988  
FXUS61 KPHI 230904  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
404 AM EST SAT JAN 23 2021  
   
SYNOPSIS
 
 
HIGH PRESSURE CENTERED IN NORTHERN ILLINOIS THIS MORNING WILL  
DRIFT SOUTHEASTWARD AND IT SHOULD PASS OFF THE NORTH CAROLINA  
COAST ON SUNDAY EVENING. WEAKENING LOW PRESSURE IS FORECAST TO  
MOVE FROM MISSOURI ON MONDAY TO THE UPPER OHIO RIVER VALLEY ON  
TUESDAY, AS A SECONDARY LOW SLIDES OFF THE MIDDLE ATLANTIC  
COAST. HIGH PRESSURE IS EXPECTED TO NUDGE INTO OUR REGION FROM  
THE NORTH ON WEDNESDAY. ANOTHER LOW IS ANTICIPATED TO PASS OFF  
THE NORTH CAROLINA COAST ON THURSDAY BEFORE MOVING FARTHER OUT  
TO SEA. HIGH PRESSURE APPROACHING FROM THE WEST IS EXPECTED TO  
BUILD ACROSS OUR REGION ON FRIDAY AND SATURDAY.  
 

 
   
NEAR TERM /THROUGH TONIGHT/
 
 
A COLD DAY IS IN STORE ALONG WITH A GUSTY WIND. A NORTHWESTERLY  
FLOW REGIME FROM THE MIDWEST TO THE NORTHEAST AND MID-ATLANTIC  
REGIONS IS FORECAST TO AMPLIFY SOME IN THE EAST TODAY. THIS IS  
DUE TO STRONG SHORT WAVE ENERGY CARVING OUT MORE OF A TROUGH  
TODAY IN THE NORTHEAST TO MID-ATLANTIC. MEANWHILE, SURFACE LOW  
PRESSURE IS FORECAST TO BE CENTERED IN THE CANADIAN MARITIMES  
WITH SURFACE HIGH PRESSURE BUILDING EAST FROM THE MIDWEST AND  
OHIO VALLEY.  
 
OUR REGION WILL BE BETWEEN THE TWO AFOREMENTIONED SURFACE  
SYSTEMS RESULTING IN A TIGHT PRESSURE GRADIENT. COLD AIR  
ADVECTION INCREASED LAST NIGHT AND THAT CONTINUES FOR MUCH OF  
TODAY, RESULTING IN HIGH TEMPERATURES IN THE 20'S AND 30'S.  
THERE WILL BE A NOTABLE BREEZE MAKING IT FEEL EVEN COLDER, WITH  
WIND CHILL VALUES IN THE TEENS TO LOWER 20S FOR THE BALANCE OF  
THE DAY (0-5F IN THE HIGHER TERRAIN OF THE POCONOS). THE  
FORECAST SOUNDINGS INDICATE A FAVORABLE SETUP FOR DEEPER MIXING  
ESPECIALLY BY MIDDAY WITH WINDS OF 30-40 MPH AVAILABLE TO MIX  
DOWN. THE STRONGEST WINDS MAY OCCUR FROM MID-MORNING THROUGH  
MID-AFTERNOON, THEN SOME RELAXING OF THE PRESSURE GRADIENT AND  
THE COLD AIR ADVECTION WEAKENING SOME WILL RESULT IN LESS MIXING  
LATE IN THE AFTERNOON AND EARLY EVENING. AS A RESULT, THE WINDS  
SHOULD SETTLE AS WE START THIS EVENING.  
 
NORTHWEST FLOW TODAY WILL DIRECT LAKE EFFECT SNOW BANDS TOWARD  
ESPECIALLY NORTHEASTERN PENNSYLVANIA, HOWEVER THE ADVECTION OF  
MUCH DRIER AIR AND A GRADUAL LOWERING INVERSION SHOULD LIMIT THE  
SOUTHEASTWARD EXTENT OF THE BANDS (A FEW FLURRIES STILL AROUND  
VERY EARLY THIS MORNING IN PARTS OF THE AREA). ANY SNOW SHOWERS  
OR FLURRIES PARTICULARLY IN THE POCONO REGION MAY END UP BEING  
CONFINED TO THIS MORNING AS A RESULT.  
 
FOR TONIGHT, SURFACE HIGH PRESSURE BUILDS CLOSER HOWEVER IT IS  
NOT FORECAST TO SETTLE RIGHT OVER OUR REGION AND THEREFORE WE  
REMAIN IN AN AREA OF AN ESTABLISHED PRESSURE GRADIENT. DESPITE  
THIS, AT LEAST SOME DECOUPLE OF THE WINDS SHOULD OCCUR TONIGHT  
ESPECIALLY OUTSIDE OF THE HIGHER TERRAIN AS AN INVERSION  
STRENGTHENS SOME. THE EXTENT OF THE WINDS WILL HAVE AN IMPACT ON  
TEMPERATURE TRENDS TONIGHT, BUT EITHER WAY MANY AREAS ARE  
FORECAST TO DROP INTO THE TEENS TONIGHT (WIND CHILLS STILL IN  
PLAY WITH SOME WIND CONTINUING).  
 

 
   
SHORT TERM /SUNDAY THROUGH TUESDAY/
 
 
SURFACE HIGH PRESSURE SLIDING TO OUR SOUTHWEST AND SOUTH WILL  
LIKELY BRING COLD DRY WEATHER TO OUR REGION FOR SUNDAY AND  
SUNDAY NIGHT. DEVELOPING WARM ADVECTION ALOFT IS EXPECTED TO  
BRING AND INCREASE IN MID AND HIGH LEVEL CLOUDS FROM SUNDAY  
AFTERNOON INTO SUNDAY EVENING.  
 
AN INITIAL MID LEVEL SHORT WAVE IS FORECAST TO BE EJECTED OUT  
OF THE SOUTHWESTERN STATES OVER THE WEEKEND. IT SHOULD REACH THE  
CENTRAL GREAT PLAINS ON MONDAY AND THE EASTERN GREAT LAKES LATE  
ON TUESDAY. A WEAKENING SURFACE LOW IS EXPECTED TO PRECEDE THE  
FEATURE WITH A SECONDARY LOW DEVELOPING IN THE VIRGINIA AND  
NORTH CAROLINA VICINITY BEFORE SLIDING OFF THE COAST AND OUT TO  
SEA ON MONDAY NIGHT AND TUESDAY.  
 
PRECIPITATION IN ADVANCE OF THE COMPLEX SYSTEM SHOULD BEGIN TO  
SPREAD INTO OUR REGION FROM THE SOUTHWEST ON MONDAY AFTERNOON.  
THE PRECIPITATION WILL LIKELY CONTINUE INTO MONDAY NIGHT BEFORE  
GRADUALLY LOSING SUPPORT ALOFT ON TUESDAY AND AND SLOWLY  
DISSIPATING.  
 
THE FORECAST TEMPERATURE PROFILES CONTINUE TO SUGGEST MOSTLY  
SNOW FROM THE INTERSTATE 78 CORRIDOR NORTHWARD, MAINLY RAIN FOR  
THE DELMARVA SOUTH OF THE CANAL AND FAR SOUTHERN NEW JERSEY, AND  
A WINTRY MIX FOR AREAS BETWEEN THE TWO.  
 
THE SYSTEM IS NOT ANTICIPATED TO HAVE A GREAT DEAL OF MOISTURE  
ASSOCIATED WITH IT, LIMITING THE SNOW AND SLEET ACCUMULATIONS.  
IT APPEARS AS THOUGH MOST LOCATIONS IN EASTERN PENNSYLVANIA, NEW  
JERSEY AND NORTHERN DELAWARE THAT RECEIVE SNOW WILL FALL IN THE  
1 TO 3 INCH RANGE.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/
 
 
A NORTHERLY WIND IS EXPECTED TO BRING AN END TO ANY LINGERING  
PRECIPITATION ON TUESDAY NIGHT, WITH DRY WEATHER AND SEASONABLE  
TEMPERATURES FOR WEDNESDAY.  
 
THERE REMAINS A FAIR AMOUNT OF VARIABILITY IN THE WAY THAT THE  
DIFFERENT GUIDANCE SOLUTIONS ARE HANDLING THE MAIN MID LEVEL  
TROUGH COMING OUT OF THE SOUTHWESTERN STATES ON TUESDAY. THIS  
CONTINUES TO HAVE IMPLICATIONS ON THE EVENTUAL STRENGTH AND  
TRACK OF ANOTHER SURFACE LOW THAT IS FORECAST TO PASS OFF THE  
NORTH CAROLINA COAST ON THURSDAY. WE WILL KEEP THE MENTION OF A  
CHANCE OF WINTRY PRECIPITATION FOR EASTERN MARYLAND, DELAWARE  
AND SOUTHERN NEW JERSEY AT THAT TIME. DEPENDING ON MODEL TRENDS  
OVER THE COMING DAYS, WE MAY NEED TO EXPAND THE FORECAST OF  
PRECIPITATION A BIT FARTHER TO THE NORTH.  
 
ONCE THURSDAY'S SYSTEM MOVES OUT TO SEA, IT APPEARS AS THOUGH  
HIGH PRESSURE WILL BUILD INTO OUR REGION FROM THE WEST FOR  
FRIDAY AND SATURDAY.  
 

 
   
AVIATION /09Z SATURDAY THROUGH WEDNESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
TODAY...VFR WITH A CEILING BETWEEN 4000-6000 FEET THROUGH AT  
LEAST THIS MORNING, THEN CLOUDS SHOULD DISSIPATE FROM SOUTHEAST  
TO NORTHWEST. NORTHWEST WINDS 15-20 KNOTS WITH GUSTS TO AROUND  
30 KNOTS (STRONGEST WINDS SHOULD BE IN THE 14-21Z TIME FRAME).  
MODERATE CONFIDENCE.  
 
TONIGHT...VFR. NORTHWEST WINDS DIMINISHING TO AROUND 10 KNOTS  
IN THE EVENING. HIGH CONFIDENCE.  
 
OUTLOOK...  
 
SUNDAY...VFR. NORTHWEST WIND 10 TO 15 KNOTS WITH GUSTS AROUND  
20 KNOTS. HIGH CONFIDENCE.  
 
MONDAY...MAINLY VFR. LIGHT WINTRY PRECIPITATION MAY SPREAD INTO  
OUR REGION FROM THE SOUTHWEST DURING THE AFTERNOON. CONDITIONS  
SHOULD DETERIORATE FOR MONDAY EVENING AND MONDAY NIGHT IN SNOW.  
THE SNOW MAY MIX WITH SLEET AND RAIN AT KILG, KMIV AND KACY.  
NORTH TO EAST WIND 5 TO 10 KNOTS. LOW TO MEDIUM CONFIDENCE.  
 
TUESDAY...MVFR AND IFR CONDITIONS IN SNOW AROUND KRDG AND KABE,  
A WINTRY MIX OF PRECIPITATION AT KTTN, KPNE AND KPHL, AND  
MAINLY RAIN AROUND KILG, KMIV AND KACY. NORTHEAST WIND 5 TO 10  
KNOTS. LOW TO MEDIUM CONFIDENCE.  
 
WEDNESDAY...MAINLY VFR. NORTH WIND 5 TO 10 KNOTS. MEDIUM  
CONFIDENCE.  
 

 
   
MARINE
 
 
GALE WARNING INTO THIS EVENING FOR ALL ZONES. THROUGH TONIGHT,  
STRONG NORTHWEST FLOW WILL RESULT IN SURFACE GUSTS TO GALE FORCE  
BEFORE DIMINISHING SOME LATER THIS EVENING FROM SOUTH TO NORTH.  
SOME LIGHT FREEZING SPRAY MAY DEVELOP TONIGHT GIVEN THE GUSTY  
WINDS AND COLDER AIR TEMPERATURES, HOWEVER SINCE WATER  
TEMPERATURES ARE STILL ON THE RELATIVELY MILDER SIDE KEPT ANY  
MENTION AS CHANCE FOR NOW.  
 
OUTLOOK...  
 
SUNDAY...NORTHWEST WIND 15 TO 20 KNOTS WITH GUSTS OF 25 TO 30  
KNOTS.  
 
MONDAY...NO MARINE HEADLINES ARE ANTICIPATED.  
 
TUESDAY...NORTHEAST WIND 15 TO 20 KNOT WITH GUSTS AROUND 25  
KNOTS.  
 
WEDNESDAY...NORTH WIND 10 TO 15 KNOTS WITH GUSTS AROUND 20  
KNOTS. WAVES ON OUR OCEAN WATERS MAY REMAIN AROUND 5 FEET.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...NONE.  
DE...NONE.  
MD...NONE.  
MARINE...GALE WARNING UNTIL 10 PM EST THIS EVENING FOR ANZ430-431-  
450>455.  
 

 
 

 
SYNOPSIS...IOVINO  
NEAR TERM...GORSE  
SHORT TERM...IOVINO  
LONG TERM...IOVINO  
AVIATION...GORSE/IOVINO  
MARINE...GORSE/IOVINO  
 
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