Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 191957
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
357 PM EDT SUN OCT 19 2014

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFFSHORE TO OUR SOUTH TONIGHT. ON MONDAY A
LOW PRESSURE SYSTEM WITH AN ASSOCIATED COLD FRONT WILL DIVE
SOUTHEAST FROM THE UPPER GREAT LAKES REACHING OUR REGION DURING THE
DAY TUESDAY. ANOTHER LOW PRESSURE WILL FORM OFF THE CAROLINA
COASTLINE ON TUESDAY AS WELL. THESE TWO LOW PRESSURE SYSTEMS WILL
INTERACT WITH EACH OTHER AND MERGE JUST OFFSHORE WEDNESDAY AND
THURSDAY. THE LOW PRESSURE SYSTEM WILL DEPART THE REGION BY FRIDAY
WITH HIGH PRESSURE MOVING IN FROM THE WEST BY SATURDAY. THIS WILL BE
FOLLOWED BY A COLD FRONTAL PASSAGE SATURDAY NIGHT. ANOTHER AREA OF
HIGH PRESSURE MOVES IN FROM THE WEST ON SUNDAY.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...
CONTINUED GUSTY NORTHWEST WINDS WILL BEGIN TO DIMINISH BY LATER THIS
EVENING AS WE LOSE ANY SURFACE HEATING AND THE SURFACE PRESSURE
GRADIENT RELAXES. THE CENTER OF THE HIGH PRESSURE SHOULD BE DIRECTLY
OVERHEAD LATE TONIGHT WITH LIGHT AND VARIABLE OR CALM WINDS
EXPECTED. DEWPOINTS WILL HOVER IN THE UPPER-20S TO LOW-30S MOST OF
THE NIGHT TEMPERATURES WILL DROP AS WELL UNDER THE GOOD RADIATIONAL
COOLING CONDITIONS.

THE FREEZE WARNING AND FROST ADVISORY LOCATIONS AND TIMING REMAINS
UNCHANGED. THE BIGGEST FLY IN THE OINTMENT WILL BE HOW FAST
TEMPERATURES DROP WITH THE DECOUPLING BEFORE SOME JET CIRRUS ADVECTS
IN FROM THE WEST. LOOKING UPSTREAM AT THE CIRRUS IT DOES NOT APPEAR
TO VERY THICK AND THE MODEL RH VALUES FROM 1000 TO 500MB ARE RATHER
VANILLA SO WE SHOULD STILL BE ABLE TO COOL A BIT OR LEVEL OFF ONCE
THE CLOUDS ROLL IN.

TEMPERATURES TONIGHT WERE A BLEND OF THE MET/MAVMOS WITH A HEAVIER
WEIGHTING ON THE SLIGHTLY COOLER MET. THE NAM OVERALL APPEARED TO
INITIALIZE BETTER THAN THE GFS UPSTREAM.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH 6 PM MONDAY/...
NOT MUCH IN THE WAY OF SENSIBLE WEATHER CHANGE OTHER THAN WE SHOULD
BE ABLE TO TACK ON A FEW DEGREES TO DAYTIME HIGHS. WINDS BACK
TOWARDS THE SOUTH-SOUTHWEST BY LATE MORNING AS HIGH PRESSURE MOVES
OFFSHORE TO OUR SOUTHEAST. DEWPOINTS WILL BEGIN TO CREEP UP THOUGH
NOT ENOUGH TO ALLOW FOR COLUMN SATURATION. WE KEEP MONDAY DRY AHEAD
OF THE NEXT UPPER LEVEL WAVE RIPPLING ACROSS THE OHIO VALLEY.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
MONDAY NIGHT: CLOUDS AND WAA BEGIN TO INCREASE AHEAD OF THE NEXT
COLD FRONTAL SYSTEM. ENOUGH LIFT SHOULD BE PRESENT TO GENERATE SOME
SCATTERED SHOWERS ACROSS WESTERN PARTS OF THE CWA BY SUNRISE TUESDAY
WITH QPF UNDER 1/10TH OF AN INCH. MAV AND MET GUIDANCE SETS USED FOR
MOST WEATHER ELEMENTS IN THIS PERIOD.

TUESDAY THROUGH THURSDAY NIGHT: A COASTAL LOW PRESSURE SYSTEM WILL
DEVELOP OFFSHORE AND BE SLOW TO MOVE NORTHEAST THROUGHOUT THIS
PERIOD. THE END RESULT WILL BE GRAY GLOOMY COOLER DAYS FEATURING
RAIN SHOWERS AND SOME BRISK NORTHWESTERLY WINDS WEDNESDAY AND
THURSDAY AFTERNOONS. THE FORMATION OF THIS LOW PRESSURE WILL START
WITH TWO PIECES, A STRONG UPPER LEVEL LOW AND COLD FRONT DIVING FROM
THE GREAT LAKES INTO THE MID-ATLANTIC AND A LOW PRESSURE FORMING OFF
THE CAROLINA`S. THE UPPER LOW AND COLD FRONTAL BOUNDARY WILL LEAD TO
CONTINUED SCATTERED SHOWERS ON TUESDAY TO THE REGION WITH A MOISTURE
PLUME FROM THE CAROLINA LOW WELL OFFSHORE. BY TUESDAY NIGHT WE BEGIN
TO SEE MORE INTERACTION BETWEEN THE FEATURES, PHASING. A PHASED LOW
FORMS OFF THE SOUTHERN NEW ENGLAND COASTLINE BY WEDNESDAY WITH THE
MAJORITY OF ATLANTIC MOISTURE BROUGHT INTO SOUTHERN NEW ENGLAND. TO
COMPARE OUR REGION WOULD BE FAVORED FOR JUST SOME WRAP AROUND
SHOWERS.

OVERALL THE OPERATIONAL MODELS HAVE COME INTO BETTER CONSENSUS TODAY
THAT THE ABOVE OUTCOME WILL OCCUR. THIS IS REFLECTED IN BOTH THE 00Z
ECMWF ENSEMBLE MEAN COMPARED TO THE OPERATIONAL RUN AND THE 06Z
GEFS. WITH THAT BEING SAID, CONFIDENCE CONTINUES TO INCREASE THAT
THIS PERIOD WILL BE DOMINATED BY SOME SCATTERED SHOWERS LASTING
THROUGH THURSDAY. AREAS FURTHER NORTHEAST CLOSER TO THE LOW
STAND THE BEST CHANCE TO SEE THE MOST IN TERMS OF SHOWER ACTIVITY.
TIMING DIFFERENCES ON THE SHOWERS ARE STILL PRESENT LEAVING SOME
UNCERTAINTY WITH POPS, KEPT AT HIGH CHANCE TO LOW END LIKELY.
TOTAL RAINFALL WILL BE UNDER ONE INCH FOR THIS EVENT. THE 12Z
ECMWF AND NAM FROM TODAY DO INDICATE THE POTENTIAL FOR SOME
HEAVIER SHOWERS ACROSS THE NORTH TUESDAY NIGHT INTO WEDNESDAY AS
THE MID-LEVEL ENERGY BEGINS TO TRANSFER TO THE COAST, THIS WILL
NEED TO BE WATCHED AS NEW DATA COMES IN. WITH PLENTY OF CLOUDS, LOW
TEMPERATURES WILL STAY UP AT NIGHT CLOSE TO 50 FOR MOST OF US
WHILE HIGHS STRUGGLE TOWARD 60, COOLER NW. NOT MUCH SPREAD IN THE
MODELS AND THERE ENSEMBLES/ STATISTICAL GUIDANCE ON TEMPERATURES,
WENT ON THE WARMER END EACH NIGHT AND THE COOLER END DURING EACH
DAY. IN TERMS OF TIDES IT LOOKS AS THOUGH THE WIND DIRECTION WILL
NOT CREATE DEPARTURES HIGH ENOUGH FOR MINOR COASTAL FLOODING OR
CREATE LOW ENOUGH DEPARTURES FOR BLOWOUT TIDES ATTM.


FRIDAY: LOW PRESSURE SYSTEM FINALLY DEPARTS WITH HIGH PRESSURE
BUILDING BACK IN. THIS ALLOWS FOR CLEARING FROM SOUTH TO NORTH AND
THE FIRST DRY DAY IN A WHILE. TEMPERATURES ARE FORECASTED TO BE
CLOSER TO MEX GUIDANCE AND THE 12Z ECMWF MODELED TWO METER
TEMPERATURES. CONTINUED NORTHWEST WINDS WITH THE BEST CHANCE OF
MIXING TO LEAD TO SOME AFTERNOON WIND GUSTS AROUND 20 MPH.

FRIDAY NIGHT THROUGH SUNDAY: DURING D+6 AND D+7, THE NEGATIVE
NAO/POSITIVE PNA PATTERN OF THE PAST TWO WEEKS IS PROJECTED TO
REVERSE. THIS TREND IS UNDERWAY, AND IS EVIDENT IN LESS HIGH-
LATITUDE BLOCKING. THE MAIN MID-LEVEL FEATURES IN THIS TIMEFRAME
ARE A CLOSED LOW LIFTING INTO THE CANADIAN MARITIMES ON SATURDAY,
FOLLOWED BY A SHORT-WAVE MOVING THROUGH A MORE ZONAL FLOW ON
SUNDAY. THERE IS MODEL DISAGREEMENT WITH THESE FEATURES, AS THE
GFS EJECTS THE CLOSED LOW SLOWER THAN THE ECMWF, RESULTING IN A
DELAYED RETURN TO A MORE ZONAL FLOW. THIS FURTHER RESULTS IN THE
GFS MOVING THE SHORTWAVE FURTHER NORTHEAST, WHILE THE ECMWF TAKES
IT MUCH FURTHER TO THE SOUTH OVER NEW ENGLAND. SOME OF THE GFS
ENSEMBLE MEMBERS ALSO SUPPORT THE ECMWF SOLUTION. GIVEN THE GFS
INITIALIZED MORE ROBUST WITH THE LEAD SHORT-WAVE /LOCATED OVER
NORTHERN SASKATCHEWAN AS OF THIS WRITING/ THAT RESULTS IN THE CUT-
OFF LOW, AND PREVIOUS GFS RUNS WERE MORE IN LINE WITH THE ECMWF,
FEEL THE GFS SOLUTION IS UNREALISTIC. THE ECMWF SOLUTION IS ALSO
MORE REPRESENTATIVE OF THE PROJECTED LACK OF HIGH-LATITUDE
BLOCKING.

FOR SATURDAY, SHORT-WAVE RIDGING ALOFT WILL ALLOW HIGH PRESSURE
TO BUILD IN FROM THE WEST. AT THIS TIME, THE COLUMN IS DRY SO NO
PRECIPITATION IS EXPECTED, AND TEMPS AT 850 HPA SUPPORT HIGHS IN THE
60S REGIONWIDE. A COLD FRONT IS PROJECTED TO MOVE THROUGH THE REGION
SAT NIGHT. AT THIS TIME, THE BEST DYNAMICS ARE SITUATED TO THE NORTH
AND MOISTURE IS LIMITED THROUGH THE COLUMN. FOR NOW, INCREASED SKY
COVER, BUT DID INSERT ANY POPS DUE TO UNCERTAINTY. IF THE TIMING OF
THE FRONT HOLDS, PROJECTED 850 HPA TEMPS WOULD SUPPORT BELOW NORMAL
HIGHS ON SUNDAY, IN THE LOW 50S TO LOW 60S.

FINALLY, MODELS INDICATE A POSSIBLE HYBRID SYSTEM DEVELOPING IN
THE GMEX AT THE TAIL END OF A FRONTAL BOUNDARY, PLACING IT IN THE
VICINITY OF FLORIDA DURING THE SATURDAY-SUNDAY TIMEFRAME. THIS
FEATURE WILL BEAR WATCHING.


&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

TONIGHT...VFR. WE LOSE THE GUSTY NORTHWEST WINDS BY THIS EVENING AND
BECOME LIGHT AND VARIABLE UNDER HIGH PRESSURE. MOSTLY CLEAR SKIES
EXPECTED.

MONDAY...VFR. WINDS BACK TOWARDS THE SOUTH-SOUTHWEST AND INCREASE TO
AROUND 10 KNOTS. INCREASING CIRRUS BECOMING ALTOCU BY EARLY
AFTERNOON. THINK ANY RAIN CHANCES HOLDS OFF UNTIL LATE MONDAY
NIGHT.

OUTLOOK...
MONDAY NIGHT AND TUESDAY...SOME RESTRICTIONS TO MVFR WITH SCATTERED
SHOWERS.

TUESDAY NIGHT THROUGH THURSDAY... SOME MVFR RESTRICTIONS WITH
SCATTERED SHOWERS. NORTH TO NORTHWEST WINDS WEDNESDAY AFTERNOON
THROUGH THURSDAY FROM 10-15 KNOTS WITH HIGHER GUSTS.

THURSDAY NIGHT AND FRIDAY: VFR, NORTHWEST WIND GUSTS FRIDAY
AFTERNOON FROM 15-20 KNOTS.

&&

.MARINE...

TONIGHT...SCA GUSTS SHOULD DIMINISH ON THE BAY BY THIS EVENING SO WE
CONTINUE THE END TIME OF 8PM. THE OCEAN FRONT TOO REMAINS UNCHANGED
FROM THE MIDNIGHT END TIME. HIGH PRESSURE MOVING IN WILL ALLOW THE
WIND AND SEAS TO RELAX LATE TONIGHT.

MONDAY...SUB-SCA CONDITIONS. WINDS BACK TOWARDS THE SOUTH-SOUTHWEST
TOMORROW AFTERNOON AROUND 10 TO 15 KNOTS. SEAS REMAIN 2 TO 3 FEET.

OUTLOOK...
MONDAY NIGHT THROUGH WEDNESDAY: SEAS AND WINDS BELOW SCA CRITERIA
BUT INCREASING WEDNESDAY WITH THE DEVELOPMENT OF A LOW PRESSURE TO
OUR NORTHEAST.

WEDNESDAY NIGHT THROUGH FRIDAY: OVERALL THINKING IS THAT WAVEWATCH
IS UNDERDONE BY ABOUT A FOOT ON THE SEAS. SEAS WILL LIKELY BE AT OR
OVER FIVE FEET THROUGH MOST OF THIS PERIOD WITH SOME DECREASE IN THE
SEAS FRIDAY. NORTHWEST WIND GUSTS OVER 25 KNOTS ARE ALSO POSSIBLE
EACH AFTERNOON. SCA POSSIBLE FOR MOST OF THIS TIMEFRAME.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...FREEZE WARNING FROM 3 AM TO 8 AM EDT MONDAY FOR PAZ054-055-061-
     062.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR PAZ060-101>106.
NJ...FREEZE WARNING FROM 3 AM TO 8 AM EDT MONDAY FOR NJZ001-007>010.
     FREEZE WARNING FROM 4 AM TO 8 AM EDT MONDAY FOR NJZ020>022-027.
     FROST ADVISORY FROM 2 AM TO 8 AM EDT MONDAY FOR NJZ012-013-
     015>019-023.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ450>455.
     SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ430-
     431.

&&

$$
SYNOPSIS...FRANCK/GAINES
NEAR TERM...HEAVENER
SHORT TERM...HEAVENER
LONG TERM...FRANCK/GAINES
AVIATION...GAINES/HEAVENER
MARINE...GAINES/HEAVENER





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