Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 240812
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
412 AM EDT THU JUL 24 2014

.SYNOPSIS...
A COLD FRONTAL BOUNDARY WILL CONTINUE MOVING OFFSHORE
TODAY. HIGH PRESSURE WILL BUILD ACROSS THE OHIO VALLEY TONIGHT AND
ON FRIDAY. THE HIGH PRESSURE SYSTEM WILL MOVE EAST OF THE REGION ON
SATURDAY AND BE FOLLOWED BY THE PASSAGE OF A WARM FRONT FROM THE
SOUTH BY SATURDAY NIGHT AND BE LOCATED TO OUR NORTH ON SUNDAY.
ANOTHER COLD FRONTAL BOUNDARY THEN WILL SWEEP FROM WEST TO EAST
ACROSS THE REGION ON MONDAY. A HIGH PRESSURE SYSTEM WILL BUILD IN
BEHIND THE COLD FRONT FOR THE MIDDLE HALF OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A CDFNT WAS WORKING ITS WAY ACRS THE REGION AND SHOULD BEE OFFSHORE
LATER THIS MRNG.  HIGH PRES WILL SLOWLY BUILD IN BEHIND THE FRONT.

HOWEVER, SOME GUID STILL INDICATES THAT THERE IS ENOUGH INSTABILITY
AND WITH THE FRONT LOCATED JUST TO OUR S, THERE COULD BE SOME
SHOWERS AND SCT TSTMS, MAINLY OVER SRN AREAS FROM LATER THIS MRNG
INTO ERLY EVE.  BOTH THE NAM/WRF AND GFS INDICATE AT LEAST SOME
POTENTIAL FOR PRECIP WHILE THE ECMWF IS DRIER.  FOR NOW, WILL CARRY
SOME LOW POPS.

THE HRRR ALSO HAS SOME PRECIP MOVG IN FROM THE S AND W THIS AM.
THERE IS SOME LIGHT STUFF OVER PA AND MD, BUT THE HRRR APPEARS A BIT
OVERDONE.

OVERALL GUID TEMPS LOOK REASONABLE AND WERE GENLY FOLLOWED.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM FRIDAY/...
HIGH PRES WILL BUILD EWD AND INTO THE AREA TONIGHT.  ANY PRECIP WILL
END EARLY AND THE SKY WILL CLEAR.  OVERALL, A QUIET NIGHT IS IN
STORE.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
FRIDAY AND FRIDAY NIGHT: HIGH PRESSURE GLIDES EAST FROM THE OHIO
VALLEY INTO OUR REGION. VARIABLE WINDS, PLENTY OF SUNSHINE AND NOT
THAT HOT SINCE THIS AIRMASS WILL BE COMING FROM CANADA! LITTLE
SPREAD IN THE MODELS ON MOST IF NOT ALL WEATHER ELEMENTS. TRICKIEST
PART OF THIS PERIOD IS HOW MUCH RADIATIONAL COOLING CAN OCCUR IN
RURAL AREAS BEFORE THE FLOW TURNS MORE SOUTHERLY BY SATURDAY.
OPTED TO GO A TOUCH COOLER THAN MEX/MAV/MET IN A FEW SPOTS WITH
LOWS FRIDAY NIGHT.

SATURDAY AND SATURDAY NIGHT: A WARM FRONT APPROACHES THE REGION FROM
THE SOUTH AND WITH A DEPARTING HIGH PRESSURE THE FLOW TURNS
SOUTHERLY. MODELED MOMENTUM TRANSFER SUGGESTS SOME GUSTS CLOSE TO 20
MPH ARE POSSIBLE IN THE AFTERNOON, WENT HIGHER THAN A STANDARD
125% FOR WIND GUSTS. MID-LEVEL AND SURFACE TEMPERATURES LOOK TO
RESPOND IN KIND AFTER THE WARM FRONTAL PASSAGE, 925 MB TEMPS NEAR 20-22C
SHOULD YIELD SURFACE TEMPERATURES JUST UNDER 90 FOR PHL AND IN THE
80`S ELSEWHERE ACROSS THE REGION. HUMIDITY IS ON THE RISE BUT THIS
WILL BE LIKE MORE TYPICAL JULY HEAT WITH HEAT INDEX VALUES WELL
UNDER ADVISORY LEVELS. THE WARM FRONT MAY PROVIDE ENOUGH LIFT FOR
SOME SCATTERED SHOWERS AND THUNDERSTORMS FOCUSED ACROSS THE
NORTHERN PART OF THE REGION. THE 21Z SREF AND THE LAST TWO ECMWF
RUNS HAVE THESE PINED DOWN WELL. INCREASING CIN COUPLED WITH 700
MB TEMPS NEAR 10C COULD ALLOW FOR THE FORMATION OF A WEAK CAP
ACROSS THE SOUTHERN PART OF THE REGION, BEING FURTHER AWAY LOWER
CHANCE POPS WERE WARRANTED WHEN COMPARED TO LOCATIONS FURTHER
NORTH.

SUNDAY AND SUNDAY NIGHT: CONTINUED WEST-SOUTHWEST FLOW IN THE WARM
SECTOR. THE LAST FEW GFS RUNS HAVE BEEN MORE AGGRESSIVE WITH
CONVECTION BY THE AFTERNOON AND EVENING HOURS. A COMMON THEME THIS
SUMMER. THINK THE GFS IS TO AGGRESSIVE WITH THIS. HOWEVER, STORM
CHANCES SHOULD INCREASE AS THE MAIN LOW PRESSURE SYSTEM AND COLD
FRONT APPROACH THE REGION. GOOD AGREEMENT AMONG THE GFS ENSEMBLES,
ECMWF ENSEMBLE MEAN AND THE OPERATIONAL MODELS THAT THE HIGHEST
CHANCE WILL BE SUNDAY NIGHT. MAINTAINED LOW END LIKELY POPS ACROSS THE
NORTH AND HIGH END CHANCE ACROSS THE SOUTH. FOR QPF STAYED CLOSE TO
THE SREF AND ECMWF SIMILAR TO SATURDAY. THOUGH DID RAISE IT SLIGHTLY
TO ACCOUNT FOR THE MORE AGGRESSIVE GFS. TEMPERATURES MAY BE RAIN
COOLED SUNDAY BUT DID NOT GO IN THAT DIRECTION ATTM. FAIR SHOT AT 90
FOR PHL WITH SLIGHTLY WARMER MODELED MID-LEVEL TEMPERATURES THAN
SATURDAY.

MONDAY AND MONDAY NIGHT: THE COLD FRONT MOVES THROUGH LIKELY MONDAY
AFTERNOON. HOWEVER THIS SHOULD BE TO LITTLE TO LATE IN TERMS OF
ANOTHER ROUND OF SHOWERS AND STORMS. THE MAIN CAPE AXIS IS LIKELY TO
OFFSHORE AT THIS TIME AND LITTLE IS LEFT FOR A TRIGGER BESIDES THE
ACTUAL FRONTAL BOUNDARY. HOWEVER MAINTAINED LOW CHANCE POPS SINCE THE
FRONT WILL STILL BE IN THE REGION. CLEARED CONDITIONS OUT MONDAY
NIGHT WITH A RETURN TO WESTERLY FLOW. ANOTHER GUSTY DAY AS ONCE
MODELED MOMENTUM TRANSFER SHOWS POTENTIAL FOR SOME GUSTS NEAR 20
MPH.


TUESDAY AND WEDNESDAY: ANOTHER CANADIAN AIRMASS COMES DOWN INTO THE
REGION AS THE SAME GENERAL PATTERN FROM THE WINTERTIME CONTINUES
WITH FEW BREAKS. COOL NORTHWESTERLY FLOW WILL BE IN PLACE AS MOST
LOCATIONS STRUGGLE TO 80 FOR A HIGH. EVEN WITH THIS ABNORMALLY COOL
AIRMASS THERE IS GOOD AGREEMENT AMONG THE MEX, WPC AND MODELED TWO
METER TEMPERATURES. TRENDED SLIGHTLY COOLER THAN WPC GIVEN THE
LATEST 00Z ECMWF WHICH IS ON THE COOLEST END OF THE MODEL GUIDANCE.
LAPSE RATES MAY STEEPEN UP TUESDAY AFTERNOON FOR THE FORMATION OF
SOME CUMULUS AND SPOTTY SHOWERS/THUNDER ON THE BACKSIDE OF THE TROUGH
ACROSS THE NORTH WITH THE AID OF ELEVATION. OTHERWISE BOTH DAYS
LOOK MOSTLY SUNNY.

&&

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

GENLY VFR CONDS ARE EXPECTED TODAY.  THERE COULD BE SOME LCL MVFR
THIS MRNG IN LOW CLOUDS OR FOG.  ADDITIONALLY, THERE COULD BE SOME
SHRA OR ISOLD TSRA, MAINLY S LATER THIS MRNG THRU ERLY EVE WHICH CUD
BRIEFLY DECREASE CIGS/VSBYS.  HOWEVER, ODDS ARE LOW ENOUGH TO NOT
MENTION IN THE INDIVIDUAL TAF SITES.  WIND IS EXPECTED TO BE NW OR N
AROUND 10 KTS TODAY DECREASING TO LESS THAN 10 KTS TONIGHT.

OUTLOOK...
FRIDAY AND FRIDAY NIGHT: VFR

SATURDAY THROUGH MONDAY: BRIEF MVFR AND IFR RESTRICTIONS IN
SCATTERED THUNDERSTORMS. HIGHEST CHANCE FOR RESTRICTIONS IS ON
SUNDAY AFTERNOON AND EVENING FOR RDG, ABE, TTN, AND POINTS NORTH.

&&

.MARINE...
WITH HIGH PRES BUILDING INTO THE REGION, NO MARINE HEADLINES ARE
ANTICIPATED THRU THE NR AND SHORT TERM PDS.

OUTLOOK...
FRIDAY THROUGH SATURDAY NIGHT: SEAS AND WINDS EXPECTED TO STAY UNDER
SCA CRITERIA. A FEW WIND GUSTS AROUND 20 KNOTS POSSIBLE SATURDAY
AFTERNOON.

SUNDAY AND MONDAY: SEAS INCREASE TO FOUR FEET ON SUNDAY AND PERHAPS
FIVE FEET BY MONDAY MORNING BEFORE FALLING BELOW FIVE FEET MONDAY
NIGHT. A FEW WIND GUSTS AROUND 20 KNOTS POSSIBLE SUNDAY AND MONDAY
AFTERNOONS.

&&

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

&&

$$
SYNOPSIS...GAINES
NEAR TERM...NIERENBERG
SHORT TERM...NIERENBERG
LONG TERM...GAINES
AVIATION...GAINES/NIERENBERG
MARINE...GAINES/NIERENBERG





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