Area Forecast Discussion
Issued by NWS Mt. Holly, NJ

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FXUS61 KPHI 040148
AFDPHI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
948 PM EDT MON AUG 3 2015

.SYNOPSIS...
A COLD FRONT FROM THE GREAT LAKES WILL SLOWLY APPROACH FROM THE
NORTHWEST OVERNIGHT, EVENTUALLY TRACKING THROUGH OUR REGION ON
TUESDAY. THIS FRONT IS FORECAST TO STALL JUST SOUTH OF OUR AREA
THROUGH THE END OF THE WEEK WITH WAVES OF LOW PRESSURE MOVING
ALONG IT. THE FINAL WAVE OF LOW PRESSURE LOOKS TO PASS OFFSHORE
SOUTHEAST OF THE REGION ON SATURDAY. A HIGH PRESSURE SYSTEM FROM
EASTERN CANADA SHOULD THEN BUILD SOUTHWARD ON SUNDAY AND MONDAY.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
A FRONTAL BOUNDARY WILL CONTINUE TO APPROACH OUR REGION FROM THE
NORTHWEST OVERNIGHT.

SCATTERED SHOWERS WITH ISOLATED LIGHTNING STRIKES LINGERED IN THE
PENNSYLVANIA COUNTIES OF SCHUYLKILL, CARBON AND BERKS, AS WELL AS
IN THE LEHIGH VALLEY AROUND 930 PM. AS THE ATMOSPHERE CONTINUES TO
BECOME MORE STABLE, THE SHOWERS ARE ANTICIPATED TO DIMINISH, MOST
LIKELY BEFORE MIDNIGHT.

MEANWHILE, IT WAS APPEARING LESS PROBABLE THAT THE CONVECTION IN
WESTERN PENNSYLVANIA THIS EVENING WILL REACH OUR FORECAST AREA
WITH CONDITIONS BECOMING INCREASINGLY STABLE OVER THE SUSQUEHANNA
RIVER VALLEY, AS WELL.

THE SKY COVER SHOULD FAVOR PARTLY CLOUDY DURING THE NIGHT WITH A
LIGHT SOUTHWESTERLY SURFACE FLOW. MINIMUM TEMPERATURES ARE
FORECAST TO BE MOSTLY IN THE UPPER 60S AND THE LOWER 70S IN OUR
REGION.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH 6 PM TUESDAY/...
FRONT GETS HUNG UP ALONG THE COAST TOMORROW. WITH SOME ADDITIONAL
MOISTURE (VS. TODAY) POOLING NEAR THE FRONT AND A SHORTWAVE IN THE
AREA, THE THINKING IS THAT SHOWERS AND THUNDERSTORMS COULD BE MORE
NUMEROUS TOMORROW ACROSS THE EASTERN ZONES. THERE`S A SIGNIFICANT
DIFFERENCE BETWEEN THE NAM AND GFS WITH THE NAM MUCH FURTHER WEST
WITH PRECIP. I`VE CHOSEN TO GO CLOSER TO THE GFS WITH SUPPORT FROM
STAT GUIDANCE.

TEMPS TOMORROW, OVERALL, SHOULD BE A COUPLE DEGREES COOLER THAN
TODAY`S HIGH. FORECASTING 90 FOR PHILLY.

WINDS WILL BE A BIT MORE WESTERLY TOMORROW AFTERNOON WITH SIMILAR
GUSTS VS. TODAY.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
IN A MODEL INITIALIZATION FLIP FROM THE WEEKEND, THE WRF/NAM
INITIALIZED THE 500MB PATTERN BETTER THAN THE GFS OR ECMWF IN THE
WESTERN CONUS, WHILE IN ERN NOAM THE GFS LOOKED BETTER. THE GFS
LOOKED CLOSER AT 850 MB AND 925MB. DP/DTING THE INITIALIZATION
OVER THE PAST 24 HOURS, THE RIDGING IN MONTANA AND IDAHO IS
STRONGER AND DOWN THE ROAD THIS IS LEADING TO A MORE BIFURCATED
SOLUTION TO HOW THE ENERGY ROUNDS THIS RIDGE, THUS THERE IS NO
DECREASE IN UNCERTAINTY WITH THIS SOUNDING RUN. THE GFS WAS NOT
USED BECAUSE OF ITS WEAKER WESTERN CONUS INITIALIZATION AND POOR
RUN TO RUN CONTINUITY. GEFS MEAN WITH THE WAVE OF LOW PRESSURE IS
FARTHER SOUTH AND THEN A FASTER EXIT ON SATURDAY. OUR FORECAST IS
CLOSEST TO A ECMWF/CAN GGEM/MF-ARPEGE BLEND. IT SHOULD BE NOTED
THAT THE UKMET HAS TRENDED SOUTHWARD WITH A MUCH WEAKER LOW WHILE
THE NOGAPS AND JMA HAVE GONE BACK TO NOT HAVING ANY PCPN REACH OUR
CWA UNTIL SATURDAY.

SO THE ACTIVE MIDDLE STRETCH OF THE LONG TERM CONTINUES WITH
TEMPERATURES CLOSER TO THE NORMAL. THE POTENTIAL REMAINS FOR A
SOAKING RAIN CENTERED AROUND FRIDAY, ALTHOUGH THERE REMAINS
UNCERTAINTIES AS TO THE IMPACT WITHIN OUR CWA. LAST NIGHT`S NAEFS
ENSEMBLE MEAN CONTINUE TO SHOW AN ANOMALOUSLY STRONG SFC LOW
PRESSURE SYSTEM FOR EARLY AUGUST WITH A FIVE YEAR RETURN PERIOD
AND SD OF BETWEEN 2 AND 3 AS IT CROSSES THE CENTRAL APPALACHIANS.

THE LACK OF THE RUN TO RUN CONTINUITY REMAINS. THE WAY THE MODELS
RESOLVE CONVECTIVE SYSTEMS THAT WILL DEVELOP ACROSS THE MIDWEST
AND UPPER MISSISSIPPI VALLEY AS THE LOWS MOVES EAST IS MAINLY WHY.
THE MORE ROBUST "FEEDBACK" LENDS TO STRONGER AND FARTHER NORTH
LOWS, WHILE MODELS WITH LESS MCV BULLSEYES HAVE WEAKER AND MORE
SUPPRESSED SOLUTIONS. IT REMAINS HARD TO SEPARATE THE TRUE MCS(S)
FROM PROLONGED FEEDBACK HANGOVERS. LIKELY THIS WILL BE THE CASE
INTO WEDNESDAY AS THE CONVECTION THAT DAY IS THE CAUSE OF MOST OF
THE MODELING HEARTBURN.

TUESDAY NIGHT, THE MODEL TIMING HAS SLOWED IN MOVING THE COLD
FRONT OFFSHORE AND WE MAINTAIN LOW POPS SOUTHEAST PART OF OUR CWA
FOR THUNDERSTORMS. GIVEN HOW DRIER AIR IS MOVING, THE MORE ROBUST
STORMS SHOULD BE DONE BY THIS TIME PERIOD. WE ARE EITHER AT OR
SLIGHTLY ABOVE STAT GUIDANCE FOR MINS GIVEN THE SLOWER MODELING
TREND.

WEDNESDAY, REMAINS POPLESS AS HIGH PRESSURE BUILDS INTO THE
REGION. THE GFS IS STANDING ALONE WITH STGR CAA AND OVERALL
STRONGER SFC WINDS. IT ALSO STANDS ALONE WITH CHANNELIZED VORT MAX
PCPN GETTING INTO THE NORTHERN PART OF OUR CWA. GIVEN THE DP/DT
TREND, GOING FASTER DOES NOT SEEM TO HAVE MUCH CORROBORATION. WE
ARE CLOSER TO A NON-GFS SOLUTION AND NAM MOS FOR HIGH TEMPS. ALSO
NO POPS. BUT, CONVECTIVE TEMPS SHOULD BE REACHED NORTH AND SOME
POPCORN TO MAYBE EVEN CIG CU LIKELY. WHILE IT WILL BE DRIER, NOT
OUT OF THE QUESTION OF A COUPLE OF MORE 90S IN THE EASTERN/COASTAL
PART OF OUR CWA.

WEDNESDAY NIGHT, DRY, AS THIS IS ONE FORECAST PERIOD ALL OF THE
MODELS AGREE UPON. WITH HIGH PRESSURE OVER THE AREA, COMFORTABLE
STAT GUIDANCE MINS LOOK REASONABLE.

THURSDAY, POPS WERE MOVED BACK APPROXIMATELY 12 HOURS. TOO LATE
IN ITS FORECAST CYCLE TO HAVE CONFIDENCE IN THE WRF/NAM TIMING,
BUT MANY OF THE MODELS DO NOT HAVE ANY MEASURABLE AT ALL THURSDAY
DAY BASED ON THE MORE ROUNDABOUT APPROACH FOR THE SHORT WAVES.
BECAUSE OF THE DRIER TRENDING, WE WENT ABOVE STAT GUIDANCE FOR MAX
TEMPS.

THURSDAY NIGHT THROUGH FRIDAY NIGHT THERE UNFORTUNATELY REMAINS
UNCERTAINTY AS TO THE EVOLUTION OF THE SYSTEM, BUT THE SYNOPTIC
SCALE SET-UP STILL POINTS TO HEAVY RAIN, EVEN IF IT DOES NOT
NECESSARILY OCCUR OR AFFECT OUR CWA THE MOST. THE HEAVY RAIN WILL
BE TIED TO CONVECTION AND THUS HOW UNSTABLE ALOFT IT BECOMES
WITHIN OUR CWA WILL DETERMINE THE FINAL OUTCOME. HIGHEST POPS ARE
THURSDAY NIGHT AND FRIDAY WITH THUNDER EMPHASIZED MORE FOR THE
SOUTHERN PART OF OUR CWA. COME FRIDAY NIGHT THE PREDICTED
INSTABILITY (REALLY LACK THEREOF) ALOFT DOES NOT SUBSTANTIATE THE
ECMWF`S PCPN/QPF SOLUTION AND WAS NOT USED. THIS DOES NOT MEAN
HEAVIER RAIN COULD NOT HAPPEN EARLIER. MAX TEMPS MAY VERY WELL BE
OVERSTATED ON FRIDAY IF THIS TIMING HOLDS.

BECAUSE OF TIMING DISCREPANCIES WE KEPT IN A LOW CHANCE FOR
PRECIPITATION ON SATURDAY. AFTER ABOVE, THE END OF THE LONG TERM
APPEARS QUIET AS HIGH PRESSURE NOSES ITS WAY SOUTHWARD FROM CANADA
AND THE FRONTAL BOUNDARY AND LOW PRESSURE SYSTEMS MOVE OFFSHORE.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
THE FOLLOWING DISCUSSION IS FOR KPHL, KPNE, KTTN, KABE, KRDG,
KILG, KMIV, KACY AND SURROUNDING AREAS.

THE SHOWERS AROUND KRDG AND KABE AT 0130Z WILL CONTINUE TO
DIMINISH. WE ARE EXPECTING THE SHOWERS AND THUNDERSTORMS THAT WERE
IN WESTERN PENNSYLVANIA THIS EVENING TO FALL APART AS WELL BEFORE
REACHING OUR TAF SITES.

WERE ARE FORECASTING MAINLY VFR CONDITIONS THROUGH THE TAF
PERIOD. WE HAVE INDICATED SOME MVFR VISIBILITY RESTRICTIONS AT
KRDG AROUND DAYBREAK DUE TO THE MOISTURE THAT WAS INTRODUCED BY
THIS EVENING`S RAINFALL IN THAT AREA.

ISOLATED SHOWERS AND THUNDERSTORMS REMAIN POSSIBLE FOR TUESDAY
AFTERNOON. THE MOST PROBABLE AREA FOR PRECIPITATION IS AROUND KMIV
AND KACY SO WE HAVE INCLUDED A PROB30 GROUP IN THOSE TAFS.

A LIGHT SOUTHWEST SURFACE FLOW OVERNIGHT SHOULD BEGIN TO FAVOR
THE WEST SOUTHWEST ON TUESDAY. WIND SPEEDS ARE FORECAST TO
INCREASE AROUND 10 KNOTS ON TUESDAY WITH GUSTS IN THE UPPER TEENS.

OUTLOOK...
TUESDAY NIGHT...MOSTLY VFR CONDITIONS. ISOLATED TO PERHAPS
SCATTERED SHWRS/TSTORMS ARE POSSIBLE VERY EARLY SOUTHEASTERN
TERMINALS.

WEDNESDAY AND WEDNESDAY NIGHT...MAINLY VFR CONDITIONS.

THURSDAY THROUGH FRIDAY NIGHT...MVFR CONDITIONS DURING
SHWRS/TSTORMS, WITH SOME IFR CONDITIONS POSSIBLE. WHILE CONFIDENCE
OF OCCURRENCE IS INCREASING, TIMING CONFIDENCE REMAINS LOW.

SATURDAY...PREDOMINATELY VFR CONDITIONS EXPECTED TO RETURN AS
SHOWER FREQUENCY DIMINISHES.

&&

.MARINE...
WILL KEEP THE SMALL CRAFT ADVISORY HEADLINES IN PLACE TONIGHT FOR
THE OCEAN WATERS AND EXTEND THEM THROUGH TOMORROW. GUSTS TO 25 KTS
CAN BE EXPECTED ALONG WITH SEAS IN THE 4 TO 6 FT RANGE. WAVEWATCH
NUMBERS WERE HIGHER AND WERE TRIMMED.

IN DELAWARE BAY, WE`LL TOP THE WIND GUSTS OUT AT 20 KTS (SUB
SMALL CRAFT).

OUTLOOK...
TUESDAY NIGHT...SMALL CRAFT ADVISORY CONDITIONS FOR SEAS ON THE
OCEAN MIGHT LAST INTO THE EVENING. CONFIDENCE TOO LOW TO EXTEND.

WEDNESDAY THROUGH THURSDAY...SUB-ADVISORY CONDITIONS ARE
EXPECTED.

THURSDAY NIGHT THROUGH FRIDAY NIGHT...MOSTLY SUB-SCA CONDITIONS;
HOWEVER, A STALLED FRONT AND A WAVE OF LOW PRESSURE MOVING ALONG
IT COULD ENHANCE SEAS AND/OR WINDS FOR THE COASTAL WATERS, MAKING
SCA CONDITIONS POSSIBLE.

SATURDAY...SUB SMALL CRAFT ADVISORY CONDITIONS EXPECTED TO
RETURN. THIS IS BASED ON TIMING OF WAVES OF LOW PRESSURE CLOSE,
CONFIDENCE AT THIS JUNCTURE IS LESS THAN AVERAGE.

&&

.RIP CURRENTS...
THERE IS A MODERATE RISK FOR THE FORMATION OF DANGEROUS RIP
CURRENTS ON TUESDAY ALONG THE NEW JERSEY SHORE AND AT THE DELAWARE
BEACHES. SEAS HAVE CONTINUED TO BUILD IN THE STIFF SOUTHERLY FLOW.
WAVE HEIGHTS IN THE SURF ZONE WILL BE UP TO 4 OR 5 FEET.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT TUESDAY FOR ANZ450>455.

&&

$$

SYNOPSIS...GIGI/KLINE
NEAR TERM...IOVINO
SHORT TERM...KRUZDLO
LONG TERM...GIGI
AVIATION...GIGI/IOVINO/KLINE
MARINE...GIGI/KLINE/KRUZDLO
RIP CURRENTS...IOVINO



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