Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 261152 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 752 AM EDT SAT JUL 26 2014 .SYNOPSIS... A WARM FRONT WILL MOVE NORTH ACROSS THE OHIO VALLEY AND MID-ATLANTIC TODAY AND TONIGHT. THIS WARM FRONT WILL THEN PUSH NORTH OF THE REGION EARLY ON SUNDAY. A COLD FRONTAL BOUNDARY WITH AN ASSOCIATED LOW PRESSURE SYSTEM THEN WILL SWEEP FROM WEST TO EAST ACROSS THE REGION ON MONDAY. THIS WILL BE FOLLOWED BY A HIGH PRESSURE SYSTEM WHICH WILL BUILD INTO AND PASS THROUGH THE REGION FOR THE MIDDLE AND LATER HALF OF NEXT WEEK. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... THE TREND OF THE STRONG SHORT WAVE BOTH IN MODELING ON RADAR HAS BECOME WETTER. WE ARE DOING AN EARLY UPDATE TO EXPAND THE MENTION OF SHOWERS EASTWARD AND ALSO CARRYING HIGHER POPS. HIGH PRES WILL MOVE TO THE E TODAY, BUT WE SHUD STILL HAVE A DRY OR MAINLY DRY DAY. AN AREA OF LOW PRES NR THE GRTLKS WILL MOVE SLOWLY EWD AND ITS ASSOCD WMFNT WILL MOVE THRU LATE. AS THE WMFNT APPROACHES, THERE CUD BE SOME SHWRS/TSRA. THE GUID SUGGESTS THE BEST CHCS ARE S PRIOR TO SUNSET. WILL KEEP SOME LOW CHC POPS IN THESE LOCATIONS. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/... THE AFOREMENTIONED AREA OF LOW PRESSURE WILL DROP SEWD TONIGHT AND ITS ASSOCD CDFNT WILL APPROACH FROM THE W. THERE ARE SOME DIFFS IN THE MDL GUID AS WE APPROACH THE END OF THE SHORT TERM PD WRT POPS. OVERALL, THE GFS IS THE WETTEST MDL AND MUCH WETTER TWD 12Z SUN. THE ECMWF IS DRY AT THE BEGINNING OF THE PD AND IMPLIES SOME QPF TWD THE END OF THE PD. THE NAM/WRF IS SUPPORTIVE OF THE DRIER ECMWF AND THE CMC IS ALMOST COMPLETELY DRY, LEAVING THE GFS AS THE WET OUTLIER. THEREFORE, WILL JUST CARRY SOME SCHC OR LOW CHC POPS INTO THE OVERNIGHT, AND SOME LOW QPF AS WELL. THERE ARE ALSO SOME DIFFS ON THE AREAS THAT WOULD SEE ANY QPF, WITH SOME MDLS SUGGESTING S AND OTHERS N. THE BEST CHCS FOR PRECIP ON SUN WILL BE AFTER DAYBREAK. && .LONG TERM /SUNDAY THROUGH FRIDAY/... SUNDAY: CONTINUED WEST-SOUTHWEST FLOW AS THE WARM FRONT PUSHES THROUGH THE REGION. TWO POTENTIAL AREAS OF CONVECTION MAY BE IN PROGRESS BY THIS POINT TO START THE DAY. THE FIRST IS LIKELY TO BE LOCATED TO OUR NORTHEAST IN ASSOCIATION WITH A SHORTWAVE AND THE SECOND OVER THE OHIO VALLEY WHERE ANOTHER SHORTWAVE COUPLED WITH VERY FAVORABLE JET DYNAMICS ARE LIKELY TO LEAD TO A MCS. THESE AREAS OF THUNDERSTORMS MAY PRODUCE SOME DEBRIS CLOUDS THROUGHOUT THE DAY ACROSS THE REGION. THE THUNDERSTORM CLUSTER OVER THE OHIO VALLEY IN THE MORNING MAY REDEVELOP FURTHER EAST IN THE AFTERNOON ACROSS OUR SOUTHERN HALF OF THE REGION AS SHOWN ON THE 00Z HIRES NAM. SEVERAL PAST GFS RUNS HAVE HINTED AT THIS AS WELL. MOST OF THE OPERATIONAL MODELS (ECMWF,GFS,CMC,UKMET 00Z RUNS) AND THE RGEM GENERATE ANOTHER CLUSTER OF STORMS OVER THE EASTERN OHIO VALLEY SUNDAY AFTERNOON, BUT THIS SHOULD HOLD OFF TILL EVENING. 850/925 MB TEMPERATURES STILL WOULD TRANSLATE TO A FAIR SHOT AT 90 FOR KPHL. HOWEVER BASED ON THE POTENTIAL FOR SOME DEBRIS CLOUDS WILL STAY AT OR JUST UNDER THE MET/MAV GUIDANCE SETS ON HIGH TEMPERATURES WHICH IS BACK IN THE MID 80`S FOR MANY. IN TERMS OF STRONG TO SEVERE STORMS THE LATEST SPC OUTLOOKS MAINTAIN A SLIGHT RISK FOR SEVERE STORMS FROM SUNDAY INTO MONDAY WITH THE SOUTHERN PART OF THE REGION HAVING THE HIGHEST CHANCE EVEN FOR SIGNIFICANT SEVERE. THERE IS QUITE A SPREAD IN TERMS OF DESTABILIZATION WITHIN THE SPC SREF PLUMES, FROM 700-3000 J/KG CAPE AT PHL FOR 21Z ON SUNDAY. HOWEVER EFFECTIVE BULK SHEAR OF 30-50 KNOTS IS WELL ESTABLISHED WITH THE OPERATIONAL MODELS AND THE SREF. IN MODEL SOLUTIONS WHERE DESTABILIZATION OCCURS, LAPSE RATES STEEPEN ENOUGH WITH THE CORRESPONDING SHEAR TO SUGGEST A HAIL THREAT AND THE POTENTIAL FOR GUSTY DOWNDRAFT WINDS. PW VALUES WILL BE CLOSE TO 2 INCHES SUGGESTING THE POTENTIAL FOR LOCALLY HEAVY DOWNPOURS AS WELL. ENHANCED WORDING HAS BEEN ADDED TO THE GRIDS AFTER 18Z. USED ELEMENTS FROM THE WPC QPF AND THE 21Z SREF FOR QPF. STAYED WITH LOW LIKELY POPS GIVEN SOME UNCERTAINTY STILL PRESENT IN THE EXACT EVOLUTION WITH THE THUNDERSTORM CLUSTERS. SUNDAY NIGHT: THE HIGHEST CHANCE FOR PRECIPITATION IN WILL BE SUNDAY NIGHT IN ASSOCIATION WITH THE STRONGEST VORT MAX AND ASSOCIATED SHORTWAVE WHICH HAS LIKELY ALREADY LEAD TO THE DEVELOPMENT OF ANOTHER MCS TO OUR WEST. THIS MCS IS LIKELY TO MOVE EAST DURING THE NIGHT. SIMILAR CONDITIONS TO EARLIER IN THE DAY WITH SOME UNCERTAINTY IN THE AMOUNT OF INSTABILITY (CLOUD COVER/ PREVIOUS STORMS) WITH MODEST SHEAR LEADING TO A CONTINUED RISK OF GUSTY WINDS AND HAIL WITH THUNDERSTORMS. ENHANCED WORDING AS WELL IN THIS PERIOD. CONTINUED LOW END LIKELY POPS SUNDAY NIGHT GIVEN THE UNCERTAINTY IN THE LOCATION OF THE MCS`S. 00Z HIRES NAM IMPLIES MAIN DEVELOPMENT TO OUR SOUTH IN THIS PERIOD WHICH ADDED HESITATION TO INCREASING POPS. FOR QPF USED BOTH THE WPC QPF AND THE 21Z SREF. STAYED CLOSE TO THE MET AND MAV GUIDANCE SETS FOR TEMPERATURES. MONDAY AND MONDAY NIGHT: THE COLD FRONT MOVES THROUGH LIKELY MONDAY AFTERNOON. THE MAJORITY OF SHOWERS AND STORMS SHOULD BE EAST OF THE REGION. HOWEVER SOME SHOWERS/THUNDER MAY LINGER WITH THE VORT MAX AND TROUGH AXIS MOVING THROUGH THE REGION. HIGHEST SHOWER CHANCES ACROSS THE NORTH. A GUSTY DAY IS LIKELY AS MODELED MOMENTUM TRANSFER CONTINUES TO SHOW THE POTENTIAL FOR SOME GUSTS NEAR 20 MPH. 850/925 MB TEMPS ARE A BIT COOLER WITH RECENT MODEL RUNS WHEN COMPARED TO THE PAST FEW DAYS ALSO MORNING CLOUDS MAY BE ISSUE AS WELL WITH AFTERNOON HIGHS. KNOCKED AFTERNOON HIGHS DOWN A TOUCH FROM PREVIOUS FORECAST WHICH MATCHES UP WELL WITH THE MET AND MAV. TUESDAY THROUGH FRIDAY: ANOTHER CANADIAN AIRMASS COMES DOWN INTO THE REGION WITH HIGH PRESSURE IN CONTROL THROUGH THURSDAY. THE HIGH PRESSURE MOVES EAST OF THE REGION BY FRIDAY ALLOWING FOR SOME MODERATION BACK TO NORMAL. COOL NORTHWESTERLY FLOW WILL BE IN PLACE TUESDAY AND WEDNESDAY AS MOST LOCATIONS STRUGGLE TO 80 FOR HIGHS. 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 PARTICULARLY THE MEX, CLOSE TO WPC IN MOST PERIODS. LAPSE RATES MAY STEEPEN UP TUESDAY AFTERNOON FOR THE FORMATION OF SOME CUMULUS/ISOLATED LIGHT SHOWER ON THE BACKSIDE OF THE TROUGH ACROSS THE NORTH WITH THE AID OF ELEVATION. MAINTAINED SLIGHT POP ON TUESDAY FROM PREVIOUS FORECAST. OTHERWISE, EACH DAY LOOKS MOSTLY SUNNY. DEWPOINT DEPRESSIONS LOOK TO LARGE FOR WEDNESDAY AND THURSDAY FOR MUCH IN THE WAY OF AFTERNOON CUMULUS. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. OVERALL, VFR CONDS ARE EXPECTED. HIGH PRES WILL MOVE EWD. A WMFNT WILL MOVE THRU LATE AND A CDFNT WILL APPROACH FROM THE W. THERE WILL BE LOW POP CHCS TODAY AND TONIGHT. ANY SHWRS OR TSRA CUD BRING LWR CIGS/VSBYS BUT CHCS ARE LOW ENOUGH AT THIS TIME NOT TO MENTION IN THE INDIVIDUAL TAF SITES AND THERE ARE ENOUGH DIFFS IN THE MDL GUID TO LWR CONFIDENCE EVEN MORE. WIND WILL GENLY BE SWLY THRU THE PD. THE WIND CUD GUST AS HIGH AS 20 KT DURG THE DAY TODAY, BUT WILL BE LESS THAN 10 KT OTHERWISE. OUTLOOK... SUNDAY AND SUNDAY NIGHT: MVFR AND IFR RESTRICTIONS IN THUNDERSTORMS. SOME GUSTY WINDS POSSIBLE AS WELL FROM THE THUNDERSTORMS. MONDAY: GRADUALLY TURNING VFR. SOME SOUTHWEST/WEST WIND GUSTS AROUND 20 KNOTS POSSIBLE MONDAY AFTERNOON. WIND SHIFTING FROM SOUTHWEST TO WEST IN THE AFTERNOON. MONDAY NIGHT THROUGH WEDNESDAY: VFR. && .MARINE... HIGH PRES WILL MOVE EWD TODAY. SWLY FLOW WILL GRADUALLY INCREASE OVER THE WATERS THRU TONIGHT AND SEAS WILL SLOWLY BUILD AS WELL. HOWEVER, BOTH WIND AND WAVES ARE EXPECTED TO REMAIN BELOW SCA CRITERIA THRU THE NR AND SHORT TERM PDS AND NO MARINE HEADLINES ARE ANTICIPATED. OUTLOOK... SUNDAY AND MONDAY:FOUR FEET SEAS WILL BE POSSIBLE AT TIMES SUNDAY AND MONDAY. THINK WAVEWATCH MAY BE A TOUCH AGGRESSIVE WITH WAVE HEIGHTS. 20 KNOT WIND GUSTS POSSIBLE AS WELL. MONDAY NIGHT THROUGH WEDNESDAY: SEAS AND WINDS EXPECTED TO BELOW SCA CRITERIA ATTM. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GAINES NEAR TERM...GIGI/NIERENBERG SHORT TERM...NIERENBERG LONG TERM...GAINES AVIATION...GAINES/NIERENBERG MARINE...GAINES/NIERENBERG

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