Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 231622 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1222 PM EDT MON MAR 23 2015 .SYNOPSIS... HIGH PRESSURE CENTERED NEAR THE UPPER GREAT LAKES WILL EXPAND SOUTHEASTWARD AND OVER OUR AREA THROUGH TUESDAY. A WARM FRONT ARRIVES ON WEDNESDAY, FOLLOWED BY A STRONG COLD FRONT THURSDAY NIGHT. HIGH PRESSURE THEN STARTS TO BUILD TOWARD THE MID ATLANTIC SATURDAY INTO SUNDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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HIGH PRESSURE OVER THE GREAT LAKES REGION WILL CONTINUE TO EXPAND SOUTHEASTWARD AND OVER OUR AREA. THIS IS ALLOWING FOR LESS WIND COMPARED TO YESTERDAY. THE AIRMASS IS COLD AND WITH LESS MIXING THE TEMPERATURES ARE SLOWER TO RESPOND TO THE SUNSHINE THUS FAR. OVER THE PAST HOUR OR SO, A BIT MORE INCREASE HAS BEEN NOTED. THE UPDATED HOURLY TEMPERATURE GRIDS WERE ADJUSTED TO ACCOUNT FOR THESE TRENDS. IN ADDITION, THE HIGH TEMPERATURES WERE LOWERED SOME. THE LIGHTER WINDS ESPECIALLY ACROSS THE SOUTH IS RESULTING IN THE FLOW STARTING TO TURN MORE ONSHORE AT THE COAST. THEREFORE, ALSO LOWERED THE HIGHS SOME ALONG THE IMMEDIATE COAST. AN UPPER-LEVEL TROUGH REMAINS ACROSS THE EAST AND A STRONG SHORT WAVE IS ROUNDING THE TROUGH IN NEW ENGLAND. SOME LIMITED FLAT STRATOCUMULUS MAINLY UP NORTH, OTHERWISE SOME HIGH LEVEL CLOUDS AT TIMES AS A SHEARING SHORT WAVE PASSES WELL TO OUR SOUTH.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... THE AFOREMENTIONED HIGH MOVES EVEN CLOSER OVERNIGHT AND A DRY FCST IS IN STORE. THE WIND SHUD GENLY BE LIGHT, BUT A S/WV IS EXPECTED TO MOVE ACRS SRN AREAS AND THIS WILL CAUSE AN INCREASE IN CLOUDS. && .LONG TERM /TUESDAY THROUGH SUNDAY/... TUESDAY...ONE LAST QUIET BUT COOL DAY IS ON TAP AS THE SURFACE HIGH WILL BE RIGHT OVER THE REGION BEFORE SHIFTING OFF SHORE TUESDAY NIGHT. WEDNESDAY...THE MAIN QUESTION THROUGH THIS DAY WILL BE THE TIMING OF THE WARM FRONT AND HOW MUCH, IF ANY, PRECIP WE WILL HAVE WITH THE INITIAL FRONTAL PASSAGE. OF NOTE WITH TODAY/S MODEL RUNS IS THE TREND TOWARDS DRIER WITH THE INITIAL WARM FRONT PASSAGE. THE NAM, ECMWF, AND CMC ALL SHOWED THIS TREND, ALTHOUGH TO VARYING DEGREES, OVER THE LAST FEW MODEL RUNS. GFS HAD BEEN SHOWING THIS TREND, BUT TRENDED BACK TO WETTER WITH THE 00Z RUN. RELATED TO THIS, THE PREVIOUSLY MENTIONED MODELS NOW SHOW THE INITIAL LOW SURFACE LOW AND UPPER LEVEL SHORT WAVE TROUGH ASSOCIATED WITH THE WARM FRONT TRACKING FURTHER NORTH. WEDNESDAY NIGHT INTO THURSDAY...BY WEDNESDAY NIGHT THE SECONDARY SURFACE LOW AND UPPER LEVEL SHORT WAVE TROUGH BEGIN THEIR APPROACH TOWARDS THE REGION, AND WITH PLENTY OF MOIST AIR IN PLACE, SHOULD RESULT IN WIDESPREAD RAIN ACROSS THE REGION. CONTINUED SOUTHWESTERLY FLOW SHOULD HELP TO WARM THE LOW LEVELS AND INCREASE INSTABILITY. EVEN SO, MODEL CAPE VALUES, EVEN FOR MU CAPE, ARE LIMITED (GENERALLY LESS THAN 500 J/KG. THEREFORE, WHILE THERE IS STILL A SMALL CHANCE FOR THUNDERSTORMS, WOULD NOT EXPECT WIDESPREAD THUNDERSTORMS ACROSS THE REGION UNLESS THERE IS MORE WARM AIR ADVECTION IN THE LOW LEVELS AND THE COLD FRONT WILL HOLD OFF IT`S ARRIVAL UNTIL VERY LATE IN THE DAY ON THURSDAY (A FEW 00Z MODEL RUNS DID TREND THIS WAY). BULK SHEAR VALUES (FOR THE 0-6 KM LAYER) LOOK TO BE NEAR 50 KT ESPECIALLY AS THE COLD FRONT APPROACHES. SO IF STORMS DO DEVELOP, A FEW STRONG STORMS ARE NOT OUT OF THE QUESTION DESPITE THE LIMITED CAPE VALUES. COLD FRONT IS EXPECTED TO QUICKLY SWEEP THROUGH EITHER THURSDAY EVENING OR OVERNIGHT. FRIDAY THROUGH SUNDAY... BOTH THE GFS AND ECMWF CONTINUED THE TREND STARTED YESTERDAY WITH DRY AIR ADVECTION DOMINATING ANY LIFT ASSOCIATED WITH THE TRAILING UPPER LEVEL TROUGH. ALSO, MOST MODELS AND ENSEMBLE MEMBERS NOW SHOW THE COASTAL LOW TAKING A TRACK WELL OUT TO SEA AT THIS TIME. GIVEN THE ROSSBY NUMBER OF 5 AND THE RECENT PATTERN, WOULD THINK THIS WOULD BE A MORE PROGRESSIVE PATTERN, THUS WOULD FAVOR THE LOW BEING WELL EAST OF THE REGION. THEREFORE, TRENDED POPS DOWN THROUGH THIS PERIOD. SUNDAY NIGHT AND MONDAY...A FAST MOVING UPPER LEVEL TROUGH COULD CROSS THE REGION THROUGH THIS PERIOD, THOUGH THERE ARE CONSIDERABLE DIFFERENCES IN THE TIMING BETWEEN THE GFS AND ECMWF. && .AVIATION /16Z MONDAY THROUGH FRIDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. THIS AFTERNOON...VFR WITH MAINLY SOME HIGH CLOUDS AT TIMES. NORTH-NORTHWEST WINDS NEAR 10 KNOTS, HOWEVER A LIGHTER FLOW DEVELOPING MAY ALLOW THE SURFACE WINDS TO TURN MORE SOUTHWEST OR SOUTH FOR A TIME AT KPHL AND KACY. TONIGHT...VFR, WITH INCREASING CLOUDS AND A CEILING DEVELOPING. NORTH-NORTHEAST WINDS LESS THAN 10 KNOTS. OUTLOOK... TUESDAY...VFR CONDITIONS EXPECTED. WEDNESDAY...CEILINGS MAY BEGIN TO LOWER TO MVFR WITH RA. THURSDAY...MVFR AND POSSIBLY IFR CEILINGS FOR MUCH OF THE DAY. VISIBILITY RESTRICTIONS IN SHRA AND ISOLATED TSRA POSSIBLE AS WELL. GUSTY WINDS POSSIBLE BEHIND A COLD FRONT LATE ON THURSDAY. FRIDAY...CEILINGS EXPECTED TO GRADUALLY INCREASE TO VFR.
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&& .MARINE...
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THE FLOW IS DIMINISHING OVERALL AND THEREFORE A NORTH OR NORTHWEST FLOW MAY TURN ONSHORE FOR A TIME THIS AFTERNOON ESPECIALLY ACROSS THE SOUTHERN WATERS INTO DELAWARE BAY. AS HIGH PRESSURE AT THE SURFACE CONTINUES TO SETTLE IN, THE WINDS AND SEAS ARE EXPECTED TO BE BELOW SCA CRITERIA THROUGH TONIGHT. OUTLOOK... TUESDAY AND WEDNESDAY...WINDS AND SEAS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA. THURSDAY AND FRIDAY...SOUTHWESTERLY WINDS WILL WILL QUICKLY INCREASE ABOVE 25KT EARLY ON THURSDAY. WINDS WILL STAY GUSTY AND SHIFT QUICKLY WITH A COLD FRONT EXPECTED LATE IN THE DAY ON THURSDAY OR OVERNIGHT THURSDAY NIGHT. WINDS GUSTING TO NEAR 30 KT POSSIBLE. SEAS WILL SUBSEQUENTLY INCREASE AND SCA CONDITIONS ARE EXPECTED THROUGH THE DAY FRIDAY.
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&& .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...GORSE/JOHNSON/NIERENBERG

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