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. --
206 FXUS61 KPHI 020735 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 335 AM EDT MON MAY 2 2016 .SYNOPSIS... LOW PRESSURE AND ITS ASSOCIATED FRONTS WILL AFFECT OUR AREA TODAY AND TONIGHT. ANOTHER LOW PRESSURE SYSTEM WILL SLIDE UP ACROSS THE DELMARVA ON TUESDAY AND THEN OFFSHORE TUESDAY NIGHT. WEAK HIGH PRESSURE WILL RIDGE ACROSS THE AREA WEDNESDAY BEFORE ANOTHER LOW PRESSURE SYSTEM ARRIVES FROM THE GREAT LAKES. THIS LOW WILL MEANDER ACROSS THE AREA THROUGH THE END OF THE WEEK AND INTO THE EARLY PART OF THE UPCOMING WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A FRONTAL BOUNDARY STILL DRAPED TO OUR SOUTH ALONG WITH HIGH PRESSURE TO OUR NORTHEAST IS KEEPING A RATHER MOIST ONSHORE FLOW ACROSS OUR AREA. THIS IS RESULTING IN SOME FOG AND DRIZZLE. IT APPEARS THAT ANY DENSE FOG IS MAINLY CONFINED TO THE HIGHER TERRAIN GIVEN HOW LOW THE CEILINGS ARE EARLY THIS MORNING. SOME SUBTLE SHORT WAVES WITHIN THE SOUTHWESTERLY FLOW ALOFT IS HELPING TO GENERATE SOME SHOWERS, WITH ONE OF THESE MORE NOTABLE FEATURES MOVING THROUGH EARLY THIS MORNING. THIS SHOULD KEEP SOME SHOWERS AROUND THE AREA BEFORE A LULL TAKES PLACE. THE FORECAST THEREAFTER IS RATHER COMPLICATED WITH LESS CERTAINTY GIVEN IT HINGES ON WHERE THE WARM FRONT MOVES TO BY LATE THIS AFTERNOON. WE ARE EXPECTING MUCH WARMER AIR TO MOVE INTO AT LEAST OUR DELMARVA ZONES, HOWEVER THE EXTENT OF EROSION OF THE LOW CLOUDS IS NOT ALL THAT CLEAR. AN EXAMINATION OF THE MODEL GUIDANCE SUGGESTS THE WARM FRONT MAY GET INTO THE PHILADELPHIA METRO AREA, WITH THE MAIN WARM SECTOR HANGING BACK FARTHER TO THE SOUTH. THE FLOW IN THE LOWEST LEVELS IS NOT FORECAST TO BE ALL THAT STRONG AS AN INCOMING SURFACE LOW IS ON THE WEAKER SIDE. AS A RESULT, WE ARE NOT RUSHING IN THE CLEARING FROM SOUTH TO NORTH. THIS WILL HAVE AN IMPACT ON DESTABILIZATION THROUGH THE AFTERNOON, AT WHICH THE BULK OF IT IS ACROSS PORTIONS OF MARYLAND AND DELAWARE TO PERHAPS FAR SOUTHERN NEW JERSEY. AGAIN, THIS WILL ULTIMATELY DEPEND ON THE POSITIONING OF THE INCOMING WARM FRONT. THIS WILL ALSO DETERMINE THE EXTENT OF CONVECTIVE CHCS AS ANOTHER SHORT WAVE ARRIVES TOWARD EVENING ALONG WITH THE INCOMING WEAK SURFACE LOW. THE FORCING FOR ASCENT SHOULD INCREASE WITH THESE FEATURES WITH AN INCREASE IN SHOWERS AND PERHAPS THUNDERSTORMS. WE CONTINUED TO CONFINE THE THUNDER CHCS ACROSS THE SOUTHERN PORTIONS OF OUR CWA, HOWEVER DID NOT ADD IN ENHANCED WORDING YET GIVEN LESS CONFIDENCE WITH THE AMOUNT OF CLEARING AND THEREFORE INSTABILITY. IF HIGHER INSTABILITY DEVELOPS, SOME STORMS COULD PRODUCE LOCALLY STRONG WINDS WITH THE FORECAST SOUNDINGS INDICATING THE POTENTIAL FOR SOME WET MICROBURSTS. THE LOW-LEVEL FLOW WILL BE BACKED SOME NEAR THE WARM FRONT WHICH WILL NEED TO BE MONITORED IF CONVECTIVE CELLS INTERACT WITH IT. OVERALL, THE POTENTIAL IS THERE FOR SOME GUSTY THUNDERSTORMS ALONG WITH SOME HAIL HOWEVER THE AMOUNT OF DESTABILIZATION IS IN QUESTION. AS FOR THE HIGH TEMPERATURES, WE USED A MOS BLEND OVERALL ALONG WITH CONTINUITY. THIS CONTINUES TO INDICATE A STRONG GRADIENT FROM SOUTH TO NORTH. THE HOURLY GRIDS EARLY THIS MORNING WERE ADJUSTED BASED ON THE LATEST OBSERVATIONS AND THEN THE LAMP/LAV GUIDANCE WAS BLENDED IN. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... AS A BIT MORE CONSOLIDATED SHORT WAVE ENERGY SLIDES NORTHEASTWARD, SURFACE LOW PRESSURE IS FORECAST TO MOVE ACROSS THE AREA TONIGHT. THIS SHOULD HELP SERVE BETTER FOCUS FOR LIFT AND THEREFORE WE ARE ANTICIPATING THAT SHOWERS EXPAND IN COVERAGE WITH THE POTENTIAL FOR SOME LOCALLY HEAVY DOWNPOURS. A RIBBON OF ENHANCED LIFT MAY BE CLOSE TO THE INTERSTATE 95 CORRIDOR. THE EVENING MAY START CONVECTIVELY ACTIVE ACROSS OUR SOUTHERN ZONES AS CONVECTION THAT DEVELOPS TO OUR SOUTHWEST TRACKS OUR WAY. THIS MAY BE ALONG A LEE SIDE TROUGH AND ALSO NEAR A POTENTIAL HEATING DIFFERENTIAL BOUNDARY IN CLOSE PROXIMITY TO A WARM FRONT. THE CONVECTIVE COVERAGE WILL BE DRIVEN BY THE AMOUNT OF INSTABILITY, HOWEVER EARLY ON THERE COULD BE SOME DISCRETE CELLS BEFORE CONSOLIDATION OCCURS. AS MENTIONED IN THE NEAR TERM SECTION, THE INTENSITY OF THE CONVECTION WILL BE DETERMINED ON THE NORTHWARD EXTENT OF THE WARM SECTOR. GIVEN THE QPF FORECAST AND THE INCOMING SHORT WAVE AND ASSOCIATED LIFT, THE POPS WERE INCREASED INTO THE CATEGORICAL RANGE THROUGH THE NIGHT FOR MUCH OF THE CWA. AS FOR THE LOW TEMPERATURES, WE USED A MOS BLEND OVERALL. A MILDER NIGHT IS ANTICIPATED ESPECIALLY FOR THE CENTRAL AND SOUTHERN ZONES GIVEN AN INCOMING WARM SECTOR. THIS WILL DRIVE DEW POINTS UP AS WELL. GIVEN THE AMOUNT OF SHOWER ACTIVITY ANTICIPATED, ANY SIGNIFICANT FOG SHOULD BE PATCHY DESPITE THE INCREASING DEW POINTS FOR AWHILE. && .LONG TERM /TUESDAY THROUGH SUNDAY/... THE FRONT THAT CROSSES THROUGH THE FORECAST AREA DURING THE SHORT TERM WILL BE SOUTH OF THE REGION TUESDAY MORNING. LOW PRESSURE WILL DEVELOP ALONG THE FRONT OVER NC/VA AND MOVE NORTHEAST OFF THE DE COAST BY TUESDAY NIGHT. THIS WILL RESULT IN MORE RAINY WEATHER FOR TUESDAY. POPS FOR TUE WERE KEPT IN THE HIGH LIKELY/LOW CATEGORICAL RANGE FOR MOST AREAS WITH THE CHC POPS ACROSS THE N/W AREAS..FARTHER AWAY FROM THE RAINY SYSTEM. WEAK RIDGING WILL OCCUR ACROSS THE AREA LATER TUESDAY NIGHT AND INTO WEDNESDAY BEHIND THE DEPARTING LOW. THE BRIEFLY LOWER POPS WILL NOT REMAIN LOW LONG AS THE NEXT SYSTEM APPROACHES FROM THE GREAT LAKES. A BIG PATTERN CHANGE ALREADY TAKING PLACE EARLY THIS WEEK BEGINS TO AFFECT OUR WEATHER LATER WEDNESDAY AS H5 UPPER HEIGHTS FALL RAPIDLY ACROSS THE GREAT LAKES. LOW PRESSURE DEVELOPS WITH THESE HEIGHT FALLS AND CIRCULATES ACROSS OUR AREA FROM WEDNESDAY NIGHT INTO THE EARLY PART OF THE WEEKEND. MUCH OF THE PERIOD WILL HAVE CLOUDS AND SHOWERS. WE HAVE KEPT POPS IN THE CHC RANGE FOR NOW...BUT EXPECT HIGHER POPS WHEN THE DETAILS BECOME MORE CERTAIN LATER TODAY AND TUESDAY. TEMPERATURES WILL REMAIN GENERALLY ABOUT 4 TO 7 DEGREES BELOW NORMAL. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY, AND SURROUNDING AREAS. TODAY...LIFR/IFR CEILINGS ARE EXPECTED TO CONTINUE FOR AWHILE THIS MORNING, WITH SOME IMPROVEMENT TO MVFR THIS AFTERNOON. WHILE AT LEAST SOME ADDITIONAL IMPROVEMENT IS POSSIBLE LATER THIS AFTERNOON, ESPECIALLY NEAR AND SOUTH OF KPHL, CONFIDENCE IS LOW ON HOW FAR NORTH A WARM FRONT GETS. THE VISIBILITIES WILL BE MVFR TO LOCALLY IFR THIS MORNING WITH SOME IMPROVEMENT EXPECTED BY MIDDAY. SOME DRIZZLE ALONG WITH SHOWERS ARE EXPECTED THIS MORNING, THEN SHOWERS AGAIN TOWARD LATER THIS AFTERNOON. SOME THUNDERSTORMS ARE POSSIBLE MOSTLY SOUTH AND WEST OF PHILADELPHIA LATER THIS AFTERNOON, HOWEVER THIS WILL DEPEND ON THE AMOUNT OF CLEARING THAT CAN OCCUR. EAST-NORTHEAST WINDS 5-10 KNOTS, BECOMING SOUTHEAST TO LOCALLY SOUTH, THEN TURNING EASTERLY AGAIN TOWARD EVENING. TONIGHT...IFR TO LIFR CEILINGS AS PLENTY OF MOISTURE REMAINS. IF A WARM FRONT IS FARTHER NORTH TO START THIS EVENING, CEILINGS COULD BE AT LEAST A LITTLE HIGHER. SHOWERS ARE EXPECTED WHICH WILL REDUCE THE VISIBILITY AT TIMES, WITH PERHAPS A FEW THUNDERSTORMS IN THE EVENING MAINLY SOUTH OF KPHL. MOSTLY NORTHEAST WINDS IN THE 4-8 KNOT RANGE. OUTLOOK... TUE/TUE NIGHT...MVFR OR IFR CONDITIONS ACROSS MOST OF THE DEL VALLEY...DELMARVA AND SRN NJ. OCNL RAIN AND FOG POSSIBLE. WED THRU FRI...MOSTLY VFR BUT LOWER CONDITIONS IN SCT SHOWERS. && .MARINE... AN ONSHORE FLOW CONTINUES TODAY AND TONIGHT, HOWEVER THIS SHOULD SHIFT TO SOUTHERLY FOR A TIME ACROSS OUR SOUTHERN WATERS BY LATER TODAY AND THIS EVENING WITH THE ARRIVAL OF A WARM FRONT. THE FLOW OVERALL REMAINS ON THE LIGHTER SIDE. IT CONTINUES TO BE RATHER MARGINAL REGARDING SEAS ESPECIALLY ACROSS THE SOUTHERN COASTAL WATERS, HOWEVER WILL KEEP THE SMALL CRAFT ADVISORY GOING FOR NOW. IT GOES UNTIL 4 PM TODAY. OTHERWISE, WINDS ARE EXPECTED TO REMAIN BELOW 25 KNOTS. SOME SHOWERS ARE EXPECTED TODAY WITH THESE BECOMING MORE NUMEROUS TONIGHT. A FEW THUNDERSTORMS ARE POSSIBLE MAINLY LATE THIS AFTERNOON AND THIS EVENING ACROSS OUR SOUTHERN WATERS, AND IF THESE DO OCCUR THEN LOCALLY GUSTY WINDS WILL BE POSSIBLE. OUTLOOK... WINDS AND SEAS SHOULD REMAIN MOSTLY BELOW SMALL CRAFT CRITERIA. OCCASIONAL SHOWERS EXPECTED THRU THE PERIOD. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS UNTIL 4 PM EDT THIS AFTERNOON FOR ANZ450>455. && $$ SYNOPSIS...O`HARA NEAR TERM...GORSE SHORT TERM...GORSE LONG TERM...O`HARA AVIATION...GORSE/O`HARA MARINE...GORSE/O`HARA

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