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Area Forecast Discussion
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000
FXUS61 KPHI 131334
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
934 AM EDT FRI MAR 13 2015

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFFSHORE TODAY. LOW PRESSURE IN THE SOUTHERN 
PLAINS WILL THEN TRACK NORTHEASTWARD INTO THE OHIO VALLEY SATURDAY, 
BEFORE MOVING OFFSHORE OF NEW ENGLAND ON SUNDAY. HIGH PRESSURE WILL 
BUILD BRIEFLY INTO OUR REGION MONDAY, THEN A COLD FRONT MOVES 
THROUGH LATE MONDAY NIGHT AND TUESDAY MORNING. A SECONDARY COLD 
FRONT MAY SETTLE ACROSS OUR AREA LATE WEDNESDAY, OTHERWISE HIGH 
PRESSURE WILL THEN GRADUALLY BUILD EASTWARD INTO OUR REGION 
WEDNESDAY AND THURSDAY.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
9:30 AM UPDATE: LOWERED DEWPOINTS A BIT ACROSS THE REGION AS A
DRY AIRMASS IS STILL IN PLACE AND WILL BE SLOWER TO DEPART. THIS
MAY HOLD OFF RAIN CHANCES A FEW HOURS THIS EVENING AND WILL UPDATE
THIS ASPECT OF THE FORECAST WITH THE 12;30 PM UPDATE. MINOR
ADJUSTMENTS MADE TO TEMPERATURES AND SKY COVER AS WELL.


MOSTLY CLEAR THROUGH NOON THEN INCREASING AND SLOWLY LOWERING
CIRRUS DURING THIS AFTERNOON. HIGHS AROUND 50 THIS AFTERNOON AND A
COUPLE DEGREES COOLER INLAND THAN THURSDAY AND CERTAINLY MUCH
COOLER ALONG THE COAST WHERE CHILLING SEABREEZES FROM THE RECENTLY
DEICED OCEAN WATERS DROPS AFTERNOON TEMPS INTO THE UPPER 30S AND
LOWER 40S. SSTS GENERALLY UPPER 30S TO AROUND 40. A LIGHT
NORTHEAST WIND EARLY TODAY HAS LIMITED PREDAWN RADIATIONAL COOLING
TO PRIMARILY NW NJ AND NE PA (N OF I-78). THIS WIND WILL BECOME
S-SE THIS AFTERNOON WITH POSSIBLE GUSTS 15 MPH.
 
CONFIDENCE: HIGH.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
WARM AIR ADVECTION RAIN DEVELOPS FROM SW TO NE BETWEEN 11 PM AND 5
AM. RAIN, POSSIBLY HEAVY AT TIMES NEAR AND AFTER 5 AM ACROSS THE
DELMARVA/SE PA AND FAR SW NJ AS A WLY 7H JET OF 55KT DEVELOPS BY
12Z SATURDAY ACROSS SOUTHERN PA WITH A WSW 50 KT JET NOSED INTO THE 
DELMARVA AND A SW 925MB JET OF 45-50 KT ALSO NOSED INTO THE 
DELMARVA. SO ITS A DECENT INSTABILITY BURST BUT NO THUNDER. A SMALL 
CHC OF ICING VCNTY HIGH POINT NJ AND KMPO AT THE ONSET IN THE 2A-5A 
TIME FRAME AND IN THE HWO ONLY. THE SFC WARM FRONT BY DAYBREAK 
SATURDAY SHOULD BE STRETCHED FROM NEAR KSBY TO NEAR KDCA TO NEAR 
KEKN (FAR S DE TO WASHINGTON DC AND NRN W.VA). NEAR 100 POP BY 10Z 
/13. SOME WARMER DEWPOINT CONTACT DEVELOPED DENSE FOG ON COLDER 
ELEVATED SFC'S NEAR DAYBREAK SATURDAY (1/4 MI POCONOS WITH 1-2 MI 
FOG POSSIBLE ELSEWHERE). LIGHT WIND. CONFIDENCE: HIGH

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
THE OVERALL SYNOPTIC SETUP IS COMPRISED OF AN AMPLIFYING UPPER-LEVEL 
TROUGH ACROSS THE GREAT LAKES AND NORTHEAST SATURDAY INTO SUNDAY. 
THIS FEATURE SHOULD LIFT OUT MONDAY AS THE NEXT TROUGH SLIDES ACROSS 
THE MIDWEST AND PORTIONS OF THE GREAT LAKES REGION. THIS SHOULD 
AMPLIFY SOME INTO THE NORTHEAST TUESDAY AS THE PATTERN TENDS TO 
TRANSITION INTO MORE OF A TROUGH ACROSS THE EAST INTO WEDNESDAY. 
DESPITE SURFACE HIGH PRESSURE BUILDING EAST, A SECONDARY COLD FRONT 
MAY SETTLE ACROSS OUR AREA LATE WEDNESDAY. THE MAIN FOCUS IS FOR THE 
POTENTIAL FOR A PERIOD OF HEAVY RAIN SATURDAY MORNING. WE USED A 
MODEL BLEND APPROACH FOR SATURDAY THROUGH MONDAY, THEN BLENDED IN 
THE 00Z WPC GUIDANCE THEREAFTER.

FOR SATURDAY...A NORTHERN STREAM SHORT WAVE AMPLIFIES AN UPPER-LEVEL 
TROUGH ACROSS THE GREAT LAKES DURING SATURDAY. THE COMBINATION OF 
THIS FEATURE AND ALSO A SHORT WAVE LIFTING INTO THE OHIO VALLEY WILL 
HELP PULL GULF OF MEXICO MOISTURE NORTHWARD. THIS MOISTURE SURGE 
LOOKS TO PEAK DURING SATURDAY MORNING, WHERE THE COMBINED LIFT CAN 
RESULT IN LOCALLY HEAVY RAIN. GIVEN THE MOISTURE TRANSPORT ALONG 
WITH WAA, THE THERMAL PROFILE IS ANTICIPATED TO NOT SUPPORT 
SNOW/SLEET AT THE ONSET UP NORTH. HOWEVER, POCKETS OF BRIEF FREEZING 
RAIN COULD OCCUR AT THE ONSET ACROSS THE POCONOS TO FAR NORTHWESTERN 
NEW JERSEY EARLY SATURDAY. THE CLOUD COVER, WAA AND A SOUTHERLY FLOW 
SHOULD HALT OR REVERSE THE EARLIER RADIATIONAL COOLING. THEREFORE, 
WE CONTINUED WITH TEMPERATURES GRADUALLY RISING AND A RAIN EVENT 
ACROSS THE CWA.

THE INFLUX OF MOISTURE SHOULD RESULT IN SOME FOG MAINLY THROUGH THE 
MORNING, ALTHOUGH THIS MAY BE MOST NOTABLE WHERE SNOW COVER REMAINS. 
A SURFACE LOW TRACKS TO OUR WEST SATURDAY BEFORE TURNING MORE EAST 
AT NIGHT, PULLING A COLD FRONT ACROSS OUR AREA. THIS WILL ALLOW THE 
INITIAL OVERRUNNING/WAA RAIN TO TAPER TO SHOWERS IN THE AFTERNOON AS 
THE WARM SECTOR MOVES NORTH DURING THE DAY /ESPECIALLY FROM THE 
PHILADELPHIA METRO AREA ON SOUTH AND EAST/. THE SHOWERS THEN END IN 
THE EVENING AS SOME DRYING WORKS IN. OVERALL, THE TOTAL QPF LOOKS TO 
BE UP TO AN INCH ACROSS THE CWA WITH NO WIDESPREAD IMPACTS 
ANTICIPATED. SEE THE HYDROLOGY SECTION BELOW.
 
FOR SUNDAY AND MONDAY...A CLOSED LOW WILL TRACK ACROSS NEW ENGLAND 
SUNDAY, THEN THIS SHIFTS EASTWARD SUNDAY NIGHT INTO MONDAY. WHILE 
THE DEEPER MOISTURE WILL BE TO OUR EAST, COLDER AIR ALOFT COMBINED 
WITH ENOUGH HEATING IN THE BOUNDARY LAYER SUNDAY SHOULD RESULT IN A 
FEW SHOWERS ACROSS THE NORTH. THIS LOOKS LIKE LESS OF A CHC NOW AS 
THE MAIN COLD POOL ALOFT TRACKS FARTHER TO OUR NORTH. WE MAINTAINED 
SOME SLIGHT CHC POPS ACROSS THE NORTHWEST ZONES FOR NOW. AS LOW 
PRESSURE DEPARTS NEW ENGLAND AND HIGH PRESSURE BUILDS ACROSS THE 
OHIO VALLEY SUNDAY, A TIGHT PRESSURE GRADIENT WILL RESULT ACROSS OUR 
AREA. AS SOME COOLING TAKES PLACE, WE SHOULD HAVE DECENT BOUNDARY 
LAYER MIXING FOR AWHILE AND THEREFORE BREEZY CONDITIONS SUNDAY. WE 
DID BOOST THE WINDS SOME FOR A TIME SUNDAY. THE MAIN UPPER-LEVEL 
TROUGH WEAKENS SOME MONDAY WITH SURFACE HIGH PRESSURE BUILDING IN. A 
NORTHWESTERLY FLOW ALOFT IS FORECAST AND THIS WILL BRING IN SOME 
COOLING, AND THE FASTER FLOW WILL DRIVE OUR NEXT COLD FRONT INTO OUR 
AREA MONDAY NIGHT. THIS APPEARS TO BE A QUICK MOVER WITH LIMITED 
MOISTURE, HOWEVER THERE COULD STILL BE A FEW SHOWERS WITH IT.
 
FOR TUESDAY, WEDNESDAY AND THURSDAY...A COLD FRONT SHOULD BE 
CLEARING OUR AREA TO START TUESDAY, THEN WE ARE LEFT WITH CYCLONIC 
FLOW. HIGH PRESSURE DROPPING SOUTHEASTWARD FROM CENTRAL CANADA IS 
FORECAST TO GRADUALLY BUILD EAST INTO OUR AREA WEDNESDAY AND 
THURSDAY, HOWEVER A SECONDARY COLD FRONT MAY MOVE THROUGH LATE 
WEDNESDAY. THE PRESENCE OF A MORE PRONOUNCED UPPER-LEVEL TROUGH IN 
THE EAST AND OUR FLOW COMING OUT OF THE NORTHWEST, SHOULD RESULT IN 
A COLDER REGIME DURING THIS TIME FRAME.

&&

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

THROUGH 12Z...VFR CLEAR OR SCT CLOUDS AOA 25000. LIGHT NE WIND.

AFTER 12Z...SCT CIRRUS AOA 25000 FT LOWERING AND THICKENING DURING 
THE AFTERNOON TO NEAR 15000 FT LATE IN THE DAY. LIGHT NE WIND BECOMING S-
SE WITH AFTERNOON GUSTS TO 15 KT. CONFIDENCE: HIGH 

TONIGHT: VFR CIGS TO START BECOMING IFR OR LIFR IN RAIN/STRATUS/FOG 
EARLY SATURDAY. LIGHT WIND. PLS SEE TAFS FOR TIMING DETAILS. 
SLIGHTEST CHC OF A FEW ICE PELLETS AT THE START VCNTY KRDG AND KABE 
AROUND 03Z-06Z TIME FRAME.

OUTLOOK... 
SATURDAY...MVFR/IFR IN PERIODS OF RAIN AND SOME FOG, THEN IMPROVING 
TO VFR AT NIGHT FROM WEST TO EAST. THE RAIN IS EXPECTED TO TAPER TO 
SHOWERS IN THE AFTERNOON AND END IN THE EARLY EVENING. SOUTH WINDS 
MAINLY 10 KNOTS OR LESS SHIFTING TO NORTHWEST AT NIGHT. 

SUNDAY...VFR CEILING AT TIMES. NORTHWEST WINDS 10-15 KNOTS WITH 
GUSTS TO 25 KNOTS.

MONDAY AND TUESDAY...VFR OVERALL. NORTHWEST TO SOUTHWEST WINDS LESS 
THAN 10 KNOTS MONDAY, BECOMING NORTHWEST MONDAY NIGHT AND TUESDAY 
10 TO 20 KNOTS.

&&

.MARINE...
NO HEADLINES THROUGH TONIGHT. SEAS AOB 4 FT. N WIND 10-15 
KT BECOMING SE THIS AFTERNOON AND NIGHT. CONFIDENCE: HIGH.  

OUTLOOK...
SATURDAY AND SUNDAY...A SOUTHERLY FLOW WILL INCREASE SATURDAY AND 
SATURDAY NIGHT THEN SHIFT TO THE NORTHWEST SUNDAY. IT APPEARS THAT 
THE WIND MAINLY STAYS BELOW ADVISORY CRITERIA. HOWEVER ON SUNDAY, 
SOME GUSTS TO 25 KNOTS MAY OCCUR NEARSHORE ALTHOUGH LESS MIXING MAY 
RESULT OVER THE WATERS AS THE BOUNDARY LAYER IS PROBABLY STILL MILD 
ENOUGH. THE STRENGTH OF THE SOUTHERLY FLOW ESPECIALLY WILL IMPACT 
HOW QUICKLY THE SEAS BUILD. AS OF NOW, KEPT IT MARGINAL AND 
THEREFORE HELD OFF ON A SMALL CRAFT ADVISORY.

MONDAY AND TUESDAY...A COLD FRONT MOVES THROUGH MONDAY NIGHT AND 
TUESDAY MORNING WITH A WIND SHIFT TO THE NORTHWEST. THE FLOW IS 
EXPECTED TO INCREASE WITH BETTER MIXING, THEREFORE GUSTS TO AROUND 
25 KNOTS ARE POSSIBLE FOR A TIME TUESDAY.

&&

.HYDROLOGY...
RAIN SATURDAY SHOULD BE THE STEADIEST AND HEAVIEST DURING THE 
MORNING HOURS. WHILE THE LOW LEVEL FLOW IS SOUTHWEST AND HELPING TO 
DRAW UP GULF OF MEXICO MOISTURE, THE FLOW VEERS TO WESTERLY FROM 
ABOUT 700 MB ON UP. THIS MAY RESULT IN SOME LOWER QPF ACROSS THE 
NORTHERN AND WESTERN AREAS, PLUS THE LOW-LEVEL JET APPEARS TO BE 
AIMED MORE TOWARD THE DELMARVA AND EASTERN NEW JERSEY. OVERALL, THE 
TOTAL RAINFALL AMOUNTS SHOULD BE UP TO AN INCH ACROSS THE CWA. WHILE 
THE 6-HOUR FFG HAS SOME SPOTS /BASICALLY ALONG EITHER SIDE OF 
INTERSTATE 95/ AROUND OR UNDER AN INCH, WIDESPREAD IMPACTS ARE NOT 
EXPECTED. WHILE WE MAY SEE SOME POOR DRAINAGE FLOODING DURING TIMES 
OF HEAVIER RAIN ALONG WITH A FEW SMALLER FAST RESPONDING STREAMS 
GETTING TO MINOR FLOOD, THE THREAT LOOKS LOCALIZED ENOUGH AND 
THEREFORE NO FLOOD WATCH WILL BE ISSUED ATTM /NOTE, NO FORECAST 
POINTS ARE EXPECTED TO GET TO OR ABOVE FLOOD STAGE ATTM/.

&&

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

&&

$$
SYNOPSIS...GORSE
NEAR TERM...GAINES
SHORT TERM...DRAG
LONG TERM...GORSE
AVIATION...DRAG/GORSE
MARINE...DRAG/GORSE
HYDROLOGY...



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