-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KPHI 201206
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
806 AM EDT MON MAY 20 2013

.SYNOPSIS...
A FRONTAL BOUNDARY EXTENDED FROM THE GREAT LAKES TO THE WATERS
OFF THE MIDDLE ATLANTIC COAST EARLY THIS MORNING. THE BOUNDARY IS
EXPECTED TO WEAKEN AND DISSIPATE TODAY. MEANWHILE, ANOTHER FRONTAL
BOUNDARY FROM THE NORTH IS FORECAST TO DROP INTO NEW YORK AND NEW
ENGLAND. THE FRONT IS EXPECTED TO STALL ACROSS THAT AREA FOR
TONIGHT AND TUESDAY BEFORE LIFTING BACK TO THE NORTH. A COLD FRONT
IS FORECAST TO APPROACH FROM THE WEST ON THURSDAY AND IT SHOULD
PASS THROUGH OUR REGION ON THURSDAY NIGHT. HIGH PRESSURE IS
ANTICIPATED TO FOLLOW FOR THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
THE DENSE FOG...IN MOST AREAS...HAS THINNED AND VSBYS HAVE
INCREASED ABOVE A MILE IN MANY AREAS. WE HAVE DECIDED TO CANCEL
THE DENSE FOG ADVISORY FOR NOW...WITH THE CAVEAT THAT THERE WILL
STILL BE A FEW AREAS OF THICKER FOG FOR THE NEXT FEW HOURS. SKIES
WILL GRADUALLY BECOME PARTLY SUNNY BY NOON. A FEW SHOWERS WILL
AFFECT SRN DEL IN A FEW HOURS WITH SMALL CHC POPS INSERTED IN THE
GRIDS/WORDS.

ONCE THE REMAINDER FOG LIFTS, CLOUDS MAY BEGIN TO BREAK SOME THIS
AFTERNOON, WHICH WILL ALLOW THE ATMOSPHERE TO DESTABILIZE SOME. A
WEAK DISTURBANCE ALOFT IS EXPECTED TO CROSS THE AREA LATER TODAY,
AND WITH AMPLE LOW-LEVEL MOISTURE AND INSTABILITY, SCATTERED
SHOWERS AND THUNDERSTORMS CAN BE EXPECTED TO DEVELOP.

WE HAVE NOT MADE ANY TEMPERATURE CHANGES TO THE FCST AT THIS
POINT, THE MET/MAV MOS NUMBERS FROM BEFORE STILL LOOK GOOD.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
ANY SHOWERS/THUNDERSTORMS THAT DEVELOP DURING THE AFTERNOON
SHOULD DISSIPATE AFTER SUNSET AS DAYTIME HEATING IS LOST AND THE
WEAK DISTURBANCE ALOFT PASSES TO OUR EAST. AFTER THE SHOWERS
DISSIPATE, THERE IS A CHANCE FOR FOG TO DEVELOP ONCE AGAIN ACROSS
THE AREA AS THERE WILL STILL BE PLENTY OF LOW-LEVEL MOISTURE.
HOWEVER, SINCE WE WILL NOT BE ON THE NORTHERN SIDE OF ANY
BOUNDARY, AND WE EXPECT WINDS TO BE MORE FROM THE SOUTH-SOUTHWEST,
THE FOG SHOULD NOT BE AS WIDESPREAD OR AS DENSE AS THIS MORNING. A
BLEND OF THE MAV/MET MOS GUIDANCE WAS TAKEN FOR OVERNIGHT
TEMPERATURES AS THEY WERE ONCE AGAIN VERY SIMILAR.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
IT REMAINS A HIGH CONFIDENCE FORECAST THAT THE PERIOD FROM
TUESDAY THROUGH FRIDAY WITH BE RATHER UNSETTLED WITH THE POTENTIAL
FOR PRECIPITATION EACH DAY. HOWEVER, IT IS A LOW CONFIDENCE
FORECAST REGARDING THE DETAILS AND TIMING. NEVERTHELESS, THE WEEK
SHOULD NOT BE A TOTAL WASHOUT. MOST OF THE TIME, PRECIPITATION
WILL NOT BE FALLING.

THE MID LEVEL PATTERN IS EXPECTED TO FEATURE THE POLAR VORTEX
WELL TO OUR NORTHEAST WITH A CLOSED LOW OVER THE MIDDLE MISSOURI
RIVER VALLEY ON TUESDAY. THERE SHOULD BE A RIDGE EXTENDING FROM
THE WESTERN NORTH ATLANTIC NORTHWESTWARD TO THE GREAT LAKES. THE
POLAR VORTEX WILL REMAIN THE DOMINANT FEATURE OVER EASTERN CANADA
INTO THE WEEKEND. MEANWHILE, THE CLOSED LOW AND ITS ASSOCIATED
TROUGH WILL PROGRESS EASTWARD AND IT SHOULD START TO INTERACT WITH
THE POLAR VORTEX AROUND TUESDAY NIGHT AS THAT FEATURE`S INFLUENCE
BEGINS TO EXPAND TO THE WEST AND SOUTH. THE MID LEVEL TROUGH WILL
LIKELY MOVE EASTWARD ACROSS THE GREAT LAKES FROM WEDNESDAY NIGHT
INTO THURSDAY NIGHT. THE TROUGH`S AXIS SHOULD PASS OVER OUR REGION
IN THE FRIDAY INTO FRIDAY NIGHT TIME FRAME.

A SHOT OF VERY WARM AIR IS FORECAST TO PASS OVER OUR REGION FROM
TUESDAY INTO WEDNESDAY. TEMPERATURES AT 850 HPA ARE EXPECTED TO
RISE INTO THE +15C TO +17C RANGE. THE SURFACE FRONT FROM THE NORTH
IS NO LONGER FORECAST TO DROP INTO OUR REGION. AS A RESULT, WE
EXPECT AFTERNOON TEMPERATURES ON BOTH DAYS TO RISE WELL INTO THE
80S AT MOST LOCATIONS. THE MAIN EXCEPTION WILL BE AREAS ALONG AND
NEAR THE COAST WHERE A SEA BREEZE SHOULD KEEP READINGS FROM
GETTING OUT OF THE 70S AND 60S.

THE HEAT AND THE LOW LEVEL MOISTURE WILL RESULT IN UNSTABLE
CONDITIONS ESPECIALLY DURING THE AFTERNOON AND EVENING HOURS ON
TUESDAY AND WEDNESDAY. WE WILL CONTINUE TO MENTION A CHANCE OF
THUNDERSTORMS WITH SURFACE BASED CAPE VALUES POSSIBLY RISING INTO
THE 1500 TO 2000 J/KG RANGE ESPECIALLY FROM THE INTERSTATE 95
CORRIDOR NORTHWESTWARD. PRECIPITABLE WATER VALUES ARE ANTICIPATED
TO BE IN THE 1.25 TO 1.5 INCH RANGE ON TUESDAY AND AROUND OR
SLIGHTLY GREATER THAN 1.5 INCHES ON WEDNESDAY. AS A RESULT,
LOCALIZED DOWNPOURS REMAIN POSSIBLE..

THE 0000 UTC GFS AND THE 0000 UTC ECMWF ARE FAIRLY SIMILAR WITH
THE TIMING OF THE COLD FRONT APPROACHING FROM THE WEST. IT SHOULD
PASS THROUGH OUR REGION FROM LATE THURSDAY NIGHT INTO EARLY FRIDAY
MORNING. WE WILL CONTINUE TO MENTION A CHANCE OF SHOWERS AND
THUNDERSTORMS FOR THURSDAY INTO THURSDAY NIGHT WITH THE FEATURE.

WE WILL KEEP THE POSSIBILITY OF LINGERING SHOWERS IN THE FORECAST
FOR FRIDAY. DRY AIR SHOULD BEGIN TO BUILD INTO OUR REGION AT THAT
TIME AND FAIR WEATHER AND SLIGHTLY BELOW NORMAL TEMPERATURES ARE
ANTICIPATED FOR SATURDAY AND SUNDAY.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

IFR CONDITIONS PREVAIL ACROSS ALL TAF SITES EARLY THIS MORNING.
CONDITIONS ARE EXPECTED TO SLOWLY IMPROVE THIS MORNING AS A
FRONTAL BOUNDARY SLOWLY LIFTS ACROSS THE AREA. SITES ARE EXPECTED
TO BECOME MVFR/VFR BY LATE MORNING/EARLY AFTERNOON. SCATTERED
SHOWERS AND A FEW ISOLATED THUNDERSTORMS ARE POSSIBLE TODAY,
ESPECIALLY THIS AFTERNOON. CONFIDENCE IN THUNDERSTORMS OCCURRING
IS LOW, SO THEY WERE NOT INCLUDED IN THE TAFS. WINDS THIS MORNING
WILL VARY FROM MORE OF AN EASTERLY DIRECTION NORTH OF THE FRONTAL
BOUNDARY, TO MORE SOUTHERLY SOUTH OF THE BOUNDARY. WINDS WILL
BECOME MORE SOUTH-SOUTHWESTERLY EVERYWHERE LATER THIS MORNING AND
THIS AFTERNOON.

ANY SHOWERS THAT DEVELOP SHOULD DISSIPATE BY SUNSET. FOG/LOW
CLOUDS ARE ONCE AGAIN EXPECTED TO DEVELOP OVERNIGHT MONDAY INTO
TUESDAY MORNING. MVFR/IFR CONDITIONS ARE EXPECTED TO DEVELOP, BUT
SHOULD NOT BE AS LOW AS THIS MORNING.

OUTLOOK...
TUESDAY THROUGH THURSDAY...MAINLY VFR. HOWEVER, MVFR AND IFR
CONDITIONS ARE POSSIBLE ESPECIALLY DURING THE LATE NIGHT AND EARLY
MORNING HOURS EACH DAY. ALSO, THERE WILL BE A CHANCE OF SHOWERS
AND AFTERNOON AND EVENING THUNDERSTORMS WHICH COULD LOWER CEILINGS
AND REDUCE THE VISIBILITY AT TIMES.

THURSDAY NIGHT...MAINLY VFR. THERE IS A CHANCE OF SHOWERS AND
EVENING THUNDERSTORMS WHICH COULD LOWER CEILINGS AND REDUCE THE
VISIBILITY AT TIMES.

FRIDAY...MAINLY VFR WITH A CHANCE OF SHOWERS.

&&

.MARINE...
-- Changed Discussion --
THE DENSE FOG ADVISORY ON THE NRN TWO NJ COASTAL WATER ZONES HAS
BEEN EXTENDED UNTIL NOON.

A SMALL CRAFT ADVISORY REMAINS ACROSS THE ATLANTIC COASTAL WATERS
THROUGH LATE THIS AFTERNOON AS SEAS ARE EXPECTED TO REMAIN NEAR 5
FEET ACROSS THE WATERS. EVEN THOUGH WINDS MAY NOT REACH 25 KNOTS,
THEY COULD PERIODICALLY GUST AROUND 20 KNOTS. WIND DIRECTION
ACROSS THE WATERS WILL VARY THIS MORNING DEPENDING ON WHICH SIDE
OF THE FRONTAL BOUNDARY ONE IS. NORTH OF THE BOUNDARY, WINDS WILL
BE MORE EASTERLY; SOUTH OF THE BOUNDARY WINDS WILL BE MORE SOUTH-
SOUTHWESTERLY. WINDS WILL BECOME SOUTH-SOUTHWESTERLY EVERYWHERE
LATER TODAY AFTER THE BOUNDARY AS LIFTED OR DISSIPATED ACROSS THE
ARE.

WE HAVE DECIDED NOT TO EXTEND THE ADVISORY OVERNIGHT MONDAY AS
CONFIDENCE IS NOT HIGH ENOUGH ON WAVES REMAINING 5 FEET OR
GREATER. WE WILL LET LATER SHIFTS TAKE A LOOK AND SEE IF THEY NEED
TO EXTEND THE ADVISORY.

OUTLOOK...
HIGH PRESSURE TO OUR EAST WILL CONTINUE TO INFLUENCE THE COASTAL
WATERS OF NEW JERSEY AND DELAWARE DURING THE MID WEEK PERIOD. A
COLD FRONT FROM THE WEST IS EXPECTED TO ARRIVE EARLY ON FRIDAY.

WIND SPEEDS ARE FORECAST TO REMAIN LESS THAN 25 KNOTS FROM
TUESDAY THROUGH FRIDAY WITH ONE EXCEPTION. WIND GUSTS MAY APPROACH
25 KNOTS ON OUR OCEAN WATERS FROM WEDNESDAY NIGHT INTO THURSDAY IN
THE STRENGTHENING SOUTH TO SOUTHWEST FLOW AHEAD OF THE APPROACHING
COLD FRONT. WAVE HEIGHTS ON OUR OCEAN WATERS MAY ALSO BUILD TO
AROUND 5 FEET AT THAT TIME.

MOIST AIR WILL REMAIN OVER THE COASTAL WATERS FROM TUESDAY
THROUGH THURSDAY NIGHT. DEW POINT TEMPERATURES WILL BE NEAR THE
WATER TEMPERATURES. AS A RESULT, THE POTENTIAL FOR FOG EXISTS AND
IT MAY BECOME DENSE AT TIMES.
-- End Changed Discussion --

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR
     ANZ450>455.
     DENSE FOG ADVISORY UNTIL NOON EDT TODAY FOR ANZ450-451.
-- End Changed Discussion --

&&

$$
SYNOPSIS...IOVINO
NEAR TERM...PO/ROBERTSON
SHORT TERM...ROBERTSON
LONG TERM...IOVINO
AVIATION...IOVINO/ROBERTSON
MARINE...IOVINO/ROBERTSON