Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 301312 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 912 AM EDT SUN AUG 30 2015 .SYNOPSIS... A WEAKENING COLD FRONT WILL ARRIVE TONIGHT, OTHERWISE HIGH PRESSURE WILL REMAIN MOSTLY CENTERED NEAR THE MID ATLANTIC REGION THROUGH MUCH OF THIS WEEK. HOWEVER, A WEAK COLD FRONT MAY SLIDE INTO OUR REGION ON THURSDAY. AN OFFSHORE LOW AND HIGH PRESSURE TO OUR NORTHEAST MAY PROVIDE SOME COOLER CONDITIONS FOR NEXT WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A SHORT WAVE TROUGH WILL ARRIVE INTO THE NORTHEAST LATER TODAY, AND AS IT DOES IT SHOULD TEND TO WEAKEN. A WEAK COLD FRONT AT THE SURFACE IS TIED TO THIS FEATURE, AND WITH SOME MOISTURE ON THE INCREASE THERE ARE SOME SHOWERS CURRENTLY WITH IT TO OUR WEST. THERE IS SOME INSTABILITY DURING THE DAY, WITH THIS PROBABLY BEST ACROSS THE WESTERN ZONES. HOWEVER, THE FORECAST SOUNDINGS MOSTLY SHOW A SKINNY CAPE PROFILE WHICH TENDS TO KEEP UPDRAFTS ON THE WEAKER SIDE. THE BULK OF THE LIFT ASSOCIATED WITH THE TROUGH AXIS IS FORECAST TO BE TO OUR WEST DURING PEAK HEATING WITH THE ACTUAL SHORT WAVE AND THE RIGHT ENTRANCE REGION OF AN UPPER-LEVEL JET. HOWEVER, TERRAIN INFLUENCES AND A WEAK SURFACE TROUGH COULD COME INTO PLAY AND THEREFORE WE KEPT A SLIGHT CHC POP DURING THE AFTERNOON ACROSS THE NORTHWESTERN ZONES. SOME INCREASE IN THE CLOUDS IS EXPECTED ESPECIALLY ACROSS THE WESTERN ZONES IN ADVANCE OF THE AFOREMENTIONED SHORT WAVE. IT WILL BE RATHER WARM TO HOT ACROSS MUCH OF THE CWA THIS AFTERNOON, HOWEVER DEW POINTS MAY LOWER A LITTLE BIT THIS AFTERNOON IN SOME AREAS DUE TO SIGNIFICANT HEATING OF THE BOUNDARY LAYER. THE PRESSURE GRADIENT IS NOT FORECAST TO BE ALL THAT TIGHT, THEREFORE LIGHT ENOUGH FLOW SHOULD RESULT IN A SEA BREEZE ONCE AGAIN THIS AFTERNOON. THE HOURLY GRIDS WERE ADJUSTED BASED ON THE LATEST OBSERVATIONS, THEN THE LAMP/LAV GUIDANCE WAS BLENDED IN TO ASSIST. NO MAJOR CHANGES WERE MADE TO THE HIGH TEMPERATURES ATTM. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/... ANY ISOLD SHWRS OR TSTMS WILL COME TO AN END AND THEN EXPECT JUST A PCLDY SKY WITH GRADUALLY INCREASING DEW PTS, AS THE HIGH REMAINS THE DOMINANT WX FEATURE AS WE CLOSE OUT AUGUST AND METEOROLOGICAL SUMMER. && .LONG TERM /MONDAY THROUGH SATURDAY/... SOME SHIFTS IN TRACKS AND TIMING WITH THE LATEST MODEL RUNS, BUT THE MAIN STORY REMAINS THE HIGH SLIDING OVER THE REGION FOR MUCH OF THE WORK WEEK. MONDAY THROUGH WEDNESDAY...MAY SEE A FEW LINGERING SHOWERS OR THUNDERSTORMS MONDAY MORNING AS AN UPPER LEVEL SHORT WAVE TROUGH MOVES FURTHER AWAY FROM THE REGION, BUT OTHERWISE PRECIPITATION CHANCES THROUGH THIS PERIOD ARE VERY SLIM. SHOULD SEE A MODEST WARMING TREND FROM MONDAY INTO TUESDAY AS THE RIDGE AXIS SLIDES OVERHEAD, THUS LEADING TO INCREASING 1000-500 MB THICKNESSES FOR THE REGION. EVEN WITH THIS HIGH AMPLITUDE RIDGE THOUGH, HIGHS SHOULD STAY WELL BELOW RECORDS, AND HEAT INDEX VALUES SHOULD STAY IN THE LOWER TO MID 90S. THURSDAY...A BIT MORE UNCERTAINTY IN THIS PERIOD, SPECIFICALLY WITH THE EVOLUTION OF THE WEAK COLD FRONT. SOME MODELS ARE NOW STALLING THIS FRONT WELL NORTH OF THE REGION, OR SHOWING THE TEMPERATURE GRADIENT ALMOST DISAPPEAR COMPLETELY BY THE TIME IT REACHES OUR REGION. FOR NOW THOUGH, HAVE STAYED CLOSE TO THE PREVIOUS FORECAST FOR BOTH TEMPERATURES AND PRECIPITATION CHANCES, AS THE UPPER LEVEL SHORT WAVE TROUGH COULD PROVIDE ENOUGH LIFT AND FOCUS FOR CONVECTION EVEN WITHOUT THE FRONT, AND STILL THINK THERE IS A CHANCE THE FRONT WILL REACH THE AREA GIVEN THAT THE MODELS TEND TO UNDERESTIMATE HOW FAR SOUTH FRONTS WILL PROPAGATE IN THE TRANSITION SEASONS. FRIDAY THROUGH SATURDAY...STAYED RELATIVELY CLOSE TO THE PREVIOUS FORECAST AS THERE ARE SOME LARGE DIFFERENCES AMONG THE LONG RANGE MODELS IN THIS PERIOD. THE GFS SHOWS STEADY ON SHORE FLOW AS A SURFACE HIGH DEVELOPS TO OUR NORTHWEST. MEANWHILE, THE ECMWF SHOWS A VERTICALLY STACKED, AND NEARLY STATIONARY, LOW TO OUR SOUTHEAST. EITHER SOLUTION THOUGH DOES LOOK TO BRING A COOLING TREND THROUGH THE WEEKEND. && .AVIATION /13Z SUNDAY THROUGH THURSDAY/... THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REST OF TODAY...VFR WITH SOME CUMULUS DEVELOPING AROUND 5000 FEET. LIGHT SOUTHWESTERLY WINDS INCREASING UP TO 10 KNOTS, WHICH SHOULD TURN MORE SOUTHERLY AT KACY AND PERHAPS KILG DUE TO A SEA/BAY BREEZE. THERE IS A LOW CHANCE A SHOWER OR THUNDERSTORM APPROACH THE KABE TO KRDG AREAS TOWARD EVENING. TONIGHT...VFR OVERALL. A WEAKENING COLD FRONT SHOULD ALLOW A SHOWER OR THUNDERSTORM TO ARRIVE NEAR THE KABE AND KRDG AREAS THIS EVENING, HOWEVER COVERAGE IS EXPECTED TO BE VERY LOW. SOUTHWESTERLY WINDS 5- 10 KNOTS, BECOMING LIGHT AND VARIABLE AT MANY OF THE TERMINALS. OUTLOOK... MONDAY THROUGH WEDNESDAY...VFR CONDITIONS EXPECTED THOUGH LOCALIZED MVFR CONDITIONS WITH FOG POSSIBLE EACH MORNING. THURSDAY...MOSTLY VFR CONDITIONS. ISOLATED THUNDERSTORMS POSSIBLE. && .MARINE... NO MARINE FLAGS ARE ANTICIPATED THRU THE NR AND SHORT TERM PDS. SEAS WILL GENLY BE IN THE 2 TO 4 FT RANGE. WIND WILL GENLY BE SW IN THE 10 TO 15 KT RANGE WITH GUSTS AS HIGH AS 20 KT. OUTLOOK... MONDAY THROUGH THURSDAY...WINDS AND SEAS SHOULD STAY WELL BELOW SMALL CRAFT ADVISORY CRITERIA. WATER TEMPERATURES ARE ABOVE NORMAL. && .RIP CURRENTS... A LONG PERIOD EAST TO SOUTHEAST SWELL, 10-11 SECONDS, CONTINUES TO ROLL IN ALONG THE COAST. THIS COMBINED WITH WINDS TURNING MORE SOUTHERLY AND INCREASING SOME THROUGH THE DAY WILL RESULT IN TRICKY CONDITIONS AT TIMES WITHIN THE SURF ZONE ESPECIALLY DURING TIDE CHANGES. AS A RESULT THERE IS A MODERATE RISK FOR THE DEVELOPMENT OF DANGEROUS RIP CURRENTS THROUGH THIS EVENING, AND THE DELAWARE BEACHES ARE NOW ALSO INCLUDED IN THIS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GORSE/JOHNSON NEAR TERM...GORSE SHORT TERM...NIERENBERG LONG TERM...JOHNSON AVIATION...GORSE/JOHNSON MARINE...JOHNSON/NIERENBERG RIP CURRENTS...GORSE

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