622
FXUS61 KPHI 190201
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
901 PM EST SAT JAN 18 2025
SYNOPSIS
A COLD FRONT WILL PUSH SOUTH AND EAST INTO THE AREA LATE
TONIGHT BEFORE A LOW PRESSURE SYSTEM DEVELOPS ALONG IT AND LIFTS
NORTH AND EAST UP THE COAST SUNDAY INTO SUNDAY NIGHT.
THEREAFTER, A BITTERLY COLD AIRMASS BUILDS IN THROUGH THE MIDDLE
OF NEXT WEEK.
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
AS OF 9:00PM...CONTINUING TO OBSERVE VISIBILITIES FALLING IN
LOCALIZED AREAS AS AREAS OF PATCHY FOG HAVE DEVELOPED EARLY
THIS EVENING, PRIMARILY OVER NEW JERSEY AND EASTERN PENNSYLVANIA.
DUE TO THE RATHER COLD GROUND, WARM AIR ABOVE AND SOME LEFTOVER
MOISTURE FROM EARLIER, THIS HAS ADDED THE POTENTIAL FOR SOME
LOCALIZED FOG TONIGHT. WE'LL CONTINUE TO MONITOR TRENDS THROUGH
THE NIGHT, BUT EXPECT AS THE WINDS INCREASE AND SHIFT TO MORE
NORTHWEST, THE FOG POTENTIAL SHOULD DECREASE. FOR NOW, HAVE
ADDED THE MENTION OF PATCHY FOG INTO THE GRIDS TONIGHT, BUT
WE'LL HOLD OFF ON ANY DENSE FOG ADVISORIES UNLESS CONDITIONS
WORSEN. OTHERWISE, PREVIOUS DISCUSSION REMAINS BELOW:
AS WE GO INTO TONIGHT, A STRONG COLD FRONT IS FORECAST TO GRADUALLY
SLIDE ACROSS OUR REGION. HOWEVER, LIFT LOOKS RATHER WEAK AND
THEREFORE NO PRECIPITATION IS CURRENTLY FORECAST WITH IT. MORE
CLOUDINESS HOWEVER WILL LINGER AND A LIGHT WIND WILL EVENTUALLY
START TO SHIFT TO THE WEST AND NORTHWEST OVERNIGHT AS THE FRONT
MOVES THROUGH. SOME DRIER AND COLDER AIR WILL THEN START TO SEEP
SOUTH AND EASTWARD THROUGH THE EARLY MORNING HOURS ON SUNDAY.
TEMPERATURES ARE FORECAST TO DROP BELOW FREEZING ACROSS THE REGION
OVERNIGHT, HOWEVER MOST SURFACES SHOULD BE DRYING OFF BY THEN TO
LIMIT ANY ICY SPOTS. THE PROGRESSION OF THE NEXT APPROACHING WAVE
FOR SUNDAY IS LOOKING SLIGHTLY SLOWER SO THE ENTIRE OVERNIGHT PERIOD
SHOULD BE DRY ACROSS THE REGION.
SHORT TERM /6 AM SUNDAY MORNING THROUGH MONDAY NIGHT/
THE MAIN FOCUS FOR THIS PERIOD REMAINS THE STORM SYSTEM FORECASTED
TO IMPACT THE AREA SUNDAY FOLLOWED BITTERLY COLD AIR IN ITS WAKE
HEADING INTO THE NEW WEEK.
NO WHOLESALE CHANGES TO THE FORECAST FOR SUNDAY. THE OVERALL
SYNOPTIC OVERVIEW REMAINS THE SAME: THERE WILL BE A COLD FRONT
MOVING IN FROM THE NORTH AND WEST THAT WILL TEND TO STALL OUT AS IT
NEARS THE COAST. THIS FRONTAL BOUNDARY WILL STRETCH ALL THE WAY DOWN
INTO THE SOUTHEASTERN STATES AND IT IS ALONG THE BOUNDARY THAT THERE
WILL BE A DEVELOPING LOW LOCATED OVER THE CAROLINAS EARLY SUNDAY
MORNING. MEANWHILE, THERE WILL BE ENERGY ALOFT ROUNDING THE BASE OF
A LARGE AND DEEP LONG WAVE TROUGH SETTING UP OVER THE CENTRAL AND
EASTERN CONUS. AS THIS ENERGY ALOFT INTERACTS WITH THE FRONT AND
DEVELOPING LOW, EXPECT LOW PRESSURE TO MOVE NORTH AND EAST THROUGH
THE DAY SUNDAY WHILE BEGINNING TO DEEPEN. THERE REMAINS, HOWEVER,
DIFFERENCES IN MODEL GUIDANCE REGARDING THE STRENGTH, TRACK,
AND TIMING OF THE LOW, WHICH WILL IMPACT BOTH THE PRECIPITATION
TYPES AND AMOUNTS.
IN THE AREAS THAT SEE ALL SNOW SUCH AS BERKS COUNTY INTO THE LEHIGH
VALLEY NORTH AND NORTHEAST THROUGH THE SOUTHERN POCONOS AND NW NJ, A
WINTER STORM WARNING HAS BEEN ISSUED. WE ARE STILL LOOKING AT THE
POTENTIAL FOR 5 TO 10 INCHES OVER THE AREAS WITH LOCALLY HIGHER
AMOUNTS. SNOWFALL RATES COULD EXCEED 1 INCH PER HOUR SUNDAY
AFTERNOON AS THE SURFACE LOW DEEPENS TO THE EAST AND AN AREA OF MID
LEVEL F-GEN FORCING SETS UP.
MEANWHILE NEAR THE I-95 CORRIDOR, THIS IS WHERE THE FORECAST WILL BE
THE TRICKIEST IN TERMS OF PTYPE. WITH TEMPERATURES RIGHT AROUND IF
NOT JUST ABOVE FREEZING HERE AS THE PRECIP BEGINS, IT MAY ACTUALLY
START AS RAIN BEFORE TURNING OVER TO SNOW AS DYNAMIC AND
EVAPORATIONAL COOLING EFFECTS TAKE HOLD. THEN, AS THE LOW TRACKS UP
THE COAST THROUGH THE DAY, A MIX WITH OR CHANGE BACK TO RAIN OR
SLEET MAY OCCUR IN THE AFTERNOON FOR A TIME BEFORE ANY MIXING FLIPS
BACK TO SNOW BEFORE ENDING SUNDAY EVENING. A WINTER WEATHER ADVISORY
WAS ISSUED FOR THIS AREA. HOWEVER, THE EARLY SIGNALS FROM THE
00Z GUIDANCE SUITE TONIGHT SUGGESTS THAT THE AMPLIFICATION WILL
BE LESS THAN PREVIOUSLY ANTICIPATED SO THIS WOULD RESULT IN A
POTENTIALLY WEAKER SYSTEM, LEADING TO MORE SNOW FURTHER SOUTH
AND EAST. WITH THIS BEING SAID, HAVE SUBTLY UPPED FORECAST
NUMBERS BY ABOUT AN INCH OR SO ACROSS THE COASTAL PLAIN EARLY
THIS EVENING. CONSIDERING THIS, MAY HAVE TO FURTHER EXPAND
WINTER WEATHER ADVISORIES/WINTER STORM WARNINGS FURTHER SOUTH
AND EAST, BUT WE'LL LEAVE THAT FOR THE MID-SHIFT TO HANDLE IN
THE COMING HOURS.
FARTHER SOUTH AND EAST TOWARDS THE COAST, MAINLY RAIN AND MIXED
PRECIPITATION IS FAVORED WITH A BRIEF CHANGEOVER TO SNOW POSSIBLE BY
THE EVENING OR LATER SUNDAY NIGHT. AROUND 1 INCH OR LESS IS
CURRENTLY FORECAST FOR THIS AREA.
IN WAKE OF THE SYSTEM ON SUNDAY NIGHT, WE'LL START TO SEE THE
BEGINNING OF THE COLD AIR MASS TAKE AIM AT THE AREA. SKIES WILL
BEGIN TO GRADUALLY CLEAR LATE SUNDAY NIGHT INTO MONDAY MORNING, AND
WITH A FRESH SNOWPACK IN PLACE, THIS SHOULD RESULT IN LOW
TEMPERATURES FALLING INTO THE SINGLE DIGITS/TEENS FOR MOST OF THE
AREA. WITH A STIFF NORTHWEST WIND FILLING IN ON THE BACKSIDE OF THE
DEPARTING LOW, WE SHOULD SEE WIND CHILLS IN THE SINGLE DIGITS FOR
MOST. MOSTLY CLEAR SKIES WILL BE ON TAP FOR MONDAY AS STRONG
CANADIAN HIGH PRESSURE BUILDS OVER THE NORTHERN PLAINS. HIGH
TEMPERATURES WILL BE LIMITED TO THE TEENS/20S WITH WIND CHILLS IN
THE SINGLE DIGITS AND TEENS. ENHANCED NORTHWEST WINDS COULD POSE A
BLOWING SNOW IN AREAS WHERE HEAVIER SNOWFALL OCCURS. COLD
TEMPERATURES MAY ALLOW ICY AND SLIPPERY CONDITIONS TO PERSIST
EVEN AFTER PRECIPITATION HAS ENDED.
MONDAY NIGHT IS WHEN WE REALLY GET INTO THE DANGEROUSLY COLD WEATHER
WITH COLD WEATHER HEADLINES NEAR CERTAIN. CONTINUING WESTERLY
BREEZES ALONG WITH LOWS IN THE SINGLE DIGITS TO BELOW ZERO, ALL
AREAS LOOK TO SEE SUB ZERO WIND CHILL VALUES WITH WIND CHILLS IN THE
MINUS 10S TO MINUS 20S ACROSS OUR N/W ZONES FROM BERKS COUNTY
THROUGH THE LEHIGH VALLEY INTO THE SOUTHERN POCONOS. THESE
DANGEROUSLY COLD TEMPERATURES COULD RESULT IN IMPACTS TO PEOPLE,
ANIMALS, AND INFRASTRUCTURE. DANGEROUSLY COLD CONDITIONS FOR PEOPLE
AND ANIMALS ARE POSSIBLE RESULTING IN AN INCREASED RISK OF
HYPOTHERMIA AND FROST BITE. FOR INFRASTRUCTURE, IMPACTS COULD
INCLUDE FREEZING WATER PIPES AND HIGH DEMAND FOR HEATING ENERGY.
LONG TERM /TUESDAY THROUGH SATURDAY/
DANGEROUSLY COLD WEATHER WILL CONTINUE TO IMPACT THE AREA THROUGH AT
LEAST THE FIRST PART OF THE LONG TERM AS AN ARCTIC AIRMASS REMAINS
IN PLACE. IN FACT, TUESDAY LOOKS TO BE THE COLDEST DAY. HIGHS ON
TUESDAY WILL RANGE FROM NEAR 10 DEGREES IN THE POCONOS TO THE LOW
20S IN DELMARVA. A WEST TO NORTHWEST WIND KEEPS NOTICEABLE COLD AIR
ADVECTION IN PLACE FROM TUESDAY INTO WEDNESDAY. THE LOWS ON TUESDAY
NIGHT RANGE FROM SLIGHTLY BELOW ZERO IN THE POCONOS TO THE LOW TEENS
IN DELMARVA. WINDS WILL BE ABOUT 5-10 MPH AT NIGHT. WHEN YOU FACTOR
THE TEMPERATURES AND WINDS, THE WIND CHILL VALUES RANGE FROM THE
NEGATIVE TEENS IN THE POCONOS TO NEAR ZERO IN DELMARVA. THESE COLD
CONDITIONS ARE CERTAINLY SOMETHING TO BE MINDFUL OF. WEDNESDAY IS
NOT MUCH IMPROVEMENT WITH HIGHS IN THE SINGLE DIGITS FOR THE POCONOS
AND MOST IN THE TEENS ELSEWHERE.
ALSO, THERE IS SOMETHING ELSE TO MENTION DURING THE TUESDAY INTO
WEDNESDAY TIMEFRAME. THERE IS STILL UNCERTAINTY, BUT LOOKING AT SOME
OF THE MODEL GUIDANCE, THE ECMWF AND CANADIAN HAVE A LOW PRESSURE
SYSTEM BRUSHING THE AREA WHILE THE GFS KEEPS THE LOW OUT TO SEA.
THIS WOULD BE TUESDAY NIGHT INTO WEDNESDAY MORNING. FOR NOW, WENT
WITH A SLIGHT CHANCE TO CHANCE OF SNOW FOR PARTS OF THE AREA WITH
THE HEAVIEST OF SNOW STAYING OFFSHORE. AFTER WEDNESDAY MORNING, WE
TREND DRIER WITH A HIGH PRESSURE SYSTEM IN CONTROL.
BY THE END OF THE LONG TERM PERIOD, TEMPERATURES START TO IMPROVE A
LITTLE EACH DAY FROM THURSDAY THROUGH SATURDAY. ANOTHER LOW PRESSURE
SYSTEM LOOKS TO POTENTIALLY IMPACT THE AREA TOWARDS THE END OF THE
WEEK BUT CONFIDENCE IS QUITE LOW GIVEN THE SPREAD ACROSS MODELS AND
IT BEING TOWARDS THE END OF THE LONG TERM PERIOD.
AVIATION /02Z SUNDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
TONIGHT...LOW VFR CEILINGS OVERALL. SOUTHWEST WINDS NEAR 5 KT
BECOMING LIGHT AND VARIABLE AT TIMES. PATCHY FOG POSSIBLE. BY
06Z, WINDS SHOULD GRADUALLY VEER AND BECOME NORTHWEST AROUND 5-8
KT. LOW CONFIDENCE WITH REGARD TO HEIGHT OVER LOWER CEILINGS.
SUNDAY...SUB-VFR WITH PERIODS OF IFR LIKELY. FOR RDG AND ABE,
SNOW LIKELY. FOR ILG, PHL, PNE, TTN, SNOW MAY MIX AT TIMES WITH
SLEET AND RAIN, BEFORE CHANGING OVER TO SNOW BY 20-22Z. FOR MIV
AND ACY, MAINLY RAIN IS FAVORED THOUGH PRECIP COULD BOTH START
AND END AS SNOW. LOW CONFIDENCE OVERALL.
OUTLOOK...
SUNDAY NIGHT...SUB VFR WITH PERIODS OF IFR LIKELY. ALL TERMINALS
ARE EXPECTED TO TRANSITION TO SNOW BY 00Z. PRECIP WINDS DOWN BY
LATER SUNDAY EVENING WITH A RETURN TO VFR.
MONDAY AND MONDAY NIGHT...VFR. NORTHWEST WIND GUSTS UP TO 25 KNOTS.
TUESDAY...VFR. NORTHWEST WIND GUSTS UP TO 20 KNOTS.
TUESDAY NIGHT THROUGH THURSDAY...SUB-VFR CONDITIONS POSSIBLE.
WATCHING LOW PRESSURE DEVELOPMENT, WHICH COULD BRING WINTER
PRECIPITATION TO THE REGION.
MARINE
CONDITIONS WILL REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA FOR ALL
COASTAL WATERS THROUGH TONIGHT. WINDS 10-15 KNOTS WITH GUSTS UP TO
20 KNOTS AND SEAS OF 2-4 FEET.
OUTLOOK...
SUNDAY...NO MARINE HEADLINES EXPECTED. RAIN AND/OR SNOW LIKELY.
SUNDAY NIGHT THROUGH MONDAY NIGHT...GALES SUNDAY NIGHT (GALE WARNING
IN EFFECT) WITH SCA CONDITIONS LIKELY ON MONDAY.
TUESDAY THROUGH THURSDAY...SCA CONDITIONS NOT CURRENTLY
ANTICIPATED. WATCHING LOW PRESSURE DEVELOPMENT OFFSHORE. SOME
FREEZING SPRAY ACCRETION POSSIBLE AT TIMES DUE TO COMBINATION OF
COLD AIR/WATER TEMPERATURES, GUSTY WINDS, SEAS.
PHI WATCHES/WARNINGS/ADVISORIES
PA...WINTER WEATHER ADVISORY FROM 7 AM SUNDAY TO 1 AM EST MONDAY
FOR PAZ070-071-104-106.
WINTER STORM WARNING FROM 10 AM SUNDAY TO 1 AM EST MONDAY FOR
PAZ054-055-062.
WINTER STORM WARNING FROM 7 AM SUNDAY TO 1 AM EST MONDAY FOR
PAZ060-061-101>103-105.
NJ...WINTER WEATHER ADVISORY FROM 7 AM SUNDAY TO 1 AM EST MONDAY
FOR NJZ016>019.
WINTER STORM WARNING FROM 10 AM SUNDAY TO 1 AM EST MONDAY FOR
NJZ001-007>009.
WINTER WEATHER ADVISORY FROM 10 AM SUNDAY TO 1 AM EST MONDAY
FOR NJZ010-012-015.
DE...WINTER WEATHER ADVISORY FROM 7 AM SUNDAY TO 1 AM EST MONDAY
FOR DEZ001.
MD...WINTER WEATHER ADVISORY FROM 7 AM SUNDAY TO 1 AM EST MONDAY
FOR MDZ012.
MARINE...GALE WARNING FROM 6 PM SUNDAY TO 6 AM EST MONDAY FOR ANZ430-
431-450>455.
SYNOPSIS...FITZSIMMONS
NEAR TERM...AKL/DESILVA
SHORT TERM...DESILVA/FITZSIMMONS/MJL
LONG TERM...GUZZO
AVIATION...AKL/DESILVA/GUZZO/MJL
MARINE...AKL/GUZZO/MJL
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