971  
FXUS61 KPHI 241948  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
348 PM EDT SUN MAR 24 2019  
   
SYNOPSIS
 
 
A COLD FRONT WILL SETTLE ACROSS THE REGION TONIGHT INTO MONDAY.  
A WEAK AREA OF LOW PRESSURE IS THEN EXPECTED TO DEVELOP ALONG THE  
FRONT AND TRACK JUST SOUTH OF OUR REGION MONDAY NIGHT INTO  
TUESDAY. HIGH PRESSURE THEN BUILDS INTO THE REGION TUESDAY AND  
REMAINS IN PLACE THROUGH FRIDAY. THE NEXT COLD FRONT ARRIVES LATER  
NEXT WEEKEND.  
 

 
   
NEAR TERM /UNTIL 6 AM MONDAY/
 
 
CLOUDS WILL CONTINUE TO INCREASE DURING THE OVERNIGHT HOURS AS A  
COLD FRONT APPROACHES, THEN CROSSES THE FORECAST AREA, POSITIONING  
ITSELF SOUTH OF THE AREA MONDAY MORNING. MOISTURE WITH THIS SYSTEM  
IS LIMITED, SO ONLY SCATTERED LIGHT RAIN SHOWERS OR SPRINKLES ARE  
EXPECTED WITH THE FRONTAL PASSAGE ITSELF, MAINLY TOWARD MORNING,  
ALONG WITH A WIND SHIFT TO THE NORTH.  
 
WITH THE CLOUD COVER AND A WEAK SOUTHERLY FLOW FOR MUCH OF THE  
OVERNIGHT PERIOD, LOW TEMPERATURES WILL RANGE FROM THE LOW TO MID  
30S IN THE FAR NORTH TO THE MID 40S SOUTH, A GOOD TEN DEGREES WARMER  
THAN LAST NIGHT AND 5 TO 10 DEGREES ABOVE NORMAL FOR THIS TIME  
OF YEAR.  
 

 
   
SHORT TERM /6 AM MONDAY THROUGH 6 PM MONDAY/
 
 
LOW PRESSURE FROM THE OHIO AND TENNESSEE RIVER VALLEYS IS EXPECTED  
TO MOVE NORTH ALONG THE COLD FRONT POSITIONED JUST TO OUR SOUTH,  
BRINGING AN INCREASED CHANCE OF RAIN SHOWERS TO THE SOUTHERN TWO-  
THIRDS OF THE FORECAST AREA, MAINLY SOUTH OF THE I-95/I-195  
CORRIDOR, LATER MONDAY AFTERNOON AND MONDAY NIGHT. TEMPERATURES WILL  
BE WARM ENOUGH FOR PRECIPITATION TO FALL AS ALL RAIN. A WEAK  
NORTHEASTERLY FLOW MONDAY MORNING WILL BECOME STRONGER AS THE LOW  
APPROACHES THE VA/NC COAST LINE LATER IN THE DAY. EXPECT HIGHS IN  
THE LOW 40S NORTH AND MID TO UPPER 50S SOUTH.  
 

 
   
LONG TERM /MONDAY NIGHT THROUGH SUNDAY/
 
 
MONDAY NIGHT-TUESDAY... A MID-LVL WAVE WILL PASS SOUTH OF THE  
AREA OVERNIGHT MONDAY CONCURRENT WITH THE LONGWAVE TROUGH  
CENTERED EAST OF HUDSON BAY SAGGING SOUTHWARD OVER THE AREA.  
LIFT ASSOCIATED WITH THIS WAVE COMBINED WITH MODEST LOW-LVL  
CONVERGENCE WILL SPARK PRECIPITATION OVER THE SOUTHERN PART OF THE  
AREA MONDAY NIGHT. PROGGING THE NORTHWARD EXTENT OF THE  
PRECIPITATION IS TRICKY AS THE AIRMASS WILL BE RAPIDLY DRYING  
FROM N-S MONDAY NIGHT INTO TUESDAY MORNING DUE TO INCREASING NORTHERLY  
FLOW RESULTING FROM HIGH PRESSURE BUILDING OVER THE GREAT LAKES  
COINCIDENT WITH CYCLOGENESIS TO OUR SE OVER THE ATLANTIC.  
LOWER-RESOLUTION GUIDANCE TYPICALLY STRUGGLES WITH THESE LOW-  
LVL DRY AIR SETUPS AND THUS LEANED MORE TOWARDS THE NAM/3KM AND  
CMC REG FOR POPS THIS PACKAGE AND DIDN'T GO AS FAR NORTH WITH  
HIGHER POPS AS THE EC/GFS/FV3 WOULD SUGGEST. THIS ESSENTIALLY  
CONFINES LIKELY POPS TO DELMARVA SOUTH OF NEW CASTLE/CECIL  
COUNTIES, AND FAR SOUTHERN NJ NEAR CAPE MAY. CAN'T RULE OUT  
PRECIPITATION MAKING IT UP TO ABOUT PHILADELPHIA BUT THINK THE  
DRY AIR WILL FILTER IN TOO QUICKLY FOR THE NORTHERN HALF OF THE  
CWA TO GET ANYTHING MONDAY NIGHT. ALTHOUGH CURRENTLY EXPECT MOST  
OF THE PRECIPITATION WILL BE RAIN, CAN'T RULE OUT SOME SNOW  
MIXING IN AT THE TAIL END EARLY TUESDAY MORNING (ALTHOUGH THIS  
WOULDN'T ACCUMULATE). SNOW POTENTIAL WILL LARGELY DEPEND UPON  
HOW LONG PRECIPITATION LINGERS IN THE FACE OF THE DRY AIR  
ADVECTION (E.G. THE NAM SOLUTION WOULD BE THE MOST FAVORABLE FOR  
SNOW BUT THE NAM IS ALSO THE SLOWEST PIECE OF GUIDANCE).  
 
PRECIPITATION IN THE SOUTH SHOULD END BY OR BEFORE DAYBREAK  
TUESDAY AS BOTH THE MID-LVL WAVE AND THE ASSOCIATED SFC LOW MOVE  
OUT TO SEA. TUESDAY WILL BE QUIET WITH A DRY AIRMASS IN PLACE,  
ALTHOUGH IT WILL BE SOMEWHAT COOL (HIGHS ABOUT 10 DEGREES BELOW  
NORMAL), AS CONTINUED COLD ADVECTION PERSISTS AS THE SFC. HIGH  
MOVES JUST TO OUR NW.  
 
WEDNESDAY... QUIET AS HIGH PRESSURE MOVES OVERHEAD.  
TEMPERATURES WARM A FEW DEGREES BUT ARE STILL A BIT BELOW  
NORMAL.  
 
THURSDAY/FRIDAY... THE AFOREMENTIONED HIGH PRESSURE MOVES OUT  
TO SEA BY EARLY THURSDAY WITH FLOW TURNING MORE SOUTHERLY. THIS  
WILL RESULT IN A NOTABLE WARM UP ON THURSDAY (APART FROM THE  
IMMEDIATE COAST WHERE THE WARM UP WILL BE MORE MODERATED) WITH  
HIGHS GETTING BACK TO NEAR NORMAL (UPPER 50S, MAYBE EVEN LOW  
60S). MOISTURE BEGINS TO INCREASE OVER THE AREA LATE THURSDAY  
ALTHOUGH THIS WILL BE MOSTLY CONFINED TO THE MID-LVLS.  
 
THE WARM UP CONTINUES ON FRIDAY AS SOUTHERLY FLOW PREVAILS.  
HIGHS SHOULD REACH THE MID TO UPPER 60S IN MOST LOCATIONS APART  
FROM THE IMMEDIATE COAST. GIVEN ADDITIONAL MOISTURE ADVECTION  
COMBINED WITH INCREASED HEATING, CAN'T RULE OUT A SHOWER OR  
THUNDERSTORM ACROSS THE FAR NORTHWEST BUT CONFIDENCE IS LOW AT  
THIS POINT  
 
SATURDAY/SUNDAY... GUIDANCE BEGINS TO DIVERGE ON SOLUTIONS FOR  
NEXT WEEKEND, AS THE PATTERN LOCALLY WILL DEPEND UPON THE  
EVOLUTION OF SHORTWAVE ENERGY OVER THE WESTERN US AND THIS  
ENERGY'S INTERACTION WITH A SAGGING LONGWAVE TROUGH OVER  
NORTHERN CANADA. THE GENERAL TREND HAS BEEN TO FURTHER AMPLIFY  
THE SHORTWAVE & PHASE IT WITH PART OF THE NORTHERN TROUGH BEFORE  
MOVING IT THROUGH THE AREA. HOWEVER THE DEGREE OF AMPLIFICATION  
WILL LARGELY DICTATE THE SPEED OF THE FEATURE AND ANY  
ASSOCIATED FRONTS OR PRECIPITATION AND THIS IS NOT AGREED UPON  
AT THIS TIME. CONSEQUENTLY BROADBRUSHED POPS IN THIS PERIOD AS  
BOTH PREFRONTAL CONVECTION AND PRECIPITATION ASSOCIATED WITH A  
COLD FRONT WOULD BE POSSIBLE.  
 

 
   
AVIATION /19Z SUNDAY THROUGH FRIDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
TONIGHT...VFR. INCREASING CLOUDS. SOUTHWEST WINDS 10 TO 15 KNOTS  
EARLY, BECOMING VARIABLE 6 KNOTS OR LESS DURING THE LATE EVENING  
HOURS.  
 
MONDAY...VFR CEILINGS, BUT MVFR CONDITIONS POSSIBLE BY AFTERNOON,  
ESPECIALLY NEAR/SOUTH OF PHL TO MIV AS SHOWERS ASSOCIATED WITH A LOW  
PRESSURE SYSTEM MOVE IN FROM THE SOUTHWEST. NORTH TO NORTHEAST WINDS  
AROUND 10 KNOTS.OUTLOOK... MONDAY...VFR CEILINGS, HOWEVER A  
PERIOD OF MVFR POSSIBLE WITH LIGHT RAIN MAINLY NEAR AND SOUTH OF  
ILG TO MIV. ANY RAIN ENDS BY LATE MONDAY NIGHT. NORTH TO  
NORTHEAST WINDS 10 KNOTS OR LESS.  
 
OUTLOOK...  
 
MONDAY NIGHT TO TUESDAY MORNING...MVFR CONDITIONS POSSIBLE IN  
PRIMARILY RAIN AT PHL AND SOUTHWARD. CONDITIONS IMPROVING NW TO  
SE WITH ALL TERMINALS LIKELY VFR BY 12Z TUESDAY. NORTHEAST  
WINDS 10-15 KTS (HIGHEST AT ACY).  
 
TUESDAY-FRIDAY VFR CONDITIONS EXPECTED TO PREVAIL. NORTHERLY  
WINDS ON TUESDAY BECOME LIGHT AND VARIABLE BY WEDNESDAY,  
EVENTUALLY TURNING SOUTHERLY BY THURSDAY.  
 

 
   
MARINE
 
 
TONIGHT AND MONDAY...HIGH PRESSURE WILL CONTINUE TO INFLUENCE  
THE COASTAL WATERS OF NEW JERSEY AND DELAWARE THROUGH A GOOD  
PORTION OF THE OVERNIGHT HOURS. HOWEVER, A COLD FRONT WILL BEGIN  
MOVING ACROSS THE NORTHERN WATERS AFTER MIDNIGHT, REACHING THE  
COASTAL WATERS OF DELAWARE MONDAY MORNING. A SOUTHWEST WIND 10  
TO 15 KNOTS WILL DOMINATE PRIOR TO THIS FRONTAL PASSAGE, THEN  
VEER TO THE NORTH- NORTHEAST SOON AFTER. 2 TO 3 FOOT WAVES ARE  
EXPECTED.  
 
OUTLOOK...  
MONDAY NIGHT AND TUESDAY...SCA CONDITIONS EXPECTED TO DEVELOP OVER  
SOUTHERN AND CENTRAL ATLANTIC MARINE AREAS WITH NORTHERLY/NORTHEASTERLY  
WIND GUSTS UP TO 30 KNOTS AND SEAS INCREASING TO 5-6 FT.  
NORTHERN NJ COASTAL WATERS AND DELAWARE BAY WILL BE MORE  
MARGINAL HOWEVER THERE WILL BE A WINDOW FOR SCA CONDITIONS  
TUESDAY MORNING. NORTHEASTERLY WINDS INCREASE LATER MONDAY  
NIGHT AND TUESDAY MORNING WITH GUSTS UP TO 30 KNOTS (ESPECIALLY  
ON THE ATLANTIC COASTAL WATERS TO PERHAPS LOWER DELAWARE BAY),  
THEN WINDS SHOULD DIMINISH SOME FROM NORTH TO SOUTH LATER  
TUESDAY. SEAS WILL ALSO BUILD DUE TO THE INCREASED NORTHEAST  
FLOW.  
 
WEDNESDAY THROUGH FRIDAY... SCA SEAS MAY LINGER IN SOUTHERN  
OCEAN ZONES WEDNESDAY MORNING HOWEVER AFTER THAT POINT SUB-SCA  
CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE PERIOD.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...NONE.  
NJ...NONE.  
DE...NONE.  
MD...NONE.  
MARINE...SMALL CRAFT ADVISORY FROM 2 AM TO 11 PM EDT TUESDAY FOR ANZ451-  
452.  
SMALL CRAFT ADVISORY FROM 11 PM MONDAY TO 8 AM EDT WEDNESDAY  
FOR ANZ453>455.  
 

 
 

 
SYNOPSIS...MIKETTA  
NEAR TERM...MIKETTA  
SHORT TERM...MIKETTA  
LONG TERM...CARR  
AVIATION...CARR/MIKETTA  
MARINE...CARR/MIKETTA  
 
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