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000
FXUS61 KPHI 020742
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
342 AM EDT SAT AUG 2 2014

.SYNOPSIS...
LOW PRESSURE LOCATED ALONG THE VIRGINIA COAST EARLY THIS MORNING
WILL PROGRESS SLOWLY TO THE NORTHEAST ALONG A FRONTAL BOUNDARY.
THE LOW IS FORECAST TO REACH THE WATERS OFF THE EASTERN TIP OF
LONG ISLAND THIS EVENING BEFORE PASSING CAPE COD OVERNIGHT. THE
FRONT IS EXPECTED TO LINGER OVER THE COASTAL WATERS ON SUNDAY
BEFORE DRIFTING OUT TO SEA. WEAK HIGH PRESSURE IS ANTICIPATED TO
FOLLOW FOR MONDAY INTO TUESDAY. A COLD FRONT FROM THE NORTHWEST IS
FORECAST TO ARRIVE ON WEDNESDAY WITH HIGH PRESSURE BUILDING INTO
OUR REGION IN ITS WAKE FOR THURSDAY AND FRIDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A COOL, DAMP START TO THE DAY TODAY, WITH A POSSIBLE END TO THE
RAIN, OR AT LEAST LESS COVERAGE, BY MID- MORNING INTO THE
AFTERNOON. TROUGHING ALOFT REMAINS TO OUR WEST ACROSS THE GREAT
LAKES, THROUGH THE OHIO RIVER VALLEY, AND SOUTHWARD TOWARD THE
GULF COAST. MEANWHILE, A FRONTAL BOUNDARY REMAINS ACROSS THE
WESTERN ATLANTIC, SOUTHWESTWARD ACROSS THE SOUTHEAST COAST. AN
AREA OF LOW PRESSURE NEAR THE SOUTHERN CHESAPEAKE BAY WILL MOVE
NORTHWARD ALONG THE FRONTAL BOUNDARY THROUGH THIS MORNING. AT THE
SAME TIME, A SHORT WAVE/VORTICITY IMPULSE IS SLIDING TOWARD THE
AREA WITHIN THE SOUTHWEST FLOW ALOFT. THE INTERACTION BETWEEN THE
TWO HAS CREATED AN AREA OF LIGHT TO MODERATE RAINFALL WITH
EMBEDDED HEAVIER RAIN THAT IS MOVING THROUGH THE MID-ATLANTIC
REGION.

THIS AREA OF RAIN WILL CLEAR THE AREA BY MID-LATE MORNING AS THE
SHORT WAVE/VORTICITY IMPULSE SLIDES NORTH OF THE AREA. WE COULD
THEN ENTER INTO A RELATIVELY DRY PERIOD FOR THE REMAINDER OF THE
DAY FOR MANY AREAS, AND WE MAY EVEN EXPERIENCE SOME FILTERED
SUNSHINE IN SOME AREAS. HOWEVER, WITH THE AMOUNT OF MOISTURE
REMAINING ACROSS THE AREA, THE FACT THAT THE FRONT REMAINS NEAR
THE AREA, AND THE POSSIBILITY FOR ADDITIONAL WEAK SHORT
WAVE/VORTICITY IMPULSES, THERE WILL REMAIN A CHANCE FOR SCATTERED
SHOWERS AND THUNDERSTORMS THROUGH THE AFTERNOON. THERE IS NOT MUCH
SURFACE BASED INSTABILITY FORECAST, BUT THERE COULD BE SOME
ELEVATED INSTABILITY LATER IN THE DAY, SO WE WILL KEEP THE CHANCE
OF THUNDERSTORMS IN THE FORECAST.

THE TEMPERATURE FORECAST TODAY WILL BE TRICKY. IF WE STAY MORE
CLOUDY AS THE NAM SUGGESTS, IT WILL END UP BEING A COOL DAY.
HOWEVER, IF WE DO GET SOME INSOLATION DURING THE DAY AS THE GFS
AND ECMWF SUGGEST, THEN WE COULD WARM UP A LITTLE DURING THE DAY.
WITH THE UNCERTAINTY IN THE CLOUD COVER, WE TOOK A BLEND OF THE
AVAILABLE GUIDANCE; MAV/MET MOS, MOSGUIDE, AND ECMWF FOR DAYTIME
HIGHS WHICH LOOKS PRETTY REASONABLE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
ROUND 2, DING DING. NOT MUCH OF AN OVERALL CHANGE IN THE PATTERN
FROM THIS PAST NIGHT TO THE UPCOMING NIGHT. THE MID/UPPER TROUGH
TO OUR WEST BEGINS TO SLIDE EASTWARD, BUT OUR AREA REMAINS IN THE
SOUTHWEST FLOW ALOFT. THE FRONTAL BOUNDARY OFF THE EAST COAST DOES
NOT MAKE MUCH PROGRESS, AND ANOTHER WEAK SURFACE LOW MAY BEGIN
FORMING ALONG THE BOUNDARY AND LIFTING TOWARD OUR AREA OVERNIGHT.
MEANWHILE, ANOTHER SHORT WAVE/VORTICITY IMPULSE WILL MOVE ACROSS
THE AREA WITHIN THE SOUTHWEST FLOW ALOFT. THE INTERACTION BETWEEN
THE VORT MAX AND THE SURFACE FEATURES WILL ONCE AGAIN CREATE AN
AREA OF RAINFALL THAT WILL MOVE ACROSS THE MID-ATLANTIC REGION
OVERNIGHT. AGAIN, MUCH OF THE RAIN WILL BE LIGHT TO MODERATE, BUT
THERE WILL BE SOME AREAS OF HEAVY RAIN POSSIBLE.

FOR OVERNIGHT LOWS, WE TOOK A BLEND OF THE AVAILABLE GUIDANCE;
MAV/MET MOS, MOSGUIDE, AND ECMWF.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
A MID LEVEL SHORT WAVE IS FORECAST TO BE LOCATED OVER THE EASTERN
GREAT LAKES AND THE UPPER AND MIDDLE PARTS OF THE OHIO RIVER
VALLEY ON SUNDAY MORNING. THE FEATURE IS EXPECTED TO LIFT EAST
NORTHEASTWARD, PASSING OVER OUR REGION ON SUNDAY NIGHT. A MID
LEVEL TROUGH SHOULD REMAIN OVER THE NORTHEASTERN STATES DURING THE
NEW WEEK WITH ANOTHER SHORT WAVE POSSIBLY PASSING OVERHEAD AROUND
THURSDAY.

A FRONTAL BOUNDARY IS ANTICIPATED TO LINGER OVER OUR COASTAL
WATERS FOR SUNDAY INTO SUNDAY NIGHT BEFORE BEING SHUNTED OUT TO
SEA BY THE FIRST SHORT WAVE. WE WILL CONTINUE TO MENTION SHOWERS
FOR SUNDAY INTO SUNDAY EVENING WITH THE HIGHER CHANCES BEING NEAR
THE COAST. WE WILL KEEP THE MENTION A CHANCE OF THUNDER. HOWEVER,
THE THUNDER SHOULD BE QUITE LIMITED BEING THAT CONDITIONS ARE
EXPECTED TO BE ONLY MARGINALLY UNSTABLE.

WEAK HIGH PRESSURE SHOULD BRING A BIT OF DRYING TO OUR REGION
FROM THE WEST FOR MONDAY INTO TUESDAY. WEAK IMPULSES IN THE MID
LEVEL FLOW COULD TOUCH OFF A FEW SHOWERS AND THUNDERSTORMS ON BOTH
DAYS MAINLY DURING THE AFTERNOON HOURS.

A COLD FRONT FROM THE NORTHWEST IS FORECAST TO ARRIVE ON
WEDNESDAY. WE WILL MENTION A CHANCE OF SHOWERS AND THUNDERSTORMS
IN ASSOCIATION WITH THE BOUNDARY. SURFACE HIGH PRESSURE AND SOME
DRYING ARE EXPECTED TO FOLLOW FOR THE END OF THE WORK WEEK,
ESPECIALLY IN THE WAKE OF THE SECOND MID LEVEL SHORT WAVE.

THE MID LEVEL TROUGH SHOULD PREVENT TEMPERATURES FROM BECOMING
EXCESSIVELY WARM. DAYTIME HIGHS ARE EXPECTED TO BE MAINLY IN THE
80S DURING THE WORK WEEK WITH OVERNIGHT LOWS MOSTLY IN THE 50S AND
60S.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

CONDITIONS VARY FROM VFR TO MVFR EARLY THIS MORNING AS AN AREA OF
MOSTLY LIGHT TO MODERATE RAINFALL MOVES ACROSS THE AREA. ALL SITES
ARE EXPECTED TO LOWER TO MVFR AND POSSIBLY IFR THROUGH SUNRISE AS
THE RAIN CONTINUES TO MOVE THROUGH. HOWEVER, AS THE RAIN ENDS BY
THE MID-LATE MORNING HOURS, CONDITIONS ARE EXPECTED TO RETURN TO
VFR FOR THE REMAINDER OF THE DAY. AS ANOTHER ROUND OF
PRECIPITATION MOVES INTO THE AREA OVERNIGHT SATURDAY INTO SUNDAY
MORNING, CONDITIONS ARE EXPECTED TO LOWER ONCE AGAIN TO MVFR
AND/OR IFR.

WINDS ARE EXPECTED TO BE MOSTLY OUT OF AN EASTERLY DIRECTION, BUT
COULD VARY FROM NORTHEAST TO SOUTHEAST AT TIMES. WIND SPEEDS ARE
EXPECTED TO BE 10 KNOTS OR LESS, ALTHOUGH A FEW GUSTS AROUND 15
KNOTS ARE POSSIBLE THIS MORNING, ESPECIALLY NEAR THE COAST.

OUTLOOK...
SUNDAY...CONDITIONS VARYING BETWEEN MVFR AND VFR WITH SHOWERS AND
SCATTERED THUNDERSTORMS.

SUNDAY NIGHT THROUGH TUESDAY...MAINLY VFR. A LOW CHANCE OF
AFTERNOON SHOWERS AND THUNDERSTORMS BOTH DAYS.

TUESDAY NIGHT...MAINLY VFR WITH SOME MVFR CEILING AND VISIBILITY
RESTRICTIONS POSSIBLE LATE AT NIGHT.

WEDNESDAY...MAINLY VFR WITH A CHANCE OF SHOWERS AND
THUNDERSTORMS.

&&

.MARINE...
A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR THE NORTHERN TWO
MARINE ZONES, FROM LITTLE EGG NORTH. MODELS INDICATE WINDS
INCREASING ACROSS THE WATERS AS SURFACE LOW PRESSURE SLIDES
NORTHWARD ALONG THE FRONTAL BOUNDARY THAT IS LOCATED OFF THE COAST
LATER THIS MORNING INTO THIS AFTERNOON. IT LOOKS LIKE THE WINDS ON
THE SOUTHERN WATERS WILL REMAIN BELOW ADVISORY LEVELS, BUT WILL
STILL BE GUSTY AROUND 20 KNOTS.

ONCE THE LOW PASSES, THE WINDS SHOULD SUBSIDE BACK BELOW ADVISORY
LEVELS FOR THE EVENING AND OVERNIGHT HOURS.

OUTLOOK...
SUNDAY THROUGH WEDNESDAY...NO MARINE HEADLINES ARE ANTICIPATED.

&&

.RIP CURRENTS...
LONG PERIOD SWELLS FROM TROPICAL STORM BERTHA MAY AFFECT THE
COASTS OF DELAWARE AND NEW JERSEY FROM MONDAY INTO WEDNESDAY. THE
SWELLS ARE EXPECTED TO BRING AN ENHANCED THREAT FOR DANGEROUS RIP
CURRENTS AT THAT TIME.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ450-
     451.

&&

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