Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 270728
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
328 AM EDT MON JUL 27 2015

.SYNOPSIS...
A COLD FRONT IS FORECAST TO WEAKEN AND DISSIPATE INTO OUR AREA
TODAY. HIGH PRESSURE WILL THEN BUILD EASTWARD INTO THE REGION FOR
THE MIDDLE OF THE WEEK BEFORE ANOTHER COLD FRONT COMES THROUGH
THURSDAY NIGHT. HIGH PRESSURE WILL BUILD EASTWARD FOR THE END OF
THE WEEK WITH A FRONTAL BOUNDARY LOCATED TO OUR SOUTH.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
THE SYNOPTIC SETUP IS COMPRISED OF NORTHWEST FLOW ALOFT WITH AN
EMBEDDED SHORT WAVE TROUGH. THIS FEATURE WILL CROSS OUR AREA DURING
THE COURSE OF TODAY. THE CONTINUATION OF PVA WITH LINGERING
INSTABILITY AND VEERING FLOW WITH HEIGHT IN THE LOWER TO MID LEVELS
IS MAINTAINING CONVECTION EARLY THIS MORNING. THE FLOW/SHEAR IS ON
THE LIGHTER SIDE, HOWEVER ORGANIZATION IS BEING MAINTAINED PROBABLY
DUE TO COLD POOLS AND NEW UPDRAFT CORES ALONG THE LEADING EDGE. THE
MODEL GUIDANCE IN GENERAL SUGGESTS THAT A GRADUAL WEAKENING TREND
OCCURS WITH AN EASTERN EXTENT FOR AWHILE THIS MORNING BEFORE
ADDITIONAL ACTIVITY DEVELOPS WITH RENEWED HEATING WITHIN INCREASING
INSTABILITY. THEREFORE WE BUMPED UP POPS QUITE A BIT FOR A TIME THIS
MORNING THEN TRENDED BACK TOWARD THE CHC RANGE FOR MOST OF THE AREA.

THE PW VALUES ARE AROUND 1.5 INCHES, AND THIS COMBINED WITH
CLUSTERING OF THE CONVECTIVE UPDRAFTS /EVEN SOME BACK BUILDING/
EARLY THIS MORNING IS LEADING TO VERY HEAVY RAINFALL IN SOME AREAS.
THIS WILL PRODUCE SOME LOCALIZED FLOODING. IT DOES NOT APPEAR A LOT
OF LIFT IS NEEDED WITHIN THE AIRMASS TO PROMOTE NEW DEVELOPMENT AS A
WEAKENING COLD FRONT GENERALLY DISSIPATES INTO OUR AREA. A WEAK
SURFACE TROUGH MAY PERSIST THOUGH AND HELP FOCUS SOME NEW
DEVELOPMENT THROUGH THE DAY.

AS FOR THE HIGH TEMPERATURES, WE MOSTLY WENT WITH A NAM/GFS MOS
BLEND WITH THE ANTICIPATION OF ENOUGH CLOUDS AND CONVECTION AROUND.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM TUESDAY/...
THE SHORT WAVE TROUGH IS FORECAST TO SHIFT TO OUR EAST THIS EVENING,
AND THEN SOME SUBTLE HEIGHT RISES OCCUR AS SLIGHT RIDGING STARTS TO
ARRIVE FROM THE WEST. AS A RESULT, THE PVA WITHIN THE NORTHWESTERLY
FLOW ALOFT IS FORECAST TO WANE AND THIS SHOULD ALLOW ANY CONVECTION
TO DISSIPATE BY LATE EVENING FOR MUCH OF THE AREA. THEREFORE, WE
TRENDED THE POPS DOWNWARD THROUGH THE EVENING WITH THE LAST
MENTIONABLE CONVECTION IN PORTIONS OF THE DELMARVA OVERNIGHT.
OTHERWISE, SOME PARTIAL CLEARING SHOULD TAKE PLACE FROM THE
NORTHWEST ALTHOUGH SOME HIGH LEVEL CLOUDS MAY CONTINUE TO MOVE
ACROSS.

THE PRESENCE OF LIGHT WINDS AND AREAS OF LESSENING CLOUD COVER MAY
RESULT IN LOCAL FOG DEVELOPMENT OVERNIGHT, ESPECIALLY IN AREAS WHERE
HEAVY RAIN HAS FALLEN WHICH WILL ASSIST IN LOW-LEVEL MOISTURE
POOLING. THIS MAY BE LOCALIZED ENOUGH THEREFORE IT WAS NOT INCLUDED
ATTM. AS FOR THE LOW TEMPERATURES, WE SIDED WITH A GFS/NAM MOS BLEND
WITH SOME MINOR LOCAL TWEAKS.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
TUESDAY THROUGH WEDNESDAY NIGHT: A GRADUAL CONTINUED UPTICK IN
HEAT AND HUMIDITY WITH A STRONG RIDGE ACROSS THE SOUTHERN PLAINS
MAKING ANOTHER CHARGE INTO THE REGION WITH RISING HEIGHTS. THIS
WILL RESULT IN A MAINLY DRY PERIOD (POSSIBLE EXCEPTION OF AN
ISOLATED THUNDERSTORM SOUTH TUESDAY AFTERNOON). FOR ACTUAL HIGH
TEMPERATURES, MODELED 925 MB TEMPERATURES RISE FROM AROUND 23C ON
TUESDAY TO 25C FOR WEDNESDAY. THIS EQUATES TO HIGH TEMPERATURES
STARTING OFF AROUND 90 ON TUESDAY THEN RISING INTO THE MID 90`S
FOR WEDNESDAY, STARTING ANOTHER POTENTIAL MODELED HEAT WAVE FOR
MOST OF THE REGION. LESS SPREAD IN PRESENT IN THE OPERATIONAL
MODELS AND THE ENSEMBLES IN THIS PERIOD COMPARED TO YESTERDAY AS
THE GFS HAS TRENDED COOLER WITH TEMPERATURES. FORTUNATELY MODELED
DEW POINTS ARE IN THE LOW/MID 60`S DURING THE PEAK HEATING HOURS
BOTH TUESDAY AND WEDNESDAY. THIS WOULD LIMIT THE MAXIMUM HEAT
INDEX TO BETWEEN 95 AND 100 DEGREES.

THURSDAY THROUGH SUNDAY: THE COLD FRONTAL BOUNDARY APPROACHING THE
REGION TO START THIS PERIOD WILL LIKELY BE THE TRIGGER FOR AN
INCREASE IN CLOUDS AND SOME SCATTERED AFTERNOON/EVENING SHOWERS AND
STORMS ON THURSDAY. ONCE AGAIN, THE LACK OF SHEAR LOOKS TO BE A
LIMITATION IN THE WAY OF ANY SEVERE WEATHER. HOWEVER, AN ISOLATED
STRONG WIND GUST CAN NOT BE RULED OUT.

THE 12Z (DAYTIME) RUNS OF THE GFS CONTINUE TO RUN WARMER AND DRIER
ON THURSDAY THAN OTHER MODELS AND GFS RUNS, CURRENT THINKING IS THIS
AN ANOMALY RATHER THAN THE RULE AND THE FORECAST WILL GO MORE
TOWARD THE ECMWF WITH TEMPERATURES ON THURSDAY. HIGHER HUMIDITY
THOUGH GIVES THE REGION A HIGHER CHANCE FOR THE HEAT INDEX TO
REACH 100 DEGREES IN PARTS OF THE REGION.

SOME DRIER AND PERHAPS SLIGHTLY COOLER AIR IS LIKELY TO END THE
POTENTIAL HEAT WAVE BEHIND THE FRONT ON FRIDAY. COMPARED TO JUST
YESTERDAY, THE OPERATIONAL MODELS AND THE RESPECTIVE ENSEMBLES
ARE FARTHER OFFSHORE WITH THE FRONT AND ARE SHOWING A MUCH LOWER
THREAT FOR WAVES OF LOW PRESSURE DEVELOP ALONG THE BOUNDARY. THE
FORECAST REFLECTS A DRY BUT STILL HOT CONDITIONS NEXT WEEKEND WITH
EVEN WARM AIR ADVECTION AGAIN BY NEXT SUNDAY WITH A FRONTAL
PASSAGE TO OUR NORTH.

&&

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

TODAY...SHOWERS AND SOME THUNDERSTORMS EARLY THIS MORNING SETTLING
EASTWARD ACROSS MUCH OF THE AREA. THIS WILL RESULT IN A TIME OF
MVFR/IFR CONDITIONS ESPECIALLY VISIBILITIES. OUTSIDE OF ANY SHOWERS
AND THUNDERSTORMS, VFR IS ANTICIPATED /LOCAL LIGHT FOG POSSIBLE
EARLY THIS MORNING/. SOME SHOWERS AND THUNDERSTORMS ARE EXPECTED
THROUGH THE DAY, HOWEVER CARRIED A TEMPO FOR SHOWERS AS THUNDERSTORM
PLACEMENT AFTER THE EARLY MORNING ACTIVITY IS A BIT UNCERTAIN. SOUTH-
SOUTHWEST WINDS GENERALLY 5-10 KNOTS.

TONIGHT...SOME SHOWERS AND THUNDERSTORMS WITH BRIEFLY REDUCED
VISIBILITIES AND/OR CEILINGS IN THE EVENING ARE EXPECTED TO
DIMINISH. THERE IS THE CHANCE FOR LOCAL FOG TO DEVELOP LATE.
SOUTHERLY WINDS 5 KNOTS OR LESS.

OUTLOOK...
TUESDAY THROUGH WEDNESDAY NIGHT: VFR. WINDS AT OR UNDER 10 KNOTS
THROUGH MOST OF THE PERIOD, WITH SOME SOUTHWESTERLY WIND GUSTS
AROUND 15 KNOTS WEDNESDAY AFTERNOON.

THURSDAY AND THURSDAY NIGHT: VFR, ISOLATED TO SCATTERED SHOWERS
THUNDERSTORMS, MAY BRIEFLY REDUCE VISIBILITIES AND CEILINGS.
WEST- SOUTHWEST WIND GUSTS AROUND 15 KNOTS POSSIBLE THURSDAY AND
EVENING, LOCALLY HIGHER GUSTS IN THUNDERSTORMS.

FRIDAY AND FRIDAY NIGHT: VFR. WINDS AT OR UNDER 10 KNOTS.

&&

.MARINE...
THE CONDITIONS ARE ANTICIPATED TO REMAIN BELOW SMALL CRAFT ADVISORY
CRITERIA TODAY AND TONIGHT. A SOUTHERLY FLOW IS EXPECTED TO CONTINUE
AS A DISSIPATING COLD FRONT ARRIVES TODAY. SOME GUSTS TO 20 KNOTS
ARE ANTICIPATED AT TIMES HOWEVER, WITH POTENTIALLY HIGHER GUSTS IN
AND NEAR ANY STRONGER THUNDERSTORM.

OUTLOOK...
SEAS AND WINDS LOOK TO REMAIN BELOW SCA CRITERIA THROUGH FRIDAY.
ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE
THURSDAY AFTERNOON/EVENING WITH THE POTENTIAL FOR A STRONG WIND
GUST OR TWO. SEAS OVERALL FOUR FEET OR LESS WITH WIND GUSTS 20
KNOTS OR LESS THROUGH THURSDAY. SEAS BUILDING TO AROUND FIVE FEET
WITH SOME ISOLATED 25 KNOT FOR A PERIOD THURSDAY NIGHT BEFORE
DECREASING ON FRIDAY.

&&

.RIP CURRENTS...
A LONG PERIOD /10-12 SECOND/ EAST-SOUTHEAST SWELL LOOKS TO
CONTINUE, RESULTING IN A MODERATE RISK OF DANGEROUS RIP CURRENTS
THROUGH TONIGHT FOR THE NEW JERSEY AND DELAWARE COASTS.

&&

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

&&

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



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