472
FXUS61 KPHI 190904
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
404 AM EST THU DEC 19 2024
SYNOPSIS
HIGH PRESSURE BRIEFLY RETURNS 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 TONIGHT/
THE COLD FRONT HAS NOW MOVED OFF THE COAST AND PRECIPITATION HAS
CONCLUDED. SKIES ARE BEGINNING TO SCATTER OUT AT THIS HOUR AND
SHOULD BECOME MOSTLY CLEAR BY DAYBREAK. TEMPERATURES ARE MAINLY IN
THE UPPER 30S TO MID 40S AT THIS HOUR AND WILL FALL A FEW MORE
DEGREES BEFORE SUNRISE.
BEHIND THE FRONT, HIGH PRESSURE OVER SOUTHERN ONTARIO WILL MOVE INTO
SOUTHERN QUEBEC LATER TODAY. THIS WILL RESULT IN COOL/DRY NORTHERLY
FLOW AND RATHER BENIGN WEATHER FOR THE DAY TODAY. SOME PASSING HIGH
CLOUDS ARE LIKELY LATER THIS AFTERNOON AS AN IMPULSE ALOFT PASSES
THROUGH, BUT NO PRECIPITATION IS EXPECTED. HIGH TEMPS WILL BE QUITE
SEASONABLE; MAINLY IN THE 40S AREAWIDE WITH 30S ACROSS THE POCONO
PLATEAU.
HEADING INTO TONIGHT, HIGH PRESSURE WILL REMAIN IN CONTROL TO OUR
NORTH, HOWEVER CLOUD COVER WILL STEADILY INCREASE DURING THE
OVERNIGHT HOURS AHEAD OF OUR NEXT WEATHER SYSTEM. LOW TEMPERATURES
WILL BOTTOM OUT IN THE MID TO UPPER 20S/LOW TO MID 30S BEFORE CLOUDS
ARRIVE AND LEVEL TEMPERATURES OFF.
SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
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. TEMPERATURES ARE EXPECTED TO THE
FALL INTO THE TEENS SATURDAY NIGHT AN ARCTIC AIRMASS BEGINS TO TAKE
HOLD ACROSS THE REGION.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
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 TEMPERATURES IN THE TEENS FOR THE POCONOS. TEMPERATURES
WILL THEN CRATER COME SUNDAY NIGHT WITH SINGLE DIGITS FORECASTED FOR
THE HIGHER ELEVATIONS AND THE PINE BARRENS WITH THE URBAN CORRIDOR
AND COASTAL STRIP IN THE LOW-TEENS, MAKING FOR THE COLDEST NIGHT IN
SOME TIME!
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 /09Z THURSDAY THROUGH MONDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS...
REST OF TONIGHT (THROUGH 12Z)...A MIX OF MVFR/VFR CEILINGS EXPECTED.
CEILINGS SHOULD BECOME VFR BY 10Z AT ALL TERMINALS. W-NW WINDS
AROUND 10 KT WITH OCCASIONAL GUSTS UP TO 18-20 KT POSSIBLE. MODERATE
CONFIDENCE.
THURSDAY...VFR EXPECTED UNDER MOSTLY CLEAR SKIES. NW-N WINDS AROUND
8-13 KT, WITH LOCALLY HIGHER GUSTS AROUND MIDDAY. HIGH CONFIDENCE.
THURSDAY NIGHT...MAINLY VFR EXPECTED WITH AN INCREASE IN CLOUDS
LATE. N-NE WINDS AROUND 5 KT. HIGH CONFIDENCE.
OUTLOOK...
FRIDAY THROUGH FRIDAY NIGHT...SUB-VFR LIKELY WITH A CHANCE OF RAIN
AND/OR SNOW.
SATURDAY THROUGH MONDAY...VFR. NO SIGNIFICANT WEATHER EXPECTED.
MARINE
A SMALL CRAFT ADVISORY IS IN EFFECT UNTIL 11 AM THIS MORNING FOR ALL
THE ATLANTIC COASTAL WATERS AND THE DELAWARE BAY.
NORTH-NORTHWEST WINDS AROUND 20 KT WITH GUSTS UP TO 25-30 KT ARE
EXPECTED THIS MORNING WITH SEAS OF 4-5 FEET. WINDS WILL DIMINISH
DURING THE AFTERNOON TO 10-20 KT WHILE SEAS ABATE TO 2-4 FEET.
FOR TONIGHT, NO MARINE HEADLINES ARE EXPECTED. NORTH-NORTHEAST WINDS
AROUND 10-15 KT AND SEAS OF 2-3 FEET.
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 UNTIL 11 AM EST THIS MORNING FOR ANZ430-
431-450>455.
SYNOPSIS...FITZSIMMONS/MJL
NEAR TERM...DESILVA
SHORT TERM...FITZSIMMONS/MJL
LONG TERM...FITZSIMMONS/MJL
AVIATION...DESILVA/MJL
MARINE...DESILVA/MJL
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