347  
FXUS61 KPHI 241601  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
1101 AM EST TUE JAN 24 2017  
   
SYNOPSIS
 
 
THE COASTAL LOW WILL LIFT NORTHEAST, PASSING EAST OF CAPE COD  
THIS EVENING. A RIDGE BUILDS OVER OUR REGION BRIEFLY TOMORROW. A  
COLD FRONT PASSES SOUTHEASTWARD OFF THE MID ATLANTIC COAST  
THURSDAY FOLLOWED BY A SECOND COLD FRONT MOVING THROUGH OUR  
REGION LATE IN THE WEEKEND.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
THE COASTAL LOW LOCATED OFF THE NEW JERSEY COAST WILL CONTINUE  
TO DRIFT EAST NORTHEASTWARD THROUGH TODAY. THE MID-LEVEL LOW  
LOCATED OFF THE DELMARVA COAST WILL CONTINUE TO MOVE EAST  
NORTHEASTWARD AS WELL. SEVERAL VORTICITY IMPULSES WILL CIRCLE  
AROUND THE TROUGH ALOFT, WHILE LOW-MID LEVEL MOISTURE WILL  
CONTINUE TO WRAP AROUND THE BACKSIDE OF THE SURFACE LOW. THIS  
WILL KEEP PERIODS OF SHOWERS MOVING BACK ACROSS MUCH OF THE ARE  
THROUGH THE DAY.  
 
SEVERAL ASOS STATIONS ACROSS SOUTHERN NEW JERSEY HAVE AT TIMES  
REPORTED -SN MIXING IN THIS MORNING, BUT WITH THEIR TEMPERATURES  
BEING 35-38 AND DEWPOINTS BEING 34-36, IT'S HARD TO BELIEVE  
THIS IS ACTUALLY SNOW AND NOT ASOS HAVING A HARD TIME  
DETERMINING WHAT TO CALL THE -RA OR -DZ THAT IS ACTUALLY  
FALLING. IF THERE IS ANY POTENTIAL FOR SLEET OR SNOW TO MIX IN  
WITH ANY RAIN/DRIZZLE, IT WOULD BE FOR AREAS ALONG AND NORTH OF  
I-78. FURTHER NORTH ACROSS THE HIGHER ELEVATIONS OF  
CARBON/MONROE, PENNSYLVANIA AND SUSSEX, NEW JERSEY WHERE  
TEMPERATURES WILL REMAIN BELOW FREEZING THROUGH TODAY, THERE  
COULD CONTINUE TO BE SOME LIGHT FREEZING RAIN OR DRIZZLE.  
THEREFORE WE'VE KEPT THE WINTER WEATHER ADVISORY IN PLACE.  
 
NORTHWEST WINDS WILL REMAIN GUSTY AT TIMES TODAY WITH GUSTS  
20-30 MPH. THE STRONGEST WINDS CONTINUE TO BE EXPECTED ACROSS  
SOUTHERN AND COASTAL NEW JERSEY, SOUTHEAST PENNSYLVANIA, AND  
MOST OF THE DELMARVA.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/
 
 
AS THE COASTAL LOW BEGINS TO MOVE INTO THE OPEN ATLANTIC EAST OF  
CAPE COD, NORTHWEST FLOW BECOMES ESTABLISHED ACROSS THE REGION  
OVERNIGHT. THE COLUMN WILL DRY RAPIDLY AS THIS OCCURS SHUTTING  
ANY REMAINING PRECIPITATION DOWN QUICKLY. ANTECEDENT OVERCAST  
CONDITIONS WILL LIKELY SCOUR OUT RAPIDLY AFTER DARK. WINDS  
SHOULD CONTINUE TO DIMINISH BUT WILL LIKELY BE ELEVATED ENOUGH  
TO PREVENT IDEAL RADIATIONAL COOLING. TEMPERATURES WILL COOL TO  
THE MID 20S IN THE SOUTHERN POCONOS TO THE MID TO UPPER 30S NEAR  
THE COAST.  
 

 
   
LONG TERM /WEDNESDAY THROUGH MONDAY/
 
 
WEDNESDAY...FOR A BRIEF PERIOD A SHORT WAVE RIDGE WILL BUILD  
OVER OUR REGION. THUS, EXPECT DRY WEATHER THROUGH THE DAY. AS  
THE LOW LEVEL RIDGE AXIS SHIFTS EAST OF OUR REGION THROUGH THE  
LATER HALF OF THE DAY, WE SHOULD SEE SOME WARM AIR ADVECTION.  
 
THURSDAY...THE WARM AIR ADVECTION WILL BE SHORT LIVED HOWEVER,  
AS THE MODELS GENERALLY SPED UP THE TIMING OF THE COLD FRONT,  
WHICH IS NOW EXPECTED TO SWEEP OFF SHORE BY MID DAY THURSDAY.  
ANY OPPORTUNITY FOR PRECIPITATION SHOULD BE BRIEF, GENERALLY  
ALONG OR JUST AHEAD OF THE FRONT, BUT EVEN THAT IS SOMEWHAT  
UNCERTAIN.  
 
FRIDAY THROUGH MONDAY...NORTHWEST FLOW PATTERN DEVELOPS KEEPING  
THE COLD AIR IN PLACE. IN ADDITION, A SECOND COLD FRONT COULD  
ARRIVE IN THE REGION LATE IN THE WEEKEND. IN ADDITION TO COLD  
AIR ADVECTION, THESE NORTHWEST FLOW PATTERNS ALSO TEND TO RESULT  
IN DRY AIR ADVECTION, SO AT THIS POINT DO NOT EXPECT MUCH IN THE  
WAY OF PRECIPITATION EXCEPT POSSIBLY IN THE SOUTHERN POCONOS,  
WHERE SOME LAKE EFFECT SNOW SHOWERS COULD SNEAK DOWN INTO THE  
REGION.  
 

 
   
AVIATION /15Z TUESDAY THROUGH SATURDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
GENERALLY MVFR CIGS ARE EXPECTED THROUGH THE DAY AND INTO THIS  
EVENING, EXCEPT ACROSS CENTRAL AND SOUTHERN NEW JERSEY WHERE  
IFR CIGS COULD CONTINUE WITH CLOUDS WRAPPING AROUND THE COASTAL  
LOW. PERIODS OF SHOWERS AND DRIZZLE WILL ALSO WRAP AROUND THE  
LOW AND AFFECT THE AREA THROUGH TODAY AS WELL UNTIL THE LOW  
SLOWLY PULLS AWAY LATE THIS AFTERNOON AND EVENING. VSBYS IN THE  
RAIN/DRIZZLE WILL VARY FROM MVFR TO IFR IN A FEW LOCATIONS.  
CONDITIONS ARE EXPECTED TO RETURN TO VFR LATER THIS EVENING AND  
OVERNIGHT BUT MAY DETERIORATE BACK TO MVFR AFTER MIDNIGHT AND  
TOWARD DAYBREAK WEDNESDAY, ESPECIALLY FOR KABE/KRDG.  
 
NORTHWEST WINDS GENERALLY 10-15 KTS WITH OCCASIONAL GUSTS 20 TO 25  
KTS ARE EXPECTED THROUGH THE DAY AND INTO TONIGHT. GUSTS MAY  
PERIODICALLY DROP IN AND OUT THROUGH TONIGHT.  
 
OUTLOOK...  
WEDNESDAY...MOSTLY VFR CONDITIONS EXPECTED.  
 
WEDNESDAY NIGHT AND THURSDAY...SMALL CHANCE OF SHOWERS WHICH  
COULD LOWER CONDITIONS TO MVFR. GUSTY WESTERLY WINDS BEHIND A  
COLD FRONT.  
 
FRIDAY AND SATURDAY...MOSTLY VFR CONDITIONS EXPECTED.  
 

 
   
MARINE
 
 
THE GALE WARNING WAS CONTINUED ACROSS THE NORTHERN ATLANTIC  
COASTAL WATERS WHERE IT PREVIOUSLY WAS, AND HAS NOW BEEN ISSUED  
FOR THE REST OF THE ATLANTIC COASTAL WATERS AND LOWER DELAWARE  
BAY THROUGH 1 AM TONIGHT. WHILE WINDS WILL BE BELOW GALE FORCE  
FOR THE NEXT SEVERAL HOURS, GUSTS ARE EXPECTED TO INCREASE BACK  
TO GALE FORCE LATE THIS AFTERNOON AND INTO THIS EVENING AS  
WINDS ABOVE THE SURFACE AND LOW-LEVEL MIXING INCREASES.  
 
OUTLOOK... WEDNESDAY...WINDS SHOULD DIMINISH BELOW SCA CRITERIA  
BY MID DAY. ONCE THEY DO SO, SUB SCA CONDITIONS ARE EXPECTED  
FOR THE REMAINDER OF THE DAY.  
 
THURSDAY THROUGH FRIDAY...WEST WIND GUSTS 25-30 KT POSSIBLE AND  
SEAS COULD BUILD ABOVE 5 FEET.  
 
SATURDAY...WEST WIND GUSTS NEAR OR ABOVE 25 KNOTS POSSIBLE.  
 

 
   
TIDES/COASTAL FLOODING
 
 
THE COASTAL FLOOD WARNING WAS ALLOWED TO EXPIRE AT 11 AM AS TIDE  
LEVELS HAVE CRESTED AND WILL CONTINUE TO FALL THROUGH THIS  
AFTERNOON. THERE MAY CONTINUE TO BE HIGH WATER LEVELS FOR  
ANOTHER HOUR ALONG THE BACK BAY AREAS CAUSING SOME MINOR  
FLOODING.  
 
BASED ON THE FORECAST GUIDANCE AND THE EXPECTED NORTH-NORTHWEST  
WINDS, WE ARE NOT ANTICIPATING ANY ADDITIONAL COASTAL FLOODING  
WITH THE NEXT HIGH TIDE CYCLE THIS AFTERNOON AND EVENING.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR PAZ054-  
055.  
NJ...WINTER WEATHER ADVISORY UNTIL 6 PM EST THIS EVENING FOR NJZ001.  
DE...NONE.  
MD...NONE.  
MARINE...GALE WARNING UNTIL 1 AM EST WEDNESDAY FOR ANZ431-450>455.  
SMALL CRAFT ADVISORY UNTIL 1 AM EST WEDNESDAY FOR ANZ430.  
 

 
 

 
SYNOPSIS...JOHNSON  
NEAR TERM...CMS/ROBERTSON  
SHORT TERM...CMS  
LONG TERM...JOHNSON  
AVIATION...CMS/JOHNSON/ROBERTSON  
MARINE...CMS/GORSE/JOHNSON/ROBERTSON  
TIDES/COASTAL FLOODING...ROBERTSON  
 
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