037
FXUS61 KPHI 090744
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
345 AM EDT WED JUL 9 2008
SYNOPSIS
A COLD FRONT WILL CROSS THE REGION TODAY INTO TONIGHT, BRINGING A
CHANCE OF SHOWERS AND THUNDERSTORMS TO THE AREA. HIGH PRESSURE WILL
THEN BUILD IN BEHIND THE FRONT FOR THURSDAY AND AS A RESULT, A DRY
AND PLEASANT DAY IS IN STORE. THE HIGH WILL THEN REMAIN OVER THE
AREA KEEPING CONDITIONS DRY INTO LATE SUNDAY. ANOTHER COLD FRONT IS
THEN EXPECTED TO CROSS THE REGION LATER SUNDAY INTO MONDAY, BRINGING
ANOTHER CHANCE OF SHOWERS AND THUNDERSTORMS. HIGH PRESSURE WILL
THEN BUILD BACK IN THROUGH THE MIDDLE OF NEXT WEEK.
NEAR TERM /THROUGH TONIGHT/
THE LATEST SATELLITE IMAGERY SHOWS SOME HIGH CLOUDS TO THE NW AND
NOT MUCH ELSEWHERE, SO TODAY WILL START OUT CLEAR TO MOSTLY CLEAR.
HOWEVER, BY LATE MORNING (AT THE EARLIEST) OR EARLY AFTERNOON (AT
THE LATEST) A COLD FRONT WILL APPROACH FROM THE WEST BRINGING A
CHANCE OF SHOWERS OR TSTMS TO THE REGION. THE FRONT WILL PUSH
THROUGH THE REGION TONIGHT AND THE PRECIP CHANCES WILL CONTINUE
UNTIL THE FRONT CLEARS THE COAST. WITH ABUNDANT MOISTURE IN THE
ATMOSPHERE, THERE IS THE POTENTIAL FOR SOME HEAVY RAINERS. PW
VALUES ARE AOA 2.00 INCHES. HOWEVER, THE WIND PROFILE FROM BOTH THE
NAM/WRF AND GFS IS PRETTY MUCH UNIDIRECTIONAL FROM THE SW OR W ALL
TH WAY UP, WITH NOT MUCH VARIANCE IN SPEED. AS A RESULT, THERE IS
VIRTUALLY NO SHEAR. THE NAM/WRF CAPES ARE GENERALLY BETWEEN
500-1000 J/KG WITH THE GFS INDICATING SOME CAPES BETWEEN 1000-1500
J/KG. CERTAINLY, THE POTENTIAL FOR SOME SEVERE TSTMS IS THERE, BUT
WITH NOT A LOT OF CAPE AND VIRTUALLY NO SHEAR, CHANCES SEEM TO BE
MORE SCATTERED. THE BEST THREATS SEEM TO BE HEAVY RAIN AND SOME
DAMAGING WINDS.
SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/
THE COLD FRONT WILL CROSS THE REGION EARLY THURSDAY WITH ITS SHOWERS
AND TSTMS. THE NAM/WRF IS FASTER THAN THE GFS WITH THE PROGRESSION
OF THE FRONT, BRINGING AN END TO THE PRECIP BY 12Z THURSDAY. THE
GFS IS HAVING SOME CONVECTIVE FEEDBACK PROBS OVER THE MID ATLC AND
AS A RESULT, IT APPEARS TO BE HANGING UP THE FRONT A BIT MORE. THE
ECMWF IS FASTER THAN THE GFS, ALBEIT, NOT AS FAST AS THE NAM/WRF.
OF COURSE, THE ECMWF DOES NOT HAVE THE FEEDBACK ISSUE EITHER. AS A
RESULT, HAVE LEANED THE TIMING AWAY FROM THE GFS SOLN.
REGARDLESS OF WHICH MODEL IS ULTIMATELY CORRECT, THEY ALL AGREE IN
CLEARING THINGS OUT BY AFTERNOON AND THEN HIGH PRESSURE BUILDS IN.
HIGH TEMPERATURES WILL MAKE IT INTO THE MID TO UPPER 80S ACROSS THE
AREA, BUT DEW POINTS WILL BE IN THE 50S. HOW REFRESHING THAT WILL
FEEL AFTER ALL THE HUMIDITY OF LATE WITH DEW POINTS THAT HAD BEEN IN
THE 60S AND 70S...THERE WILL EVEN BE A DECENT NWLY WIND. WE DON'T
GET MANY DAYS LIKE THIS IN JULY! THURSDAY NIGHT LOOKS TO BE CLEAR
AND PLEASANT AS WELL.
LONG TERM /FRIDAY THROUGH WEDNESDAY/
HIGH PRESSURE IS EXPECTED TO BE CENTERED OVER THE REGION ON FRIDAY,
AND THE WEATHER LOOKS TO BE ABSOLUTELY SPECTACULAR AGAIN WITH A
GENERALLY CLEAR SKY TEMPS IN THE UPPER 80S WITH DEW POINTS IN THE
LOW 60S AND A WEST TO NORTHWEST WIND. THE HIGH REMAINS OVER THE
REGION ON SATURDAY BEFORE MOVING OFFSHORE ON SUNDAY, ALLOWING FOR A
RETURN SWLY FLOW AND INCREASING HUMIDITY. AN AREA OF LOW PRESSURE
WILL MOVE ACROSS ERN CANADA AND ITS ASSOCIATED CDFNT WILL MOVE
SLOWLY EASTWARD. THIS FRONT SHOULD CROSS THE REGION SUNDAY NIGHT
INTO MONDAY, BRINGING ANOTHER SHOT OF SHOWERS/TSTMS, BUT MOST OF THE
WEEKEND LOOKS TO BE DRY ATTM. THE GFS KEEPS THE FRONT OVER THE AREA
INTO EARLY MONDAY AS A FEW WAVES MOVE ALONG IT. HOWEVER, BY LATER
MONDAY, THE FRONT FINALLY DEPARTS AS HIGH PRESSURE OVER THE MIDWEST
BEGINS TO BUILD IN. THIS HIGH PRESSURE SYSTEM WILL BE THE DOMINANT
WX FEATURE THRU MIDWEEK, BRINGING DRY AND PLEASANT WX. WE SHOULD
NOT BE COMPLAINING AT ALL, AS IT IS JULY.
TEMPS ARE FCST TO BE AT OR SLIGHTLY ABOVE SEASONAL NORMS THRU THE
PERIOD.
AVIATION /06Z WEDNESDAY THROUGH SUNDAY/
OTHER THAN AN MVFR VISIBILITY AT KABE, ALL OF OUR TAF SITES WERE IN
THE VFR CATEGORY AT 0700Z. WITH THE CLEAR SKY AND RELATIVELY LIGHT
WIND, WE HAVE MENTIONED SOME MVFR VISIBILITY VALUES, AS WELL, FOR
KRDG, KTTN AND KMIV EARLY THIS MORNING. CONDITIONS SHOULD NOT BE
NEARLY AS LOW AS THEY WERE DURING THE PAST FEW MORNINGS. MEANWHILE,
KPHL, KPNE, KILG AND KACY SHOULD MAINTAIN ENOUGH OF A SOUTH TO
SOUTHWEST WIND TO PREVENT EVEN LIGHT FOG FROM DEVELOPING.
HIGH AND MID LEVEL CLOUDS WILL CONTINUE TO BUILD OVERHEAD FROM THE
WEST THIS MORNING. WHILE THERE WAS SOME LIGHT PRECIPITATION AS FAR
EAST AS CENTRAL PENNSYLVANIA AT 0700Z, THE LEADING BAND OF SHOWERS
WAS WEAKENING. HOWEVER, THERE WERE ADDITIONAL SHOWERS AND ISOLATED
THUNDERSTORMS EXTENDING WELL BACK INTO OHIO AND INDIANA, OUT AHEAD
OF A COLD FRONT DROPPING DOWN FROM THE NORTHWEST. IT DOES NOT
APPEAR AS THOUGH ANY PRECIPITATION WILL REACH OUR NORTHWESTERN TAF
SITES, KRDG AND KABE, UNTIL LATE THIS MORNING.
EVEN THOUGH THE COLD FRONT IS NOT EXPECTED TO REACH OUR REGION UNTIL
LATE TONIGHT, SHOWERS AND THUNDERSTORMS ARE ANTICIPATED FROM THIS
AFTERNOON INTO TONIGHT. WITH A NUMBER OF BOUNDARIES DEVELOPING IN
RESPONSE TO THE PRECIPITATION TO OUR WEST, TIMING ANY SHOWERS OR
THUNDERSTORMS AT OUR EIGHT TAFS SITES FOR TODAY IS DIFFICULT AT THIS
POINT. USING THE COMPUTER MODEL GUIDANCE, THE CURRENT LOCATION OF
THE PRECIPITATION, AND CLIMATOLOGY, WE HAVE TRIED TO NARROW DOWN THE
MOST LIKELY FOUR HOUR PERIOD FOR SHOWERS AND THUNDERSTORMS AT EACH
SITE. WE WILL EMPHASIZE THE POTENTIAL FOR PRECIPITATION AT KRDG AND
KABE FROM 1900Z TO 2300Z. FOR OUR TAF SITES ALONG THE DELAWARE
RIVER, INCLUDING KPHL, WE WILL USE THE TIME RANGE FROM 2200Z TO
0200Z. FOR KMIV AND KACY, WE WILL FOCUS ON 0000Z TO 0400Z. WE WILL
ALSO INCLUDE THE POSSIBILITY OF SHOWERS FOR A FEW HOURS ON EITHER
SIDE OF THOSE PERIODS. WE HAVE CONFINED THE PRECIPITATION TYPE TO
SHOWERS FOR NOW AND HAVE NOT MENTIONED ANY THUNDERSTORMS DUE TO THE
UNCERTAINTY IN TIMING. WE HAVE, HOWEVER, IMPLIED THE POTENTIAL FOR
THUNDERSTORMS BY INCLUDING CUMULONIMBUS.
OUTLOOK...
ONCE THE COLD FRONT PASSES, IT LOOKS LIKE A PERIOD OF MAINLY FAIR
WEATHER FOR THURSDAY, FRIDAY AND SATURDAY. ANOTHER COLD FRONT MAY
BEGIN TO APPROACH FROM THE NORTHWEST ON SUNDAY, BRINGING A CHANCE
FOR SHOWERS AND THUNDERSTORMS AT THAT TIME.
MARINE
WE HAVE DECIDED TO DROP THE SMALL CRAFT ADVISORY FROM OUR OCEAN
WATERS WITH THE EARLY MORNING ISSUANCE OF THE COASTAL WATERS
FORECAST. A SOUTH TO SOUTHWEST WIND OF 15 TO 20 KNOTS IS EXPECTED
FOR TODAY, WITH WAVES ON OUR OCEAN WATERS STAYING MAINLY IN THE 3 TO
4 FOOT RANGE.
A COLD FRONT THAT WAS LOCATED OVER THE GREAT LAKES REGION EARLY THIS
MORNING, WILL CONTINUE TO DROP TO THE SOUTHEAST AND IT SHOULD REACH
THE COASTAL WATERS OF NEW JERSEY AND DELAWARE LATE TONIGHT. HIGH
PRESSURE IS FORECAST TO FOLLOW FOR THURSDAY, FRIDAY AND SATURDAY,
BRINGING A PERIOD OF UNEVENTFUL WEATHER TO THE REGION. ANOTHER COLD
FRONT FROM THE NORTHWEST IS EXPECTED TO APPROACH ON SUNDAY, POSSIBLY
RESULTING IN AN INCREASE IN WIND SPEEDS FROM THE SOUTH AND
SOUTHWEST, ALONG WITH BUILDING SEAS. FOR NOW, IT APPEARS AS THOUGH
CONDITIONS WILL REMAIN BELOW SMALL CRAFT ADVISORY CRITERIA AT THAT
TIME.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
SYNOPSIS...NIERENBERG
NEAR TERM...NIERENBERG
SHORT TERM...NIERENBERG
LONG TERM...NIERENBERG
AVIATION...IOVINO
MARINE...IOVINO
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