Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 191955
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
355 PM EDT FRI SEP 19 2014

.SYNOPSIS...
HIGH PRESSURE WILL SHIFT OFFSHORE TONIGHT. A WARM FRONT WILL LIFT TO
OUR NORTHWEST SATURDAY, THEN A COLD FRONT IS EXPECTED TO AFFECT THE
AREA LATE SUNDAY INTO SUNDAY NIGHT. THIS FRONT WILL MOVE TO OUR
SOUTH, WHILE HIGH PRESSURE BEGINS TO BUILD IN FROM THE WEST ON
MONDAY. A WEAKENING FRONT MAY BRIEFLY AFFECT THE AREA ON TUESDAY,
BEFORE THE HIGH FULLY BUILDS ACROSS THE AREA FOR MUCH OF THE
REMAINDER OF THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
A 1030 MB SURFACE HIGH WAS CENTERED OVER NEW ENGLAND THIS AFTERNOON.
THE HIGH WILL SHIFT EASTWARD TOWARD THE GULF OF MAINE THROUGH THIS
EVENING BEFORE MOVING FARTHER OFFSHORE LATE TONIGHT. EASTERLY FLOW
AROUND THE HIGH THIS AFTERNOON HAS DRAWN RELATIVELY COOL/MOIST
MARINE LAYER INLAND.

STRATOCU HAS BEEN PERSISTENT SO FAR THIS AFTERNOON OVER THE SOUTHERN
HALF OF NJ- WHERE MOISTURE REMAINS TRAPPED AT THE TOP OF THE
BOUNDARY LAYER. THERE IS A BRIEF POTENTIAL FOR PARTIAL CLEARING
TOWARD SUNSET BUT EXPECT CLOUDS TO REDEVELOP TONIGHT UNDER CONTINUED
ONSHORE FLOW. FARTHER INLAND,MARINE LAYER NOT AS WELL ESTABLISHED
AND STRATOCU HAS BEEN ABLE TO SCT OUT THIS AFTERNOON. HOWEVER,
CLOUDS OVER VA WILL SPREAD INTO EASTERN PA THROUGH TONIGHT AS
SOUTHERLY FLOW AND ISENTROPIC LIFT NEAR H8 STRENGTHENS AROUND THE
WESTERN PERIPHERY OF THE HIGH.

OFFICIAL MIN TEMP FORECAST FALLS ON THE WARMER ENVELOPE OF GUIDANCE
AS RADIATIONAL COOLING SETUP NOT IDEAL OWING TO THE INCREASING CLOUD
COVER THAT IS EXPECTED AND THE ONSHORE FLOW. THERE MAY BE A BETTER
SETUP FOR RADIATIONAL COOLING THIS EVENING BEFORE THE CLOUDS ARRIVE
ACROSS THE FAR NORTH. AREAS SUCH AS THE LEHIGH VALLEY, POCONOS AND
NORTHWEST NJ HAVE A POTENTIAL TO SEE FOG DEVELOP OVERNIGHT.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
HIGH PRESSURE WILL MOVE FARTHER OFFSHORE INTO THE NORTHERN ATLANTIC
WATERS ON SATURDAY. AN AREA OF LOW PRESSURE IS FORECAST TO TRACK
NORTH OF THE GREAT LAKES WHILE ANOTHER LOW PRESSURE SYSTEM DEVELOPS
OFF THE SOUTHEAST COAST. THE PATTERN IN BETWEEN THESE TWO SYSTEMS
WILL ALLOW THE ABOVE MENTIONED HIGH OVER THE ATLANTIC TO RIDGE BACK
WESTWARD INTO THE MID-ATLANTIC STATES.

SOUTHERLY FLOW AROUND THE PERIPHERY OF THE HIGH WILL PROMOTE WAA IN
THE LOW LEVELS. THIS PATTERN WILL RESULT IN MAX TEMPS THAT ARE 5-10F
WARMER ON SATURDAY THAN TODAY. SATURDAY MAY POTENTIALLY BE THE FIRST
DAY WITH ABOVE NORMAL TEMPS SINCE SEP 11, ALBEIT NOT MUCH MORE THAN
A COUPLE OF DEGREES ABOVE.

MODEL BUFKIT SOUNDINGS DEPICT A SATURATED BOUNDARY LAYER INITIALLY
SATURDAY MORNING AS A RESULT OF THE ONSHORE FLOW AT THE START OF THE
PERIOD. THE 12Z NAM TRIES TO MIX OUT MOISTURE AND RESULTANT CLOUDS
RATHER QUICKLY (BY 15Z) ACROSS THE ENTIRE CWA WHILE THE 12Z GFS
INDICATES A MUCH CLOUDIER SOLUTION ALONG AND EAST OF THE FALL LINE
THRU MUCH OF THE DAY AS MARINE AIR IS STUBBORN TO MIX OUT. DEEPER
MOISTURE IN THE COLUMN AS FORECAST BY THE 12Z WOULD INDICATE THE
POTENTIAL FOR SHOWERS TO DEVELOP NEAR THE COAST WITH THE ONLY
DISCERNIBLE FORCING MECHANISM BEING LOW-LEVEL ISENTROPIC LIFT. KEPT
POPS VERY LOW DUE TO THE UNCERTAINTY AND CONFINED SLIGHT CHANCE FOR
SHOWERS TO COASTAL LOCALES SINCE MOISTURE FLUX IF FORECAST TO BE
GREATEST OFFSHORE.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
SATURDAY NIGHT, HIGH PRESSURE PULLS AWAY TO OUR NORTHEAST AHEAD OF
THE APPROACHING COLD FRONT. AT THE SAME TIME, AN AREA OF LOW
PRESSURE WILL BE MOVING ALONG THE EAST COAST NEAR THE CAROLINA
COASTS. THE LOW WILL MOVE NORTHWARD AND PASS EAST OF OUR AREA, BUT
WILL LIKELY NOT PASS CLOSE ENOUGH TO OUR AREA TO BRING ANY
SIGNIFICANT IMPACTS BEFORE THE FRONT APPROACHES AND PUSHES IT
NORTHEASTWARD. WE MAY HAVE ANOTHER POSSIBILITY FOR LOW CLOUDS AND
FOG AND/OR DRIZZLE AS THE LOW APPROACHES SATURDAY NIGHT AND THE
LOW LEVELS MOISTEN. SO WE HAVE ADDED PATCHY FOG/DRIZZLE FOR
SATURDAY NIGHT/SUNDAY MORNING.

THE FRONTAL BOUNDARY SHOULD BE ENTERING OUR WESTERN AREAS DURING
SUNDAY AFTERNOON, BEFORE SWEEPING ACROSS OUR AREA SUNDAY EVENING
AND SUNDAY NIGHT. MODELS HAVE THE HIGHEST POPS AND QPF MOSTLY TO
OUR WEST DURING THE DAY, BEFORE LOWERING AS THE FRONT MOVES
THROUGH OUR AREA SUNDAY EVENING. SO WE WILL HAVE HIGHEST RAIN
CHANCES SUNDAY AFTERNOON ACROSS THE NORTHWESTERN AREAS,
DIMINISHING TO LOW END CHANCE SUNDAY EVENING. THERE IS SOME
INSTABILITY ACROSS THE AREA AND ESPECIALLY TO THE WEST DURING THE
DAY, BUT THE QUESTION IS WHETHER OR NOT WE LOSE THE INSTABILITY
BEFORE THE ACTIVITY REACHES OUR AREA. WE WILL MAINTAIN THE SLIGHT
CHANCE OF THUNDERSTORMS AS THERE IS THE POSSIBILITY FOR SOME
ISOLATED CONVECTION.

ON MONDAY, THE FRONT WILL BE MOVING OUT TO SEA, WHILE HIGH PRESSURE
BEGINS BUILDING IN FROM THE WEST ACROSS THE AREA THROUGH MONDAY
NIGHT. A WEAKENING FRONTAL BOUNDARY MAY BRIEFLY AFFECT THE AREA ON
TUESDAY, BUT FOR NOW THE FRONT LOOKS LIKE IT SHOULD BE A MOSTLY DRY
FRONTAL PASSAGE.

THEN HIGH PRESSURE FULLY BUILDS BACK ACROSS THE AREA FOR MUCH OF
THE REMAINDER OF THE WEEK, WHICH WILL PROVIDE DRY WEATHER ACROSS
THE AREA. ACTUALLY, THE FRONTAL PASSAGE SUNDAY/SUNDAY NIGHT LOOKS
LIKE OUR ONLY CHANCE OF RAIN FOR THE ENTIRE EXTENDED PERIOD, SO
LETS HOPE WE GET SOMETHING FROM IT.

TEMPERATURES ON SUNDAY WILL BE THE WARMEST OF THE EXTENDED WITH
TEMPERATURES 5-10 ABOVE NORMAL. THEN TEMPERATURES RETURN CLOSER
TO NORMAL OR FOR THE REMAINDER OF THE PERIOD.

&&

.AVIATION /19Z FRIDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

CIGS HAVE LIFTED TO VFR AT ALL TERMINALS AS OF 19Z. THIS MARINE
STRATOCU ARE FORECAST TO REMAIN BETWEEN 3-5 KFT THRU THIS EVE BEFORE
CIGS LOWER OVERNIGHT. GUIDANCE IS IN GOOD AGREEMENT WITH MVFR CIGS
DEVELOPING AFTER 06Z AND CONTINUING THRU DAYBREAK. THERE IS MORE
UNCERTAINTY CONCERNING HOW QUICKLY LOW CLOUDS ERODE AND CIGS IMPROVE
TO VFR. THE MARINE LAYER WILL GRADUALLY MIX OUT FROM WEST TO EAST
DURING THE LATE MORNING AND AFTERNOON ONCE LOW-LEVELS WINDS VEER OUT
OF THE SOUTH. CURRENT THINKING IS IMPROVEMENT TO VFR CIGS MAY NOT
OCCUR UNTIL CLOSER TO MIDDAY FOR MOST TERMINALS, WHICH IS LATER THAN
INDICATED BY THE 12Z NAM.

OUTLOOK...

SATURDAY NIGHT...LOWER CIGS AND/OR VSBYS POSSIBLE WITH STRATUS/FOG
DEVELOPMENT OVERNIGHT SATURDAY/SUNDAY MORNING.

SUNDAY-SUNDAY NIGHT...LOWER CONDITIONS POSSIBLE IN THE MORNING THE
BECOMING VFR DURING THE DAY. A COLD FRONT APPROACHES LATE IN THE DAY
INTO SUNDAY NIGHT WITH SCATTERED SHOWERS/THUNDERSTORMS AND LOWER
CONDITIONS POSSIBLE.

MONDAY-WEDNESDAY...MOSTLY VFR. GUSTY W-NW WINDS 15-20 KNOTS MONDAY.
LESS GUSTY TUESDAY AND WEDNESDAY.

&&

.MARINE...
NORTHEAST WINDS WILL CONTINUE BETWEEN 10-20 KT THRU THE REMAINDER OF
THE AFTERNOON BEFORE WINDS SHIFT OUT OF THE EAST TONIGHT. BUOYS
AROUND THE AREA SHOW SEAS HAVE INCREASED TO 5 FT AND THUS HAVE
EXPANDED SCA TO INCLUDE ALL ATLANTIC MARINE ZONES THRU 2 AM. WINDS
AND SEAS WILL GRADUALLY RELAX IN THE NORTHERN ZONES OVERNIGHT AS THE
AXIS OF HIGH PRESSURE SHIFTS OVERHEAD. SCA REMAINS IN EFFECT THRU
SATURDAY SOUTH OF MANASQUAN INLET WITH 5 FT SEAS EXPECTED.

OUTLOOK...
SATURDAY NIGHT-SUNDAY...SMALL CRAFT ADVISORY EXTENDED AS SEAS LOOK
TO LINGER INTO EARLY SATURDAY NIGHT BEFORE SUBSIDING LATER IN THE
NIGHT INTO SUNDAY.

SUNDAY NIGHT...A COLD FRONT APPROACHES SUNDAY NIGHT WITH SHOWERS AND
POSSIBLY THUNDERSTORMS WITH INCREASING WINDS. WINDS AND WAVES MAY
APPROACH SMALL CRAFT ADVISORY LEVELS BEHIND THE COLD FRONT OVERNIGHT
INTO EARLY MONDAY MORNING..

MONDAY-WEDNESDAY...CONDITIONS EXPECTED TO TO DROP BELOW ADVISORY
LEVELS DURING THE DAY MONDAY AND STAY BELOW THROUGH WEDNESDAY.

&&

.RIP CURRENTS...
WITH LONG PERIOD SWELLS STILL PRESENT TODAY, A TIGHTENING GRADIENT
AND INCREASING WAVE HEIGHTS, IN HOUSE GUIDANCE CONTINUES TO SUGGEST
A MODERATE RISK TODAY FOR NJ AND DE.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT SUNDAY FOR ANZ451>455.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT SATURDAY FOR ANZ450.

&&

$$
SYNOPSIS...ROBERTSON
NEAR TERM...KLEIN
SHORT TERM...KLEIN
LONG TERM...ROBERTSON
AVIATION...KLEIN/ROBERTSON
MARINE...KLEIN/ROBERTSON
RIP CURRENTS...KRUZDLO



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