000
FXUS61 KPHI 071941
AFDPHI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
340 PM EDT SUN SEP 7 2008
.SYNOPSIS...
A WEAK HIGH PRESSURE SYSTEM WILL BUILD OVER THE REGION TONIGHT AND
OFF THE COAST MONDAY. A COLD FRONT WILL MOVE IN FROM THE GREAT LAKES
AND CROSS THE REGION TUESDAY NIGHT. ANOTHER HIGH PRESSURE SYSTEM
WILL THEN BUILD IN FROM THE GREAT LAKES WEDNESDAY AND THURSDAY
BEFORE MOVING OFF THE COAST FRIDAY. A PAIR OF COLD FRONTS WILL
APPROACH FROM THE WEST LATE FRIDAY NIGHT AND AGAIN FOR LATE IN THE
DAY ON SUNDAY.
&&
.NEAR TERM /THROUGH TONIGHT/...
THE GFS INITIALIZATION WAS BETTER DOWN TOWARD IKE WHILE THE WRF-NMM
INITIALIZATION LOOKED BETTER TOWARD US. BUT THE WRF-NMM HAD A SLOW
BIAS WITH HANNA AND ITS CFP TIMING IS SLOWER THAN MOST OF THE OTHER
MODELS EXCEPT FOR ITS SREF BRETHREN. THIS FCST PKG IS GOING TO SIDE
WITH THE FASTER GFS AND THUS A SLIGHTLY FASTER CFP ON TUESDAY.
A MUCH QUIETER NIGHT EXPECTED THROUGHOUT OUR CWA. THE CLOUDINESS W
OF OUR CWA IS FORECAST TO LIFT NORTHEASTWARD TONIGHT AND MISS OUR
CWA. NOW THAT IT HAS RAINED, WE DID ADD SOME PATCHY FOG FOR TONIGHT
IN THE INTERIOR VALLEYS AS WINDS OVERALL SHOULD BE LIGHT AND SKIES
MAINLY CLEAR. NOT MUCH OF A SPREAD BETWEEN GFS AND ETA MOS AND WE
WILL FOLLOW AS THEY LOOK GOOD BASED ON CURRENT DEW POINTS.
&&
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
FORECAST SOUNDINGS REMAIN QUITE DRY FOR MONDAY AND THE MOSTLY SUNNY
FORECAST WILL BE CONTINUED. THE FULL SUN MACROS BY BOTH MODELS ARE
SIDING WITH THE WARMER GFS MOS.
EVEN FOLLOWING THE FASTER GFS, THERE IS FORECAST WAA AND LLVL THETA
E ADVT TO ARRIVE BEFORE DAWN ON TUESDAY. A QUESTION AS TO WHETHER OR
NOT THERE WILL BE ENUF MSTR OR TOO MUCH DRY AIR FOR PCPN TO REACH
THE GROUND. ATTM WE INTRODUCED A SLGT CHC NW OF THE I95 CORRIDOR
WHERE THE FCST WAA IS THE STRONGEST.
TUESDAY STILL LOOKING LIKE IT COULD BE A SEVERE WEATHER DAY ACROSS
OUR CWA. WE WOULD HAVE RAISED THAT LEVEL A NOTCH HIGHER IF THE
NEGATIVE TILT TROF WAS FORECAST TO MOVE THRU OUR CWA INSTEAD TO OUR
NORTH. SO IN TYPICAL FASHION THE GREATEST FCST INSTABILITY (SE) IS
NOT COINCIDENTAL WITH THE PROXIMITY TO THE LLJ AND ENTRANCE REGION
TO THE H2.5 JET ALF (N). THE GFS SLIGHTLY FASTER TIMING WOULD FAVOR
THE SERN HALF OF OUR CWA (IN SPITE OF BETTER KINEMATICS N), WHILE
THE WRF-NMM WOULD FAVOR ANY PART OF OUR CWA. THE GFS INSTABILITY
PARAMETERS ARE INFLATED BECAUSE OF FCST DEWPOINTS IN EXCESS OF 70F.
EVEN A TONED DOWN VERSION OF THE WRF-NMM WOULD SUPPORT CONVECTION
WITH THE POSSIBILITY OF SOME SEVERE STORMS AS THE CURRENT SWODY3 HAS.
DAYS ARE GETTING SHORTER, SO THE WINDOW OF OPPORTUNITY NARROWS IF
WAA INDUCED CLOUDS ARE PRESENT. GFS MOS ASSUMES FULL SUN WHILE ETA
MOS ASSUMES LOW CLOUDS ALL DAY. REALITY PRECEDING A CDFNT USUALLY
RESIDES CLOSER TO GFS MOS WHERE THERE SHOULD BE SUFFICIENT BREAKS TO
BRING MAX TEMPS CLOSE TO THOSE LEVELS.
WITH THE FASTER GFS SOLUTION PLUS THE PROGRESSIVELY EARLIER SUNSETS,
WE CONTINUED TO EMPHASIZE THE EVENING HOURS FOR THE HIGHER POPS AS
THE FRONT NEARS AND THEN CROSSES OUR CWA.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
OUR CWA WILL REMAIN WITHIN THE GENERAL ZONAL FLOW ACROSS THE
NORTHERN CONUS THROUGHOUT THIS PERIOD AS WE WAIT TO SEE WHERE IKE
GOES TOWARD THE END OF THIS DETERMINISTIC FORECAST PERIOD. THE FRONT
SHOULD BE SOUTH OF OUR CWA BY WEDNESDAY MORNING AND TWO COOL AND DRY
DAYS ARE EXPECTED ON WED AND THU. THE CAVEAT WILL BE THE ORIENTATION
OF THE HIGH WHICH MIGHT BRING IN SOME SC FROM THE OCEAN WITH OUR SRN
CWA HAVING THE GREAT CHANCE. THE NEXT LOW PRESSURE SYSTEM IS
FORECAST TO REACH THE GREAT LAKES ON FRIDAY. THE CHANCES AND TREND
OF SOME WAA INDUCED PRECIPITATION TO OCCUR THURSDAY NIGHT APPEAR
DIMINISHED. THE NEXT COLD FRONT SHOULD MOVE THROUGH OUR CWA FRIDAY
NIGHT OR EARLY SATURDAY. THE AIR MASS BEHIND THIS FRONT IS NOT
ANTICIPATED TO BE AS REFRESHING AS THE MIDWEEK ONE. STAB FCSTS
SUPPORT THE CONTINUED MENTION OF THUNDER. ANOTHER COLD FRONT IS THEN
FORECAST TO APPROACH THE REGION ON SUNDAY. THIS ONE MIGHT EVENTUALLY
ENTRAIN IKE ITSELF OR AT THE LEAST SOME OF THE TROPICAL CONNECTION
MOISTURE ASSOCIATED WITH IKE. PLEASE REFER TO PRODUCTS BY THE TPC
FOR OFFICIAL FORECAST INFORMATION.
&&
.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
AS HANNA CONTINUES TO MOVE AWAY FROM THE AREA, HIGH PRESSURE WITH
MUCH DRIER AIR HAS MOVED IN. NOTHING MORE THAN A FEW FAIR WEATHER CU
TODAY AND THESE WILL DISAPPEAR BY SUNSET. THE HIGH PRESSURE WILL
CONTROL OUR WEATHER INTO TUESDAY. EXPECT CLEAR SKIES TONIGHT. MAY BE
SOME LIGHT FOG WITH MVFR VSBYS IN THE PRE-DAWN HOURS IN THE MOST
SUSCEPTABLE AREAS WHERE WINDS DROP OFF AND GROUND MOISTURE REMAINS
FROM YESTERDAYS RAINS, BUT, FOR THE MOST PART, VFR CONDITIONS WILL
PREVAIL. ONLY SOME FAIR WEATHER CLOUDS EXPECTED MONDAY. A FRONTAL
SYSTEM WILL MOVE IN WITH ANOTHER POSSIBILITY OF SHOWERS AND
THUNDERSTORMS TUESDAY INTO TUESDAY NIGHT. HIGH PRESSURE WITH VFR
WEATHER IS EXPECTED AGAIN WEDNESDAY AND THURSDAY.
&&
.MARINE...
SMALL CRAFT ADVISORIES WERE EXTENDED INTO THE AFTERNOON FOR SEAS.
EVEN THOUGH WAVE HEIGHTS WELL OFF SHORE ARE STILL RUNNING 5 TO
ALMOST 6 FT, THEY HAVE TRANSITIONED INTO 13 TO 14 SECOND LONG
PERIOD SWELLS. WITH A DIMINISHING TREND FORECAST, SEE NO REASON
TO CONTINUE THE ADVISORY. HIGH PRESSURE WILL KEEP WINDS AND WAVES
BELOW SMALL CRAFT ADVISORY CRITERIA INTO TUESDAY OR TUESDAY NIGHT.
A COLD FRONTAL PASSAGE IS FORECAST FOR TUESDAY NIGHT. HIGH PRESSURE
PUSHING IN BEHIND THE FRONT IS EXPECTED TO BRING N TO NE WINDS ON
WEDNESDAY AND THAT MAY PUSH WINDS AND/OR SEAS TO NEAR SMALL CRAFT
ADVISORY CRITERIA.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR
ANZ450>455.
&&
$$
SYNOPSIS...GIGI
NEAR TERM...GIGI
SHORT TERM...GIGI
LONG TERM...GIGI
AVIATION...RPW
MARINE...RPW
RIP CURRENTS...RPW
