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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 131957
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
357 PM EDT MON MAY 13 2013

.SYNOPSIS...
-- Changed Discussion --
HIGH PRESSURE WILL MOVE TO THE EAST COAST TUESDAY. A STRONG WARM
FRONT FROM MICHIGAN TO VIRGINIA TUESDAY WILL THEN CROSS THE MID
ATLANTIC STATES WEDNESDAY NIGHT FOLLOWED BY A WEAK COLD FRONTAL
PASSAGE THURSDAY NIGHT. WEAK HIGH PRESSURE COVERS OUR AREA LATER
FRIDAY INTO SATURDAY.  LOW PRESSURE TAKING SHAPE OVER THE UPPER
MIDWEST NEXT SUNDAY MOVES VERY SLOWLY EAST WITH AN INCREASINGLY
HUMID SOUTHERLY FLOW DEVELOPING HERE EARLY NEXT WEEK.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
-- Changed Discussion --
A RATHER SHARP SHORT WAVE/VORT MAX IS APPROACHING THE AREA FROM THE
NORTHWEST EMBEDDED A LONGER WAVE TROUGH ACROSS THE NORTHEAST. THERE
IS SOME MOISTURE IN THE 850-700 MB LEVELS ALONG WITH SOME
INSTABILITY WITH 925-700 LAPSE RATES NEAR 9 DEGREES C/KM. THIS IS
PRODUCING SOME SCATTERED SHOWERS AND SPRINKLES JUST TO OUR
NORTHWEST. WE WILL INTRODUCE ISOLATED SHOWERS/SCATTERED SPRINKLES
FOR THE REMAINDER OF THE AFTERNOON INTO THE EARLY EVENING. AFTER THE
SUN GOES DOWN, THESE SHOWERS/SPRINKLES SHOULD DIMINISH IN COVERAGE.

CLOUDS WILL BEGIN TO DIMINISH AFTER SUNSET ACROSS THE AREA AS WELL,
LEADING TO MOSTLY CLEAR SKIES OVERNIGHT. HIGH PRESSURE TO OUR
SOUTHWEST WILL BEGIN NOSING ITS WAY ACROSS THE AREA OVERNIGHT AS
WELL. THIS WILL ALLOW FOR WINDS TO BECOME FAIRLY LIGHT ACROSS MUCH
OF THE AREA. THE COLD AIRMASS WILL BE IN PLACE FOR ONE MORE NIGHT AS
THE MID/UPPER TROUGH BEGINS TO SLIDE ACROSS THE AREA OVERNIGHT.
TEMPERATURES TONIGHT ARE FORECAST TO BE A FEW DEGREES COOLER THAN
LAST NIGHT. THE FREEZE WARNING FOR THE NORTHERN THREE COUNTIES
REMAINS IN PLACE, AND A FROST ADVISORY IS NOW IN EFFECT FOR MUCH OF
THE REST OF OUR PENNSYLVANIA COUNTIES, EXCEPT FOR EXTREME SOUTHEAST
PORTIONS OF PENNSYLVANIA; PORTIONS OF NORTHERN NEW JERSEY, AS WELL
AS PORTIONS OF THE PINE BARRENS.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
-- Changed Discussion --
AFTER A CHILLY START TO THE DAY, TUESDAY WILL END UP BEING A VERY
NICE DAY. HIGH PRESSURE SLIDES TO OUR SOUTH WHILE THE MID/UPPER
TROUGH SLIDES TO OUR EAST. THICKNESSES INCREASE SLIGHTLY ACROSS THE
AREA, WHICH WILL ALLOW TEMPERATURES TO WARM A FEW DEGREES FROM THE
HIGHS ON MONDAY. WINDS ARE NOT EXPECTED TO BE AS BREEZY AS THEY WERE
ON MONDAY, AND IT SHOULD BE LESS CLOUDY...AT LEAST IN REGARDS TO
LOW-LEVEL CLOUDS. THERE COULD BE SOME HIGH-LEVEL CIRRUS DURING THE
DAY, ALONG WITH SOME SCATTERED CUMULUS DURING THE AFTERNOON.
-- End Changed Discussion --

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
-- Changed Discussion --
**NEAR RECORD COLD AND FROST FREEZE POTENTIAL EARLY TUESDAY
 MORNING**

500MB: STRONG RIDGING IS IN PROGRESS TO START THIS EXTENDED PERIOD
WITH A FEW WEAK SHORT WAVES LATE IN THE WEEK CARVING OUT A TROUGH
OVER THE MARITIMES BY SATURDAY THEN FURTHER RIDGING DEVELOPS ALONG
THE US EAST COAST SUNDAY IN ADVANCE OF A SLOWLY DEVELOPING LARGE
SCALE TROUGH IN NATIONS MIDSECTION EARLY NEXT WEEK.

PRESUMING THIS PATTERN DEVELOPS AS INTERPRETED ABOVE...ITS BASICALLY
DRY THROUGH AT LEAST SATURDAY WITH LESS THAN ONE HALF INCH OF RAIN
BUT NEXT WEEK SHOULD BE COMPARATIVELY WET AS A LONG DURATION DEEP
AND INCREASINGLY MOIST SOUTH TO SOUTHWEST FLOW DEVELOPS ALONG THE
EASTERN SEABOARD.

CALENDAR DAY AVERAGE TEMPERATURES: WEDNESDAY AROUND HALF THE BELOW
NORMAL DEPARTURE OF TOMORROW-TUESDAY...OR ABOUT 5 OR 6 DEGREES BELOW
NORMAL THEN 5 DEGREES ABOVE NORMAL THU AND POSSIBLY FRI. IT MAY
COOL A BIT TO NEAR NORMAL SATURDAY (DRIER AIRMASS) BEFORE PROBABLY
WARMING ABOVE NORMAL SUNDAY AND ESPECIALLY NEXT MONDAY.

THE DAILIES BELOW /INTERPRETATION OF MULTI MODEL PROBABLE
ESSENCE-NOT EVERY POSSIBLE SOLUTION IS LISTED BELOW/...

THE FORECAST FOR WEDNESDAY AND THURSDAY IS 50 50 BLEND OF THE 12Z/13
NAM/GFS MAV/METMOS WITH TEMP CHECKS AGAINST THE RGEM/NAM/ECMWF 2M
TEMPS AND POPS ADDING A 30 PERCENT BLEND FROM THE 09Z/13 SREF.

THE PERIOD THURSDAY-SUNDAY IS ALMOST EXCLUSIVELY THE 15Z/13 HPC
GRIDDED ELEMENTS WITH A 50 50 BLEND OF THE 12Z/13 GFS MEXMOS FOR
TEMPS.  HPC POPS MAY BE MODIFIED IF THE 12Z/13 MASS FIELDS OF THE
ECMWF CYCLICALLY SUGGEST AN ADJUSTMENT WITH SUPPORT FROM THE 12Z/13
GEFS 6 HR POPS FOR .05.

TODAYS NCEP FCST CYCLE DECIDEDLY SPEEDS UP THE PROCESSES BY 12
HOURS FROM PRIOR FORECAST INTERPRETATIONS FOR A WED NIGHT CONVECTIVE
EVENT NOW MORE LIKELY OCCURRING WEDNESDAY.

TUESDAY NIGHT...MOSTLY CLEAR TO START BUT CLOUDING UP RAPIDLY NEAR
MIDNIGHT WITH A CHANCE OF SCT LIGHT MID LVL GENERATED SHOWERS AT
DAWN WEDNESDAY. WEAK INSTABILITY BURST SOUTH-SOUTHWESTERLY WAA ON
THE BACKSIDE OF THE SE USA COASTAL HIGH.

WEDNESDAY...VARIABLE CLOUDINESS WITH SCT SHOWERS AND AT LEAST
ISOLATED MID-LATE AFTN SEWD MOVING TSTMS. NOTING THE RECENT NCEP
MODEL CYCLES CATCHING UP WITH THE GGEM OF PRIOR CYCLES AND NOW THE
ECMWF IS THE WEAK AND STILL SLOW OUTLIER. SSE WIND G15-20 MPH IN
THE AFTN. SWI -2C TO -4C IN THE AFTN/EVE WITH TT 52-54 AND KI NEAR
35C. LATE DAY ML CAPE NEAR 600J DELMARVA IN WAA WITH MOSGUIDANCE
SUGGESTING NEAR 90F AT KCRW...HINTS POTENTIAL FOR HAIL WITH ANY
STRONGER THUNDER LATE WED AFTN.(ALSO VERY WEAK LEFTOVER INSTABILITY
OF MIDWEST EML REFERENCED IN 1725Z SWODY2). THIS FITS NICELY WITH
THE SPCDY3 SEE TEXT-5% FROM EARLY THIS MORNING. POPS ARE MODEST
DUE TO MODEL DISPARITY AND MY THINKING IS THAT STRONGER CONVECTION
SHOULD BE NEAR KPHI SOUTH. CONFIDENCE FOR THE MAX TEMPS ON
WEDNESDAY IS MUCH BELOW AVERAGE DUE TO TIMING OF THE CLUSTERS OF
SHOWERS WITH MAX HEATING. IF NO RAIN BETWEEN 11AM AND 2PM...THE
CURRENT FCST LOOKS GOOD. IF RAIN MIDDAY-EARLY AFTN...THEN THERE
WILL BE LARGER FCST ERRORS.

WED NIGHT...ANY CLUSTERS OF SHOWERS/ISO TSTMS SHOULD END EARLY AS
THEY HEAD ESE OUT TO SEA. POSSIBLE HAZE OR A BIT OF FOG LATE.

THU...P TO M/S AND WARM. W WIND G15 MPH IN THE AFTN. 80S PHL.
INSTABILITY OVER DELMARVA AND MODELED APPROACHING WEAK COOL FRONT
FROM THE NORTH MIGHT TRIGGER TSTMS LATE DAY OVER THE DELMARVA.

FRI...SUNNY...DRIER AIRMASS BUT I THINK STILL WARM! NW WIND GUST
10-15 MPH IN THE AFTN...BUT EVENTUALLY COASTAL SEABREEZES EXPECTED
BY LATE AFTN. 80S PHL. THE ECMWF HAS BEEN ALL OVER THE PLACE THE
LAST SEVERAL CYCLES ON THE TROUGH EVOLUTION OR RELATIVE LACK
THEREOF OVER NEW ENGLAND AND THE MARITIMES. MY FEELING...BASED ON
THE ECMWF LACK OF CONSISTENCY AND HPC 15Z GUIDANCE IS THAT THE
ECMWF IS NOW TRYING TO SHOVE TOO MUCH COOL AIR SOUTHWARD.

SAT...M/S DAY BUT INCREASING CLOUDS AT NIGHT MAYBE SHOWERS BY
SUNDAY MORNING IN WEAK WAA? LIGHT WIND WITH COOLING COASTAL
SEABREEZES.

SUN AND MON...15Z HPC GUIDANCE PREVAILS.
-- End Changed Discussion --

&&

.AVIATION /20Z MONDAY THROUGH SATURDAY/...
-- Changed Discussion --
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

VFR CONDITIONS ARE EXPECTED ACROSS THE TAF SITES TONIGHT. SCT-BKN
CLOUDS THIS EVENING SHOULD BECOME MOSTLY CLEAR OVERNIGHT. A FEW
SCATTERED SPRINKLES OR SHOWERS MAY AFFECT THE NORTHERN PORTIONS OF
THE FORECAST AREA LATE THIS AFTERNOON INTO EARLY EVENING, BUT SHOULD
NOT IMPACT ANY TAF SITES. ANY WIND GUSTS LATE THIS AFTERNOON/EARLY
EVENING SHOULD DIMINISH AROUND SUNSET.

VFR CONDITIONS WILL CONTINUE INTO TUESDAY. WINDS ARE NOT EXPECTED TO
BE AS GUSTY AS TODAY, BUT MAY PERIODICALLY GUST AROUND 15-20 KNOTS.

OUTLOOK...
THIS MONDAY FCST CYCLE DECIDEDLY SPEEDS UP THE PROCESSES FROM WED NIGHT
INTO WED.

TUE NIGHT...VFR WITH CIGS AOA 5000 FT DEVELOPING NEAR 04Z. A BAND
OF SHOWERS POSSIBLE TOWARD 10Z WED. LIGHT SOUTH WIND. MODERATE
CONFIDENCE.

WED...VFR. CIGS AOA 5000 FT. SCT SHOWERS WITH MVFR CONDS IN SCT AFTN
TSTMS WITH A POSSIBLE ISOLATED HAIL EVENT. SSE WIND G15-20 KT IN THE
AFTN. LOW TO MODERATE CONFIDENCE.

WED NIGHT...VFR WITH POSSIBLY BRIEF MVFR CONDS IN ANY LEFTOVER EVENING
SHOWERS AND THEN MVFR CONDS IN POSSIBLE HAZE TOWARD 12Z THU. S WIND.
LOW TO MODERATE CONFIDENCE.

THU AND FRI...PROBABLY VFR. W TO NW WIND G10-15 KT IN THE AFTN.
MODERATE TO HIGH CONFIDENCE.

SAT...VFR. MODERATE CONFIDENCE.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
A SMALL CRAFT ADVISORY WILL REMAIN FOR A FEW HOURS THROUGH LATE THIS
AFTERNOON INTO THIS EVENING. WINDS ALOFT ARE EXPECTED TO DIMINISH
TOWARD SUNSET, AND THE GUSTS TO 25 KNOTS SHOULD BEGIN TO DROP OFF
OVER THE NEXT FEW HOURS. ONCE WINDS DROP OFF BELOW 25 KNOTS, THEY
WILL REMAIN BELOW ADVISORY LEVELS THROUGH THE DAY TUESDAY AS HIGH
PRESSURE FROM THE SOUTH NOSES ITS WAY INTO OUR AREA. WINDS MAY STILL
PERIODICALLY GUST AROUND 20 KNOTS, ESPECIALLY TONIGHT. SEAS ARE
EXPECTED TO REMAIN BELOW 5 FEET THROUGH TUESDAY.

OUTLOOK...
TUE NIGHT...NO HEADLINE ANTICIPATED.

WED INTO THU...A WARM FRONT WILL APPROACH AND SLY FLOW WILL INCREASE
AND A WAA SCA SITUATION IS POSSIBLE FOR A PERIOD OF 25 KT GUSTS
WEDNESDAY OR WEDNESDAY EVENING. SEAS WILL EVENTUALLY BUILD TO 5 OR FEET
ON THE ATLANTIC WATERS WED OR WED NIGHT THEN SLOWLY SUBSIDE THU.

FRI AND SAT...NO HEADLINES ANTICIPATED IN LIGHT FLOW WITH AFTERNOON
SEABREEZES PROBABLE.
-- End Changed Discussion --


&&

.CLIMATE...
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POSSIBLE RECORD OR NEAR RECORD LOWS TUESDAY MORNING.

5/14 TUESDAY...A GOOD CHANCE FOR SEVERAL OF THESE BEING WITHIN 2
DEGREES OF RECORD.

MPO 29 1938 POR DATES BACK TO 1901
PHL 40 1996 POR DATES BACK TO 1872
RDG 33 1996 POR DATES BACK TO 1869
ILG 36 1996 1940 1939 POR DATES BACK TO AT LEAST 1917
GED 35-1996 POR DATES BACK TO ONLY TO 1948
-- End Changed Discussion --

&&

.EQUIPMENT...
-- Changed Discussion --
MILLVILLE ASOS GROUND TO AIR RADIO FREQUENCY IS OUT OF SERVICE FOR
THE NEXT COUPLE OF DAYS. A NOTAM HAS BEEN ISSUED.
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
PA...FROST ADVISORY FROM 2 AM TO 8 AM EDT TUESDAY FOR PAZ060>062-
     101-103-105.
     FREEZE WARNING FROM 2 AM TO 8 AM EDT TUESDAY FOR PAZ054-055.
NJ...FROST ADVISORY FROM 2 AM TO 8 AM EDT TUESDAY FOR NJZ007>010-
     020>022-027.
     FREEZE WARNING FROM 2 AM TO 8 AM EDT TUESDAY FOR NJZ001.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ430-
     431-450>455.
-- End Changed Discussion --

&&

$$
SYNOPSIS...DRAG 357
NEAR TERM...ROBERTSON 357
SHORT TERM...ROBERTSON 357
LONG TERM...DRAG 357
AVIATION...DRAG/ROBERTSON 357
MARINE...DRAG/ROBERTSON 357
CLIMATE...357
EQUIPMENT...357