Area Forecast Discussion
Issued by NWS State College, PA

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000
FXUS61 KCTP 011943
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
343 PM EDT MON SEP 1 2014

.SYNOPSIS...
WARM AND HUMID CONDITIONS WILL CONTINUE INTO TUESDAY UNTIL A COLD
FRONTAL PASSAGE BRINGS DRIER AND SLIGHTLY COOLER AIR TO CENTRAL
PENNSYLVANIA THROUGH MID WEEK. HUMIDITY WILL RETURN TOWARD THE
END OF THE WEEK AHEAD OF THE NEXT FRONTAL SYSTEM THAT WILL BRING
THE CHANCE OF RAIN FOR THE UPCOMING WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
18Z...RADAR LOOP INDICATES CONVECTIVE PCPN IS STARTING TO INCREASE
IN CVRG OVER THE LAST 30 MINUTES OVER THE SRN 1/3 OF THE CWA WHERE
THE RAP SHOWS THE HIGHEST CAPE IN PA. EVEN BETTER INSTABILITY CAN
BE FOUND SOUTH OF THE MASON DIXON LINE NEAR THE I95 CORRIDOR WHERE
THE FIRST LTG STRIKE OF THE AFTN HAS BEEN DETECTED. HIGHEST POPS
/30-40%/ HAVE BEEN PAINTED OVER THE SRN TIER ZONES THRU THE EARLY
EVENING HOURS. FURTHER TO THE NORTH...WEAK LG SCALE FORCING
COUPLED WITH MARGINAL INSTABILITY /HINDERED BY CLOUD COVER/ AND
VERY MOIST/HUMID AIRMASS CONTINUES TO SUPPORT IDEA OF MAINLY ISOLD
SHOWERS. MESO MDL GUIDANCE SHOWS EVE STORMS EVENTUALLY DISSIPATING
AFTER DARK WITH THE LOSS OF HEATING. UPSTREAM STORMS OVER THE GRT
LWR MI/OH VLY SHOULD ALSO EXHIBIT A CONSIDERABLE WEAKENING TREND
AS THE EVOLVE EWD AND MAY SURVIVE INTO WRN PA LATE TNGT.

MAIN FOCUS WILL SHIFT TO THE WEST TONIGHT AS A WELL-DEFINED COLD
FRONT APPROACHES THE AREA FROM THE N/W. HIGHEST POPS /40-50%/
WILL BE OVER THE FAR NW MTNS BASED ON MULTI-MODEL ENSEMBLE CONSENSUS
QPF. IT WILL BE MUGGY WITH LOWS 65-70F. LGT WINDS AND HI DEWPOINTS
ALONG WITH SOME PARTIAL CLEARING FAVORS SOME LOW CLOUDS/FOG.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
A RELATIVELY LOW AMPLITUDE SHORTWAVE TROUGH WILL SLIDE EWD FROM
THE GREAT LAKES/MIDWEST INTO NRN NEW ENGLAND BY THE END OF THE
PERIOD. THIS FEATURE WILL DRIVE A WELL-DEFINED COLD FRONT /WITH
SHARP MSTR-PW GRADIENT/ SEWD FROM THE LWR LKS/OH VLY ACRS THE
N-CNTRL APPALACHIANS. A CONDITIONAL RISK FOR STRONG TO ISOLATED
SEVERE STORMS WILL EXIST FROM LATE TUE MORNING THROUGH THE
AFTERNOON WITH THE PRIMARY POTNL TSTM HAZARD BEING DAMAGING
WINDS.

CLOUD COVER FROM UPSTREAM CONVECTION LKLY ONGOING AT 12Z ALONG
WITH RESIDUAL OVERNIGHT LOW STRATUS/FOG SHOULD ACT TO LIMIT
DESTABILIZATION EARLY TOMORROW. ALTHOUGH 700-500MB LAPSE RATES
WILL GENERALLY REMAIN WEAK TO POOR...THE MODELS SHOW A BELT OF
STRONGER WESTERLY MID-LVL FLOW AND DEEP LYR SHEAR. THIS SHOULD
HELP TO SUPPORT AN INCREASE IN CONVECTIVE PCPN/INTENSITY AS
RENEWED DEVELOPMENT OCCURS ALONG OUTFLOWS/DIFFERENTIAL HEATING
ZONES BY LATE MORNING INTO THE AFTERNOON...WITH SOME ORGANIZATION
INTO LINE SEGMENTS/CLUSTERS. THIS SHOULD YIELD AT LEAST AN ISOLD
DMGG WIND THREAT...WARRANTING AN UPGRADE BY SPC TO A CATEGORICAL
/SLGT/ RISK DESIGNATION. THIS HAS BEEN REFLECTED IN AN UPDATED
HWO.

EARLY CLOUDS SHOULD BREAK FOR A WARM AND HUMID DAY WITH FCST
HIGHS EXPECTED TO RANGE FROM THE MID 70S OVER THE NW TO NEAR 90
OVER THE LOWER SUSQ VLY. THE SECOND HALF OF THE PERIOD ESPECIALLY
AFTER MIDNIGHT SHOULD FEATURE A COOLER/DRYING TREND BEHIND THE
FRONT WITH PWS FALLING AOB NORMAL BY 12Z WED.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
COLD FRONT EXITING TO THE EAST TUE NIGHT ALONG WITH NORTHWEST
FLOW AROUND BUILDING HIGH PRESSURE AREA OVER OHIO VALLEY WILL
BRING A TRANSITION TO A NOTICABLY DRIER AIRMASS FOR MIDWEEK.
DAYTIME HIGHS WILL REMAIN SLIGHTLY ABOVE NORMAL...BUT LOWER
DEWPOINTS WILL MAKE IT FEEL MORE COMFORTABLE. OVERNIGHT LOWS WED
NIGHT WILL DIP TO NEAR 50F IN THE NORTHERN MTNS TO AROUND 60F IN
THE SE.

THE HIGH WILL MOVE OFF THE EAST COAST THU INTO FRI...ALLOWING MORE
HUMID AIR TO BEGIN RETURNING TO THE REGION. A SURFACE LOW SLIDES
FROM THE NORTHERN PLAINS ACROSS THE GREAT LAKES AND LIFTING INTO
S CANADA ON FRI...DRAGGING A COLD FRONT ALONG BEHIND. AS THIS
FRONT APPROACHES...AN AREA OF HIGHER PWATS /1-2"/ SURGES INTO THE
OHIO VALLEY...AND THEN INTO PA FRI NIGHT INTO SAT. AT SAME TIME A
BROAD UPPER TROUGH SAGS SOUTHWARD. THIS WILL BRING ELEVATED
CHANCES FOR SHOWERS/TSTMS STARTING FRI NIGHT IN THE NW AND
SPREADING AREAWIDE ON SAT.

BEHIND THE FRONT...AIRMASS CHANGE WILL USHER IN MUCH COOLER AND
DRIER AIR FOR LATE WEEKEND INTO EARLY NEXT WEEK. HIGHS WILL FALL
BACK ABOUT 10F...RANGING FROM THE UPPER 60S TO MID 70S. AS LARGE
HIGH PRESSURE AREA TRACKS ACROSS NEW ENGLAND...MORNING LOWS SHOULD
DIP WELL INTO THE 40S ACROSS THE NORTHERN MTNS...AND IN THE LOWER
TO MID 50S ACROSS THE SOUTH.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
18Z...CIGS/VISBYS HAVE IMPROVED TO VFR OR MVFR AS EXPECTED.
HOWEVER DESPITE A GENERAL INCREASE IN SHOWER ACTIVITY THERE IS
STILL LOW CONFIDENCE IN POINT TERMINAL IMPACTS. EVOLUTION OF
CONVECTIVE ACTIVITY AND COLLOCATION OF BEST INSTABILITY SUGGESTS
THE SRN TAFS HAVE THE BEST CHC TO SEE SCT SHOWERS OR A BRIEF TSRA
DOWNPOUR. HAVE ADDED SOME 1HR TEMPS THRU 19Z WITH SHOWERS MOVG
THRU AOO/UNV.

OTHER CONCERN WILL BE CLOUD TRENDS OVERNIGHT WITH MOIST AIRMASS
LKLY PROMOTING ANOTHER PERIOD OF LOW CIGS/FOG INTO TUE MORNING. A
COLD FRONT MOVG EWD THRU THE MIDWEST WILL ALSO BRING THE CHC FOR
SOME SHOWERS TO REACH THE NW 1/4 TO 1/3 OF THE AIRSPACE BY
EARLY TUE MORNING. THIS FRONT WILL BE A FOCUS FOR SCT-NMRS
SHWRS/TSTMS TUES AFTN-EVE AS IT MOVES SEWD ACRS CENTRAL PA. THE
RECENT GUIDANCE SUGGESTS A SLIGHTLY HIGHER PROBABILITY FOR LCL
SVR STORMS AND AT LEAST AN ISOLD THREAT FOR DAMAGING TSTM WIND
GUSTS.

OUTLOOK...
WED-THU...PATCHY AM FOG...OTHERWISE VFR.
FRI...MAINLY VFR. CHC OF PM TSTMS WEST.
SAT...VFR/MVFR WITH SCT SHWRS/TSTMS ASSOCD WITH COLD FROPA.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

$$
SYNOPSIS...STEINBUGL
NEAR TERM...STEINBUGL
SHORT TERM...STEINBUGL
LONG TERM...RXR
AVIATION...STEINBUGL



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