NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Oct 7, 7:55 PM EST, 3 hours 5 minutes earlier.
Area forecast discussion, Oct 7, 7:55 PM EST, 3 hours 5 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
855 PM EDT TUE OCT 7 2014
.SYNOPSIS...
A COLD FRONT WILL CROSS OUR AREA LATE TONIGHT INTO EARLY
WEDNESDAY. HIGH PRESSURE WILL THEN BRIEFLY BUILD INTO THE MID
ATLANTIC REGION LATER WEDNESDAY THROUGH THURSDAY. FOR THE END OF
THE WEEK, A WEAK AREA OF LOW PRESSURE MAY DEVELOP ALONG A NEARBY
FRONTAL BOUNDARY FRIDAY. THIS BOUNDARY WILL LINGER SOUTH OF OUR
AREA OVER THE WEEKEND, BEFORE POSSIBLY MOVING NORTH AS A WARM
FRONT MONDAY.
&&
.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
THE AXIS OF A MID LEVEL TROUGH EXTENDED FROM LOWER MICHIGAN TO
WESTERN OHIO TO EASTERN KENTUCKY THIS EVENING. THE FEATURE WILL
CONTINUE TO TAKE ON A NEGATIVE TILT DURING THE NIGHT AS IT ROTATES
AROUND THE MID LEVEL LOW OVER WESTERN ONTARIO. THE AXIS OF THE
TROUGH SHOULD PASS OVER OUR REGION BETWEEN ABOUT 300 AM AND 600
AM. A SURFACE COLD FRONT FROM THE WEST SHOULD MOVE THROUGH EASTERN
PENNSYLVANIA, NORTHEASTERN MARYLAND, DELAWARE AND NEW JERSEY
ALMOST COINCIDENT WITH THE MID LEVEL TROUGH.
SHOWERS IN ADVANCE OF THE MID LEVEL TROUGH EXTENDED FROM THE
EASTERN GREAT LAKES DOWN TO VIRGINIA AND THE CHESAPEAKE BAY REGION
THIS EVENING. THE SHOWERS WILL CONTINUE TO LIFT NORTHEASTWARD AND
THEY WILL AFFECT OUR FORECAST AREA OVERNIGHT.
ISOLATED THUNDERSTORMS ARE ANTICIPATED DURING THE NIGHT IN
ASSOCIATION WITH THE DYNAMIC MID LEVEL SYSTEM. ALSO, INSTABILITY
IS EXPECTED TO INCREASE, ESPECIALLY NEAR THE COAST.
A LOW LEVEL SOUTH SOUTHWESTERLY WIND JET WILL BE LOCATED OVERHEAD
DURING THE NIGHT. THERE REMAINS SOME CONCERN THAT ANY CONVECTION
COULD MIX SOME STRONG WIND GUSTS TO THE SURFACE, SO WE CONTINUE TO
MENTION THAT POTENTIAL IN THE FORECAST AND IN THE HAZARDOUS
WEATHER OUTLOOK.
A SOUTHERLY SURFACE WIND IS EXPECTED TO SHIFT TO THE SOUTHWEST
AND WEST WITH THE ARRIVAL OF THE COLD FRONT LATE TONIGHT. MINIMUM
TEMPERATURES ARE FORECAST TO RANGE MAINLY FROM THE MIDDLE 50S TO
THE LOWER 60S.
&&
.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
THE FRONT AND SHORT WAVE WILL LIFT NORTH OF THE AREA AROUND AND
SHORTLY AFTER SUNRISE, SO ANY SHOWER ACTIVITY WILL MOVE NORTH OF
THE AREA WITH THEM. WE THEN EXPECT SKIES TO MOSTLY CLEAR OUT
THROUGH THE DAY, ALTHOUGH THERE MAY BE SOME STRATOCU DEVELOP IN
THE WESTERLY FLOW TO OUR NORTHWEST THAT MAY FILTER ACROSS THE
AREA. WINDS WILL ONCE AGAIN BE QUITE GUSTY DURING THE DAY AS WE
BEGIN TO BECOME WELL MIXED WITH GUSTS OF AT LEAST 20-25 MPH.
TEMPERATURES SHOULD WARM QUITE NICELY WITH THE AMOUNT OF SUN
EXPECTED AND END UP SEVERAL DEGREES ABOVE NORMAL. A BLEND OF MIXED
ECMWF 925MB TEMPS, MAV/MET MOS, AND MOSGUIDE WAS USED FOR DAYTIME
HIGHS.
&&
.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
A RATHER QUIET START TO THE LONG TERM PERIOD AS SURFACE HIGH
PRESSURE WILL BE BUILDING ACROSS THE MID ATLANTIC REGION WEDNESDAY
NIGHT THROUGH THURSDAY, WITH A LONG WAVE TROUGH REMAINING
OVERHEAD. A COOL, DRY AIR MASS WILL BE SETTLING ACROSS THE REGION
WITH NEAR AVERAGE EARLY OCTOBER TEMPERATURES, AS LOWS BOTTOM OUT
IN THE 40S TO LOWER 50S WEDNESDAY NIGHT FOLLOWED BY HIGHS MAINLY
IN THE 60S TO AROUND 70 DEGREES THURSDAY.
FROM HERE, THE FORECAST BECOMES A BIT MORE TRICKY FOR THE END OF
THE WORK WEEK AND INTO THE WEEKEND. THE GFS, ECMWF, AND OTHERS ALL
INDICATE THAT A FRONTAL BOUNDARY SHOULD SET-UP EITHER NEAR OR JUST
TO THE SOUTH OF OUR AREA LATE THURSDAY NIGHT INTO FRIDAY. IN
ADDITION, A WEAK SURFACE LOW MAY FORM ALONG THIS FRONT AROUND THE
LOWER OHIO VALLEY AND THEN MOVE EAST ALONG THE BOUNDARY THROUGH
FRIDAY AND FRIDAY NIGHT. UNCERTAINTY STILL REMAINS WITH REGARDS TO
THE PLACEMENT OF THE FRONTAL BOUNDARY AND THE EVENTUAL DEVELOPMENT
AND TRACK OF POSSIBLE WEAK LOW PRESSURE, WITH THESE FACTORS
ULTIMATELY AFFECTING THE TIMING AND EXTENT OF PRECIPITATION ACROSS
OUR REGION. AT THIS TIME, THE BULK OF THE PRECIP ASSOCIATED WITH
THESE FEATURES LOOKS TO OCCUR FROM THE LATTER PART OF FRIDAY
THROUGH FRIDAY NIGHT, AND WE HAVE HIGH CHANCE POPS FOCUSED DURING
THIS TIME FRAME, WITH THE LONGEST DURATION OF STEADIER RAIN
EXPECTED FOR THE SOUTHEAST HALF OF THE FORECAST AREA AS THE WEAK
SURFACE LOW EMERGES EAST AND OFF THE COAST EARLY SATURDAY MORNING.
SOME MODEL DIFFERENCES CONTINUE THROUGH THE WEEKEND REGARDING THE
PLACEMENT OF THE LINGERING FRONT TO OUR SOUTH. OVERALL, THE MODELS
TEND TO SETTLE THE BOUNDARY FARTHER SOUTH AS HIGH PRESSURE FROM
AROUND THE GREAT LAKES NOSES IN ACROSS THE NORTHEAST TO NORTHERN
MID ATLANTIC STATES. HOWEVER, THERE WILL LIKELY BE SOME LINGERING
PRECIP AROUND, ESPECIALLY FOR OUR SOUTHERN ZONES, AND THIS IS
WHERE WE HAVE FOCUSED HIGHEST CHANCE POPS. AS MODEL SOLUTIONS
BECOME CLOSER IN AGREEMENT, WE CAN BETTER DETERMINE THE TIMING AND
EXTENT OF PRECIP ACROSS THE FORECAST AREA.
TOWARDS THE END OF THE LONG TERM PERIOD, MODEL SOLUTIONS TEND TO
DIVERGE EVEN MORE. AN UPPER LEVEL TROUGH LOOKS TO DEVELOP ACROSS
THE PLAINS STATES DURING THE MONDAY TO TUESDAY TIME FRAME, WITH
SUBSEQUENT UPPER RIDGING TAKING SHAPE ALONG THE EAST COAST. THERE
ARE DIFFERENCES WITH REGARDS TO THE STRENGTH AND EXTENT OF THIS
UPPER TROUGH AND POSSIBLE LOW PRESSURE DEVELOPING, AS THE ECMWF
DEVELOPS LOW PRESSURE OVER THE SOUTHERN PLAINS AND THE GFS SHOWS
LOW PRESSURE FORMING ACROSS THE UPPER MIDWEST. WITH THESE
DIFFERENCES IN MODEL SOLUTIONS, MUCH UNCERTAINTY EXISTS WITH
REGARDS TO THE TIMING AND ADVANCEMENT OF A POSSIBLE WARM FRONT
ACROSS OUR REGION MONDAY. FOR NOW, WE WENT WITH A BLEND OF WPC
GUIDANCE WITH CONTINUITY FOR TEMPERATURES, WINDS, AND PRECIP
CHANCES.
&&
.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.
VARIABLE CONDITIONS ARE ANTICIPATED OVERNIGHT AS AN AREA OF
SHOWERS AND SCATTERED THUNDERSTORMS LIFTS NORTHEASTWARD THROUGH
OUR REGION. CONDITIONS SHOULD FAVOR VFR AND MVFR. HOWEVER, IFR
CONDITIONS ARE POSSIBLE FOR A SHORT TIME IN THE HEAVIER SHOWERS.
A COLD FRONT FROM THE WEST SHOULD PASS THROUGH OUR REGION BETWEEN
ABOUT 0800Z AND 1100Z. CONDITIONS ARE FORECAST TO IMPROVE TO VFR
WITH A CLEARING SKY FOR WEDNESDAY AS DRY AIR ARRIVES IN THE WAKE
OF THE FRONT.
A SOUTHERLY WIND AROUND 6 TO 12 KNOTS IS ANTICIPATED FOR MUCH OF
THE NIGHT. WE CONTINUE TO MENTION LOW LEVEL WIND SHEAR DUE TO THE
EXPECTED LOW LEVEL SOUTH SOUTHWESTERLY WIND JET BEING OVERHEAD
FROM ABOUT 0200Z UNTIL 0800Z.
THE WIND DIRECTION IS EXPECTED TO SHIFT TO THE SOUTHWEST AND WEST
FOLLOWING THE PASSAGE OF THE COLD FRONT. A GUSTY WEST WIND IS
FORECAST FOR WEDNESDAY. SUSTAINED SPEEDS SHOULD BE AROUND 10 TO 14
KNOTS WITH GUSTS INTO THE 20S.
OUTLOOK...
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...VFR CONDITIONS ARE
EXPECTED WITH WESTERLY WINDS.
FRIDAY THROUGH SUNDAY...MOSTLY VFR CONDITIONS THROUGH THE PERIOD,
BUT SCATTERED SHOWERS/RAIN WITH MVFR CIGS/VSBYS ARE POSSIBLE AT
TIMES, ESPECIALLY FOR OUR SOUTHERN TAF SITES, INCLUDING KACY,
KMIV, KILG, AND KPHL.
&&
.MARINE...
SMALL CRAFT ADVISORY IS IN EFFECT FOR ALL WATERS. THE ADVISORY
FOR DELAWARE BAY WILL REMAIN ENDING AT 6 AM. NOT CONFIDENT ENOUGH
ON ANY WIND GUSTS MIXING DOWN TO THE SURFACE DURING THE DAY
WEDNESDAY TO EXTEND. THE ADVISORY ON THE OCEAN REMAINS AS IS AS
SEAS WILL REMAIN ELEVATED INTO WEDNESDAY ONCE THE INCREASE LATER
THIS EVENING.
A COLD FRONT WILL MOVE THROUGH TONIGHT AND WILL BRING AN AREA OF
SHOWERS AND POSSIBLY THUNDERSTORMS TO THE WATERS. THERE COULD BE
SOME LOCALLY STRONG WIND GUSTS WITH ANY OF THE STRONGER SHOWERS OR
THUNDERSTORMS AS WINDS ABOVE THE SURFACE ARE QUITE STRONG. WE DO
NOT BELIEVE IT WOULD BE A LONG DURATION WIND GUST EVENT TO NEED A
GALE WARNING SINCE THE GUSTS WOULD MORE LIKELY OCCUR WITH ANY
CONVECTION.
OUTLOOK...
WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...SUB-ADVISORY CONDITIONS
ARE EXPECTED.
FRIDAY THROUGH SUNDAY...SUB-ADVISORY CONDITIONS ARE EXPECTED TO
CONTINUE AT THIS TIME. SOME SCATTERED SHOWERS/RAIN ARE POSSIBLE AT
TIMES THROUGH THIS PERIOD WHICH COULD TEMPORARILY REDUCE
VISIBILITIES, ESPECIALLY FOR OUR SOUTHERN WATERS.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT WEDNESDAY FOR ANZ450>455.
SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ430-431.
&&
SYNOPSIS...KLINE
NEAR TERM...IOVINO
SHORT TERM...ROBERTSON
LONG TERM...KLINE
AVIATION...IOVINO/KLINE
MARINE...KLINE/ROBERTSON