Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KPHI 031323 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 923 AM EDT FRI JUL 3 2015 .SYNOPSIS... A WEAK HIGH PRESSURE SYSTEM WILL BUILD INTO NEW ENGLAND TODAY AND TONIGHT. MEANWHILE, A LOW PRESSURE SYSTEM OVER THE LOWER OHIO VALLEY WILL RIDE ALONG THE STALLED FRONTAL BOUNDARY AND PASS EAST OF THE DELMARVA PENINSULA ON INDEPENDENCE DAY. ANOTHER AREA OF HIGH PRESSURE WILL THEN MOVE INTO THE REGION FOR THE END OF THE HOLIDAY WEEKEND AND MONDAY. A WEAK LOW PRESSURE SYSTEM MIGHT EASE NORTH INTO THE AREA ON TUESDAY AS ANOTHER COLD FRONT APPROACHES THE FORECAST AREA BY WEDNESDAY NIGHT. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
FOG HAS MOSTLY DISSIPATED ACROSS THE AREA. A TRANSIENT SURFACE HIGH WILL SLIDE OVER THE REGION TODAY BRINGING A FAIRLY NICE DAY FOR MOST AREAS. THERE ARE NO STRONG SHORT WAVE/VORTICITY IMPULSES FORECAST TO MOVE ACROSS THE AREA AND THERE IS NOT ANY INSTABILITY FORECAST AS A STRONG CAP WILL BE IN PLACE. SO WE DO NOT EXPECT ANY PRECIPITATION TO DEVELOP THROUGH THE DAYTIME PERIOD FOR MOST OF THE AREA. THE ONLY EXCEPTION WOULD BE ACROSS SOUTHERN NEW JERSEY AND DELMARVA WHERE THERE IS SOME WEAK CHANNELIZED VORTICITY, WHICH COULD CREATE A FEW ISOLATED SHOWERS. OTHERWISE, MAINLY AN INCREASE IN CLOUD COVER IS EXPECTED TODAY. HIGHS ARE A BLEND OF MAV/MET MOS, MOSGUIDE, AND BLENDED 925 MB ECMWF TEMPERATURES.
-- End Changed Discussion --
&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/... AN AREA OF LOW PRESSURE WILL BE DEVELOPING TO OUR WEST THIS EVENING ALONG THE STALLED OUT FRONTAL BOUNDARY THAT IS LOCATED TO OUR SOUTH AND SOUTHWEST. THIS LOW WILL TRACK EASTWARD THROUGH THE NIGHT ALONG THE FRONTAL BOUNDARY AND APPROACH OUR SOUTHERN AREAS TOWARD DAYBREAK SATURDAY. A COUPLE OF SHORT WAVE/VORTICITY IMPULSES WILL BE MOVING ACROSS THE AREA OVERNIGHT AS WELL. THIS WILL LEAD TO INCREASING SHOWER POSSIBILITIES OVERNIGHT INTO DAYBREAK SATURDAY. THERE IS NOT MUCH, IF ANY INSTABILITY FORECAST FOR MOST AREAS EXCEPT OUR FAR SOUTHERN AREAS. SO WE ONLY KEEP ISOLATED THUNDERSTORMS FOR EXTREME SOUTHERN NEW JERSEY AND DELMARVA. LOWS ARE A BLEND OF MAV/MET MOS AND MOSGUIDE. && .LONG TERM /SATURDAY THROUGH THURSDAY/... THE GFS INITIALIZATION LOOKED MUCH BETTER THAN THE WRF-NMMB WITH THE 500MB TROF IN THE MIDWEST AND ALSO BETTER THAN THE WRF-NMMB AT 850MB. ONCE WE GET DOWN TO 925MB, THE WRF-NMMB LOOKS BETTER. THE IMPLICATION OF THE 500MB DIFFERENCES (ESP IN THE UPPER MIDWEST) IS THAT THE WRF-NMM HAS A SLIGHTLY MORE SHEARED WEAKER SOLUTION FOR INDEPENDENCE DAY. THE LATEST GFS IS VERY CLOSE TO THE PREVIOUS TWO ECMWF RUNS AND NOW HAS THE HEAVIEST RAIN FLIPPED TO THE OPPOSITE END OF OUR CWA FROM LAST NIGHT. A DP/DT VALID 18Z SATURDAY SHOWS THIS TRANSITION WHICH STARTED WITH 06Z RUN LAST NIGHT. WITH THE TROF DEEPER AND HANGING BACK, THE NEXT WAVE ON THE FRONT BECOMES MUCH MORE MUTED AND THE LAST LOW ON THE WAVE TRAIN BECOMES THE ALPHA LOW. AND THERE GOES INDEPENDENCE DAY. LAST NIGHT IT APPEARED THE EURO WAS TOO SLOW WITH WAVE NUMBER TWO, BUT IN REALITY AND UNFORTUNATELY ITS LOOKING LIKE IT WILL BE RIGHT FOR THE WRONG REASON AS ITS WAVE NUMBER THREE THAT SHOULD MAKE IT THREE CONSECUTIVE WET SATURDAYS IN A ROW. THE WAA INDUCED PHASE OF THE SYSTEM SHOULD BE UNDERWAY OR ON THE VERGE OF GETTING UNDERWAY IN THE WESTERN PART OF OUR CWA AS INDEPENDENCE DAY STARTS. WE SEE DECENT MID LEVEL QVEC CONVERGENCE PLUS A WELL POSITIONED 250MB ENTRANCE REGION OF THE JET FOR THE COOL SECTOR PCPN MAX. THE RAW QPF MAY BE OVERDONE THERE BECAUSE OF THE LACK OF PREDICTED CONVECTION, THERE SHOULD BE A SECONDARY MAX IN THAT PART OF THE CYCLONE. WHILE THE ECMWF HAS BEEN STEADIER, THERE ARE STILL SOME LATITUDINAL DIFFERENCES TO THE EXTENT OF CONVECTION IN OUR CWA. THE GFS IS ON THE NORTHERN ENVELOPE. THE GEFS MEAN DOES A NORTH-SOUTH-NORTH MEANDERING AROUND THE OP SFC LOW POSITION. WE SPREAD CONVECTIVE CHANCES NORTHWARD AS SATURDAY PROGRESSES, BUT THE BEST CHANCE REMAINS FROM THE MASON-DIXON AND ACY EXPRESSWAY LINE SOUTHWARD. THIS SHOULD BE A SECONDARY 9AND POSSIBLY HIGHEST) PRECIP MAX. GFS PCPN WATER VALUES EXCEED TWO INCHES YET AGAIN. AS FAR AS SEVERE GOES, PREDICTED 500MB TEMPS ARE RATHER WARM, A FEW DEGREES WARMER THAN 6/30. THUS MID LEVEL LAPSE RATES ARE POOR. DCAPE IS NOT STRONG. WE WILL HAVE MORE THAN ADEQUATE BULK SHEAR, BUT MIXED LAYER CAPES ARE PREDICTED TO REMAIN LESS THAN 1K JOULES EXCEPT FOR POSSIBLY DELMARVA. SO IF THERE IS A WINDOW FOR STRONGER STORMS, ITS FAR SOUTH AS OF NOW. THE EARLY START TO CLOUDS AND PCPN IS NOT GOING TO HELP. THE WAA PUSH GETS THROUGH DURING THE AFTERNOON, SO IF THERE IS A SILVER LINING, THE CURRENT TIMING (PMDHMD SUGGESTS A NON-CMC BLEND) WOULD END THE HIGHEST PCPN CHANCES TOWARD EVENING. NOT CONFIDENT ABOUT MAX TEMPS AT BOTH ENDS OF OUR CWA: NORTHWEST CLOUDS/PCPN MAY MAKE US TOO HIGH, SOUTHEAST, A WARM SECTOR SQUEEZE WE MAY BE TOO LOW. FULL SUN SUPPORTIVE OF NEAR 90. IF WE CAN BANK ON CURRENT TIMING, SHWRS AND TSTMS WOULD BE DONE BY THE START OF ANY FIREWORK FESTIVITIES SATURDAY EVENING. GIVEN THE TIMING SLIPPAGE FROM LAST NIGHT, WE CARRIED A LOW CHANCE EARLY. SUNDAY CONTINUES TO BE THE BETTER WEEKEND DAY. A DRY FORECAST WITH TEMPERATURES RECOVERING TO NEAR NORMAL AND RELATIVELY LOW HUMIDITY LEVELS. FORECAST SOUNDINGS DO SHOW SOME CAPE, BUT HAVE THE CAP HOLDING. ITS THE TYPE OF DAY IN WHICH VERY ISOLATED CONVECTION WOULD AFFECT LESS THAN 10% OF OUR CWA. THE TRANSITION TO A WARMER AND MORE HUMID WEEK THEN STARTS ON MONDAY. THIS MIGHT BE TEMPERED SLIGHTLY ON MONDAY AND TUESDAY AS YET ANOTHER WEAK LOW PRESSURE ON OUR OLD FRONTAL BOUNDARY IS PREDICTED TO FORM AND DRIFT SLOWLY NORTH. POPS ARE GRADUALLY INCREASED FROM SOUTH TO NORTH MONDAY INTO TUESDAY. NO BIG CHANGES TO WED AND THU FORECASTS. A SLOW MOVING COLD FRONT SHOULD BE NEAR ENOUGH TO TRIGGER MORE THUNDERSTORMS ON WEDNESDAY AND THURSDAY. THE USUAL MODEL TIMING DIFFERENCES ARE THERE WITH THE GFS FASTER THAN THE ECMWF. NORMALLY SLOWER IS BETTER IN SUMMER (UNFORTUNATELY FOR SATURDAY), SO WE KEPT RELATIVELY HIGH POPS IN FOR BOTH DAYS. && .AVIATION /13Z FRIDAY THROUGH TUESDAY/...
-- Changed Discussion --
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS WITH LIGHT WINDS (GENERALLY NEAR OR BELOW 5 KT) WILL CONTINUE THROUGH AT LEAST 00Z. RAIN MAY START MOVING INTO THE AREA AS EARLY AS 03Z, BUT MORE LIKELY AFTER 06Z. ONCE THE RAIN BEGINS, CONDITIONS MAY LOWER TO MVFR OR LOWER. WIND DIRECTION WILL ONCE AGAIN BE A BIT VARIABLE TODAY INTO TONIGHT, SHIFTING FROM MOSTLY NORTHERLY DIRECTION NOW TO A SOUTHEASTERLY DIRECTION AROUND OR AFTER 00Z. OUTLOOK... SATURDAY...PREDOMINATELY MVFR, WITH IFR CONDITIONS AT TIMES DURING HEAVIER SHOWERS AND TSTMS. SATURDAY NIGHT...SOME MVFR CONDITIONS POSSIBLE IN FOG, ESPECIALLY AT MORE RURAL AIRPORTS. SUNDAY AND SUNDAY NIGHT...VFR. MONDAY AND TUESDAY...PREDOMINATELY VFR, BUT DECREASING TO MVFR/IFR GOING FORWARD INTO TUESDAY AS MORE SHOWERS AND TSTMS DEVELOP.
-- End Changed Discussion --
&& .MARINE... SUB-SMALL CRAFT ADVISORY CONDITIONS WILL REMAIN ACROSS THE AREA TODAY INTO TONIGHT, ALTHOUGH WINDS MAY BEGIN INCREASING AND GUSTING AROUND 20 KNOTS OVERNIGHT FRIDAY INTO EARLY SATURDAY MORNING AS LOW PRESSURE APPROACHES FROM THE WEST. OUTLOOK... SATURDAY AND SATURDAY NIGHT...DEPENDING ON THE STRENGTH AND TRACK OF THE LOW PRESSURE SYSTEM ALONG THE STALLED FRONT, A SCA MAY BE NEEDED, ESPECIALLY ON THE NORTHERN OCEAN WATERS STARTING SATURDAY AFTERNOON. WHILE WINDS SHOULD DECREASE SATURDAY NIGHT, SEAS MIGHT STILL REACH SMALL CRAFT ADVISORY CRITERIA. SUNDAY THRU TUESDAY...OUTSIDE OF ANY SPECIAL MARINE WARNINGS...NO SYNOPTIC SCALE INDUCED MARINE FLAGS ANTICIPATED. && .TIDES/COASTAL FLOODING... DUE TO THE RECENT FULL MOON AND A STEADY EASTERLY FLOW TODAY INTO TONIGHT, TIDES WILL CONTINUE RUNNING HIGH. THE HIGH TIDE LATER TONIGHT INTO EARLY SATURDAY MORNING MAY APPROACH THE MINOR FLOOD LEVEL, BUT RIGHT NOW NO SITES ARE FORECAST TO REACH LEVELS NEEDED FOR A COASTAL FLOOD ADVISORY. THE TWO SITES THAT MAY GET THE CLOSEST WOULD BE REEDY POINT AND PHILADELPHIA. WE`LL CONTINUE TO MONITOR THROUGH THE DAY TO SEE IF AN ADVISORY IS NEEDED. THEN ON SATURDAY NIGHT, THE TIDAL CONCERN SWITCHES TO THE OCEANSIDE AS A LINGERING NORTHEAST FLOW SHOULD BRING ACTUAL TIDES CLOSE TO MINOR TIDAL FLOODING LEVELS. THE HIGHEST CONCERN IS ALONG THE NJ COAST TOWARD NEW YORK CITY. && .RIP CURRENTS...
-- Changed Discussion --
THE COMBINATION OF AN ONSHORE FLOW AND THE FULL MOON IS EXPECTED TO INCREASE THE STRENGTH OF RIP CURRENTS SATURDAY, BEFORE CONDITIONS IMPROVE ON SUNDAY. LOCAL REGRESSION GUIDANCE SHOWS THE RIP CURRENT RISK FOR THE NJ AND DE BEACHES TO BE JUST BELOW MODERATE FOR TODAY, WITH A GREATER LIKELIHOOD FOR A MODERATE RISK ON SATURDAY (WHICH MAY NOT BE A GREAT BEACH DAY BECAUSE OF NUMEROUS SHOWERS).
-- End Changed Discussion --
&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GIGI/NIERENBERG NEAR TERM...JOHNSON/ROBERTSON SHORT TERM...ROBERTSON LONG TERM...GIGI AVIATION...GIGI/JOHNSON/ROBERTSON MARINE...GIGI/NIERENBERG/ROBERTSON TIDES/COASTAL FLOODING... RIP CURRENTS...

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.