Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 211721
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
121 PM EDT TUE OCT 21 2014

.SYNOPSIS...
LOW PRESSURE OVER LAKE ONTARIO WILL SLIDE SOUTHEAST TO THE NEW
JERSEY COAST THIS EVENING. IT SLOWLY INTENSIFIES WEDNESDAY AND
PASSES SOUTHEAST OF CAPE COD THURSDAY NIGHT. HIGH PRESSURE OVER THE
OHIO VALLEY LATE IN THE WEEK WILL AWAIT THE PASSAGE OF A COLD FRONT
SATURDAY NIGHT THEN BUILD OVER THE MID ATLANTIC STATES SUNDAY AND
MONDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
ADDED THUNDER TO EXTREME EASTERN NEW JERSEY FOR A COUPLE HOURS AS
WE ARE SEEING RAPIDLY FORMING CONVECTION IN EASTERN OCEAN AND
MONMOUTH COUNTIES. WE HAVE RECEIVED MULTIPLE PEA TO DIME SIZE HAIL
REPORTS WITH THESE STORMS ALONG WITH VERY HEAVY RAINFALL. FREEZING
LEVELS ACROSS THE AREA ARE AROUND 8KFT AND WITH AMPLE COLD AIR
ALOFT, THOUGH THE COLDEST PART OF THE COLD POOL IS STILL TO OUR
WEST, LAPSE RATES ARE STEEPENING AND WHEN YOU ADD IN A WEAK PSEUDO-
SEABREEZE FOR THE SURFACE FORCING AND 500-1000J/KG OF MUCAPE TO
TAP INTO RAPID DEVELOPMENT OCCURS. THE GOOD THING IS WITH THIS
ACTIVITY BEING SO CLOSE TO THE COAST, WITH A NORTHEAST MOVEMENT,
IT SHOULD BE OFF THE COAST WITHIN A COUPLE HOURS.

OTHERWISE, THE MAIN FORECAST CHALLENGE CONTINUES TO BE THE TIMING
AND COVERAGE OF THE ASSOCIATED SHOWERS, TO OUR WEST, THIS AFTERNOON AS
ANOTHER STRONG SHORT WAVE ROUNDS THE BASE OF THE TROUGH. WE
CONTINUED SLIGHT CHC TO CHC POPS FOR ISOLATED/SCATTERED SHOWERS
FOR THE AFTERNOON, MOSTLY ACROSS OUR WESTERN ZONES WITH AN
INCREASE TO LIKELY FOR AREAS CLOSER TO THE INCOMING TROUGH.

THE AIRMASS IS MODERATING AHEAD OF THE MAIN UPPER-
LEVEL TROUGH AND THE ASSOCIATED WAA WILL YIELD WARMER AFTERNOON
TEMPERATURES. THERE MAY BE A SQUEEZE PLAY THOUGH AS THE WARMEST
AIR MAY SLIDE UP ACROSS OUR DELMARVA AND EASTERN ZONES. THEREFORE,
A BLEND OF THE NAM/GFS MOS RESULTED IN THE WARMEST HIGH
TEMPERATURES IN THESE AREAS. OTHERWISE, THE FLOW SHOULD START TO
SHIFT AROUND FROM THE SOUTHWEST TO THE NORTHWEST DURING THE COURSE
OF THE DAY AS LOW PRESSURE DEVELOPS OVER OUR AREA BEFORE
CONSOLIDATING SOME JUST TO OUR EAST TOWARD EVENING.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
A CLOSED LOW WILL STRENGTHEN ACROSS THE MID ATLANTIC AND NORTHEAST
THROUGH TONIGHT. AS THIS OCCURS, SURFACE LOW PRESSURE SHOULD
CONSOLIDATE SOME MORE OFF OF OUR COAST. THE MODEL GUIDANCE OVERALL
SHOWS A SIGNIFICANT SHORT WAVE ROUNDING THE BASE OF THE CLOSED LOW
OVERNIGHT. THIS FEATURE LOOKS TO NEAR OUR SOUTHEASTERN ZONES TOWARD
DAYBREAK. AS THIS OCCURS, LARGE SCALE LIFT IN CONJUNCTION WITH SOME
POTENTIAL FRONTOGENETIC FORCING ON THE WEST SIDE OF THE SURFACE LOW
SHOULD ORGANIZE AND AREA OF RAIN. THIS LOOKS TO GENERALLY BE ACROSS
THE EASTERN HALF OF THE CWA. AS A RESULT, LIKELY POPS ARE CARRIED
ACROSS MUCH OF THE CWA ESPECIALLY LATE WITH THE SLIGHTLY HIGHER
VALUES ACROSS THE EASTERN ZONES.

WHILE ISOLATED THUNDER CANNOT BE RULED OUT ESPECIALLY ACROSS THE
EASTERN AREAS AS AT LEAST SOME MID LEVEL INSTABILITY COULD BE
PRESENT, THE CHC APPEARS TO BE RATHER LOW AND THEREFORE IT WAS NOT
CARRIED ATTM. THE POTENTIALLY DEVELOPING RAIN AREA HAS THE SIGNATURE
OF WHAT COULD BE THE START OF A PIVOT REGION ACROSS AT LEAST A
PORTION OF OUR AREA STARTING NEAR DAYBREAK. THIS WOULD BE DUE TO THE
CLOSED LOW MOVING OVERHEAD AND THE STRONG SHORT WAVE PIVOTING UP
FROM THE SOUTHWEST AS THE SURFACE LOW ORGANIZES SOME MORE OFFSHORE.

AS FOR LOW TEMPERATURES, WE UTILIZED MAINLY AN EVEN NAM/GFS MOS
BLEND. WHILE THE WINDS SHOULD BE LIGHT FOR MOST, A NORTHERLY WIND
SHOULD START TO INCREASE SOME MAINLY LATE AS THE SYSTEM AS A WHOLE
STARTS TO BECOME BETTER ORGANIZED TO OUR EAST.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
500 MB: A LARGE AND VERTICALLY DEEP CLOSED LOW ALONG THE MID ATLANTIC
COAST TO START THE PERIOD WILL SLIDE TO THE EAST OF NEW ENGLAND FRIDAY.
A POTENTIALLY STRONG SHORT WAVE IS SLATED TO MOVE FROM SOUTH CENTRAL
CANADA SATURDAY THROUGH SOUTHEAST CANADA SUNDAY THEN TO BE FOLLOWED
BY TEMPORARY RIDGING NEXT MONDAY.

TEMPERATURES: CALENDAR DAY AVG TEMPS FOR OCTOBER WERE ABOUT 2 DEGREES
ABOVE NORMAL THROUGH THE 20TH AND DIFFICULT TO BELIEVE THIS MONTH
CAN NOW AVERAGE NORMAL OR BELOW. DAILY AVERAGES WILL B A LITTLE
ABOVE NORMAL THROUGH FRIDAY WITH MINIMUM TEMPS SIGNIFICANTLY ABOVE
NORMAL AND MAXIMUMS NEAR OR SLIGHTLY BELOW NORMAL. ABOVE NORMAL TEMPS
CONTINUE SATURDAY WITH A POSSIBLE BRIEF COOLING TO NEAR NORMAL SUNDAY
BEFORE WARMING WELL ABOVE NORMAL EARLY NEXT WEEK.

FORECAST BASIS: UNLESS OTHERWISE NOTED THE LONG TERM PERIOD OF THIS
FORECAST IS GENERALLY BASED ON A 50 50 BLEND OF THE 00Z/21 NAM/GFS
MOS FOR THE PERIOD WEDNESDAY-THURSDAY...THE 00Z/21 GFS MOS THURSDAY
NIGHT AND FRIDAY...THEN THEREAFTER (FRIDAY NIGHT ONWARD) THE 0502Z/21
WPC GRIDDED GUIDANCE. THE 00Z/21 NCEP GUIDANCE MAXIMUM TEMPS MAY BE
SIGNIFICANTLY TOO WARM WEDNESDAY, THURSDAY AND NEXT SUNDAY. THE
WED/THU 00Z/21 NCEP MOS GUIDANCE WAS BLENDED DOWN WITH THE 00Z/21
ECMWF TEMPS. WEDNESDAY AND THURSDAY COULD BE EVEN COOLER THAN THE
330 AM FCST ISSUANCE INDICATED.

PRECIPITATION PROBABILITY GUIDANCE IS CHECKED AGAINST THE 21Z/20
SREF 3HRLY POPS FOR .01 THROUGH 12Z FRIDAY AND THEREAFTER THE
00Z/21 GEFS 6HR POPS FOR 0.05.

THE DAILIES BELOW...

WED-THU...PERIODS OF SHOWERS IN THE DEEP CYCLONIC FLOW WITH  UNSTABLE
MID LVLS..EVEN SMALL POTENTIAL OF THUNDER NNJ WHERE SWI IS SUB ZERO
AT TIMES. A TROWAL CURLS WESTWARD AROUND THE NORTHWEST SIDE OF
THE DEEP CYCLONIC CIRCULATION. RAIN SHOULD BE HEAVY AT TIMES
WEDNESDAY ALONG THE COAST AND THEN POSSIBLY THURSDAY IN NNJ NEAR
THE AXIS OF THE 850 MB WIND SHIFT (850 MB VORTICITY AXIS) FROM NE
TO NW AND COINCIDENT WITH THE TROWAL.
CONFIDENCE: ABOVE AVERAGE.

THU NIGHT-FRIDAY...AS THE LOW ALOFT MOVES AWAY TO OUR NORTHEAST
THE POTENTIAL FOR RAIN SHOWERS SHOULD GRADUALLY DIMINISH IN OUR
AREA. CLOUD COVER WILL STILL BE PREDOMINANT.

CONFIDENCE: AVERAGE SINCE TIMING OF THE IMPROVEMENT IS UNCERTAIN.

THIS WEEKEND...A SHORT WAVE WITH A 12 HR HFC OF OVER 120 METERS
PASSES THRU NYS AND NEW ENGLAND SAT AND SAT NIGHT. 850 TEMPS IN
ITS WAKE COOL 6C ON THE ECMWF FOR NEXT SUNDAY. THE SHORT WAVE
IS NOT EXPECTED TO HAVE MUCH MOISTURE ASSOCIATED WITH IT. THEREFORE,
WE ARE NOT ANTICIPATING ANY RAIN.

CONFIDENCE: AVERAGE...JUST A MATTER OF INTENSITY OF THE SHORT
WAVE DIVING SEWD TOWARD THE NE USA SAT EVENING AND THE RESULTANT
COOLER 850MB TEMPERATURES ON SUNDAY.

NEXT MONDAY...A MID LEVEL RIDGE FROM THE WEST SHOULD BUILD TOWARD
OUR REGION WHEN THE NICEST WEATHER OF THIS 6 DAY EXTENDED PERIOD
SHOULD OCCUR.  CONFIDENCE: AVERAGE FOR A DAY 7 FORECAST.

&&

.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

TODAY...MOSTLY VFR. SOME SHOWERS WILL BE AROUND THE AREA AS LOW
PRESSURE DEVELOPS OVERHEAD BEFORE STARTING TO CONSOLIDATE SOME
JUST TO OUR EAST TOWARD EVENING. WHILE MVFR CONDITIONS CAN OCCUR
FOR A TIME WITH SHOWERS, THERE IS SOME LOWER CONFIDENCE ON THE
TIMING AND AREAL COVERAGE. THERE IS THE POTENTIAL FOR A LOW-TOPPED
THUNDERSTORM TO DEVELOP THIS AFTERNOON, HOWEVER THIS LOOKS TO BE
ISOLATED IF IT WERE TO DEVELOP. A SOUTH-SOUTHWEST WIND WILL SHIFT
TO THE WEST AND NORTHWEST DURING THE COURSE OF THE DAY, HOWEVER
SPEEDS ARE EXPECTED TO BE AROUND 5 KNOTS.

TONIGHT...VFR CEILINGS OVERALL. THERE IS THE POTENTIAL FOR MVFR
VISIBILITIES AT TIMES WITH SOME SHOWERS. A MORE ORGANIZED AREA OF
RAIN SHOULD DEVELOP ESPECIALLY LATE, WHERE SOME MVFR CEILINGS
SHOULD START TO DEVELOP. LOWER CONFIDENCE ON THE MVFR CEILINGS. THE
WINDS ARE ANTICIPATED TO BECOME NORTH TO NORTHEAST NEAR 5 KNOTS,
BUT INCREASE SOME TOWARD DAYBREAK.

OUTLOOK...
WEDNESDAY THROUGH THURSDAY...CONDITIONS VARYING BETWEEN VFR CIGS AND
MVFR CONDITIONS IN PERIODS OF SHOWERY RAINS. POTENTIAL BRIEF IFR
CONDITIONS KABE...KTTN AND KACY. NORTH NORTHWEST WIND GUSTS 20 KT
WEDNESDAY AND 25 TO 30 KT THURSDAY. CONFIDENCE: ABOVE AVERAGE.

THURSDAY NIGHT AND FRIDAY...MAINLY VFR CIGS WITH A CHANCE OF SHOWERS.
NORTHWEST WIND GUSTS 20-25 KT.  CONFIDENCE: ABOVE AVERAGE.

SATURDAY...VFR SCT-BKN AOA 5000 FT.  NORTHWEST WIND GUSTS 15 TO 20 KT.
CONFIDENCE: ABOVE AVERAGE.

&&

.MARINE...
TODAY AND TONIGHT...LOW PRESSURE DEVELOPING OVERHEAD WILL START TO
CONSOLIDATE SOME OFFSHORE TONIGHT. THIS WILL RESULT A SOUTHWESTERLY
WIND TURNING TO THE WEST AND NORTHWEST TODAY THEN NORTH-NORTHEAST
DURING TONIGHT. GIVEN THE NEARBY LOCATION OF THE ORGANIZING SURFACE
LOW, THE FLOW IS FORECAST TO BE ON THE LIGHTER SIDE. AFTER SOME
SURGE IN THE SEAS OFFSHORE EARLIER, THE SEAS ARE EXPECTED TO BE
BELOW ADVISORY CRITERIA THROUGH TONIGHT. THE NORTHERLY WINDS MAY
START TO INCREASE THOUGH TOWARD DAYBREAK WEDNESDAY.

OUTLOOK...
MIDWEEK...A GALE WATCH WAS ISSUED FOR MOST OF OUR WATERS...FOR
OCNL GUSTS AROUND 35 KT WEDNESDAY AFTN POSSIBLY INTO MIDDAY
THURSDAY. ONLY THE UPPER PART OF DELAWARE BAY IS WITHOUT A GALE
WATCH AND THERE WE ISSUED AN SCA.

FUTURE FORECASTS WILL DETERMINE WHETHER THE GALE WATCH IS A BIT
TOO ROBUST AND WE`LL NEED TO SETTLE FOR A STRONG SCA. FOR NOW...BE
PREPARED FOR THE POSSIBILITY OF GALES. AT THIS TIME...AM 60 PERCENT
CONFIDENT THAT AT LEAST THE S NJ AND DE COASTAL WATERS WILL VERIFY
A GALE BY THURSDAY. CONFIDENCE: A BIT ABOVE AVERAGE.


THURSDAY NIGHT THROUGH FRIDAY NIGHT...NORTHWESTERLY WIND GUSTS OF
25 TO 30 KNOTS AT TIMES. SCA LIKELY. CONFIDENCE: ABOVE AVERAGE

SATURDAY...NO MARINE HEADLINES ARE ANTICIPATED. NORTHWEST WIND GUSTS
15-20 KT. CONFIDENCE: ABOVE AVERAGE.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...GALE WATCH FROM WEDNESDAY AFTERNOON THROUGH LATE WEDNESDAY
     NIGHT FOR ANZ431-450>455.
     SMALL CRAFT ADVISORY FROM NOON WEDNESDAY TO 6 AM EDT THURSDAY
     FOR ANZ430.

&&

$$
SYNOPSIS...DRAG
NEAR TERM...GORSE/HEAVENER
SHORT TERM...GORSE
LONG TERM...DRAG
AVIATION...DRAG/GORSE
MARINE...DRAG/GORSE






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