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Area Forecast Discussion
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000
FXUS61 KPHI 130133
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
933 PM EDT THU MAR 12 2015

.SYNOPSIS...
HIGH PRESSURE CURRENTLY OVER OUR REGION WILL MOVE OFFSHORE 
ON FRIDAY. LOW PRESSURE IN THE SOUTHERN PLAINS WILL MOVE 
NORTHEASTWARD INTO THE OHIO VALLEY ON SATURDAY THEN INTO NEW ENGLAND 
ON SUNDAY. HIGH PRESSURE WILL BUILD EASTWARD INTO THE REGION BEHIND 
THIS LOW PRESSURE SYSTEM ON MONDAY. BY TUESDAY, A COLD FRONTAL 
BOUNDARY WILL MOVE THROUGH THE REGION. ANOTHER HIGH PRESSURE SYSTEM 
WILL THEN BUILD EASTWARD INTO THE REGION BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
930 PM UPDATE...NO MAJOR CHANGES IN THE NEAR TERM. PREVIOUS HIGHER
DEW POINT ANOMALY IN THE LEHIGH VALLEY HAS DISSIPATED, SO EVERYONE
NORTH OF DELMARVA HAS SINGLE DIGIT DEWPOINTS. DEWPOINTS SHOULD
GRADUALLY INCREASE THOUGH AS WINDS SHIFT TO AN EASTERLY, THEN
SOUTHEASTERLY DIRECTION.

630 PM UPDATE...ADJUSTED DEW POINT TEMPERATURES TO REFLECT CURRENT
OBS. INTERESTINGLY MOST LOCATIONS OUTSIDE OF DELMARVA HAVE DEW
POINT TEMPERATURES IN THE SINGLE DIGITS EXCEPT KABE AND KRDG WHERE
DEW POINTS ARE 13 AND 11, RESPECTIVELY, AS OF 6 PM EDT. THIS AREA
OF HIGHER DEW POINTS SEEMS TO MIRROR THE NARROW CORRIDOR THAT
STILL HAS SOME SNOW PACK, AND APPEARS TO BE THE RESULT OF SNOW
MELT IN THIS AREA. 

PREVIOUS NEAR TERM DISCUSSION...GUSTY WINDS WILL REMAIN FOR A
COUPLE OF MORE HOURS, THEN AS HIGH PRESSURE BUILDS ACROSS THE AREA
TONIGHT, WINDS WILL LIGHTEN AND BECOME LIGHT AND VARIABLE IN MOST
AREAS. SKIES WILL REMAIN MOSTLY CLEAR FOR MOST OF THE NIGHT, WITH
ONLY SOME HIGH LEVEL CLOUDS POSSIBLE. WITH MOSTLY CLEAR SKIES AND
LIGHTENING WINDS, IT LOOKS TO BE A GOOD RADIATIONAL COOLING NIGHT
IS EXPECTED AND TEMPERATURES SHOULD FALL BELOW NORMAL.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH 6 PM FRIDAY/...
HIGH PRESSURE BUILDS OFFSHORE DURING THE DAY FRIDAY, ALLOWING FOR 
RETURN FLOW TO DEVELOP ACROSS THE AREA. EVEN WITH THE RETURN FLOW, 
TEMPERATURES DO NOT LOOK TO REBOUND SIGNIFICANTLY, THOUGH MOISTURE 
WILL BEGIN TO INCREASE LATER IN THE DAY. THERE WILL BE AN INCREASE 
IN CLOUDS LATER IN THE AFTERNOON, BUT NO PRECIPITATION IS EXPECTED 
THROUGH THE DAYLIGHT HOURS. WINDS SHOULD BE LIGHTER THAN MONDAY, BUT 
MAY GUST AROUND 15-20 MPH DURING THE AFTERNOON.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
FRIDAY NIGHT THROUGH SUNDAY: CLOUDS WILL BE ON THE INCREASE WITH 
MOISTURE OVERRUNNING A WARM FRONTAL BOUNDARY AHEAD OF A LOW
PRESSURE SYSTEM IN THE SOUTHERN PLAINS FRIDAY NIGHT. THIS LOW
PRESSURE SYSTEM WILL TRACK NORTHEASTWARD ON SATURDAY INTO THE OHIO
VALLEY. THE MOISTURE LIFTING OVER THE WARM FRONT WILL RESULT IN A
LARGE AREA OF OVERRUNNING RAIN DEVELOPING TO OUR SOUTH AND
EXPANDING THROUGH THE REGION FRIDAY NIGHT WITH GRADUALLY
INCREASING POPS TO CATEGORICAL. LOWS LIKELY WILL OCCUR IN THE
EVENING THEN RISE BY MORNING WITH THE WARMER AIRMASS ADVECTING IN,
SOUTHERLY WINDS. TEMPERATURES IN THE POCONOS MAY BE CLOSE TO
FREEZING SATURDAY MORNING BUT LOOK JUST ABOVE THE THRESHOLD FOR
FREEZING RAIN ATTM. SOME ADVECTION FOG MAY OCCUR OVER SNOWPACK AS
WELL WITH INCREASING DEWPOINTS.

BY SATURDAY TEMPERATURES WILL WARM WELL ABOVE THE FREEZING MARK 
REGIONWIDE WITH HIGHS IN THE 50'S IN SPOTS AS THE WARM FRONT PUSHES 
INTO THE REGION. WITH THE WARM FRONT IN THE REGION, PERIODS OF RAIN 
WILL CONTINUE THROUGHOUT THE DAY. FAIRLY GOOD MODEL AGREEMENT
BETWEEN THE SREF, GEFS AND OPERATIONAL MODELS OF QPF BETWEEN 3/4
AND 1 1/4 INCHES BY SATURDAY NIGHT. HOWEVER, RECENT HEAVY RAINFALL
EVENTS AND SNOW MELT MAY LEAD TO SOME LOCALIZED HYDRO CONCERNS, NO
FLOOD WATCH ISSUANCE ATTM.

THE LOW PRESSURE SYSTEM WILL DEPART ON SATURDAY NIGHT. HOWEVER, 
MOISTURE LOOKS TO BE SLOW TO CLEAR OUT. THE LINGERING MOISTURE
WITH LIGHTER WINDS MAY BE ENOUGH TO PROMOTE FOG AND DRIZZLE. SOME
OF THE GEFS MEMBERS LINGER MOISTURE EVEN LONGER INTO SUNDAY. THE
CURRENT FORECAST WILL GO WITH THE MORE OPTIMISTIC OUTCOME SHOWED
IN THE OPERATIONAL MODELS OF CLEARING CONDITIONS FOR SUNDAY.
 


SUNDAY NIGHT THROUGH THURSDAY: 

MOST OF THIS PERIOD LOOKS RATHER QUIET WITH TEMPERATURE CHANGES 
BETWEEN QUICK HITTING WINTER AND SPRING LIKE AIRMASSES. 925 MB 
TEMPERATURES ALONG WITH RENEWED SOUTHERLY FLOW SUGGEST MONDAY
COULD RUN WARMER THAN GUIDANCE INTO THE 50'S FOR MANY OF US WITH
SUNSHINE. ON THE OTHER HAND, A COLD FRONT IS PROGGED TO PASS
THROUGH THE REGION ON TUESDAY WITH NORTHWEST FLOW CLOUDS AND
POSSIBLY A FEW RAIN SHOWERS, MIGHT BE COLD ENOUGH FOR LIGHT SNOW
SHOWERS IN THE HIGHEST ELEVATIONS. WILL JUST CARRY SLIGHT CHANCE
POP. QUICK TURNAROUND TO ANOTHER WARMER, DRY AIRMASS BY WEDNESDAY
AND THURSDAY WITH REBOUNDING 925 MB TEMPERATURES THAT SUGGESTING
MODELED TWO METER TEMPERATURES AND ENSEMBLE GUIDANCE MAY BE TO
COOL.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, 
KMIV, KACY, AND SURROUNDING AREAS.

VFR CONDITIONS WILL PERSIST THROUGH THE DAY TIME HOURS FRIDAY.
ONLY AN INCREASE IN HIGH LEVEL CLOUDS EXPECTED OVERNIGHT INTO
EARLY FRIDAY. CLOUDS WILL BEGIN TO LOWER AND THICKEN AFTER 18Z.

NORTHWEST WINDS SHOULD CONTINUE TO DIMINISH OVER THE NEXT FEW
HOURS AS DAYTIME MIXING WANES. ALSO EXPECT A GRADUAL SHIFT TO
NORTHEASTERLY WINDS THROUGH THE EVENING HOURS THEN EASTERLY INTO
FRIDAY MORNING. A FEW TAF SITES MAY GO LIGHT AND VRB BETWEEN 06
AND 12Z. WINDS WILL INCREASE OUT OF THE SOUTHEAST DURING THE DAY
FRIDAY, WITH SOME GUSTS AROUND 15 KNOTS POSSIBLE DURING THE
AFTERNOON.

OUTLOOK... 
FRIDAY NIGHT: CEILINGS LOWERING TOP MVFR/IFR WITH RAIN DEVELOPING
IN THE EVENING. PATCHY FOG. SOUTHEAST WINDS UNDER 10 KNOTS.

SATURDAY AND SATURDAY NIGHT: MVFR/IFR IN PERIODS OF RAIN AND PATCHY 
FOG. SOUTH WINDS 10 KNOTS OR LESS SHIFTING TO NORTHWEST BY SUNDAY. 

SUNDAY: GRADUAL CLEARING WITH CEILINGS IMPROVING TO VFR.
NORTHWEST WINDS 10-15 KNOTS WITH GUSTS UP TO 25 KNOTS.

SUNDAY NIGHT THROUGH TUESDAY: VFR, WIND SHIFT FROM SOUTHWEST TO 
NORTHWEST ON TUESDAY. NORTHWEST WIND GUSTS TO 15 KNOTS TUESDAY 
AFTERNOON.

&&

.MARINE...

WINDS AND SEAS SHOULD REMAIN BELOW ADVISORY LEVELS THROUGH FRIDAY
AS HIGH PRESSURE BUILDS OVER THE AREA TONIGHT AND OFFSHORE FRIDAY.
WINDS WILL BE SHIFTING FROM NORTH NORTHWESTERLY TO SOUTHERLY
OVERNIGHT INTO TOMORROW, BUT WIND GUSTS SHOULD REMAIN NEAR OR
BELOW 20 KT.

OUTLOOK...
FRIDAY NIGHT THROUGH SUNDAY: SEAS WILL INCREASE FRIDAY NIGHT AND 
SATURDAY WITH SCA SEAS FROM 18Z SATURDAY TO 12Z SUNDAY. SOUTHERLY 
WINDS UNDER 20 KNOTS, HIGHEST SATURDAY AFTERNOON. WIND SHIFT TO 
NORTHWEST ON SUNDAY WITH GUSTS AROUND 25 KNOTS SUNDAY AFTERNOON.  
SEAS SHOULD DECREASE ON SUNDAY. PATCHY FOG POSSIBLE.

SUNDAY NIGHT THROUGH MONDAY NIGHT: SEAS AND WINDS BELOW SCA 
CRITERIA. 

TUESDAY: INCREASING NORTHWESTERLY WIND GUSTS TO AROUND 25 KNOTS IN 
THE AFTERNOON.

&&

.HYDROLOGY...
ANOTHER ROUND OF RAINFALL IS EXPECTED FRIDAY NIGHT AND SATURDAY
WITH AROUND AN INCH OF RAIN. CURRENT SIX HOUR FFG HAS SCATTERED
LOCATIONS BASICALLY ALONG EITHER SIDE OF INTERSTATE 95 AROUND OR
UNDER AN INCH. CURRENT MODELING FROM THE MARFC HAS SEVERAL POINTS
STAYING CLOSE OR UNDER CAUTION STAGE INTO SATURDAY. THESE POINTS
MAY SEE LEVELS RISE BACK INTO CAUTION STAGE SATURDAY NIGHT AND
SUNDAY. MODELED QPF AND POTENTIAL SNOW MELT ARE FACTORED INTO
THIS FORECAST TODAY WHICH INCREASES CONFIDENCE. A FLOOD WATCH WAS
NOT ISSUED WITH THIS FORECAST PACKAGE GIVEN THAT NO POINTS ARE
EXPECTED TO GET INTO FLOOD STAGE ATTM.

&&

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

&&

$$
SYNOPSIS...GAINES
NEAR TERM...JOHNSON/ROBERTSON
SHORT TERM...ROBERTSON
LONG TERM...GAINES
AVIATION...GAINES/JOHNSON/ROBERTSON
MARINE...GAINES/JOHNSON/ROBERTSON
HYDROLOGY...



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