249  
FXUS61 KPHI 062311  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
711 PM EDT MON APR 6 2020  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL CONTINUE TO WORK ITS WAY ACROSS THE REGION  
THROUGH TUESDAY, BRINGING DRY AND PLEASANT WEATHER AS IT DOES SO. A  
WAVE OF LOW PRESSURE WILL RIDE ALONG A WARM FRONT AS IT SLOWLY LIFTS  
NORTHWARD INTO OUR REGION WEDNESDAY. A STRONGER SURFACE LOW WILL  
TRACK INTO THE GREAT LAKES BY THE END OF THE WEEK, BRINING A COLD  
FRONT EASTWARD ACROSS THE MID-ATLANTIC THURSDAY. UNSETTLED WEATHER  
LOOKS TO ACCOMPANY THE LOW AS IT SLOWLY LIFTS NORTH AND EAST FRIDAY,  
BEFORE HIGH PRESSURE BEGINS TO BUILD TO OUR SOUTH INTO THE WEEKEND.  
ANOTHER LOW PRESSURE SYSTEM MAY AFFECT OUR REGION INTO THE START OF  
NEXT WEEK.  
 

 
   
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
 
 
NO SIGNIFICANT CHANGES IN THE NEAR TERM. THE SEA BREEZE  
CONTINUES TO PROGRESS INLAND, BUT IS EXPECTED TO DISSIPATE  
WITHIN THE NEXT 3 HOURS.  
 
OTHERWISE, TRANQUIL WEATHER WILL PERSIST OVER THE REGION  
OVERNIGHT. CLOUDS WILL BEGIN TO INCREASE FROM SOUTH TO NORTH AS  
THE FRONT TO OUR SOUTH BEGINS TO MOVE BACK NORTHWARD AS A WARM  
FRONT AHEAD OF THE NEXT SYSTEM. LOWS WILL BE GENERALLY IN THE  
LOW TO MID 40S EXCEPT SOME UPPER 30S OVER THE SOUTHERN POCONOS  
AND PARTS OF NW NJ.  
 

 
   
SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/
 
 
THE CLOUDS WILL GENERALLY LOWER AND THICKEN THROUGH TUESDAY MORNING  
AS THE NEXT LOW PRESSURE SYSTEM ADVANCES THROUGH THE MIDWEST AND THE  
WARM FRONT TO OUR SOUTH CONTINUES TO NUDGE NORTHWARD. ALONG AND  
AHEAD OF THIS FRONT, IT'S STILL LOOKING LIKE THERE WILL BE SOME  
SHOWERS DEVELOPING BUT THE TIMING HAS BEEN DELAYED SLIGHTLY AND IT  
ALSO LOOKS AT THIS POINT LIKE MOST OF THE ACTIVITY SHOULD BE  
CONFINED TO SE PA INTO FAR SOUTHERN NJ AND DELMARVA. EXPECT THESE  
AREAS TO SEE INCREASING CHANCES FOR SOME SHOWERS AROUND MAINLY  
BEYOND THE MIDDAY TIME FRAME. POPS DECREASE TO SLIGHT CHANCE FARTHER  
NORTH OVER NE PA INTO NW NJ. ALSO WORTH MENTIONING, THERE COULD EVEN  
BE A FEW RUMBLES OF THUNDER LATE DAY BUT MAINLY SOUTH OF THE MASON-  
DIXON LINE. HIGHS TUESDAY WILL BE MAINLY IN THE LOW TO MID 60S SO  
NOT TOO DIFFERENT THAN TODAY AS THE WARM ADVECTION PATTERN IS  
COUNTERACTED BY THE INCREASED CLOUD COVER.  
 

 
   
LONG TERM /TUESDAY NIGHT THROUGH MONDAY/
 
 
A WEAK WAVE OF LOW PRESSURE WILL RIDE EASTWARD AS A WARM FRONT LIFTS  
NORTHWARD FROM VIRGINIA WEDNESDAY, BRINING SCATTERED RAIN SHOWERS TO  
THE REGION AS IT DOES SO. FORCING DOESN'T LOOK PARTICULARLY STRONG  
WITH ONLY A 100 KT UPPER LEVEL JET, THUS PVA WILL BE THE PRIMARY  
FORCING MECHANISM. RAIN SHOULD TAPER OFF BY LATE AFTERNOON OR EARLY  
EVENING AS THE DISTURBANCE PUSHES OFFSHORE TO OUR SOUTH AND  
EAST. FORECAST MLCAPE VALUES OF 500-1000 J/KG WILL LIKELY RESULT  
IN EMBEDDED THUNDERSTORMS. AS WE MOVE INTO RANGE OF SOME OF THE  
CAMS, THEY SUGGEST THERE COULD BE A COUPLE ROUNDS OF SHOWERS  
AND CONVECTION, WITH A MORE WIDESPREAD ROUND WEDNESDAY, FOLLOWED  
BY A LULL AND EVENTUALLY AN ADDITIONAL ROUND OF SHOWERS AND  
THUNDERSTORMS WEDNESDAY EVENING. WITH NO SURPRISE, KEPT MENTION  
OF THUNDER IN THE GRIDS THROUGH MUCH OF THE DAY WEDNESDAY.  
 
THE WARM FRONT LOOKS TO HANG SOMEWHERE OVER THE REGION, THUS A  
TEMPERATURE GRADIENT WILL LIKELY ESTABLISH ITSELF, YIELDING A LITTLE  
DIFFICULTY IN THE TEMPERATURE AND DEW POINT FORECAST IN SPATIAL AND  
TEMPORAL REGARD. HIGHS WEDNESDAY WILL VERY WELL LIKELY BE THE  
WARMEST OF THE WEEK WITH MOST PLACES REACHING NEAR OR ABOVE 70, SO  
THAT WILL ATTEMPT TO MAKE UP FOR THE PRECIPITATION.  
 
MOVING INTO THURSDAY, A SURFACE LOW WILL BEGIN TO APPROACH THE  
REGION AS IT MOVES ACROSS THE GREAT LAKES INTO SOUTHEASTERN ONTARIO.  
THE LOW LOOKS TO QUICKLY OCCLUDE AS BOTH THE EC AND GFS ARE  
FORECASTING A CLOSED 500 MB LOW BY THURSDAY AFTERNOON, THUS, AS IS  
USUALLY THE CASE WITH SUCH SYSTEMS, A NEW SURFACE LOW WILL FORM NEAR  
THE TRIPLE POINT SOMEWHERE OVER THE DELAWARE VALLEY. NOT A TON  
OF CONVECTION ALONG THE COLD FRONT AS IT MOVES INTO THE REGION  
AS FORECAST, CAPE VALUES INDICATE LESS IMPRESSIVE INSTABILITY  
COMPARED TO WEDNESDAY. NOT TO SAY THIS WON'T CHANGE AS WE DRAW  
CLOSER, BUT FORE NOW IT IS SUCH. THE NEW LOW WILL THEN SKIRT  
NORTHEAST ALONG THE NEW ENGLAND COAST INTO THURSDAY NIGHT INTO  
FRIDAY AS A REINFORCING SHORTWAVE DIVES SOUTHWARD ACROSS THE  
GREAT LAKES, PUMPING VORTICITY AND REINFORCING JET ENERGY INTO  
THE AMPLIFYING SYNOPTIC TROUGH. HIGHS THURSDAY WILL TREND  
SLIGHTLY COOLER WITH THE THREAT FOR MORE WIDESPREAD RAIN ALONG  
THE COLD FRONT WITH HIGHS STAYING IN THE LOW 60S NORTH TO UPPER  
60S SOUTH.  
 
UNSETTLED CONDITIONS FRIDAY AND INTO FRIDAY NIGHT AS THIS  
REINFORCING SHORTWAVE PUSHES A SERIES OF SURFACE TROUGHS SOUTH INTO  
THE REGION AROUND THE DEEPENING SURFACE LOW TO OUR NORTHEAST. BROAD-  
BRUSHED POPS THROUGH SATURDAY MORNING WITH THE GENERAL CHANCE FOR  
SCATTERED SHOWERS FOR NOW UNTIL BETTER GUIDANCE COMES INTO PLAY. THE  
SHARP COOLING AND STEEP LAPSE RATES SHOULD MEAN THAT ACROSS THE AREA  
THURSDAY AND FRIDAY WE'LL BE FAIRLY GUSTY FROM 25-35 KTS POSSIBLE.  
WE COULD APPROACH ADVISORY LEVEL WIND GUSTS THURSDAY AFTERNOON,  
SO THIS WILL WARRANT CONTINUAL OBSERVATION.  
 
HIGH PRESSURE BUILDS TO OUR SOUTH INTO THE CAROLINAS SATURDAY  
AFTERNOON THROUGH SUNDAY AS NORTHWEST FLOW SLOWLY TURNS MORE  
SOUTHWESTERLY. COOLER THAN WHAT WE WILL HAVE GROWN ACCUSTOMED TO  
THIS WEEKEND WITH HIGHS IN THE MID TO UPPER 50S SATURDAY AND LOW 60S  
BY SUNDAY.  
 
LONG RANGE GUIDANCE GOES SOUTH BY EARLY NEXT WEEK, WITH APPRECIABLE  
DIFFERENCES BETWEEN THE EC AND GFS MONDAY AS TO THE TIMING OF  
ANOTHER SURFACE LOW. THE EC HAS A SOLID SOAKER WITH A SURFACE LOW  
MOVING RIGHT UP THE EASTERN APPALACHIANS SUNDAY NIGHT INTO MONDAY  
MORNING MORNING, WHEREAS THE GFS KEEPS THE LOW WELL TO OUR WEST  
UNTIL LATE MONDAY AS A SURFACE LOW TRACKS ACROSS THE CAROLINAS. AS  
SUCH, POOR CONFIDENCE IN POPS AT THIS TIME WITH ONLY A BROAD GENERAL  
MENTION OF SHOWERS.  
 

 
   
AVIATION /23Z MONDAY THROUGH SATURDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
THROUGH TONIGHT...VFR CONDITIONS ARE EXPECTED, ALTHOUGH MID AND  
HIGH LEVEL CLOUDS ARE EXPECTED TO INCREASE AFTER 06Z. NORTHERLY  
AND NORTHWESTERLY WINDS ARE EXPECTED TO DIMINISH SOON AND MAY  
BECOME LIGHT AND VARIABLE OVERNIGHT. HIGH CONFIDENCE.  
 
TUESDAY...CLOUDS LOWERING AND THICKENING WITH LOW VFR TO HIGH END  
MVFR CIGS LIKELY BY THE AFTERNOON ALONG WITH A DEVELOPING CHANCE OF  
SHOWERS. MEDIUM CONFIDENCE.  
 
OUTLOOK...  
 
WEDNESDAY...SUB-VFR CONDITIONS LIKELY, ESPECIALLY IN THE EARLY  
MORNING AND LATE AFTERNOON WITH SEVERAL ROUNDS OF SHOWERS AND  
THUNDERSTORMS. SOUTHWESTERLY WINDS TURNING NORTHWESTERLY FROM 5 TO  
10 KNOTS WITH GUSTS TO 15 KNOTS. HIGHER GUSTS POSSIBLE IN  
THUNDERSTORMS. LOW CONFIDENCE.  
 
THURSDAY...VFR INITIALLY WITH DETERIORATION TO MVFR INTO THE LATE  
MORNING AND AFTERNOON AS RAIN MOVES INTO THE REGION AHEAD OF A COLD  
FRONT. SOUTHEASTERLY WIND TURNING SOUTHWESTERLY THEN WESTERLY INTO  
THE AFTERNOON. WINDS INCREASING TO 15 TO 20 KNOTS WITH GUSTS FROM 25  
TO 30 KNOTS POSSIBLE BY THE LATE AFTERNOON. MEDIUM CONFIDENCE.  
 
FRIDAY...GENERALLY VFR WITH WESTERLY WINDS FROM 15 TO 20 KNOTS  
WITH GUSTS FROM 25 TO 30 KNOTS. A FEW MVFR RESTRICTIONS POSSIBLE  
WITH WIDELY SCATTERED SHOWERS. MEDIUM CONFIDENCE.  
 
SATURDAY...VFR WITH WESTERLY WINDS FROM 5 TO 10 KNOTS AND GUSTS FROM  
15 TO 20 KNOTS. MEDIUM CONFIDENCE.  
 

 
   
MARINE
 
 
CONDITIONS ARE EXPECTED TO REMAIN BELOW SCA LEVELS THROUGH TUESDAY.  
WINDS BECOMING SW AROUND 5-10 KNOTS TONIGHT AND INCREASING TO 10-15  
KNOTS TUESDAY. SEAS MAINLY 3 TO 4 FEET THROUGH THE PERIOD.  
 
OUTLOOK...  
 
WEDNESDAY...SUB-SCA CONDITIONS EXPECTED WITH NORTHWESTERLY WINDS  
FROM 10 TO 15 KNOTS WITH GUSTS TO 20 KNOTS. SEAS FROM 1 TO 3  
FEET.  
 
THURSDAY...SCA CONDITIONS POSSIBLE WITH SOUTHEASTERLY WINDS TURNING  
SOUTHWESTERLY FROM 15 TO 20 KNOTS AND GUSTS UP TO 25 KNOTS. SEAS  
RANGING FROM 2 TO 4 FEET.  
 
FRIDAY...SCA CONDITIONS LIKELY WITH WESTERLY WINDS FROM 20 TO 25  
KNOTS WITH THE POSSIBILITY FOR GALE FORCE GUSTS ON THE ATLANTIC.  
SEAS FROM 2 TO 4 FEET.  
 
SATURDAY...SCA CONDITIONS MAY LINGER INTO EARLY SATURDAY MORNING,  
OTHERWISE, WINDS REMAIN BELOW ADVISORY CRITERIA THROUGH THE DAYTIME  
HOURS FROM 15 TO 20 KNOTS. SEAS LOWERING TO 1 TO 3 FEET.  
 

 
   
TIDES/COASTAL FLOODING
 
 
AS WE APPROACH THE FULL MOON TOMORROW, ASTRONOMICAL HIGH TIDES WILL  
BE RUNNING HIGH FOR THE NEXT FEW DAYS. WE DON'T HAVE MUCH ON SHORE  
FLOW THROUGH THE NEXT FEW DAYS, BUT GIVEN THE CURRENT ASTRONOMICAL  
HIGH TIDES, EVEN WEAK ONSHORE FLOW COULD PRODUCE MINOR COASTAL  
FLOODING. AT THIS POINT, WE ARE EXPECTING SPOTTY MINOR FLOODING FOR  
MOST HIGH TIDE CYCLES UNTIL WE GET TO WEDNESDAY EVENING. FOR THE  
WEDNESDAY EVENING/NIGHT HIGH TIDE, WE ARE CURRENTLY FORECASTING  
WIDESPREAD MINOR FLOODING FOR THE ATLANTIC OCEANFRONT AND THE  
DELAWARE BAY. HOWEVER, THIS WILL BE HIGHLY DEPENDENT ON THE TIMING  
OF A COLD FRONT ON WEDNESDAY. CURRENTLY WE ARE FORECASTING THE FRONT  
TO CROSS OFF SHORE LATE IN THE DAY, THUS WINDS WON'T SHIFT TO  
OFFSHORE UNTIL JUST BEFORE THE HIGH TIDE, HAVING LITTLE TO NO IMPACT  
TO DECREASE WATER LEVELS. HOWEVER, IF THE FRONT ARRIVES EARLIER IN  
THE DAY, THE INCREASED PERIOD OF OFFSHORE FLOW AHEAD OF THE HIGH  
TIDE COULD LEAD TO LOWER WATER LEVELS AT HIGH TIDE. WE WILL CONTINUE  
TO MONITOR THIS OVER THE NEXT FEW DAYS.  
 
ON THE TIDAL PORTIONS OF THE DELAWARE RIVER, THERE COULD BE SPOTTY  
MINOR TIDAL FLOODING FOR THE NEXT FEW HIGH TIDE CYCLES, BUT THE  
CHANCE FOR WIDESPREAD MINOR FLOODING IS LOW.  
 
AT THIS POINT, TIDAL FLOODING IS NOT EXPECTED ALONG THE NORTHEASTERN  
CHESAPEAKE BAY.  
 

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

 
 

 
SYNOPSIS...DAVIS  
NEAR TERM...FITZSIMMONS/JOHNSON  
SHORT TERM...FITZSIMMONS  
LONG TERM...DAVIS  
AVIATION...DAVIS/FITZSIMMONS/JOHNSON  
MARINE...DAVIS/FITZSIMMONS  
TIDES/COASTAL FLOODING...JOHNSON  
 
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