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000
FXUS61 KPHI 141929
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
329 PM EDT TUE MAY 14 2013

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE SOUTHEAST COAST TONIGHT AND OUT TO
SEA INTO THURSDAY. A WARM FRONT IS FORECAST TO LIFT THROUGH OUR AREA
ON EARLY WEDNESDAY, FOLLOWED BY A COLD FRONT WEDNESDAY NIGHT. THIS
FRONT WILL SAG TO OUR SOUTH AND STALL FOR THE LATE WEEK PERIOD AND
INTO THE WEEKEND. THE FRONT MAY LIFT BACK NORTHWARD ACROSS THE AREA
AS A WARM FRONT EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
RAPIDLY THICKENING AND LOWERING CIGS ...THE BAND YOU SEE ON 19Z
SATELLITE IMAGERY FROM MICHIGAN TO W PTNS PA AND NYS. SCT LIGHT
SHOWERS EXPECTED...MOSTLY TRACE...AFTER MIDNIGHT AND MODELED IMO
PRETTY WELL BY THE 00Z/14 NSSL WRF AND NOW THE 18Z RAP...FLYING
SEWD 30-40 KT. LIGHT S WIND IN THE WAA PATTERN BEHIND THE
DEPARTING SFC HIGH OFF THE SE USA COAST.

50 50 BLENDED 12Z/14 NCEP MOS GUIDANCE FOR TEMPS/WINDS/DEWS.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
WEDNESDAY...THE 12Z GFS LOOKS LIKE MY IDEA OF A BEST MODEL SOLN OF
THE 12Z INTERNATIONAL SUITE. THE 12/14 GFS IMO HAS THE RIGHT IDEA
ABOUT STRONG CONVECTION AND PROBABLY STREAMING EAST SOUTHEAST FROM
SOUTHERN PA ACROSS S NJ AND OR THE DELMARVA LATE IN THE DAY WEDNESDAY.
SPC 1715Z SWODY2 ASSESSMENT MATCHES MY THINKING.

THE INCREASING BOUNDARY LAYER MOISTURE MAY BE OVERDONE BY THE MODELS,
THUS LIMITING INSTABILITY AND THE POTENTIAL FOR INITIATING CONVECTION.

THE 18Z GFS LAMP HAS GRIDDED LAMP TSTM PROBS IN W NYS AND NW PA BY
14Z.

MODEL REMNANTS OF AN EML NOW SPREADING EWD FROM THE MIDWEST THAT
SUPPORTS CONCERN FOR HAILERS....INCREASING THE 700-500MB LAPSE
RATES LATE IN THE DAY.

MORE THAN ADEQUATE BULK SHEAR FOR SVR WIND... AND SO THE QUESTION
BECOMES...IS THERE ENOUGH MOISTURE TO SUPPORT TSTM GENERATION. 12Z/14
GFS ML CAPE IS ONLY 600J LATER IN THE DAY AND SO DID NOT WORD HAIL
OR GUSTY WINDS IN THE ZONE PRODUCTS.

OTRW TEMPS/WINDS/DEWS ARE 50 50 BLENDED 12Z/14 NCEP MOS GUIDANCE
WITH A LEAN TO A WARMER TEMP SOLN SINCE MOST OF THE DAY SHOULD
BE RAINFREE.

CONFIDENCE ON POPS IS BELOW AVG AND I MAY BE OVER FCST THE CHC OF
A SHOWER OR TSTM WED AFTN.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
THE WARM FRONT IS PROGGED TO BE NORTH OF OUR REGION BY EARLY
THURSDAY, WITH SOME SUN AND WARM TEMPERATURES IN STORE FOR
THURSDAY. MUCH OF THE REGION SHOULD PEAK IN THE UPPER 70S TO LOWER
80S FOR HIGH TEMPERATURES. BY MID TO LATE DAY, A WEAK COLD FRONT
WILL BE APPROACHING FROM THE WEST, AND THERE LOOKS TO BE ENOUGH
MODELED INSTABILITY TO TRIGGER SCATTERED SHWRS/T-STORMS, WITH THE
BEST CHANCES OVER OUR DELMARVA REGION. THIS FRONT MAY STALL FOR A
TIME JUST TO THE SOUTH OF OUR AREA, ESPECIALLY THROUGH THURSDAY
NIGHT AND INTO EARLY FRIDAY, AND WE HAVE ADDED POPS ACROSS OUR
SOUTHERN ZONES TO INDICATE AN ONGOING CHANCE FOR SCATTERED
SHWR/T-STORM ACTIVITY. OTHERWISE FARTHER NORTH, THROUGH EASTERN PA
AND MUCH OF NJ, MOST OF FRIDAY AND SATURDAY SHOULD FEATURE DRY
CONDITIONS WITH SOME SUN AND MILD TEMPERATURES REACHING INTO THE
MIDDLE AND UPPER 70S. WEAK HIGH PRESSURE WILL THEN SHIFT EAST AND
AWAY FROM THE REGION BY SUNDAY. FROM THERE, MODEL DIFFERENCES
INCREASE, BUT THE OVERALL PICTURE FROM SUNDAY AND INTO EARLY NEXT
WEEK HAS UNSETTLED WEATHER IN PLACE ACROSS OUR REGION, WITH THE
POTENTIAL FOR MORE SCATTERED SHWR/T-STORM ACTIVITY. WE USED A
BLEND OF WPC GUIDANCE WITH CONTINUITY AT THIS EXTENDED TIMEFRAME
AND KEPT CHANCE POPS IN PLACE.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

REMAINDER THIS AFTERNOON...VFR WITH CIRRUS DEVELOPING SEWD. WNW
WIND WIND GUSTS GENERALLY LESS THAN 17 KT.

TONIGHT...VFR CIGS AOA 7000 FT DEVELOPING FM WNW TO ESE WITH SCT
SPRINKLES OR LIGHT .02/HR SHOWERS STREAMING SEWD 30-40 KT AFTER
04Z. LIGHT SOUTH SFC WIND.

WEDNESDAY...VFR SCT-BKN CLOUDS AOA 5000 FT WITH ONLY A SMALL
CHANCE OF A LEFTOVER SHOWER POSSIBLE IN THE MORNING BUT A BAND OF
SCT-BKN SHOWERS AND ISO STRONG TSTMS EXPECTED LATE IN THE DAY...
PROBABLY MOVING ESEWD THRU SE PA NEAR KPHL. SSW WIND GUSTS 15 KT
IN THE AFTN. STRONGER WLY GUST TO 35 KT `POSSIBLE` IN A LATE DAY
TSTM VCNTY KPHL. CONFIDENCE ON THUNDERSTORM INITIATION WED AFTN IN
SRN PA IS BELOW AVG DUE TO MOST MODELS NOT FCSTG MUCH IF ANY
SHOWER ACTIVITY.

OUTLOOK...

WEDNESDAY NIGHT...MOSTLY VFR CONDITIONS EXPECTED. SOME
LOWERING TO MVFR CIGS/VSBYS POSSIBLE IN SCATTERED SHWRS/T-STORMS,
MAINLY EVENING.

THURSDAY...MOSTLY VFR CONDITIONS. A WEAK COLD FRONT MAY TRIGGER
SCATTERED SHOWERS IN AFTN TO EVE, WITH POSSIBLE BRIEF LOWERING MVFR.

FRIDAY AND SATURDAY...MAINLY VFR CONDITIONS.

&&

.MARINE...
HIGH PRESSURE WILL MOVE OVER THE SERN CONUS TODAY AND THEN FURTHER
EWD OVER THE SERN COASTAL WATERS TONIGHT. AS A RESULT THE WIND
AND SEAS ARE EXPECTED TO REMAIN BELOW SCA CRITERIA THRU THE NEAR
PERIOD.

WEDNESDAY...GUIDANCE INDICATES OUR COASTAL WATERS WILL REACH SCA
WIND GUSTS DURING THE DAYTIME WEDNESDAY WITH SEAS BUILDING TO 5
FT ON THE ATLC WATERS DURING THE AFTN GENERATED BY THE SLY FLOW
AHEAD OF AN APPROACHING WFRONT. FOR LOWER DE BAY THERE MAY BE A
PERIOD OF SCA WIND GUSTS WEDNESDAY BUT CONFIDENCE WAS NOT HIGH
ENOUGH AT THIS TIME TO INCLUDE THIS AS A HEADLINE.

AM STARTING THE SCA A BIT SOONER ON THE ATLC WATERS WEDNESDAY...
AROUND 12Z. WILL LEAVE IT TO THE MID SHIFT TO ISSUE FOR DE BAY.

OUTLOOK...
THE WARM FRONT WILL BE LIFTING NORTHEASTWARD THROUGH THE REGION
WEDNESDAY NIGHT. SCA CONTINUES THROUGH 12Z THURSDAY. THIS SCA MAY
POSSIBLY NEED TO BE EXTENDED FURTHER INTO THURSDAY, DEPENDING ON
HOW QUICKLY THE SEAS DIMINISH. ONCE SEAS SUBSIDE ON OUR COASTAL
WATERS THURSDAY, WE ANTICIPATE SUB-SCA CONDITIONS FOR OUR WATERS
THROUGH FRIDAY AND SATURDAY AS WEAK HIGH PRESSURE SETTLES ACROSS
THE REGION.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 11 AM WEDNESDAY TO 8 AM EDT THURSDAY
     FOR ANZ450>455.

&&

$$
SYNOPSIS...KLINE/ROBERTSON 327
NEAR TERM...DRAG 327
SHORT TERM...DRAG 327
LONG TERM...KLINE
AVIATION...DRAG/KLINE 327
MARINE...DRAG/KLINE 327