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Area Forecast Discussion
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000
FXUS61 KPHI 230419
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1219 AM EDT WED APR 23 2014

.SYNOPSIS...
A COLD FRONT WILL CROSS THE AREA THIS EVENING. HIGH PRESSURE WILL
THEN BUILD IN BEHIND THE FRONT FOR WEDNESDAY AND THURSDAY. THE
HIGH COMBINED WITH LOW PRESSURE EAST OF NEW ENGLAND WILL RESULT IN
GUSTY NORTHWEST WINDS ON WEDNESDAY AND THURSDAY. ANOTHER AREA OF LOW
PRESSURE WILL MOVE TO THE NORTH AND BRING A WEAK FRONT THROUGH THE
REGION LATE FRIDAY INTO EARLY SATURDAY, FOLLOWED BY MORE HIGH
PRESSURE AND FAIR WEATHER FOR SUNDAY. ANOTHER STORM SYSTEM
APPROACHES SLOWLY FROM THE SOUTHWEST AND BEGINS TO AFFECT OUR
REGION LATER MONDAY INTO TUESDAY.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
THE FRONT IS THRU THE REGION AND PRECIP HAS ALL BUT ENDED. WIND
HAS BECOME W TO NW OVER THE AREA AND WHILE THERE ARE STILL SOME
POCKETS OF CLOUDS, THE SKY HAS BEGUN TO CLEAR.

PREVIOUS NEAR TERM DISCUSSION...THROUGH LATE-DAY, A COLD FRONT
WILL CONTINUE TO SLOWLY PROGRESS EASTWARD, EVENTUALLY CROSSING OUR
FORECAST AREA BY LATE EVENING. MODEL GUIDANCE AND ACTUAL
OBSERVATIONS TO OUR WEST CONTINUE TO SHOW LIMITED MOISTURE WITH
THIS FRONTAL PASSAGE, AND MOST AREAS WILL ONLY SEE A TENTH TO
PERHAPS TWO TENTHS OF AN INCH OF RAIN FROM SHOWERS AS THE FRONT
PASSES THROUGH THE REGION. THERE IS ALSO LIMITED INSTABILITY
THROUGH LATE-DAY AND THIS EVENING, BUT WE DID KEEP SLIGHT
CHANCE/ISOLATED THUNDER IN THE FORECAST BASED ON FORECAST CAPES
OFF THE GFS/NAM AND ECMWF. WINDS WILL CONTINUE TO BE OUT OF THE
SOUTHWEST EARLY, THEN BECOMING MORE WESTERLY FOLLOWING THE FRONTAL
PASSAGE. WE QUICKLY DECREASE POPS AFTER ABOUT 01Z FROM WEST TO
EAST ACROSS THE FORECAST AREA AS THE FRONT ADVANCES TOWARD THE
COAST AND OFFSHORE. THROUGH THE OVERNIGHT HOURS THEN, COOLER AND
DRIER AIR WILL BEGIN TO OVERSPREAD THE REGION ON GUSTY NORTHWEST
WINDS. IN FACT, THROUGH THE EARLY MORNING HOURS, NORTHWEST WINDS
GUSTING BETWEEN 20 TO 25 MPH ARE ANTICIPATED. FOR TEMPERATURES, WE
MOSTLY TOOK A MET/MAV GUIDANCE BLEND WITH SOME LOCAL ADJUSTMENTS
AND EXPECT LOWS TO BE MAINLY IN THE 40S ACROSS THE REGION.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/...
A WINDY AND DRY DAY IS EXPECTED ON WEDNESDAY AS STRENGTHENING LOW
PRESSURE LINGERS TO OUR NORTH OVER THE NEW ENGLAND STATES AND HIGH
PRESSURE ACROSS THE GREAT LAKES AND MIDWEST GRADUALLY BUILDS
EASTWARD THROUGH THE DAY. WITH THE STRONG PRESSURE GRADIENT
BETWEEN THESE TWO SYSTEMS, GUSTY NORTHWEST WINDS WILL BE FELT
ACROSS OUR FORECAST AREA THROUGH THE DAY, WITH GUSTS INTO THE 30
TO 35 MPH RANGE. WITH A MID-LEVEL TROUGH PASSING OVERHEAD, A
COUPLE OF ISOLATED SHOWERS OVER THE HIGHER TERRAIN OF OUR FAR
NORTHWEST ZONES CANNOT BE RULED OUT, BUT OTHERWISE, DRY CONDITIONS
AND SOME SUNSHINE ARE EXPECTED. DAYTIME TEMPERATURES ARE EXPECTED
TO BE AROUND 10 TO 15 DEGREES COOLER THAN TUESDAY, WITH 850/925MB
TEMPS SUPPORTING HIGHS REACHING MOSTLY IN THE UPPER 50S TO LOWER
60S FOR MUCH OF THE REGION.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
HIGH PRESSURE WILL BE BUILDING OUT OF THE GREAT LAKES REGION
TOWARD OUR AREA AT THE BEGINNING OF THIS TIME PERIOD WHILE A
STRONG LOW PRESSURE SYSTEM NEAR MAINE MOVES SLOWLY AWAY. THE
PRESSURE GRADIENT BETWEEN THE TWO SYSTEM WILL RESULT IN STRONG
WINDS OVER AREA FOR WEDNESDAY NIGHT INTO THURSDAY.

SIGNIFICANT FIRE WEATHER THREAT POSSIBLE ON THURSDAY WITH THE
COMBINED AFFECT OF THE STRONG WINDS AND DAYTIME RELATIVE HUMIDITIES
DROPPING BELOW 25 PERCENT FOR THE AREA.  

FOR WEDNESDAY NIGHT INTO FRIDAY...USED A MET/MAV BLEND FOR
TEMPERATURES.

NEXT STORM SYSTEM PASSING BY TO OUR NORTH LATE FRIDAY INTO EARLY
SATURDAY BRINGS ANOTHER FRONT THROUGH THE REGION. USED WPC SURFACE
FRONT FORECAST FOR PRECIPITATION/WIND TIMING. END RESULT WAS VERY
LITTLE CHANGE FROM WHAT WAS PREVIOUSLY IN THE GRIDS.  

FOR FRIDAY NIGHT INTO TUESDAY...USED WPC EXTENDED RANGE GUIDANCE
AS FIRST GUESS FOR GRIDS. ONLY MINOR MODIFICATIONS MADE TO THAT
DATA SET. 

NEXT STORM SYSTEM TO AFFECT THE REGION WILL BE LATER MONDAY INTO
TUESDAY. THIS IS A SLOW MOVING SYSTEM PER WPC MAPS AND DISCUSSION.
TRIMMED BACK PRECIPITATION START TIME IN PREVIOUS FORECAST TO
LATER ON MONDAY. ADDITIONAL ADJUSTMENTS MAY BE NEEDED DOWN THE ROAD
AS SLOW MOVING SYSTEMS TEND TO BE EVER SLOWER THAN INITIALLY
FORECAST. 

REVIEWING THE FORECAST TEMPERATURES FOR THIS TIME PERIOD...
OVERALL VERY CLOSE TO SEASONAL NORMS.

&&

.AVIATION /04Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

EVENING UPDATE...THE THUNDERSTORM THREAT IS GENERALLY OVER FOR
MOST TERMINALS. THERE IS A SMALL THREAT THAT MVFR CEILINGS WILL
DEVELOP BEHIND THE COLD FRONT THAT WILL MOVE THROUGH THE REGION
SHORTLY, BUT IT IS TOO SMALL OF A THREAT TO MENTION IN THE TAFS
NOW.

PREVIOUS AVIATION DISCUSSION...MAINLY VFR CONDITIONS WILL CONTINUE
LATE-DAY AND THIS EVENING; ALTHOUGH, A BRIEF REDUCTION TO MVFR IS
POSSIBLE IN RAIN SHOWERS, MAINLY DUE TO REDUCED VISIBILITIES.
WHILE ISOLATED TSTMS CANNOT BE RULED OUT, WE HAVE LOW CONFIDENCE
IN THUNDER FOR THE TAF SITES...SO THIS WAS NOT INCLUDED IN THE
TAFS. WINDS WILL TURN FROM THE SOUTHWEST TO WEST WITH THE FRONTAL
PASSAGE THIS EVENING AND BECOME GUSTY AND OUT OF THE NORTHWEST
DURING THE OVERNIGHT HOURS. GUSTS TO BETWEEN 20 TO 25 KNOTS CAN BE
EXPECTED DURING THE OVERNIGHT HOURS, WITH GUSTS IN THE 30 KNOT
RANGE DURING THE DAYTIME WEDNESDAY. OTHERWISE, VFR AND DRY
CONDITIONS ARE EXPECTED THROUGH THE DAYTIME WEDNESDAY.
                      
OUTLOOK...
WED NIGHT THROUGH THU...VFR CONDS WITH NW WINDS IN THE 20 TO 30 KT
RANGE. HIGH CONFIDENCE.

FRI THROUGH SAT...MAINLY VFR BUT LOCALLY MVFR IN SCATTERED
SHOWERS FRI NIGHT INTO EARLY SAT. MDT CONFIDENCE.

SUN...VFR CONDITIONS.  MODERATE CONFIDENCE.

&&

.MARINE...
WITH THE AFTERNOON PACKAGE, WE DECIDED TO UPGRADE THE GALE WATCH TO 
A GALE WARNING FOR OUR ATLANTIC COASTAL WATERS, BEGINNING AT 12Z 
WEDNESDAY AND LASTING INTO THE DAYTIME THURSDAY. WIND GUSTS AND SEAS 
WILL BEGIN TO INCREASE INTO SCA TERRITORY DURING THE OVERNIGHT HOURS 
FOLLOWING A COLD FRONTAL PASSAGE. DURING THE DAYTIME WEDNESDAY AND 
INTO THURSDAY GALE FORCE WIND GUSTS AROUND 35 KNOTS PLUS ARE 
EXPECTED. FOR DELAWARE BAY, WE MAINTAIN THE SMALL CRAFT ADVISORY AND 
EXTENDED IT INTO THE DAYTIME THURSDAY. WIND GUSTS FOR THE BAY SHOULD 
PRIMARILY TOP OUT AROUND 30 KNOTS DURING WEDNESDAY. 
 
OUTLOOK...

WED NIGHT THROUGH THU...GALE FORCE GUSTS LIKELY ON THE OCEAN WITH
GUSTS AROUND 35 KT AND POSSIBLY HIGHER. A GALE WARNING HAS NOW BEEN
ISSUED. WIND SUBSIDING LATER THU.

FRI THROUGH SUN...NO MARINE HEADLINES ARE ANTICIPATED AT THIS
TIME, THOUGH WE COULD APPROACH SCA WIND BY SAT NIGHT.

&&

.FIRE WEATHER...
A FIRE WEATHER WATCH HAS BEEN ISSUED FOR WEDNESDAY. NORTHWEST
WINDS WITH GUSTS OVER 30 MPH WILL BE WELL OVER FIRE WEATHER CRITERIA.
RH VALUES MAY STAY ABOVE 30 PERCENT ON WEDNESDAY BUT FUEL MOISTURE
VALUES WILL ALSO BE A PROBLEM AS RAINFALL TONIGHT IS EXPECTED TO
BE LIGHT. BOTTOM-LINE IS THAT THERE IS ENOUGH OF A RISK BASED ON
THE WINDS AND FUEL MOISTURE TO JUSTIFY A WATCH FOR WEDNESDAY.

PROBLEMS ARE LIKELY TO CONTINUE INTO THURSDAY. THOUGH WINDS GUSTS MAY
BE A LITTLE LOWER, RH VALUES WILL DROP BELOW 20% IN MANY LOCATIONS
THURSDAY AFTERNOON AND FUEL MOISTURE LEVELS WILL CONTINUE TO BE A
PROBLEM. MONITOR THE FORECAST AS FIRE WEATHER HEADLINES MAY BE
REQUIRED ON THURSDAY.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...FIRE WEATHER WATCH FROM 11 AM EDT THIS MORNING THROUGH THIS 
     EVENING FOR PAZ054-055-060>062-070-071-101>106.
NJ...FIRE WEATHER WATCH FROM 11 AM EDT THIS MORNING THROUGH THIS 
     EVENING FOR NJZ001-007>010-012>027.
DE...FIRE WEATHER WATCH FROM 11 AM EDT THIS MORNING THROUGH THIS 
     EVENING FOR DEZ001>004.
MD...FIRE WEATHER WATCH FROM 11 AM EDT THIS MORNING THROUGH THIS 
     EVENING FOR MDZ008-012-015-019-020.
MARINE...GALE WARNING FROM 8 AM THIS MORNING TO NOON EDT THURSDAY FOR 
     ANZ450>455.
     SMALL CRAFT ADVISORY UNTIL NOON EDT THURSDAY FOR ANZ430-431.

&&

$$
SYNOPSIS...SZATKOWSKI
NEAR TERM...JOHNSON/KLINE/NIERENBERG
SHORT TERM...KLINE
LONG TERM...SZATKOWSKI
AVIATION...SZATKOWSKI/JOHNSON/KLINE
MARINE...SZATKOWSKI/KLINE
FIRE WEATHER...






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