680
FXUS61 KPHI 182320
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
620 PM EST WED DEC 18 2024
SYNOPSIS
AN AREA OF LOW PRESSURE WITH AN ASSOCIATED COLD FRONT WILL MOVE
THROUGH THE AREA TONIGHT. HIGH PRESSURE BRIEFLY RETURNS ON
THURSDAY AHEAD OF ANOTHER AREA OF LOW PRESSURE WHICH PASSES BY
ON FRIDAY AS SECONDARY LOW PRESSURE DEVELOPS OFFSHORE. IN ITS
WAKE, COLD CANADIAN HIGH PRESSURE ARRIVES FOR THE WEEKEND INTO
EARLY NEXT WEEK. A NEW AREA OF LOW PRESSURE COULD AFFECT THE
AREA BY CHRISTMAS EVE INTO CHRISTMAS DAY.
NEAR TERM /THROUGH THURSDAY/
RAIN HAS SPREAD INTO THE REGION, AND WILL CONTINUE THROUGH THE
NIGHT BEFORE TAPERING OFF PRIOR TO DAYBREAK AS LOW PRESSURE
DRAGS A WARM FRONT NORTH THROUGH THE MID-ATLANTIC AND NORTHEAST.
THIS WILL BE FOLLOWED BY A COLD FRONT AS LOW PRESSURE DEPARTS
AFTER MIDNIGHT TONIGHT.
RAINFALL AMOUNTS IN THE 0.25-0.50 RANGE CAN BE EXPECTED. SOME
SNOW MAY MIX IN ACROSS THE POCONO PLATEAU AND ELEVATIONS OVER
1000FT OVERNIGHT BEFORE PRECIP ENDS, THOUGH MOST ACCUMULATIONS
ARE NOT EXPECTED TO BE MEASURABLE.
NORTHWEST WINDS BEHIND THE COLD FRONT WILL BE A BIT BREEZY
AROUND 10 MPH EARLY THURSDAY MORNING. SOME GUSTS APPROACHING 20
MPH CANNOT BE RULED OUT.
OVERNIGHT LOWS ARE EXPECTED TO FALL INTO THE UPPER 20S TO UPPER
30S, COLDEST ACROSS THE POCONOS, WARMEST ACROSS THE SOUTHERN
COASTAL PLAIN.
HIGH PRESSURE WILL SETTLE OVER SOUTHERN QUEBEC ON THURSDAY. AS
A RESULT, TRANQUIL AND SEASONABLE WEATHER CONDITIONS ARE
EXPECTED. THE REGIONS WILL SEE MOSTLY SUNNY SKIES WITH HIGHS
MAINLY IN THE 40S, 30S IN FAR NW.
SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/
HIGH PRESSURE TO OUR NORTH OVER QUEBEC WILL MAINTAIN CONTROL OVER
THE AREA FOR THURSDAY NIGHT. HOWEVER CLOUD COVER WILL START TO
INCREASE AS THE NEXT SYSTEM APPROACHES...ESPECIALLY BY THE OVERNIGHT
HOURS. THIS WILL MAKE FOR A BIT OF A TRICKY LOW TEMPERATURE FORECAST
AS IT WILL DEPEND ON HOW QUICKLY THE CLOUDS COME IN. CURRENT
FORECAST IS FOR LOWS MAINLY IN THE 20S TO LOW 30S EXCEPT A BIT
WARMER RIGHT NEAR THE COAST AS THE WINDS START TO TURN MORE ONSHORE.
OUR ATTENTION THEN TURNS TO THE FRIDAY THROUGH FRIDAY NIGHT PERIOD
AS OUR NEXT WEATHER SYSTEM TAKES AIM AT THE AREA. A DEEPENING UPPER
TROUGH WILL BE APPROACHING THE AREA TO CLOSE THE WEEK, WHICH WILL BE
ACCOMPANIED WITH SEVERAL SHORTWAVES EMBEDDED IN THE FLOW. AT THE
SURFACE, LOW PRESSURE ORIGINATING OVER THE HIGH PLAINS WILL TRAVERSE
ACROSS THE SOUTHERN GREAT LAKES REGION AND APPROACH OUR REGION BY
FRIDAY AFTERNOON. FORECAST GUIDANCE HAS TRENDED A LITTLE DEEPER WITH
THE PRIMARY SHORTWAVE, SO AS THE LOW APPROACHES, SOME PRECIPITATION
IS EXPECTED TO DEVELOP AND OVERSPREAD THE AREA THROUGH THE DAY
FRIDAY. AT THE SAME TIME, A SECONDARY LOW WILL BE DEVELOPING A
COUPLE HUNDRED MILES OFF THE MID-ATLANTIC COAST AND DEEPEN RAPIDLY
AS IT LIFTS NORTHEAST; ENHANCED BY SPEED MAX ROUNDING BASE OF THE
UPPER TROUGH.
WITH THE LOW OFFSHORE REMAINING IN 'CLOSE ENOUGH' PROXIMITY TO THE
AREA, IT IS LIKELY THAT THERE WILL BE SOME AREAS OF MAINLY LIGHT
RAIN AND SNOW ACROSS THE AREA ON FRIDAY INTO FRIDAY NIGHT AS THE
INITIAL LOW TRANSITIONS ITS ENERGY TO THE OFFSHORE LOW. IN ADDITION,
SOME FORECAST GUIDANCE INDICATES THE DEVELOPMENT OF AN INVERTED /
NORLUN TROUGH SET-UP ON THE NORTHWEST SIDE OF THE OFFSHORE LOW. THIS
WOULD ENHANCE PRECIPITATION ACROSS PORTIONS OF THE AREA, HOWEVER, IT
IS STILL UNCERTAIN WHERE OR IF THIS FEATURE IS TO EVEN DEVELOP AT
THIS TIME. FOR NOW, THE BEST CHANCE OF OBSERVING ACCUMULATING SNOW
WILL BE ACROSS THE LEHIGH VALLEY, NORTHERN NEW JERSEY AND IN THE
POCONOS WHERE TEMPERATURES WILL BE COOLER THROUGH THE DURATION OF
THE EVENT. CURRENT FORECAST SNOW TOTALS IN THESE AREAS ARE FOR
BETWEEN 1-2", LOCALLY UP TO 3". LIGHT ACCUMULATIONS OF A DUSTING UP
TO 1" ARE POSSIBLE ACROSS THE REMAINDER OF NEW JERSEY, PENNSYLVANIA
AND NORTHERN DELAWARE AS RAIN TRANSITIONS TO SNOW ON FRIDAY NIGHT AS
TEMPERATURES COOL BELOW/NEAR FREEZING. IT SHOULD BE NOTED THOUGH
THAT THESE TYPE OF INVERTED TROUGH SETUPS ARE NOTORIOUSLY DIFFICULT
TO FORECAST AS THEY CAN SOMETIMES HAVE LOCALIZED HEAVIER
PRECIPITATION AMOUNTS. IF THIS OCCURS, SOME AREAS COULD
"OVER PERFORM" AND SEE SNOWFALL AMOUNTS AS HIGH AS 4 OR 5 INCHES.
BEST CHANCES FOR THIS WOULD BE CENTRAL INTO NW NJ, NE PA.
PRECIPITATION WILL TAPER OFF FROM WEST TO EAST BY EARLY SATURDAY
MORNING AS THE LOW EXITS TOWARD NOVA SCOTIA. THE REMAINDER OF THE
DAY SATURDAY WILL BE BLUSTERY AND COLD WITH HIGHS RANGING FROM THE
20S TO LOW 30S NORTH WITH MID TO HIGH 30S FOR HIGHS NEAR AND
SOUTH/EAST OF THE I-95 CORRIDOR.
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
BEHIND SATURDAY'S DEPARTING LOW PRESSURE SYSTEM, AN EXPANSIVE AREA
OF ARCTIC HIGH PRESSURE WILL MOVE IN FOR SUNDAY INTO EARLY NEXT
WEEK. SUNDAY'S HIGHS WILL ONLY BE IN THE 20S AREA WIDE WITH SOME OF
OUR COLDER LOCATIONS GETTING DOWN INTO THE SINGLE DIGITS SUNDAY
NIGHT. MONDAY WILL ONLY BE A BIT BETTER THAN SUNDAY AS THE AIRMASS
STARTS TO MODIFY WITH HIGHS GENERALLY RANGING FROM THE MID 20S NORTH
TO THE LOW TO MID 30S SOUTH. A NEW WEATHER SYSTEM WILL BE
APPROACHING THE AREA BY THE CHRISTMAS EVE INTO CHRISTMAS DAY TIME
FRAME AS THE HIGH PRESSURE SYSTEM STARTS TO RETREAT AND TEMPERATURES
MODIFY. THIS CURRENTLY DOES NOT LOOK LIKE A MAJOR SYSTEM BUT COULD
FEATURE A WINTRY MIX FOR PARTS OF THE AREA LIKELY TRANSITIONING TO
MAINLY RAIN CHRISTMAS DAY.
AVIATION /00Z THURSDAY THROUGH MONDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS...
TONIGHT...MVFR, LOWERING TO IFR IN RAIN AND STRATUS. CONDITIONS
IMPROVE TO VFR 06Z AS THE RAIN ENDS AND A COLD FRONT PASSES
THROUGH THE TERMINALS. WINDS BECOME W/NW AROUND 10 KTS AFTER
00Z. GUSTS UP TO 20 KTS TOWARD DAYBREAK. MODERATE CONFIDENCE.
THURSDAY...MAINLY VFR CONDITIONS EXPECTED. HIGH CONFIDENCE.
OUTLOOK...
THURSDAY NIGHT...VFR. NO SIGNIFICANT WEATHER EXPECTED.
FRIDAY THROUGH FRIDAY NIGHT...SUB-VFR LIKELY WITH A CHANCE OF RAIN
AND/OR SNOW.
SATURDAY THROUGH MONDAY...VFR. NO SIGNIFICANT WEATHER EXPECTED.
MARINE
TONIGHT...SCA IN EFFECT FOR THE COASTAL WATERS AND DELAWARE BAY
BEGINNING THE SECOND HALF OF TONIGHT. IT'S MARGINAL WITH SEAS
3-5 FEET AND NW WINDS AROUND 25 KTS.
THURSDAY...AFTER SOME SCA CONDITIONS IN THE MORNING, SUB-SCA
CONDITIONS ARE EXPECTED IN THE AFTERNOON. SEAS MAINLY 3 TO 4
FEET AND WINDS NW 10 TO 20 KTS. GUSTS UP TO 25 KTS IN THE
MORNING.
OUTLOOK...
FRIDAY THROUGH SATURDAY...INCREASING WINDS/SEAS WITH SMALL CRAFT
ADVISORY CONDITIONS LIKELY BY LATE FRIDAY LASTING THROUGH SATURDAY.
WIND GUSTS COULD EVEN APPROACH GALE FORCE BY LATER SATURDAY.
SUNDAY THROUGH MONDAY...SMALL CRAFT ADVISORY MAY LINGER INTO EARLY
SUNDAY HOWEVER WINDS AND SEAS WILL BE DIMINISHING BY THIS TIME. THE
REMAINDER OF SUNDAY AND MONDAY WILL SEE CONDITIONS BELOW SMALL CRAFT
ADVISORY LEVELS.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 1 AM TO 11 AM EST THURSDAY FOR
ANZ430-431-450>455.
SYNOPSIS...FITZSIMMONS
NEAR TERM...KRUZDLO/MPS
SHORT TERM...FITZSIMMONS
LONG TERM...FITZSIMMONS
AVIATION...FITZSIMMONS/KRUZDLO/MPS
MARINE...FITZSIMMONS/KRUZDLO
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