227  
FXUS61 KPHI 231137  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
637 AM EST THU NOV 23 2017  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL BUILD BUILD ACROSS THE EAST COAST TODAY  
THROUGH EARLY FRIDAY, BEFORE SHIFTING OFFSHORE LATER ON FRIDAY.  
A COLD FRONT IS FORECAST TO MOVE ACROSS THE AREA DURING THE DAY  
SATURDAY. HIGH PRESSURE BUILDS ACROSS THE REGION MONDAY, THEN  
OFFSHORE AND TO OUR SOUTH MONDAY NIGHT INTO TUESDAY. A COLD  
FRONT IS EXPECTED LATER TUESDAY INTO WEDNESDAY, THOUGH  
PRECIPITATION MAY DRY OUT BEFORE REACHING THE EAST COAST.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
CENTER OF THE SURFACE HIGH WILL SETTLE IN JUST SOUTH OF OUR  
REGION. IN THE MID AND UPPER LEVELS, A WEAK SHORT WAVE TROUGH  
WILL APPROACH FROM THE WEST. HOWEVER, THANKS TO A VERY DRY  
BOUNDARY LAYER, THIS WILL HAVE LITTLE IMPACT ASIDE FROM  
INCREASING CLOUDS LATE IN THE DAY.  
 
STAYED VERY CLOSE TO THE PREVIOUS FORECAST WITH HIGHS RANGING  
FROM THE UPPER 30S TO UPPER 40S.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/
 
 
THE SURFACE HIGH WILL REMAIN IN PLACE, LEADING TO CONTINUED  
LIGHT WINDS. THUS, DESPITE SOME MID AND HIGH CLOUDS THROUGH THE  
EVENING, EXPECT EFFICIENT RADIATIONAL COOLING CONDITIONS.  
THEREFORE, FOR LOW TEMPERATURES WENT ON THE LOWER SIDE OF  
GUIDANCE, WITH LOWS RANGING FROM THE LOWER 20S TO LOWER 30S.  
 

 
   
LONG TERM /FRIDAY THROUGH WEDNESDAY/
 
 
FAIRLY QUIET WEATHER IS CONTINUES FOR MOST OF THE EXTENDED  
PERIOD THROUGH NEXT WEDNESDAY, WITH A CHANCE OF ISOLATED SHOWERS  
THIS WEEKEND.  
 
HIGH PRESSURE WILL BE IN PLACE EARLY FRIDAY, BEFORE SHIFTING  
OFFSHORE THROUGH THE DAY. DRY WEATHER IS EXPECTED TO CONTINUE  
ACROSS THE REGION FRIDAY AND FRIDAY NIGHT. TEMPERATURES ARE  
FORECAST TO WARM BACK TO NEAR OR SLIGHTLY ABOVE NORMAL FRIDAY.  
 
A COLD FRONT IS EXPECTED TO MOVE ACROSS THE AREA DURING THE DAY  
SATURDAY. MODELS DO NOT HAVE A SIGNIFICANT AMOUNT OF  
PRECIPITATION FORECAST WITH THIS FRONTAL PASSAGE. BUT PW VALUES  
DO APPROACH ONE INCH, AND THERE IS SOME ENHANCED LOW-MID LEVEL  
MOISTURE FORECAST AS THE SHORT WAVE/VORTICITY IMPULSE AND COLD  
FRONT MOVE ACROSS THE AREA. SO WE WILL KEEP A SLIGHT CHANCE OF  
SHOWERS IN THE FORECAST DURING THE DAY SATURDAY.  
 
NORTHWEST FLOW DEVELOPS ACROSS THE AREA BEHIND THE FRONT  
OVERNIGHT FOR SATURDAY NIGHT INTO SUNDAY. IT IS POSSIBLE THAT  
SOME ISOLATED LAKE EFFECT SHOWERS/FLURRIES COULD MAKE THEIR WAY  
ACROSS OUR AREA SATURDAY NIGHT INTO EARLY SUNDAY MORNING IN THE  
NORTHWEST FLOW. AS USUAL, THE POCONOS HAVE THE BETTER CHANCE OF  
ANY SHOWERS. HOWEVER, THE FLOW FROM THE GREAT LAKES GETS CUT OFF  
DURING THE DAY SUNDAY, SO ANY SHOWERS ARE EXPECTED TO END  
DURING THE MORNING.  
 
TEMPERATURES REMAIN ABOVE NORMAL SATURDAY BEFORE THE FRONT  
MOVES THROUGH THE AREA, BUT FALLS BACK TO NEAR NORMAL OR  
SLIGHTLY BELOW FOR SUNDAY.  
 
BY SUNDAY NIGHT, HIGH PRESSURE BEGINS TO APPROACH FROM THE WEST  
THEN FULLY BUILDS ACROSS THE AREA MONDAY. THE FRONT THEN PUSHES  
OFFSHORE AND TO OUR SOUTH MONDAY NIGHT INTO TUESDAY. THIS WILL  
BRING DRY WEATHER BACK TO THE AREA EARLY NEXT WEEK. TEMPERATURES  
ARE EXPECTED TO BE WARM BACK TO ABOVE NORMAL MONDAY THROUGH  
TUESDAY AS RETURN FLOW DEVELOPS.  
 
A COLD FRONT IS FORECAST TO MOVE ACROSS THE AREA TUESDAY NIGHT  
INTO WEDNESDAY. MOISTURE ASSOCIATED WITH THIS FRONT IS EXPECTED  
TO DISSIPATE AS IT APPROACHES OUR AREA AND THE FRONTAL PASSAGE  
MAY END UP BEING PRECIPITATION FREE. EVEN WITH THE FRONTAL  
PASSAGE, TEMPERATURES ARE FORECAST TO BE ABOVE NORMAL INTO  
WEDNESDAY.  
 

 
   
AVIATION /12Z THURSDAY THROUGH MONDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
TODAY...VFR CONDITIONS EXPECTED WITH INCREASING MID AN UPPER  
LEVEL CLOUDS AFTER 18Z. NORTHWESTERLY WINDS WILL SLOWLY BACK TO  
WESTERLY. HOWEVER, WIND SPEEDS ARE GENERALLY EXPECTED TO BE 10  
KT OR LESS. HIGH CONFIDENCE ON ALL ASPECTS OF THE FORECAST.  
 
TONIGHT...VFR CONDITIONS EXPECTED WITH ONLY SOME MID TO UPPER  
LEVEL CLOUDS. WINDS WILL GENERALLY BE WESTERLY AT 5 KT OR LESS,  
BUT COULD BECOME LIGHT AND VARIABLE. HIGH CONFIDENCE ON ALL  
ASPECTS OF THE FORECAST.  
 
OUTLOOK...  
 
FRIDAY-FRIDAY NIGHT...VFR EXPECTED. WESTERLY WINDS THURSDAY-  
EARLY FRIDAY. BECOMING SOUTHWEST LATER FRIDAY INTO FRIDAY NIGHT.  
HIGH CONFIDENCE.  
 
SATURDAY-SUNDAY...GENERALLY VFR. ISOLATED SHOWERS POSSIBLE  
WHICH MAY OCCASIONALLY LOWER CONDITIONS. SOUTHWEST WINDS EARLY  
SATURDAY, BECOMING WEST TO NORTHWEST AND GUSTING 20-25 KNOTS  
SATURDAY NIGHT INTO SUNDAY. MODERATE CONFIDENCE ON SHOWERS AND  
SUB-VFR CONDITIONS, HIGH CONFIDENCE ON WINDS.  
 
SUNDAY NIGHT-MONDAY...VFR EXPECTED. HIGH CONFIDENCE.  
 

 
   
MARINE
 
 
ALTHOUGH GUSTS NEAR OR ABOVE 20 KT WILL BE POSSIBLE THROUGH THE  
MORNING HOURS, WINDS AND SEAS ARE EXPECTED TO STAY BELOW SMALL  
CRAFT ADVISORY CRITERIA TODAY AND TONIGHT.  
 
OUTLOOK...  
 
FRIDAY-SATURDAY...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED,  
ALTHOUGH SEAS MAY BE AROUND 4 FEET AT TIMES FRIDAY NIGHT INTO  
SATURDAY.  
 
SATURDAY NIGHT-SUNDAY NIGHT...SMALL CRAFT ADVISORY CONDITIONS  
LIKELY BEHIND COLD FRONTAL PASSAGE.  
 
MONDAY...CONDITIONS FALLING BELOW SMALL CRAFT ADVISORY LEVELS.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...NONE.  
DE...NONE.  
MD...NONE.  
MARINE...NONE.  
 

 
 

 
SYNOPSIS...ROBERTSON  
NEAR TERM...JOHNSON  
SHORT TERM...JOHNSON  
LONG TERM...ROBERTSON  
AVIATION...JOHNSON/ROBERTSON  
MARINE...JOHNSON/ROBERTSON  
 
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