670
FXUS61 KPHI 192035
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
335 PM EST THU DEC 19 2024
SYNOPSIS
HIGH PRESSURE INFLUENCES THE REGION THROUGH TONIGHT. LOW PRESSURE
IMPACTS THE REGION FRIDAY/FRIDAY NIGHT; IMPACTS LASTING POSSIBLY
INTO SATURDAY MORNING. COLD AND STRONG SURFACE HIGH PRESSURE BEGINS
TO BUILD IN LATER SATURDAY, HOLDING INFLUENCE OVER THE REGION
THROUGH MONDAY. NEXT LOW PRESSURE SYSTEM COULD IMPACT THE REGION
MONDAY NIGHT INTO THE WEDNESDAY TIME FRAME.
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
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 /6 AM FRIDAY MORNING THROUGH SATURDAY/
THIS CONTINUES TO BE THE MOST CHALLENGING PART OF THE FORECAST DUE
TO A COMPLEX SYSTEM THAT WILL BE IMPACTING THE AREA FRIDAY THROUGH
EARLY SATURDAY. IN THE UPPER LEVELS, A FAIRLY STRONG, ROBUST UPPER
LEVEL TROUGH WILL CONTINUE TO DIG AS IT MOVES EASTWARD AND BECOMES
CENTERED NEAR THE COAST BY 0Z SATURDAY. AS THIS OCCURS, THE INITIAL
SURFACE LOW ASSOCIATED WITH THIS FEATURE WILL FIZZLE OUT NEAR OHIO
WHILE AS A SECONDARY LOW STRENGTHENS AND MOVES NORTH AND EAST OFF
THE NORTH CAROLINA COAST. ONE OF THE MAIN FORECAST CHALLENGES WILL
BE THE EXACT TRACK THIS LOW TAKES AND WHETHER AN INVERTED SURFACE
TROUGH DEVELOPS ON ITS NW FLANK HELPING FOCUS SOME POTENTIALLY
HEAVIER PRECIPITATION OVER OUR AREA. THERE CONTINUE TO BE SOME
DIFFERENCES IN OUR FORECAST GUIDANCE REGARDING HOW ALL THIS PLAYS
OUT. ALL GUIDANCE INDICATES WE'LL GET AT LEAST SOME PRECIP FROM THE
SYSTEM WITH THE NAM (ESPECIALLY THIS MORNING'S 6Z RUN) DEPICTING THE
LOW BEING FARTHEST WEST CLOSER TO THE COAST THAN OTHER GUIDANCE. THE
OTHER CHALLENGE WILL BE THE MARGINAL TEMPERATURES AROUND THE
FREEZING MARK MAKING FOR A TRICKY PRECIPITATION TYPE FORECAST.
PUTTING ALL THIS TOGETHER IN TERMS OF WHAT IT MEANS FOR OUR SENSIBLE
WEATHER, EXPECT MAINLY LIGHT PRECIPITATION TO BEGIN OVERSPREADING
THE AREA FROM SOUTH TO NORTH THROUGH FRIDAY MORNING WITH THIS
CONTINUING THROUGH THE AFTERNOON. MODERATING TEMPERATURES SHOULD
ALLOW THIS TO BE MAINLY RAIN THROUGH THE DAY NEAR AND SOUTH OF THE I-
95 CORRIDOR WITH MIXED RAIN AND SNOW FARTHER NORTH INTO PORTIONS OF
BERKS COUNTY INTO THE LEHIGH VALLEY AND THEN RUNNING EAST INTO
PORTIONS OF NORTHERN NJ ALONG THE I-78 CORRIDOR. NORTH OF HERE,
PRECIPITATION SHOULD BE MAINLY SNOW ACROSS THE SOUTHERN POCONOS INTO
NW NJ (CARBON AND MONROE COUNTIES IN PA, SUSSEX COUNTY NJ). THESE
AREAS WILL SEE HIGHS ONLY IN THE LOW TO MID 30S WHILE FARTHER SOUTH,
NEAR AND SOUTH OF THE I-95 CORRIDOR, HIGHS GET INTO THE UPPER 30S
AND 40S. BY SUNSET FRIDAY, THERE MAY ALREADY BE SOME SNOW
ACCUMULATION ON THE GROUND NEAR AND NORTH OF THE I-78 CORRIDOR BUT
ESPECIALLY OVER THE HIGHER ELEVATIONS OF THE POCONOS AND NW NJ.
DON'T EXPECT ANY SNOW ON THE GROUND THROUGH THE DAYTIME HOURS
FARTHER SOUTH EVEN IF SOME FLAKES MIX IN AT TIMES.
THE FORECAST GETS A BIT MORE INTERESTING FARTHER SOUTH AS WE HEAD
INTO FRIDAY EVENING AND OVERNIGHT. THE LOW OFFSHORE WILL BE STARTING
TO PULL AWAY FROM THE AREA BUT AS ALLUDED TO ABOVE, THERE MAY BE A
SURFACE TROUGH EXTENDING BACK INTO THE AREA THAT LINGERS KEEPING
PRECIPITATION GOING MUCH OF THE NIGHT. ALSO WINDS WILL BE TURNING
MORE NORTHERLY WHICH, WHEN COMBINED WITH THE DIURNAL CYCLE, WILL
HELP TO COOL TEMPERATURES. THE UPSHOT OF ALL THIS IS THAT I EXPECT
THE RAIN/SNOW TRANSITION ZONE TO SHIFT SOUTHWARD WITH A CHANGE TO
SNOW LIKELY THROUGH THE EVENING ACROSS THE I-95 CORRIDOR AND
EVENTUALLY OVERNIGHT EVEN CLOSER TO THE COAST BEFORE PRECIP STARTS
TO WIND DOWN LATE. IT'S STILL NOT LOOKING LIKE A MAJOR SNOWSTORM FOR
THESE AREAS BUT IN OUR LATEST FORECAST WE ARE INDICATING A COATING
UP TO A HALF INCH OR SO OF ACCUMULATION NEAR THE URBAN
CORRIDOR...SPECIALLY ON GRASSY SURFACES. FARTHER NORTH AND WEST
EXPECT AROUND 1 TO 2 INCHES ACROSS THE LEHIGH VALLEY NORTH AND EAST
INTO NW NJ WITH 2 TO 3 INCHES LIKELY ACROSS THE POCONO PLATEAU. IT
SHOULD CONTINUE TO BE NOTED THOUGH THAT THIS IS A MORE CHALLENGING
FORECAST THAN AVERAGE AND THAT IF PRECIPITATION IS A BIT HEAVIER AND
A CHANGE TO SNOW OCCURS SOONER, AMOUNTS COULD BE HIGHER THAN
CURRENTLY FORECAST... POTENTIALLY 1 TO 2 INCHES IN THE URBAN
CORRIDOR FROM AROUND PHILLY TO TRENTON WITH UPWARDS OF 2 TO 4 INCHES
NORTH OF HERE. EXPECT LOWS BY SATURDAY MORNING MAINLY IN THE UPPER
20S TO LOW 30S EXCEPT LOW TO MID 20S OVER THE POCONO PLATEAU AND THE
HIGHER TERRAIN OF NW NJ.
FOR SATURDAY, DEEPENING LOW PRESSURE CONTINUES TO PULL AWAY FROM THE
AREA WITH A STRONG PRESSURE GRADIENT SETTING UP OVER THE AREA AS AN
ARCTIC HIGH BUILDS IN TO OUR WEST. THE RESULT WILL BE A VERY COLD,
BLUSTERY DAY WITH TEMPERATURES ONLY RISING A FEW DEGREES DUE TO THE
COLD ADVECTION PATTERN. EXPECT ANY LINGERING LIGHT SNOW TO COME TO
AN END THROUGH THE MORNING WITH LITTLE TO NO ADDITIONAL ACCUMULATION
WITH THE MAIN HAZARD BEING STRONG NW WINDS 15 TO 20 GUSTING UP TO 30
MPH. THIS WILL RESULT IN WIND CHILLS A GOOD 10 TO 15 DEGREES COLDER
THAN THE ACTUAL TEMPERATURES SO IN THE TEENS AND 20S!
LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
SURFACE HIGH PRESSURE CENTERED JUST NORTH OF THE GREAT LAKES REGION
SATURDAY NIGHT WILL SLIDE SOUTHEASTWARDS WITH TIME. AS THIS SURFACE
HIGH SHIFTS OFFSHORE OF THE NORTHEASTERN CONUS AROUND THE TIME FRAME
OF MONDAY/MONDAY NIGHT, SURFACE LOW PRESSURE FROM THE WEST IS
INVITED TO APPROACH. A WEAK WARM FRONT ASSOCIATED WITH THE LOW COULD
LIFT THROUGH OUR REGION AFTER THE MONDAY PERIOD WITH A COLD FRONT TO
EVENTUALLY FOLLOW. THIS COLD FRONT COULD END UP PASSING THROUGH
DURING THE TUESDAY/WEDNESDAY TIME FRAME WITH SOME WEAK SURFACE HIGH
PRESSURE POSSIBLY BUILDING IN BEHIND.
COLD AND STRONG SURFACE HIGH PRESSURE WILL CONTROL THE REGION
SATURDAY NIGHT THROUGH AT LEAST MONDAY. THOUGH A FEW LINGERING
FLURRIES AND/OR LIGHT SNOW SHOWERS MAY OCCUR OFFSHORE DURING THE
SATURDAY NIGHT PERIOD, THE REGION IS MAINLY LOOKING AT A DRY AND
COLD FORECAST DURING THE TIME FRAME. THE COLD WILL BE THE MAIN STORY
DURING THE TIME FRAME. OVERNIGHT LOWS SATURDAY NIGHT ARE EXPECTED TO
BE IN THE TEENS ACROSS MUCH OF THE REGION, WITH HIGHS ON SUNDAY
ANTICIPATED TO BE MAINLY IN THE 20S. WITH SURFACE HIGH PRESSURE
CENTERED NEARLY OVERHEAD SUNDAY NIGHT, OVERNIGHT LOWS DURING THE
PERIOD ARE ANTICIPATED TO BE EVEN COLDER THAN THOSE SEEN DURING THE
PREVIOUS NIGHT; SINGLE DIGITS ARE POSSIBLE ACROSS AREAS KNOWN TO
RADIATE WELL AND THOSE LOCATED GENERALLY NORTHWESTWARDS OF THE I-95
CORRIDOR.
LOW PRESSURE AND ASSOCIATED FRONTS COULD BRING SOME PRECIPITATION TO
THE REGION STARTING LATE MONDAY NIGHT ONWARDS, BUT THE FORECAST
REMAINS OVERALL UNCERTAIN THIS FAR OUT GIVEN THE PATTERN.
TEMPERATURES TUESDAY ONWARDS ARE ANTICIPATED TO BE MUCH MORE MILD;
A RETURN TO NEAR AVERAGE CAN BE EXPECTED.
AVIATION /21Z THURSDAY THROUGH TUESDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS...
TONIGHT...VFR EXPECTED. N TO NE WINDS AROUND 5 KT. HIGH CONFIDENCE.
FRIDAY AND FRIDAY NIGHT...DETERIORATING CONDITIONS EXPECTED. VFR TO
START THE DAY FRIDAY, TRANSITIONING TO MVFR BETWEEN 15Z AND 18Z,
AND THEN IFR AROUND 20Z. TERMINALS MAY SEE A TRANSITION BACK TO MVFR
THE SECOND HALF OF FRIDAY NIGHT. RAIN AND SNOW EXPECTED. SNOW
EXPECTED TO START AT KABE AND KRDG DURING THE DAY ON FRIDAY. THE I95
TERMINALS, KMIV, AND KACY WON'T SEE SNOW UNTIL VERY LATE IN THE DAY,
OR MORE LIKELY FRIDAY EVENING. MODERATE CONFIDENCE.
OUTLOOK...
SATURDAY THROUGH MONDAY...AFTER CEILINGS LIFT EARLY ON SATURDAY,
VFR CONDITIONS ARE EXPECTED THROUGH AT LEAST MONDAY NIGHT. NO
SIGNIFICANT WEATHER IS EXPECTED.
TUESDAY...MVFR CONDITIONS POSSIBLE WITH A SYSTEM MOVING IN FROM THE
GREAT LAKES.
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. NORTHEAST WINDS
AROUND 10-15 KT AND SEAS OF AROUND FEET.
NORTHEAST WINDS WILL INCREASE THROUGH THE DAY FRIDAY AND REACH
AT LEAST SMALL CRAFT ADVISORY LEVELS BY FRIDAY NIGHT. THESE
CONDITIONS WILL CONTINUE SATURDAY WITH WINDS SHIFTING TO
NORTHWESTERLY. IT'S POSSIBLE THAT WE COULD EVEN SEE SOME PERIODS
OF GALE FORCE WIND GUSTS FRIDAY NIGHT AND/OR SATURDAY.
OUTLOOK...
SATURDAY NIGHT...SCA FLAG CONTINUES AS CRITERIA LINGERS INTO
THE PERIOD.
SUNDAY THROUGH TUESDAY...NO MARINE HEADLINES ANTICIPATED.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 6 AM SATURDAY TO MIDNIGHT EST
SATURDAY NIGHT FOR ANZ430-431.
SMALL CRAFT ADVISORY FROM 4 PM FRIDAY TO 6 AM EST SUNDAY FOR
ANZ450>455.
SYNOPSIS...WUNDERLIN
NEAR TERM...FITZSIMMONS
SHORT TERM...FITZSIMMONS
LONG TERM...WUNDERLIN
AVIATION...KRUZDLO
MARINE...FITZSIMMONS/WUNDERLIN
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