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000
FXUS61 KPHI 220139
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
939 PM EDT MON APR 21 2014

.SYNOPSIS...
A WEAK RIDGE OF HIGH PRESSURE JUST OFF THE MID- ATLANTIC COAST
TONIGHT WILL GIVE WAY ON TUESDAY TO A COLD FRONT APPROACHING FROM
THE WEST. THE FRONT WILL CROSS THE AREA AND MOVE OFFSHORE TUESDAY
EVENING FOLLOWED BY HIGH PRESSURE BUILDING OVER THE REGION ON
WEDNESDAY THROUGH THURSDAY. THE HIGH COMBINED WITH LOW PRESSURE
EAST OF NEW ENGLAND WILL RESULT IN GUSTY NORTHWEST WINDS. ANOTHER
FRONTAL SYSTEM WILL CROSS THE AREA FRIDAY OR FRIDAY NIGHT FOLLOWED
BY MORE HIGH PRESSURE AND FAIR WEATHER FOR THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
930 PM UPDATE...BIGGEST CHANGE WAS FOR THE POCONOS AND
SOUTHEASTERN PA. NEARLY ALL OF THE SHORT RANGE MODELS CONTINUE TO
WELL OVER FORECAST DEW POINT TEMPERATURES WEST OF THE I95
CORRIDOR. WHILE WE SHOULD HAVE INCREASING MOISTURE ADVECTION IN
THE MID AND UPPER LEVELS THROUGH THE NIGHT, DO NOT SEE MUCH LOW
LEVEL MOISTURE ADVECTION, ASIDE FROM THE TYPICAL NOCTURNAL
INCREASE DUE TO DECOUPLING. THUS, IN ADDITION TO LOWERING DEW
POINT TEMPERATURES IN THIS AREA, HAVE ALSO SLIGHTLY DECREASED LOWS
GIVEN THE DRIER THAN EXPECTED AIR. OTHERWISE...NO OTHER
SIGNIFICANT CHANGES TO THE FORECAST.

PREVIOUS NEAR TERM DISCUSSION...CONTINUED FAIR AND QUIET WEATHER
IS EXPECTED THIS EVENING AND TONIGHT AS WEAK SURFACE HIGH PRESSURE
EASES FARTHER OFFSHORE AND AN AREA OF LOW PRESSURE TRACKS EAST
ACROSS THE GREAT LAKES. ITS ASSOCIATED COLD FRONT WILL BE
APPROACHING OUR REGION GOING INTO TUESDAY, BUT THE FRONT WILL
REMAIN WELL TO OUR WEST THROUGH THE OVERNIGHT, ONLY NEARING THE
APPALACHIANS AND FAR WESTERN PA BY AROUND DAYBREAK TUESDAY.

THROUGH THE OVERNIGHT HOURS, FORECAST SOUNDINGS INDICATE INCREASING
MOISTURE THROUGH THE COLUMN, WITH MORE HIGH/MID CLOUDS SPREADING
INTO OUR AREA FROM WEST TO EAST, ESPECIALLY AFTER MIDNIGHT.
OTHERWISE, A DRY FORECAST IS MAINTAINED THROUGH THE NIGHTTIME AND
EARLY MORNING HOURS, WITH THE FRONT STILL WELL OFF TO OUR WEST.
TEMPERATURES WILL BE NOTICEABLY MILDER THAN LAST NIGHT, WITH THE
INCREASING CLOUDS AND LIGHT SOUTHERLY TO SOUTHWEST WINDS IN ADVANCE
OF THE FRONT. FOR THE MOST PART, WE TOOK A BLEND OF MET/MAV GUIDANCE
WITH SOME LOCAL ADJUSTMENTS AND ANTICIPATE MINIMUM TEMPERATURES
MAINLY IN THE 40S ACROSS THE REGION.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
THROUGH THE DAYTIME TUESDAY, SURFACE LOW PRESSURE IS FORECAST TO
PROGRESS EASTWARD FROM THE GREAT LAKES TO THE NEW ENGLAND STATES
BY EVENING, WITH ITS ASSOCIATED COLD FRONT CROSSING OUR REGION
DURING THE AFTERNOON TO EVENING HOURS. HIGHEST POPS ARE CENTERED
AROUND THIS TIMEFRAME, WITH ONLY CHANCE TO SLIGHT CHANCE POPS FROM
WEST TO EAST THROUGH THE MORNING HOURS. SLIGHT CHANCE THUNDER WAS
KEPT ACROSS THE FORECAST AREA FOR THE AFTERNOON TO EVENING WITH
THE FRONTAL PASSAGE, AS MODEL GUIDANCE CONTINUES TO INDICATE SOME
INSTABILITY. THE PASSAGE OF THIS FRONT THROUGH OUR AREA CONTINUES
TO LOOK RATHER PROGRESSIVE WITH FAIRLY LIMITED MOISTURE. THE GFS,
NAM, AND ECMWF ALL GENERALLY HAVE AROUND A QUARTER OF AN INCH OR
LESS QPF. IF ANY T-STORMS DO DEVELOP, SOMEWHAT HIGHER AMOUNTS MAY
OCCUR.

FOR TEMPERATURES, MILD SOUTHWESTERLY WINDS AHEAD OF THE FRONT AND
FORECAST 925/850MB TEMPS LOOK TO SUPPORT DAYTIME HIGHS INTO THE
LOWER 70S FOR MUCH OF THE REGION, WITH SOMEWHAT COOLER READINGS
THROUGH THE HIGHER TERRAIN IN OUR NORTHWEST ZONES AND ALONG THE
COAST.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
AT THE START OF THE LONG-TERM...00Z WED...A COLD FRONT IS FCST TO
EXTEND N TO S ACROSS NJ AND DELMARVA. ASSOCD SHOWERS WILL BE OVER
THE AREA AND A LITTLE BIT OF LINGERING CAPE IS EXPECTED SO HAVE
LEFT IN THE MENTION OF ISOLD TSTMS FOR A COUPLE OF HOURS AFTER
00Z. PROB OF ANY THUNDER WILL BE RAPIDLY DECREASING AND ALL PRECIP
SHOULD CLEAR THE AREA FROM W TO E BY MIDNIGHT WITH JUST A
LINGERING CHANCE OF SHOWERS OVER FAR NW NJ AND THE POCONOS. STRONG
LOW-LVL COLD ADVECTION WILL OCCUR OVERNIGHT BEHIND THE FRONT.

ON WED...THE SFC LOW ASSOCD WITH THE COLD FRONT IS FCST TO DEEPEN
EAST OF NEW ENGLAND AS HIGH PRES BUILDS IN FROM THE OH VLY. THE STG
PRES GRADIENT WILL MAINTAIN GUSTY NW WINDS AND COLD ADVECTION WITH
MAX TEMPS 10 TO 15 DEG F COOLER THAN ON TUESDAY. WITH GOOD PBL
MIXING AND 850 HPA WINDS 40 TO 50 KT...SOME WIND GUSTS IN THE 30
TO 35 KT RANGE SEEM LIKELY FOR WEDNESDAY DAYTIME. THIS WINDY
PATTERN WILL CONTINUE THROUGH WED NIGHT AND THURSDAY THO WITH THE
USUAL NOCTURNAL DECREASE AND NOT QUITE AS STRONG ON THURSDAY AFTN
AS THE HIGH PRES RIDGE MOVES CLOSER TO THE MID-ATLANTIC COAST. MAX
TEMPS SHOULD RECOVER SOMEWHAT CLOSE TO NORMAL ON THURSDAY IN SPITE
OF THE WIND.

THE HIGH PRES RIDGE IS FCST TO MOVE OFF THE MID-ATLANTIC COAST ON
FRIDAY AHEAD OF ANOTHER SHRTWV TROF AND ASSOCD FRONTAL SYS
CROSSING THE AREA FRIDAY OR FRIDAY NIGHT. AT THIS RANGE THE TIMING
IS MORE UNCERTAIN. FOR NOW WE HAVE THE HIGHER CHC POPS ON FRIDAY
INTO FRIDAY NIGHT WITH LINGERING CHC POPS ON SAT OVER NRN NJ AND
ADJACENT PA. CONFIDENCE IN THIS IS NOT TOO HIGH AT THE MOMENT.
COLD ADVECTION BEHIND THE FRONT SHOULD RESULT IN COOLER TEMPS FOR
THE WEEKEND BUT MAINLY FAIR SKIES LATER ON SAT AND INTO SUN.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

FOR THE 00Z TAFS...PRIMARILY VFR CONDITIONS ARE EXPECTED THROUGH
THE TAF PERIOD. FOR TONIGHT, THERE IS A RISK OF BR DEVELOPING AT
KMIV...AND POSSIBLY KACY WHILE WINDS ARE LIGHT AND VARIABLE,
BEFORE THEY TURN TO A MORE SW DIRECTION NEAR SUNRISE. EXPECT
INCREASING HIGH CLOUDS THROUGH THE OVERNIGHT INTO MORNING HOURS.
SHOWERS, AND AN ASSOCIATED COLD FRONT WILL BEGIN TO APPROACH THE
REGION AFTER 15Z, SPREADING FROM WEST TO EAST THROUGH THE
AFTERNOON. GENERALLY VFR CONDITIONS ARE EXPECTED, THOUGH SOME
LOCALIZED MVFR CONDITIONS ARE POSSIBLE IN HEAVIER SHRA.  WHILE
ISOLATED THUNDER IS NOT OUT OF THE QUESTION AS THERE WILL BE SOME
INSTABILITY, CONFIDENCE WAS NOT HIGH ENOUGH AT THIS TIME TO INCLUDE
THUNDER IN THE TAFS.

OUTLOOK...
TUESDAY NIGHT...SOME SCATTERED SHOWERS WITH LOCALLY MVFR CONDS IN
THE EVENING...THEN IMPROVING TO GENERALLY VFR OVERNIGHT.

WEDNESDAY THROUGH THURSDAY...VFR CONDITIONS PREVAILING BUT VERY
GUSTY NW WINDS...ESPECIALLY ON WEDNESDAY.

FRIDAY THROUGH SATURDAY...MAINLY VFR BUT LOCALLY MVFR IN SCATTERED
SHOWERS.

&&

.MARINE...
930 PM UPDATE...WAVE HEIGHTS AT BUOY 44009 REMAIN NEAR OR JUST
ABOVE 5 FT, SO THE SMALL CRAFT ADVISORY REMAINS IN EFFECT UNTIL
MIDNIGHT. WAVE HEIGHTS ARE EXPECTED TO SLOWLY DECREASE OVER THE
NEXT FEW HOURS, AND SHOULD BE BELOW 5 FT AFTER MIDNIGHT.

PREVIOUS MARINE DISCUSSION...AT LATE-DAY, SOME ENHANCED SEAS
STILL EXIST ON OUR COASTAL WATERS, WITH MAINLY THE OUTER WATERS
STILL REACHING IN THE 5 TO 6 FOOT RANGE, INCLUDING BUOY 44009. WE
WILL CONTINUE WITH THE CURRENT SMALL CRAFT ADVISORY FOR OUR
COASTAL WATERS, WHICH EXCLUDES OUR NORTHERNMOST ZONE FROM
MANASQUAN INLET NORTHWARD TO SANDY HOOK. WHILE THE SEAS ARE
DIMINISHING, GUIDANCE STILL SHOWS A FEW MORE HOURS INTO THIS
EVENING OF ELEVATED SEAS. MEANWHILE, WINDS ARE BELOW SCA CRITERIA
AT 15 KNOTS OR LESS, AND THEY WILL REMAIN SO THROUGH TONIGHT.

ONCE SEAS SUBSIDE LATER TONIGHT, THE OVERNIGHT PERIOD AND THROUGH
MOST OF THE DAYTIME TUESDAY WILL BE AT SUB-SCA LEVELS FOR OUR
COASTAL WATERS AND DELAWARE BAY AS A COLD FRONT SLOWLY APPROACHES
FROM THE WEST. SCATTERED SHOWERS WITH ISOLATED THUNDERSTORMS WILL
BECOME MORE LIKELY ACROSS THE WATERS DURING THE LATE AFTERNOON TO
EVENING HOURS ON TUESDAY.

OUTLOOK...

TUESDAY NIGHT THROUGH THURSDAY...NORTHWEST WINDS GUSTING 25 TO 30
KT. SOME GALE FORCE GUSTS ARE POSSIBLE ON WEDNESDAY.

FRIDAY AND SATURDAY...NO MARINE HEADLINES ARE ANTICIPATED AT THIS
TIME.

&&

.FIRE WEATHER...
SOME FIRE WEATHER DANGER MAY BE PRESENT ON WEDNESDAY AND THURSDAY.
GUSTY NORTHWEST WINDS WILL BE PRESENT BOTH DAYS BUT SOMEWHAT
STRONGER ON WEDNESDAY. HOWEVER...AT THIS TIME IT LOOKS LIKE RH
VALUES MAY STAY ABOVE 30 PERCENT ON WEDNESDAY. RH WILL BE LOWER ON
THURSDAY WITH ADDITIONAL DRYING AFTER TUESDAYS PRECIP...AND STILL
GUSTY NW WINDS.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ451>455.

&&

$$
SYNOPSIS...AMC
NEAR TERM...JOHNSON/KLINE
SHORT TERM...KLINE
LONG TERM...AMC
AVIATION...AMC/JOHNSON/KLINE
MARINE...AMC/JOHNSON/KLINE
FIRE WEATHER...AMC