Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 201343
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
943 AM EDT WED AUG 20 2014

.SYNOPSIS...
LOW PRESSURE IN GREAT LAKES REGION WILL WEAKEN AS IT MOVES TO NEAR LAKE
ONTARIO THURSDAY. A SECOND AREA OF LOW PRESSURE WILL DEVELOP NEAR
THE CHESAPEAKE BAY THURSDAY NIGHT. HIGH PRESSURE IN EASTERN CANADA
WILL BUILD DOWN ALONG THE EAST COAST LATER THIS WEEKEND INTO NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
830 AND 930 AM AFD UPDATES:

MIXED CLOUDS AND SUN PROBABLY FAVORING MORE SUN. ANOTHER NICE
DAY.

A COMPLEX OF SHOWERS AND STORMS IN WPA/WVA ASSOCIATED WITH A MID-
LVL SHORTWAVE TROUGH OUT AHEAD OF THE GREAT LAKES LOW SHOULD WEAKEN
AS IT MOVES EASTWARD INTO AN INCREASINGLY STABLE AIRMASS THAT
RESIDES EAST OF THE OH VLY. THIS IMPULSE IS FORECAST TO REACH
CENTRAL PA BY MIDDAY AND EASTERN PA BETWEEN 18Z-00Z. THERE IS A
POTENTIAL FOR ISOLATED SHOWERS TO DEVELOP AHEAD OF THE SHORTWAVE
TROUGH DURING THE MID TO LATE AFTERNOON JUST OF OUR CWA.

NO CHANGE IN AREAL COVERAGE FROM THE 330AM/630AM FCST.

TONIGHT...HIGH PRESSURE WILL RETREAT OFF THE EASTERN SEABOARD
AS THE ABOVE MENTIONED SHORTWAVE TROUGH MOVES INTO THE AREA FROM
THE WEST. EXPECT SHOWERS AND PERHAPS A FEW THUNDERSTORMS WEST OF
THE APPALACHIAN RIDGE. FORECAST IS CONSERVATIVE IN REGARDS TO HOW
FAR EAST SHOWERS AND STORMS WERE MENTIONED AS MODELS GENERALLY
SHOW CONVECTION DECAYING AS IT MOVES EASTWARD INTO A MORE STABLE
AIRMASS OVER NJ/DE. CLOUDS COVER, WHICH WILL INCREASES ACROSS THE
ENTIRE AREA WITH THE APPROACH OF THE TROUGH, WILL LIMIT
RADIATIONAL COOLING TONIGHT. OFFICIAL MIN TEMP FORECAST SLIGHTLY
WARMER THAN MOS GUIDANCE.

&&

.SHORT TERM /THURSDAY/...
THURSDAY...THE AREA OF LOW PRESSURE AND ASSOCIATED FRONTAL BOUNDARY
TO OUR NORTHWEST WILL WEAKEN AS IT MOVES SE OUT OF THE GREAT LAKES
TO NEAR LAKE ONTARIO. HOWEVER, THE MID/UPPER- LEVEL LOW WILL SWING
THROUGH THE NORTHEAST AND MID- ATLANTIC THROUGH THURSDAY AND THURSDAY
NIGHT. THIS WILL ALLOW FOR SHOWERS, AND WITH A FAIR AMOUNT OF
INSTABILITY, SCATTERED THUNDERSTORMS TO DEVELOP AND MOVE INTO THE
AREA. THERE IS NOT MUCH SHEAR OR MUCH OF A WIND FIELD, SO WE DO
NOT EXPECT SEVERE WEATHER AT THIS TIME. PW VALUES ARE GENERALLY
FORECAST AROUND 1.5-1.75 INCHES, SO SOME SHOWERS/STORMS COULD
PRODUCE A PERIOD OF MODERATE TO HEAVY RAINFALL. ISOLATED SMALL
HAIL NOT IMPOSSIBLE AS TT NEAR 50 IN AREA OF MAX INSTABILITY IN
NJ (NEAR THE DELAWARE RIVER).

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
THE LONG TERM FORECAST STARTS OFF WITH RAIN CHANCES, BEFORE A DRYING
OUT PERIOD SETS IN ACROSS THE AREA.

THURSDAY NIGHT...A SECOND AREA OF SURFACE LOW PRESSURE IS FORECAST
TO DEVELOP NEAR THE CHESAPEAKE BAY ALONG THE STATIONARY BOUNDARY
TO OUR SOUTH. IT IS POSSIBLE THAT THIS MAY HELP KEEP A FOCUS FOR
PRECIPITATION THURSDAY NIGHT, BEFORE IT SAGS TO OUR SOUTH.

FOR FRIDAY INTO THE WEEKEND, THE MID/UPPER LOW WILL REMAIN TO OUR
NORTHEAST, KEEPING A NORTHWEST FLOW ALOFT ACROSS OUR AREA.
MEANWHILE, HIGH PRESSURE WILL BEGIN BUILDING DOWN ACROSS THE EAST
COAST FROM EASTERN CANADA. BEFORE THE HIGH TAKES FULL CONTROL OF THE
WEATHER, THERE WILL REMAIN A CHANCE OF SCATTERED SHOWERS FRIDAY AND
SATURDAY AS THERE MAY BE A FEW SHORT WAVE/VORT MAXES THAT AFFECT THE
AREA IN THE NORTHWEST FLOW ALOFT.

BY SUNDAY INTO EARLY NEXT WEEK, THE SURFACE HIGH BUILDS FURTHER INTO
THE MID-ATLANTIC REGION, WHICH SHOULD BRING DRY WEATHER TO THE AREA.

HIGHS ARE EXPECTED TO START OUT CLOSE TO OR SLIGHTLY ABOVE NORMAL
THURSDAY INTO FRIDAY, BUT AS THE HIGH BUILDS DOWN OUT OF EASTERN
CANADA AND THE NORTHWEST FLOW ALOFT REMAINS ACROSS THE AREA OVER THE
WEEKEND, 925/850 MB TEMPS AND THICKNESSES LOWER. THIS WILL ALLOW FOR
SLIGHTLY BELOW NORMAL TEMPERATURES OVER THE WEEKEND. AS WE MOVE INTO
EARLY NEXT WEEK, WE SHOULD START TO GET MORE OF A RETURN SURFACE
FLOW AND RIDGING ALOFT BEGINS TO TAKE PLACE ONCE AGAIN, ALLOWING
FOR REBOUNDING TEMPERATURES.

&&

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

TODAY...VFR SCT-BKN AOA 4000 FT. LIGHT SE TO S WIND.

TONIGHT...VFR CIGS LIKELY. LIGHT SOUTH WIND. PROB30 GROUP FOR SHRA
ADDED FOR RDG/ABE EARLY THIS EVE WHEN A DISTURBANCE MOVES THRU.

THURSDAY...GENERALLY VFR CIGS. LIGHT SOUTH WIND. SCATTERED SHOWERS
AND THUNDERSTORMS WHICH MAY LOWER CIGS/VSBYS TO BRIEFLY IFR CONDITIONS.

OUTLOOK...
THURSDAY NIGHT...GENERALLY VFR. CHANCE OF SHOWERS AND THUNDERSTORMS
WHICH MAY LOWER CIGS/VSBYS.

FRIDAY-SUNDAY...PERIODS OF LOW END VFR OR MVFR CIGS POSSIBLE WITH A
CHANCE OF SHOWERS, ESPECIALLY FRIDAY INTO SATURDAY.

&&

.MARINE...
NO MARINE RELATED HEADLINES THROUGH THURSDAY.

EASTERLY WINDS BETWEEN 5-10 KT WILL BECOME SOUTHEASTERLY THIS
AFTN AS HIPRES MOVES OFFSHORE. LOCALLY HIGHER WINDS TO 15 KT
POSSIBLE THIS AFTN AND EVE.

OUTLOOK...
THURSDAY-FRIDAY NIGHT...SUB-SMALL CRAFT ADVISORY CONDITIONS EXPECTED.

SATURDAY-SUNDAY...SEAS MAY BEGIN TO APPROACH SMALL CRAFT ADVISORY
LEVELS AS A LONG FETCH DEVELOPS AROUND HIGH PRESSURE BUILDING IN
FROM THE NORTHEAST OUT OF EASTERN CANADA.

&&

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

&&

$$
SYNOPSIS...DRAG/ROBERTSON
NEAR TERM...DRAG/KLEIN 943
SHORT TERM...DRAG/KLEIN 943
LONG TERM...ROBERTSON
AVIATION...DRAG/KLEIN/ROBERTSON 943
MARINE...DRAG/KLEIN/ROBERTSON 943






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