE 1-DAY
DAILY RECORD TOTALS FOR TODAY FROM OUR SNOW OBSERVING SITES.
SOME OF THESE COULD BE CHALLENGED.
TODAY'S DAILY SNOWFALL RECORDS
ALLENTOWN (ABE) 10.4" (1988)
AC AIRPORT (ACY) 8.3" (2000)
PHILADELPHIA (PHL) 8.5" (2000)
READING (RDG) 9.0" (1905)
TRENTON (TTN) 14.0" (1905)
WILMINGTON (ILG) 10.0" (2000)
PHI WATCHES/WARNINGS/ADVISORIES
PA...WINTER STORM WARNING UNTIL 1 PM EST MONDAY FOR PAZ054-055-
060>062-070-071-101>106.
NJ...WINTER STORM WARNING UNTIL 1 PM EST MONDAY FOR NJZ001-007>010-
012-015>019-021.
WINTER STORM WARNING UNTIL 7 AM EST MONDAY FOR NJZ013-014-020-
022>027.
DE...WINTER STORM WARNING UNTIL 1 PM EST MONDAY FOR DEZ001>004.
MD...WINTER STORM WARNING UNTIL 1 PM EST MONDAY FOR MDZ012-015-019-
020.
MARINE...GALE WARNING FROM 6 AM THIS MORNING TO 6 PM EST THIS EVENING
FOR ANZ430-431-452>455.
GALE WARNING FROM NOON TODAY TO MIDNIGHT EST TONIGHT FOR
ANZ450-451.
DISCUSSION...HOEFLICH/RCM
AVIATION...OHARA
MARINE...HOEFLICH/RCM
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