079
FXUS61 KPHI 042326
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
726 PM EDT SAT JUL 4 2009
SYNOPSIS
BROAD LOW PRESSURE, LOCATED OVER THE LOWER SAINT LAWRENCE RIVER
VALLEY THIS EVENING, WILL CONTINUE TO MOVE TO THE EAST. MEANWHILE,
WEAK HIGH PRESSURE WILL REMAIN OVER OUR REGION INTO THE EARLY PART
OF THE NEW WEEK. ANOTHER AREA OF LOW PRESSURE, LOCATED OVER
MISSOURI THIS EVENING, WILL PROGRESS TO THE EAST AND IT SHOULD PASS OFF
THE COASTS OF VIRGINIA AND NORTH CAROLINA EARLY ON MONDAY. A WEAK
FRONTAL BOUNDARY FROM THE NORTHWEST IS EXPECTED TO ARRIVE ON
MONDAY NIGHT. HIGH PRESSURE SHOULD FOLLOW FOR THE MIDDLE AND LATE
PARTS OF THE NEW WEEK. A COLD FRONT FROM THE NORTHWEST IS FORECAST
TO ARRIVE LATE ON SATURDAY.
NEAR TERM /UNTIL 6 AM SUNDAY MORNING/
AT 645 PM, THE CLOUDS ARE INCHING THEIR WAY INTO THE WEST AND
SOUTHWEST PART OF THE FORECAST REGION. SEVERAL LAYERS ARE SHOWING
UP EVEN OUTSIDE OUR WINDOWS BUT THINK THE THICKENING PART WILL
REMAIN TO THE SOUTHWEST. TEMPERATURES WERE FALLING INTO THE 70S
AND UPPER 60S.
THE GRADIENT HAS BEEN THE STORY TODAY WITH COLD AIR MOVING IN AT
80H THROUGH THE AFTERNOON WITH GUSTY WINDS AND NOW WAA IN RESPONSE
TO WAVE MOVING INTO VIRGINIA.
WE LOOK FOR THE EARLIER FORECAST TREND TO CONTINUE, I.E. MOSTLY
CLOUDY OUR SOUTHERN COUNTIES, AND PARTLY CLOUDY UP NORTH.
THE NAM AND THE GFS HAVE BEEN EXHIBITING SOME DIFFICULTY IN HANDLING
THE EASTWARD PROGRESS OF THE CONVECTION THAT WAS IN THE MIDDLE
MISSISSIPPI RIVER VALLEY THIS AFTERNOON. THE LATEST GUIDANCE
SUGGESTED THAT THE CHANCE FOR PRECIPITATION TONIGHT WILL BE VERY LOW
FOR OUR FAR SOUTHERN COUNTIES AND NONEXISTENT FOR THE CENTRAL AND
NORTHERN PARTS OF OUR AREA. AS A RESULT, WE WILL SIMPLY CARRY
SLIGHT CHANCE POPS FOR SOUTHERN DELAWARE AND FOR THE MARYLAND
COUNTIES OF TALBOT AND CAROLINE.
SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/
THE UPPER LEVEL TROUGH IS EXPECTED TO REMAIN OVER THE NORTHEASTERN
STATES FOR SUNDAY, MONDAY AND TUESDAY, WITH A REINFORCING SHORT WAVE
EXPECTED TO DROP DOWN FROM THE NORTHWEST EARLY IN THE NEW WEEK.
THE REMNANTS OF THE CONVECTIVE COMPLEX FROM THE WEST AND ITS
ASSOCIATED SURFACE LOW SHOULD PASS OFF THE COAST AROUND SOUTHERN
VIRGINA AND NORTHERN NORTH CAROLINA EARLY ON MONDAY. OUR SOUTHERN
COUNTIES WILL LIKELY BE ON THE NORTHERN EDGE OF THE SYSTEM'S
PRECIPITATION SHIELD ON SUNDAY NIGHT. WITH CONDITIONS OVER OUR
REGION EXPECTED TO BE STABLE AT THAT TIME, WE HAVE SIMPLY
MENTIONED A CHANCE OF SHOWERS. AGAIN OUR CENTRAL AND NORTHERN
COUNTIES SHOULD REMAIN DRY.
WITH WEAK IMPULSES MOVING ALONG THE UPPER TROUGH, WE MAY SEE SPOTTY
SHOWERS DURING THE AFTERNOON AND EARLY EVENING HOURS ON MONDAY AND
TUESDAY, ESPECIALLY IN EASTERN PENNSYLVANIA AND IN NORTHERN AND
CENTRAL NEW JERSEY. FOR NOW, WILL HAVE INCLUDED SLIGHT CHANCE
POPS. IT SEEMS AS THOUGH INSTABILITY WILL BE LIMITED AT THOSE
TIMES, SO ANY LIGHTNING ACTIVITY MAY BE RATHER ISOLATED.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
IT LOOKS AS THOUGH WE WILL LOSE THE UPPER LEVEL TROUGH BRIEFLY
DURING THE LATE PART OF THE WEEK. HOWEVER, BOTH THE GFS AND THE
ECMWF SUGGEST ITS RETURN DURING THE COURSE OF NEXT WEEKEND, ALTHOUGH
IT MAY NOT BE AS PRONOUNCED AS THE CURRENT ONE.
SURFACE HIGH PRESSURE IS EXPECTED TO BUILD INTO OUR REGION FROM THE
WEST ON WEDNESDAY. THE CENTER OF THE HIGH SHOULD PASS OVER OR NEAR
OUR REGION ON THURSDAY, BEFORE MOVING OUT TO SEA ON FRIDAY. WE WILL
FORECAST DRY WEATHER FOR EACH OF THE THREE DAYS.
A COLD FRONT IS ANTICIPATED TO DROP DOWN FROM THE NORTHWEST ON
SATURDAY, AS AN UPPER LEVEL TROUGH AGAIN BEGINS TO ESTABLISH ITSELF
OVER THE EASTERN STATES. WE WILL INCLUDE A CHANCE FOR AFTERNOON AND
EVENING THUNDERSTORMS.
AVIATION /00Z SUNDAY THROUGH THURSDAY/
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
AS ONE STORM SYSTEM CONTINUES TO SLIDE FARTHER AWAY FROM OUR AREA
TONIGHT, WE TURN OUR ATTENTION TO THE NEXT ONE ARRIVING FROM THE
WEST. THE RATHER FLAT CUMULUS THAT DEVELOPED DURING THE DAYTIME HAVE
JUST ABOUT DISSIPATED AT THIS TIME, AND NOW SOME MID TO HIGH LEVEL
CLOUDS ARE STREAMING ACROSS THE AREA. THIS WILL MOSTLY BE THE THEME
TONIGHT AS A LOW PRESSURE SYSTEM ACROSS THE MISSISSIPPI VALLEY
CONTINUES TO MOVE EAST AND SOUTHEASTWARD THROUGH SUNDAY NIGHT. THE
FORECAST SOUNDINGS INDICATE THAT A MID LEVEL CLOUD DECK WILL BECOME
MORE DOMINANT THROUGH THE OVERNIGHT AND WE TIPPED THE FORECAST IN
THIS DIRECTION. KABE LOOKS TO BE ON THE NORTHERN EDGE OF THE GREATER
CLOUD COVERAGE THEREFORE WE TONED IT DOWN SOME HERE. THE GUSTY WEST
TO NORTHWEST WINDS ARE DIMINISHING AND WITH THE LOSS OF THE DAYTIME
HEATING, VERTICAL MIXING WILL WANE THUS ALLOWING THE WINDS TO GO
MUCH LIGHTER AT ALL THE TERMINALS THROUGH THE EVENING.
FOR SUNDAY, THE AFOREMENTIONED LOW PRESSURE SYSTEM IS FORECAST TO BE
SLIDING TO OUR SOUTH. THERE HAS BEEN SOME UNCERTAINTY ON HOW FAR
NORTH THE PRECIPITATION SHIELD GETS WITH THIS, HOWEVER IT APPEARS
THE BULK OF THE SHOWERS ARE EXPECTED TO REMAIN SOUTH OF OUR
TERMINALS. PERHAPS SOME SHOWERS CANNOT BE RULED OUT MAINLY AT KMIV
AND KACY, HOWEVER THE CHANCE IS SMALL ENOUGH AT THIS TIME TO NOT
INCLUDE. THEREFORE, WE WILL JUST PLAY UP THE CLOUDS WHICH ARE
EXPECTED TO REMAIN VFR THROUGH THE PERIOD. A LIGHT AND VARIABLE WIND
AT MOST TERMINALS SUNDAY WILL GO NORTHWEST BEFORE SHIFTING TO THE
SOUTHWEST. THE FLOW IS FORECAST TO BE WEAKER COMPARED TO TODAY,
THEREFORE WIND GUSTS ARE NOT ANTICIPATED. THIS LIGHTER FLOW SHOULD
ALLOW THE SURFACE WINDS TO BECOME MORE SOUTHERLY /PERHAPS EVEN
SOUTHEAST/ AT TERMINALS SUCH AS KACY, KMIV AND KILG WHERE A SEA
BREEZE AND BAY BREEZE MAY BECOME A FACTOR.
OUTLOOK...
THE AREA OF LOW PRESSURE IS FORECAST TO BE SLIDING TO OUR SOUTH AND
EAST SUNDAY NIGHT INTO MONDAY, TAKING THE CLOUDS/MOISTURE WITH IT.
THE SURFACE WINDS SHOULD TEND TO GO LIGHT AND VARIABLE SUNDAY NIGHT
INTO MONDAY MORNING, BUT SOME TERMINALS MAY HAVE A NORTHEAST WIND
DEVELOP BEFORE SHIFTING TO THE NORTHWEST AS THE LOW MOVES AWAY. WE
THEN GET MORE INTO A NORTHWESTERLY FLOW ALOFT ONCE AGAIN WITH A FEW
WEATHER DISTURBANCES MOVING THROUGH. THESE MAY BE ENOUGH TO ALLOW
FOR AN ISOLATED SHOWER OR THUNDERSTORM MAINLY DURING THE AFTERNOON
AND EVENING ON TUESDAY. AT THE SURFACE, HIGH PRESSURE IS FORECAST TO
BUILD IN WEDNESDAY AND THURSDAY. OVERALL, NO SIGNIFICANT WEATHER
IS ANTICIPATED THROUGH THIS PERIOD.
MARINE
WK HIGH PRESSURE OVER THE REGION HAS BROUGHT GENLY NICE WX TO THE
MARINE AREA FOR THE HOLIDAY WEEKEND. THE ONLY FLY IN THE OINTMENT
IS SOME GUSTS W TO NW WINDS, GENLY TO ABOUT 20 KTS. THERE COULD BE A
GUST OR TWO TO 25 KT, BUT CHCS APPEAR FAIRLY LOW FOR THAT. SEAS ARE
GENLY EXPECTED TO BE IN THE 2 TO 3 FT RANGE.
THE RIP CURRENT RISK WILL CONTINUE TO BE LOW, DESPITE THE LONG
PERIOD ON THE WAVES AND THE NEARING OF THE FULL MOON ON TUESDAY.
A WX DISTURBANCE WILL PASS TO THE S LATER SUNDAY INTO SUNDAY NIGHT.
THIS MAY BRING SOME SCT SHWRS TO THE SRN MARINE ZONES, BUT LITTLE
ELSE.
YET ANOTHER UPPER LOW BUILDS DOWN FROM THE N ON MONDAY WITH WK HIGH
PRES AT THE SFC. GENLY DRY WX IS EXPECTED, WITH THE EXCEPTION OF
SOME ISOLD TO SCT DIURNAL CONVECTION WITH ANY RIPPLES WHICH ROTATE
THROUGH THE LOW.
PHI WATCHES/WARNINGS/ADVISORIES
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.
SYNOPSIS...IOVINO/EBERWINE
NEAR TERM...IOVINO/EBERWINE
SHORT TERM...IOVINO
LONG TERM...IOVINO
AVIATION...GORSE
MARINE...NIERENBERG
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