Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 200806 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 406 AM EDT WED AUG 20 2014 .SYNOPSIS... AN AREA OF LOW PRESSURE AND ASSOCIATED FRONTAL BOUNDARY WILL MOVE THROUGH THE GREAT LAKES REGION TODAY AND WEAKEN AS THEY MOVE INTO UPSTATE NEW YORK THURSDAY. A SECOND AREA OF LOW PRESSURE WILL DEVELOP NEAR THE CHESAPEAKE BAY THURSDAY NIGHT ALONG THE STATIONARY BOUNDARY TO OUR SOUTH. HIGH PRESSURE WILL BUILD DOWN ALONG THE EAST COAST OUT OF EASTERN CANADA LATER THIS WEEKEND INTO NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... SURFACE LOW PRESSURE, WHICH WAS LOCATED ABOUT 250 MI OFF THE SOUTHEAST VA COAST EARLY THIS MORNING, WILL CONTINUE TO PULL AWAY FROM THE EASTERN SEABOARD. ANOTHER AREA OF LOW PRESSURE THAT IS CURRENTLY LOCATED NEAR LAKE MICHIGAN WILL MOVE ACROSS THE GREAT LAKES REGION TODAY. BOTH OF THESE LOWS DEVELOPED ALONG A STALLED FRONT. HIGH PRESSURE RIDGING DOWN THE NEW ENGLAND AND MID-ATLANTIC SEABOARD WILL KEEP THIS FRONTAL BOUNDARY SOUTH AND WEST OF THE FORECAST AREA TODAY. WINDS WILL BE LIGHT/VARIABLE TO START THE DAY WITH THE SFC RIDGE AXIS OVERHEAD. WINDS THEN VEER OUT OF THE SOUTHEAST ALONG THE COAST AND SOUTH FARTHER INLAND THIS AFTERNOON AS THE RIDGE SHIFTS OFFSHORE. MID CLOUDS STREAMING IN FROM THE WEST WILL RESULT IN A MOSTLY CLOUDY START TO THE DAY FOR NJ/PA. THERE WILL BE OPPORTUNITY FOR CLOUDS TO SCATTER OUT A BIT LATER THIS MORNING, ESPECIALLY ALONG AND EAST OF I-95. THE WARMEST TEMPS THIS AFTERNOON ARE THUS FORECAST FOR THE URBAN I-95 CORRIDOR AND EASTERN MD (HIGHS IN THE MID 80S). DESPITE MORE SUNSHINE FARTHER EAST, SLIGHTLY COOLER CONDITIONS CAN BE EXPECTED WITH AN ONSHORE FLOW. A COMPLEX OF SHOWERS AND STORMS ASSOCIATED WITH A MID-LVL SHORTWAVE TROUGH OUT AHEAD OF THE GREAT LAKES LOW SHOULD WEAKEN THIS MORNING AS IT MOVES EASTWARD INTO AN INCREASINGLY STABLE AIRMASS THAT RESIDES EAST OF THE OH VLY. THIS IMPULSE IS FORECAST TO REACH CENTRAL PA BY MIDDAY AND EASTERN PA BETWEEN 18Z-00Z. THERE IS A POTENTIAL FOR CONVECTION TO REDEVELOP AHEAD OF THE SHORTWAVE TROUGH DURING THE MID TO LATE AFTERNOON OVER THE HIGHER TERRAIN. WITH MODELS CONTINUING TO SHOW STRONGER STATIC STABILITY FARTHER EAST ACROSS THE CWA, CONFINED PRECIP TO WEST OF I-95 FOR THIS AFTERNOON. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM THURSDAY/... HIGH PRESSURE WILL RETREAT OFF THE EASTERN SEABOARD TONIGHT AS THE ABOVEMENTIONED SHORTWAVE TROUGH MOVES INTO THE AREA FROM THE WEST. EXPECT SHOWERS AND PERHAPS A FEW THUNDERSTORMS WEST OF THE DIVIDE. FORECAST IS CONSERVATIVE IN REGARDS TO HOW FAR EAST SHOWERS AND STORMS WERE MENTIONED AS MODELS GENERALLY SHOW CONVECTION DECAYING AS IT MOVES EASTWARD INTO A MORE STABLE AIRMASS OVER NJ/DE. CLOUDS COVER, WHICH WILL INCREASES ACROSS THE ENTIRE AREA WITH THE APPROACH OF THE TROUGH, WILL LIMIT RADIATIONAL COOLING TONIGHT. OFFICIAL MIN TEMP FORECAST SLIGHTLY WARMER THAN MOS GUIDANCE. && .LONG TERM /THURSDAY THROUGH TUESDAY/... THE LONG TERM FORECAST STARTS OFF WITH RAIN CHANCES, BEFORE A DRYING OUT PERIOD SETS IN ACROSS THE AREA. ON THURSDAY, THE AREA OF LOW PRESSURE AND ASSOCIATED FRONTAL BOUNDARY TO OUR NORTHWEST WILL WEAKEN AS THEY MOVE OUT OF THE GREAT LAKES AND INTO UPSTATE NEW YORK. HOWEVER, THE MID/UPPER-LEVEL LOW WILL SWING THROUGH THE NORTHEAST AND MID-ATLANTIC THROUGH THURSDAY AND THURSDAY NIGHT. THIS WILL ALLOW FOR SHOWERS, AND WITH A FAIR AMOUNT OF INSTABILITY, SCATTERED THUNDERSTORMS TO DEVELOP AND MOVE INTO THE AREA. THERE IS NOT MUCH SHEAR OR MUCH OF A WIND FIELD, SO WE DO NOT EXPECT SEVERE WEATHER AT THIS TIME. PW VALUES ARE GENERALLY FORECAST AROUND 1.5-1.75 INCHES, SO SOME SHOWERS/STORMS COULD PRODUCE A PERIOD OF MODERATE TO HEAVY RAINFALL. THURSDAY NIGHT, A SECOND AREA OF SURFACE LOW PRESSURE IS FORECAST TO DEVELOP NEAR THE CHESAPEAKE BAY ALONG THE STATIONARY BOUNDARY TO OUR SOUTH. IT IS POSSIBLE THAT THIS MAY HELP KEEP A FOCUS FOR PRECIPITATION THURSDAY NIGHT, BEFORE IT SAGS TO OUR SOUTH. FOR FRIDAY INTO THE WEEKEND, THE MID/UPPER LOW WILL REMAIN TO OUR NORTHEAST, KEEPING A NORTHWEST FLOW ALOFT ACROSS OUR AREA. MEANWHILE, HIGH PRESSURE WILL BEGIN BUILDING DOWN ACROSS THE EAST COAST FROM EASTERN CANADA. BEFORE THE HIGH TAKES FULL CONTROL OF THE WEATHER, THERE WILL REMAIN A CHANCE OF SCATTERED SHOWERS FRIDAY AND SATURDAY AS THERE MAY BE A FEW SHORT WAVE/VORT MAXES THAT AFFECT THE AREA IN THE NORTHWEST FLOW ALOFT. BY SUNDAY INTO EARLY NEXT WEEK, THE SURFACE HIGH BUILDS FURTHER INTO THE MID-ATLANTIC REGION, WHICH SHOULD BRING DRY WEATHER TO THE AREA. HIGHS ARE EXPECTED TO START OUT CLOSE TO OR SLIGHTLY ABOVE NORMAL THURSDAY INTO FRIDAY, BUT AS THE HIGH BUILDS DOWN OUT OF EASTERN CANADA AND THE NORTHWEST FLOW ALOFT REMAINS ACROSS THE AREA OVER THE WEEKEND, 925/850 MB TEMPS AND THICKNESSES LOWER. THIS WILL ALLOW FOR SLIGHTLY BELOW NORMAL TEMPERATURES OVER THE WEEKEND. AS WE MOVE INTO EARLY NEXT WEEK, WE SHOULD START TO GET MORE OF A RETURN SURFACE FLOW AND RIDGING ALOFT BEGINS TO TAKE PLACE ONCE AGAIN, ALLOWING FOR REBOUNDING TEMPERATURES. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS EXPECTED TODAY AND TONIGHT. BKN MID-LVL CIGS IMPACTING MOST OF THE TERMINALS EARLY THIS MORNING. EXPECT THESE CLOUDS TO SCT OUT TOWARD MIDDAY BEFORE CLOUDS INCREASE ACROSS THE WESTERN TERMINALS THIS AFTN AND THE REST OF THE AREA TERMINALS TONIGHT. PROB30 GROUP FOR SHRA ADDED FOR RDG/ABE LATE THIS AFTN AND EARLY THIS EVE WHEN A DISTURBANCE MOVES THRU. WHILE TSRA CANNOT BE RULED OUT, COVERAGE/CONFIDENCE TOO LOW TO MENTION IN TAFS ATTM. SAME GOES FOR SHRA CHANCES FARTHER DOWNSTREAM INTO PHL AND TO THE EAST. OUTLOOK... THURSDAY-THURSDAY NIGHT...GENERALLY VFR. CHANCE OF SHOWERS AND THUNDERSTORMS WHICH MAY LOWER CIGS/VSBYS. FRIDAY-SUNDAY...PERIODS OF LOW END VFR OR MVFR CIGS POSSIBLE WITH A CHANCE OF SHOWERS, ESPECIALLY FRIDAY INTO SATURDAY. && .MARINE... EASTERLY WINDS BETWEEN 5-10 KT THIS MORNING WILL BECOME SOUTHEASTERLY THIS AFTN AS HIPRES MOVES OFFSHORE. LOCALLY HIGHER WINDS TO 15 KT POSSIBLE THIS AFTN AND EVE. OUTLOOK... THURSDAY-FRIDAY NIGHT...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED. SATURDAY-SUNDAY...SEAS MAY BEGIN TO APPROACH SMALL CRAFT ADVISORY LEVELS AS A LONG FETCH DEVELOPS AROUND HIGH PRESSURE BUILDING IN FROM THE NORTHEAST OUT OF EASTERN CANADA. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...ROBERTSON NEAR TERM...KLEIN SHORT TERM...KLEIN LONG TERM...ROBERTSON AVIATION...KLEIN/ROBERTSON MARINE...KLEIN/ROBERTSON

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