631  
FXUS61 KPHI 190244  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
944 PM EST THU DEC 18 2014  
   
SYNOPSIS
 
 
A LOW PRESSURE SYSTEM OVER PRINCE EDWARD ISLAND WILL TRACK SLOWLY  
TO THE NORTHEAST. HIGH PRESSURE OVER THE NORTHERN GREAT LAKES  
WILL MOVE INTO THE OHIO VALLEY OVERNIGHT. LOW PRESSURE IS EXPECTED  
TO FORM OVER THE GULF STATES FRIDAY NIGHT AND TRACK ACROSS GEORGIA  
SATURDAY. A COLD FRONT MAY MOVE THROUGH THE EASTERN SEABOARD ON  
CHRISTMAS EVE.  
 

 
   
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
 
 
SINCE THE TRUNDLING CLOSED LOW PRESSURE SYSTEM FROM LAST WEEK, THE  
NORTHEASTERN CONUS HAS NOT BEEN ABLE TO SHAKE THE PLETHORA OF LOW  
CLOUDINESS STUCK UNDERNEATH THE INVERSION, EVEN AFTER CHANGING AIR  
MASSES. TONIGHT SEEMS NOT MUCH DIFFERENT. IN ADDITION, WE DO HAVE  
SOME MID TO HIGH LEVEL CLOUDS MOVING THROUGH OUR CWA ASSOCIATED  
WITH A WEAKENING SHORT WAVE. WHILE 88DS ARE SHOWING PCPN ALOFT,  
NONE IS MAKING IT TO THE GROUND. THE FREEZING SNIZZLE IN UPSTATE  
NEW YORK (DONT RECALL THIS HAPPENING TWICE IN TWO CONSECUTIVE WEEKS)  
APPEARS TO NOT BE GETTING CLOSE TO OUR POCONOS. FOR THE OVERNIGHT  
UPDATE, WE DID INCREASE CLOUD COVER AND BUMPED UP TEMPS,  
ESPECIALLY IN THE NWRN TWO THIRDS OF OUR CWA WHERE WE ARE SOLIDLY  
OVERCAST UPSTREAM. THE SOUTHEASTERN THIRD, THERE ARE SOME LOW  
CLOUDS BREAK, SO KEPT THOSE MINS SIMILAR, BUT SHOWED MORE OF A  
LATE AT NIGHT SPIRAL.  
 

 
   
SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/
 
 
LATEST WRF, RAP SHOWING MORE MOISTURE TRAPPED UNDERNEATH THE  
INVERSION ON FRIDAY WITH CONVECTIVE TEMPS WITHIN REACH. WE MADE IT  
CLOUDIER. LAST WEEK, WE FOUND A WAY TO STILL MAKE MAX TEMPS IN  
SPITE OF THE CLOUDS, SO LEFT THEM THE SAME.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/
 
 
MID-LEVEL FLOW THE NEXT COUPLE OF DAYS IS RATHER FLAT THOUGH A  
CHANGE TO THAT PATTERN APPEARS LIKELY BY THE END OF THE WEEKEND. A  
DEEP TROUGH EMERGES ACROSS THE CENTRAL U.S. BY TUESDAY AS MULTIPLE  
PACIFIC NORTHWEST WAVES ROUND THE BASE OF THE TROUGH AND ACROSS OUR  
REGION...WE ARE HEADING FOR A VERY UNSETTLED PERIOD BY EARLY NEXT  
WEEK.  
 
FRIDAY NIGHT - SATURDAY...LOOKS DRY. FRIDAY SHOULD BE DOMINATED BY  
GREAT LAKES HIGH PRESSURE WHICH SHOULD YIELD PARTY CLOUDY SKIES.  
 
SATURDAY NIGHT AND SUNDAY...AN INVERTED TROUGH MAY THROW BACK SOME  
MOISTURE ACROSS THE AREA AS A WEAK WAVE OF LOW PRESSURE MOVES WELL  
OFFSHORE OF OUR REGION. ONLY HAVE SLIGHT CHANCE POPS ACROSS THE  
NORTHEASTERN PORTION OF THE CWA AS THAT LOOKS LIKE THE MOST  
FAVORABLE LOCATION FOR THE TONGUE TO MOISTURE TO REACH. GIVEN THE  
OVERNIGHT TIMING PRECIP COULD FALL AS RAIN SNOW MIX OR ALL SNOW.  
 
MONDAY - TUESDAY...LOW PRESSURE MOVES OFF THE CAROLINA COAST AND OUT  
TO SEA ON TUESDAY. THIS LOW WILL HELP LIFT A WARM FRONT ASSOCIATED  
WITH A LARGE AND DEVELOPING LOW PRESSURE SYSTEM OVER THE MIDDLE OF  
THE CONUS INTO THE AREA. ONSHORE FLOW AHEAD OF THE SYSTEM AND WARM  
AIR MOVING IN WITH THE FRONT WILL ALLOW FOR A WARMING LOW-LEVEL  
THERMAL PROFILE SO PRECIP SHOULD BE PRIMARILY LIQUID. MID-RANGE  
CHANCE POPS WILL PERSIST MONDAY...MONDAY NIGHT...AND TUESDAY.  
 
WEDNESDAY...STILL WATCHING A LARGE LOW PRESSURE FORM TO OUR WEST AND  
TRACK INTO THE GREAT LAKES REGION ON WEDNESDAY. THIS WOULD KEEP OUR  
REGION UNDER A WARMING THERMAL PROFILE WITH A LOT OF MOISTURE TO  
WORK WITH. WHAT IS INTERESTING WITH THE LATEST MODEL RUNS IS HOW  
THEY ARE SEEMINGLY WEAKENING THE PRIMARY LOW AS IT MOVES INTO THE  
LAKES ALLOWING FOR ANOTHER, STRONGER, PIECE OF PAC NW ENERGY TO  
PRODUCE CYCLOGENESIS ACROSS THE MID-ATLANTIC. IT APPEARS THAT CHRISTMAS  
EVE WL BE A DAY W/ MOISTURE, WINDS, AND POSSIBLY CONVECTION. LKLY  
POPS ARE IN THE FCST.  
 
THURSDAY...CHRISTMAS DAY - DEEP LAYER ZONAL FLOW WILL FILL IN  
ACROSS THE AREA. DRY CONDITIONS XPCTD AS THE COLD FRONT SHOULD BE  
E OF THE AREA. A DEEP STACKED LOW WILL BE OVER THE EASTERN GREAT  
LAKES. RIGHT NOW "COOL AND BRZY" COULD BE THE WX WORDS FOR THE DAY.  
 

 
   
AVIATION /03Z FRIDAY THROUGH TUESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
00Z TAFS WILL BE VFR.  
 
TONIGHT...A VFR CIG IS FORECAST. FOR KACY AND KMIV THIS IS MAINLY  
DUE TO MID LEVEL CLOUDS. AT THE KPHL AIRPORTS, ITS A COMBINATION  
OF A STRATOCU CIG AROUND 4K AND THE MID LEVEL CLOUD DECK. AT KRDG  
AND KABE ITS MAINLY A STRATOCU DECK AT AROUND 3500 FEET. THERE  
WILL BE MVFR CIGS AT AIRPORTS FARTHER TO THE NORTHWEST AND MIGHT  
MAKE IT INTO THESE LATTER TERMINALS. WE DID AMEND SOME OF THE  
TERMINALS DOWNWARD. WEST TO NORTHWEST WINDS SHOULD AVERAGE LESS  
THAN 10 KNOTS.  
 
FRIDAY...GOING MORE PESSIMISTICALLY WITH VFR CIGS AND EXPECTING A  
STRATOCU CIG TO EITHER PERSIST NORTHWEST TO TERMINALS, OR DEVELOP  
ELSEWHERE DURING THE DAY. MVFR CIGS POSSIBLE HIER TERRAIN  
AIRPORTS. NORTHWEST WINDS SHOULD BE SLIGHTLY LESS THAN TODAY WITH  
SUSTAINED SPEEDS AROUND 10 KNOTS AND PEAK GUSTS CLOSER TO 20  
KNOTS. LATE IN THE DAY WE ARE PREDICTING THE GUSTS AND VFR CIGS  
SHOULD NO LONGER OCCUR.  
 
OUTLOOK...  
FRIDAY NIGHT - SATURDAY...VFR. NORTHWEST WINDS VEER TOWARDS THE  
NORTH-NORTHEAST BY SATURDAY.  
 
SUNDAY - MONDAY...SUB-VFR POSSIBLE WITH SCATTERED RAIN/SNOW SHOWERS.  
 
TUESDAY...VFR.  
 

 
   
MARINE
 
 
THE SMALL CRAFT ADVISORY NORTHERN WATERS WILL BE ALLOWED TO  
EXPIRE AT 10 PM. GUIDANCE IS SHOWING A PAINFULLY SLOW, BUT STEADY  
DROP OFF IN WINDS.  
 
GUSTS NEAR OR ABOVE 20 KT WILL BE POSSIBLE THROUGH THE OVERNIGHT.  
 
SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED ON FRIDAY.  
 
 
OUTLOOK...  
FRIDAY NIGHT...MOSTLY SUB-ADVISORY CONDITIONS ARE EXPECTED. SOME  
NORTHWEST WIND GUSTS COULD STILL BE IN THE 20 PLUS KNOT RANGE,  
THOUGH. CONFIDENCE: ABOVE AVERAGE.  
 
SATURDAY - SUNDAY...SUB-SCA EXPECTED FOR THE MOST PART. SEAS REMAIN  
AROUND 3 TO 4 FEET. CONFIDENCE: AVERAGE TO SLIGHTLY BELOW AVERAGE.  
 
MONDAY - TUESDAY...SCA CONDITIONS SHOULD PRESENT THEMSELVES LATER  
ON MONDAY UNDER A STRENGTHENING EASTERLY FLOW AND BUILDING SEAS.  
CONFIDENCE: AVERAGE.  
 

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

 
 

 
SYNOPSIS...GIGI  
NEAR TERM...GIGI  
SHORT TERM...99  
LONG TERM...99  
AVIATION...GIGI/99  
MARINE...GIGI/99  
 
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