Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 020136 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 936 PM EDT SUN MAY 1 2016 .SYNOPSIS... A WARM FRONT WILL SLOWLY LIFT NORTHWARD TOWARD THE AREA TONIGHT, THEN ACROSS THE AREA DURING THE DAY MONDAY AS AN AREA OF LOW PRESSURE SLIDES ACROSS THE NEW ENGLAND STATES. A COLD FRONT WILL SAG INTO OUR AREA MONDAY, WHILE AN AREA OF LOW PRESSURE MOVES ALONG THE BOUNDARY AND APPROACHES OUR AREA FROM WEST LATE IN THE DAY INTO THE EVENING. THE FRONT WILL SLOWLY DRIFT OFFSHORE THROUGH TUESDAY, WITH SEVERAL AREAS OF LOW PRESSURE MOVING ALONG THE BOUNDARY TUESDAY AND TUESDAY NIGHT. HIGH PRESSURE WILL RIDGE ACROSS THE AREA FROM THE NORTH WEDNESDAY. MORE LOW PRESSURE WILL STRENGTHEN AND AFFECT OUR WEATHER FROM THURSDAY INTO THE UPCOMING WEEKEND. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... A WARM FRONT LOCATED TO OUR SOUTH IS FORECAST TO SLOWLY LIFT NORTHWARD TOWARD THE AREA OVERNIGHT TONIGHT. MEANWHILE, AN AREA OF LOW PRESSURE IS FORECAST TO WORK ITS WAY UP THE OHIO RIVER VALLEY TONIGHT. ANOTHER WEAK AREA OF LOW PRESSURE IS EXPECTED TO DEVELOP OFF OUR COAST ALONG THE WARM FRONTAL BOUNDARY AND LIFT TO OUR NORTHEAST. AS A RESULT, THE SURFACE WIND IS ANTICIPATED REMAIN OUT OF THE EAST TO THE NORTHEAST ON THE COASTAL PLAIN AND ON MOST OF OUR MARINE AREA. THE WIND SHOULD BECOME LIGHT AND VARIABLE FARTHER INLAND, BUT ANY DIRECTION WILL LIKELY BE EAST TO NORTHEAST. THE ONSHORE FLOW NORTH OF THE WARM FRONT WILL HOLD LOW LEVEL MOISTURE IN OUR REGION THROUGH THE NIGHT WHICH WILL KEEP PATCHY FOG AND DRIZZLE ACROSS THE AREA. WEAK VORTICITY IMPULSES TRAVELING IN THE WEST SOUTHWEST MID LEVEL FLOW MAY ACT TO TOUCH OFF SCATTERED TO ISOLATED SHOWERS. THERE IS THUNDERSTORM ACTIVITY TO OUR WEST, BUT AS THESE RIDE OVER THE FRONTAL BOUNDARY TO OUR SOUTH AND WEST, THEY SHOULD LOSE STEAM, SO NO THUNDERSTORMS ARE EXPECTED ACROSS THE AREA OVERNIGHT. THE CLOUD COVER IS FORECAST TO KEEP TEMPERATURES FROM DROPPING MUCH OVERNIGHT. LOWS SHOULD BE MOSTLY IN THE 40S IN THE NORTH AND IN THE 50S IN THE SOUTH. && .SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/... THE LOW LEVEL MOISTURE WILL REMAIN IN OUR REGION INTO MONDAY MORNING. AS A RESULT, THE DAY SHOULD BEGIN OVERCAST WITH PATCHY DRIZZLE AND FOG ALONG WITH A CHANCE OF SHOWERS. THE MARINE LAYER IS EXPECTED TO ERODE GRADUALLY FROM THE SOUTH THROUGH THE DAY AS THE WARM FRONT LIFTS NORTHWARD. HOWEVER, THE IMPROVEMENT MAY NOT REACH PARTS OF NORTHERN NEW JERSEY AND OUR ADJACENT COUNTIES IN EASTERN PENNSYLVANIA BY DAY`S END. DUE TO THE VARYING AMOUNTS OF CLOUD COVER, WE ARE ANTICIPATING A WIDE SPREAD IN MAXIMUM TEMPERATURES. HIGHS MAY NOT GET OUT OF THE 50S IN THE FAR NORTH AND PERHAPS ALONG THE NORTHERN PART OF THE JERSEY SHORE. MEANWHILE, MAXIMUM TEMPERATURES ARE FORECAST TO APPROACH 80 IN OUR FAR SOUTHERN COUNTIES. THE WIND SHOULD BEGIN THE DAY FROM THE NORTHEAST AND EAST AROUND 4 TO 8 MPH. THE DIRECTION IS EXPECTED TO VEER TOWARD THE SOUTHEAST AND SOUTH AS THE MARINE LAYER ERODES. MADE SOME UPDATES TO THE FORECAST WITH THE EVENING UPDATE TO INCREASE THUNDERSTORMS CHANCES ACROSS FAR SOUTHEASTERN PA, SOUTHERN NJ AND ESPECIALLY OUR DELMARVA ZONES. THE LATEST 12Z/18Z GUIDANCE STILL SHOWS SOME DIFFERENCES REGARDING HOW FAR NORTH INTO OUR AREA THE WARM FRONT ADVANCES BUT SOLUTIONS ARE CONVERGING TOWARD THE WARM FRONT BEING IN CLOSE PROXIMITY TO THE PHILA METRO BY LATE AFTERNOON. CONVECTION MAY BE SLOW TO DEVELOP DUE TO A LACK OF ORGANIZED/DEEP LIFT INITIALLY ON MONDAY AFTERNOON. HOWEVER, LIFT SUBSEQUENTLY INCREASES LATE IN THE AFTERNOON AND ESPECIALLY MONDAY NIGHT AS A WAVE OF LOW PRESSURE ALONG THE FRONTAL BOUNDARY DEEPENING OVER THE DC AREA, LOW-LEVEL CONVERGENCE INCREASES NEAR THE WARM FRONT BOUNDARY. ADDITIONALLY, FORCING FOR ASCENT IS FORECAST TO DEEPEN LATER MONDAY NIGHT IN RIGHT-ENTRANCE REGION OF AN UPPER-LEVEL JET STREAK TO OUR NORTHWEST AND AHEAD OF AN APPROACHING MID-LEVEL SHORTWAVE TROUGH. THERE IS ALSO GROWING CONCERN FOR STRONG TO SEVERE THUNDERSTORMS POTENTIALLY DEVELOPING ALONG AND SOUTH OF THE WARM FRONT DURING THE LATE AFTERNOON AND EVENING. FORECAST CONVECTIVE INDICES FROM THE 18Z NAM WAS PARTICULARLY OMINOUS WITH 2000-3000 J/KG OF SBCAPE AND 45-55 KT OF DEEP-LAYER BULK SHEAR PRESENT IN THE WARM SECTOR FROM ABOUT ILG TO ACY SOUTHWARD AT 21Z MON AND 00Z TUE. LAST NIGHT`S 00Z RUN OF THE HI-RES NCAR ENSEMBLES ALSO INDICATE A SIMILAR FAVORABLE ENVIRONMENT FOR CONVECTION IN THE WARM SECTOR ALTHOUGH MEAN FORECAST INDICES ARE NOT QUITE AS EXTREME AS THE 18Z NAM (NOT SURPRISING SINCE AN ENSEMBLE MEAN BLENDS OUT THE EXTREMES). NONETHELESS, THE FORECAST ENVIRONMENT INDICATES A POTENTIAL FOR DAMAGING WINDS/WET MICROBURSTS AND LARGE HAIL ACROSS OUR SOUTHERN ZONES. WILL ADD THE SEVERE RISK IN THE HWO. FURTHER COORDINATE WITH SPC MAY BE NEEDED. WE ALSO MAY TRANSITION TO A HEAVY RAINFALL EVENT MONDAY NIGHT SOMEWHERE IN THE SOUTHERN TIER OF THE CWA NEAR THE WARM FRONT. MORE DETAILS WILL BE PROVIDED IN UPCOMING FORECAST DISCUSSIONS IF NECESSARY. && .LONG TERM /TUESDAY THROUGH SUNDAY/... LITTLE CHANGE FROM THE PREVIOUS FORECAST IN THIS TIME PERIOD. UNSETTLED WEATHER FOR MUCH OF THIS TIME FRAME WITH TEMPERATURES RUNNING SEVERAL DEGREES COOLER THAN NORMAL. CONSIDERABLE UNCERTAINTY WITH THE SURFACE PATTERN DETAILS LATER THIS WEEK AS THE DEEP UPPER TROUGH SETTLES IN OVER THE REGION. BEST CHANCES FOR PRECIPITATION ARE IN THE MONDAY NIGHT/TUESDAY TIMEFRAME AND THEN AGAIN THURSDAY/FRIDAY. NEXT SUNDAY IS CURRENTLY THE DRIEST DAY IN THIS FORECAST PERIOD. PRIMARILY USED 12Z SUPERBLEND IN THIS TIME PERIOD. BUT 12Z SUPERBLEND STRUGGLED WITH THE WINDS FOR MUCH OF THIS TIME PERIOD. 00Z NATIONAL BLEND PROVIDED BETTER CONTINUITY FOR WINDS WITH OUR PREVIOUS FORECAST AND WITH ADJACENT OFFICES SO THAT WAS USED. ALSO USED WPC GUIDANCE IN LIEU OF SUPERBLEND FOR DAY 7 TO REFLECT LATEST FORECAST THINKING. && .AVIATION /00Z MONDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY, AND SURROUNDING AREAS. IFR CONDITIONS ARE FORECAST TO PREVAIL THROUGH TONIGHT AND INTO MONDAY MORNING AT OUR TAF SITES. THERE IS A CHANCE OF SHOWERS. ALSO, PATCHY FOG AND DRIZZLE ARE POSSIBLE OVERNIGHT INTO EARLY MONDAY MORNING. THE WIND IS EXPECTED TO FAVOR THE EAST AND NORTHEAST AROUND 4 TO 8 KNOTS. GRADUAL IMPROVEMENT IS EXPECTED FROM THE SOUTH FROM LATE MONDAY MORNING INTO MONDAY AFTERNOON. HOWEVER, THE SPEED AND EXTENT OF THE IMPROVEMENT REMAINS A LOW CONFIDENCE FORECAST AT THIS TIME. WE HAVE KEPT THE TAFS PESSIMISTIC BASED ON THE UNCERTAINTY IN THIS TYPE OF WEATHER PATTERN. THE WIND DIRECTION SHOULD BEGIN TO VEER TOWARD THE SOUTHEAST AND SOUTH ON MONDAY AFTERNOON, ESPECIALLY AT KACY, KMIV AND KILG. ALSO MONDAY AFTERNOON INTO THE EVENING, AS A COLD FRONT MOVES ACROSS THE AREA AND LOW PRESSURE APPROACHES FROM THE WEST, THERE IS A CHANCE FOR SHOWERS AND POSSIBLE THUNDERSTORMS TO INCREASE ACROSS THE SOUTHERN PORTIONS OF THE AREA. WE CURRENTLY ONLY HAVE SHOWERS IN THE TAFS, BUT THUNDERSTORMS MAY BE NEED TO BE INCLUDED IN THE FUTURE. OUTLOOK... MON NIGHT THRU TUE NIGHT...SHOWERY CONDITIONS WITH LOWER CIGS/VSBYS AT TIMES. WED...MOSTLY VFR. WED NIGHT THRU FRI...MORE SHOWERY CONDITIONS WITH LOWER CONDITIONS POSSIBLE. && .MARINE... THE ONSHORE FLOW IS EXPECTED TO CONTINUE TONIGHT INTO MONDAY MORNING WITH WEAK LOW PRESSURE DEVELOPING OFF OUR COAST. WE ANTICIPATE THAT WAVE HEIGHTS ON OUR OCEAN WATERS WILL BUILD TO AROUND 5 FEET AND WE WILL CONTINUE TO CARRY A SMALL CRAFT ADVISORY FOR SEAS. WE WILL ADJUST THE TIME OF THE ADVISORY, STARTING IT AT 800 PM THIS EVENING AND ENDING IT AT 400 PM MONDAY BASED ON THE LATEST GUIDANCE. WIND SPEEDS ARE FORECAST TO REMAIN BELOW 20 KNOTS WITH THE DIRECTION FAVORING THE NORTHEAST AND EAST TONIGHT AND MONDAY MORNING, AND THE SOUTHEAST AND SOUTH ON MONDAY AFTERNOON. OUTLOOK... MONDAY NIGHT THRU FRIDAY NIGHT...MOSTLY SUB SCA CONDITIONS. SCT SHOWERS THRU MUCH OF THE TIME. LOW END SCA SEAS POSSIBLE FRIDAY INTO FRIDAY NIGHT. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM EDT MONDAY FOR ANZ450>455. && $$ SYNOPSIS...SZATKOWSKI/ROBERTSON NEAR TERM...IOVINO/ROBERTSON SHORT TERM...IOVINO/KLEIN LONG TERM...SZATKOWSKI AVIATION...SZATKOWSKI/IOVINO/ROBERTSON MARINE...SZATKOWSKI/IOVINO

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