Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 211424
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
1024 AM EDT THU AUG 21 2014

.SYNOPSIS...
LOW PRESSURE FROM LAKE ONTARIO TO VIRGINIA PRODUCES OCCASIONALLY
UNSETTLED WEATHER HERE THROUGH FRIDAY. QUEBEC HIGH PRESSURE BECOMES
OUR PRIMARY WEATHER INFLUENCE LATER THIS WEEKEND THROUGH THE MIDDLE
OF NEXT WEEK AS THE HIGH SETTLES SOUTHWARD TO THE MID ATLANTIC STATES.

&&

.NEAR TERM /THROUGH TONIGHT/...
1010AM ESTF HAS REDUCED RAIN CHANCES ALONG THE COAST AND ENHANCED
THE WORDING IN NE PA AND NW NJ IN PART DUE TO THE 12Z NAM AND
PRIOR ECMWF MASS FIELD PREDICTORS. THE EXTRA CLOUD COVER AND HIGHER
THAN MODELED SFC DEWPOINTS IN SE PA N MD ALSO SUGGEST GREATER POTENTIAL
INSTABILITY FOR MID AFTN DEVELOPMENT.

12Z SOUNDING FROM IAD/WAL/APG AND OKX REVIEWED. MAX TEMPS 83-86.

UNSETTLED WITH POTENTIAL FOR BRIEF POOR DRAINAGE FLOODING AND SMALL
HAIL PRODUCING THUNDERSTORMS (G35KT)...PARTICULARLY NE PA AND NW
NJ...AND THINKING AKIN TO THE 00Z/21 NSSL WRF AN IN WEAK WAA AHEAD
OF THE SFC TROUGH IN CENTRAL PA. THAT DOESN`T RULE OUT THE DELMARVA
BUT FOR SOME TIME NOW...IT APPEARS INSTABILITY AND PROXIMITY TO
THE COLD TROUGH ALOFT HAS FOCUSED NORTH RATHER THAN SOUTH. PWAT
NEAR 1.5 INCHES. MLCAPE 400-600J. MARGINAL 0-6KM BULK SHEAR.

OTRW...A NICE DAY WITH TEMPS NEAR OR SLIGHTLY ABOVE NORMAL UNDER
MIXED SUN AND CLOUDS. THERE IS STILL MUCH MORE LOW CLOUDINESS OVER
SE PA...NE MD AND N DE THIS MORNING THAN ANTICIPATED YDY. THIS
SHOULD START THINNING AND LIFTING BY NOON.

PLEASE FOLLOW ANY UPDATED SWOMCD`S SWODY1 AND LOCAL PHI PRODUCTS.

TONIGHT...A COUPLE OF BANDS OF SHOWERS AND ISOLATED TSTMS IN THE
STILL UNSTABLE AIRMASS. SHOWERS SHOULD DIMINISH LATE.

NOTING THE 12Z NAM CONTG A THEME OF 2INCH HOURLY TSTMS SOMEWHERE
IN E CENTRAL PA INTO CENTRAL NJ THIS EVENING. WHILE THE PLACEMENT
IS POSSIBLY WRONG...THE IDEA I THINK IS CORRECT. A PTN OF E CENTRAL
OR NE PA IN N OR CENTRAL NJ SHOULD RECEIVE SOME STRONG TSTORMS
VERY LATE THIS AFTN OR EVENING.

&&

.SHORT TERM /FRIDAY/...
1000J OF MLCAPE AND SLIGHTLY STRONGER 0-6KM BULK SHEAR CUES INTEREST
IN CONVECTION FRI AFTN. SREF HAS DECENT PROBS FOR SHOWERS...ESPECIALLY
E PA...S NJ AND THE DELMARVA.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
FRIDAY NIGHT THROUGH SATURDAY...THE REGION REMAINS UNDER
NORTHWEST FLOW AS THE STOUT RIDGE REMAINS OVER THE MISSISSIPPI
VALLEY, AND THE OTHER HIGH REMAINS OVER EASTERN CANADA. WITH THE
NORTHWEST FLOW, EXPECT A FEW EMBEDDED SHORT WAVE TROUGHS TO BRING
CHANCES FOR THUNDERSTORMS THROUGH THIS PERIOD. HOWEVER, THE TIMING
OF THE INDIVIDUAL SHORT WAVE TROUGHS REMAINS UNCERTAIN.

SUNDAY THROUGH THURSDAY...THE HIGH OVER EASTERN CANADA BUILDS SOUTH.
WITH THE ASSOCIATED COLD AIR ADVECTION, COULD SEE HIGHS ESPECIALLY
EARLY IN THE WEEKEND 5 TO 10 DEGREES BELOW NORMAL. BY TUESDAY
HOWEVER, THE HIGH STARTS TO SHIFT OFF SHORE, LEAVING THE REGION
UNDER SOUTHERLY FLOW AND LEADING TO A MODEST WARMING TREND. HOWEVER,
ALSO TOWARDS THE END OF THIS FORECAST PERIOD THE GFS AND ECMWF
SOLUTIONS DIFFER GREATLY ON THE TIMING OF AN UPPER LEVEL TROUGH AND
ASSOCIATED SURFACE COLD FRONT THAT WILL BE PROPAGATING EAST ON THE
HEALS OF THE HIGH. STILL, BOTH SOLUTIONS SHOW THESE FEATURES JUST
BEYOND THE SEVEN DAY FORECAST.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

TODAY...PERIOD OF MVFR CIGS IN E PA NE MD AND N DE THROUGH 16Z OTRW
VFR SCT-BKN AOA 4000 FT THIS AFTERNOON BUT LOCAL IFR CONDS IN SCT
SHOWERS AND TSTMS THIS AFTN. LIGHT SOUTH WIND. BUT A NW WIND GUST
TO 35 KT POSSIBLE ASSOCIATED WITH AN AFTN TSTM NEAR AND N OF KABE.

TONIGHT...VFR CIGS MAY DEGRADE TO MVFR CONDS IN FOG LATE. IFR
CONDS IN LEFTOVER EARLY NIGHT SHOWERS AND TSTMS.

FRIDAY...CIGS 2500-4000 FT WITH LOWER IFR CONDS IN SCT SHOWERS AND
TSTMS AND A WIND TURNING LIGHT EASTERLY.

OUTLOOK...
FRIDAY AND SATURDAY...MOSTLY VFR. ISOLATED TO SCATTERED TSRA ARE
POSSIBLE ACROSS THE REGION. UNDER ANY TSRA MVFR CEILINGS AND
BRIEF IFR VISIBILITIES WILL BE POSSIBLE.

SUNDAY THROUGH MONDAY...GENERALLY VFR.

&&

.MARINE...
SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED THROUGH FRIDAY WITH SEAS
3 FEET OR LESS AND SOUTH TO SOUTHEAST WINDS 5 TO 10 KNOTS BECOMING
EASTERLY FRIDAY.

WE`VE NOT SEEN ANY NEW MAREPS THIS WEEK FROM MARINERS IN OUR EASY
USE (INTERNET AND/OR SMART PHONE) LINK WWW.WEATHER.GOV/PHI/MAROBSFORM
THIS HAS BEEN DERIVED FOR THE MARINER TO EASILY POST INFO INSTANTLY
TO THE NWS FOR USE IN OUR MARINE PRODUCTS.

OUTLOOK...
FRIDAY NIGHT...SCA NE WIND GUSTS MAY DEVELOP LATE AT NIGHT ON THE
ATLC WATERS.

SATURDAY...OCCASIONAL GUSTS NEAR 25 KT AND WAVE HEIGHTS APPROACHING
5 FT ARE POSSIBLE ESPECIALLY SATURDAY AFTERNOON THROUGH SATURDAY
NIGHT.

SUNDAY AND MONDAY...WAVE HEIGHTS AND WINDS SLOWLY FALLING BELOW
SMALL CRAFT ADVISORY CRITERIA SUNDAY MORNING AND SHOULD REMAIN
BELOW CRITERIA THROUGH MONDAY.

&&

.CLIMATE...
WE RCD INQUIRY ON HOW THE CLIMATE PROGRAM SELECTS FOR OUR 530 PM
CLI. OUR PROGRAM SEARCHES MAX/MIN TEMP DATA FOR THE DAY ENDING 5PM
SHARP. THAT DATA IS INGESTED INTO THE 530 PM POSTED CLI. IF A MAX
TEMP OCCURS THEREAFTER...IT IS REFLECTED IN THE END OF DAY SUMMARY
POSTS AROUND 230 AM EDT THE NEXT DAY AND ALSO YOU CAN CHECK THE 8
PM RTPPHI WHICH POSTS AROUND 815 PM EDT.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...DRAG/JOHNSON
NEAR TERM...DRAG  1023
SHORT TERM...DRAG 1023
LONG TERM...JOHNSON
AVIATION...DRAG/JOHNSON 1023
MARINE...DRAG/JOHNSON
CLIMATE...






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