Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 311048 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 648 AM EDT THU JUL 31 2014 .SYNOPSIS... SEVERAL WEAK SURFACE TROUGHS WILL MOVE INTO THE AREA THROUGH FRIDAY, BEFORE HIGH PRESSURE OVER THE WESTERN ATLANTIC PUSHES AN OFFSHORE WARM FRONT NORTHWESTWARD ACROSS THE EAST COAST THIS WEEKEND. SEVERAL DISTURBANCES WILL MOVE NORTHEAST ALONG THIS BOUNDARY THROUGH THE WEEKEND. ANOTHER COLD FRONT WILL THEN MOVE ACROSS THE AREA LATE TUESDAY INTO WEDNESDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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MID AND UPPER LEVEL SHORT WAVE TROUGH LIFTS NORTHEAST OVER THE REGION TODAY. INSTABILITY IS SOMEWHAT LIMITED (ML CAPE VALUES ARE GENERALLY 500 J/KG OR LESS AND CONVECTIVE TEMPS ARE NEAR OR JUST BELOW FORECAST HIGHS), BUT NOT NEGLIGIBLE. HOWEVER, PEAK HEATING AND, THUS PEAK INSTABILITY LOOKS TO OCCUR AFTER THE SHORTWAVE BEGINS TO LIFT AWAY FROM THE REGION. HIGHEST CHANCE LOOKS TO BE FURTHER NORTH CLOSER TO THE SHORT WAVE TROUGH, AND THUS SLIGHTLY HIGHER EFFECTIVE SHEAR. EVEN SO, GIVEN THE LIMITING FACTORS, EXPECT ISOLATED TO SCATTERED COVERAGE AT MOST. WITH THE BROAD TROUGH STILL REMAINING NW OF THE REGION, AND SOME CLOUD COVER THROUGH THE DAY, EXPECT TEMPERATURES TO ONCE AGAIN BE BELOW NORMAL.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/... THE PREVIOUSLY MENTIONED SHORT WAVE TROUGH SHOULD BE WELL NORTHEAST OF THE REGION BY 00Z. IN ITS WAKE, MEAN FLOW TRANSITIONS TO SOUTHWESTERLY. WITH WARM WATERS, AND STILL RELATIVELY COOL AIR, THIS COULD BE ENOUGH FOR SHOWERS TO DEVELOP OVER THE BAYS AND MOVE INTO DELMARVA AND FAR SOUTHERN NJ. EVEN IF ANY THING DEVELOPS, COVERAGE SHOULD BE VERY LIMITED GIVEN THE MEAGER INSTABILITY IN PLACE. OVERNIGHT CLOUD COVER IS EXPECTED TO BE A BIT MORE EXPANSIVE, AND INCREASING LOW LEVEL MOISTURE WILL LIMIT COOLING, SO SHOULD SEE LOWS NEAR NORMAL TONIGHT. IF THE CLOUD COVER IS NOT AS PERSISTENT AS FORECAST, A VERY WEAK UP SLOPE AND ON SHORE FLOW IN ADDITION TO THE INCREASING MOISTURE COULD LEAD TO PATCHY VALLEY AND NEAR SHORE FOG. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... MEDIUM RANGE GUIDANCE STILL SHOWING DECENT CONSISTENCY OVER THE PAST SEVERAL DAYS, THROUGH AT LEAST THE WEEKEND, WITH THE EVOLUTION AND MOVEMENT OF THE WESTERN ATLANTIC RIDGE AND OFFSHORE SURFACE BAROCLINIC ZONE. TEMPERATURES LOOK TO BE SEVERAL DEGREES BELOW NORMAL THROUGH THE WEEKEND WITH A MODERATING TREND EXPECTED TO OCCUR EARLY NEXT WEEK. FRIDAY...DEEPER MOISTURE ADVECTS INTO THE REGION WITH RIDGING OFFSHORE BUILDING AND HEIGHTS ACROSS THE EAST COAST BEGINNING TO INCREASE. BETTER INSTABILITY OVER THE WESTERN SECTIONS OF THE CWA WITH MORE MID-LEVEL IMPULSE ACTIVITY SHOULD LEAD TO EVEN MORE SCATTERED CONVECTION DURING THE PEAK HEATING HOURS. WEAK SURFACE CONVERGENCE UNDER A PREDOMINANT SOUTH-SOUTHEAST FLOW WILL AIDE IN BETTER LIFT FOR SHOWER ACTIVITY ALONG THE HIGHER TERRAIN. TEMPERATURES SHOULD AGAIN END UP COOLER THAN NORMAL. SATURDAY...ANOTHER 24 HOURS LATER AND THERE IS STILL A GLARING DIFFERENCE ALONG THE NEW JERSEY COASTLINE WITH THE TRACK OF A SURFACE WAVE EARLY THIS WEEKEND. THE NCEP MODELS CONTINUE TO WAVER BETWEEN AN OFFSHORE SOLUTION AND ONE CLOSER TO THE COAST, WHILE THE NON-NCEP SUITE HAS BEEN PRETTY CONSISTENT BRINGING THE WAVE RIGHT ACROSS THE DELMARVA INTO EASTERN NEW JERSEY. THE TIMING OF THE STRONGER SURFACE WAVES IS ALSO SUSPECT WITH NCEP MODELS SHOWING BETTER FORCING ON SUNDAY WHILE THE NON-NCEP GROUP HAVE IT ON SATURDAY. WITH SUCH AN ANOMALOUS TROUGH IN PLACE THE NUMERICAL GUIDANCE IS NOT HANDLING THE TIMING OF THE EMBEDDED SHORTWAVES WELL, EVEN WITHIN 24 HOURS OF THE EVENT. THIS REMAINS THE BIGGEST FLY IN THE OINTMENT FOR SATURDAY`S POTENTIAL BUT THINKING THAT A FASTER PROGRESSION IS LIKELY. UPPER LEVEL JET DYNAMICS WITH THE RIGHT ENTRANCE REGION SITTING ACROSS THE MID-ATLANTIC AND AMPLE SUB-TROPICAL MOISTURE AVAILABLE TO TAP INTO, WE COULD BE LOOKING AT A HEAVY RAIN POTENTIAL...GREATER CHANCES EAST OF THE RIVER CLOSER TO THE FRONTAL BOUNDARY. STILL A GREAT DEAL OF UNCERTAINTY AT THIS POINT, THOUGH IT COULD BE MORE TO DO WITH A SMALLER SAMPLE SIZE OF SYNOPTIC PATTERNS SIMILAR TO THE ONE WE ARE IN. SUNDAY...THERE LOOKS TO BE A DRY PERIOD, AT LEAST THE FIRST HALF OF THE DAY, BEFORE MORE SCATTERED SHOWERS WITH EMBEDDED THUNDER COMMENCES. NCEP GUIDANCE PEGS SUNDAY AS THE MAIN ACTION DAY WITH THE NON-NCEP MEMBERS KEEPING THE FRONT NEARBY BUT HONING IN ON A STRONGER MID-LEVEL SHORTWAVE, COLD POOL, SWEEPING THROUGH DURING THE AFTERNOON HOURS. EVEN WITH A MORE PREDOMINANT EASTERLY FLOW, THE COLDER AIR ALOFT, WITH HIGHER THAN NORMAL PWATS, SHOULD BE ABLE TO OVERCOME A SLIGHTLY MORE STABLE SURFACE TO IGNITE ISOLATED TO SCATTERED CONVECTION. MONDAY - WEDNESDAY...SLIGHT DRYING TREND EXPECTED ON MONDAY THOUGH NOT ENTIRELY VOID OF ANY SHOWERS WITH COLD AIR STILL ALOFT WITH A FEW MORE SHORTWAVES SHEARING ACROSS OVERHEAD. HIGH PRESSURE SHOULD BE NOSING IN BY TUESDAY TO ALLOW FOR BETTER DRYING. MORE MOISTURE AND HEAT ADVECTS IN AND COULD PUSH TEMPERATURES BACK TO NORMAL. && .AVIATION /12Z THURSDAY THROUGH MONDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. FOR THE 12Z TAFS...MOSTLY VFR CONDITIONS SHOULD CONTINUE THROUGH AT LEAST 06Z. THERE IS A SLIGHT RISK OF SHRA AND TSRA ACROSS THE REGION. FIRST THIS AFTERNOON, WITH THE HIGHEST RISK AT KABE AND KTTN. THEN OVERNIGHT TONIGHT, KILG MAY BE ON THE NORTHERN EDGE OF OVERNIGHT SHRA. IN BOTH CASES, COVERAGE SHOULD BE VERY LIMITED, SO HAVE ONLY INCLUDED A VCSH MENTION FOR NOW. THERE IS ALSO A RISK OF BR DEVELOPING AFTER 00Z, LEADING TO MVFR VISIBILITIES. AT THIS TIME, BR LOOKS LIKELY AT KMIV AND KACY GIVEN WEAK ON SHORE FLOW AND INCREASING LOW LEVEL MOISTURE. FOR THE REST OF THE TERMINALS A COMBINATION OF MID LEVEL CLOUDS AND SLIGHTLY HIGHER DEW POINT DEPRESSIONS MEANS A MUCH LOWER RISK OF BR. OUTLOOK... FRIDAY - SUNDAY...MOSTLY VFR WITH SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE EACH AFTERNOON. LOCAL SUB-VFR CONDITIONS IN SHOWERY ACTIVITY. MEDIUM CONFIDENCE. MONDAY - TUESDAY...VFR. ISOLATED SHOWERS POSSIBLE ON MONDAY.
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&& .MARINE... EXPECT WINDS AND SEAS TO REMAIN BELOW SMALL CRAFT ADVISORY TODAY AND TONIGHT WITH WINDS STAYING NEAR OR BELOW 15 KT AND SEAS BETWEEN 2 AND 3 FEET. OUTLOOK... FRIDAY - MONDAY...SUB-SCA CONDITIONS ARE EXPECTED ACROSS OUR WATERS THIS PERIOD. && .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...NONE. && $$ SYNOPSIS...ROBERTSON NEAR TERM...JOHNSON SHORT TERM...JOHNSON LONG TERM...HEAVENER AVIATION...HEAVENER/JOHNSON MARINE...HEAVENER/JOHNSON

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