Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 241339 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 939 AM EDT SUN AUG 24 2014 .SYNOPSIS... HIGH PRESSURE WILL CONTINUE TO BUILD INTO THE REGION TODAY, THEN REMAIN IN CONTROL OF THE WEATHER THROUGH TUESDAY. THE HIGH WILL RETREAT SOUTH BY WEDNESDAY AS A FRONTAL BOUNDARY APPROACHES FROM THE NORTH LATE WEDNESDAY INTO THURSDAY. THE FRONT MAY STALL NEAR OR JUST SOUTH OF THE AREA FRIDAY INTO SATURDAY AS HIGH PRESSURE MOVES ACROSS THE NORTHEAST. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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AN UPPER AIR ANALYSIS SHOWED A TROUGH AXIS NOW TO OUR SOUTHEAST, WITH A RIDGE EXTENDING FROM THE SOUTHERN STATES TO THE GREAT LAKES THEN INTO CANADA. AT THE SURFACE, HIGH PRESSURE CENTERED FROM NEAR JAMES BAY TO NORTHERN NEW YORK IS THEN WEDGING DOWN INTO THE MID ATLANTIC. THE 12Z RAOBS FROM STERLING, VA AND UPTON, NY INDICATE THAT THE AIRMASS HAS DRIED FROM YESTERDAY. HOWEVER, SOME LOW-LEVEL MOISTURE REMAINS SO FAR BELOW 700/800 MB WHERE SOME CAPPING IS ALSO EVIDENT. GIVEN THE CENTER OF SURFACE HIGH PRESSURE TO OUR NORTH, AN ONSHORE FLOW WILL BE MAINTAINED. BASED ON THE SOUNDINGS, SOME ADDITIONAL CUMULUS SHOULD DEVELOP WITH HEATING DUE TO JUST ENOUGH LOW-LEVEL MOISTURE REMAINING. THEREFORE, WE INCREASED THE CLOUD COVER A BIT MORE HOWEVER IT WILL PROBABLY NOT IMPACT THE WORDING. THE DEW POINTS IN GENERAL SHOULD LOWER SOME THROUGH THE DAY WITH MIXING. OVERALL, MUCH MORE SUNSHINE IS EXPECTED COMPARED TO YESTERDAY AND WITH THE TROUGH AXIS NOW TO OUR SOUTHEAST SOME MODERATION IN THE AIRMASS IS EXPECTED. IT WILL STILL BE A BIT COOLER THOUGH CLOSER TO THE COAST DUE TO THE ONSHORE FLOW. THE HOURLY GRIDS WERE TWEAKED BASED ON THE LATEST OBSERVATIONS, AND THEN THE LAMP/LAV GUIDANCE WAS USED TO ASSIST THROUGH THE AFTERNOON. THIS INCLUDED RAISING THE DEW POINTS SOME FOR THE NEXT FEW HOURS. IN ADDITION, THE WINDS WERE INCREASED SOME MAINLY ALONG THE COASTAL AREAS. NO MAJOR CHANGES WERE MADE TO THE HIGH TEMPERATURES ATTM.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
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A SHORT WAVE UPPER LEVEL TROUGH SLIDES SOUTHEAST APPROACHING THE REGION, RESULTING IN CLEARING SKIES. WITH CONTINUED ONSHORE FLOW THERE IS A SMALL RISK THAT PATCHY FOG COULD DEVELOP ONCE AGAIN. HOWEVER GIVEN THE DRY AIR ADVECTION THROUGH THE DAY, THINK IT IS UNLIKELY.
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&& .LONG TERM /MONDAY THROUGH SATURDAY/... HIGH PRESSURE WILL REMAIN IN CONTROL OF THE WEATHER MONDAY AND TUESDAY, WHICH WILL KEEP FAIR CONDITIONS ACROSS THE AREA. TEMPERATURES WILL BE ON THE RISE AS RIDGING ALOFT NOSES IN FROM SOUTHWEST. THE HIGH IS EXPECTED TO RETREAT SOUTHWARD WEDNESDAY AS A FRONTAL BOUNDARY APPROACHES THE AREA FROM THE NORTH. THERE ARE NOT ANY STRONG SHORT WAVE/VORTICITY IMPULSES FORECAST WITH THE FRONT, AND THERE IS NOT A LOT OF MOISTURE FORECAST AHEAD OF THE FRONT. THEREFORE THE FORECAST FOR THE DAY WEDNESDAY IS DRY. HOWEVER, AS THE FRONT SAGS SOUTHWARD WEDNESDAY NIGHT INTO THURSDAY, THERE COULD BE SOME ISOLATED SHOWERS DEVELOP, ESPECIALLY IF THE SHORT WAVE THE ECMWF IS FORECASTING OCCURS. TEMPERATURES ARE EXPECTED TO REMAIN ABOVE NORMAL WEDNESDAY AND THURSDAY AS WE REMAIN ON THE NORTHERN EDGE OF THE RIDGE ALOFT. THE FORECAST THEN BECOMES MORE UNCERTAIN AFTER THIS. THE GFS STALLS THE FRONT NEAR THE AREA OR JUST TO OUR SOUTH FRIDAY, BEFORE LIFTING BACK NORTHWARD AS LOW PRESSURE DEVELOPS WEST OF THE AREA AND MOVES TO OUR NORTHWEST. THE ECMWF PUSHES THE FRONT THROUGH THE AREA, THEN PUSHES HIGH PRESSURE ACROSS THE AREA THROUGH SATURDAY. WITH THE UNCERTAINTY IN THE MODELS, AND THE POSSIBILITY FOR RAIN CHANCES, WE WILL KEEP A CHANCE OF SHOWERS AND THUNDERSTORM INTO THE WEEKEND. THE MODELS CONTINUE TO SHOW THE POTENTIAL TROPICAL SYSTEM REMAINING WELL OFFSHORE LATE IN THE WEEK, SO FOR NOW WE DO NOT EXPECT ANY EFFECTS FROM THE STORM EXCEPT AN INCREASE IN SWELLS AND RIP CURRENTS ON THE COAST. && .AVIATION /14Z SUNDAY THROUGH THURSDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REST OF TODAY...VFR WITH CLOUD BASES MAINLY AT OR ABOVE 4000 FEET. NORTH AND NORTHEAST WINDS 5-10 KNOTS, TURNING EAST OR LOCALLY SOUTHEAST TOWARD EVENING. SOME GUSTINESS IS POSSIBLE MAINLY AT KACY AND KMIV. TONIGHT...VFR OVERALL WITH ANY CLOUDS THINNING. AFTER 06Z, THERE COULD BE SOME LOCALIZED FOG DEVELOPMENT HOWEVER GIVEN THAT SLIGHTLY DRIER AIR SHOULD BE IN PLACE OUR CONFIDENCE IN ANY FOG DEVELOPMENT IS LOW. EAST-SOUTHEAST WINDS TURNING NORTHEAST AT LESS THAN 5 KNOTS. OUTLOOK... MONDAY-WEDNESDAY NIGHT...MOSTLY VFR. ONLY EXCEPTION WOULD BE POSSIBLE FOG TUESDAY NIGHT-WEDNESDAY MORNING. THURSDAY... MOSTLY VFR. CHANCE OF SHOWERS.
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&& .MARINE...
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HIGH PRESSURE BUILDS DOWN FROM THE NORTH THROUGH TONIGHT. A LINGERING ONSHORE FLOW HOWEVER WILL KEEP SEAS UP AROUND 5 FEET ACROSS THE SOUTHERN OCEAN ZONES DUE TO A BETTER FETCH. FARTHER NORTH, THERE IS RATHER LIMITED BUOY DATA /SEAS AT BUOY 44017 HAVE BEEN BELOW 5 FEET FOR SEVERAL HOURS/ AND THEREFORE WE ARE ASSUMING SEAS WILL REMAIN UNDER ADVISORY CRITERIA HERE. THE WINDS ARE ANTICIPATED TO BE BELOW 25 KNOTS FOR THE NORTHERN ZONES AND DELAWARE BAY. OTHERWISE, THE REMAINING ADVISORY CONTINUES THROUGH 22Z TODAY. ONCE SEAS DO DROP BELOW 5 FEET, CONDITIONS SHOULD STAY BELOW SMALL CRAFT ADVISORY CRITERIA THROUGH OVERNIGHT. OUTLOOK... MONDAY-WEDNESDAY NIGHT...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED WITH HIGH PRESSURE ACROSS THE WATERS. THURSDAY...INCREASING LONG PERIOD SWELLS POSSIBLE ASSOCIATED WITH POSSIBLE TOPICAL SYSTEM WELL TO THE EAST OVER THE ATLANTIC.
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&& .RIP CURRENTS...
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THERE IS A MODERATE RISK OF RIP CURRENTS TODAY FOR THE DELAWARE BEACHES AND THE NEW JERSEY SHORE. WITH THE TROPICAL SYSTEM EXPECTED TO LIFT NORTHEAST /STAYING WELL OFFSHORE/, LONGER PERIOD SWELLS COULD LEAD TO AN ENHANCED RIP CURRENT RISK LATER THIS WEEK.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ452>455. && $$ SYNOPSIS...ROBERTSON NEAR TERM...GORSE SHORT TERM...JOHNSON LONG TERM...ROBERTSON AVIATION...GORSE/ROBERTSON MARINE...GORSE/ROBERTSON RIP CURRENTS...JOHNSON

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