Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 080645
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
245 AM EDT WED JUL 8 2015

.SYNOPSIS...
A COLD FRONT IN NORTHWEST PENNSYLVANIA WILL SAG SLOWLY SOUTHEAST
TODAY, REACHING SOUTHERN SECTIONS OF PENNSYLVANIA AND NEW JERSEY
BEFORE STALLING TONIGHT. TWO AREAS OF LOW PRESSURE WILL MOVE EAST
ALONG THE FRONT AND OFF THE NEW JERSEY COAST, ONE EARLY THURSDAY
AND THEN ANOTHER EARLY FRIDAY. THEREAFTER THE FRONT SLIPS SLOWLY
SOUTH OF THE DELMARVA DURING FRIDAY. HIGH PRESSURE WILL BRIEFLY
MOVE INTO THE REGION FOR THE WEEKEND, BEFORE A WARM FRONT MOVES TO
OUR NORTH ON MONDAY. A TROUGH LOOKS TO PERSIST OVER OUR AREA
THROUGH MOST OF NEXT WEEK, AS A RESULT OF A DOMINANT RIDGE OVER
THE MIDWEST.

&&

.NEAR TERM /THROUGH TODAY/...
EARLY TODAY...ITS A FAIR, WARM AND HUMID EARLY SUMMER MORN...MIN
TEMPS 6 TO 12 DEGREES ABOVE NORMAL. STILL A SMALL CHANCE OF
SHOWERS EARLY TODAY FOR THE POCONOS BUT THE LEADING EDGE OF
SHOWERS IN CENTRAL PA HAS BEEN DISSIPATING.

PATCHY FOG EXISTS OVER NW NJ.

TODAY...A LESS THAN AVERAGE CONFIDENCE FORECAST FOR BOTH MAX TEMPS
AND TIMING/EXTENT OF SHOWERS AND HOW MUCH OF IT IS THUNDER.

SHOWERS EITHER ON GOING AT DAYBREAK NEAR AND NORTH OF I-80 OR
REDEVELOP DURING THE MIDDAY/AFTERNOON HOURS OVER E PA AND N OR
CENTRAL NJ.

PWAT 2.25 INCHES DURING THE AFTN AND EVENING ALONG AND SE OF I-95!
YET MLCAPE NOT IMPRESSIVE...ABOUT 800J. 0-6KM BULK SHEAR DECREASES
DURING THE DAY WITH WLY CONVECTIVE STEERING FLOW APPEARING TO SLOW
TO 15 KT BY THIS EVENING, AND NEARLY PARALLEL TO THE SLOW MOVING
FRONT. THIS COULD MEAN NARROW SWATH OF 2-4 INCH RAINFALLS, IF
TRAINING CAN OCCUR OR REOCCUR, ESPECIALLY DELMARVA OR SE PA AND S
NJ.

MAXIMUM TEMPERATURES ARE DEPENDENT ON AMOUNT OF REMAINING SUNSHINE
THROUGH 18Z AND ONSET OF SHOWERS AT ANY LOCATION. FOR NOW, WITH
ABOUT 17-18C AT 850MB TO START THE DAY AND STILL 16-17C AT 18Z...
THINK WE SHOULD NUDGE 90 IN PHL AROUND 17Z-18Z BEFORE ANY FURTHER
RISE IN TEMPS IS PROBLEMATIC WITH THICKENING CLOUD COVER AND
DEVELOPMENT OF SHOWERS. DEWPOINTS AT TIME OF MAX TEMP SHOULD BE
LOW ENOUGH TO PREVENT HEAT INDICES FROM RISING TO ADVISORY THRESHOLD.
STILL IT APPEARS TO BE A HOT AND HUMID DAY VCNTY I-95 SEWD, ESPECIALLY
WITH LESS WIND THAN TUE AFTN.

NOTE: THE 00Z/8 ECMWF IS NOTICEABLY COOLER THAN THE NAM, GFS AND
GGEM 2M TEMPS. THIS LEADS TO LOWERED CONFIDENCE. THE 05Z HRRR,
WHILE BIASED WARM IN ITS 2M TEMPS IS STILL BASICALLY DRY THROUGH
18Z IN THE PHILLY AREA. SO ITS POSSIBLE 90F WILL WORK OKAY.

THE MAX TEMP FCST WAS PRIMARILY A 00Z/8 NAM MOS/2M TEMP BLEND. AGAIN
LESS THAN IDEAL CONFIDENCE AND IF ANYTHING, THIS FCST COULD BE TOO
HOT!

&&

.SHORT TERM /TONIGHT/...
TONIGHT...EVENING CONVECTION PROBABLY DIES OUT THOUGH THERE IS A
CHANCE OF RENEWED SHOWERS/TSTMS TO OUR WEST ADVANCING INTO OUR
AREA OVERNIGHT. THE SFC COOL FRONT SAGS DOWN TO NEAR PHILADELPHIA
AND ATLANTIC CITY BY DAWN THURSDAY. HUMID. PWAT LOWERS .3 TO .4
INCHES OVERNIGHT BUT STILL A JUICY 1.5 TO 2 INCHES S OF I-78 AT
DAYBREAK THURSDAY.

THIS PART OF THE FCST WAS A 50 50 BLEND OF THE 00Z/8 NAM/GFS MOS
GUIDANCE.

CONFIDENCE IS ONLY AVERAGE, AND BELOW AVERAGE REGARDING
POPS/TIMING.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
HEMISPHERIC WAVE GUIDANCE SHOWS DEEP SOUTHWESTERLY FLOW ACROSS THE
EASTERN HALF OF THE U.S. AT THE START OF THE LONGTERM PERIOD. BY THE
WEEKEND THE WAVELENGTH ACROSS THE CONTIGUOUS U.S. BECOMES LONGER
ALLOWING THE SOUTHEAST RIDGING TO RETROGRADE TOWARDS THE CENTRAL
U.S. THIS SETS UP A PSEUDO-HIGH LATITUDE OMEGA BLOCK, WITH OUR
REGION ON THE PERIPHERY OF AN EAST COAST TROUGH. THIS PATTERN LOOKS
TO REMAIN IN PLACE, WHILE LIFTING AND WEAKENING A BIT, GOING INTO
NEXT WORK WEEK, ADDING TO OUR DAILY CHANCES FOR SHOWERS AND
THUNDERSTORMS.

THURSDAY  - FRIDAY NIGHT...THE SLOW SAGGING COLD FRONT THAT
BEGINS TO CROSS THE REGION ON WEDNESDAY LOOKS TO MAKE IT AS FAR
SOUTH AS DELMARVA ON THURSDAY AND REMAIN NEARLY IN PLACE THROUGH
FRIDAY. MULTIPLE WAVES MOVE ALONG THIS BOUNDARY AS IT PRESSES
SOUTHWARD ADDING TO THE INCREASED CHANCES FOR SCATTERED SHOWERS
AND EMBEDDED THUNDER. GUIDANCE TRIES TO ADVECT IN MORE INSTABILITY
FROM THE SOUTH ON THURSDAY AHEAD OF THE FRONT BUT THE TIMING
DOESN`T LOOK LIKE IT OVERLAPS THE FRONTAL PASSAGE. THAT BEING SAID
PWATS WILL STILL BE WELL ABOVE NORMAL, POSSIBLY 2+ INCHES GIVING
US MORE LOCALIZED FLOODING ISSUES...SAME AS IT EVER WAS. WE
CONTINUE WITH THE HEAVY RAIN WORDING IN THE FORECAST THURSDAY
NIGHT INTO FRIDAY MORNING, BUT CONFINE IT TO OUR NORTHERN
HALF...BETTER LIFT/DYNAMICS AND SOME ELEVATED INSTABILITY TO WORK
WITH. AFTER WHAT COULD BE A GREAT LAKES MCS PASSAGE FRIDAY MORNING
ACROSS OUR NORTH, THE FRONT CONTINUES TO SAG SOUTHWARD DURING THE
DAY WITH ISOLATED SHOWERS AND THUNDERSTORMS POSSIBLE ACROSS
DELMARVA...DRYING OUT BEHIND THE FRONT ACROSS THE NORTH. IT SHOULD
BE NOTED THAT FFG ACROSS THE NORTHERN ZONES IS RUNNING QUITE LOW
WITH A LOT OF AREAS ONLY NEEDING 1.5 INCHES IN AN HOUR TO CAUSE
ISSUES...SOMETHING TO WATCH.

SATURDAY...THE AFOREMENTIONED FRONT SHOULD BE FARTHER TO OUR SOUTH
THIS WEEKEND WHILE LARGE SCALE SUBSIDENCE TAKES OVER...THE LONGWAVE
RIDGING RETROGRADING ALL THE WHILE. WE STILL EXPECT SATURDAY TO BE
RAIN FREE BUT THERE COULD BE LINGERING MID-LEVEL ENERGY MOVING BY TO
OUR SOUTHWEST THAT MAY TOUCH OFF A FEW ISOLATED TO SCATTERED SHOWERS
IN OUR EXTREME SOUTHWEST ZONES...HAVE TIME TO BETTER DEFINE THESE
CHANCES IF ANY.

SUNDAY - TUESDAY...WARM FRONT PASSAGE, FROM WHAT WAS ONCE THE COLD
FRONT EARLIER IN THE PERIOD, MOVES BACK TOWARDS THE NORTH ON SUNDAY
NIGHT INTO MONDAY. COLD FRONT THEN NEARS FROM THE NORTHWEST LATE
ON MONDAY INTO TUESDAY AS TROUGHING TAKES BACK OVER AGAIN.
NORTHWEST FLOW ALOFT LOOKS TO PREVAIL AS CENTRAL U.S. RIDGING
AMPLIFIES. THIS MAY SEND SEVERAL SHORTWAVES THROUGH THE REGION
FROM LATE MONDAY ONWARD...NORTHERN PLAINS MCS SEASON.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

PRIOR TO 12Z...VFR CIGS AOA 7000 FT DEVELOP. VSBY MAY LOWER TO
4-6 MI IN HAZE FOG IN A FEW TAF LOCATIONS. LIGHT S-SW WIND. CHANCE
OF SHOWERS TOWARD DAWN NEAR AND N OF I-80 (SHOWERS SEEN ON RADAR
OVER CENTRAL PA AT 0630Z).

WEDNESDAY...VFR CIGS GENERALLY AOA 5000 FT. BRIEF IFR CONDITIONS
IN MAINLY AFTERNOON EVENING SHOWERS AND SCT TSTMS. GRADIENT S-SW
WIND GUST 15 KT, POSSIBLY 20 KT AT 15Z, BUT SOMEWHAT DECREASING
GUSTINESS DURING THE AFTERNOON EXCEPT NEAR TSTMS WHERE GUSTS 30KT
POSSIBLE. CONFIDENCE: AVERAGE

TONIGHT...VFR CIGS WITH MVFR VSBY POSSIBLE. CHANCE OF SHOWERS.
CONFIDENCE: AVERAGE.

OUTLOOK...

THURSDAY...POTENTIAL MVFR AND IFR RESTRICTIONS IN SHOWERS AND
THUNDERSTORMS, HIGHEST CHANCES EACH AFTERNOON AND EVENING. WEST-
SOUTHWEST WIND GUSTS AT OR UNDER 20 KNOTS.

FRIDAY - SATURDAY NIGHT...VFR. WINDS AT OR UNDER 10 KNOTS, MAINLY
NORTHERLY.

SUNDAY...MOSTLY VFR. SOME SCATTERED SHOWERS AND EMBEDDED THUNDER
POSSIBLE.

&&

.MARINE...
NO MARINE HAZARDS FORESEEN ATTM THROUGH TONIGHT, EXCEPTING THE
POSSIBILITY OF MARINE WEATHER STATEMENTS OR SPECIAL MARINE
WARNINGS FOR CONVECTIVE GUSTS 25-35 KT LATE THIS AFTN/EVENING.

OTHERWISE GRADIENT SSW WIND GUSTS 15-20 KT THIS MORNING MAY DECREASE
LATE TODAY FROM NORTH TO SOUTH IN NJ WITH THE APPROACHING COLD FRONT
THEN WINDS ALONG THE NJ COAST SHOULD BECOME SOME SORT OF NLY COMPONENT
OVERNIGHT WEDNESDAY.

OUTLOOK...

SUB-SCA WINDS AND SEAS EXPECTED. ANY WIND GUSTS LOOK TO REMAIN
BELOW 20 KNOTS, MORE NORTHERLY THROUGH SATURDAY NIGHT. SEAS
AROUND FOUR FEET ON WEDNESDAY AND THURSDAY. THE HIGHEST CHANCE OF
THUNDERSTORMS IS WEDNESDAY AFTERNOON AND EVENING THEN AGAIN LATER
THURSDAY.

&&

.RIP CURRENTS...
MAXIMUM WAVE ENERGY SHOULD BE FROM A 3-4 FT, 5-6 SECOND SOUTHERLY
WIND WAVE WITH A 190 DEGREE SURFACE WIND AT 12 KT OFFERING A LOW
RISK FOR THE FORMATION OF DANGEROUS RIP CURRENTS ALONG BOTH THE NJ
AND DE COASTS TODAY. OUTGOING AFTERNOON TIDES WILL LOCALLY ENHANCE
THE RIP CURRENTS BUT THE LACK OF MUCH LONG PERIOD INCOMING SWELL
KEEPS THE RISK GENERALLY LOW. THUNDERSTORMS MAY IMPACT BEACH
ACTIVITIES MID OR LATE AFTERNOON.

&&

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

&&

$$
SYNOPSIS...DRAG
NEAR TERM...DRAG 245
SHORT TERM...DRAG 245
LONG TERM...GAINES/HEAVENER
AVIATION...DRAG/HEAVENER 245
MARINE...DRAG/HEAVENER 245
RIP CURRENTS...245


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