486  
FXUS61 KPHI 212245  
AFDPHI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ  
645 PM EDT THU AUG 21 2014  
   
SYNOPSIS
 
 
WEAK LOW PRESSURE WILL CROSS THE REGION TONIGHT THROUGH FRIDAY  
NIGHT AND THEN MOVE OFF THE COAST SATURDAY. HIGH PRESSURE WILL  
BUILD ACROSS THE AREA THIS WEEKEND AND REMAIN IN CONTROL OF THE  
WEATHER INTO NEXT WEEK. A COLD FRONT WILL APPROACH THE AREA NEXT  
WEDNESDAY.  
 

 
   
NEAR TERM /UNTIL 6 AM FRIDAY MORNING/
 
 
STABLE AIR WAS CONTINUING TO ADVECT OFF THE OCEAN EARLY THIS  
EVENING. DEW POINT READINGS WERE DROPPING INTO THE UPPER 50S AND  
LOWER 60S IN NEW JERSEY. MEANWHILE, CONDITIONS REMAINED UNSTABLE  
ON THE WESTERN SIDE OF OUR FORECAST AREA.  
 
CONDITIONS ARE FORECAST TO BECOME INCREASINGLY STABLE DURING THE  
EVENING WITH THE GRADUAL LOSS OF DAYTIME HEATING AND THE  
CONTINUED ONSHORE FLOW. WE HAVE ADJUSTED THE FORECAST TO REMOVE  
THE THUNDERSTORMS FROM ALL BUT TWO AREAS.  
 
WE WILL KEEP THE MENTION OF THUNDERSTORMS WITH HEAVY RAINFALL  
ACROSS OUR FAR NORTHERN COUNTIES FOR THIS EVENING TO ACCOUNT FOR  
THE CONVECTION MOVING ACROSS NORTHEASTERN PENNSYLVANIA AND INTO  
NORTHERN NEW JERSEY. THERE MAY BE SOME STRONG WIND GUSTS AND HAIL  
THERE, AS WELL. ALSO, WE WILL MAINTAIN THE EVENING THUNDERSTORM  
FORECAST WITH THE POTENTIAL FOR HEAVY RAINFALL IN NORTHEASTERN  
MARYLAND AND CENTRAL AND SOUTHERN DELAWARE AS SOME OF THE  
CONVECTION IN THE LOWER SUSQUEHANNA RIVER VALLEY MAY SLIDE  
SOUTHEASTWARD INTO THAT AREA.  
 
A MID LEVEL SHORT WAVE THAT WAS LOCATED OVER THE EASTERN GREAT  
LAKES REGION EARLY THIS EVENING SHOULD CONTINUE TO PROGRESS  
SOUTHEASTWARD AND IT IS ANTICIPATED TO PASS OVERHEAD LATE TONIGHT.  
AS A RESULT, WE WILL MAINTAIN SCATTERED SHOWERS THROUGHOUT OUR  
FORECAST AREA FOR TONIGHT.  
 
TEMPERATURES ARE EXPECTED TO DROP INTO THE 60S OVERNIGHT WITH A  
LIGHT SOUTH TO EAST WIND.  
 

 
   
SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/
 
 
1000J OF MLCAPE AND SLIGHTLY STRONGER 0-6KM BULK SHEAR CUES  
INTEREST IN CONVECTION FRI AFTN. SREF HAS DECENT PROBS FOR  
SHOWERS...ESPECIALLY E PA...S NJ AND THE DELMARVA. FOR NOW HAVE  
PLAYED THE SHOWER AND TSTM RISK CONSERVATIVELY AND MAINTAINED THE  
330 AM THURSDAY FCST POPS FOR FRIDAY...ABOUT 10 PCT BELOW THE  
12Z/21 GFS/NAM MOS BLEND.  
 
IT WILL BE SLIGHTLY COOLER AS THE FLOW TURNS MORE EASTERLY AS THE  
SFC LOW CONSOLIDATES TO THE S OF THE DELMARVA.  
 
FCST BASIS: TEMPS/DEWS/WINDS ARE A 50 50 BLEND OF THE 12Z/21  
GFS/NAM MOS.  
 

 
   
LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/
 
 
THE AREA WILL CONTINUE TO BE UNDER THE INFLUENCE OF THE WEAK  
UPPER LOW AND SFC LOW THU NIGHT AND INTO FRIDAY. SCT SHOWERS AND A  
FEW TSTMS WILL BE ACROSS MOST AREAS THU EVENING AND THEN DIMINISH  
OVERNIGHT...A COUPLE LEFTOVER SHOWERS WILL DEVELOP SAT MOSTLY  
ACROSS THE DELMARVA...SE PA AND SRN NJ. CHC FOR SHOWERS ARE ONLY  
IN THE CHC RANGE HOWEVER. A FEW DOWNPOURS ARE STILL POSSIBLE THU  
NIGHT WITH THE HIGHER PWATS STILL ACROSS THE SRN AREAS. LOWS THU  
NIGHT WILL MOSTLY BE IN THE LOW 60S ACROSS THE NORTH AND MID/UPPER  
60S ELSEWHERE. HIGHS SAT IN THE UPPER 70S/LOW 80S SOUTH AND LOW TO  
MID 70S NORTH. DRIER AIR WILL CONTINUE TO PUSH IN FROM NORTH TO  
SOUTH SAT.  
 
AN UPPER RIDGE BUILDS UP TO THE WEST OF THE AREA THIS WEEKEND AND  
THEN ROTATES ACROSS THE AREA EARLY NEXT WEEK. SFC HIGH PRESSURE  
WILL MOVE SLOWLY IN TANDEM WITH THE UPPER HIGH. THIS WILL PRODUCE  
A PERIOD OF DRY WEATHER FOR OUR REGION. POPS FOR SAT NIGHT THRU  
NEXT WEN NIGHT ARE SUB-15PCT RANGE FOR THE ENTIRE AREA.  
TEMPERATURES WILL BE A FEW DEGREES BELOW NORMAL SUN/MON...NEAR  
NORMAL TUE...AND THEN A BIT ABOVE NORMAL WED/THU. HUMIDITY LEVELS  
WILL BE COMFORTABLE THROUGH MUCH OF THE PERIOD...BUT WILL TREND UP  
TOWARD THE MIDDLE OF NEXT WEEK.  
 

 
   
AVIATION /00Z FRIDAY THROUGH TUESDAY/
 
 
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,  
KILG, KMIV, KACY AND SURROUNDING AREAS.  
 
SCATTERED SHOWERS ARE ANTICIPATED FOR TONIGHT. ISOLATED  
THUNDERSTORMS ARE EXPECTED FOR THIS EVENING TO THE NORTH OF KABE  
AND KTTN AND TO THE WEST AND SOUTHWEST OF KPHL AND KILG.  
CONDITIONS SHOULD BE GENERALLY VFR THROUGH 0400Z EXCEPT THEY MAY  
LOWER TO MVFR IN RAIN SHOWERS.  
 
MVFR CONDITIONS ARE EXPECTED TO PREVAIL FROM LATE TONIGHT INTO  
FRIDAY MORNING. SOME SPOTS COULD FALL TO IFR DEPENDING UPON THE  
EXTENT OF ANY STRATUS AND FOG DEVELOPMENT ALONG WITH ADDITIONAL  
SHOWER ACTIVITY. MAINLY VFR CONDITIONS ARE EXPECTED TO RETURN FOR  
FRIDAY AFTERNOON AND THERE IS A CHANCE OF SHOWERS AND  
THUNDERSTORMS AT THAT TIME.  
 
THE WIND SHOULD BACK FROM THE SOUTH AND SOUTHEAST TO THE EAST  
DURING THE TAF PERIOD. SPEEDS ARE EXPECTED TO BE MAINLY LESS THAN  
10 KNOTS  
 
OUTLOOK...  
FRI NIGHT THRU SAT...MOSTLY VFR BUT SCT SHOWERS MAY BRING LOWER  
CONDITIONS.  
 
SAT NIGHT THRU TUESDAY...VFR EXPECTED.  
 

 
   
MARINE
 
 
SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED THROUGH FRIDAY WITH  
SEAS 3 FEET OR LESS AND SOUTH TO SOUTHEAST WINDS 5 TO 10 KNOTS  
BECOMING EASTERLY FRIDAY.  
 
WE'VE NOT SEEN ANY NEW MAREPS THIS WEEK FROM MARINERS IN OUR EASY  
USE (INTERNET AND/OR SMART PHONE) LINK  
WWW.WEATHER.GOV/PHI/MAROBSFORM THIS HAS BEEN DERIVED FOR THE  
MARINER TO EASILY POST INFO INSTANTLY TO THE NWS FOR USE IN OUR  
MARINE PRODUCTS.  
 
OUTLOOK...  
THU NIGHT THRU FRI NIGHT...SUB SCA CONDITIONS WITH SCT SHOWERS.  
 
SAT AND SAT NIGHT...LOW END SCA CONDITIONS EXPECTED ON THE OCEAN.  
FAIR WEATHER.  
 
SUN THRU TUE...SUB-SCA CONDITIONS WITH FAIR WEATHER.  
 

 
   
CLIMATE
 
 
WE RCD INQUIRY ON HOW THE CLIMATE PROGRAM SELECTS FOR OUR 530 PM  
CLI. OUR PROGRAM SEARCHES MAX/MIN TEMP DATA FOR THE DAY ENDING 5PM  
SHARP. THAT DATA IS INGESTED INTO THE 530 PM POSTED CLI. IF A MAX  
TEMP OCCURS THEREAFTER...IT IS REFLECTED IN THE END OF DAY SUMMARY  
POSTS AROUND 230 AM EDT THE NEXT DAY AND ALSO YOU CAN CHECK THE 8  
PM RTPPHI WHICH POSTS AROUND 815 PM EDT.  
 

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

 
 

 
 
SYNOPSIS...O'HARA  
NEAR TERM...IOVINO  
SHORT TERM...DRAG  
LONG TERM...O'HARA  
AVIATION...IOVINO/O'HARA  
MARINE...DRAG/O'HARA  
CLIMATE...DRAG  
 
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