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Area Forecast Discussion
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000
FXUS61 KPHI 300952
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
552 AM EDT SAT AUG 30 2014

.SYNOPSIS...
HIGH PRESSURE CENTERED OFF THE NEW ENGLAND COAST WILL CONTINUE TO
MOVE EAST TODAY AND TONIGHT. MEANWHILE, A WARM FRONT IS EXPECTED
TO LIFT NORTH LATE SATURDAY, THEN BECOME NEARLY STATIONARY NEAR
THE CANADIAN BORDER SUNDAY THROUGH TUESDAY. A COLD FRONT IS THEN
EXPECTED TO MOVE ACROSS THE AREA TUESDAY NIGHT AND EARLY
WEDNESDAY, FOLLOWED BY HIGH PRESSURE FOR THE REMAINDER OF THE
WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
OUR WEATHER WILL BE IN TRANSITION TODAY AS AN UPPER-LEVEL RIDGE 
SLIDES ACROSS AND THEN SHIFTS TO OUR EAST. AS THIS OCCURS, SURFACE 
HIGH PRESSURE WILL CONTINUE TO RETREAT TO THE NORTHEAST. THIS OPENS 
THE DOOR FOR A SOUTHERLY FLOW THAT WILL BRING IN MORE MOISTURE.

THE MODEL GUIDANCE SHOWS WAA OCCURRING THROUGH THE DAY, HOWEVER 
THERE IS A MORE NOTED INCREASE TOWARD LATE AFTERNOON. THIS ALSO 
OCCURS AS AN INCREASE IN THE MOISTURE ARRIVES, WHICH IS SEEN IN THE 
THETA-E FIELDS. THIS INCREASE IN MOISTURE WILL ALLOW THE SURFACE DEW 
POINTS TO INCREASE, ALTHOUGH THIS PROCESS DURING THE DAYLIGHT HOURS 
WILL PROBABLY BE GRADUAL FOR MUCH OF THE AREA. THE MOISTURE INCREASE 
SHOULD ALSO RESULT IN MORE CLOUDINESS THROUGH THE DAY WITH CUMULUS 
DEVELOPMENT BELOW SOME MID TO HIGH LEVEL CLOUDS ON THE WESTERN FLANK 
OF THE DEPARTING RIDGE. THIS INCREASE IN MOISTURE WITHIN THE 
SOUTHERLY FLOW IS ALREADY EVIDENT EARLY THIS MORNING WITH AREAS OF 
CLOUDINESS ADVECTING NORTH-NORTHEASTWARD FROM VIRGINIA AND
MARYLAND. THERE ARE ALSO SOME LOW CLOUDS ACROSS NORTHEASTERN
PENNSYLVANIA DUE TO SOME WEAK UPSLOPE FLOW COMBINED WITH BOUNDARY
LAYER COOLING. AT LEAST SOME FORECAST SOUNDINGS INDICATE A CAP IN
PLACE AS WARMING OCCURS ALOFT DURING THE DAY, HOWEVER MOISTURE
NEAR THE BASE OF THE CAP SHOULD HELP FOCUS SOME ADDITIONAL CLOUD
DEVELOPMENT ESPECIALLY INLAND.

LOW PRESSURE TRACKING ACROSS THE GREAT LAKES REGION AHEAD OF AN 
UPPER-LEVEL TROUGH WILL HELP ASSIST IN WAA DOWNSTREAM, WHICH WILL 
ORGANIZE A WARM FRONT TO OUR SOUTHWEST. IN ADDITION, CONVECTIVE 
DEVELOPMENT IS EXPECTED TO OUR WEST WITHIN THE DEVELOPING WARM 
SECTOR AND NEAR A PRE-FRONTAL TROUGH. HOWEVER, THE LIFT WITH THESE 
FEATURES ARE EXPECTED TO REMAIN TO OUR WEST AND THEREFORE TODAY WAS 
KEPT DRY.

AS FOR HIGH TEMPERATURES, WE USED A BLEND OF THE NAM/GFS MOS THEN 
MADE A LITTLE BIT OF AN UPWARD ADJUSTMENT FOR SOME INLAND AREAS 
GIVEN THE WAA. WE ARE NOT ANTICIPATING TO OBTAIN DEEP MIXING AND THE 
SURFACE FLOW LOOKS MOSTLY FROM THE SOUTH OR SOUTHEAST. THIS WOULD 
TEND TO KEEP TEMPERATURES FROM INCREASING DRAMATICALLY, ALTHOUGH IT 
SHOULD BE WARMER THAN YESTERDAY WITH SOME ADDED HUMIDITY AS WELL.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
HIGH PRESSURE AT THE SURFACE WILL BE SITUATED TO OUR EAST ALLOWING A 
SOUTHERLY FLOW TO BE MAINTAINED. OUR REGION WILL BECOME INCREASINGLY 
MORE ON THE NORTHWESTERN FLANK OF THE UPPER-LEVEL RIDGE, AND THE 
PASSAGE OF A WARM FRONT WILL ALLOW MUCH MORE HUMID AIR TO OVERSPREAD 
THE REGION. WE SHOULD SEE A DECENT INCREASE IN THE SURFACE DEW 
POINTS IN THE EVENING AS ANY MIXING DIMINISHES. WHILE WE STILL 
MAINTAIN SOME WAA THROUGH THE NIGHT, THIS GENERALLY TURNS WEAK. WE 
DO MAINTAIN SOME MOISTURE ADVECTION THOUGH, AND THIS COMBINED WITH A 
WARMER BOUNDARY LAYER MAY LEAD TO AREAS OF STRATUS AND EVEN SOME 
FOG. 

THE MAIN SHORT WAVE TROUGH THAT IS FORECAST TO BE AMPLIFYING ACROSS 
THE GREAT LAKES IS FORECAST TO HANG BACK FAIRLY FAR TO OUR WEST. 
THERE DOES APPEAR TO BE SOME LEAD SHORT WAVES TRACKING NORTHEASTWARD 
ALONG THE PERIPHERY OF THE UPPER-LEVEL RIDGE. THE FORECAST SOUNDINGS 
DO SHOW SOME INCREASE IN THE INSTABILITY TONIGHT, HOWEVER THERE MAY 
NOT BE MUCH FORCING. THERE COULD BE SOME WEAKENING SHOWERS/THUNDER 
APPROACHING OUR NORTHWEST ZONES THIS EVENING BEFORE THEY DISSIPATE, 
THEN PERHAPS SOME ADDITIONAL ACTIVITY MAY TRY AND ARRIVE ACROSS OUR 
WESTERN ZONES TOWARD DAYBREAK. THE LATTER MAY BE ASSOCIATED WITH AN 
EMBEDDED SHORT WAVE TRACKING AROUND THE RIDGE. OVERALL, WE THINK THE 
GREATER CHC WOULD BE TO OUR WEST CLOSER TO THE SHORT WAVE TROUGH AND 
ITS ASSOCIATED LIFT. THEREFORE ATTM, WE WERE SLOW TO INCREASE THE 
POPS TOWARD MORNING ACROSS THE WESTERN ZONES. OTHERWISE, AN INCREASE 
IN CLOUDS ESPECIALLY LATE WITH SOME STRATUS DEVELOPMENT AND PERHAPS 
PATCHY FOG. WE ARE NOT ALL THAT CERTAIN HOW MUCH FOG DEVELOPS GIVEN 
THE AIRMASS IS STILL UNDERGOING MOISTENING, THEREFORE WE DID NOT 
INCLUDE FOG ATTM.

AS FOR LOW TEMPERATURES, WE WENT WITH AN INITIAL EVEN BLEND OF THE 
NAM/GFS MOS THEN MADE SOME MAINLY MINOR TWEAKS.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
MID-LEVEL RIDGING OVER THE EASTERN U.S. NEAR THE BEGINNING OF THE 
LONG TERM PERIOD GRADUALLY BECOMES ZONAL TOWARD THE END OF THE 
PERIOD WHICH TRANSLATES INTO ABOVE NORMAL TEMPERATURES FOR MUCH OF 
THE PERIOD.

SUNDAY - TUESDAY...A NEARLY STATIONARY FRONTAL BOUNDARY TO OUR NORTH 
AND A SOUTHWESTERLY FLOW BOTH AT THE SURFACE AND ALOFT WILL PUMP IN 
WARM AND MOIST AIR OVER OUR REGION THROUGH THE PERIOD, BRINGING A 
CHANCE OF SHOWERS AND THUNDERSTORMS EACH DAY. THE BEST CHANCE FOR 
SHOWERS AND THUNDERSTORMS WILL BE SUNDAY NIGHT INTO MONDAY. 
DEWPOINTS WILL RISE INTO THE 70S ACROSS THE REGION WHICH WILL BE 
INDICATIVE OF HIGHER THAN NORMAL PRECIPITABLE WATER 
VALUES...POSSIBLY OVER TWO INCHES. GIVEN THE DRY CONDITIONS OF LATE, 
ANY FLOODING THAT DOES DEVELOP WOULD MOST LIKELY BE URBAN AND POOR 
DRAINAGE TYPE FLOODING. WITH TEMPERATURES A GOOD TEN DEGREES ABOVE 
NORMAL, AND DEWPOINT TEMPERATURES IN THE 70S, IT WILL FEEL LIKE THE 
DOG DAYS OF SUMMER. 

WEDNESDAY...LOW PRESSURE SYSTEM WELL TO THE NORTH OF THE REGION 
SENDS A SOMEWHAT STRONGER COLD FRONT THROUGH OUR AREA. THEN 
CONDITIONS WILL DRY OUT BEHIND THIS FRONT AS HIGH PRESSURE BUILDS IN 
FROM THE WEST DURING THE DAY. DEWPOINTS ARE EXPECTED TO DROP IN TO 
THE MID 60S, AND TEMPERATURES SHOULD DROP A FEW DEGREES TOO, 
ALTHOUGH THEY ARE STILL EXPECTED TO BE ABOVE NORMAL FOR THIS TIME OF 
YEAR. 

THURSDAY - FRIDAY...HIGH PRESSURE CONTINUES TO BUILD BACK INTO OUR 
REGION WITH ZONAL FLOW ALOFT, AND WE SHOULD BE DRY BOTH DAYS. 
TEMPERATURES MAY DROP A DEGREE OR TWO COMPARED TO WEDNESDAY, BUT 
STILL SHOULD BE A LITTLE ABOVE NORMAL.

&&

.AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG, 
KMIV, KACY AND SURROUNDING AREAS.

TODAY...MAINLY VFR, WITH SCATTERED TO BROKEN BASES AROUND 5000 FEET.
SOME STRATUS EARLY THIS MORNING MAINLY NORTH AND WEST OF KABE AND
KRDG. SOUTHERLY WINDS INCREASING TO AROUND 10 KNOTS.

TONIGHT...VFR FOR AWHILE, HOWEVER AN INCREASE IN MOISTURE SHOULD 
RESULT IN AREAS OF STRATUS AND/OR FOG TOWARD MORNING. 
SOUTH-SOUTHWEST WINDS 5 KNOTS OR LESS.

OUTLOOK...
SUNDAY...VFR EARLY. THEN MVFR POSSIBLE IN SCATTERED SHOWERS AND
THUNDERSTORMS...ESPECIALLY NORTH AND WEST OF PHL. MDT CONFIDENCE.

SUNDAY NIGHT INTO MONDAY...IFR CONDITIONS POSSIBLE WITH SHOWERS AND 
THUNDERSTORMS. CONDITIONS IMPROVING TO VFR LATER MONDAY. LOW TO
MDT CONFIDENCE ON PRECIP COVERAGE.

MONDAY NIGHT AND TUESDAY...GENERALLY VFR CONDITIONS EXPECTED.

TUESDAY NIGHT INTO WEDNESDAY...MVFR CONDITIONS POSSIBLE IN SCATTERED 
SHOWERS AND THUNDERSTORMS. LOW TO MDT CONFIDENCE.

LATE WEDNESDAY AND THURSDAY...VFR. MDT CONFIDENCE.

&&

.MARINE...
HIGH PRESSURE WILL CONTINUE TO SHIFT TO OUR NORTHEAST AND EAST 
THROUGH TONIGHT. THIS WILL PRODUCE A SOUTHEAST TO SOUTH FLOW AS A 
WARM FRONT LIFTS NORTH OF THE AREA BY LATE TONIGHT. WHILE THE FLOW 
IS MAINLY ON THE LIGHT SIDE, SOME NEARSHORE ENHANCEMENT COULD OCCUR 
DURING PEAK HEATING. WHILE THE MOISTURE IS FORECAST TO INCREASE WITH 
AN UPTICK IN THE SURFACE DEW POINTS, THE WATER IS ON THE WARM SIDE 
THEREFORE WE MAY NOT HAVE MUCH FOG DEVELOPMENT. OVERALL, THE 
CONDITIONS ARE ANTICIPATED TO REMAIN BELOW SMALL CRAFT ADVISORY 
CRITERIA THROUGH TONIGHT.

OUTLOOK...
SUNDAY...SUB SCA.

SUNDAY NIGHT AND MONDAY...SCA CONDITIONS POSSIBLE AS SEAS BUILD TO AROUND
5 FEET. SUB-SCA CONDITIONS EXPECTED AGAIN LATER MONDAY INTO
TUESDAY. A COLD FRONT WILL APPROACH LATE TUESDAY EVENTUALLY
CROSSING ON WEDNESDAY. SEAS WILL INCREASE BUT ARE EXPECTED TO
REMAIN BELOW BELOW SCA.

&&

.RIP CURRENTS...
THERE IS A MODERATE RISK OF DANGEROUS RIP CURRENTS THROUGH THIS
EVENING, AS ENOUGH OF A SWELL COMPONENT IS STILL PRESENT TO
ENHANCE THE FORMATION OF RIP CURRENTS.

&&

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

&&

$$
SYNOPSIS...MIKETTA
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...MIKETTA
AVIATION...GORSE/MIKETTA
MARINE...GORSE/MIKETTA
RIP CURRENTS...GORSE




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