Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 251331 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 931 AM EDT MON AUG 25 2014 .SYNOPSIS...
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HIGH PRESSURE WILL REMAIN IN CONTROL OF OUR WEATHER THROUGH TUESDAY. A COLD FRONT SHOULD SLIDE SOUTHEASTWARD INTO THE MID ATLANTIC REGION DURING MID WEEK. IN THE WAKE OF THE COLD FRONT, HIGH PRESSURE BUILDS IN DURING THURSDAY AND FRIDAY. A WARM FRONT MAY LIFT NORTHWARD NEAR OUR AREA SATURDAY, THEN A COLD FRONT APPROACHES SUNDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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THE SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL RIDGE THAT CONTINUES TO BUILD INTO THE NORTHEAST AND MID ATLANTIC REGION. SINCE WE ARE NEAR THE EASTERN EDGE OF THIS RIDGE, THE FLOW UP THROUGH ABOUT 500 MB IS STILL ONSHORE. IN ADDITION, SURFACE HIGH PRESSURE CENTERED NEAR NORTHERN NEW YORK STATE WILL CONTINUE TO WEDGE DOWN INTO THE MID ATLANTIC REGION. DESPITE THE ONSHORE FLOW, THE AIRMASS HAS DRIED SOME MORE SINCE YESTERDAY ESPECIALLY JUST ABOVE THE SURFACE. THIS IS EVIDENT IN THE 12Z RAOBS FROM STERLING, VA AND UPTON, NY. WHILE SOME CUMULUS SHOULD OCCUR ESPECIALLY INLAND WITH A NARROW MOIST LAYER NEAR 850 MB, IT SHOULD BE LESS THAN YESTERDAY GIVEN SOME WARMING ALOFT AND SOME INCREASE IN SUBSIDENCE. SOME THIN HIGH CLOUDS SHOULD BE AROUND AT TIMES ESPECIALLY ACROSS THE WESTERN ZONES. A NORTHEASTERLY LOW-LEVEL FLOW SHOULD TURN MORE EAST AND THEN SOUTH-SOUTHEAST GIVEN THE WEAKER PRESSURE GRADIENT AND FLOW. THE DELMARVA HOWEVER MAY HOLD ONTO A NORTHEAST OR EAST FLOW LONGER. THIS TRANSLATES TO PROBABLY SOME ENHANCEMENT OF A SEA/BAY BREEZE AS THE LAND HEATS UP. IT SHOULD BE COOLER CLOSER TO THE COAST AND ALSO THE DELMARVA GIVEN THE LINGERING EFFECTS OF THE OCEAN INFLUENCE. THE DEW POINTS IN GENERAL ARE ANTICIPATED TO BE IN THE COMFORTABLE RANGE TODAY, WITH SOME DECREASE PROBABLY OCCURRING WITH HEATING/MIXING. THE HOURLY GRIDS WERE ADJUSTED BASED ON THE LATEST OBSERVATIONS, THEN THE LAMP/LAV GUIDANCE WAS BLENDED IN TO ASSIST ESPECIALLY WITH TEMPERATURES AND DEW POINTS. NO MAJOR CHANGES WERE MADE TO THE HIGH TEMPERATURES, WHICH WERE MOSTLY A NAM/GFS MOS BLEND.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/... THE AFOREMENTIONED HIGH WILL REMAIN PARKED OVER THE AREA SO A CLEAR SKY, AND DRY CONDS ARE ANTICIPATED. AGAIN, MOS GUID WAS IN GOOD AGREEMENT AND GENLY FOLLOWED. && .LONG TERM /TUESDAY THROUGH SUNDAY/... CONSIDERABLY DIFFERENT MODEL SOLUTIONS FROM BOTH THE GFS AND ECMWF THAN THE MODEL RUNS 24 HOURS AGO. TUESDAY...START TO SEE SOUTHWESTERLY FLOW DEVELOP IN THE LOW LEVELS AT THE SAME TIME AN UPPER LEVEL SHORT WAVE RIDGE PIVOTS SOUTHEAST OVER THE REGION EARLY IN THE DAY. THE COMBINATION OF BOTH OF THESE WILL RESULT IN RATHER PRONOUNCED WARM UP FOR TUESDAY. HIGHS COULD BE AS MUCH AS 5 DEGREES ABOVE NORMAL. WEDNESDAY AND THURSDAY...THE BIGGEST CHANGE IN THE LATEST LONG RANGE MODEL RUNS IS WITH THE TIMING OF THE COLD FRONT. WHILE THERE HAD BEEN A TREND UP THROUGH YESTERDAY`S 00Z MODEL RUNS OF DELAYING THE ARRIVAL OF THE COLD FRONT (OR NOT EVEN BRINGING IT THIS FAR SOUTH AT ALL), THE 12Z RUNS, AND NOW THE LATEST 00Z RUNS HAVE SPED UP THE ARRIVAL OF THE FRONT. SHOWING THE FRONT ARRIVING IN OUR REGION ON WEDNESDAY OR WEDNESDAY NIGHT. INTERESTINGLY, TO START THIS PERIOD, MID AND UPPER LEVEL FLOW IS NEARLY ZONAL (SUGGESTING THAT THE FRONT MAY NOT DIG AS FAR SOUTH). HOWEVER, BOTH THE GFS AND ECMWF SHOW AN UPPER LEVEL SHORT WAVE TROUGH QUICKLY DIGGING SOUTHEAST OUT OF NORTH CENTRAL CANADA, CROSSING THE NORTHEASTERN U.S. BY WEDNESDAY NIGHT. THERE WILL BE SOME CHANCE OF THUNDERSTORMS ALONG THE FRONT, THOUGH WITH DRIER SOUTHWESTERLY FLOW IN THE PERIODS LEADING UP TO THIS, THERE IS SOME QUESTION OF MOISTURE AVAILABILITY, AND THUS HOW WIDESPREAD PRECIPITATION WILL BE. THE LIMITED LOW LEVEL MOISTURE ALSO HAS AN IMPACT ON INSTABILITY, AS DOES THE EXPECTED NIGHT TIME ARRIVAL OF THE FRONT. THUS...AT THIS TIME SEVERE STORMS SEEM UNLIKELY, BUT IF THE FRONT ARRIVES DURING DAY LIGHT HOURS, NOT COMPLETELY OUT OF THE QUESTION. ON A SIDE NOTE FOR THIS PERIOD, CRISTOBAL IS STILL EXPECTED TO BE WELL OUT TO SEA, AND BY THIS POINT RACING FURTHER AWAY FROM THE REGION. THUS, THE ONLY IMPACTS WE ARE EXPECTING FROM CRISTOBAL ARE LONG PERIOD SWELLS AND AN ENHANCED RIP CURRENT RISK, THOUGH THE TIMING OF BOTH IS UNCERTAIN. FRIDAY...THE CONTINENTAL POLAR AIR MASS SETTLES IN OVER THE REGION, ALBEIT BRIEFLY, BY FRIDAY, LEADING TO A COOL AND DRY DAY. FRIDAY NIGHT THROUGH SUNDAY...AS THE HIGH SHIFTS NORTHEAST OFF THE COAST, LOW LEVEL SOUTHERLY FLOW RETURNS BRINGING A WARMING TREND, AND MORE MOISTURE. THIS COULD SET THE STAGE FOR THE BEST CHANCE OF THUNDERSTORMS OVER THE NEXT WEEK EITHER SATURDAY OR SUNDAY AS A SECOND COLD FRONT COULD APPROACH THE REGION. && .AVIATION /14Z MONDAY THROUGH FRIDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. REST OF TODAY...VFR. NORTHEAST WINDS 5-8 KNOTS, MOSTLY BECOMING EAST AND THEN SOUTHERLY THIS AFTERNOON. TONIGHT...VFR OVERALL. LOCALIZED FOG MAY OCCUR TOWARD MORNING, HOWEVER IT MAY BE SHALLOW GROUND FOG. OUR CONFIDENCE IS LOW THAT IT WOULD HAVE AN IMPACT ON ANY TERMINALS, THEREFORE IT WAS NOT INCLUDED AT THIS TIME. SOUTHERLY WINDS AROUND 5 KNOTS, BECOMING LIGHT AND VARIABLE OR CALM. TUESDAY...VFR. LIGHT AND VARIABLE WINDS TO START, BECOMING SOUTHWESTERLY 5-8 KNOTS. A SEA/BAY BREEZE IN THE AFTERNOON MAY AFFECT KACY, KMIV AND KILG WITH MORE OF A SOUTHEAST WIND. OUTLOOK... TUESDAY NIGHT...VFR CONDITIONS EXPECTED. WEDNESDAY THROUGH THURSDAY...MOSTLY VFR CONDITIONS EXPECTED. A SMALL RISK OF THUNDERSTORMS AS A COLD FRONT COULD PUSH THROUGH WEDNESDAY OR THURSDAY. FRIDAY...VFR CONDITIONS LIKELY.
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&& .MARINE... THE SCA WILL REMAIN IN EFFECT AS PREV ISSUED MAINLY FOR SEAS DUE TO THE NELY FLOW. THE FLOW SHOULD EVENTUALLY BECOME MORE SLY THEN SWLY AND THIS SHOULD ALLOW THE SEAS TO SLOWLY SUBSIDE, AFTER WHICH TIME NO ADDITIONAL MARINE HEADLINES WILL BE NECESSARY FOR THE REMAINDER OF THE NEAR AND SHORT TERM PDS. OUTLOOK... TUESDAY...WINDS AND SEAS ARE EXPECTED TO BE BELOW SMALL CRAFT ADVISORY CRITERIA. WEDNESDAY THROUGH FRIDAY...WINDS WILL STAY BELOW SCA CRITERIA. WE COULD BEGIN TO SEE LONG PERIOD SWELLS ASSOCIATED WITH TROPICAL CYCLONE CRISTOBAL, WHICH WILL STAY WELL OUT TO SEA, AS EARLY AS WEDNESDAY. HOWEVER, TIMING AS WELL AS WAVE HEIGHTS ASSOCIATED WITH THESE SWELLS IS STILL VERY UNCERTAIN AT THIS TIME. && .RIP CURRENTS...
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THE RISK OF DANGEROUS RIP CURRENTS IS HIGH THROUGH THIS EVENING. THE COMBINATION OF TODAY`S NEW MOON, LONG FETCH ONSHORE FLOW EARLY AND THEN LONG PERIOD SWELLS ASSOCIATED WITH TROPICAL STORM CRISTOBAL LATER IN THE WEEK SHOULD KEEP AN ELEVATED RISK OF DANGEROUS RIP CURRENTS. TROPICAL STORM CRISTOBAL IS FORECAST TO TRACK WELL EAST OF THE MID ATLANTIC COAST LATER THIS WEEK.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...HIGH RIP CURRENT RISK THROUGH THIS EVENING FOR NJZ014-024>026. DE...HIGH RIP CURRENT RISK THROUGH THIS EVENING FOR DEZ004. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ452>455. && $$ SYNOPSIS...GORSE/JOHNSON NEAR TERM...GORSE SHORT TERM...NIERENBERG LONG TERM...JOHNSON AVIATION...GORSE/JOHNSON MARINE...JOHNSON/NIERENBERG RIP CURRENTS...JOHNSON/NIERENBERG

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