602  
FXUS61 KPHI 111125  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
625 AM EST SUN DEC 11 2016  
   
SYNOPSIS
 
 
LOW PRESSURE CROSSING THE GREAT LAKES REGION SUNDAY NIGHT LIFTS A  
WARM FRONT INTO OUR AREA. THIS WILL BE QUICKLY FOLLOWED BY A COLD  
FRONT PUSHING THROUGH THE REGION MONDAY AFTERNOON AS THE CENTER OF  
THE LOW MOVES TO MAINE. ANOTHER COLD FRONT IS EXPECTED WEDNESDAY OR  
WEDNESDAY NIGHT. STRONG HIGH PRESSURE BUILDS EAST THROUGH THE END OF  
THE WORK WEEK BRINGING OUR COLDEST AIR OF THE SEASON SO FAR THURSDAY  
AND FRIDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
A BAND OF FLURRIES HAS DEVELOPED FROM CENTRAL DELMARVA BACK  
TOWARDS SOUTH CENTRAL PA. THIS IS MODELED BY HIGH RESOLUTION  
MODELS SUCH AS THE HRRR. SINCE THIS BAND IS WELL DISPLACED FROM  
THE LIFT ASSOCIATED WITH THE SHORT WAVE TROUGH, AND THE SURFACE  
HIGH REMAINS IN PLACE, DO NOT EXPECT THIS BAND TO LAST LONG. IN  
FACT THE HRRR SHOWS IT DISSIPATING WITHIN THE NEXT FEW HOURS.  
UPDATED THE FORECAST TO INCLUDE A MENTION OF ISOLATED FLURRIES  
THROUGH MID MORNING.  
 
OTHERWISE, THE HIGH PRESSURE ACROSS THE AREA EARLY THIS MORNING  
WILL SHIFT OFFSHORE BY MIDDAY. CLOUDS WILL INCREASE THROUGH THE  
MORNING, ESPECIALLY ACROSS THE NORTHERN HALF OF THE AREA, AS LOW-  
MID LEVEL MOISTURE INCREASES. A SHORT WAVE/VORTICITY IMPULSE IS  
EXPECTED TO MOVE ACROSS THE AREA FROM LATE MORNING INTO THE  
AFTERNOON, WHICH SHOULD CREATE SOME ENHANCED LIFT ACROSS THE AREA.  
WITH THIS ENHANCED LIFT AND MOISTURE COMBINATION, AN AREA OF LIGHT  
SNOW COULD DEVELOP AND SPREAD ACROSS THE NORTHERN HALF OF THE  
AREA, BASICALLY FROM I-78 NORTHWARD. A LIGHT DUSTING TO AROUND AN  
INCH OF SNOW IS POSSIBLE THIS AFTERNOON, WITH THE HIGHEST AMOUNTS  
EXPECTED ACROSS THE NORTHERN AREAS, I-80 NORTHWARD.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/
 
 
A BREAK IN THE SNOW IS POSSIBLE EARLY THIS EVENING AS THE LEAD SHORT  
WAVE PASSES EASTWARD, BUT THIS BREAK IN PRECIPITATION WILL ONLY BE  
TEMPORARY. A WARM FRONT WILL LIFT NORTHWARD ACROSS THE AREA TONIGHT  
AS AN AREA OF LOW PRESSURE MOVES INTO THE GREAT LAKES REGION. A  
COUPLE OF SHORT WAVE/VORTICITY IMPULSES WILL SPREAD ACROSS THE AREA  
DURING THE OVERNIGHT, WHICH WILL HELP ENHANCE LIFT ACROSS THE AREA  
AS LOW-MID LEVEL MOISTURE SPREAD THROUGH THE REGION. THIS WILL LEAD  
TO AN EXTENDED PERIOD OF PRECIPITATION. THE QUESTION BECOMES WHAT THE  
P-TYPES WILL BE. AS THE PRECIPITATION FIRST DEVELOPS AND SPREADS  
ACROSS THE AREA, IT SHOULD START OUT AS SNOW. HOWEVER, AS  
TEMPERATURES BEGIN TO WARM, ESPECIALLY ALOFT, WE SHOULD BEGIN HAVING  
A CHANGE OVER TO A WINTRY MIX. WE EXTENDED THE WINTER WEATHER  
ADVISORY A TIER OF COUNTIES SOUTHWARD, AND HAVE KEPT THE ADVISORY  
THE SAME FOR THE COUNTIES THAT WERE ALREADY IN IT. HIGHEST SNOW  
AMOUNTS ARE EXPECTED TO BE ACROSS THE NORTHERN AREAS FROM I-78/I-80  
NORTHWARD WHERE 3-5 INCHES IS POSSIBLE. SOUTH OF THIS AREA IN THE  
ADVISORY, A DUSTING TO 1-2 INCHES IS POSSIBLE. WITH THE FREEZING  
RAIN, A TRACE TO LESS THAN ONE-TENTH OF AN INCH OF ICE IS EXPECTED  
BEFORE A CHANGE OVER TO ALL RAIN.  
 

 
   
LONG TERM /MONDAY THROUGH SATURDAY/
 
 
MONDAY...THOUGH THE WARM FRONT SHOULD BE MOST IF NOT ALL THE WAY  
THROUGH THE REGION BY SUNRISE, A WINTRY MIX MAY LINGER IN THE  
POCONOS AND NW NJ THROUGH MID MORNING WHERE THE TERRAIN MAY HELP  
TO KEEP THE COLD AIR ENTRENCHED IN THE BOUNDARY LAYER. STILL, BY  
15Z, EXPECT ALL PRECIP TO BE RAIN. PRECIP SHOULD END QUICKLY FROM  
WEST TO EAST FROM MID DAY THROUGH THE AFTERNOON AS THE COLD FRONT  
SWEEPS THROUGH THE REGION, ALSO BRINGING DRY AIR ADVECTION.  
 
MONDAY NIGHT THOUGH TUESDAY...SOME COLD AIR ADVECTION BEHIND THE  
COLD FRONT. A HIGH TRIES TO BUILD IN BRIEFLY, BRINGING MOSTLY  
TRANQUIL WEATHER FOR THIS PERIOD.  
 
WEDNESDAY...NEXT COLD FRONT ARRIVES. STILL CONSIDERABLE  
UNCERTAINTY ON HOW FAR NORTH WILL BE THE EXTEND OF PRECIP  
ASSOCIATED WITH AN OFF SHORE LOW. IF THERE IS ANY FOR OUR REGION,  
IT SHOULD BE MOSTLY SNOW, BUT DOES NOT LOOK TO BE A MAJOR SNOW  
PRODUCER AT THIS POINT.  
 
THURSDAY THROUGH FRIDAY...STILL LOOKING LIKE THIS PERIOD WILL BE  
THE COLDEST TEMPERATURES OF THE SEASON SO FAR, WITH MANY LOCATIONS  
STAYING BELOW FREEZING THROUGH THE 2 DAYS.  
 
SATURDAY AND SUNDAY...STILL WATCHING A CLOSED LOW THAT COULD BE  
LIFTING FROM THE PLAINS INTO THE GREAT LAKES REGION THROUGH THIS  
PERIOD, THOUGH THERE REMAINS QUITE A BIT OF UNCERTAINTY WITH THE  
EXACT TRACK.  
 

 
   
AVIATION /12Z SUNDAY THROUGH THURSDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
VFR CONDITIONS CONTINUE FOR THE FIRST HALF OF TODAY, ALTHOUGH CLOUD  
COVER WILL INCREASE. A PERIOD OF LIGHT SNOW COULD DEVELOP AND SPREAD  
ACROSS THE AREA THIS AFTERNOON, ESPECIALLY FOR ABE AND RDG. IF THE  
SNOW DOES DEVELOP, IT COULD LEAD TO MVFR CONDITIONS. THE REST OF THE  
TAF SITES HAVE A SMALLER CHANCE, SO WE ONLY HAVE A PROB30 IN FOR  
NOW. A BREAK IN THE SNOWFALL IS EXPECTED THIS EVENING WITH VFR  
CONDITIONS, BEFORE DIMINISHING CONDITIONS OVERNIGHT. MVFR, THEN IFR  
CONDITIONS ARE EXPECTED TO DEVELOP OVERNIGHT AS SNOW DEVELOPS AND  
SPREAD ACROSS THE AREA. A CHANGE OVER TO A WINTRY MIX OF SLEET AND  
FREEZING RAIN IS POSSIBLE FOR ABE, RDG, AND TTN OVERNIGHT, BEFORE  
CHANGING TO ALL RAIN BY MONDAY MORNING. FOR ILG, PHL, PNE SOUTHWARD,  
THE SNOW SHOULD CHANGE OVER TO PLAIN RAIN AS TEMPERATURES WARM  
OVERNIGHT AND NO FREEZING RAIN IS EXPECTED.  
 
LIGHT AND VARIABLE WINDS EARLY THIS MORNING WILL BECOME  
SOUTHWESTERLY LATER THIS MORNING AS HIGH PRESSURE MOVES OFFSHORE. AS  
A WARM FRONT LIFTS INTO THE AREA TONIGHT, WIND WILL BECOME MORE  
SOUTHEASTERLY.  
 
OUTLOOK...  
MONDAY...MVFR AND LOCALIZED IFR CONDITIONS (MOSTLY FOR CEILINGS)  
IN THE MORNING SHOULD IMPROVE TO VFR THROUGH THE AFTERNOON HOURS.  
ANY PRECIP AT THE TAF SITES SHOULD BE ALL RAIN AFTER 12Z MONDAY.  
 
MONDAY NIGHT...VFR. BREEZY NORTHWESTERLY WINDS POSSIBLE DURING THE  
EVENING HOURS.  
 
TUESDAY...VFR CONDITIONS EXPECTED.  
 
WEDNESDAY...MVFR OR EVEN IFR CONDITIONS ARE POSSIBLE IF WINTRY  
PRECIP MOVES INTO THE REGION. GUSTY NORTHWESTERLY WINDS BY NIGHT.  
 
THURSDAY...VFR CONDITIONS EXPECTED. WINDY CONDITIONS POSSIBLE  
THROUGH THE DAY WITH NORTHWEST WIND GUSTS UP TO 30 KT.  
 

 
   
MARINE
 
 
SUB-SMALL CRAFT ADVISORY CONDITIONS WILL PERSIST ACROSS THE WATERS  
TODAY AS HIGH PRESSURE BUILDS ACROSS THE AREA EARLY, THEN OFFSHORE  
DURING TODAY. WINDS ARE EXPECTED TO INCREASE TONIGHT AS A WARM FRONT  
LIFTS ACROSS THE WATERS AND REACH SMALL CRAFT ADVISORY LEVEL BY  
MIDNIGHT. CONDITIONS COULD APPROACH GALE FORCE, BUT WITH  
UNCERTAINTY, HAVE ONLY ISSUED A SMALL CRAFT ADVISORY FOR NOW AND  
LET LATER SHIFTS UPGRADE IF NEEDED.  
 
OUTLOOK...  
MONDAY...ON THE COASTAL WATERS, SCA CONDITIONS ARE EXPECTED  
THROUGH THE DAY AND FOR THE FIRST HALF OF MONDAY NIGHT. GIVEN WARM  
AIR ADVECTION OVER RELATIVELY COOL WATERS, TRANSFER IS EXPECTED TO  
BE POOR, SO EVEN THOUGH THERE COULD BE VERY STRONG WINDS JUST  
ABOVE THE SURFACE, GALE FORCE GUSTS, IF ANY, ARE EXPECTED TO BE  
LIMITED TO THE OUTER COASTAL WATERS. WILL CONTINUE TO MONITOR THIS  
POTENTIAL THOUGH. ON THE DELAWARE BAY, SCA CONDITIONS ARE EXPECTED  
TO BE CONFINED TO THE LOWER BAY, THOUGH ON THE UPPER BAY, GUSTS  
NEAR OR ABOVE 20 KT WILL BE POSSIBLE BEHIND THE COLD FRONT.  
 
TUESDAY...WINDS AND SEAS SHOULD DROP BELOW SCA CRITERIA BEFORE  
SUNRISE AND SUB SCA CONDITIONS SHOULD CONTINUE FOR THE REMAINDER  
OF THE DAY.  
 
WEDNESDAY...WINDS AND SEAS SHOULD STAY BELOW SCA CRITERIA.  
 
WEDENSDAY NIGHT AND THURSDAY...BEHIND A COLD FRONT, STRONG WEST  
NORTHWEST WINDS ARE EXPECTED. WINDS SHOULD GUST TO AT LEAST 30KT  
ON THE COASTAL WATERS, AND MAY GUST TO GALE FORCE AT TIMES.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 9 AM EST  
MONDAY FOR PAZ054-055-062.  
WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 6 AM EST  
MONDAY FOR PAZ060-061-105.  
WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 4 AM EST  
MONDAY FOR PAZ101-103-104-106.  
NJ...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 9 AM EST  
MONDAY FOR NJZ001-007-008.  
WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 6 AM EST  
MONDAY FOR NJZ009-010.  
WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 4 AM EST  
MONDAY FOR NJZ012-015.  
DE...NONE.  
MD...NONE.  
MARINE...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 AM EST  
TUESDAY FOR ANZ450>455.  
SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 1 PM EST  
MONDAY FOR ANZ431.  
 

 
 

 
SYNOPSIS...JOHNSON  
NEAR TERM...JOHNSON/ROBERTSON  
SHORT TERM...ROBERTSON  
LONG TERM...JOHNSON  
AVIATION...JOHNSON/ROBERTSON  
MARINE...JOHNSON/ROBERTSON  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab PA Page
The Nexlab NJ Page
The Nexlab DE Page
The Nexlab MD Page Main Text Page