660  
FXUS61 KPHI 040812  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
412 AM EDT SAT JUL 4 2015  
   
SYNOPSIS
 
 
LOW PRESSURE OVER SOUTHEAST VIRGINIA WILL MOVE OUT TO SEA  
SOUTHEAST OF CAPE COD BY THIS EVENING. WEAK HIGH PRESSURE FOLLOWS  
LATE TONIGHT AND SUNDAY, THEN SHIFTS OFFSHORE MONDAY. A WARM FRONT  
MOVES SLOWLY NORTHEAST THROUGH THE MID ATLANTIC STATES TUESDAY  
WITH A COLD FRONT TO FOLLOW LATE WEDNESDAY OR THURSDAY.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
THE UPPER LEVEL TROF IS PROGRESSING SLOWLY EASTWARD ACROSS THE  
GRTLKS AND OH VLY. EXTENSIVE MID CLOUDS AND AREAS OF SHOWERS HAVE  
SPREAD ACROSS THE FCST AREA AHEAD OF THE TROF AND NORTH OF THE QUASI-  
STNRY FRONTAL BOUNDARY EXTENDING W TO E ACROSS VA. SHOWERS WILL  
CONTINUE TO DEVELOP/SPREAD ACROSS THE AREA THIS MORNING...HWVR THE  
BEST CHC FOR THE EARLY MORN HOURS LOOKS TO BE N/W OF PHL BASED ON  
THE REGIONAL RADAR LOOP. LATER IN THE DAY AS LOW PRES MOVES EAST OF  
DELMARVA...POPS MAY BE MORE LIKELY S/E BUT CONFIDENCE IS NOT HIGH  
AT THIS TIME. CLOUD AND SHOWERS TODAY WILL LIMIT MAX TEMPS TO THE  
UPPER 60S N/W AND MID 70S S/E. CHANCE FOR PRECIP SHOULD DECREASE  
FROM W TO E FROM MID AFTERNOON ONWARD AS FORCING FOR UVV MOVES  
AWAY FROM THE AREA. HWVR CLOUDINESS WILL LINGER AS DRIER AIR WILL  
BE SMWHT SLOW TO FILTER IN BEHIND THE LOW.
 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/
 
 
FOR TONIGHT...THE UPPER TROF AXIS WILL CONT MOVING EWD AND OFFSHORE  
BY SUNDAY MORNING WITH DRIER AIR FILTERING IN BEHIND IT. WEAK HIGH  
PRES WILL BUILD IN AT THE SFC. ANY LINGERING SHOWERS NEAR THE COAST  
SHOULD MOVE OUT BEFORE DARK ALLOWING FOR FIREWORKS TO PROCEED.  
EVENING CLOUDS SHOULD CLEAR FROM THE NW OVER NIGHT WITH THE DRIER  
AIR COMING IN. WIND WILL BE RATHER LIGHT ALLOWING FOR MIN TEMPS  
GENLY IN THE 50S EXCEPT 60S IN DELMARVA.  
 

 
   
LONG TERM /SUNDAY THROUGH FRIDAY/
 
 
500MB: A TROUGH CENTERED NEAR THE TENNESSEE VALLEY SUNDAY WILL WEAKEN  
NORTHEASTWARD ACROSS THE MID ATLANTIC STATES TUESDAY. A WEAK WEST  
SOUTHWEST FLOW PREVAILS THEREAFTER WITH WEAK EMBEDDED DISTURBANCES.  
 
TEMPERATURES: CALENDAR DAY TEMPERATURES NEAR OR SLIGHTLY BELOW  
NORMAL ON SUNDAY WARM TO ALMOST 5 DEGREES ABOVE NORMAL TUESDAY  
AND WEDNESDAY AND POSSIBLY REMAIN ABOVE NORMAL THURSDAY AND  
FRIDAY.  
 
FORECAST BASIS: UNLESS OTHERWISE NOTED, THIS 330 AM SATURDAY JULY  
4TH FORECAST WAS GENERALLY A 50 50 BLEND OF THE 00Z/4 GFS/NAM MOS  
GUIDANCE SUNDAY-MONDAY, 00Z/4 MEX MOS MONDAY NIGHT AND TUESDAY,  
THEN THE 0521Z/4 WPC GRIDDED ELEMENTS OF MAX/MIN TEMP, 12 HOUR  
POP, 6 HOUR DEWPOINT- SKY-WIND FROM TUESDAY NIGHT THROUGH NEXT  
FRIDAY WITH THE EXCEPTION OF MAX TEMPS TUESDAY AND WEDNESDAY WHEN  
THE 00Z/4 MEX BLENDED WITH EVEN WARMER 00Z/4 ECMWF 2M TEMPS  
PREVAILED.  
 
THE DAILIES...  
 
SUNDAY...AFTER ANY EARLY MORNING PATCHY FOG DISSIPATES...SCT-BKN  
AOA 5000 FT. WEST WIND GUST 15 MPH. CONFIDENCE: ABOVE AVERAGE.  
 
MONDAY....INCREASING CLOUDS. ST/FOG POSSIBLE LATE MONDAY NIGHT?  
SOUTH WIND GUST 15 MPH MONDAY AFTERNOON. CONFIDENCE: ABOVE AVERAGE.  
 
TUESDAY...AREAS OF SHOWERS AND EMBEDDED TSTMS WITH PWAT OF 1.75 TO  
TO 2 INCHES, MLCAPE 1200J, AND WEAK STEERING WHICH COULD MEAN  
SEVERAL INTENSE TSTMS WITH EXCESSIVE SHORT DURATION RAINFALL (POOR  
DRAINAGE FLOODING FOR STARTERS). SOUTHERLY WIND GUST 20 MPH. NEAR  
90F PHILLY AREA. CONFIDENCE: ABOVE AVERAGE.  
 
WEDNESDAY...LIKELY A HOT DAY. TSTMS LATE IN THE DAY AHEAD OF THE  
APPROACHING AND EVENTUALLY SLOWING COLD FRONT. 1000J MLCAPE. COULD  
BE STRONG TSTMS E PA. HEAT INDEX RIGHT NOW MODELED 99 PHL AND NEAR  
100 DELMARVA. WILL BE REEVALUATED NEXT SEVERAL DAYS. NO HEAT  
INDEX ACTION ATTM IN THE MORNING HWO. CONFIDENCE: ABOVE AVERAGE.  
 
THURSDAY...UNCERTAINTY ON TIMING BUT TSTMS ARE IN THE FCST WITH  
ANOTHER SHORT WAVE PASSAGE. ALSO UNCERTAINTY ON TEMPS, DEPENDENT  
ON TIMING CONVECTIVE RELATED SKYCOVER. CONFIDENCE: AVERAGE OR  
BELOW AVERAGE.  
 
FRIDAY...PROBABLY DRYING OUT AFTER THURSDAYS PROBABLE SHORT WAVE  
PASSAGE. CONFIDENCE: AVERAGE OR BELOW AVERAGE.  
 

 
   
AVIATION /08Z SATURDAY THROUGH WEDNESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
VFR CONDS EARLY THIS MORNING WILL WORSEN SOMEWHAT AFTER DAYBREAK AS  
AREAS OF SHOWERS DEVELOP/SPREAD ACROSS THE REGION. SHOWERS ARE AHEAD  
OF A SHRTWV TROF MOVING EAST FROM THE OHIO VLY. THERE WILL BE  
PERIODS OF MVFR CIGS/VSBYS WITH SOME OF THE HEAVIER SHOWERS. CONDS  
SHOULD IMPROVE FROM MID/LATE AFTN ON INTO THE EVENING. CURRENT LIGHT  
SE WINDS WILL INCREASE SOME AND BACK TO THE NE AS LOW PRES DEVELOPS  
LATER THIS MORNING S OF DELMARVA AND THEN MOVES OFFSHORE.  
 
OUTLOOK...  
 
SUNDAY...VFR SCT-BKN AOA 5000 FT. WEST WIND MAX GUST 15 KT DURING  
THE AFTERNOON. PATCHY MVFR FOG POSSIBLE TO START THE DAY AND  
AGAIN LATE SUNDAY NIGHT. HIGH CONFIDENCE.  
 
MONDAY...VFR SCT-BKN AOA 5000 FT DURING THE DAY WITH A CHANCE OF  
IFR ST/FOG LATE MONDAY NIGHT AHEAD OF A WARM FRONT. SOUTHERLY  
WIND MAX GUST 15 KT DURING THE AFTERNOON. HIGH CONFIDENCE.  
 
TUESDAY...VFR SCT-BKN AOA 5000 FT WITH SCT TSTMS AND ASSTD BRIEF  
IFR CONDS IN HEAVY RAIN, ESPECIALLY E PA DURING THE AFTN-EVENING.  
HIGH CONFIDENCE.  
 
WED...VFR SCT-BKN WITH A PRETTY GOOD CHANCE OF AFTN OR NIGHTTIME  
TSTMS. IFR CONDS POSSIBLE IN TSTMS. CONFIDENCE: AVERAGE OR ABOVE  
AVERAGE.  
 

 
   
MARINE
 
 
SE WINDS EARLY THIS MORNING WILL BACK TO THE E AND NE LATER THIS  
MORNING AND AFTN AS LOW PRES DEVELOPS EAST OF DELMARVA. WIND  
SPEED AND WAVES WILL INCREASE SOME TODAY BUT ARE EXPECTED TO  
REMAIN BELOW SCA LEVELS. WINDS SHOULD DECREASE AND BECOME NLY  
TONIGHT AS THE LOW PRES MOVES AWAY AND WEAK HIGH PRES BUILDS IN.  
 
OUTLOOK...  
 
SUNDAY NIGHT THRU WEDNESDAY...NO MARINE FLAGS ARE ANTICIPATED AS  
OF THIS WRITING. CONFIDENCE: AVERAGE  
 

 
   
TIDES/COASTAL FLOODING
 
 
TONIGHT (SATURDAY EVENING). WHILE SOME TIDAL LOCATIONS MAY APPROACH  
MINOR TIDAL FLOODING LEVELS, CURRENT DATA INDICATES THEY WILL REMAIN  
BELOW ADVISORY THRESHOLD.  
 

 
   
RIP CURRENTS
 
 
THERE IS A MODERATE RISK OF RIP CURRENTS ON SATURDAY ALONG THE  
NEW JERSEY SHORE GIVEN THE CONTINUED ONSHORE FLOW AND MODERATE  
PERIOD SWELLS. THE RISK IS LOW FOR DELAWARE.  
 

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

 
 

 
SYNOPSIS...DRAG  
NEAR TERM...AMC 412  
SHORT TERM...AMC 412  
LONG TERM...DRAG  
AVIATION...AMC/DRAG  
MARINE...AMC/DRAG  
TIDES/COASTAL FLOODING...412  
RIP CURRENTS...  
 
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