Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 210728
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
328 AM EDT TUE OCT 21 2014

.SYNOPSIS...
LOW PRESSURE WILL PASS OFF THE MID ATLANTIC COAST TONIGHT. THE
LOW IS THEN EXPECTED TO MOVE SLOWLY NORTH AND NORTHEASTWARD,
REACHING THE WATERS OFF CAPE COD AROUND THURSDAY NIGHT AND
ARRIVING IN NOVA SCOTIA ON FRIDAY NIGHT. HIGH PRESSURE IS
ANTICIPATED TO BUILD INTO OUR REGION FROM THE SOUTHWEST FOR FRIDAY
INTO SATURDAY. A COLD FRONT IS EXPECTED TO ARRIVE SATURDAY NIGHT
WITH ANOTHER AREA OF HIGH PRESSURE FOLLOWING FOR SUNDAY AND
MONDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
AN UPPER-LEVEL TROUGH WILL CONTINUE TO AMPLIFY INTO THE NORTHEAST
THROUGH TODAY. AN INITIAL STRONG AND COMPACT SHORT WAVE CARVING OUT
THE TROUGH CONTINUES TO WORK ITS WAY ACROSS PENNSYLVANIA EARLY THIS
MORNING. THIS FEATURE IS WELL EVIDENT ON THE WATER VAPOR IMAGERY AS
IT LIFTS EAST-NORTHEASTWARD, AND APPEARS TO BE STRONGER THAN EARLIER
GUIDANCE INDICATED. AS A RESULT, THE DOWNSTREAM WAA AND LOWER LEVEL
CONVERGENCE/LIFT HAS BEEN STRONG ENOUGH TO DEVELOP AND ORGANIZE SOME
SHOWERS. THIS IS WITHIN A MOISTENING AIRMASS AS IT WAS INITIALLY
RATHER DRY ACROSS OUR AREA. THE AIRMASS WILL CONTINUE TO MOISTEN UP
SOME MORE TODAY AS THE UPPER-LEVEL TROUGH AMPLIFIES FURTHER.

A STRONGER MID/UPPER LEVEL JET DIVING DOWN THE WEST SIDE OF THE
TROUGH WILL PUSH STRONGER SHORT WAVE ENERGY ALONG. THIS WILL ASSIST
IN CUTTING OFF THE TROUGH FROM THE MAIN FLOW, THEREFORE THIS
UPPER-LEVEL TROUGH WILL BE CLOSING OFF DURING THE COURSE OF THE DAY.
THIS WILL ALSO TAKE LOW PRESSURE NEAR THE EASTERN GREAT LAKES EARLY
THIS MORNING, AND THEN MOVE IT OVER OUR AREA BEFORE IT STARTS TO
EVENTUALLY CONSOLIDATE OFFSHORE. THE MAIN FORECAST CHALLENGE IS THE
TIMING AND COVERAGE OF THE ASSOCIATED SHOWERS. AFTER SOME INITIAL
SHOWERS EARLY THIS MORNING MAINLY ACROSS THE WESTERN ZONES, THERE
COULD BE A BREAK BEFORE ADDITIONAL SHOWERS DEVELOP ESPECIALLY LATER
THIS AFTERNOON AS ANOTHER STRONG SHORT WAVE ROUNDS THE BASE OF THE
TROUGH. THE SOUNDINGS SHOW SOME INSTABILITY DEVELOPING, BUT THIS IS
MOSTLY CONFINED TO THE LOWEST LEVELS. AS A RESULT, WE HELD OFF ON
ADDING A THUNDER MENTION ATTM. WE CONTINUED CHC POPS FOR SCATTERED
SHOWERS THROUGH THE DAY, ALTHOUGH A TIME OF LIKELY POPS ACROSS THE
WESTERN 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/...
A MID LEVEL LOW IS EXPECTED TO PASS OFF THE DELMARVA COAST ON
WEDNESDAY MORNING. THE FEATURE IS THEN ANTICIPATED TO MEANDER OFF
OUR COAST FROM WEDNESDAY AFTERNOON INTO THURSDAY EVENING BEFORE
LIFTING NORTHEASTWARD AND REACHING THE WATERS OFF CAPE COD ON
FRIDAY MORNING. A SURFACE LOW IS FORECAST TO FOLLOW THE MID LEVEL
LOW CLOSELY DURING THE PERIOD.

WE ARE EXPECTING THE POTENTIAL FOR RAIN FROM WEDNESDAY THROUGH
THURSDAY MORNING. THE POSSIBILITY OF MODERATE TO HEAVY RAINFALL
SHOULD BE MOSTLY ON THE EAST SIDE OF THE DEVELOPING MID LEVEL LOW.
AS A RESULT, WE ARE NOT ANTICIPATING MUCH MODERATE TO HEAVY
RAINFALL IN OUR REGION. THE ONLY EXCEPTION IS IN OUR COASTAL AREAS
WEDNESDAY WHERE RAINFALL AMOUNTS MAY APPROACH AN INCH AT SOME
LOCATIONS. ALSO, MARGINAL INSTABILITY IN THAT AREA MAY TRANSLATE
INTO ISOLATED LIGHTNING AND THUNDER. REGARDLESS, THE EXPECTED
RAINFALL TOTALS SHOULD NOT RESULT IN ANY FLOODING PROBLEMS.

AS THE LOW BEGINS TO PULL AWAY TO OUR NORTHEAST ON THURSDAY
NIGHT, THE POTENTIAL FOR RAIN SHOWERS SHOULD END GRADUALLY IN OUR
AREA.

A COUPLE OF REINFORCING MID LEVEL SHORT WAVES SHOULD DROP OVER
OUR REGION FROM THE NORTHWEST IN THE CYCLONIC FLOW AROUND THE
DEPARTING MID LEVEL LOW OVER THE COMING WEEKEND. THE SHORT WAVES
ARE NOT EXPECTED TO HAVE MUCH MOISTURE ASSOCIATED WITH THEM.
THEREFORE, WE ARE NOT ANTICIPATING ANY PRECIPITATION AT THAT TIME.

A MID LEVEL RIDGE FROM THE WEST SHOULD BUILD TOWARD OUR REGION
FOR SUNDAY AND MONDAY.

DAYTIME HIGHS ARE FORECAST TO BE A BIT BELOW NORMAL WITH THE RAIN
ON WEDNESDAY AND THURSDAY. READINGS SHOULD RETURN TO NEAR NORMAL
FOR THE PERIOD FROM FRIDAY THROUGH MONDAY.

&&

.AVIATION /08Z 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 CONSOLIDATING 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. A SOUTH-SOUTHWEST WIND WILL SHIFT TO THE WEST AND
NORTHWEST DURING THE COURSE OF THE DAY, HOWEVER SPEEDS ARE EXPECTED
TO BE LESS THAN 10 KNOTS.

TONIGHT...VFR CEILINGS OVERALL. THERE IS THE POTENTIAL FOR MVFR
VISIBILITIES AT TIMES WITH SOME SHOWERS. A MORE ORGANIZED AREA OF
RAIN MAY DEVELOP LATE ESPECIALLY EAST OF KPHL, WHERE SOME MVFR
CEILINGS COULD START TO DEVELOP. LOW CONFIDENCE ON THE MVFR
CEILINGS. THE WINDS ARE ANTICIPATED TO BECOME NORTH TO NORTHEAST
AROUND 5 KNOTS.

OUTLOOK...
WEDNESDAY THROUGH THURSDAY...CONDITIONS VARYING BETWEEN VFR AND MVFR
IN PERIODS OF RAIN.

THURSDAY NIGHT...MAINLY VFR WITH A CHANCE OF SHOWERS.

FRIDAY THROUGH SATURDAY...MAINLY VFR.

&&

.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...
WEDNESDAY...NORTHERLY WIND GUSTS OF 25 TO 30 KNOTS ARE POSSIBLE.

WEDNESDAY NIGHT THROUGH FRIDAY NIGHT...NORTHWESTERLY WIND GUSTS
OF 25 TO 30 KNOTS ARE POSSIBLE.

SATURDAY...NO MARINE HEADLINES ARE ANTICIPATED.

&&

.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...IOVINO
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...IOVINO
AVIATION...GORSE/IOVINO
MARINE...GORSE/IOVINO




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