Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 301937
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
337 PM EDT SAT MAY 30 2015

.SYNOPSIS...
LOW PRESSURE ALONG AN ASSOCIATED COLD FRONT ACROSS THE
OHIO VALLEY WILL CONTINUE MOVING EASTWARD TONIGHT AND INTO OUR
REGION ON SUNDAY. THIS COLD FRONT WILL SLOWLY MOVE ACROSS OUR REGION
EARLY NEXT WEEK. HIGH PRESSURE WILL BUILD SOUTHEASTWARD BEHIND IT
INTO THE REGION FOR THE MIDDLE AND LATER HALF OF NEXT WEEK. THIS
HIGH PRESSURE SYSTEM WILL BE FOLLOWED BY ANOTHER COLD FRONT DROPPING
SOUTHEAST INTO THE REGION BY NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
OUR CWA REMAINS NEAR THE WESTERN PERIPHERY OF AN UPPER-LEVEL RIDGE.
THE SOUTHERLY FLOW AROUND THIS FEATURE WILL CONTINUE TO SUPPLY A
WARM AND MOIST AIRMASS ACROSS OUR REGION. WHILE MUCH OF THE REGION
IS SEEING CUMULUS, SOME THAT ARE SHOWING MORE VERTICAL GROWTH THAN
OTHERS, THE SURFACE FLOW HAS BACKED SOME ALONG THE COAST ALLOWING
FOR LITTLE TO NO CLOUDS AND A COOLING AFFECT. FARTHER INLAND THOUGH,
IT IS DIFFERENT.

SOME SUBTLE SHORT WAVES EMBEDDED IN THE FLOW AROUND THE RIDGE IS
TEAMING UP WITH INSTABILITY AND TERRAIN TO PRODUCE SOME SHOWERS AND
THUNDERSTORMS. THIS IS PROBABLY BEING ENHANCED SOME WEST OF OUR AREA
WHERE A MORE PRONOUNCED SHORT WAVE IS MOVING UP THE OHIO VALLEY AND
TOWARD THE EASTERN GREAT LAKES THIS AFTERNOON. THIS PLACES OUR
WESTERN ZONES IN THE BEST AREA FOR SOME CONVECTION THROUGH PORTIONS
OF THE EVENING. AS A RESULT, THE HIGHEST POPS REMAIN IN THESE AREAS,
THEN THESE DROP OFF TO NON-MENTIONABLE FARTHER EAST. THE FLOW IS ON
THE WEAKER SIDE THEREFORE THE STORM MOTION SHOULD BE SLOW ENOUGH TO
ALLOW FOR LOCALLY HEAVY RAIN UNDER STRONGER CONVECTIVE CORES GIVEN
THE PW VALUES ARE AROUND 1.50 INCHES. THE SHEAR LOOKS TO BE ON THE
WEAK ENOUGH SIDE TO KEEP ORGANIZATION AND STRENGTH IN CHECK,
ALTHOUGH A PULSE STORM COULD CONTAIN LOCALLY GUSTY WINDS. THE CHC OF
SOME SHOWERS OR THUNDER MAY LINGER MAINLY ACROSS OUR NORTHWEST ZONES
THROUGH THE NIGHT, ALTHOUGH THIS WILL DEPEND ON ANY BETTER LARGE
SCALE LIFT AFTER SUNSET AS THE INSTABILITY WANES.

THE AMOUNT OF LOW-LEVEL MOISTURE SHOULD COMBINE WITH AN INVERSION
OVERNIGHT TO PRODUCE SOME LOW CLOUDS. THIS APPEARS TO BE MOST
FOCUSED ACROSS OUR NORTHERN AND WESTERN AREAS GIVEN THE FLOW HAS
VEERED MORE TO THE SOUTHWEST COMPARED TO YESTERDAY. WE MAY SEE MORE
STRATUS THAN FOG, THEREFORE DID NOT INCLUDE FOG ATTM.

AS FOR THE LOW TEMPERATURES, WE USED MAINLY AN EVEN BLEND OF THE
NAM/GFS MOS.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
A SURFACE COLD FRONT WILL GRADUALLY BE SETTLING CLOSER TO OUR AREA.
THIS FEATURE APPEARS TO BE SLOWER AND THEREFORE MUCH LESS OF A CHC
OF CONVECTION ACROSS OUR SOUTHERN ZONES THROUGH THE DAY. THE BETTER
LIFT AND CONVERGENCE IS ACROSS THE NORTHERN AND WESTERN AREAS AND
THIS IS WHERE WE HAVE THE HIGHEST POPS ONCE AGAIN. WE DID TIGHTEN UP
THE POP GRADIENT A BIT FROM NORTHWEST TO SOUTHEAST, HOWEVER THE
HIGHER POPS DO EDGE TO INTERSTATE 95 TOWARD LATE AFTERNOON.

AS THE FRONT NEARS OUR NORTHERN ZONES DURING THE AFTERNOON, SOME
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO OCCUR. THERE IS LESS
CERTAINTY REGARDING THE AMOUNT OF INSTABILITY DURING THE COURSE OF
THE DAY, GIVEN THE PROSPECTS OF LOW CLOUDS TO START THEN CONVECTIVE
TEMPERATURES BEING REACHED TO PROMOTE A DECENT AMOUNT OF CUMULUS
DEVELOPMENT. THE AREAS CLOSER TO THE INCOMING FRONT WILL TEND TO
HAVE SOME INCREASE IN THE SHEAR TO PROMOTE ORGANIZED STORMS AND THIS
COULD POSE A LOCALIZED DAMAGING WIND THREAT. GIVEN THE LOW
CONFIDENCE IN THE CONVECTIVE EVOLUTION/STRENGTH THIS FAR OUT, WE DID
NOT ADD ENHANCED WORDING TO THE FORECAST. LOCALLY VERY HEAVY RAIN
HOWEVER CAN OCCUR GIVEN HIGH PW VALUES AHEAD OF THE FRONT AND ALSO
THE CHC OF SOME TRAINING OF CELLS TO OCCUR. THIS OVERALL LOOKS
LOCALIZED AT THIS POINT HOWEVER WE DID ADD A HEAVY RAIN MENTION TO
THE FAR NORTHERN AND WESTERN AREAS.

AS FOR THE HIGH TEMPERATURES, WE USED A NAM/GFS MOS BLEND WITH SOME
ADJUSTMENTS THEN MADE. SINCE THE FRONTAL BOUNDARY ARRIVAL IS SLOWER,
MUCH OF THE AREA WILL REMAIN IN THE WARM SECTOR AND THEREFORE HIGHS
WERE BUMPED UP SOME ESPECIALLY THE SOUTHERN AREAS /COOLER ALONG THE
COAST/.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...

SUNDAY NIGHT THROUGH TUESDAY NIGHT:

LOW PRESSURE ACROSS THE GREAT LAKES WILL TRACK NORTHEAST OF THE
REGION AS A COLD FRONT BEGINS TO DRIFT SOUTHEAST TOWARD THE REGION.
SHOWERS AND SOME THUNDERSTORMS ARE LIKELY TO BE ONGOING. THE HIGHEST
CONCENTRATION WILL BE ACROSS THE NORTHERN PARTS OF THE REGION CLOSER
TO THE SURFACE LOW AND FRONTAL BOUNDARY. THIS EVENT WILL LIKELY
TRANSITION FROM THE THUNDERSTORMS TO A HEAVY RAIN THREAT. A STRONG
STORM OR TWO CONTAINING GUSTY WINDS AND SMALL HAIL CAN NOT BE RULED
OUT EARLY IN THE EVENING SUNDAY WITH MODEST INSTABILITY 500-1500 J/KG
CAPE AND STEEP LOW LEVEL LAPSE RATES.

INSTABILITY WILL DECREASE HEADING INTO MONDAY WITH THE FRONT SAGGING
SOUTHEAST TOWARD THE REGION. MID-LEVEL FLOW WILL SLOW DOWN
CONSIDERABLY BY MONDAY, ALMOST ALLOWING THE FRONT TO STALL OUT.
SEVERAL FACTORS SUGGEST HEAVY, POTENTIALLY TRAINING SHOWERS AND A
FEW THUNDERSTORMS WILL OCCUR AT TIMES LATE SUNDAY NIGHT INTO
TUESDAY AS MID-LEVEL DISTURBANCES PASS THROUGH THE REGION.
MOISTURE WILL CONTINUE TO STREAM NORTHWARD AHEAD OF THE FRONT
LEADING TO SURGING PW VALUES CLOSE TO 2 INCHES. A TALL SKINNY CAPE
PROFILE IS ALSO MODELED ALONG WITH VERY SLOW STORM MOTIONS. WITH
MORE IN THE WAY OF SHOWERS OVERALL, LOWER INSTABILITY WILL LEAD TO
A MORE ISOLATED THREAT FOR ANY STRONG THUNDERSTORMS. THE HIGHEST
CHANCES FOR RAIN WILL GRADUALLY SHIFT SOUTHEASTWARD MONDAY AND
MONDAY NIGHT AND DEPEND ON THE EXACT TRACK OF PASSING MID- LEVEL
DISTURBANCES. THE FRONTAL BOUNDARY SHOULD BEGIN TO TRANSITION
EASTWARD ON TUESDAY WITH GRADUALLY DECREASING CHANCES OF RAIN FROM
NORTHWEST TO SOUTHEAST.

TOTAL RAINFALL IS LIKELY TO RANGE FROM 1 TO 3 INCHES WITH LOCALLY
HIGHER AMOUNTS. THERE IS SOME VARIABILITY WITHIN THE GEFS, NAEFS AND
OPERATIONAL MODELS ON THE EXACT PLACEMENT OF THE HIGHEST TOTALS DUE
TO VARIABILITY IN THE FEATURES. A GENERAL CONSENSUS AT THIS TIME
YIELDS THE HIGHEST RAINFALL TOTALS ACROSS FAR EASTERN PA, NORTHERN
NJ AND THE EASTERN SHORE OF MD WITH ONLY MODERATE CONFIDENCE IN THIS
PLACEMENT. QPF GRIDS ARE MORE GENERALIZED TO ACCOUNT FOR THE
UNCERTAINTY. HIGH TEMPERATURES ARE ALSO FORECASTED A LITTLE COOLER
THAN SOME OF THE STATISTICAL AND ENSEMBLE GUIDANCE NUMBERS DUE TO
THE RAIN CHANCES AS WELL.

WEDNESDAY THROUGH FRIDAY NIGHT: HIGH PRESSURE BUILDS OVER THEN
PASSES EAST OF THE REGION FOR THE MIDDLE AND LATER HALF OF THE WEEK.
COOL REFRESHING AIRMASS TO START THEN WARMER AND MUGGY BY WEEKS END.
THE GFS AND THE GEFS ARE TRYING TO KEY ON ANOTHER LOW PRESSURE
FEATURE TO OUR SOUTH WHICH COULD RESULT IN ANOTHER SHOWER CHANCE.
HOWEVER, GIVEN THE LACK OF SUPPORT FROM THE OTHER MODELS ATTM
IMPACTS FROM THIS FEATURE ARE NOT THAT LIKELY. FORECAST WILL JUST
FEATURE PARTLY TO MOSTLY SUNNY SKIES.

SATURDAY: ANOTHER COLD FRONT IS LIKELY TO MOVE INTO THE REGION. WARM
AND MORE HUMID CONDITIONS MAY PRECEDE THE FRONT. POTENTIAL IS
PRESENT FOR ENSEMBLE GUIDANCE TO BE A LITTLE LOW WITH HIGH
TEMPERATURES GIVEN SOUTHERLY FLOW AND INCREASING 925 MB
TEMPERATURES. SOME SCATTERED THUNDERSTORMS MAY FORM AHEAD OF THE
FRONT AS WELL. OPTED FOR LOW CHANCE POPS ATTM.

&&

.AVIATION /20Z SATURDAY THROUGH THURSDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

REST OF THIS AFTERNOON...VFR WITH VARYING CLOUD COVERAGE WITH BASES
AROUND 5000 FEET. SOME SHOWERS AND THUNDERSTORMS WILL BE MOST
WIDESPREAD TO OUR WEST, HOWEVER A BRIEF IMPACT MAY AFFECT MAINLY
KRDG AND KABE. SOUTH-SOUTHWEST WINDS 10-15 KNOTS WITH SOME GUSTS TO
20 KNOTS AT TIMES.

TONIGHT...SOME SHOWERS AND THUNDERSTORMS MAINLY NEAR KABE AND KRDG
IN THE EVENING, OTHERWISE VFR. HOWEVER, THERE SHOULD BE
REDEVELOPMENT OF SOME STRATUS AND/OR FOG TOWARD MORNING ESPECIALLY
FOR KTTN, KABE AND KRDG. OUR CONFIDENCE IS LOWER AT THE OTHER
TERMINALS. SOUTHWEST WINDS DIMINISHING TO LESS THAN 10 KNOTS.

SUNDAY...SOME AREAS OF STRATUS OR FOG TO START, OTHERWISE VFR
OVERALL. DURING THE COURSE OF THE DAY, SOME TIMES OF MFVR/IFR DUE TO
SHOWERS AND THUNDERSTORMS MAINLY NORTH AND WEST OF KPHL. SOUTH TO
SOUTHWEST WINDS MAINLY AROUND 10 KNOTS.

OUTLOOK...

SUNDAY NIGHT THROUGH TUESDAY NIGHT: MVFR AND IFR RESTRICTIONS IN
SHOWERS AND SCATTERED THUNDERSTORMS. SOUTH TO SOUTHEAST WINDS UNDER
10 KNOTS THROUGH MONDAY NIGHT THEN EAST TO NORTHEAST UNDER 10 KNOTS
THROUGH TUESDAY NIGHT.

WEDNESDAY THROUGH THURSDAY: VFR. WINDS UNDER 10 KNOTS.

&&

.MARINE...
A SOUTHERLY FLOW WILL BE MAINTAINED THROUGH SUNDAY WELL AHEAD OF A
COLD FRONT. THIS FLOW SHOULD INCREASE AT TIMES, ESPECIALLY NEARSHORE
AND ALSO ACROSS THE NORTHERN COASTAL WATERS HOWEVER WE ARE
ANTICIPATING THE BULK OF THE GUSTS TO REMAIN UNDER 25 KNOTS. THE
SOUTHERLY FLOW WILL MAINTAIN ELEVATED SEAS ON THE COASTAL WATERS,
HOWEVER THESE ARE ANTICIPATED TO BE NO HIGHER THAN 4 FEET OVERALL.
THERE COULD BE SOME FOG OVERNIGHT AND EARLY SUNDAY MORNING
NEARSHORE, HOWEVER WITH THE FLOW MORE FROM THE SOUTHWEST ABOVE THE
SURFACE WE ANTICIPATE IT NOT TO BE WIDESPREAD AND IT WAS NOT
INCLUDED ATTM.

OUTLOOK...

SUNDAY NIGHT THROUGH TUESDAY MORNING: SEAS AROUND FOUR FEET WITH
WIND GUSTS BELOW 20 KNOTS.

TUESDAY AFTERNOON THROUGH THURSDAY: SEAS AROUND FIVE FEET,
DECREASING BY A FOOT OR TWO FROM NORTH TO SOUTH ON THURSDAY. ANY
WIND GUSTS UNDER 20 KNOTS. WAVEWATCH COULD BE TO HIGH IN THIS PERIOD
WITH WAVE HEIGHTS GIVEN THE GFS MODEL HAS MORE IN THE WAY OF LOW
PRESSURE TO OUR SOUTHEAST.
&&

.RIP CURRENTS...
THE RIP CURRENT RISK FOR THE JERSEY SHORE REMAINS AT MODERATE
THROUGH THIS EVENING, DUE TO SOME STRONGER SOUTHERLY NEARSHORE WINDS
COMBINED WITH A LONGER WAVE PERIOD.

&&

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

&&

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


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