Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 251954
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
354 PM EDT SAT OCT 25 2014

.SYNOPSIS...
A COLD FRONT WILL PASS THROUGH THE AREA TONIGHT. THE MID-ATLANTIC
REGION WILL BE SITUATED BETWEEN LOW PRESSURE OVER EASTERN CANADA AND
HIGH PRESSURE BUILDING IN FROM THE TENNESSEE VALLEY ON SUNDAY. THEN
THE HIGH PRESSURE SYSTEM WILL RIDGE INTO THE AREA SUNDAY NIGHT AND
MONDAY. A WARM FRONT WILL LIFT NORTH OF THE AREA TUESDAY BEFORE A
COLD FRONT MOVES THROUGH WEDNESDAY. ANOTHER HIGH PRESSURE SYSTEM
BRIEFLY RETURNS TO THE AREA ON THURSDAY. A COLD FRONT IS
EXPECTED TO PASS THROUGH THE NORTHEAST ON FRIDAY WITH A LOW
PRESSURE SYSTEM FORMING ALONG IT. CANADIAN HIGH PRESSURE WILL THEN
BUILD EAST FOR NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
A RELATIVELY DRY COLD FRONT WILL MOVE ACROSS THE AREA TONIGHT, ALONG
WITH A FAIRLY STRONG SHORT WAVE/VORTICITY MAX. HOWEVER, WITH A LACK
OF VERTICAL MOISTURE ASSOCIATED WITH THE SYSTEM, WE DO NOT EXPECT
ANY PRECIPITATION ACROSS THE AREA, MOSTLY AN INCREASE IN CLOUD COVER
OVERNIGHT. THE MORE LIKELY MEASURABLE PRECIPITATION IS EXPECTED TO
PASS NORTH OF THE AREA. THERE COULD BE A FEW SPRINKLES MOVE ACROSS
THE NORTHERN TIER OF THE AREA, BUT FOR NOW WE WILL KEEP THE FORECAST
PRECIP FREE.

TEMPERATURES WILL COOL THROUGH THE NIGHT, ESPECIALLY BEHIND THE
FRONTAL BOUNDARY WHICH SHOULD MOVE THROUGH AFTER MIDNIGHT. OVERNIGHT
LOWS WERE A BLEND OF MAV/MET MOS AND MOSGUIDE.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
STRONG NORTHWEST FLOW BETWEEN LOW PRESSURE TO THE NORTHEAST AND HIGH
PRESSURE BUILDING BUILDING IN FROM THE SOUTHWEST WILL BE THE MAIN
CONCERN ON SUNDAY. LOOKING AT SOUNDINGS, GUSTS OF AT LEAST 25-30
MPH, WITH GUSTS OF 35-40 MPH POSSIBLE, CAN BE EXPECTED FROM
MID-MORNING INTO THE LATE AFTERNOON. NO PRECIPITATION IS EXPECTED,
ALTHOUGH THERE COULD BE AN INCREASE IN CLOUD COVER DURING THE DAY.

HIGHS ARE EXPECTED TO BE A LITTLE ABOVE NORMAL FOR MOST PLACES. WE
USED A BLEND OF MIXED 925MB ECMWF TEMPS, MAV/MET MOS, AND MOSGUIDE
FOR DAYTIME HIGHS.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
THE GFS INITIALIZATION LOOKED BETTER THAN THE WRF-NMMB AT 500MB
WHILE THERMALLY THERE WERE ISSUES IN THE LOCAL AREA, BUT UPWIND BOTH
LOOKED VERY GOOD. THERE IS PRETTY GOOD MODELING CONSENSUS CONCERNING
THE COLD FRONT ON WEDNESDAY, MUCH LESS CONSENUS WITH THE
EVOLUTION OF THE DEEPENING TROF FOR NEXT WEEKEND. THE GEFS MEAN IS
MORE PROGRESSIVE THAN THE GFS WHICH BY ITSELF IS AT ONE END OF THE
PROGRESSIVE SPECTRUM. THE LATEST ECMWF CONTINUES THE 00Z RUN IDEA
OF A CLOSING CUT-OFF LOW AND NOR`EASTER. ITS 00Z ENSEMBLE MEAN WAS
MORE PROGRESSIVE, ALTHOUGH THE SD(S) AT THE BASE OF THE TROF SHOW
THERE ARE BIG DIFFERENCES IN TROF STRENGTH AMONG ITS MEMBERS. THE
BIGGEST DIFFERENCES ARE BEYOND SATURDAY AT THIS POINT AND WE HAVE
OPTED FOR A MODEL BLEND EARLY AND THEN A CAN GGEM/WPC CONSENSUS
FOR FRIDAY AND SATURDAY.

ON SUNDAY NIGHT THE GRADIENT WILL BE RELAXING. FCST BOUNDARY LAYER
WINDS SUGGEST DECOUPLING BY MORNING. WITH GENERALLY CLEAR SKIES, WE
OPTED FOR THE COOLER GFS MOS MINS BECAUSE OF THIS. ANY FROST THAT
DOES OCCUR IS EXPECTED TO BE NORTH WHERE THE GROWING SEASON HAS
ENDED.

ON MONDAY THERE WILL BE SOME WAA CLOUDS, ESPECIALLY NORTH. MOST LOOK
TO BE AT HIGH ALTOCU OR CIRRUS LEVEL. LESS OVERALL SOUTH. WHILE
THERE IS A PREDICTED SHORT WAVE LATE, WE STILL HAVE RIDGING
INCREASING, SO OVERALL THE DAY SHOULD BE MOSUNNY. BASED ON FCST
925MB AND 850MB TEMPS (EVEN THE WRF`S), GFS MOS MAX TEMPS LOOKED
BETTER AND MAX TEMPS WERE NOT TOUCHED MUCH.

ON MONDAY NIGHT A WEAK WARM WILL START MOVING TOWARD OUR AREA. NOT
MUCH MOISTURE PREDICTED WITH IT, MAINLY AT CIRRUS LEVELS AGAIN. GIVEN
THIS IS GETTING FURTHER IN TIME, WE WERE NOT AS AGGRESSIVE WITH
RADIATING THE MINS. THE SFC GRADIENT IS LOOSE ENOUGH THAT WINDS
WOULD DECOUPLE.

AS THE WARM FRONT MOVES NORTH OF OUR CWA TUESDAY, A POCKET OF
EXTREMELY WARM AIR FOR LATE OCTOBER WILL BE MOVING INTO OUR CWA.
925MB AND 850MB TEMPS OF THIS LEVEL IN SUMMER WOULD GET US INTO
THE 80S IN A BIG CHUNK OF OUR CWA. MODEL FCST SOUNDINGS ARE NOT IN
MUCH OF A MIXING MOOD, MAYBE TOO MUCH OF AN EXTENT BECAUSE THE SW
GRADIENT DOES NOT LOOK THAT FEEBLE. AGAIN THIS IS GETTING OUT
THERE IN TIME, BUT PREDICTED 1000-850MB THICKNESSES OVER US TUE IN
THE CONUS YDA GAVE HIGHS NEAR 80F. THE SOUNDING MAXT MACROS ARE IN
THE UPPER 70S TO MID 80S. SO WE COMPROMISED UPWARD BETWEEN THE
LATTER AND CONTINUITY. TUE RECORD HIGHS ARE MAINLY IN THE LOWER
TO MID 80S.

FOR TUESDAY NIGHT AND WEDNESDAY WE FOLLOWED THE USUAL MODEL TIMING
BIAS FOR THE TIMING OF THE COLD FRONT AND SHOWERS. MAINTAINED THE
THOUGHT OF HIGHER POPS AS THE PREDICTED ENTRANCE REGION OF THE 250MB
JET SHOULD ENHANCE UPWARD MOTION/PCPN CHANCES OVER OUR CWA.
TIMING IS CLOSEST TO THE CAN GGEM SOLUTION. WHILE THE GFS HAS
EDGED FASTER, ITS 12Z GEFS MEAN IS NOW SLOWER THAN THE OP MODEL.
WITH A TIGHTER TIMING SOLUTION, WE REMOVED MOST OF THE POPS FOR
WEDNESDAY NIGHT. TUESDAY NIGHT COULD BE WARMER WITH A DECENT SW
GRADIENT AND NOT SURE ABOUT HOW MUCH OF A COOL OFF ON WEDNESDAY AS
OUR STARTING POINT WILL BE RELATIVELY HIGH.

THE COLD FRONT TREND FOR THURSDAY IS FOR MORE OF A SOUTHERN
PROGRESSION. THAT STARTED ON THE 00Z RUN AND CONTINUED WITH THE
12Z RUN. A DRY DAY WITH NEAR SEASONAL TEMPERATURES ARE PREDICTED.

FRIDAY INTO THE WEEKEND HAS LOOKED PRETTY DYNAMIC FOR A WHILE, ITS
THE PLAYERS ON THE TEAM THAT HAVE BEEN TRADED ALL OVER THE PLACE. A
COLD FRONT IS EXPECTED TO APPROACH AS THE TROF BEGINS DIGGING ON
FRIDAY. SOUTHERN STREAM CYCLOGENESIS IS INDICATED BY BOTH THE
CAN GGEM AND ECMWF. THOSE RESULTS FOR FRIDAY NIGHT/SATURDAY ARE
ABOUT THE SAME WITH AN INVERTED TROF PREDICTED OVER OUR CWA AND A
CHANCE FOR RAIN. THE BIGGER MODELING DIFFERENCES ARE BEYOND
SATURDAY. EITHER WAY NEXT WEEKEND DOES NOT LOOK AS INVITING AS
THIS WEEKEND.

&&

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

VFR CONDITIONS ARE EXPECTED THROUGH THE PERIOD. GUSTY WESTERLY WINDS
GENERALLY AROUND 15-20 KNOTS WILL CONTINUE FOR THIS AFTERNOON,
BEFORE GUSTS DROP OFF LATE THIS AFTERNOON/EARLY THIS EVENING. A
STEADY WEST BREEZE OF 10 KNOTS OR LESS IS EXPECTED THROUGH MOST OF
THE OVERNIGHT BEFORE WINDS INCREASE AND GUSTS INCREASE SUNDAY
MORNING BEHIND THE FRONTAL BOUNDARY. WIND GUSTS OF 25-30 KNOTS ARE
EXPECTED DURING THE DAY SUNDAY, WITH GUSTS AS HIGH AS 35 KNOTS
POSSIBLE.

OUTLOOK...
SUNDAY NIGHT THROUGH TUESDAY...VFR.

TUESDAY NIGHT AND WEDNESDAY...PREDOMINATELY VFR. ALTHOUGH A BRIEF
PERIOD OF MVFR AND SHRA POSSIBLE WITH COLD FROPA.

WEDNESDAY NIGHT AND THURSDAY...VFR.

&&

.MARINE...
SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR TONIGHT AND SUNDAY AS
STRONG WEST-NORTHWEST WINDS WILL INCREASE TONIGHT AND ESPECIALLY
SUNDAY BEHIND A COLD FRONTAL PASSAGE. WIND GUSTS OF AROUND 30 KNOTS
ARE EXPECTED OVERNIGHT INTO SUNDAY. IT IS POSSIBLE AN OCCASIONAL
GUST NEAR 34 KNOTS MAY OCCUR DURING THE DAY SUNDAY, BUT WE DO NOT
EXPECT IT TO BE FREQUENT ENOUGH TO NEED A GALE WARNING.

OUTLOOK...
SUNDAY NIGHT...WE EXTENDED THE SMALL CRAFT ADVISORY IN THE SOUTHERN
ATLANTIC WATERS THROUGH SUNDAY NIGHT AS THE GRADIENT IS PREDICTED TO
RELAX SLIGHTLY LATER.

MONDAY THROUGH TUESDAY...SUB SMALL CRAFT ADVISORY CONDITIONS
EXPECTED. THE SOUTHWEST FLOW IS PREDICTED TO START INCREASING ON
TUESDAY.

TUESDAY NIGHT AND WEDNESDAY...THERE IS A CHANCE FOR SMALL CRAFT
ADVISORY CONDITIONS, HIGHER CHANCE ON THE OCEAN. THE SOUTHWEST FLOW
IS EXPECTED TO INCREASE FURTHER, ALTHOUGH THE MODELS TEND TO BE A
BIT TOO BULLISH IN THIS REGARD AND SUBSEQUENTLY WITH THE SEAS.

WEDNESDAY NIGHT THROUGH THURSDAY...A RETURN OF SUB SMALL CRAFT
ADVISORY CONDITIONS.

&&

.FIRE WEATHER...
SUNDAY WILL BE VERY GUSTY AND RELATIVE HUMIDITY LEVELS WILL DROP TO
AROUND 30-35 PERCENT FOR MANY LOCATIONS ACROSS SOUTHEAST
PENNSYLVANIA, CENTRAL/SOUTHERN NEW JERSEY, AND DELMARVA. HOWEVER,
WITH THE RECENT RAINS IN THE LAST WEEK, FUELS ARE STILL FAIRLY
MOIST, SO WE ARE NOT ISSUING ANY ENHANCED FIRE WEATHER STATEMENTS.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 6 AM EDT MONDAY
     FOR ANZ450>455.
     SMALL CRAFT ADVISORY FROM 8 AM TO 9 PM EDT SUNDAY FOR ANZ430-
     431.

&&

$$
SYNOPSIS...GIGI/KLEIN
NEAR TERM...ROBERTSON
SHORT TERM...ROBERTSON
LONG TERM...GIGI
AVIATION...GIGI/KLEIN/ROBERTSON
MARINE...GIGI/KLEIN/ROBERTSON
FIRE WEATHER...ROBERTSON






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