NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at Sep 11, 3:29 AM EST, 4 hours 41 minutes earlier.
Area forecast discussion, Sep 11, 3:29 AM EST, 4 hours 41 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
429 AM EDT FRI SEP 11 2009
.SYNOPSIS...
STRONG HIGH PRESSURE OVER MAINE AND NOVA SCOTIA EARLY THIS MORNING
WILL MOVE EASTWARD DURING TODAY. THIS WILL ALLOW LOW PRESSURE JUST
OFF THE DELMARVA PENINSULA EARLY THIS MORNING TO DRIFT NORTHWARD
INTO SOUTHERN PORTIONS OF OUR AREA THIS MORNING. THE CENTER OF THE
LOW WILL LIKELY BE NEAR OR JUST EAST OF DELAWARE BAY BY DARK. THE
LOW WILL BEGIN TO MOVE OFFSHORE LATE TONIGHT AND SATURDAY MORNING,
AND THEN RECEDE WELL EAST OF OUR AREA SATURDAY NIGHT. HIGH PRESSURE
OVER THE GREAT LAKES SUNDAY IS FORECAST TO BUILD SOUTHEASTWARD INTO
OUR AREA EARLY NEXT WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
WE ARE REACHING THE CRESCENDO THIS MORNING...OR PERHAPS TODAY...WITH
THIS COASTAL LOW AS IT IS NEARING SOUTHERN PORTIONS OF OUR AREA
EARLY THIS MORNING. THE GFS AND THE NAM ARE PRETTY SIMILAR THIS
MORNING IN STRENGTH, POSITIONING, AND TRACK OF THE LOW AS WELL AS
THE HIGH TO THE NORTH. THE NAM IS JUST A COUPLE OF MILES TO THE WEST
OF THE GFS BY 00Z SATURDAY...AS THE LOW BY THEN IS OVER OR JUST EAST
OF DELAWARE BAY. CONFIDENCE IS LOW THAT THE LOW WILL FILL VERY MUCH
TODAY.
FOR US, THIS MEANS THAT BANDS OF HEAVY RAIN HAVE PINWHEELED INTO
SOUTHERN AND CENTRAL AREAS OVERNIGHT, AND THIS WILL CONTINUE THIS
MORNING. ONGOING HEAVY RAIN TO START WILL ALSO BE ACCOMPANIED BY
STRONG THUNDERSTORMS NEAR THE COAST, AND PERHAPS EVEN SOME OF THOSE
WILL EXHIBIT ROTATION. STRONG SYNOPTIC WIND GUSTS AT AND NEAR THE
COAST SHOULD BE TRENDING DOWNWARD SOMEWHAT DURING THIS MORNING, SO A
WIND ADVISORY WAS NOT RE-ISSUED FOR THIS MORNING AS THE GFS WAS
SHOWING 925 HPA WINDS DIMINISHING TO 35 KNOTS BY MID MORNING. OF
COURSE, THE NAM WAS A BIT STRONGER HPC PREFERRED THE GFS, AS DO WE.
THE INHERITED FLASH FLOOD WATCH WILL BE CONTINUED IN GEOGRAPHICAL
AREA, BUT EXTENDED IN TIME AS RAIN WILL BE PERSISTING BEYOND 15Z,
AND PERHAPS BEYOND 18Z. AT THIS TIME IT WILL JUST BE EXTENDED
THROUGH 20Z AS A NEW FORECAST WILL BE OUT BY THEN. MORE HYDROLOGIC
DETAILS ARE BELOW.
WITH THE ONSHORE FLOW AND SWELLS, TIDES AND RIP CURRENTS ARE ALSO
PROBLEMATIC. MORE ON THESE THREATS CAN BE FOUND BELOW.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...
THE SURFACE LOW RESPONSIBLE FOR THE RAIN AND WIND WILL MEANDER OVER
SOUTHERN PORTIONS OF OUR AREA THIS EVENING, BEFORE STARTING TO PUSH
OFF THE COAST. RAIN CHANCES WILL CONTINUE TO DECREASE FROM SOUTH TO
NORTH TONIGHT INTO SATURDAY MORNING. ISOLATED THUNDER WILL CONTINUE
TO BE ADDED IN FOR THIS EVENING UNTIL INSTABILITY DIMINISHES
OVERNIGHT AND SATURDAY MORNING. HOWEVER, SHOWERS STILL CANT BE
RULED OUT DURING SATURDAY, PERHAPS MORE SO FOR THE MORNING GIVEN THE
PROXIMITY OF THE LOW SURFACE AND ALOFT.
TEMPERATURES WILL REMAIN BELOW NORMAL TODAY AND CLIMB A FEW DEGREES
TO NEAR NORMAL SATURDAY. THE GFS MOS WAS PREFERRED.
&&
.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
THE EXTENDED PORTION OF THE FORECAST IS EXPECTED TO BE MORE
TRANQUIL. A WEAK COLD FRONT IS EXPECTED TO MOVE IN FROM THE NORTH
DURING TUESDAY OR TUESDAY NIGHT, BUT PRECIPITATION MAY BE MEAGER
WITH IT, SO ONLY SLIGHT CHANCES WERE USED FOR NOW. HIGH PRESSURE IS
THEN EXPECTED TO FINISH OFF THE WEEK.
THE WARMEST DAY OF THE COMING WEEK APPEARS TO BE MONDAY, AHEAD OF
THE FRONT, WHERE LOWER TO MID 80S ARE POSSIBLE. TUESDAY MAY BE
ALMOST AS WARM, ALTHOUGH MORE CLOUDS COULD SCREEN THE SUN.
TEMPERATURES ARE EXPECTED TO DROP TO MORE NORMAL LEVELS
POST-FRONTALLY, ESPECIALLY WEDNESDAY AND THURSDAY.
&&
.AVIATION /09Z FRIDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
MVFR TO IFR CONDITIONS, MAINLY BUT NOT EXCLUSIVELY DUE TO CEILINGS,
ARE EXPECTED THROUGH THE TAF PERIOD AS LOW PRESSURE MOVES VERY
SLOWLY TO NEAR THE TAF AREA AND THEN REMAINS NEARLY STATIONARY.
WINDS ARE EXPECTED TO BE FAIRLY STRONG FROM THE NORTHEAST THROUGH
MUCH OF THE PERIOD, AND THUNDER WILL THREATEN THE SOUTHEASTERN TAF
SITES EARLY IN THE TAF PERIOD.
OUTLOOK...
IMPROVEMENT IS EXPECTED FOR THE PERIOD FROM SATURDAY THROUGH TUESDAY
AS HIGH PRESSURE BEGINS TO BUILD DOWN FROM THE NORTHWEST.
&&
.MARINE...
LOW PRESSURE OFF THE SOUTHERN DELMARVA EARLY THIS MORNING WILL VERY
SLOWLY TOWARD AND THEN NEAR THE NEW JERSEY COAST TODAY AND TONIGHT,
THEN BEGIN TO MOVE AWAY ON SATURDAY. THE LOW HAS BEEN DEEPENING MORE
THAN EARLIER MODELS HAD FORECAST, AND THE HIGH TO THE NORTH STILL IS
STRONG. THE MODEL THAT SEEMS TO BE CLOSEST TO CORRECT IS THE ECMWF,
AND WE ARE LEANING THAT WAY WITH THIS FORECAST. WEVE EXTENDED THE
GALES OUT TO 16Z FOR THE NORTHERN ATLANTIC WATERS AND TO 12Z FOR THE
SOUTHERN WATERS AND THE LOWER BAY, AND WEVE EXTENDED THE ADVISORY
FOR THE UPPER BAY OUT UNTIL 16Z. WE MAY END UP EXTENDING THE GALE
OVER THE NORTHERN WATERS AGAIN.
THE LOW IS EXPECTED TO WEAKEN AS IT MOVES AWAY ON SATURDAY. HIGH
PRESSURE IS FORECAST TO BUILD DOWN FROM THE NORTHWEST DURING THE
EARLY PART OF THE NEW WEEK.
&&
.HYDROLOGY...
THE 00Z MODELS CAN NOW BE BLENDED WITH CONTINUITY FROM ONGOING
ACTIVITY. THE HEAVIEST RAIN OVER SOUTHERN AND CENTRAL AREAS BEFORE
SUNRISE SHOULD SHIFT TO CENTRAL AND NORTHERN AREAS LATER THIS
MORNING AND TOWARD MIDDAY AS THE LOW DRIFTS NORTHWARD. EVEN SO,
RAIN IS EXPECTED TO CONTINUE OVER THE FLASH FLOOD WATCH AREA, AND
FOR THIS REASON THE WATCH WAS EXTENDED A FEW HOURS INTO THE
AFTERNOON. SOUTHERN DELAWARE, AND LATELY THE EASTERN MARYLAND SHORE,
RECEIVED A DOUSING LATE THURSDAY, THURSDAY NIGHT, AND INTO EARLY
THIS MORNING. AS MENTIONED, THIS SHOULD TRANSLATE NORTHWARD LATER
THIS MORNING. IT IS STILL THOUGHT THAT A GENERAL 1 TO 3 INCHES OF
RAIN, PERHAPS 2 TO 4 INCHES FAR SOUTH, WILL SUFFICE FOR THIS EVENT.
HPC QPF GUIDANCE HELPED RESOLVE RAIN AMOUNTS THIS MORNING.
&&
.TIDES/COASTAL FLOODING...
WE EXPERIENCED SOME MINOR TIDAL FLOODING ALONG THE SOUTHERN NEW
JERSEY AND DELAWARE COASTS DURING THE LOWER HIGH TIDE OVERNIGHT.
GIVEN THE ECMWF PROG, IT DOES NOT LOOK LIKE TIDAL DEPARTURES CAN
STAY UP FOR THE NEXT HIGH TIDE EARLY THIS AFTERNOON, BUT IT DOES
LOOK LIKE THEY CAN OVER THE CENTRAL AND NORTHERN NEW JERSEY COAST
INCLUDING RARITAN BAY AND THE ADJACENT BACK BAYS. WE HAVE ISSUED
ANOTHER COASTAL FLOOD ADVISORY THERE IN RESPONSE.
&&
.RIP CURRENTS...
WITH THE ROUGH SURF PRODUCED BY THE COASTAL LOW, WE WILL CONTINUE TO
MENTION A HIGH RISK OF RIP CURRENTS TODAY.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...FLASH FLOOD WATCH UNTIL 4 PM EDT THIS AFTERNOON FOR PAZ067>071.
NJ...COASTAL FLOOD ADVISORY FROM 11 AM THIS MORNING TO 3 PM EDT
THIS AFTERNOON FOR NJZ012>014-020-022-025>027.
FLASH FLOOD WATCH UNTIL 4 PM EDT THIS AFTERNOON FOR NJZ015.
DE...FLASH FLOOD WATCH UNTIL 4 PM EDT THIS AFTERNOON FOR DEZ001.
MD...NONE.
MARINE...GALE WARNING UNTIL NOON EDT TODAY FOR ANZ450>452.
GALE WARNING UNTIL 8 AM EDT THIS MORNING FOR ANZ431-453>455.
SMALL CRAFT ADVISORY UNTIL NOON EDT TODAY FOR ANZ430.
&&
SYNOPSIS.../
NEAR TERM.../
SHORT TERM... /KRUZDLO
LONG TERM...KRUZDLO /
AVIATION...DELISI
MARINE...DELISI
HYDROLOGY.../ KRUZDLO
TIDES/COASTAL FLOODING...DELISI
RIP CURRENTS...DELISI