Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 251705
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
105 PM EDT FRI JUL 25 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD ACROSS THE OHIO VALLEY AND MID-ATLANTIC
TODAY AND MOVE OFFSHORE TONIGHT. ON THE BACKSIDE OF THE HIGH PRESSURE
SYSTEM A WARM FRONT AND ASSOCIATED LOW PRESSURE SYSTEM WILL MOVE ACROSS
THE MIDWEST ON SATURDAY AND INTO OUR REGION BY SATURDAY NIGHT AND
PUSH NORTH OF THE REGION ON SUNDAY. A 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/...
NOT MANY CHANGES NEEDED (ONE WOULD HOPE SO ON A DAY LIKE TODAY)
WITH THE NEXT ESTF UPDATE EITHER. THE MORNING 12Z SOUNDINGS SHOW
AN EXCELLENT CAP AND CONVECTIVE TEMPS AS HIGH AS AROUND 100
DEGREES. LATEST LAPS SOUNDINGS SUGGESTING MAYBE A COUPLE OF
REALLY HIGH BASED CU PRIMARILY FROM THE MASON DIXON LINE/AC
EXPRESSWAY NORTH. TEMPS ON/CLOSE TO SCHEDULE, SO NO CHANGE THERE.
DEW POINTS ARE RUNNING HIGHER THAN EXPECTED AND SOME UPWARD
ADJUSTMENTS HAVE BEEN MADE. A SEA AND BAY BREEZE FRONT IS EXPECTED
TO MOVE INTO NJ AND DE THIS AFTERNOON.

HIGH PRES WILL BUILD INTO THE REGION TODAY AND A DRY AND PLEASANT
DAY IS IN STORE, WITH DEW POINTS IN THE 40S AND 50S, WHICH IS
SPECTACULAR FOR LATE JULY!

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SATURDAY/...
THE HIGH WILL MOVE TO THE EAST TONIGHT AND THE WIND WILL BECOME MORE
S TO SWLY BUT STILL BE LIGHT AND DEW POINTS WILL CREEP UP A BIT, BUT
AGAIN DRY WX IS EXPECTED.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
SATURDAY AND SATURDAY NIGHT: A WARM FRONT APPROACHES THE REGION
FROM THE MIDWEST AND OHIO VALLEY THEN PUSHES NORTHEAST THROUGH THE
REGION SATURDAY NIGHT. THE RESULT WILL BE INCREASE IN SOUTHERLY
MOISTURE AND MOISTURE TRANSPORT INTO THE REGION. MID-LEVEL AND
SURFACE TEMPERATURES LOOK TO RESPOND IN KIND WITH THE SOUTHERLY
AND SOUTHWEST ADVECTION, 925 MB TEMPS NEAR 20C SHOULD YIELD
SURFACE TEMPERATURES JUST UNDER 90 FOR PHL AND IN THE 80`S
ELSEWHERE ACROSS THE REGION. AS MENTIONED IN THE PREVIOUS FORECAST
THE RAPID RISE OF DEWPOINTS APPEARS SUSPECT AND IS MUCH SLOWER
WITH THE LATEST 00Z MAV AND MET GUIDANCE SETS. THE SLOWER DEWPOINT
RISE MAY LIMIT THE AMOUNT OF DESTABILIZATION THAT OCCURS DURING
THE DAY AS WELL. A FEW HUNDRED J/KG OF CIN COUPLED WITH 700 MB TEMPS
NEAR 10C COULD ALLOW FOR THE FORMATION OF A WEAK CAP ACROSS THE
SOUTHERN PART OF THE REGION. THE MAJORITY OF THE OPERATIONAL
MODELS SUGGEST THE BEST CHANCE OF ANY SHORTWAVE/TRIGGER FOR
CONVECTION TO BE ACROSS THE NORTHERN HALF OF THE REGION SATURDAY
NIGHT, CLOSER TO THE WARM FRONT. WILL MAINTAIN CHANCE POPS ACROSS
THE NORTH AND SLIGHT ACROSS THE SOUTH. ALSO OF INTEREST IS THE
POTENTIAL FOR 30-50 KTS OF 0-6 KM BULK SHEAR AS WELL. IF STORMS
CAN FORM SATURDAY NIGHT THERE IS A POTENTIAL FOR ORGANIZATION AND
A DAMAGING WIND THREAT IF INSTABILITY OF THE MODELED 1000 J/KG OR
SO DOES MATERIALIZE. PW VALUES JUST UNDER 2 INCHES SUGGEST A HEAVY
RAIN THREAT WITH ANY STORMS AS WELL. THE CURRENT SPC OUTLOOK DOES
NOT FEATURE A SEVERE THREAT IN THIS PERIOD LIKELY DUE TO THE
LIMITED COVERAGE OF THE STORMS. AS THE MAIN STORM CHANCE IS LATE SATURDAY
MODELED MOMENTUM TRANSFER SUGGESTS SOME GUSTS FROM 15-20 MPH ARE
POSSIBLE IN THE AFTERNOON ON SATURDAY.

SUNDAY AND SUNDAY NIGHT: CONTINUED WEST-SOUTHWEST FLOW IN THE WARM
SECTOR. GOOD AGREEMENT AMONG THE GFS ENSEMBLES, 12Z ECMWF ENSEMBLE
MEAN AND THE OPERATIONAL GFS AND CMC RUNS THAT THE HIGHEST CHANCE
OF STORMS WILL BE SUNDAY NIGHT IN ASSOCIATION WITH THE STRONGEST VORT
MAX AND ASSOCIATED SHORTWAVE. ON THE OTHER HAND THE NEW 00Z ECMWF
RUN IS SLOWER AND HAS THE MAIN SHOW ON MONDAY. WENT HIGH CHANCE
POPS SUNDAY AFTERNOON AND LOW END LIKELY POPS FOR SUNDAY NIGHT
MORE ALONG THE LINE OF THE CMC AND GFS. FOR QPF STAYED CLOSE TO
THE 21Z SREF. SIMILAR TO SATURDAY ENOUGH BULK SHEAR MAY BE PRESENT
TO ORGANIZE STORMS THAT DO FORM. HOWEVER THE AMOUNT OF
DESTABILIZATION IS IN QUESTION WITH MODELED CAPE VALUES ONLY
AROUND 1000 J/KG AND WILL BE DEPENDENT ON CONVECTION FROM THE
NIGHT BEFORE, PW VALUES NEAR 2 INCHES SUGGEST A CONTINUED HEAVY
RAIN THREAT FROM STORMS. 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.
THE SPC FEATURES THE REGION IN A SLIGHT RISK FOR SEVERE
THUNDERSTORMS DUE TO THE POTENTIAL FOR THE STORMS TO ORGANIZE AND
FOR WIND/HAIL THREATS. THE HWO HAS BEEN UPDATED FOR THIS.

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 ON THE GFS AND CMC. THE NEW 00Z
ECMWF IS SLOWER WITH THE FRONT LEADING TO ANOTHER ROUND OF SHOWERS
AND THUNDER. FOR NOW CONTINUED WITH A MORE PROGRESSIVE IDEA
CENTERING THE CHANCES IN EARLIER PERIODS BUT DID RAISE POPS IN THIS
PERIOD. ANOTHER GUSTY DAY AS ONCE MODELED MOMENTUM TRANSFER SHOWS
POTENTIAL FOR SOME GUSTS OF 15-20 MPH. RAIN MAY KEEP TEMPERATURES
DOWN BUT MID-LEVEL TEMPERATURES SUGGEST ANOTHER HOT DAY.
TEMPERATURES MAY TRY AND SPIKE AHEAD OF THE COLD FRONT AS WELL. MORE
UNCERTAINTY WITH TEMPERATURES IN THIS PERIOD AS RAIN MAY KEEP
TEMPERATURES DOWN BUT A TEMPERATURE SPIKE COULD OCCUR AHEAD OF THE
FRONT.

TUESDAY THROUGH THURSDAY: 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 HIGHS ON TUESDAY AND WEDNESDAY. EVEN WITH THIS
ABNORMALLY COOL AIRMASS THERE IS GOOD AGREEMENT AMONG THE MEX, WPC
AND MODELED TWO METER TEMPERATURES IN THIS PERIOD. WENT ON THE
COOLER END OF GUIDANCE CLOSE TO WPC IN MOST PERIODS. LAPSE RATES MAY
STEEPEN UP TUESDAY AFTERNOON FOR THE FORMATION OF SOME CUMULUS ON
THE BACKSIDE OF THE TROUGH ACROSS THE NORTH WITH THE AID OF
ELEVATION. OTHERWISE EACH DAY LOOKS MOSTLY SUNNY. DEWPOINT
DEPRESSIONS LOOK TO LARGE FOR WEDNESDAY AND THURSDAY FOR MUCH IN THE
WAY OF AFTERNOON CUMULUS.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

18Z TAFS CONTINUE VFR FORECAST.

THIS AFTERNOON SCATTERED VFR CUMULUS WITH THE GREATEST
CONCENTRATION AT NJ TERMINALS AND AIRPORTS.

A SEA AND BAY BREEZE FRONTS ARE FORMING. WE START KACY EAST OF THE
BOUNDARY AND BY 21Z THE FRONTS SHOULD BE IN LOWER NEW CASTLE COUNTY,
SOUTHERN SALEM, GLOUCESTER, CAMDEN, CENTRAL BURLINGTON, SOUTHEAST
MERCER AND MIDDLESEX COUNTIES. AROUND 00Z A WEAKENED VERSION IS
PREDICTED TO JUST ABOUT GET TO THE KPHL AREA AIRPORTS. WIND
SPEEDS EVEN BEHIND THE FRONT SHOULD BE LESS THAN 10 KNOTS.
PRECEDING THE FRONT AND AT OTHER TERMINALS LIGHT WEST TO SOUTHWEST
WINDS WILL PREVAIL.

FOR TONIGHT WINDS WILL BECOME LIGHT AND VARIABLE, SOUTHWEST IF
THERE IS A DIRECTION. THE CIRRUS IN THE TAFS IS MORE FOR THE
SECOND HALF OF THE NIGHT. NO FOG IS EXPECTED TO FORM.

ON SATURDAY. VFR CIG EXPECTED. MOST OF THE REMAINING TAF TIME IT
SHOULD BE AT THE ALTOCU LEVEL. SOUTHWEST WINDS WILL BE INCREASING
AS THE MORNING PROGRESS. WINDS IN THE LAST FORECAST GROUP REPRESENT
MORE OF THE LATTER HALF OF THE MORNING/EARLY AFTERNOON
EXPECTATIONS.

ISOLATED SHOWERS AND THUNDERSTORMS SHOULD OCCUR, BUT COVERAGE FOR NOW
APPEARS TOO SMALL AND LIKELY AFTER 18Z TO INCLUDE IN ANY
TERMINALS. CONFIDENCE TOO LOW FOR KPHL INCLUSION.


OUTLOOK...
SATURDAY NIGHT...BRIEF MVFR AND IFR RESTRICTIONS IN SCATTERED
THUNDERSTORMS. HIGHEST CHANCE FOR RESTRICTIONS IS ON SATURDAY
AFTERNOON AND EVENING FOR RDG, ABE, TTN, AND POINTS NORTH.

SUNDAY THROUGH MONDAY NIGHT...BRIEF MVFR AND IFR RESTRICTIONS IN
THUNDERSTORMS. SOME SOUTHWEST WIND GUSTS AROUND 15 KNOTS POSSIBLE
MONDAY AFTERNOON OUTSIDE OF THUNDERSTORMS.

TUESDAY...VFR.

&&

.MARINE...
WITH HIGH PRES OVER THE REGION TODAY AND MOVG OVER THE CSTL WATERS
TONIGHT, NO MARINE HEADLINES ARE ANTICIPATED THRU THE NR AND
SHORT TERM PDS.

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

SATURDAY NIGHT...SEAS APPROACHING FIVE FEET AT TIMES. WINDS BELOW
SCA CRITERIA.

SUNDAY THROUGH TUESDAY...FOUR FEET SEAS DECREASING LATE IN THE
DAY. HOWEVER SEAS MAY APPROACH FOUR FEET AT OTHER TIMES IN THIS
PERIOD. WINDS BELOW SCA CRITERIA.

&&

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

&&

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






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