762  
FXUS61 KPHI 250802  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
402 AM EDT FRI JUL 25 2014  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL BUILD ACROSS THE OHIO VALLEY AND MID-ATLANTIC  
TODAY AND MOVE OFFSHORE TONIGHT. ON THE BACKSIDE OF THE HIGH PRESSURE  
SYSTEM A WARM FRONT AND ASSOCIATED LOW PRESSURE SYSTEM WILL MOVE ACROSS  
THE MIDWEST ON SATURDAY AND INTO OUR REGION BY SATURDAY NIGHT AND  
PUSH NORTH OF THE REGION ON SUNDAY. A COLD FRONTAL BOUNDARY THEN  
WILL SWEEP FROM WEST TO EAST ACROSS THE REGION ON MONDAY. A HIGH  
PRESSURE SYSTEM WILL BUILD IN BEHIND THE COLD FRONT FOR THE MIDDLE  
HALF OF NEXT WEEK.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
HIGH PRES WILL BUILD INTO THE REGION TODAY AND A DRY AND PLEASANT  
DAY IS IN STORE, WITH DEW POINTS IN THE 40S AND 50S, WHICH IS  
SPECTACULAR FOR LATE JULY! TEMPS ARE GENLY EXPECTED IN THE MID 80S.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/
 
 
THE HIGH WILL MOVE TO THE EAST TONIGHT AND THE WIND WILL BECOME MORE  
S TO SWLY BUT STILL BE LIGHT AND DEW POINTS WILL CREEP UP A BIT, BUT  
AGAIN DRY WX IS EXPECTED.  
 

 
   
LONG TERM /SATURDAY THROUGH THURSDAY/
 
 
SATURDAY AND SATURDAY NIGHT: A WARM FRONT APPROACHES THE REGION  
FROM THE MIDWEST AND OHIO VALLEY THEN PUSHES NORTHEAST THROUGH THE  
REGION SATURDAY NIGHT. THE RESULT WILL BE INCREASE IN SOUTHERLY  
MOISTURE AND MOISTURE TRANSPORT INTO THE REGION. MID-LEVEL AND  
SURFACE TEMPERATURES LOOK TO RESPOND IN KIND WITH THE SOUTHERLY  
AND SOUTHWEST ADVECTION, 925 MB TEMPS NEAR 20C SHOULD YIELD  
SURFACE TEMPERATURES JUST UNDER 90 FOR PHL AND IN THE 80'S  
ELSEWHERE ACROSS THE REGION. AS MENTIONED IN THE PREVIOUS FORECAST  
THE RAPID RISE OF DEWPOINTS APPEARS SUSPECT AND IS MUCH SLOWER  
WITH THE LATEST 00Z MAV AND MET GUIDANCE SETS. THE SLOWER DEWPOINT  
RISE MAY LIMIT THE AMOUNT OF DESTABILIZATION THAT OCCURS DURING  
THE DAY AS WELL. A FEW HUNDRED J/KG OF CIN COUPLED WITH 700 MB TEMPS  
NEAR 10C COULD ALLOW FOR THE FORMATION OF A WEAK CAP ACROSS THE  
SOUTHERN PART OF THE REGION. THE MAJORITY OF THE OPERATIONAL  
MODELS SUGGEST THE BEST CHANCE OF ANY SHORTWAVE/TRIGGER FOR  
CONVECTION TO BE ACROSS THE NORTHERN HALF OF THE REGION SATURDAY  
NIGHT, CLOSER TO THE WARM FRONT. WILL MAINTAIN CHANCE POPS ACROSS  
THE NORTH AND SLIGHT ACROSS THE SOUTH. ALSO OF INTEREST IS THE  
POTENTIAL FOR 30-50 KTS OF 0-6 KM BULK SHEAR AS WELL. IF STORMS  
CAN FORM SATURDAY NIGHT THERE IS A POTENTIAL FOR ORGANIZATION AND  
A DAMAGING WIND THREAT IF INSTABILITY OF THE MODELED 1000 J/KG OR  
SO DOES MATERIALIZE. PW VALUES JUST UNDER 2 INCHES SUGGEST A HEAVY  
RAIN THREAT WITH ANY STORMS AS WELL. THE CURRENT SPC OUTLOOK DOES  
NOT FEATURE A SEVERE THREAT IN THIS PERIOD LIKELY DUE TO THE  
LIMITED COVERAGE OF THE STORMS. AS THE MAIN STORM CHANCE IS LATE SATURDAY  
MODELED MOMENTUM TRANSFER SUGGESTS SOME GUSTS FROM 15-20 MPH ARE  
POSSIBLE IN THE AFTERNOON ON SATURDAY.  
 
SUNDAY AND SUNDAY NIGHT: CONTINUED WEST-SOUTHWEST FLOW IN THE WARM  
SECTOR. GOOD AGREEMENT AMONG THE GFS ENSEMBLES, 12Z ECMWF ENSEMBLE  
MEAN AND THE OPERATIONAL GFS AND CMC RUNS THAT THE HIGHEST CHANCE  
OF STORMS WILL BE SUNDAY NIGHT IN ASSOCIATION WITH THE STRONGEST VORT  
MAX AND ASSOCIATED SHORTWAVE. ON THE OTHER HAND THE NEW 00Z ECMWF  
RUN IS SLOWER AND HAS THE MAIN SHOW ON MONDAY. WENT HIGH CHANCE  
POPS SUNDAY AFTERNOON AND LOW END LIKELY POPS FOR SUNDAY NIGHT  
MORE ALONG THE LINE OF THE CMC AND GFS. FOR QPF STAYED CLOSE TO  
THE 21Z SREF. SIMILAR TO SATURDAY ENOUGH BULK SHEAR MAY BE PRESENT  
TO ORGANIZE STORMS THAT DO FORM. HOWEVER THE AMOUNT OF  
DESTABILIZATION IS IN QUESTION WITH MODELED CAPE VALUES ONLY  
AROUND 1000 J/KG AND WILL BE DEPENDENT ON CONVECTION FROM THE  
NIGHT BEFORE, PW VALUES NEAR 2 INCHES SUGGEST A CONTINUED HEAVY  
RAIN THREAT FROM STORMS. TEMPERATURES MAY BE RAIN COOLED SUNDAY  
BUT DID NOT GO IN THAT DIRECTION ATTM. FAIR SHOT AT 90 FOR PHL  
WITH SLIGHTLY WARMER MODELED MID-LEVEL TEMPERATURES THAN SATURDAY.  
THE SPC FEATURES THE REGION IN A SLIGHT RISK FOR SEVERE  
THUNDERSTORMS DUE TO THE POTENTIAL FOR THE STORMS TO ORGANIZE AND  
FOR WIND/HAIL THREATS. THE HWO HAS BEEN UPDATED FOR THIS.  
 
MONDAY AND MONDAY NIGHT: THE COLD FRONT MOVES THROUGH LIKELY MONDAY  
AFTERNOON. HOWEVER THIS SHOULD BE TO LITTLE TO LATE IN TERMS OF  
ANOTHER ROUND OF SHOWERS AND STORMS ON THE GFS AND CMC. THE NEW 00Z  
ECMWF IS SLOWER WITH THE FRONT LEADING TO ANOTHER ROUND OF SHOWERS  
AND THUNDER. FOR NOW CONTINUED WITH A MORE PROGRESSIVE IDEA  
CENTERING THE CHANCES IN EARLIER PERIODS BUT DID RAISE POPS IN THIS  
PERIOD. ANOTHER GUSTY DAY AS ONCE MODELED MOMENTUM TRANSFER SHOWS  
POTENTIAL FOR SOME GUSTS OF 15-20 MPH. RAIN MAY KEEP TEMPERATURES  
DOWN BUT MID-LEVEL TEMPERATURES SUGGEST ANOTHER HOT DAY.  
TEMPERATURES MAY TRY AND SPIKE AHEAD OF THE COLD FRONT AS WELL. MORE  
UNCERTAINTY WITH TEMPERATURES IN THIS PERIOD AS RAIN MAY KEEP  
TEMPERATURES DOWN BUT A TEMPERATURE SPIKE COULD OCCUR AHEAD OF THE  
FRONT.  
 
TUESDAY THROUGH THURSDAY: ANOTHER CANADIAN AIRMASS COMES DOWN INTO THE REGION  
AS THE SAME GENERAL PATTERN FROM THE WINTERTIME CONTINUES WITH FEW  
BREAKS. COOL NORTHWESTERLY FLOW WILL BE IN PLACE AS MOST LOCATIONS  
STRUGGLE TO 80 FOR HIGHS ON TUESDAY AND WEDNESDAY. EVEN WITH THIS  
ABNORMALLY COOL AIRMASS THERE IS GOOD AGREEMENT AMONG THE MEX, WPC  
AND MODELED TWO METER TEMPERATURES IN THIS PERIOD. WENT ON THE  
COOLER END OF GUIDANCE CLOSE TO WPC IN MOST PERIODS. LAPSE RATES MAY  
STEEPEN UP TUESDAY AFTERNOON FOR THE FORMATION OF SOME CUMULUS ON  
THE BACKSIDE OF THE TROUGH ACROSS THE NORTH WITH THE AID OF  
ELEVATION. OTHERWISE EACH DAY LOOKS MOSTLY SUNNY. DEWPOINT  
DEPRESSIONS LOOK TO LARGE FOR WEDNESDAY AND THURSDAY FOR MUCH IN THE  
WAY OF AFTERNOON CUMULUS.  
 

 
   
AVIATION /08Z FRIDAY THROUGH TUESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,  
KMIV, KACY AND SURROUNDING AREAS.  
 
VFR CONDS EXPECTED THRU THE TAF PD, WITH HIGH PRES IN CONTROL. THE  
HIGH WILL GRADUALLY MOVE EWD THRU TONIGHT AND THE WIND WILL SHIFT  
FROM N OR NW ERLY TO W TO SW BY TONIGHT. WIND SPEED SHUD GENLY BE  
LESS THAN 10 KT. WITH THE LIGHT WIND, THE GUID IS HINTING AT A BIT  
OF A SEABREEZE, MAINLY FOR KACY AND PSBLY FOR KMIV DURG THE LATE  
AFTN.  
 
OUTLOOK...  
SATURDAY AND SATURDAY NIGHT: BRIEF MVFR AND IFR RESTRICTIONS IN SCATTERED  
THUNDERSTORMS. HIGHEST CHANCE FOR RESTRICTIONS IS ON SATURDAY  
AFTERNOON AND EVENING FOR RDG, ABE, TTN, AND POINTS NORTH.  
 
SUNDAY THROUGH MONDAY NIGHT: BRIEF MVFR AND IFR RESTRICTIONS IN  
THUNDERSTORMS. SOME SOUTHWEST WIND GUSTS AROUND 15 KNOTS POSSIBLE  
MONDAY AFTERNOON OUTSIDE OF THUNDERSTORMS.  
 
TUESDAY: VFR.  
 

 
   
MARINE
 
 
WITH HIGH PRES OVER THE REGION TODAY AND MOVG OVER THE CSTL WATERS  
TONIGHT, NO MARINE HEADLINES ARE ANTICIPATED THRU THE NR AND  
SHORT TERM PDS.  
 
OUTLOOK...  
 
SATURDAY: SEAS AND WINDS EXPECTED TO STAY UNDER SCA CRITERIA. A FEW  
WIND GUSTS AROUND 20 KNOTS POSSIBLE SATURDAY AFTERNOON.  
 
SATURDAY NIGHT: SEAS APPROACHING FIVE FEET AT TIMES. WINDS BELOW SCA  
CRITERIA.  
 
SUNDAY THROUGH TUESDAY: FOUR FEET SEAS DECREASING LATE IN THE DAY.  
HOWEVER SEAS MAY APPROACH FOUR FEET AT OTHER TIMES IN THIS PERIOD.  
WINDS BELOW SCA CRITERIA.  
 

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

 
 

 
SYNOPSIS...GAINES  
NEAR TERM...NIERENBERG  
SHORT TERM...NIERENBERG  
LONG TERM...GAINES  
AVIATION...GAINES/NIERENBERG  
MARINE...GAINES/NIERENBERG  
 
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