Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 280759
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
359 AM EDT TUE JUL 28 2015

.SYNOPSIS...
WEAK HIGH PRESSURE COVERS THE NORTHEAST UNITED STATES THROUGH
WEDNESDAY. A VERY WEAK COOL FRONT PASSES THROUGH THE MID ATLANTIC
STATES THURSDAY NIGHT. ANOTHER COOL FRONT MAY APPROACH FROM THE
NORTHWEST NEXT MONDAY.  MEANWHILE LOW PRESSURE CENTERS ALONG THE
SOUTHEAST COAST OF THE UNITED STATES THIS WEEK WILL BE MONITORED FOR
POSSIBLE NORTHWARD DEVELOPMENT NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE SYNOPTIC SETUP IS COMPRISED OF AN UPPER-LEVEL TROUGH AXIS NOW TO
OUR EAST WITH A RIDGE BUILDING TO OUR WEST. THIS ALLOWS A
NORTHWESTERLY FLOW ALOFT REGIME TO BE MAINTAINED ACROSS THE
NORTHEAST AND MID ATLANTIC. AT THE SURFACE, WEAK HIGH PRESSURE IS
FORECAST TO SETTLE INTO OUR AREA TODAY.

AS THE RIDGE TO OUR WEST GRADUALLY BUILDS NORTH AND EASTWARD SOME
THROUGH TODAY, THERE DOES NOT APPEAR TO BE MUCH IN THE WAY OF SHORT
WAVE ENERGY /AT LEAST ORGANIZED/ SLIDING SOUTHEASTWARD. AS A RESULT,
NO ORGANIZED AREAS OF LIFT IS FORECAST TO OCCUR TODAY WITHIN A VERY
WARM TO HOT AND HUMID AIR MASS. THE FORECAST SOUNDINGS DO SHOW
DECENT INSTABILITY DEVELOPING THROUGH THE AFTERNOON, HOWEVER ABOVE
ABOUT THE 850 MB LEVEL IT IS DRY. THE WATER VAPOR IMAGERY EARLY THIS
MORNING SHOWS A LOT OF MID LEVEL DRY AIR FROM AROUND THE EASTERN
GREAT LAKES TO THE MID ATLANTIC. AS A RESULT, ANY CONVECTION THAT
CAN DEVELOP SHOULD BE ISOLATED AND ALSO PULSE DRIVEN GIVEN LITTLE
FLOW IN THE LOWER TO MID LEVELS. IT APPEARS THAT SEA AND BAY BREEZE
BOUNDARIES ESPECIALLY THIS AFTERNOON COULD FOCUS SOME CONVECTIVE
DEVELOPMENT AND WE CONTINUED WITH SLIGHT CHC POPS FOR THE EASTERN
ZONES AND PORTIONS OF THE DELMARVA. ELSEWHERE, WE OPTED TO CARRY A
DRY FORECAST ATTM AS THERE IS NOT MUCH TO LATCH ONTO FOR CONVECTIVE
INITIATION OTHER THAN TERRAIN. SOME WARMING AROUND THE 925 MB LEVEL
MAY ALSO TEMPER CONVECTIVE DEVELOPMENT.

A POCKET OF NEAR +25C AIR AT 925 MB IS FORECAST TO ADVECT INTO OUR
AREA THROUGH THE AFTERNOON. DESPITE SOME CUMULUS DEVELOPMENT, PLENTY
OF HEATING IS EXPECTED /ALTHOUGH A LACK OF MIXING DUE TO THE WEAK
FLOW/ AND THEREFORE SOME AREAS ARE ANTICIPATED TO REACH 90 DEGREES
THIS AFTERNOON. THE STRONG WARMING OF THE BOUNDARY LAYER MAY ALLOW
THE SURFACE DEW POINTS TO DECREASE AT LEAST SOME ESPECIALLY FARTHER
NORTH ACROSS THE CWA, AND WITH WEAK FLOW SEA AND BAY BREEZES ARE
EXPECTED. THIS WILL PROVIDE SOME COOLING ALONG THE COAST.

AS FOR THE HIGH TEMPERATURES, WE USED AN EVEN BLEND OF THE NAM/GFS
MOS THEN MADE SOME LOCAL TWEAKS.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM WEDNESDAY/...
A WEAK SURFACE HIGH IS FORECAST TO BE OVER OUR AREA TONIGHT AS AN
UPPER-LEVEL RIDGE AXIS SLIDES ACROSS THE EASTERN GREAT LAKES AND
OHIO VALLEY. THIS STILL MAINTAINS NORTHWESTERLY FLOW ALOFT, BUT
LIGHT AND VARIABLE FLOW AT THE SURFACE. DUE TO A LACK OF ORGANIZED
SHORT WAVES TO PROVIDE ENOUGH LIFT, AN ISOLATED SHOWER OR
THUNDERSTORM INITIATED PROBABLY BY ANY LOW-LEVEL CONVERGENCE /I.E.
SEA AND BAY BREEZES/ ARE EXPECTED TO DISSIPATE EARLY IN THE EVENING.
IN ADDITION, ANY CUMULUS FIELD IS EXPECTED TO FLATTEN AND DISSIPATE
WITH PERHAPS SOME HIGH CLOUDINESS OCCURRING AT TIMES.

IT WILL BE A WARM AND MUGGY NIGHT FOR MUCH OF THE CWA AS THE SURFACE
DEW POINTS SHOULD RECOVER FROM ANY DAYTIME HEATING INFLUENCE. THE
COMBINATION OF LIGHT TO CALM WINDS, A MOIST BOUNDARY LAYER AND NOT A
LOT OF CLOUDINESS COULD RESULT IN PATCHY LOW CLOUDS/FOG DEVELOPMENT
LATE.

AS FOR THE LOW TEMPERATURES, A MOS BLEND WAS GENERALLY USED.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
500 MB: HIGH PRESSURE IN THE SOUTHERN PLAINS WILL BE THE DOMINANT
INFLUENCE HERE THROUGH THURSDAY.  OTHERWISE A TROUGH TRIES TO EVOLVE
OVER THE EASTERN STATES NEXT WEEKEND.

TEMPERATURES: THE MONTH OF JULY SO FAR HAS BEEN NEAR NORMAL (TEMPS).
THIS EXTENDED PERIOD WILL SEE CALENDAR DAY AVERAGES ABOVE NORMAL
EVERY DAY. TEMPS SHOULD AVERAGE 5 TO 7 DEGREES ABOVE NORMAL WEDNESDAY
AND THURSDAY AND 3 TO 5 DEGREES ABOVE NORMAL FRIDAY THROUGH SUNDAY
AND THEN MORE THAN 5 DEGREES ABOVE NEXT MONDAY AUGUST 3.

FORECAST BASIS: UNLESS OTHERWISE NOTED, A 50 50 BLEND 00Z/28 GFS/NAM
MOS GUIDANCE WEDNESDAY-THURSDAY, 00Z/28 MEX MOS THURSDAY NIGHT AND
FRIDAY, THEN THE 0521Z/28 WPC GRIDDED ELEMENTS OF MAX/MIN TEMP, 12
HOUR POP, 6 HOUR DEWPOINT-SKY-WIND FROM FRIDAY NIGHT THROUGH NEXT
MONDAY.

THE DAILIES...

WHILE NOT IN THE SYNOPSIS DUE TO ITS POTENTIAL TO CAUSE CONFUSION...
AND ITS LACK OF SIGNIFICANT WEATHER IMPACT, IT LOOKS LIKE THERE
WILL BE A LEFTOVER WIND SHIFT BOUNDARY SOMEWHERE NEAR I-95 THROUGH
THURSDAY BEFORE A MORE STRUCTURED WEAK COOL FRONTAL PASSAGE OCCURS
THURSDAY NIGHT.

WEDNESDAY...RELATIVELY DRY HEAT. PWAT ~1.35 INCHES. HEAT INDEX
BELOW 100F. SOUTHWEST WIND GUST 15 MPH DURING THE AFTERNOON
EXCEPT WEAK SEA BREEZES COASTAL LOCATIONS BEGINNING AROUND NOON.
USED THE WARMER MAV TEMPS FOR THE DAYTIME FCST. FCST MAX TEMPS MAY
BE A DEGREE TOO LOW. OVERALL CONFIDENCE: ABOVE AVERAGE.

THURSDAY...APPROACHING WET BULB FRONT WITH THE 850 MB HOT PROD OF
18-20C AHEAD OF THE CF AND A QUICK START TO 90F THURSDAY MORNING.
AFTERNOON DEWPOINTS ARE EXPECTED TO BE MUCH HIGHER THAN WEDNESDAY
(BY ALMOST 10F). RAISED THE 00Z/28 NCEP GUIDANCE USING THE 00Z/28
ECMWF BUT DID SO WITH LESS THAN IDEAL CONFIDENCE.

MLCAPE BUILDS IN CENTRAL PA TO 1400J BY 18Z THU AND 600J NJ.
APPEARS UNLIKELY TO HAVE ANY SHOWERS OR TSTMS GOING IN OUR AREA
BEFORE 16Z AND PROBABLY NOT TO THE I-95 CORRIDOR TIL NEAR 22Z.
THAT SHOULD ALLOW MORE WARMING THAN MODELED AND HI NEARING 100F BY
18Z. MAX TEMPS SHOULD REMAIN BELOW RECORDS WHICH ARE 97-99F EXCEPT
KMPO 90. SSW WIND GUST 15-20 MPH DURING THE AFTN.

WHAT COULD PREVENT THE HEAT INDEX REACHING 100F...THURSDAY MORNING
SHOWERS AND TSTMS VCNTY KPHL SOUTH AND EAST WHICH WOULD LESSEN
SUNSHINE AND MAKE IT MORE DIFFICULT FOR THE AIR TEMPERATURE TO
EXCEED 90F. THERE ARE MODEL HINTS OF A WEAK INSTABILITY BURST
TRYING TO SHOVE NEWD INTO THE DELMARVA AND SNJ THURSDAY MORNING.

A SCT-BKN BAND OF SHOWERS AND TSTMS SHOULD DEVELOP AND PASS ACROSS
THE AREA THU AFTN/NIGHT.  PWAT INCREASES TO 1.9 INCHES ALONG THE I-
95 CORRIDOR DURING THURSDAY EVENING SO HEAVY RAINERS AND LOCAL POOR
DRAINAGE FLOODING ANTICIPATED AND CANT RULE OUT ISOLATED FF. WHILE
TIMING IS EXCELLENT FOR STRONG TSTM DEVELOPMENT, SVR UNLIKELY SINCE
0-6KM BULK SHEAR IS PRETTY WEAK AND LAPSE RATES VIA TT INDEX LOOK
PRETTY POOR. SREF MODELED PWAT BACK EDGE OF 1.5 INCHES DOWN TO A
KDOV- KACY LINE BY 12Z FRIDAY.

FRIDAY...DEWPOINTS LOWER BY 10 TO 12F ON LIGHT NLY FLOW AND AIR
TEMPS DOWN 2-3F. BLUE MOON AND POTENTIALLY NICE HOT SUMMER DAY FOR
THE END OF JULY. ABOVE AVERAGE CONFIDENCE.

SATURDAY AND SUNDAY...HEATS UP MAYBE A BIT MORE EACH DAY ON WSW
AFTERNOON WIND GUSTS 10-15 MPH. A NICE WEEKEND SINCE AFTERNOON
DEWPOINTS STILL REMAIN PRETTY MODEST...LOW TO MID 60S. SMALL CHC
OF A TSTM NE PA SAT EVE IN WAA - THIS PER 140J NEAR KHZL MIDDAY
REACHING KBLM BY 00Z/SUNDAY.  AVERAGE CONFIDENCE.

NEXT MONDAY...MORE HUMID AND CONTD HOT. 2000J MLCAPE I95 SEWD.
AVERAGE CONFIDENCE ON THE FCST DETAILS.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

TODAY...LOCAL LOW CLOUDS/FOG DISSIPATE BY MID MORNING, OTHERWISE
VFR WITH A CLOUD BASE MOSTLY BETWEEN 3500-5000 FEET. AN ISOLATED
SHOWER OR THUNDERSTORM MAY DEVELOP THROUGH THE DAY ESPECIALLY
SOUTH AND EAST OF KPHL. SEA/BAY BREEZES ARE EXPECTED TO DEVELOP BY
MID AFTERNOON AND AFFECT KACY, KMIV AND KILG WITH WINDS TURNING
MORE FROM THE SOUTHEAST.

TONIGHT...MAINLY VFR. HOWEVER DUE TO THE MOIST AIR MASS IN PLACE,
SOME LATE NIGHT LOW CLOUDS/FOG MAY DEVELOP, AND OUR CONFIDENCE IS
ON THE LOWER SIDE AT THIS TIME. LIGHT SOUTHERLY TO CALM WINDS.

OUTLOOK...
WEDNESDAY THROUGH THURSDAY MORNING...MAINLY VFR. HOWEVER, THE
HIGH HUMIDITY LEVELS MAY RESULT IN SOME LATE NIGHT AND EARLY
MORNING MVFR OR IFR LOW CLOUDS, HAZE AND FOG. LIGHT SW WIND.

THURSDAY AFTERNOON AND THURSDAY NIGHT...A CHANCE OF SHOWERS AND
THUNDERSTORMS THAT MAY RESULT IN MVFR OR IFR CONDITIONS AT TIMES.
GRADIENT SW WIND GUSTS 15-20 KT THU AFTN.

FRIDAY THROUGH SATURDAY...MAINLY VFR.  LIGHT WIND,  MAINLY NORTH
FRIDAY MORNING WITH SEABREEZES BOTH FRIDAY AND SATURDAY.

&&

.MARINE...
THE CONDITIONS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY
CRITERIA THROUGH TONIGHT. A SOUTHERLY FLOW WILL CONTINUE WITH SOME
ENHANCEMENT OCCURRING THIS AFTERNOON AND EARLY EVENING AS A SEA AND
BAY BREEZE DEVELOPS. THE SEAS SHOULD RUN IN THE 1-3 FEET RANGE
THROUGH TONIGHT.

OUTLOOK...
WEDNESDAY THROUGH SATURDAY...NO MARINE HEADLINES ARE ANTICIPATED.

&&

.RIP CURRENTS...
A LONG PERIOD /AROUND 10 SECONDS/ SWELL FROM THE EAST-SOUTHEAST WILL
CONTINUE TODAY. A SOUTHERLY WIND AT 10-15 MPH WITH SOME AFTERNOON
SEA BREEZE ENHANCEMENT ALONG WITH WAVES OF AROUND 2 FEET IN THE SURF
ZONE ARE FORECAST TODAY. THE SETUP IS SIMILAR TO YESTERDAY AND
THEREFORE WE WILL MAINTAIN A MODERATE RISK OF DANGEROUS RIP CURRENTS
FOR BOTH THE NEW JERSEY AND DELAWARE COASTS.

SST`S CONTINUE ABOVE NORMAL!

&&

.CLIMATE...
KACY RAINFALL 6.33 RANKED 15TH WITH THE POR DATING BACK THROUGH
1874. WETTEST 13.09 IN 1959.

KABE MAY BE NEAR RECORD ON WEDNESDAY JULY 29. THE RECORD THERE IS
IS 96 SET IN 1954. RIGHT NOW WE`RE FCSTG 94.

&&

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

&&

$$
SYNOPSIS...DRAG 4A
NEAR TERM...GORSE
SHORT TERM...GORSE
LONG TERM...DRAG 4A
AVIATION...DRAG/GORSE 4A
MARINE...DRAG/GORSE 4A
RIP CURRENTS...
CLIMATE...4A



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