Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 052238
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
638 PM EDT TUE MAY 5 2015

.SYNOPSIS...
A COLD FRONT WILL SLOWLY MOVE THROUGH OUR REGION TONIGHT AND
WEDNESDAY. HIGH PRESSURE WILL THEN MOVE INTO THE AREA FROM THE
NORTH AND EAST ON THURSDAY THROUGH THE WEEKEND. ANOTHER SLOW
MOVING COLD FRONT WILL APPROACH OUR AREA EARLY NEXT WEEK...AND
MOVE THROUGH THE REGION BY MID WEEK.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
CONDITIONS REMAINED MARGINALLY UNSTABLE OVER DELAWARE AND
NORTHEASTERN MARYLAND AROUND 630 PM. HOWEVER, THE TREND THROUGHOUT
OUR FORECAST AREA WILL BE TOWARD STABILIZATION EARLY THIS EVENING
WITH THE LOSS OF DAYTIME HEATING. AS A RESULT, WE HAVE REMOVED THE
MENTION OF THUNDER FROM THE FORECAST. THE ISOLATED LIGHTNING OVER
NORTHERN VIRGINIA AND CENTRAL MARYLAND EARLY THIS EVENING SHOULD
REMAIN TO THE WEST OF CHESAPEAKE BAY.

ALSO, BASED ON RADAR TRENDS WE HAVE LOWERED THE PROBABILITY OF
PRECIPITATION FOR THIS EVENING AND OVERNIGHT. THE MODELS HAVE BEEN
OVERLY ENTHUSIASTIC WITH THE COVERAGE AND INTENSITY OF THE
PRECIPITATION. IT LOOKS AS THOUGH THERE WILL BE ISOLATED TO
SCATTERED SHOWERS UNTIL AROUND MIDNIGHT IN RESPONSE TO WEAK
IMPULSES TRAVELING IN THE WEST NORTHWESTERLY MID LEVEL FLOW ALONG
WITH THE SURFACE FRONTAL BOUNDARY SINKING SOUTHWARD THROUGH OUR
REGION.

THE SURFACE FRONT WAS RATHER DIFFUSE AND DIFFICULT TO FIND EARLY
THIS EVENING. IT APPEARED TO EXTEND WESTWARD FROM SOUTHERN NEW
ENGLAND INTO NORTHERN PENNSYLVANIA AROUND 630 PM.

THE WIND IS FORECAST TO REMAIN LIGHT FOR TONIGHT. IT WILL FAVOR
THE WEST THIS EVENING AND IT SHOULD VEER TOWARD THE NORTH AND
NORTHEAST LATE TONIGHT. LOW TEMPERATURES ARE EXPECTED TO RANGE
FROM AROUND 50 IN THE NORTH TO NEAR 60 IN THE SOUTH.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH 6 PM WEDNESDAY/...
THE FRONT IS EXPECTED TO HAVE PASSED TO OUR SOUTH ON WEDNESDAY
MORNING, BUT MAY HANG AROUND THE VERY FAR SOUTHERN DELMARVA UNTIL
MID-LATE MORNING. THERE ARE A COUPLE OF MORE VORTICITY IMPULSES
THAT ARE FORECAST TO SLIDE ACROSS THE AREA WEDNESDAY. THERE WILL
REMAIN DECENT MOISTURE AROUND BEHIND THE FRONT, WITH PW VALUES
NEAR 1.0-1.25 INCHES, SO WE WILL KEEP ISOLATED/SCATTERED SHOWERS
IN THE FORECAST THROUGH THE DAY WEDNESDAY.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH TUESDAY/...
OVERVIEW...
MID-LEVEL RIDGE SLOWLY MOVES OVER THE NORTHEAST CONUS THU THRU
SAT...WITH WEAK S/WV DISTURBANCES TRAVERSING IT. MEANWHILE...A
CUT-OFF LOW DEVELOPS INVOF THE SOUTHEAST US COAST...AND THIS MAY
ACQUIRE SUBTROPICAL CHARACTERISTICS DURING THIS TIME FRAME.
OVERALL...THERE WILL BE A GENERAL BLOCKING PATTERN ALONG THE EAST
COAST WHICH MAY BECOME REX-LIKE ATTMS. THIS WILL LEAD TO A RIDGE
OF HIGH PRES AT THE SURFACE THROUGH THE WEEKEND...AND GRADUALLY
GIVE WAY TO A COOL FRONT APPROACHING FROM THE NW BY EARLY NEXT
WEEK. GENERALLY FAIR WX EXPECTED THRU THE WEEKEND... WITH AN
INCREASING CHANCE OF SHRA/TSRA WITH THE APPROACH OF COOL FRONT SUN
THROUGH EARLY NEXT WEEK. MAX TEMPERATURES WILL BE NEAR AVERAGE
THRU THE PERIOD...COOLER NEAR THE COAST THU THROUGH SAT WITH
ONSHORE FLOW. BY SUNDAY...THE AIR MASS MAY TURN INCREASINGLY
HUMID.

DAILIES...

WEDNESDAY NIGHT...A WEAK S/WV WILL MOVE THROUGH THE REGION WITH
FAVORABLE JET DYNAMICS. THIS WILL LEAD TO SOME OVERRUNNING ALONG A
SLOW MOVING FRONTAL BOUNDARY JUST TO OUR SOUTH. WEAK LIFT AND
LIMITED MOISTURE MAY SUPPORT SOME -SHRA OVER THE SOUTHWEST CWA.

THURSDAY AND FRIDAY...BOTH DAYS WILL FEATURE A WEAK S/WV MOVING
THRU THE REGION DURING THE AFTERNOON TIME FRAME. THIS INDUCES A
WEAK SFC TROF...WITH A SEA-BREEZE ALONG THE COAST...WHICH WILL
ENHANCE SFC CONVERGENCE. THERE WILL BE MORE MOISTURE AVAILABLE ON
THURSDAY...SO -SHRA ARE POSSIBLE...MAINLY NORTHWEST OF THE I-95
CORRIDOR. STABILITY INDICES DO NOT SUPPORT THUNDER ATTM.
ALSO...THERE MAY BE SOME PATCHY FOG FRI AM...MAINLY OVER THE
NORTHWEST INTERIOR...PER SYNOPTIC PATTERN AND MODEL SOUNDINGS.

SATURDAY AND SUNDAY...RIDGE BUILDS SURFACE AND ALOFT ON SAT...
AND GRADUALLY MOVES SOUTHEAST ON SUNDAY. SFC FLOW GRADUALLY VEERS
FROM THE SOUTHEAST ON SATURDAY TO SOUTHWEST ON SUNDAY. A COOL
FRONT WILL APPROACH THE SAINT LAWRENCE VALLEY BY 00Z SUNDAY...WITH
THE GFS MUCH MORE PROGRESSIVE THAN THE EURO THEREAFTER WITH THE
SOUTHWARD PROGRESSION OF THE FRONT. GIVEN THE BLOCKING PATTERN
ALONG THE EAST COAST...AND THE RIDGE ANCHORED OVER THE MID-
ATLANTIC...FAVOR THE SLOWER SOLUTION. FEEL GENERAL SUBSIDENCE WILL
KEEP THE COLUMN DRY/CAPPED ACROSS THE CWA...BUT CANNOT RULE OUT
-SHRA/TSRA MAKING IT INTO THE NW PORTION OF THE CWA ON SUN AFTN.

MONDAY AND TUESDAY...AS THE COOL FRONT APPROACHES...THERE WILL BE
GREATER MOISTURE, LIFT, AND INSTABILITY AVAILABLE. GIVEN A SLOW
FRONTAL PASSAGE WITH AMPLE GULF/SUBTROPICAL MOISTURE, AND
FAVORABLE JET DYNAMICS...HEAVY RAINFALL IS POSSIBLE DURING THIS
TIME FRAME.

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

WE CONTINUE A VFR FORECAST THROUGH THE TAF PERIOD. THERE REMAINS
THE CHANCE FOR SCATTERED SHOWERS THIS EVENING, BEFORE A SHOWER-
LESS PERIOD EXPECTED OVERNIGHT. HOWEVER, SCATTERED SHOWERS ARE
ONCE AGAIN POSSIBLE ON WEDNESDAY.

GUIDANCE EARLIER WAS SHOWING THE POTENTIAL FOR MVFR CIGS/VSBYS
AROUND DAYBREAK WEDNESDAY INTO THE DAY, BUT HAS NOW BACKED OFF OF
THIS POTENTIAL. FOR NOW WE ONLY HAVE A SCATTERED DECK AROUND
2,000-2,500 FEET IN THE FORECAST.

WINDS BEHIND THE FRONT WILL START OUT WEST-NORTHWEST, THEN
EVENTUALLY BECOME NORTHEAST OVERNIGHT INTO WEDNESDAY MORNING.

OUTLOOK...
WED NIGHT AND THU...GENERALLY VFR...EXCEPT MVFR POSSIBLE IN
-SHRA... MAINLY CONFINED TO PHL, PNE, ILG, ABE, RDG.

FRI THRU SAT NIGHT...VFR CONDITIONS EXPECTED.

SUN...VFR CONDITIONS MAY DETERIORATE TO MVFR OVER THE INTERIOR IN
AFTN SHRA/TSRA.

&&

.MARINE...
SUB-SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED TONIGHT INTO
WEDNESDAY. SEAS WILL REMAIN 3-4 FEET, AND SOUTH-SOUTHWEST WINDS.
HOWEVER, AS THE FRONT PASSES THROUGH, WINDS WILL DIMINISH AND
BECOME NORTHEAST, STARTING FROM NORTH TO SOUTH DURING WEDNESDAY.

OUTLOOK...
THU THRU SAT...PERSISTENT ONSHORE OUT OF THE SOUTHEAST. WINDS ARE
EXPECTED TO REMAIN BELOW SCA CRITERIA. HOWEVER...THERE IS A LOW
PROBABILITY THAT SEAS MAY APPROACH SCA LEVELS BY SATURDAY.

SUN...SUB-SCA CONDITIONS EXPECTED.

&&

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

&&

$$

SYNOPSIS...FRANCK
NEAR TERM...IOVINO
SHORT TERM...ROBERTSON
LONG TERM...FRANCK
AVIATION...FRANCK/ROBERTSON
MARINE...FRANCK/ROBERTSON


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