746  
FXUS61 KPHI 281024  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
624 AM EDT THU JUL 28 2016  
   
SYNOPSIS
 
 
HIGH PRESSURE WILL REMAIN TO THE NORTH THROUGH FRIDAY. A WEAK  
FRONT WILL STALL TO OUR SOUTH AND AREAS OF LOW PRESSURE WILL  
DEVELOP ALONG THIS FRONT THROUGH THE WEEKEND AND BRING PERIODS OF  
SHOWERS AND THUNDERSTORMS.  
 

 
   
NEAR TERM /UNTIL 6 PM THIS EVENING/
 
 
THE SKY WAS CLEAR OVER OUR NORTHERN COUNTIES AROUND 6:15 AM AND  
PARTLY CLOUDY OVER THE SOUTH. LOCALIZED FOG EARLY THIS MORNING  
SHOULD DISSIPATE QUICKLY. DEBRIS CLOUDS FROM CONVECTION OVER THE  
OHIO RIVER VALLEY EARLY THIS MORNING SHOULD OVERSPREAD OUR REGION  
TODAY. ALSO, WE ARE ANTICIPATING THE DEVELOPMENT OF DAYTIME  
CUMULUS.  
 
IT APPEARS AS THOUGH OUR FORECAST AREA WILL REMAIN PRECIPITATION  
FREE FOR THIS MORNING. HOWEVER, INCREASING INSTABILITY IN OUR  
SOUTHERN COUNTIES SHOULD LEAD TO THE DEVELOPMENT OF SCATTERED  
AFTERNOON SHOWERS AND THUNDERSTORMS THERE. THE STORM PREDICTION  
CENTER HAS PLACED NORTHEASTERN MARYLAND, DELAWARE AND SOUTHERN NEW  
JERSEY UNDER ITS MARGINAL TO SLIGHT RISK DESIGNATIONS FOR SEVERE  
WEATHER DUE TO THE EXPECTED INSTABILITY (AROUND 1000 TO 2000 J/KG  
MIXED LAYER CAPE) ALONG WITH A MODERATELY STRONG WESTERLY MID  
LEVEL FLOW.  
 
A POOL OF DEEP ATMOSPHERIC MOISTURE WAS LOCATED OVER PARTS OF  
NORTH CAROLINA, VIRGINIA AND THE ADJACENT WATERS EARLY THIS  
MORNING. IT IS EXPECTED TO DRIFT NORTHWARD TODAY. PRECIPITABLE  
WATER VALUES ARE ANTICIPATED TO INCREASE AROUND 2.2 TO 2.4 INCHES  
IN OUR SOUTHERN COUNTIES BY THIS EVENING. THERE WILL BE THE  
POTENTIAL FOR HEAVY DOWNPOURS.  
 
MAXIMUM TEMPERATURES SHOULD FAVOR THE LOWER 90S IN OUR REGION.  
READINGS SHOULD NOT GET OUT OF THE 80S IN THE ELEVATED TERRAIN OF  
THE POCONOS AND NORTHWESTERN NEW JERSEY, AND ALONG THE IMMEDIATE  
COAST. HEAT INDEX VALUES ARE EXPECTED TO REMAIN SEVERAL DEGREES  
BELOW THE EXCESSIVE HEAT CRITERION FOR OUR NORTHERN COUNTIES AND  
JUST BELOW THE CRITERIA FOR THE URBAN CORRIDOR AND FOR OUR  
SOUTHERN COUNTIES.  
 
THE SYNOPTIC WIND SHOULD BE LIGHT ALLOWING LOCAL INFLUENCES TO  
DRIVE TODAY'S WIND DIRECTION. SPEEDS SHOULD BE MOSTLY LESS THAN 10  
MPH.  
 

 
   
SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/
 
 
PRECIPITABLE WATER VALUES OF 2.2 TO 2.4 INCHES WILL OVERSPREAD  
OUR FORECAST AREA FROM THE SOUTH FOR TONIGHT. CONDITIONS ARE  
EXPECTED TO REMAIN UNSTABLE, ESPECIALLY ACROSS OUR SOUTHERN  
COUNTIES. ALSO, SURFACE LOW PRESSURE APPROACHING FROM THE WEST  
WILL RESULT IN THE DEVELOPMENT OF A FAVORABLE LOW LEVEL WIND  
PROFILE FOR ORGANIZED CONVECTION TONIGHT. THE SURFACE WIND SHOULD  
BEGIN TO FAVOR THE EAST TO SOUTH QUADRANT LATE TONIGHT, ESPECIALLY  
ON THE COASTAL PLAIN, WHILE WINDS AROUND 800 HPA WILL BE FROM THE  
SOUTHWEST.  
 
THE VERY HIGH PRECIPITABLE WATER VALUES SHOULD RESULT IN HEAVY  
RAINFALL IN ANY ORGANIZED CONVECTION. AS A RESULT, THE FLASH FLOOD  
WATCH REMAINS IN EFFECT FOR SOUTHEASTERN PENNSYLVANIA, CENTRAL AND  
SOUTHERN NEW JERSEY, DELAWARE AND NORTHEASTERN MARYLAND.  
 
THE CLOUD COVER AND HIGH HUMIDITY WILL KEEP TEMPERATURES FROM  
FALLING BELOW THE 70S FOR TONIGHT EXCEPT IN THE POCONOS AND FAR  
NORTHERN NEW JERSEY.  
 

 
   
LONG TERM /FRIDAY THROUGH WEDNESDAY/
 
 
AN AREA OF LOW PRES WILL RIDE ALG THE STALLED FRONT AND BRING  
RAIN TO THE AREA ON FRI. THERE IS STILL SOME DISAGREEMENT IN THE  
MDLS AS TO THE EXTENT OF THE RAIN AND THE LOCATIONS OF THE  
HEAVIEST, WITH THE GFS INDICATING MOST RAIN N AND VERY LITTLE S  
AND THE ECMWF HAVING A MORE WIDESPREAD EVENT. FOR NOW, WILL JUST  
CARRY HIGH CHC EVERYWHERE.  
 
MDLS THEN CLEAR THINGS OUT FRI NIGHT INTO EARLY SAT, SO HAVE  
LOWERED POPS AND REMOVED THEM FOR THE FIRST PART OF SAT.  
 
THEN THERE IS MORE DISAGREEMENT IN THE MDLS INTO SAT AS BOTH MDLS  
DEVELOP PRECIP AGAIN BUT THE ECMWF IS MORE WIDESPREAD INTO EARLY  
SUN. HOWEVER, BY LATER SUN, BOTH THE GFS AND ECMWF HAS ANOTHER  
GOOD SHOT OF PRECIP OVER THE AREA AS ANOTHER WAVE MOVES BY ALG THE  
FRONT.  
 
AFTER SUN, THE ECMWF IS MUCH DRIER THROUGH MIDWEEK, KEEPING MOST  
OF THE PERIOD DRY, WHILE THE GFS KEEPS MON WITH A CHC OF PRECIP  
AND DIURNAL STUFF ON TUE. THE DRIER ECMWF SOLN IS SUPPORTED BY THE  
CMC, SO HAVE LEANED THE FCST IN THAT DIRECTION ATTM.  
 
TEMPS LOOK TO BE A BIT COOLER THAN WE HAVE HAD RECENTLY, WITH  
TEMPS NOT EXPECTED TO HIT 90 DEGREES IN MANY AREAS THRU THE  
EXTENDD PD.  
 

 
   
AVIATION /12Z THURSDAY THROUGH MONDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
THERE WILL BE PATCHY MVFR/IFR CEILING AND VISIBILITY RESTRICTIONS  
EARLY THIS MORNING. OTHERWISE MAINLY VFR CONDITIONS ARE EXPECTED  
FOR TODAY. SCATTERED SHOWERS AND THUNDERSTORMS ARE FORECAST TO  
DEVELOP FOR THIS AFTERNOON, ESPECIALLY IN AREAS TO THE WEST AND  
SOUTH OF PHILADELPHIA. WE HAVE NOT INCLUDED THEIR MENTION IN ANY  
OF OUR TAFS DUE TO THE UNCERTAINTY REGARDING THEIR COVERAGE AND  
TIMING AT THIS POINT.  
 
DETERIORATING CONDITIONS ARE ANTICIPATED FOR TONIGHT AS SHOWERS  
AND THUNDERSTORMS BECOME MORE NUMEROUS IN OUR REGION. THE RAIN IS  
EXPECTED TO BECOME HEAVY AT TIMES.  
 
A LIGHT AND VARIABLE WIND THIS MORNING MAY SETTLE INTO THE  
SOUTHWEST AND SOUTH FOR THIS AFTERNOON AT LESS THAN 10 KNOTS. A  
LIGHT SOUTHERLY FLOW THIS EVENING MAY BEGIN TO BACK TOWARD THE  
SOUTHEAST OR EAST LATE TONIGHT.  
 
OUTLOOK...  
FRI THROUGH SUN...SHRA/TSRA WILL LOWER CIGS/VSBYS AT TIMES  
OTHERWISE VFR EXPECTED. MODERATE CONFIDENCE.  
 
MON...MAINLY VFR. MODERATE CONFIDENCE.  
 

 
   
MARINE
 
 
THE WIND DIRECTION IS FORECAST TO FAVOR THE SOUTH FOR TODAY WITH  
SPEEDS AROUND 10 KNOTS OR LESS. THE DIRECTION IS EXPECTED TO BACK  
TOWARD THE SOUTHEAST FOR TONIGHT.  
 
WAVE HEIGHTS ON OUR OCEAN WATERS WILL BE 2 FEET OR LESS AND WAVES  
ON DELAWARE BAY SHOULD BE 1 FOOT OR LESS.  
 
SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE FOR THIS  
AFTERNOON WITH NUMEROUS SHOWERS AND THUNDERSTORMS ANTICIPATED FOR  
TONIGHT.  
 
OUTLOOK...  
FRI THROUGH MON...THERE IS A CHANCE OF MARGINAL SCA CONDS FRI  
NIGHT INTO ERLY SAT, BUT CONFIDENCE IS LOW. OTHERWISE, NO MARINE  
HEADLINES ARE ANTICIPATED THRU THE PD.  
 
RIP CURRENTS...  
THERE IS A LOW RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS  
FOR TODAY DUE TO THE RELATIVELY LIGHT WIND AND TRANQUIL SEAS.  
 
THE PROBABLY RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS  
ON FRIDAY IS ALSO LOW.  
 

 
   
PHI WATCHES/WARNINGS/ADVISORIES
 
 
PA...FLASH FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH FRIDAY  
EVENING FOR PAZ070-071-101>106.  
NJ...FLASH FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH FRIDAY  
EVENING FOR NJZ009-010-012>027.  
DE...FLASH FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH FRIDAY  
EVENING FOR DEZ001>004.  
MD...FLASH FLOOD WATCH FROM 6 PM EDT THIS EVENING THROUGH FRIDAY  
EVENING FOR MDZ008-012-015-019-020.  
MARINE...NONE.  
 

 
 

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