Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 211533 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1133 AM EDT TUE APR 21 2015 .SYNOPSIS... A COLD FRONT WILL MOVE RAPIDLY OFFSHORE THIS MORNING. REINFORCING COLD FRONTS WILL MOVE THROUGH THE MID ATLANTIC STATES ON WEDNESDAY AND THURSDAY. A LOW PRESSURE SYSTEM SHOULD THEN SLIDE SOUTH OF THE AREA PASSING OFF THE CAROLINA COAST ON SATURDAY. A HIGH PRESSURE WILL GRADUALLY BUILD IN FROM THE WEST THROUGH THE REMAINDER OF THE WEEKEND INTO MONDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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THE COLD FRONT AND ITS ASSOCIATED RAINS HAVE MOVED TO THE EAST. RAPID CLEARING HAS OCCURRED ACROSS THE REGION...WITH SOME DAYTIME CU POPPING ACROSS THE N/W AREAS. WINDS HAVE INCREASED AND SOME GUSTINESS HAS DEVELOPED. TEMPS/DEW POINTS OK FOR NOW. ANOTHER SHORT WAVE/VORTICITY IMPULSE IS FORECAST TO APPROACH THE AREA LATER IN THE DAY. WITH STEEP LOW/MID LEVEL LAPSE RATES AND SOME LOW/MID LEVEL MOISTURE FORECAST ACROSS OUR NORTHERN AREAS, THERE COULD BE SOME ISOLATED SHOWERS DEVELOP LATER IN THE DAY. SO WE INCLUDE A SLIGHT CHANCE OF SHOWERS THIS AFTERNOON ACROSS THE NORTHERN TIER OF THE AREA.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/... ANY SHOWERS THAT DEVELOP DURING THE DAY ARE EXPECTED TO HAVE DIMINISHED BY SUNSET AS WE LOSE DAYTIME HEATING. WE DO EXPECT AN INCREASE IN MID-LEVEL CLOUD COVER AS A SHORT WAVE/VORTICITY IMPULSE SLIDES ACROSS THE AREA. RIGHT NOW IT DOES NOT LOOK LIKE THERE WILL BE DEEP ENOUGH MOISTURE TO CREATE ANY SHOWERS, SO WE KEEP THE FORECAST DRY. A BLEND OF MAV/MET MOS AND MOSGUIDE WAS USED FOR OVERNIGHT LOWS, WHICH BRINGS EVERYONE PRETTY CLOSE TO NORMAL. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... THE LONG TERM WILL FEATURE AN ALL TOO FAMILIAR PATTERN OF CLOSED LOWS LINGERING ACROSS SOUTHEAST CANADA AND NORMAL TO COOLER THAN NORMAL WEATHER PATTERN PREVAILING. THE GFS AND WRF 500MB INITIALIZATION LOOKED GOOD. THEY BOTH WERE INTERMITTENTLY TOO COLD AT 850MB AND 925MB AT UPSTREAM SITES. ON WEDNESDAY, A REINFORCING COLD FRONT IS PREDICTED TO MOVE THROUGH OUR CWA. THIS HAS DECENT MID AND UPPER LEVEL SUPPORT (QVEC CONVERGENCE, EXIT REGION OF THE 250MB JET) AS WELL AS PREDICTED LOW LEVEL THETA E RIDGING. COMING QUICKLY ON THE HEELS OF THE CURRENT SYSTEM THERE WILL NOT BE MUCH AIR MASS RECOVERY FOR HEAVIER PCPN. BUT FORECAST SOUNDINGS ARE SHOWING THE INVERTED V LOOK AND THERE COULD BE SOME GUSTY SHOWERS OR TSTMS AS PCPN MOVES ACROSS THE AREA. BOTH THE NAM AND GFS ARE FAIRLY BULLISH WITH WIND GUSTS REACHING OR EXCEEDING 35 MPH. GIVEN DECENT MODELING CONSENSUS ABOUT SHOWERS, WE UPPED POPS TO LIKELY. THERE ARE DIFFERENCES AS TO WHETHER OR NOT A RIBBON OF INSTABILITY CAPABLE OF PRODUCING THUNDER WILL BE SUFFICIENT. WE ADDED LOW CHANCES DURING THE AFTERNOON OVER THE SOUTHEASTERN TWO THIRDS OF OUR CWA WHERE DAYTIME HEATING SHOULD HAVE MORE TIME TO GENERATE INSTABILITY. ODDLY A FASTER CFP DID NOT TRANSFER INTO LOWER GFS MOS MAX TEMPS AND WE PREFER THEIR HIGHER NUMBER BASED ON FCST 925MB TEMPS. UNLIKE NOW WHERE PCPN IS LINGERING AND LINGERING AND LINGERING, SHOWERS/TSTMS WEDNESDAY SHOULD BE MORE DIURNALLY DRIVEN AND DECREASE RAPIDLY WITH SUNSET. THE ONE EXCEPTION IS FAR NORTHWEST WHERE A SHORT WAVE ROUNDING THE BASE OF THE 500MB TROF COULD KEEP PCPN CHANCES GOING INTO THE NIGHT AND THURSDAY MORNING. HIGHER TERRAIN LOCATIONS WOULD BE COLD ENOUGH FOR POSSIBLY SOME SNOW SHOWERS. BETWEEN THE CHANNELIZED VORT MAX AND CONVECTIVE TEMPS WITHIN REACH, SELF DESTRUCT SUNSHINE SHOULD BE OCCURRING ON THURSDAY. ONCE AGAIN GFS MOS AGREES MORE WITH THE NAM`S THERMAL PROFILES THAN ITS COLDER OWN. NOT MUCH CHANGE FROM CONTINUITY, A COOLER STEP DOWN OF MAX TEMPS. WITH THE SURFACE AND UPPER LOW LINGERING OVER SOUTHEASTERN CANADA, THERE SHOULD BE TOO MUCH OF A GRADIENT FOR RADIATIONAL COOLING IN PLACES WHERE THE GROWING SEASON HAS MADE STRIDES THE LAST WEEK OR SO. SUB FREEZING MINS WERE KEPT FAR NORTH. ANOTHER BREEZY BUT DRY DAY FRIDAY. POSSIBLY LESS SELF DESTRUCT SUNSHINE THAN THURSDAY AS PREDICTED MOISTURE IS LESS. MAX TEMPS THOUGH ARE FORECAST TO BE SIMILAR TO THURSDAY, COOLER THAN NORMAL. FRIDAY NIGHT HAS A GREATER CHANCE TO BE A FROSTY ONE AS WEAK HIGH PRESSURE COMES CLOSER TO OUR CWA. ON SATURDAY (THIS SOUNDS LIKE A WINTER SCENARIO), A SOUTHERN SLIDER LOW PRESSURE SYSTEM IS PREDICTED TO PASS OFF THE CAROLINA COAST. AS LONG AS THE ANTECEDENT UPPER CLOSED/SFC LOW REMAIN LINGERING OVER THE CANADIAN MARITIMES, THIS NEW LOW MAY NOT HAVE THE ABILITY TO TURN THE CORNER AND AFFECT US. THE LATEST ECMWF BACKED OFF ON PCPN EXTENT AND WE KEPT THE LOW CHANCE FAR SOUTH BECAUSE OF ITS CLOSER PROXIMITY TO THE EXITING LOW. THEN NOT MUCH CHANGE FOR SUNDAY AND MONDAY AS THE AIR MASS SHOULD RECOVER SLIGHTLY AS THE MARITIME SYSTEM`S COLD AIR SUPPLY BECOMES STALER. && .AVIATION /16Z TUESDAY THROUGH SATURDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDITIONS HAVE RETURNED TO THE TAF SITES AND THEY SHOULD REMAIN TONIGHT AND TUESDAY MORNING. ONLY SOME SCT CU EARLY THIS AFTERNOON...A CIG MAY DEVELOP ACROSS THE N/W AREAS LATER ON...VFR THOUGH. WIND GUSTS OF 25-30 KNOTS HAVE DEVELOPED AND SHOULD REMAIN THROUGH THE DAY. THE GUSTS WILL DROP OFF AROUND OR AFTER SUNSET TONIGHT AND BECOME MORE SOUTHWEST OVERNIGHT. OUTLOOK... WEDNESDAY...MAINLY VFR CONDITIONS EXPECTED WITH SUB-VFR SHOWERS AND TSTMS POSSIBLE AS A COLD FRONT CROSSES THE REGION. GUSTY SOUTHWEST TO WEST WINDS SHOULD EXCEED 30 KNOTS, ESPECIALLY IN PROXIMITY TO ANY SHOWERS. WEDNESDAY NIGHT THROUGH FRIDAY NIGHT...MAINLY VFR CONDITIONS EXPECTED. SOME GUSTY DAYTIME NORTHWEST WINDS EXPECTED. SATURDAY...MAINLY VFR CONDITIONS...LOWEST CONFIDENCE SOUTHERN AIRPORTS AS SHOWERS MIGHT OCCUR THERE.
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&& .MARINE... THE SMALL CRAFT ADVISORY REMAINS ON THE OCEAN AS WIND GUSTS OF 25 KNOTS SHOULD INCREASE TODAY BEHIND THE COLD FRONT AND SEAS WILL REMAIN ELEVATED. THE ADVISORY REMAINS IN PLACE ON THE LOWER DELAWARE BAY AND WE HAVE EXPANDED THE ADVISORY INTO THE NORTHERN DELAWARE BAY AS WINDS WILL INCREASE TODAY BEHIND THE FRONT ON THE BAY. ALL OF THE ADVISORIES END AT 6 PM TONIGHT, ALTHOUGH IT IS POSSIBLE THE ADVISORY ON THE OCEAN MAY NEED AN EXTENSION IN TIME FOR A FEW HOURS THIS EVENING IF SEAS TAKE LONGER TO SUBSIDE. OUTLOOK... WEDNESDAY...AN INCREASING SOUTHWEST GRADIENT PRECEDING THE NEXT COLD FRONT COULD BRING SMALL CRAFT ADVISORY CONDITIONS BACK TO ALL OF THE AREA WATERS. WEDNESDAY NIGHT THROUGH THURSDAY...BORDERLINE SMALL CRAFT ADVISORY CONDITIONS ARE OUTLOOKED AS A NORTHWEST GRADIENT WIND WILL PERSIST. THURSDAY NIGHT AND FRIDAY...NEAR SMALL CRAFT ADVISORY CONDITIONS ARE OUTLOOKED. THE PERSISTENT NORTHWEST FLOW MIGHT WEAKEN SLIGHTLY. FRIDAY NIGHT AND SATURDAY...GREATER CONFIDENCE ABOUT SUB SMALL CRAFT ADVISORY CONDITIONS. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ430- 431-450>455. && $$ SYNOPSIS...GIGI/MEOLA NEAR TERM...GAINES/GIGI/ROBERTSON SHORT TERM...ROBERTSON LONG TERM...GIGI AVIATION...GIGI/ROBERTSON/MEOLA MARINE...GIGI/ROBERTSON/MEOLA

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