Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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000
FXUS61 KPHI 302006
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
406 PM EDT SAT AUG 30 2014

.SYNOPSIS...
A WARM FRONT WILL LIFT NORTH THROUGH THE AREA TONIGHT. THIS WARM FRONT
IS EXPECTED BECOME QUASI-STATIONARY NEAR THE CANADIAN BORDER SUNDAY
THROUGH TUESDAY...WITH A TROUGH EXTENDING SOUTHWARD TO THE LEE OF
THE APPALACHIANS...BETWEEN BERMUDA HIGH PRESSURE ANCHORED OFFSHORE
AND A SLOW MOVING COLD FRONT IN THE MISSISSIPPI VALLEY. THIS VERY
WEAK COLD FRONT IS PROJECTED MOVE THROUGH THE REGION LATE TUESDAY
INTO EARLY WEDNESDAY...FOLLOWED BY BERMUDA HIGH PRESSURE RETURNING
TO DOMINATE LATER IN THE WEEK. ANOTHER COLD FRONT MAY APPROACH THE
REGION EARLY NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
EXPANSIVE AREA OF STRATOCU ACROSS THE REGION SHOULD BEGIN TO THIN
OUT SOME BY THIS EVENING AS BOUNDARY LAYER HEATING CONTINUES.
SOMETHING RESEMBLING A WARM FRONT, STILL TO OUR SOUTH AND WEST, WILL
GRADUALLY LIFT THROUGH LATER TONIGHT, IF IT DOESN`T WASH OUT
ENTIRELY. NONE-THE-LESS THE AIRMASS MODIFICATION WILL CONTINUE AS
PLANNED AS DEWPOINTS WILL JUMP INTO THE MID TO UPPER-60S IN A LOT OF
SPOTS TONIGHT. STRONGER WARM AIR ADVECTION WILL ALSO TAKE PLACE
ALLOWING A LOW-LEVEL INVERSION TO SET UP. WINDS WILL GRADUALLY
DECREASE TONIGHT, LIGHTENING UP FROM THE SOUTH, TO ALLOW FOR FOG AND
A DECK OF STRATUS TO FORM.

GUIDANCE IS SHOWING SOME ISOLATED SHOWERS TRYING TO WORK THERE WAY
INTO THE REGION LATE TONIGHT ON THE NOSE OF THE BETTER WAA SHOT. WE
DO CARRY SLIGHT CHANCE POPS FOR OUR WESTERN ZONES, BUT THE MODELS
MAY BE PICKING UP ON THE MOISTENING BOUNDARY LAYER AND POTENTIAL FOG
FORMATION WITH LITTLE IN THE WAY OF QPF.

OVERNIGHT LOWS WILL BE SEVERAL DEGREES WARMER THAN THE PAST FEW
MORNINGS. A BLEND OF THE MET/MAV SEEMS REASONABLE AT THIS TIME GIVING
US ABOVE NORMAL LOWS.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH 6 PM SUNDAY/...
CONTINUED AIRMASS MODIFICATION OCCURS A PWATS CLIMB CLOSER TO THE 2
INCH MARK. DEWPOINTS JUMP INTO THE UPPER-60S, POSSIBLY LOW-70S
DURING THE DAY MAKING FOR MUGGY CONDITIONS. TEMPERATURES, UNDER
STRONGER WAA, SHOULD BE ABLE TO WARM INTO THE MID TO UPPER-80S
THOUGH NOT QUITE SURE HOW MUCH THE CLOUD COVER WILL PLAY A FACTOR.
WE EXPECT THE MORNING STRATUS TO LIFT AND BURN OFF WITH A STRONGER
LOW-LEVEL JET MOVING IN OVERHEAD ALLOWING FOR DEEPER MIXING. HIGHER
BASED DECKS ARE EXPECTED IN ADVANCE OF AN APPROACHING MID-LEVEL
SHORTWAVE AND SURFACE TROUGH. THESE TWO FEATURES WILL MORE THAN
LIKELY BE THE CATALYST FOR AFTERNOON AND EVENING CONVECTIVE
INITIATION.

DECENT AMOUNT SHEAR AND BOUNDARY LAYER INSTABILITY WILL BE PRESENT
AND WHEN COMBINED WITH THE ABOVE NORMAL PWATS HEAVY RAIN IS A
POSSIBILITY. THE GOOD THING ABOUT TOMORROW IS THAT THE FLOW SHOULD
BE STRONG ENOUGH TO KEEP THE STORMS MOVING, THE BAD THING IS THAT
WITH THE AVAILABLE INSTABILITY WE COULD SEE NUMEROUS TOWERS SHOOT UP
TO GIVE US SOME STRONG WET-MICROBURSTS LATER IN THE EVENING. MOST OF
THE MESOSCALE MODELS PAINT THIS SCENARIO ACROSS OUR NORTHWESTERN
ZONES, CLOSER TO THE SHORTWAVE PASSAGE. WE WILL CONTINUE TO WATCH
THE DEVELOPMENT FOR ANY LOCALIZED FLOOD AND SEVERE ISSUES.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
SUNDAY NIGHT....BIG CONCERN THROUGH THIS PERIOD WILL BE THE
CONVECTION. THE UPPER LEVEL TROUGH OVER THE UPPER MID WEST NOW
WILL BE LIFTING OVER THE NORTHEAST U.S. BY TOMORROW NIGHT.
HOWEVER, ALL MODELS SHOW THE TROUGH FILLING AS IT LIFTS, WHICH IS
CONSISTENT WITH WHAT WAS OBSERVED WITH THE 12Z SOUNDINGS THIS
MORNING, WHICH SHOWED VERY MARGINAL HEIGHT FALLS AHEAD OF THE
TROUGH AXIS. AS MENTIONED BY THE PREVIOUS SHIFT, PWAT VALUES ARE
EXPECTED TO BE ABOVE NORMAL, NEAR 2 INCHES. HOWEVER, AS MENTIONED
PREVIOUSLY WITH MEAN FLOW OF NEAR OR ABOVE 30 KT...STORM MOTIONS
SHOULD BE RELATIVELY FAST AND AS MENTIONED IN THE PREVIOUS
DISCUSSION, WE STILL HAVE RELATIVELY DRY ANTECEDENT CONDITIONS.
THUS DON`T ANTICIPATE WIDESPREAD ISSUES OUTSIDE OF SOME POOR
DRAINAGE/URBAN NUISANCE FLOODING AT THIS TIME. AS FOR THE SEVERE
THREAT, CAPE VALUES (BOTH SURFACE BASED OR ELEVATED - WHICH MAY BE
MORE REALISTIC FOR THE NIGHT TIME HOURS) COULD BE NEAR OR ABOVE
500 J/KG. AT THE SAME TIME, BULK SHEAR (MOSTLY SPEED SHEAR) COULD
BE NEAR 30KT. THIS COULD BE ENOUGH FOR STRONG OR EVEN MARGINALLY
SEVERE STORMS FOR WINDS, AND POSSIBLY ENOUGH FOR SOME SMALL HAIL.

LABOR DAY...THERE MAY BE A BRIEF BREAK IN THE CONVECTION (OR AT
LEAST MORE LIMITED COVERAGE) AS THE 500MB SHORT WAVE RIDGE AXIS
MOVES OVER. AS IT DOES SO, MEAN FLOW WILL DECREASE, HOWEVER PWAT
VALUES WILL LIKELY ALSO DECREASE AS THE FLOW TURNS MORE WESTERLY.
THUS, THINK THE FLOODING THREAT WILL REMAIN MORE OF A URBAN AND
POOR DRAINAGE THREAT.

TUESDAY INTO WEDNESDAY...EXPECT A LULL IN THE PRECIPITATION
CHANCES BEFORE THE NEXT UPPER LEVEL TROUGH (AT THIS TIME OVER THE
GREAT BASIN REGION) SLIDES EAST, AS DOES THE ASSOCIATED SURFACE
COLD FRONT. GFS AND ECMWF SPED UP THE TIMING OF THE COLD FRONT
WITH THE LATEST RUNS...NOW ARRIVING AS EARLY AS TUESDAY EVENING.
IN THE WAKE OF THE FRONT, EXPECT DRIER AND COOLER WEATHER, THOUGH
TEMPERATURES WILL LIKELY STILL BE SLIGHTLY ABOVE NORMAL.

THURSDAY THROUGH SATURDAY...UPPER LEVEL FLOW TRANSITIONS TO MOSTLY
ZONAL FLOW BY THURSDAY WITH A SURFACE HIGH SETTLING IN THROUGH
FRIDAY. BY SATURDAY THE NEXT UPPER LEVEL TROUGH PROPAGATES EAST
ACROSS SOUTHERN CANADA. THERE IS UNCERTAINTY HOWEVER, GIVEN THE
MOSTLY ZONAL FLOW IF THE ASSOCIATED COLD FRONT WILL DIG AS FAR
SOUTH AS OUR REGION BEFORE FRONTOLYSIS OCCURS. FOR NOW, HAVE A
SLIGHT CHANCE FOR THUNDERSTORMS THROUGH THE WEEKEND GIVEN THE
UNCERTAINTY.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG, KILG,
KMIV, KACY AND SURROUNDING AREAS.

THROUGH LATE EVENING...VFR. STRATOCU BASES WILL REMAIN BETWEEN 3500
TO 5000 FEET. WINDS CONTINUE OUT OF THE SOUTH AND COULD BACK MORE
TOWARDS THE SOUTH-SOUTHWEST AROUND 10 KNOTS.

TONIGHT...VFR TO MVFR, POSSIBLY IFR. WINDS LIGHTEN UP BUT REMAIN
MOSTLY SOUTHERLY. MORE MOISTURE MOVES IN ALLOWING AT LEAST AN MVFR
DECK WITH PATCHY FOG TO DEVELOP. SOME LOCATIONS MAY DROP TO IFR, HAD
SLIGHTLY HIGHER CONFIDENCE AT ILG AND TTN BASED ON SURFACE FLOW AND
CLIMATOLOGY.

TOMORROW...VFR. STRATUS MIXES OUT BY LATE MORNING LEAVING MOSTLY
ALTOCU IN PLACE. MOST SHOWERS AND POTENTIAL THUNDER SHOULD HOLD OFF
UNTIL LATE IN THE PERIOD.

OUTLOOK...
SUNDAY NIGHT INTO MONDAY NIGHT...IFR CONDITIONS EXPECTED WITH
SHOWERS AND THUNDERSTORMS. COVERAGE OF PRECIPITATION DECREASING BY
MONDAY NIGHT.

TUESDAY AND TUESDAY NIGHT...CONDITIONS IMPROVING TO VFR EARLY IN THE
DAY. STILL A SMALL THREAT OF SHOWERS AND THUNDERSTORMS.

WEDNESDAY THROUGH THURSDAY...GENERALLY VFR CONDITIONS EXPECTED.

&&

.MARINE...
SUB-SCA CONDITIONS EXPECTED TONIGHT AND A MAJORITY OF TOMORROW. SEAS
WILL CONTINUE TO BUILD THROUGH SUNDAY UNDER A STRENGTHENING
SOUTHERLY FLOW THAT BEGINS TO BACK TOWARDS THE SOUTHWEST LATER
TOMORROW. THIS COULD POSE SOME ISSUES AROUND THE INLETS WHERE LARGER
SWELLS, CLOSE TO 5 FEET, AND GUSTS AROUND 25 KNOTS MAY
OCCUR...MOSTLY NEARSHORE FOR THE GUSTS. DECIDED THE SETUP WAS TOO
MARGINAL TO WARRANT A SMALL CRAFT AT THIS TIME.

OUTLOOK...
MONDAY NIGHT...WINDS AND SEAS SHOULD REMAIN JUST BELOW SMALL CRAFT
ADVISORY CRITERIA. GUSTIER WINDS POSSIBLE IN THE VICINITY OF
THUNDERSTORMS.

TUESDAY THROUGH THURSDAY...WINDS AND SEAS EXPECTED TO REMAIN WELL
BELOW SCA CRITERIA. HOWEVER, SOME GUSTY WINDS ARE POSSIBLE WITH
THUNDERSTORMS ON TUESDAY.

&&

.RIP CURRENTS...
THERE IS A MODERATE RISK OF DANGEROUS RIP CURRENTS THROUGH THIS
EVENING, AS ENOUGH OF A SWELL COMPONENT IS STILL PRESENT TO ENHANCE
THE FORMATION OF RIP CURRENTS.

&&

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

&&

$$
SYNOPSIS...FRANCK
NEAR TERM...HEAVENER
SHORT TERM...HEAVENER
LONG TERM...JOHNSON
AVIATION...HEAVENER/JOHNSON
MARINE...HEAVENER/JOHNSON
RIP CURRENTS...





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