Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 101502 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 1102 AM EDT THU JUL 10 2014 .SYNOPSIS... A FRONTAL BOUNDARY WILL STALL TODAY NEAR THE COAST AND ACROSS THE DELMARVA, BEFORE DISSIPATING LATER TONIGHT INTO FRIDAY. HIGH PRESSURE WILL BUILD ACROSS THE NORTHEAST FRIDAY INTO SATURDAY, THEN SHIFT OFFSHORE LATER SATURDAY. A COUPLE OF COLD FRONTS ARE THEN FORECAST TO ARRIVE LATER MONDAY AND TUESDAY, HOWEVER THEY SHOULD BE SETTLING OFFSHORE ON WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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THE FRONTAL BOUNDARY HAS PUSHED NEAR THE NEW JERSEY COASTLINE SOUTHWARD THROUGH SOUTHERN DELMARVA AND WILL LIKELY REMAIN NEARLY STATIONARY THROUGH THE REMAINDER OF TODAY. AN INITIAL SHORT WAVE/VORTICITY IMPULSE IS SLIDING ACROSS THE DELMARVA/SOUTHERN NEW JERSEY THIS MORNING AND CONTINUE TO PRODUCE SCATTERED SHOWERS AND THUNDERSTORMS, SOME WHICH ARE QUITE HEAVY. THIS AREA OF RAIN IS EXPECTED TO MOVE OFFSHORE IN THE NEXT COUPLE OF HOURS, THEN WE SHOULD HAVE A BREAK, BEFORE ADDITIONAL SHOWERS AND THUNDERSTORMS DEVELOP DURING THE AFTERNOON AS A SECOND SHORT WAVE/VORTICITY IMPULSE APPROACHES FROM THE SOUTHWEST. THIS IMPULSE MAY SPARK SCATTERED/ISOLATED SHOWERS AND STORMS ACROSS MUCH OF THE AREA, BUT THE BEST CHANCES WILL BE FARTHER SOUTH CLOSER TO THE STALLED OUT FRONTAL BOUNDARY. MIXED LAYER CAPE VALUES ARE FORECAST TO APPROACH OR EXCEED 1000 J/KG MAINLY TO THE SOUTHWEST OF A READING TO PHILADELPHIA TO ATLANTIC CITY LINE. AN UPPER LEVEL JET SHOULD EXTEND FROM THE TENNESSEE RIVER VALLEY ACROSS THE NORTHEASTERN STATES TO ATLANTIC CANADA FOR TODAY. MUCH OF OUR REGION WILL BE UNDER THE RIGHT ENTRANCE REGION OF THE JET FURTHER ENHANCING THE POTENTIAL FOR SCATTERED CONVECTION. THE STATISTICAL GUIDANCE TEMPERATURES FROM THE 0000 UTC NAM AND THE 0000 UTC GFS WERE SIMILAR. BOTH MODELS SUGGEST HIGHS MAINLY IN THE MIDDLE 80S WITH MAXIMUM READINGS IN THE UPPER 70S IN OUR ELEVATED TERRAIN. WIND SPEEDS ARE FORECAST TO REMAIN GENERALLY LESS THAN 10 MPH FOR TODAY WITH A VERY WEAK PRESSURE GRADIENT IN THE VICINITY OF THE FRONT. THE WIND DIRECTION SHOULD FAVOR THE NORTHEAST TO SOUTHEAST QUADRANT.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... THE FRONT IS EXPECTED TO REMAIN ACROSS THE SOUTHERN PART OF OUR FORECAST AREA FOR MUCH OF TONIGHT. HOWEVER, THE BOUNDARY MAY BEGIN SINK TO OUR SOUTH AFTER MIDNIGHT. ANY SHOWER AND THUNDERSTORM ACTIVITY SHOULD DECREASE GRADUALLY AFTER SUNSET WITH THE LOSS OF DAYTIME HEATING. THE PRECIPITATION WILL LIKELY BECOME CONFINED TO AREAS AROUND THE FRONTAL BOUNDARY. THE WIND IS ANTICIPATED TO REMAIN LIGHT. MINIMUM TEMPERATURES SHOULD BE SIMILAR TO THOSE EXPERIENCED THIS MORNING. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... THE OVERALL SYNOPTIC SETUP IS COMPRISED OF GENERAL CYCLONIC FLOW ACROSS THE NORTHEAST AND MID ATLANTIC. THIS LOOKS TO EASE SOME SATURDAY AS HIGH PRESSURE SETTLES TO OUR EAST, HOWEVER A SIGNIFICANT UPPER-LEVEL TROUGH IS FORECAST TO DIG INTO THE MIDWEST AND UPPER GREAT LAKES REGION DURING THE COURSE OF THE WEEKEND. AS THIS OCCURS, THE FLOW ACROSS OUR AREA WILL INCREASE AND TEND TO BECOME MORE CYCLONIC WITH TIME. THIS SETUP WILL DRIVE A COLD FRONT OR TWO ACROSS OUR AREA DURING THE FIRST HALF OF NEXT WEEK. GIVEN THE IDEA OF AN AMPLIFYING UPPER-LEVEL TROUGH WITH DOWNSTREAM STRENGTHENING CYCLONIC FLOW, WE MAY HAVE A FEW DAYS WHERE IT BECOMES CONVECTIVELY ACTIVE IN OUR CWA. WE USED A MODEL BLEND FOR FRIDAY INTO SUNDAY, THEN MOSTLY BLENDED THE 00Z WPC GUIDANCE INTO CONTINUITY THEREAFTER. FOR FRIDAY...HIGH PRESSURE IS FORECAST TO SETTLE ACROSS THE AREA BEFORE BECOMING BETTER ESTABLISHED TO OUR NORTHEAST. WHILE THERE LOOKS TO BE A WEAK SHORT WAVE TROUGH MOVING THROUGH DURING THE COURSE OF THE DAY, THE OVERALL FORCING AND ENOUGH DRYING SHOULD LIMIT THE CONVECTIVE DEVELOPMENT. WE DID KEEP SLIGHT CHC TO LOW CHC POPS ACROSS THE FAR SOUTHEASTERN AREAS, WHICH ARE CLOSER TO A LINGERING OR DISSIPATING BOUNDARY. HIGH PRESSURE SHOULD THEN BE SHIFTING MORE TO NEAR THE SOUTHERN NEW ENGLAND COAST AT NIGHT. THIS WILL PROMOTE AN ONSHORE FLOW, HOWEVER IT IS NOT ALL THAT CERTAIN HOW DEEP THE MOISTURE IS AS THIS OCCURS. THERE IS A SOUTHEAST TO SOUTH FLOW AT NIGHT, HOWEVER THE PROSPECTS OF LOW CLOUDS AND OR SOME FOG LOOKS LOW ATTM AS THE NAM IN PARTICULAR MAY BE FAVORING TO MUCH PRECIPITATION. THE FORECAST SOUNDINGS APPEAR TO INDICATE LESS OF A LOW CLOUD POTENTIAL OVERALL, BUT WILL MONITOR. FOR SATURDAY AND SUNDAY...AS HIGH PRESSURE SLIPS FARTHER OFF THE SOUTHEASTERN NEW ENGLAND COAST SATURDAY MORNING, THE FLOW WILL TURN FROM EAST-SOUTHEAST TO MORE SOUTHERLY. AS THIS OCCURS, SOME INCREASE IN THE WAA AHEAD OF AN AMPLIFYING UPPER-LEVEL TROUGH INTO THE GREAT LAKES REGION SHOULD ORGANIZE A WARM FRONT TO OUR SOUTHWEST. THIS FRONT SHOULD THEN START MIGRATING NORTHWARD SUNDAY. OVERALL SATURDAY LOOKS TO BE DRY WITH HIGH PRESSURE CLOSE ENOUGH TO START AND THEN OVERALL A LACK OF ORGANIZED LIFT. AS THE UPPER-LEVEL FLOW STARTS TO TURN MORE CYCLONIC SUNDAY, SOME SHOWERS AND THUNDERSTORMS MAY DEVELOP ESPECIALLY INLAND IN THE AFTERNOON PERHAPS FOCUSED NEAR A LEE SIDE TROUGH. THIS WOULD BREAK OUR STRING OF NICE WEATHER ON THE WEEKENDS. OVERALL, WE USED A 50/50 BLEND OF CONTINUITY AND WPC GUIDANCE ESPECIALLY FOR SUNDAY. FOR MONDAY THROUGH WEDNESDAY...A SIGNIFICANT UPPER-LEVEL TROUGH IS FORECAST TO SLIDE ACROSS THE GREAT LAKES REGION AND INTO THE NORTHEAST. THIS PATTERN HAS SOME SIMILARITIES TO THE CURRENT ONE WITH LOW PRESSURE TRACKING ACROSS CANADA, WHICH THEN PULLS A COLD FRONT INTO THE EAST. THE PRESENCE OF STRENGTHENING CYCLONIC FLOW IN COMBINATION OF AN INCREASINGLY UNSTABLE AIR MASS WILL INITIATE SHOWERS AND THUNDERSTORMS. THIS MAY BE TIED TO AN INITIAL LEE SIDE TROUGH MONDAY, THEN MORE FOCUSED WITH THE COLD FRONT ALONG WITH COOLING ALOFT TUESDAY. THE INSTABILITY SHOULD BE ENHANCED SOME AS DEEPER MOISTURE ADVECTS NORTHEASTWARD IN ADVANCE OF THE SURFACE FRONT. THIS ALL COULD RESULT IN SOME STRONG CONVECTIVE EPISODES MONDAY AND TUESDAY, HOWEVER THE SEVERE WEATHER THREAT WILL DEPEND ON THE TIMING OF THE LARGE SCALE FORCING AND ORGANIZATION AS WELL AS THE ACTUAL INSTABILITY AND SHEAR. WE KEPT HIGHER END CHC POPS OVERALL FOR AT LEAST SCATTERED CONVECTION MONDAY AND TUESDAY, AS THE CONVECTIVE ORGANIZATION THIS FAR OUT CARRIES UNCERTAINTY. FOR WEDNESDAY, WE FOLLOWED CLOSER TO WPC AND TAKE THE COLD FRONT OFFSHORE. IT APPEARS THAT THE SOUTHWESTERLY PORTION OF THE UPPER- LEVEL TROUGH MAY HANG BACK TO OUR WEST, BUT WITH THE IDEA OF THE FRONT OFFSHORE WE WILL GO WITH A DRY WEDNESDAY FOR NOW. && .AVIATION /15Z THURSDAY THROUGH MONDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. LOWER CIGS/VSBYS ARE OCCURRING ACROSS SOUTHERN NEW JERSEY THIS MORNING AND WILL CONTINUE INTO THE EARLY AFTERNOON AS SCATTERED SHOWERS AND THUNDERSTORMS MOVE THROUGH THE AREA. OTHERWISE, GENERALLY VFR CONDITIONS ARE EXPECTED FOR THE REST OF THE AREA TODAY. SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE, ESPECIALLY DURING THE AFTERNOON. WHILE THERE IS NOT A PARTICULARLY HIGH PROBABILITY OF A SHOWER OR THUNDERSTORM AFFECTING TE MAJORITY OF THE TAF SITES TODAY, THE CHANCE SEEMS HIGHEST IN THE KILG, KMIV AND KACY VICINITIES. THE SCATTERED SHOWERS AND THUNDERSTORMS ARE FORECAST TO DIMINISH AFTER DARK. VFR CONDITIONS THIS EVENING MAY GIVE WAY TO AREAS OF MVFR VISIBILITY RESTRICTIONS FOR LATE TONIGHT. THE WIND SHOULD REMAIN MOSTLY LESS THAN 10 KNOTS FOR TODAY AND TONIGHT. THE DIRECTION IS EXPECTED TO FAVOR THE NORTHEAST TO SOUTHEAST QUADRANT. OUTLOOK... FRIDAY...VFR OVERALL, HOWEVER THERE MAY BE SOME MVFR CEILINGS DEVELOPING LATE AT NIGHT WITH AN EASTERLY FLOW. OUR CONFIDENCE IS ON THE LOW SIDE AT THIS TIME REGARDING LOW CLOUDS. AN ISOLATED SHOWER OR THUNDERSTORM POSSIBLE, MAINLY SOUTH OF KILG IN THE AFTERNOON. SATURDAY...PERHAPS SOME MVFR CEILINGS TO START, OTHERWISE ANY VFR CEILINGS SHOULD SCATTER OUT. SUNDAY AND MONDAY...SCATTERED SHOWERS AND THUNDERSTORMS ESPECIALLY DURING THE AFTERNOON AND EVENING HOURS. THESE WILL RESULT IN LOCAL SUB-VFR CEILINGS AND VISIBILITIES AT TIMES.
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&& .MARINE... A SLOW MOVING FRONT IS EXPECTED TO STALL ACROSS THE WATERS OF DELAWARE BAY AND SOUTHERN NEW JERSEY FOR MUCH OF TODAY AND THIS EVENING. THE BOUNDARY IS FORECAST TO SINK FARTHER TO THE SOUTH TONIGHT. SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE. WIND SPEEDS AND WAVE HEIGHTS ARE ANTICIPATED TO REMAIN BELOW THE SMALL CRAFT ADVISORY CRITERIA FOR TODAY AND TONIGHT. OUTLOOK... FRIDAY AND SATURDAY...HIGH PRESSURE ARRIVES FRIDAY THEN SHIFTS OFF THE SOUTHEASTERN NEW ENGLAND COAST FRIDAY NIGHT AND SATURDAY. THIS WILL RESULT IN AN ONSHORE FLOW THAT STRENGTHENS SOME FOR A TIME BEFORE TURNING MORE SOUTHERLY. IT APPEARS THOUGH THAT THE CONDITIONS WILL REMAIN BELOW ADVISORY CRITERIA. SUNDAY AND MONDAY...A WARM FRONT SHOULD LIFT NORTHWARD SUNDAY, ALLOWING A SOUTHWESTERLY FLOW TO OCCUR AND INCREASE SOME. HOWEVER, THE CONDITIONS OVERALL SHOULD REMAIN BELOW ADVISORY CRITERIA. SOME SHOWERS AND THUNDERSTORMS SHOULD BE ON THE INCREASE, ESPECIALLY MONDAY. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...GORSE NEAR TERM...ROBERTSON/IOVINO SHORT TERM...IOVINO LONG TERM...GORSE AVIATION...ROBERTSON/GORSE/IOVINO MARINE...GORSE/IOVINO

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