Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 262341
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
741 PM EDT TUE AUG 26 2014

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OVER THE AREA THROUGH WEDNESDAY MORNING. A
COLD FRONT WILL MOVE FROM NORTHWEST TO SOUTHEAST ACROSS THE REGION
LATE WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT. HIGH PRESSURE RETURNS
THURSDAY AND FRIDAY. A WARM FRONT LIFTS THROUGH THE REGION SATURDAY
FOLLOWED BY A COLD FRONT APPROACHING FROM THE NORTHWEST SUNDAY INTO
MONDAY.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
A STRONG UPPER-LEVEL RIDGE WILL FLATTEN SOME OVERNIGHT AS A SHORT
WAVE TROUGH SLIDES ACROSS THE UPPER GREAT LAKES REGION. THIS SHORT
WAVE WILL DRIVE A COLD FRONT EASTWARD ASSOCIATED WITH A SURFACE
LOW THAT IS FORECAST TO TRACK WELL TO OUR NORTH ACROSS CANADA.
MEANWHILE, SURFACE HIGH PRESSURE FROM THE CENTRAL APPALACHIANS
NORTHEASTWARD WILL NARROW AND WEAKEN AS THE RIDGE FLATTENS. THE
HIGH WILL TEND TO SHIFT NORTHEASTWARD, ALLOWING A RETURN FLOW TO
BECOME BETTER ESTABLISHED ACROSS MUCH OF OUR AREA.

SINCE HIGH PRESSURE ALOFT AND AT THE SURFACE ARE THE DOMINATING
WEATHER FEATURES, CLEAR TO MOSTLY SKIES ARE EXPECT THROUGH THE
OVERNIGHT HOURS. THIS WILL ASSIST IN DECENT COOLING OF THE
BOUNDARY LAYER ONCE AGAIN, ALTHOUGH THE AIRMASS IS MODIFIED BUT
THE DEW POINTS WILL BE UP A BIT. THIS COMBINATION SHOULD RESULT IN
SOME PATCHY GROUND FOG ONCE AGAIN LATE, ESPECIALLY IN FIELDS AND
OTHER OPEN AREAS.

LOW TEMPERATURES WERE AN EVEN BLEND OF THE NAM/GFS MOS, ALTHOUGH
SOME UPWARD TWEAKS WERE MADE FOR THE HIGHLY URBANIZED AREAS SUCH AS
CENTER CITY PHILADELPHIA. THE HOURLY GRIDS WERE ADJUSTED WITH THE
LATEST OBSERVATIONS, THEN THE LAMP/LAV GUIDANCE WAS BLENDED IN TO
HELP ASSIST WITH TRENDS THROUGH THIS EVENING.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
THE UPPER-LEVEL RIDGE IS FORCED SOUTHWESTWARD SOME AS THE
AFOREMENTIONED SHORT WAVE TROUGH AMPLIFIES AS IT SLIDES ACROSS
SOUTHEASTERN CANADA AND THE EASTERN GREAT LAKES. AT THE SURFACE, A
WEAK COLD FRONT WILL BE ARRIVING DURING THE AFTERNOON.

THE MODEL GUIDANCE SHOWS A FAIRLY NARROW CORRIDOR OF HIGHER THETA-E
AIR SURGING AHEAD OF THE COLD FRONT. THIS IS ALSO DEPICTED NICELY
WITHIN THE MODEL GUIDANCE AS A PW PLUME OF 1.50 TO 1.80 INCHES.
DESPITE THIS CORRIDOR OF INCREASED MOISTURE, THERE DOES NOT APPEAR
TO BE A LOT OF FORCING WITH THE FRONT. THE FLOW ALOFT IS
WEST-NORTHWEST, AND WHILE SOME CONVERGENCE SHOULD OCCUR AT THE
SURFACE IT IS GENERALLY WEAK. THERE SHOULD BE SOME CONVECTIVE
DEVELOPMENT UPSTREAM WITHIN THE RIBBON OF HIGHER MOISTURE CONTENT
AND CLOSER TO SOME MORE NOTED HEIGHT FALLS, HOWEVER ACROSS OUR AREA
THIS IS NOT MUCH OF A FACTOR. THEREFORE, WE SLOWED DOWN THE POP
INCREASE SOME DURING THE AFTERNOON BUT DID MAINTAIN SOME SLIGHT CHC
TO LOW CHC POPS NORTH AND WEST OF INTERSTATE 95 BY LATE IN THE DAY.
THE FORECAST SOUNDINGS SOUTH AND EAST OF HERE SHOW MORE OF A CAP
OCCURRING THROUGH THE DAY. IF STORMS ARE ABLE TO ARRIVE ACROSS OUR
NORTHWEST ZONES EARLY ENOUGH, PERHAPS SOME PULSE TYPE UPDRAFTS COULD
RESULT GIVEN THE LIGHT ENOUGH WIND FIELD.

OTHERWISE, A HOT AND SOMEWHAT HUMID DAY IS ANTICIPATED AS 850 MB
TEMPERATURES TOP OUT NEAR +18C. THIS COMBINED WITH SOME WESTERLY
FLOW ALOFT SHOULD ALLOW TEMPERATURES TO REACH OR JUST EXCEED 90
DEGREES FOR SEVERAL INLAND LOCALES. SOME OF THE GUIDANCE CAME IN A
LITTLE COOLER, HOWEVER GIVEN THE AIRMASS JUST ABOVE THE SURFACE WE
STAYED RATHER CLOSE TO CONTINUITY FOR MUCH OF THE AREA.

HURRICANE CRISTOBAL IS FORECAST TO TRACK WELL EAST OF THE MID
ATLANTIC COAST LATER WEDNESDAY, HOWEVER BUILDING SWELLS WILL ARRIVE
FROM SOUTH TO NORTH. FOR MORE INFORMATION, SEE THE RIP CURRENT
SECTION BELOW.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
THE COLD FRONT IS EXPECTED TO ADVANCE SOUTHEASTWARD THROUGH THE
FORECAST AREA DURING THE EVENING, ALTHOUGH MODELS HAVE TRENDED
SLIGHTLY SLOWER WITH THE PROGRESSION OF THE FRONT AND THE FROPA MAY
BE DELAYED UNTIL OVERNIGHT FOR THE DELMARVA. AN ISOLATED SHOWER OR
TSTM POSSIBLE NEAR THE FRONT EARLY IN THE EVENING ACROSS THE HIGHER
TERRAIN BEFORE CONVECTION WANES AFTER SUNSET WITH THE LOSS OF
DAYTIME HEATING. THE PREDOMINANT IMPACT THE FROPA MAY HAVE IS A FEW
HOURS OF MOSTLY CLOUDY SKIES AS WELL AS A WIND SHIFT OUT OF THE NW
AND ARRIVAL OF COOLER/DRIER AIR IN ITS WAKE. THE OFFICIAL NHC
FORECAST FOR HURRICANE CRISTOBAL IS FOR THE CENTER TO STAY ABOUT 450
MILES OR SO EAST THE DELMARVA COAST WEDNESDAY NIGHT, WHICH IS WELL
OFFSHORE TO BRING ANY DIRECT IMPACT FROM THE TROPICAL CYCLONE TO THE
AREA.

HIGH PRESSURE BUILDS IN FROM THE GREAT LAKES THURSDAY. POST- FRONTAL
CAA REGIME WILL CONTINUE. FORECAST H8 TEMPS ARE 4-8 C LOWER ON
THURSDAY THAN ON WEDNESDAY, TRANSLATING TO MAX TEMPS THURSDAY IN THE
LOWER 80S (EXCEPT 70S IN THE MOUNTAINS). THESE TEMPERATURES COMBINED
WITH DEWPOINTS ONLY IN THE 50S WILL LEAD TO A PLEASANT LATE SUMMER
DAY. THE PRESSURE GRADIENT BETWEEN THE HIGH AND CRISTOBAL WILL
PRODUCE A NW WIND 10-15 MPH.

A QUIET WX PATTERN WILL CONTINUE THROUGH THE REMAINDER OF THE WORK
WEEK WITH HIGH PRESSURE OVERHEAD. TEMPS WILL BE RIGHT AT, IF NOT A
COUPLE OF DEGREES BELOW NORMAL THURSDAY NIGHT AND FRIDAY.

THE CENTER OF HIGH PRESSURE IS FORECAST TO SHIFT OFF THE NEW ENGLAND
COAST FRIDAY NIGHT INTO SATURDAY. WINDS AT THE SURFACE WILL BEGIN TO
VEER OUT OF THE SOUTHEAST AND EVENTUALLY SOUTH DURING THIS TIME. WAA
PATTERN WILL DEVELOP AS THE OLD FRONTAL BOUNDARY THAT MOVES THROUGH
WEDNESDAY AND STALLS TO OUR SOUTH THURSDAY/FRIDAY WILL LIFT BACK
NORTHWARD AS WARM FRONT DURING THE BEGINNING OF THE HOLIDAY WEEKEND.
THE RESULT WILL BE AN UPTICK IN TEMPS, HUMIDITY AND CLOUD COVER.
COULD SEE ISOLATED MORNING SHOWERS AND AFTERNOON SHOWERS/STORMS ON
SATURDAY WITH THE FROPA. ISENTROPIC LIFT IS RATHER SHALLOW/WEAK. NOT
EXPECTING A WASHOUT FOR SATURDAY.

THE WARM FRONT WILL LIFT NORTHWARD INTO NEW ENGLAND ON SUNDAY.
FARTHER SOUTH, THE HEAT AND HUMIDITY WILL CONTINUE TO INCREASE AS
OUR AREA BECOMES SITUATED DEEPER INTO THE WARM SECTOR. SIDED CLOSELY
WITH WPC GUIDANCE, WHICH INDICATES HIGHS AROUND 90F ON SUNDAY.
MEANWHILE A NORTHERN STREAM SHORTWAVE TROUGH IS PROGGED TO MOVE
EASTWARD THROUGH THE GREAT LAKES/MIDWEST AND NORTHEAST STATES DURING
THE SUNDAY-MONDAY PERIOD. THERE IS STILL UNCERTAINTY IN THE TRACK
AND TIMING OF THIS SYSTEM, WHICH IS COMMON THIS FAR OUT. THINK THE
12Z OPERATIONAL GFS IS TOO FAST WITH THE TROUGH AND WITH BREAKING
DOWN THE DOWNSTREAM UPPER RIDGE. ACCORDINGLY, KEPT THE HIGHEST
POPS SUNDAY ACROSS THE HIGHER TERRAIN IN THE NORTHWEST PORTION OF
THE CWA, BUT LOW OVERALL AS THE BEST LIFT SHOULD STILL RESIDE
NORTHWEST OF THE AREA. CHANCES FOR SHOWERS AND STORMS INCREASE
LABOR DAY AS A COLD FRONT TRIES TO MOVE INTO THE AREA. DRIER
WEATHER FOR TUESDAY BEHIND THE FRONT.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

OVERNIGHT...VFR OVERALL. SOME LOCALIZED FOG IS POSSIBLE TOWARD
MORNING, MAINLY AT KMIV AND KRDG. SOUTHERLY WINDS AROUND 5 KNOTS,
BECOMING LIGHT AND VARIABLE OR CALM.

WEDNESDAY....MAINLY VFR. A LATE DAY SHOWER OR THUNDERSTORM IS
POSSIBLE MAINLY NEAR KTTN, KABE AND KRDG. SOUTHWEST WINDS INCREASING
TO 5-10 KNOTS, HOWEVER TURNING SOUTHEASTERLY MAINLY AT KACY.

OUTLOOK...
WEDNESDAY EVENING...AN ISO SHRA OR TSRA THROUGH ABOUT SUNSET TO THE
N/W OF THE PHILLY TERMINALS. UNLESS THERE ONE OF THESE STORMS
MOVES DIRECTLY OVER A TERMINAL, VFR CONDITIONS EXPECTED.

THURSDAY THROUGH FRIDAY NIGHT...VFR AND DRY WITH HIPRES OVERHEAD.

SATURDAY THROUGH SUNDAY...SHRA AND TSRA CHANCES INCREASE AS THE
WEEKEND PROGRESSES. ATTM, BETTER PRECIP CHANCE BOTH DAYS WOULD
APPEAR TO BE CLOSER TO THE PA MTS OUT TOWARD RDG/ABE.

&&

.MARINE...
HIGH PRESSURE WILL SHIFT TO THE NORTHEAST AND WEAKEN OVERNIGHT,
THEN A WEAK COLD FRONT ARRIVES LATER WEDNESDAY. THIS WILL RESULT
IN A WEAK ONSHORE FLOW AIDED BY SEA/BAY BREEZE INTO THIS EVENING,
THEN THE FLOW SHOULD TURN MORE SOUTHWESTERLY. HOWEVER HURRICANE
CRISTOBAL IS FORECAST TO TRACK WELL EAST OF THE MID ATLANTIC COAST
LATER WEDNESDAY AND THIS SHOULD HELP KEEP AN EAST OR NORTHEAST
FLOW ACROSS OUR SOUTHERN OCEAN WATERS. THE CONDITIONS ARE EXPECTED
TO BE BELOW SMALL CRAFT ADVISORY THROUGH TONIGHT, THEN INCREASING
SWELLS ARRIVE DURING WEDNESDAY. AS THESE ARRIVE AND BUILD, A SMALL
CRAFT ADVISORY GOES INTO EFFECT STARTING AT 14Z ACROSS THE
SOUTHERN OCEAN ZONES THEN WORKING NORTHWARD. WE ARE EXPECTING SUB-
ADVISORY CONDITIONS ON DELAWARE BAY THROUGH WEDNESDAY.

OUTLOOK...

WEDNESDAY NIGHT AND THURSDAY...THE OUTER EFFECTS OF HURRICANE
CRISTOBAL WILL REACH OUR MARINE ZONES WEDNESDAY NIGHT. SCA ISSUED
FOR THE ATLANTIC ZONES FOR WEDNESDAY NIGHT AS SEAS ARE FORECAST TO
BUILD TO 5-7 FT. WINDS SHOULD FOR THE MOST PART REMAIN UNDER 25 KT,
SO SCA FOR HAZARDOUS SEAS WAS ISSUED. HOWEVER, A BRIEF NW WIND SURGE
THAT APPROACHES THE SCA THRESHOLD IS POSSIBLE BEHIND THE COLD FRONT
EARLY THURSDAY MORNING. LONG PERIOD SWELLS NEAR 15 SECONDS ARE ALSO
EXPECTED. SEAS SHOULD GRADUALLY SUBSIDE THURSDAY BUT THE SCA WILL
LIKELY NEED TO BE EXTENDED INTO THIS PERIOD.

THURSDAY NIGHT THROUGH SUNDAY...SEAS CONTINUE TO SUBSIDE AS
CRISTOBAL MOVES FARTHER AWAY FROM THE EAST COAST. NO MARINE
HEADLINES EXPECTED THROUGH THE WEEKEND.

&&

.RIP CURRENTS...

FOR WEDNESDAY, HURRICANE CRISTOBAL IS FORECAST TO TRACK WELL EAST OF
THE MID ATLANTIC COAST. HOWEVER, BUILDING SWELLS WILL RADIATE
OUTWARD FROM THE HURRICANE AND AFFECT OUR COASTAL AREAS. AS OF NOW,
WAVES IN THE SURF ZONE LOOK TO BUILD TO 4 TO 6 FEET, POSSIBLY TO 7
FEET WEDNESDAY NIGHT. WHILE WIND IS NOT EXPECTED TO BE AN ISSUE,
RATHER LONG PERIOD SWELLS WILL CREATE ROUGH CONDITIONS WITH A
STRONGER CURRENT. AS A RESULT, A HIGH RISK OF DANGEROUS RIP
CURRENTS WILL BE ISSUED FOR WEDNESDAY.

WHILE THE RIP CURRENT RISK MAY NOT BE QUITE AS HIGH ON THURSDAY
AS WEDNESDAY, IT WILL BE ENHANCED NONETHELESS AS CRISTOBAL MOVES
EVEN FARTHER OUT TO SEA.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...HIGH RIP CURRENT RISK FROM WEDNESDAY MORNING THROUGH WEDNESDAY
     EVENING FOR NJZ014-024>026.
DE...HIGH RIP CURRENT RISK FROM WEDNESDAY MORNING THROUGH WEDNESDAY
     EVENING FOR DEZ004.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 10 AM WEDNESDAY
     TO 6 AM EDT THURSDAY FOR ANZ452>455.
     SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS FROM 2 PM WEDNESDAY TO
     6 AM EDT THURSDAY FOR ANZ450-451.

&&

$$
SYNOPSIS...KLEIN
NEAR TERM...GORSE/MIKETTA
SHORT TERM...GORSE
LONG TERM...KLEIN
AVIATION...GORSE/KLEIN
MARINE...GORSE/KLEIN
RIP CURRENTS...GORSE/MIKETTA







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