Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000 FXUS61 KPHI 212058 AFDPHI AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE MOUNT HOLLY NJ 358 PM EST FRI NOV 21 2014 .SYNOPSIS...
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STRONG HIGH PRESSURE WILL BUILD ACROSS THE MID ATLANTIC STATES TONIGHT AND SATURDAY, BEFORE MOVING OFFSHORE LATER SATURDAY NIGHT. A WARM FRONT WILL LIFT NORTH ACROSS THE REGION SUNDAY NIGHT INTO MONDAY AS STRONG LOW PRESSURE ADVANCES INTO THE GREAT LAKES. THIS LOW PRESSURE WILL TRACK INTO EASTERN CANADA AS ITS COLD FRONT CROSSES OUR REGION MONDAY NIGHT TO EARLY TUESDAY. HIGH PRESSURE WILL BUILD TO OUR SOUTH LATER TUESDAY THROUGH WEDNESDAY, FOLLOWED BY POSSIBLE LOW PRESSURE DEVELOPING AROUND THE GREAT LAKES THURSDAY. HIGH PRESSURE FROM THE MIDWEST SHOULD BUILD INTO THE AREA FRIDAY.
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&& .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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AS OF MID AFTERNOON SFC HIGH PRES WAS CENTERED OVER THE MID OH VLY AND WAS CONTG TO MOVE EWD INTO THE MID-ATL REGION. GUSTY NW WINDS AROUND THE HIGH CONT OVER THE FCST AREA BUT SHOULD GRADLY DIMINISH FOR THE REST OF THE AFTN AS THE PRES GRADIENT RELAXES. AFTN TEMPS MAINLY IN THE LOW TO MID 30S ARE ABOUT 15 DEGS F COOLER THAN NORMAL FOR THIS TIME OF YEAR. THIS IS IN SPITE OF SUNNY SKIES MOST AREAS... EXCEPT FOR SOME LOW CLOUD STREAMERS OVER NE PA AND NW NJ CARRYING MOISTURE FROM THE LOWER GRTLKS. FOR TONIGHT...THE HIGH PRES WILL MOVE OVER OUR AREA RESULTING IN FURTHER DIMINISHING WINDS. THE LIGHT OR NEAR CALM WINDS PLUS A DRY ATMOS WILL ALLOW FOR PLENTY OF RADIATIONAL COOLING OVERNIGHT. WARMER AIR WILL BE MOVING IN ALOFT FROM THE WEST BUT THIS WILL ONLY ENHANCE THE LOW LEVEL INVERSION AND FURTHER DE-COUPLING OF THE SURFACE LAYER. DECIDED TO UNDERCUT MOS GUIDANCE BY A DEGREE OR TWO. THE OVERNIGHT MIN TEMPS MAY APPROACH RECORDS FOR THE DATE FOR SOME LOCATIONS. HWVR URBAN AND COASTAL AREAS SHOULD NOT BE QUITE AS COLD.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
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HIGH PRES WILL CONT TO SHIFT EWD OR SEWD AND SHOULD BE CENTERED OFF OF CAPE HAT BY LATE IN THE DAY. THIS WILL RESULT IN SWLY FLOW AND SMWHT OF A MODERATING TREND IN TEMPS. WITH WARM ADVECTION CONTINUING ALOFT...AFTN MAXS SHOULD BE 5 TO 10 DEGREES WARMER THAN TODAY BUT STILL BELOW NORMAL. INCREASING HI CLOUDS WILL TEND TO HOLD TEMPS BACK ESPECIALLY N/W OF PHL. NO PRECIP IS EXPECTED BEFORE 00Z SUNDAY.
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&& .LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
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A CHANGING PATTERN AND NOTICEABLY MILDER AIRMASS ARE IN STORE AT THE BEGINNING OF THE LONG TERM PERIOD, BUT A RETURN TO COOLER AND BELOW AVERAGE TEMPERATURES LOOKS TO FOLLOW FOR THE MIDDLE OF NEXT WEEK. AFTER A FAIRLY QUIET DAYTIME SATURDAY, THE DEVELOPING RETURN FLOW AROUND HIGH PRESSURE AS IT GRADUALLY MOVES OFFSHORE INTO SATURDAY NIGHT WILL ALLOW FOR SOME LOWER LEVEL MOISTURE TO RETURN BACK IN ACROSS THE REGION. LOOKING AT FORECAST SOUNDINGS ALOFT THROUGH ABOUT 850MB, SOME WARM AIR ADVECTION WILL BE TAKING PLACE THROUGH THE 0Z TO 12Z SUNDAY TIMEFRAME. THESE SIGNALS LOOK TO INITIATE SOME LIGHT PRECIP OFF OF THE GREAT LAKES, ESPECIALLY TO OUR NORTHWEST, FROM LATE-DAY SATURDAY AND INTO SATURDAY NIGHT. FOR OUR REGION, THERE LOOKS TO BE ENOUGH LIFT ALOFT TO PERHAPS SUPPORT SOME LIGHT PRECIP REACHING OUR FAR NORTHERN ZONES, AND IF THIS WERE TO OCCUR INTO SATURDAY NIGHT, IT MAY RESULT IN SOME LIGHT FREEZING RAIN AS SURFACE TEMPS WILL BE BELOW FREEZING AS THE WARMING ALOFT OCCURS. THIS STILL LOOKS TO BE A LOW PROBABILITY EVENT, WITH PERHAPS THE SHELTERED VALLEYS HAVING THE BEST CHANCE FOR A LITTLE FREEZING RAIN AS THE COLD SURFACE AIR REMAINS TRAPPED. NONETHELESS, WITH OUR CONFIDENCE IN THIS OCCURRENCE BELOW AVERAGE, WE HAVE KEPT POPS AT 30 PERCENT OR LESS. WE WILL, HOWEVER, KEEP A MENTION OF THIS POSSIBILITY IN THE HAZARDOUS WEATHER OUTLOOK PRODUCT. GOING INTO SUNDAY AND SUNDAY NIGHT, WAA AND MOISTURE ADVECTION WILL BE TAKING SHAPE IN EARNEST ACROSS OUR REGION BEHIND THE OFFSHORE HIGH PRESSURE. AT THE SURFACE, A WARM FRONT WILL BE APPROACHING OUR REGION FROM THE SOUTHWEST AS STRONG SURFACE LOW PRESSURE TRACKS INTO THE GREAT LAKES. HIGHEST POPS FOR RAIN ARE KEPT THROUGH THE SUNDAY NIGHT TO EARLY MONDAY TIMEFRAME, WITH THE BEST LIFT OCCURRING AND THE WARM FRONT PROGRESSING NORTH THROUGH THE REGION. HOWEVER, SOME HIGH CHANCE POPS ARE IN PLACE FOR LATE-DAY SUNDAY FOR OUR SOUTHERN AND WESTERN ZONES. INTO MONDAY, WITH THE WARM FRONT NORTH OF OUR AREA, WE TRIM BACK POPS FOR ONLY SOME SCATTERED SHOWERS. MONDAY LOOKS TO BE THE WARMEST DAY OF THE LONG TERM AS WAA AND A SOUTH-SOUTHWEST FLOW CONTINUE ACROSS THE REGION. DEPENDING ON CLOUD COVER, ANY SHOWER ACTIVITY, AND DECENT MIXING, MAXIMUM TEMPERATURES ARE EXPECTED TO EASILY REACH INTO THE MIDDLE AND UPPER 60S FOR MUCH OF THE FORECAST AREA, WITH SOME AREAS HAVING A CHANCE AT REACHING AROUND 70 DEGREES. THIS WOULD BE NEARING RECORD HIGH TERRITORY. LATER MONDAY NIGHT INTO EARLY TUESDAY, THE GFS AND ECMWF SHOW STRONG SURFACE LOW PRESSURE TRACKING INTO EASTERN CANADA, WITH ITS ASSOCIATED COLD FRONT CROSSING OUR REGION. THIS COLD FRONT MAY TAKE ITS TIME MOVING FARTHER OFFSHORE AND AWAY FROM THE EASTERN SEABOARD THROUGH TUESDAY AND WEDNESDAY AS THE GFS AND ECMWF SHOW THE UPPER TROUGH REMAINING OFF TO OUR WEST. IN FACT, THE GUIDANCE CONTINUES TO SHOW POTENTIAL LOW PRESSURE DEVELOPMENT ALONG THIS LINGERING BOUNDARY OFF OF THE SOUTHEAST UNITED STATES COAST AS SOME ENERGY EMERGES THROUGH THE BASE OF THE UPPER TROUGH. WHILE ANY PRECIP CHANCES SHOULD BE FAIRLY LIMITED TUESDAY INTO WEDNESDAY, IT WILL DEPEND ON THE PROXIMITY OF THIS LOW PRESSURE TO THE EASTERN SEABOARD AS IT ADVANCES NORTHEAST ALONG THE LINGERING BOUNDARY. FOR NOW, WE HAVE KEPT SOME CHANCE POPS FOR RAIN/SHWRS INTO WEDNESDAY, ESPECIALLY FOR OUR EASTERN ZONES. IN ADDITION TO ANY POSSIBLE PRECIP CHANCES, COLD AIR ADVECTION WILL BE TAKING SHAPE THROUGH MIDWEEK, WITH A RETURN TO BELOW AVERAGE TEMPERATURES BY WEDNESDAY. WHILE THERE IS A LITTLE MORE UNCERTAINTY TOWARD THE END OF THE LONG TERM PERIOD, THERE ARE MORE SIMILARITIES WITH THE GFS AND ECMWF RUNS AS COMPARED TO PREVIOUS RUNS WITH REGARDS TO A MUCH STRONGER MID/UPPER TROUGH DIGGING DOWN FROM THE GREAT LAKES AND TOWARD OUR REGION THURSDAY. AT THIS TIME, WE WENT PRIMARILY WITH A WPC/CONTINUITY BLEND WITH REGARDS TO TEMPS AND POPS THURSDAY. AS THIS TROUGH MOVES OFFSHORE INTO FRIDAY MORNING, SURFACE HIGH PRESSURE FROM THE MIDWEST LOOKS TO TAKE ITS PLACE AND BUILD EAST TOWARD OUR REGION.
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&& .AVIATION /21Z FRIDAY THROUGH WEDNESDAY/...
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THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, KMIV, KACY AND SURROUNDING AREAS. VFR CONDS ARE EXPECTED TO CONTINUE FOR AT LEAST THE NEXT 24 HOURS FOR ALL TAF SITES. THE CURRENT GUSTY NW WINDS ARE SLOWLY DIMINISHING AS OF MID AFTN AND WILL DECREASE MORE RAPIDLY AFTER SUNSET. LIGHT WESTERLY OR VARIABLE WINDS SHOULD PREVAIL OVERNIGHT. AS HIGH PRES MOVES OFFSHORE ON SATURDAY...SWLY WINDS WILL DEVELOP BY MID/LATE MORNING BUT SHOULD GENLY REMAIN BELOW 10 KT DURG THE DAY. OUTLOOK... SATURDAY NIGHT THROUGH SUNDAY...VFR CONDITIONS; ALTHOUGH, INCREASING CLOUDINESS IS EXPECTED SUNDAY. SUNDAY NIGHT THROUGH MONDAY NIGHT...CEILING AND VSBY RESTRICTIONS ARE EXPECTED IN AREAS OF RAIN. TUESDAY...MAINLY VFR CONDITIONS. WEDNESDAY...POSSIBLE SUB-VFR DEPENDING ON THE TRACK OF OFFSHORE LOW PRESSURE. LOW CONFIDENCE.
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&& .MARINE...
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SEAS ARE DECREASING WITH BUOY 44009 AROUND 4 FT AT 20Z AND 44065 BELOW 3 FT. WINDS ARE ALSO DECREASING BUT SOME GUST BETWEEN 25 AND 30 KT ARE STILL BEING REPORTED. THE CURRENT SCA FOR ALL FORECAST WATERS IS SET TO EXPIRE AT AT 600 PM WHICH LOOKS GOOD AT THIS POINT. WINDS OVER THE DELAWARE BAY MIGHT DECREASE A LITTLE FASTER. WINDS OVERNIGHT AND SATURDAY WILL BACK AROUND TO THE WEST AND THEN SW BUT SHOULD REMAIN BELOW SCA LEVEL. OUTLOOK... SATURDAY NIGHT...CONDITIONS MAY BE CLOSE TO SCA CRITERIA FOR OUR COASTAL WATERS, WITH SOME WIND GUSTS BETWEEN 20 TO 25 KNOTS. SUNDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED, WITH WIND GUSTS TO AROUND 20 KNOTS OR LESS FOR THE COASTAL WATERS. SUNDAY NIGHT THROUGH MONDAY NIGHT...SCA CONDITIONS ARE EXPECTED AT THIS TIME FOR THE COASTAL WATERS AND INTO DELAWARE BAY, WITH WIND GUSTS AS HIGH AS 30 KNOTS PLUS AT TIMES ALONG WITH ELEVATED SEAS. TUESDAY...SOME LINGERING SCA CONDITIONS ON THE COASTAL WATERS DUE TO ELEVATED SEAS. WEDNESDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED.
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&& .PHI WATCHES/WARNINGS/ADVISORIES... PA...NONE. NJ...NONE. DE...NONE. MD...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ430- 431-450>455. && $$ SYNOPSIS...KLINE NEAR TERM...AMC SHORT TERM...AMC LONG TERM...KLINE AVIATION...AMC/KLINE MARINE...AMC/KLINE

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