928  
FXUS61 KPHI 290140  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
940 PM EDT THU MAY 28 2015  
   
SYNOPSIS
 
 
A COLD FRONT WILL MOVE ACROSS THE AREA OVERNIGHT. HIGH PRESSURE  
REESTABLISHES ITSELF OFF THE EAST COAST FRIDAY INTO SATURDAY.  
ANOTHER COLD FRONT WILL THEN SLOWLY MOVE ACROSS THE REGION  
SATURDAY NIGHT OR SUNDAY. HIGH PRESSURE WILL BUILD OVER EASTERN  
CANADA EARLY NEXT WEEK WHILE THE FRONTAL BOUNDARY STALLS TO OUR  
SOUTH.  
 

 
   
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
 
 
SHOWERS AND THUNDERSTORMS HAVE DISSIPATED WITHIN THE PAST TWO  
HOURS OVER MOST OF THE REGION. SOME NEW SHOWERS HAVE BROKEN OUT  
OVER NORTHEAST MARYLAND, BUT COVERAGE IS ISOLATED. ADDITIONAL  
SHOWERS HAVE DEVELOPED WEST OF THE CHESAPEAKE BAY. RECENT HRRR  
RUNS SUGGESTS THIS ACTIVITY MAY CONTINUE INTO THE EARLY MORNING  
HOURS.  
 
WIND SHIFT TO THE NORTH (SPEEDS VERY LIGHT) HIGHLIGHTS THE ARRIVAL  
OF DRIER AIR ACROSS THE REGION. DEWPOINT DISCONTINUITY PROVIDES  
BEST IDENTIFICATION OF FRONTAL BOUNDARY.  
 
THERE MAY BE SOME PATCHY FOG/ST OVERNIGHT IN THE FRONTAL BOUNDARY  
AREA WITH CONFIDENCE FOR FOG/STRATUS FORMATION BELOW AVG. PATCHY  
FOG IS IN THE WEATHER GRIDS USING THE UPS CROSSOVER TOOL.  
 
OTHERWISE A FAIR NIGHT AND A FEW DEGREES COOLER UP NORTH LATE AT  
NIGHT DUE TO DRIER AIR.  
 
FCST TEMPS ARE BASED ON THE WARMER 12Z/28 NAM MOS AND ALL OTHER  
GUIDANCE IS DERIVED OFF A 50 50 BLEND OF THE 12Z/28 GFS/NAM MOS.  
 

 
   
SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/
 
 
A NICER DAY WITH LOWER DEWPOINTS...AN IDEAL SUMMER DAY KPHL  
NORTHEASTWARD...WARM BUT RELATIVELY COMFORTABLE WITH LIGHT EAST  
WINDS TURNING SE OR S DURING THE AFTERNOON. COOLER COASTS DUE TO  
THE UPWELLED COOLER OCEAN WATERS, ESPECIALLY NNJ.  
 
WE HAVE SMALL POPS IN DURING THE MORNING DELMARVA AND SPREADING  
NWD THRU E PA IN THE AFTN BUT CONFIDENCE IS BELOW AVG. IT SHOULD  
BE RAINFREE MOST OF OUR FORECAST AREA ON FRIDAY. ONLY CALLED IT  
SHOWERS PER MORE STABLE ENVIRONMENT AND CHANCEY AT WORST IN SW  
PORTION OF THE FCST AREA  
 
FCST TEMPS BASED ON THE WARMER OF THE AVBL 12Z/28 NCEP GUIDANCE.  
REMAINDER OF THE ELEMENTS DERIVED FROM THE 12Z/28 50 50 BLENDED  
GFS/NAM MOS.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/
 
 
HIGH PRES WILL REMAIN OFF THE COAST FOR THE START OF THE PD AS  
CDFNT ADVANCES FROM THE W. WITH THE LOW OVER QUEBEC, WE WILL BE  
WELL IN THE WARM SECTOR AND WITH OUT MANY TRIGGERS BESIDES DAYTIME  
HEATING, EXPECT FRI NIGHT TO BE DRY AND EARLY SAT AS WELL. BY  
LATER SAT, CUD SEE A FEW SHRA/TSTMS MAINLY N AND W.  
 
BY LATER SAT INTO SUN, THIS IS OUR BEST SHOT TO SEE SOME DECENT  
RAIN ACRS THE AREA, AND WE NEED IT. THE ECMWF, IS STILL A BIT  
SLOWER WITH THE CFP, BUT OVERALL TIMING DIFFS HAVE DECREASED. SAT  
NIGHT INTO SUN APPEARS TO BE THE WET TIME PD, THOUGH IT WONT BE  
RAINING THE WHOLE TIME, AND CERTAINLY NOT EVERYONE WILL GET RAIN  
AT THE SAME TIMES.  
 
BEHIND THE FRONT, HIGH PRES WILL MOVE TO THE N AND BE ANCHORED IN  
QUEBEC AS THE FRONT STALLS TO OUR S. NELY FLOW WILL SET IN THE  
FCST WILL BE VERY DEPENDENT ON WHERE THE FRONT SETS UP. EXPECT MON  
TO BE COOL AND DREARY WHETHER OR NOT IT RAINS, BUT THERE WILL BE  
SCT SHOWERS AT LEAST, AND PSBLY MORE IN THE WAY OF PRECIP. GUID IS  
STILL HAVING DIFFICULTY WITH DETERMINING OF WHERE THE STEADIEST  
RAIN MIGHT BE AND HAS HAD PROBS OVER THE LAST FEW DAYS WITH THE  
DETAILS OF THE FCST AROUND MON. THOSE STILL CONTINUE. IT SHUD BE  
NOTED THAT THE CMC IS MUCH DRIER THAN EITHER THE GFS AND ECMWF ON  
MON. THE GFS HAS A WET BIAS, BUT THE ECMWF, EXCEPT FOR ONE DAY  
EARLIER THIS WEEK HAS BEEN CONSISTENT WITH SOME PRECIP FOR MON.  
 
HIGH PRESSURE SLIDES ACROSS TO THE NORTH AND EAST OF THE REGION  
MONDAY NIGHT. WITH HIGH PRESSURE REMAINING ENTRENCHED OVER THE  
ATLANTIC OCEAN, THE COLD FRONT MAKES LITTLE HEADWAY THROUGH THE  
REGION AND LOOKS LIKELY TO REMAINED STALLED ACROSS OR NEAR OUR AREA  
THROUGH TUESDAY. AS THE NORTHEASTERN HIGH STARTS TO PUSH BACK INTO  
OUR AREA, THE FRONT WILL PUSH OFFSHORE, AROUND WEDNESDAY. THE HIGH  
THEN REMAINS OVER OUR AREA THROUGH THE END OF THE WEEK.  
 
WITH THE FRONT REMAINING STALLED IN OUR AREA, A CHANCE FOR SOME  
SHOWERS WILL CONTINUE THROUGH TUESDAY. AS THE FRONT STARTS TO PUSH  
OFFSHORE SHOWER ACTIVITY WILL EXIT FROM NORTHWEST TO SOUTHEAST AND  
AS THE HIGH BUILDS INTO OUR REGION, WE SHOULD REALLY START TO DRY  
OUT, REMAINING DRY THROUGH THURSDAY.  
 
TEMPS START OUT QUITE WARM, THEN TAKE A NOSEDIVE MON AND TUE  
BEFORE RETURNING TO MORE NRML LEVELS BY THE END OF THE PD.  
 

 
   
AVIATION /02Z FRIDAY THROUGH TUESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
TONIGHT...CFP OCCURS WITH WIND SHIFTING TO LIGHT N AND THEN NE.  
IFR ST/FOG MAY FORM IN THE FRONTAL ZONE OVERNIGHT OTRW PREDICTING  
GENERALLY VFR. CONFIDENCE: BELOW AVERAGE DUE TO THE UNCERTAINTY  
REGARDING THE FORMATION OF IFR ST/FOG OVERNIGHT.  
 
FRIDAY...VFR WITH ANY LEFTOVER IFR DISSIPATING BY 14Z AND THEN  
SCT-BKN CLOUDS AOA 4000 FT DURING THE AFTN. LIGHT E WIND DURING  
THE MORNING BECOMING SE TO S DURING THE AFTERNOON. ISOLATED  
SHOWERS POSSIBLE FOR KILG AND KRDG DURING THE AFTN. THUNDER  
UNLIKELY IN OUR AREA.  
 
CONFIDENCE: AVERAGE.  
 
OUTLOOK...  
FRI NIGHT...VFR ERLY, THEN LOWERING CIGS/VSBYS WITH STRATUS/FOG  
PSBL. MDT CONFIDENCE  
 
SAT...LOWER CONDITIONS PSBL ERLY, THEN BECOMING VFR DURING THE  
DAY. SCT SHRA/TSRA MAINLY N AND W. MDT CONFIDENCE.  
 
SAT NIGHT-MON...AN EXTENDED PERIOD OF MVFR/IFR CONDITIONS  
POSSIBLE. A CHANCE OF RAIN EACH DAY. BEST POTENTIAL FOR  
TSRA IS SUN WITH CFP SAT NIGHT INTO SUN. LOW CONFIDENCE ON EXACT  
DETAILS.  
 
MONDAY NIGHT THROUGH TUESDAY...IMPROVING CONDITIONS FROM NORTHWEST  
TO SOUTHEAST. LINGERING SHOWERS WITH MVFR CEILINGS/VISIBILITIES  
MONDAY NIGHT IMPROVING TO VFR BY LATE MORNING/EARLY AFTERNOON ON  
TUESDAY.  
 

 
   
MARINE
 
 
DO NOT ANTICIPATE SCA CONDITIONS THROUGH FRIDAY. SLY FLOW SHOULD  
TURN NE TO E ALONG THE WATERS OVERNIGHT AND LIGHT ONSHORE FRIDAY.  
 
OUTLOOK...  
 
FRI NIGHT-SAT...SUB-SCA CONDS EXPECTED, ALTHOUGH WINDS MAY GUST  
AROUND 20 KNOTS AT TIMES AND SEAS COULD APPROACH 5 FT BY THE END  
OF THE PD.  
 
SAT NIGHT-MON...INCREASING SEAS ESPECIALLY LATER SUN INTO MON  
WITH WIND INCREASING ABOVE SCA CRITERIA AS WELL. AN SCA WILL  
LIKELY BE BE NEEDED FOR A PORTION OF THIS TIME WITH THE FRONT TO  
OUR S AND INCREASING NELY FLOW.  
 
MONDAY NIGHT THROUGH TUESDAY...EASTERLY FLOW WILL CONTINUE ACROSS  
THE WATERS THROUGH TUESDAY. SEAS WILL REMAIN ELEVATED ABOVE 5 FEET  
ON THE OCEAN WITH WINDS GUSTING UP AROUND 25 KNOTS.  
 

 
   
RIP CURRENTS
 
 
NEW WEBLINK, WORKS BEST ON FIREFOX. DISPLAYS THE FCST GRAPHIC ETC.  
 
WWW.WEATHER.GOV/PHI/SURFRIP4  
 
LOW RISK CONTINUES THROUGH FRIDAY.  
 
SUBSTANTIAL UPWELLING OCCURRED YESTERDAY WITH THE SOUTHERLY FLOW,  
ESPECIALLY NNJ WATERS WHERE 44065 WATER TEMP DROPPED ALMOST 9  
DEGREES IN 24 HRS DOWN INTO THE UPPER 40S EARLIER THIS MORNING.  
 
CHILLY TO SWIM MOST OF CENTRAL AND NNJ BEACHES DESPITE WELL ABOVE  
NORMAL LAND TEMPS.  
 

 
   
CLIMATE
 
 
MAY 2015...A TOP 5 WARMEST ON RECORD FOR LARGE PORTIONS OF OUR AREA.  
 
CONSERVATIVE VALUES LISTED BELOW FROM OUR 5 AM SFT AND COOLING THE  
NEAR MIDNIGHT SUNDAY NIGHT MAY 31 LOW TEMP DUE TO NLY FLOW CAA SUNDAY  
EVENING.  
 
ALLENTOWN WILL PROBABLY AVERAGE VERY CLOSE TO 65.9 OR 6 DEGREES  
ABOVE NORMAL. POR BACK TO 1922. AT LEAST 5TH WARMEST ON RECORD.  
1991 67.2  
2012 66.1  
1944 66.0  
2004 65.9  
 
PHILADELPHIA WILL PROBABLY AVERAGE CLOSE TO 69.7 DEGREES OR 5.8  
DEGREES ABOVE NORMAL. SECOND WARMEST ON RECORD.  
 
1991 70.8  
 
NUMBER 3 WOULD BE 69.2 IN 2004.  
 
ATLANTIC CITY MAY 2015 65.9 OR 4.8 ABOVE NORMAL AND PROBABLE #3  
POR BACK TO 1874  
 
2004 66.9  
1991 66.0  
2015  
 
WILMINGTON DE SOLID POR BACK TO 1916 LOCKED INTO #4 WARMEST  
1896 70.1  
1991 69.1  
2004 68.2  
2015  
 
NO AVAILABLE MONTHLY HISTORICAL DATA FOR KMPO KGED KTTN AND KRDG.  
 

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

 
 

 
SYNOPSIS...NIERENBERG  
NEAR TERM...DRAG/SZATKOWSKI  
SHORT TERM...DRAG  
LONG TERM...NIERENBERG  
AVIATION...DRAG/SZATKOWSKI/NIERENBERG/MEOLA  
MARINE...DRAG/SZATKOWSKI/NIERENBERG/MEOLA  
RIP CURRENTS...  
CLIMATE...  
 
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