630
FXUS61 KPHI 191932
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
232 PM EST THU DEC 19 2024
SYNOPSIS
HIGH PRESSURE BRIEFLY RETURNS TODAY 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/
230 PM...AS OF THIS TIME, HIGH PRESSURE CENTERED OVER EASTERN
ONTARIO INTO WESTERN QUEBEC CONTINUES TO DOMINATE OUR WEATHER
HOWEVER WE ARE STARTING TO SEE SOME HIGH CLOUDS STREAMING IN
ACROSS PARTS OF THE AREA AHEAD OF THE NEXT SYSTEM. THIS HAS BEEN
IN ADDITION TO SOME STRATO CU WE'VE HAD AROUND. SO ALL IN ALL,
A BLEND OF SUN AND CLOUDS ACROSS THE REGION THIS AFTERNOON WITH
SEASONABLE TEMPERATURES.
AS WE GO INTO TONIGHT, HIGH PRESSURE CENTERED NORTH OF US WILL
CONTINUE TO DRIFT NORTH AND EAST THROUGH QUEBEC WHILE AN UPPER LEVEL
TROUGH WILL BE DIGGING TOWARDS THE EAST COAST. THE INITIAL SURFACE
LOW WITH THIS SYSTEM WILL BE MOVING THROUGH THE MIDWESTERN STATES
WHILE A SECONDARY LOW WILL BEGIN TO TAKE SHAPE BY MORNING NEAR THE
CAROLINA COAST. IT SHOULD STAY MAINLY DRY ACROSS OUR AREA THROUGH
TONIGHT WITH THE BIGGEST CHALLENGE BEING THE SKY COVER AND
TEMPERATURE FORECAST. THE OVERALL TREND WILL BE TOWARDS AN
EVENTUALLY THICKENING AND LOWERING OF THE CLOUD DECK BY MORNING
HOWEVER THROUGH THIS EVENING, IT MAY JUST BE MAINLY HIGH CLOUDS
ACROSS THE AREA. COMBINED WITH DECREASING WINDS, THIS COULD ALLOW
OUR TEMPERATURES TO DROP OFF FOR A TIME BEFORE THE CLOUDS THICKEN
AND LOWER AND WINDS START TO TURN MORE ONSHORE. CURRENTLY
FORECASTING LOWS FOR TONIGHT MAINLY IN THE 20S TO LOW 30S BUT IF
THERE ARE LESS CLOUDS AROUND THROUGH THE FIRST HALF OF THE NIGHT IT
COULD GET A COLDER THAN THE CURRENT FORECAST. ALSO, NEAR THE COAST
LOWS WILL BE A BIT WARMER DUE TO THE WINDS TURNING ONSHORE WITH LOWS
FORECAST HERE TO GENERALLY BE IN THE 35 TO 40 DEGREE RANGE.
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 THURSDAY/
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 /20Z THURSDAY THROUGH TUESDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS...
TODAY...VFR EXPECTED UNDER MOSTLY CLEAR SKIES. NW-N WINDS
AROUND 8-13 KT, WITH LOCALLY HIGHER GUSTS AROUND MIDDAY. HIGH
CONFIDENCE.
TONIGHT...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
THE SMALL CRAFT ADVISORY WAS ALLOWED TO EXPIRE AT 11 AM. IT
WILL STILL BE A BIT BREEZY INTO THIS AFTERNOON BUT THE
CONDITIONS WILL REMAIN BELOW SCA LEVELS.
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...NONE.
SYNOPSIS...FITZSIMMONS/MJL
NEAR TERM...FITZSIMMONS
SHORT TERM...FITZSIMMONS/MJL
LONG TERM...FITZSIMMONS/MJL
AVIATION...DESILVA/MJL
MARINE...DESILVA/FITZSIMMONS/MJL
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