Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 210517
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
117 AM EDT TUE OCT 21 2014

.SYNOPSIS...
LOW PRESSURE WILL PASS OFF THE MID ATLANTIC COAST ON TUESDAY
NIGHT. THE LOW IS THEN EXPECTED TO MOVE SLOWLY NORTH AND
NORTHEASTWARD, REACHING THE WATERS OFF CAPE COD AROUND THURSDAY
NIGHT AND ARRIVING IN NOVA SCOTIA ON FRIDAY NIGHT. HIGH PRESSURE
IS ANTICIPATED TO BUILD INTO OUR REGION FROM THE SOUTHWEST FOR
FRIDAY INTO SATURDAY. A COLD FRONT IS EXPECTED TO ARRIVE SATURDAY
NIGHT WITH ANOTHER AREA OF HIGH PRESSURE FOLLOWING FOR SUNDAY AND
MONDAY.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
AN UPPER-LEVEL TROUGH WILL CONTINUE TO AMPLIFY INTO THE NORTHEAST
OVERNIGHT. THE WATER VAPOR IMAGERY SHOWS A WELL DEFINED AND COMPACT
SHORT WAVE MOVING ACROSS SOUTHWESTERN PENNSYLVANIA. THIS FEATURE
WILL CONTINUE TO GRADUALLY SHIFT EASTWARD. OUT AHEAD OF IT, SOME
WAA AND THETA-E ADVECTION IS COMBINING WITH SOME SHORT WAVE ENERGY
WELL OUT AHEAD OF THE MAIN FEATURE. THIS ALONG WITH JUST ENOUGH
LOWER LEVEL CONVERGENCE IS RESULTING IN SOME SHOWERS ACROSS THE
WESTERN ZONES AND DOWN INTO VIRGINIA. THIS ACTIVITY IS GRADUALLY
SHIFTING EASTWARD, HOWEVER INTO AN INITIALLY DRIER AIRMASS. SOME
BRIEF HEAVIER SHOWERS THOUGH WILL SLIDE ACROSS THE FAR WESTERN
ZONES THROUGH ABOUT 08Z. OVERALL, THE QPF IS EXPECTED TO BE LIGHT.
WE CONTINUE SLIGHT CHC TO LOW CHC POPS FOR SOME SHOWERS MAINLY
ACROSS THE WESTERN HALF OF THE CWA.

THE HOURLY GRIDS WERE ADJUSTED BASED ON THE LATEST OBSERVATIONS,
AND THEN THE LAMP/LAV GUIDANCE WAS BLENDED IN FOR THE TEMPERATURES
AND DEW POINTS THROUGH EARLY THIS MORNING.

&&

.SHORT TERM /TUESDAY/...
A FILLING SURFACE LOW PRESSURE SYSTEM TO OUR NORTHWEST SLIDES
FURTHER SOUTH LATE TOMORROW MORNING AND BECOMES MORE BROAD. THERE
WILL LIKELY BE A DRY SLOT SETTING UP ACROSS THE CENTRAL PORTION OF
OUR CWA, THOUGH THE EXACT PLACEMENT IS STILL SUSPECT. A BETTER
DEFINED AND STRONGER COASTAL LOW FORMS OFF THE DELMARVA LATE IN
THE DAY AND MOVES TOWARDS THE NORTHEAST...LOTS OF JET DYNAMICS
INVOLVED. CHANCES FOR SHOWERS INCREASES TO LIKELY DURING THE DAY
MAINLY ACROSS OUR WESTERN AND NORTHERN ZONES, THOUGH STILL NOT
ENTIRELY SOLD ON A COMPLETELY DRY DAY ELSEWHERE SO WE CONTINUE THE
CHANCE POPS. NOT LOOKING AT A COMPLETE WASHOUT TOMORROW WITH
WIDELY SCATTERED SHOWERS THE MOST PROBABLE. WE KEEP THUNDER OUT OF
THE FORECAST, EVEN WITH STEEPER MID-LEVEL LAPSE RATES FORMING, AS
THE BETTER DYNAMICS OFFSHORE COULD ROB INLAND AREAS OF ALL THE
LUSTER. TEMPERATURES WILL CONTINUE TO CLIMB WITH THE MODIFYING
AIR MASS AND SOUTHERLY AHEAD OF THE LOW PRESSURE SYSTEM.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
A UPPER LEVEL JET EXTENDED FROM WESTERN HUDSON BAY, ACROSS
WESTERN ONTARIO TO THE WESTERN PART OF THE GREAT LAKES REGION THIS
AFTERNOON. A MID LEVEL LOW IS FORECAST TO DEVELOP IN THE LIFT
UNDER ITS LEFT FRONT QUADRANT TONIGHT OVER THE LAKE HURON
VICINITY. THE MID LEVEL LOW IS EXPECTED TO BE LOCATED OVER EASTERN
WEST VIRGINIA ON TUESDAY EVENING AND IT SHOULD PASS OFF THE
DELMARVA COAST ON WEDNESDAY MORNING. THE FEATURE IS THEN
ANTICIPATED TO MEANDER OFF OUR COAST FROM WEDNESDAY AFTERNOON INTO
THURSDAY EVENING BEFORE LIFTING NORTHEASTWARD AND REACHING THE
WATERS OFF CAPE COD ON FRIDAY MORNING. A SURFACE LOW IS FORECAST
TO FOLLOW THE MID LEVEL LOW CLOSELY DURING THE PERIOD.

WE ARE EXPECTING THE POTENTIAL FOR RAIN FROM TUESDAY NIGHT
THROUGH THURSDAY MORNING. THE POSSIBILITY OF MODERATE TO HEAVY
RAINFALL SHOULD BE MOSTLY ON THE EAST SIDE OF THE DEVELOPING MID
LEVEL LOW. AS A RESULT, WE ARE NOT ANTICIPATING MUCH MODERATE TO
HEAVY RAINFALL IN OUR REGION. THE ONLY EXCEPTION IS IN OUR COASTAL
AREAS FROM TUESDAY NIGHT INTO WEDNESDAY WHERE RAINFALL AMOUNTS MAY
APPROACH AN INCH AT SOME LOCATIONS. ALSO, MARGINAL INSTABILITY IN
THAT AREA MAY TRANSLATE INTO ISOLATED LIGHTNING AND THUNDER.
REGARDLESS, THE EXPECTED RAINFALL TOTALS SHOULD NOT RESULT IN ANY
FLOODING PROBLEMS.

AS THE LOW BEGINS TO PULL AWAY TO OUR NORTHEAST ON THURSDAY
NIGHT, THE POTENTIAL FOR RAIN SHOWERS SHOULD END GRADUALLY IN OUR
AREA.

A COUPLE OF REINFORCING MID LEVEL SHORT WAVES SHOULD DROP OVER
OUR REGION FROM THE NORTHWEST IN THE CYCLONIC FLOW AROUND THE
DEPARTING MID LEVEL LOW OVER THE COMING WEEKEND. THE SHORT WAVES
ARE NOT EXPECTED TO HAVE MUCH MOISTURE ASSOCIATED WITH THEM.
THEREFORE, WE ARE NOT ANTICIPATING ANY PRECIPITATION AT THAT TIME.

A MID LEVEL RIDGE FROM THE WEST SHOULD BUILD TOWARD OUR REGION
FOR SUNDAY AND MONDAY.

DAYTIME HIGHS ARE FORECAST TO BE A BIT BELOW NORMAL WITH THE RAIN
ON WEDNESDAY AND THURSDAY. READINGS SHOULD RETURN TO NEAR NORMAL
FOR THE PERIOD FROM FRIDAY THROUGH MONDAY.

&&

.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

OVERNIGHT...VFR OVERALL. LIGHT SOUTHERLY WINDS. SOME SHOWERS WILL
GENERALLY BE NORTH AND WEST OF KPHL, WITH A BRIEF HEAVIER SHOWER
AT KRDG AND KABE THROUGH ABOUT 08Z. WHILE SOME MVFR FOG CANNOT BE
RULED OUT, MAINLY AT KRDG AND KABE, CONFIDENCE IS ON THE LOW SIDE
GIVEN THE CLOUD COVER AND SHOWERS AND THEREFORE IT WAS NOT
INCLUDED AT THIS TIME.

TUESDAY...MOSTLY VFR. WEAK LOW PRESSURE SYSTEM NEARS FROM THE
WEST-NORTHWEST. WINDS START OFF LIGHT OUT OF THE SOUTH, MAYBE
SOUTHEAST, AND VEER TOWARDS THE WEST-NORTHWEST. SOME SHOWERS ARE
EXPECTED TO BE AROUND, HOWEVER THERE IS SOME LOWER CONFIDENCE ON
THE COVERAGE AND ACTUAL TIMING.

OUTLOOK...
TUESDAY NIGHT THROUGH THURSDAY...CONDITIONS VARYING BETWEEN VFR
AND MVFR IN PERIODS OF RAIN.

THURSDAY NIGHT...MAINLY VFR WITH A CHANCE OF SHOWERS.

FRIDAY THROUGH SATURDAY...MAINLY VFR.

&&

.MARINE...
OVERNIGHT...SUB-SCA CONDITIONS EXPECTED OVERALL. SOUTHERLY WINDS
IN THE 10-20 KNOT RANGE OVERALL, WITH THE GREATEST MIXING OUT
TOWARDS 20NM. THIS IS WHERE SEAS INCREASED TO 5 FEET EARLIER,
HOWEVER THESE HAVE SUBSIDED A LITTLE. SINCE THIS APPEARS TO BE
TOWARD THE OUTER EDGE OF THE COASTAL WATERS, NO SMALL CRAFT
ADVISORY ATTM. SEAS REMAIN MAINLY AT 4 FEET OR LESS.

TUESDAY...SUB-SCA CONDITIONS. WINDS BACK TOWARDS THE SOUTH-
SOUTHWEST TOMORROW AFTERNOON AND BEGIN TO DECREASE AS WEAK LOW
PRESSURE MOVES IN OVERHEAD. SEAS REMAIN 2 TO 3 FEET.

OUTLOOK...
TUESDAY NIGHT...NO MARINE HEADLINES ARE ANTICIPATED.

WEDNESDAY...NORTHERLY WIND GUSTS OF 25 TO 30 KNOTS ARE POSSIBLE.

WEDNESDAY NIGHT THROUGH FRIDAY NIGHT...NORTHWESTERLY WIND GUSTS
OF 25 TO 30 KNOTS ARE POSSIBLE.

SATURDAY...NO MARINE HEADLINES ARE ANTICIPATED.

&&

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

&&

$$
SYNOPSIS...IOVINO
NEAR TERM...GORSE
SHORT TERM...HEAVENER
LONG TERM...IOVINO
AVIATION...GORSE/IOVINO/HEAVENER
MARINE...GORSE/IOVINO/HEAVENER




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