NWS Philadelphia/Mount Holly wrote its last area forecast discussion before the first event at May 23, 6:30 PM EST, 1 hour 25 minutes earlier.
Area forecast discussion, May 23, 6:30 PM EST, 1 hour 25 minutes before
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
730 PM EDT MON MAY 23 2011
.SYNOPSIS...
A WARM FRONT WILL MOVE NORTH OF THE AREA TONIGHT. A COLD FRONT WILL
APPROACH THE REGION TUESDAY, THEN CROSS THE AREA TUESDAY NIGHT
BEFORE STALLING TO THE SOUTH SOUTH ON WEDNESDAY. WEAK HIGH
PRESSURE WILL MOVE ACROSS THE AREA ON WEDNESDAY. ANOTHER FRONTAL
BOUNDARY WILL DROP INTO THE GREAT LAKES REGION ON THURSDAY, AND
WEAK AREAS OF LOW PRESSURE WILL RIDE ALONG IT FOR THE END OF THE
WEEK.
&&
.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
THE WARM FRONT WAS NEAR A RDG TO PHL TO ACY LINE EARLY THIS
AFTERNOON, AND IT IS EXPECTED TO CONTINUE TO MAKE PROGRESS
NORTHWARD AS THE HIGH TO THE EAST DRIFTS AWAY. STILL NOT A ROBUST
UPPER JET NEARBY TO SUPPORT ANY CONVECTION THIS EVENING, BUT THERE
IS A MID LEVEL IMPULSE THAT THE MODELS STILL PROG ACROSS OUR AREA
BY AROUND 06Z, DECENT INSTABILITY IN THE WARM SECTOR (ALTHOUGH NOT
VERY IMPRESSIVE AT MID LEVELS) AND SOME SHEAR. WE HAVE BEEN
CARRYING MILDLY ENHANCED WORDING, AND WE WILL RETAIN THAT WHERE WE
THINK THE INGREDIENTS ARE BEST THIS EVENING. ANOTHER IMPULSE IS
PROGGED TO APPROACH LATE TONIGHT, WHICH IS WHY WE ONLY THROTTLE
BACK TO SLIGHT CHANCE POPS RATHER THAN DROP THEM ENTIRELY. WE ARE
GOING TO RESIDE ON THE HIGH SIDE OF STAT GUIDANCE MIN TEMPERATURES
IN THE WAKE OF THE WARM FRONT ON A DECENT SOUTHERLY FLOW JUST
ABOVE THE SURFACE.
&&
.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
A COLD FRONT WILL APPROACH TOMORROW, AND THIS TIME THE UPPER JET
LOOKS A BIT CLOSER IF NOT MORE ROBUST. THERE IS AN ASSOCIATED MID
LEVEL IMPULSE, INSTABILITY IS AGAIN EXPECTED (THIS TIME OVER THE
GREAT BULK OF THE AREA), MOISTURE IS AVAILABLE, BUT SHEAR PERHAPS
WILL BE A BIT MORE MARGINAL. THE BEST FORCING LOOKS TO BE
NORTHWEST. INSTABILITY AND MOISTURE ARE AVAILABLE EVERYWHERE. WE
AGAIN WILL CARRY MILDLY ENHANCED WORDING AWAY FROM THE ATLANTIC
AND WE WILL CARRY OUR BEST POPS TOWARD THE BEST FORCING. WE
CONTINUE THE PREVIOUS FORECAST PHILOSOPHY OF LEANING STRONGLY
TOWARD THE WARMER STAT GUIDANCE AHEAD OF THE APPROACHING FRONT
GIVEN THE MODEL SOUNDINGS AND THE NAM/ECMWF H925 TEMPERATURES.
AFTER THE USUAL LINGERING EVENING POPS, WE TRY TO CARVE OUT A
PERIOD FROM LATE TUESDAY NIGHT THROUGH WEDNESDAY EVENING WITHOUT
ANY POPS. THE MID LEVEL RIDGE IS PROGGED TO BUILD WITH A MINOR
AXIS PERHAPS DEVELOPING TO OUR WEST, AND THE MODELS DON'T SEEM TO
BE PUSHING ANY IMPULSES OUR WAY. WITH THE EXCEPTION OF RADIATING
SPOTS, WE GO FOR THE WARMER MINS ON TUESDAY NIGHT, AND WE GO FOR
THE WARMER TEMPERATURES AWAY FROM THE COAST ON THE WEDNESDAY
MAXES. THE WIND FIELD AT LOW LEVELS LOOKS RATHER WEAK ON
WEDNESDAY, AND SO WE CARRY A SEA BREEZE WITH COOLER TEMPERATURES
ALONG THE COAST.
ANOTHER SURFACE BOUNDARY STARTS TO APPROACH FROM THE NORTHWEST
WEDNESDAY NIGHT AND REMAINS FAIRLY CLOSE TO THE AREA THROUGH
THURSDAY. RIGHT NOW, THE MODELS ARE WARMING US NICELY TO THE SOUTH
OF THAT FRONT WITH VARYING AMOUNTS OF INSTABILITY, A MEDIOCRE
WIND FIELD AND DECENT MOISTURE. WE MAY GET AN IMPULSE KICKING OUT
OF A SLOWLY APPROACHING MID LEVEL TROUGH, AND WE CARRY POPS THAT
RANGE FROM CHANCE NORTHWEST (FURTHEST AWAY FROM THE MID LEVEL
RIDGE) TO NIL SOUTHEAST. WE BOUGHT INTO THE WARM H925 TEMPERATURES
AND WENT VERY WARM ON MAX TEMPERATURES.
&&
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
THE FIRST LOOK FOR THE ENTIRE MEMORIAL DAY WEEKEND IS SUGGESTING A
SUMMER TYPE PATTERN WITH UNSEASONABLY WARM TEMPS AND THE CHANCES FOR
MAINLY AFTERNOON AND EVENING THUNDERSTORMS WITH THE GREATEST
EMPHASIS IN THE NORTHWESTERN HALF OF OUR CWA.
THE MODELS TRY TO BRING COLD FRONTS THROUGH OUR CWA WITHOUT MUCH
SUCCESS UNTIL MAYBE SUNDAY AT THE EARLIEST. THE FIRST ATTEMPT COMES
THURSDAY NIGHT. THE STALLED FRONT SHOULD LIFT NORTHWARD ON FRIDAY
WITH THERMAL FIELDS SUPPORTING AROUND 90F ALONG THE COASTAL PLAIN
AWAY FROM THE IMMEDIATE COAST. BOTH THE GFS AND ECMWF HAVE THE
THERMAL CORE OF THE SERN CONUS RIDGE PASSING ACROSS OUR CWA THEN.
IF THERE IS A FORECAST PERIOD THAT LOOKS PCPN FREE THE MOST ATTM ITS
FRIDAY NIGHT AS THE WARM FRONT SHOULD MOVE NORTH OF THE AREA. WITH
THE COLD FRONT EDGING ITS WAY EASTWARD FROM THE OH VALLEY,
SATURDAY'S BEST TSRA CHANCES SHOULD BE IN THE NW HALF OF OUR CWA.
THE THERMAL CORE MOVES OFFSHORE, BUT THINK GUIDANCE COOLS THE AIR
MASS OFTEN TOO MUCH GIVEN THERE SHOULD NOT BE AN AIR MASS CHANGE.
WE WENT ABOVE STAT GUIDANCE ON SATURDAY AND SIMILARLY FOR SUNDAY.
LESS CONFIDENCE SUNDAY BECAUSE OF CFP TIMING DIFFERENCES.
AMONG THE LATEST GUIDANCE, THE ECMWF AND GFS HAVE BECOME MORE
PROGRESSIVE, WITH THE UKMET AND CAN GGEM A BIT SLOWER WITH THE CFP.
WITHOUT MUCH CONTINUITY FROM THE PREVIOUS MODEL RUN, WE STAYED A
MORE CONSERVATIVE COURSE OF MOVING THE CDFNT THROUGH GIVEN IT
USUALLY COMES LATER THAN SOONER THIS TIME OF YEAR. AS A HEDGE THOUGH
WE DID CARRY THE HIGHEST POPS FOR THE HOLIDAY WEEKEND ON SUNDAY WITH
LOWER POPS ON MONDAY.
&&
.AVIATION /23Z MONDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.
A LINE OF TSRAS TRIED TO FORM WEST OF THE TERMINAL SITES, BUT
OTHER THAN KABE AT TAF START TIME, IT LOOKS AS THOUGH TSRAS SHOULD
NOT AFFECT OUR OTHER TERMINALS. WHAT IS LEFT OF THE ONGOING
CONVECTION SHOULD BE DONE BY 02Z. THE FORECAST UNCERTAINTY THEN IS
HOW MUCH FOG OR LOW CLOUDS WILL FORM OVERNIGHT. THE PASSAGE OF THE
WARM FRONT THROUGH ALL THE TERMINALS SHOULD BRING IN SOME DRIER
AIR JUST ABOVE THE SURFACE OVERNIGHT, IN ADDITION MID LEVEL DEBRIS
FROM THE CONVECTION FARTHER TO THE WEST SHOULD SPREAD OVER THE
TERMINALS LATER TONIGHT. SO WE BROUGHT VSBYS DOWN TO IFR WHERE THE
TSRAS WITH HEAVIER RAIN HAVE OCCURRED AND ALSO NEAR THE NJ COAST
BECAUSE OF PROXIMITY TO THE OCEAN. THE ONLY TERMINAL WE FORECAST
AN IFR CIG IS AT KACY.
A COLD FRONT WILL BE APPROACHING THE TERMINALS ON TUESDAY.
PRECEDING ITS ARRIVAL CONDITIONS SHOULD BECOME VFR DURING THE
MORNING ONCE THE FOG BURNS AWAY. WHILE SCATTERED SHOWERS AND
THUNDERSTORMS SHOULD OCCUR PRECEDING THE FRONT, THERE ARE MIXED
SIGNALS AMONG OUR MODELS AS TO THE AREAL COVERAGE. BECAUSE OF
THIS CONFIDENCE AT THIS FORECAST JUNCTURE IS TOO LOW TO INCLUDE
TSRAS IN THE TAFS, SO WE KEPT THE MENTION OF CB CLOUDS FOR NOW.
OUTLOOK...
TUESDAY NIGHT...THE COLD FRONT SETTLES INTO THE AREA AND STALLS
NEARBY. THERE COULD BE A WEAK LOW PRESSURE SYSTEM ALONG IT WHICH MAY
HELP TO PRODUCE SOME SHOWERS AND THUNDERSTORMS. THEREFORE, POCKETS
OF SUB-VFR CONDITIONS ARE POSSIBLE.
WEDNESDAY...THE FRONT STALLS MAINLY TO OUR SOUTH AS WEAK HIGH
PRESSURE SLIDES TO OUR NORTH. THIS MAY BE ENOUGH TO HINDER ANY
SHOWER AND THUNDERSTORM DEVELOPMENT. GENERALLY VFR.
THURSDAY THROUGH SATURDAY...A STALLED FRONT SHOULD TURN NORTHWARD AS
A WARM FRONT BUT PROBABLY BE SLOW TO CLEAR THE AREA AS LOW PRESSURE
SYSTEMS TRACK TO OUR WEST. THEREFORE, WE MAY HAVE SUB-VFR CONDITIONS
DUE TO THE WARM FRONT AND ALSO DUE TO THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS AROUND.
&&
.MARINE...
A WARM FRONT WILL CONTINUE TO GRADUALLY LIFT NORTHEASTWARD AND
ACROSS THE AREA THROUGH TONIGHT. THIS WILL MAINTAIN A SOUTHERLY FLOW
ACROSS THE WATERS. THERE HAS BEEN SOME GUSTS NEARING 25 KNOTS THIS
AFTERNOON BUT THIS HAS BEEN MAINLY NEARSHORE DUE TO WARMER SURFACE
TEMPERATURES AND BETTER MIXING. THE SOUTHERLY FLOW HAS RESULTED IN
THE SEAS BUILDING FROM SOUTH TO NORTH AND WITH THIS EXPECTED TO BE
MAINTAINED THROUGH ABOUT TUESDAY MORNING, WE WILL EXTEND THE SMALL
CRAFT ADVISORY THROUGH 16Z TUESDAY. SOME MODEL GUIDANCE ARE STRONGER
WITH THE LOW-LEVEL JET TONIGHT AND THEREFORE BRING 25 KNOT WINDS TO
THE AREA. HOWEVER, GIVEN THE FAIRLY PRONOUNCED LOW-LEVEL INVERSION
FORECAST OVER THE WATERS DUE TO INCREASINGLY WARMER AIR OVER THE
COOLER WATER, MIXING SHOULD BE LIMITED. AN EXCEPTION TO THIS COULD
BE MAINLY NEARSHORE FOR A TIME. THEREFORE, THE ADVISORY IS MAINLY
FOR ELEVATED SEAS. FOR DELAWARE BAY, IT APPEARS GUSTS TO 25 KNOTS
SHOULD BE LIMITED THEREFORE WE WILL MAINTAIN NO ADVISORY ATTM. SOME
SHOWERS AND THUNDERSTORMS MAY CROSS THE AREA TONIGHT, WITH
POTENTIALLY LOCALLY GUSTY WINDS. AS THE DEW POINTS INCREASE TONIGHT,
PERHAPS SOME FOG OVER THE WATERS BUT GIVEN INCREASED UNCERTAINTY
WITH THIS, IT WAS NOT INCLUDED ATTM.
FOR TUESDAY, A COLD FRONT WILL APPROACH LATER IN THE DAY. A
SOUTHERLY FLOW WILL CONTINUE BUT IT MAY WEAKEN ENOUGH IN THE
AFTERNOON AND EVENING TO ALLOW THE SEAS TO LESSEN A LITTLE BIT. THIS
FRONT SHOULD TRIGGER SHOWERS AND THUNDERSTORMS MAINLY DURING THE
AFTERNOON AND EVENING AND SOME STORMS COULD BE STRONG. THE FRONT
SHOULD TEND TO STALL IN THE AREA OR JUST TO OUR SOUTH WEDNESDAY, AND
ITS ACTUAL LOCATION WILL IMPACT THE WINDS. THE FRONT IS THEN
FORECAST TO SLOWLY MOVE NORTHWARD AS A WARM FRONT THURSDAY THROUGH
SATURDAY AS LOW PRESSURE SYSTEMS TRACK TO OUR WEST. THE FLOW LOOKS
WEAK ENOUGH TO MAINTAIN CONDITIONS GENERALLY BELOW ADVISORY
CRITERIA.
&&
.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TUESDAY FOR ANZ450>455.
&&
SYNOPSIS...DELISI/HAYES
NEAR TERM...DELISI
SHORT TERM...DELISI
LONG TERM...GIGI
AVIATION...GIGI/GORSE
MARINE...GORSE