Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 311416
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1016 AM EDT SUN AUG 31 2014

.SYNOPSIS...
HIGH PRESSURE WELL OFF THE EAST COAST WILL MAINTAIN A SOUTHWESTERLY
FLOW OVER THE AREA THROUGH THE FIRST PART OF THE WEEK. A WEAK COLD
FRONT IS THEN EXPECTED TO MOVE ACROSS OUR AREA TUESDAY NIGHT AND
EARLY WEDNESDAY. HIGH PRESSURE WILL BUILD IN BEHIND THIS FRONT FOR
THE SECOND HALF OF THE WEEK. ANOTHER COLD FRONT MAY APPROACH FROM
THE WEST NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
NOT MUCH CHANGE NEEDED TO THE GRIDS AT THIS TIME. THE TIMING OF
THE POPS, BASED ON CURRENT REGIONAL RADAR AND DECENT HANDLING BY
THE 10Z HRRR, LOOK GOOD. DID DECREASE SKY COVER ACROSS THE
SOUTHERN HALF OF THE CWA THROUGH THE REMAINDER OF THE MORNING
BEFORE ANOTHER INCREASE IS EXPECTED UNDER A SELF DESTRUCTING
SKY...LOTS OF LOW-LEVEL MOISTURE AND EXCEEDING CONVECTIVE
TEMPERATURES. LATEST 12Z REGIONAL SOUNDINGS SHOW VERY WEAK MID-
LEVEL LAPSE RATES WITH SOME MID-LEVEL CAPPING IN PLACE...LESS OF
CAP TO OUR SOUTHWEST BUT SURPRISINGLY ALSO A LITTLE LESS MOISTURE.

ORIGINALLY OUR REGION WAS UNDER A SLIGHT RISK FOR SEVERE
THUNDERSTORMS, 15 PERCENT PROBABILITY, BUT AFTER COORDINATION WITH SPC,
BASED ON HOW BENIGN THE LAPSE RATES AND LESS CAPE THAN EXPECTED,
WE ARE IN SEE TEXT NOW. THIS MEANS THE PROBABILITY OF SEVERE
THUNDERSTORMS, MOSTLY IN THE FORM OF WET DOWNBURSTS FROM
PRECIPITATION LOADING, ARE LESS THAN BEFORE BUT NOT ENTIRELY OUT
OF THE QUESTION.

OTHERWISE, OUR REGION WILL MAINLY BE CAUGHT BETWEEN SYSTEMS
TODAY, AS AN UPPER-LEVEL RIDGE REMAINS SITUATED TO OUR SOUTH AND
SOUTHEAST WITH SURFACE HIGH PRESSURE TO THE EAST. MEANWHILE, AN
UPPER-LEVEL TROUGH WILL CONTINUE TO TRACK ACROSS THE GREAT LAKES
THEN ACROSS SOUTHERN ONTARIO CANADA. THIS WILL RESULT IN A DEEP
SOUTHWESTERLY FLOW, WHICH WILL PULL AN ABUNDANCE OF MOISTURE INTO
OUR REGION. AS A RESULT, A MORE HUMID DAY IS EXPECTED.

AS WE STEP FORWARD THROUGH THE DAY, ENOUGH HEATING COMBINED WITH
CLIMBING SURFACE DEW POINTS SHOULD RESULT IN ENOUGH INSTABILITY
/MLCAPE UP TO 1500 J/KG/ TO PRODUCE SHOWERS AND THUNDERSTORMS. THE
BULK OF THIS ACTIVITY IS EXPECTED TO DEVELOP TO OUR WEST NEAR A WEAK
FRONTAL BOUNDARY WITH ADDITIONAL DEVELOPMENT POSSIBLY NEAR A
DIFFERENTIAL HEATING ZONE. THE HEIGHT FALLS ARE WEAK THIS FAR EAST
AS THE SHORT WAVE TROUGH TRACKS TO OUR NORTH LATE IN THE DAY.
HOWEVER, AN INCREASE IN THE MID LEVEL FLOW TO NEAR 40 KNOTS WILL
INCREASE THE SHEAR WITH TIME. THIS SHOULD BE ENOUGH TO PROMOTE SOME
STORM ORGANIZATION WITH THE MAIN MODE BEING LINE SEGMENTS, IF WE
GET BETTER UPDRAFT GROWTH TO OCCUR. IN ADDITION, THE PW VALUES ARE
FORECAST TO INCREASE TO AROUND 2 INCHES WHICH WILL LEAD TO
DOWNPOURS. THESE DOWNPOURS MAY RESULT IN BRIEF POOR DRAINAGE
FLOODING, HOWEVER THE FLASH FLOOD THREAT GENERALLY LOOKS LOW AS
THERE SHOULD BE ENOUGH OF A STORM MOTION.

THE MOIST ENVIRONMENT COMBINED WITH ENOUGH INSTABILITY COULD ALSO
RESULT IN SOME STORMS PRODUCING FREQUENT LIGHTNING. GIVEN THE
FORECAST THERMODYNAMIC SETUP, SOME STORMS WILL BE CAPABLE OF
PRODUCING GUSTY TO PERHAPS LOCALLY DAMAGING WINDS. THIS GENERALLY
LOOKS TO BE FROM ABOUT THE INTERSTATE 95 CORRIDOR ON NORTH AND WEST
BY LATE AFTERNOON. WE THEREFORE MAINTAINED INCREASING POPS FROM WEST
TO EAST WITH THE WESTERN ZONES GOING TO LIKELY IN THE AFTERNOON, AND
WE ALSO ADDED SOME ENHANCED WORDING. MUCH OF THE EASTERN AND
SOUTHEASTERN ZONES MAY REMAIN DRY FOR THE BULK OF THE DAY.

AS FOR HIGH TEMPERATURES, WE USED AN EVEN BLEND OF THE NAM/GFS MOS
THEN ADJUSTED DOWN A LITTLE BIT FOR SOME AREAS WITH THE IDEA OF LOTS
OF CLOUDS PREVAILING.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM MONDAY/...
THE AFOREMENTIONED SHORT WAVE TROUGH IS FORECAST TO DAMPEN OUT AS IT
TRACKS WELL TO OUR NORTH TONIGHT. THERE IS STILL A TRAIL OF SHORT
WAVES ROLLING UP THE BACKSIDE OF THE UPPER-LEVEL RIDGE WITH ALSO A
WEAKENING FRONTAL BOUNDARY NEARING THE AREA. THE FORECAST SOUNDINGS
INDICATE THAT ENOUGH INSTABILITY IS MAINTAINED FOR AWHILE FOR SOME
SHOWERS AND THUNDERSTORMS TO CONTINUE THROUGH THE EVENING,
ESPECIALLY FROM THE INTERSTATE 95 CORRIDOR ON NORTH AND WEST. A
SOMEWHAT MORE PRONOUNCED SHORT WAVE MAY HELP TO FOCUS A CONVECTIVE
CLUSTER OVERNIGHT, HOWEVER WHERE THIS IS FOCUSED HAS LESS CERTAINTY
WITH IT ATTM. AS THE PW VALUES REMAIN RATHER HIGH, LOCAL DOWNPOURS
COULD PUT DOWN A DECENT AMOUNT OF RAIN HOWEVER ANY FLOOD THREAT
LOOKS BRIEF AND LOCALIZED.

AS MENTIONED ABOVE, SOME STRONG CONVECTION MAY OCCUR IN THE EVENING
WITH LOCALLY GUSTY WINDS POSSIBLE. THIS WOULD BE MORE TIED TO ANY
LINE SEGMENTS THAT ARE ABLE TO MAINTAIN THEMSELVES WITH PERHAPS SOME
ENHANCEMENT FROM WATER LOADED DOWNDRAFTS. OTHERWISE, A WEALTH OF
CLOUDS SHOULD BE AROUND THROUGH THE NIGHT FOR MUCH OF THE AREA ALONG
WITH MUGGY CONDITIONS.

AS FOR LOW TEMPERATURES, AN EVEN BLEND OF THE NAM/GFS MOS WAS
GENERALLY USED.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
UNSETTLED WEATHER IS EXPECTED ON MONDAY WITH CONVECTION STILL
POSSIBLE MOST AREAS THROUGH MOST OF THE DAY. LOCALLY HEAVY RAIN IS
POSSIBLE JUST ABOUT ANYWHERE...BUT LATEST GUIDANCE SUGGESTS NEAR AND
SOUTH AND EAST OF THE I-95 CORRIDOR MIGHT BE FAVORED. ANY FLOODING
SHOULD BE MORE URBAN AND POOR DRAINAGE FLOODING. WITH A CONTINUED
SOUTHWESTERLY FLOW, TEMPERATURES WILL PEAK 5 TO 10 DEGREES ABOVE
NORMAL FOR THE BEGINNING OF SEPTEMBER.

MONDAY NIGHT AND TUESDAY...A LULL IN THE PRECIPITATION IS EXPECTED
LATE MONDAY NIGHT THROUGH TUESDAY AFTERNOON. IF THERE`S ENOUGH
SUNSHINE...TEMPERATURES COULD PEAK OUT IN THE LOW 90S.

TUESDAY NIGHT...SHOWERS AND THUNDERSTORMS...SOME WITH LOCALLY HEAVY
RAIN...CAN BE EXPECTED AS A COLD FRONT SWINGS THROUGH THE AREA FROM
WEST TO EAST.

WEDNESDAY THROUGH FRIDAY...THE AIR MASS BEHIND THE COLD FRONT REALLY
WON`T BE TOO MUCH COOLER COURTESY OF A MID-LEVEL ZONAL FLOW, BUT IT
WILL BE DRIER AND MORE COMFORTABLE. HIGHS ALL THREE DAYS WILL BE
PRIMARILY IN THE LOW TO MID 80S, WHICH IS STILL ABOVE NORMAL.
BEAUTIFUL EARLY SEPTEMBER WEATHER.

SATURDAY...INCREASING CLOUDINESS AS THE DAY WEARS ON AS A COLD FRONT
APPROACHES FROM THE WEST. SHOWERS AND THUNDERSTORMS ARE POSSIBLE
WITH TEMPERATURES STILL ABOVE NORMAL.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

TODAY...AREAS OF MVFR TO LOCAL IFR CEILINGS WILL IMPROVE TO VFR
CEILINGS BY MIDDAY.

SOME SHOWERS AND THUNDERSTORMS ARE EXPECTED TO CONTINUE TO
DEVELOP TO OUR WEST AND OVERSPREAD OUR AREA THIS AFTERNOON. SOME
TIMING WAS INDICATED IN THE TAFS, WITH THUNDER ONLY MENTIONED AT
KABE TO KRDG DUE TO HIGHER CONFIDENCE AS OF NOW. THERE WILL BE
BRIEF TIMES OF MVFR/IFR VISIBILITIES ESPECIALLY WITHIN SHOWERS AND
THUNDERSTORMS AS DOWNPOURS ARE ANTICIPATED. SOUTH-SOUTHEAST WINDS
INCREASING TO GENERALLY 10-15 KNOTS AND BECOMING SOUTH-SOUTHWEST.

TONIGHT...SHOWERS AND THUNDERSTORMS SHOULD CONTINUE EASTWARD WITH
MUCH OF THE ACTIVITY IN THE EVENING HOURS. AS A RESULT, THERE WILL
BE TIMES OF MVFR/IFR DUE TO DOWNPOURS. IN ADDITION, SOME LIGHT FOG
COULD DEVELOP LATE IF SOME CLEARING OCCURS COMBINED WITH LIGHT
WINDS.

OUTLOOK...
MONDAY INTO MONDAY NIGHT...IFR CONDITIONS EXPECTED WITH SHOWERS AND
THUNDERSTORMS. COVERAGE OF PRECIPITATION DECREASING DURING THE
OVERNIGHT HOURS.

TUESDAY...GENERALLY VFR CONDITIONS EXPECTED DURING THE DAY.

TUESDAY NIGHT...IFR CONDITIONS POSSIBLE AS A COLD FRONT MOVES
THROUGH THE AREA.

WEDNESDAY THROUGH FRIDAY...GENERALLY VFR CONDITIONS EXPECTED.

&&

.MARINE...
A SOUTHERLY FLOW IS EXPECTED THROUGH TONIGHT AHEAD OF A WEAKENING
FRONTAL BOUNDARY AS A DISTURBANCE TRACKS WELL TO OUR NORTH. AS THIS
OCCURS, THE FLOW IS FORECAST TO INCREASE AND THIS OPENS THE DOOR TO
SOME MIXING. IT APPEARS THAT THE WARM AIR ADVECTING ACROSS THE AREA
WILL KEEP THE STRONGER WINDS ABOVE THE SURFACE. WHILE THERE CAN BE
SOME GUSTINESS ESPECIALLY NEARSHORE, IT GENERALLY LOOKS MARGINAL.
THE SOUTHERLY FLOW WILL ALSO ALLOW THE SEAS TO BUILD THROUGH
TONIGHT, HOWEVER GIVEN THE SOUTHERLY FLOW DIRECTION AND FETCH, WE
KEPT SEAS UP TO 4 FEET. THEREFORE, NO SMALL CRAFT ADVISORY HAS BEEN
ISSUED AT THIS TIME. SOME SHOWERS AND THUNDERSTORMS WILL ARRIVE LATE
THIS AFTERNOON AND TONIGHT, AND SOME STORMS COULD PRODUCE LOCALLY
GUSTY WINDS.

OUTLOOK...
MONDAY AND MONDAY NIGHT...WINDS AND SEAS SHOULD REMAIN JUST BELOW
SMALL CRAFT ADVISORY CRITERIA. GUSTIER WINDS POSSIBLE IN THE
VICINITY OF THUNDERSTORMS.

TUESDAY THROUGH THURSDAY...WINDS AND SEAS EXPECTED TO REMAIN BELOW
SCA CRITERIA. HOWEVER, SOME GUSTY WINDS ARE POSSIBLE WITH
THUNDERSTORMS TUESDAY NIGHT AND EARLY WEDNESDAY.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

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






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