Area Forecast Discussion
Issued by NWS State College, PA

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000
FXUS61 KCTP 191514
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1114 AM EDT TUE AUG 19 2014

.SYNOPSIS...
AN UPPER LOW OVR THE W GRT LKS WILL DRIFT SLOWLY SE ACROSS UPSTATE
NY AND NEW ENG BY LATE THIS WEEK. A LARGE SFC HIGH OVR THE CANADIAN
MARITIMES WILL RIDGE SOUTHWARD INTO PA DURING THE UPCOMING WEEKEND
AND EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 8 PM THIS EVENING/...

LOW CLOUDS SLOWLY LIFTING AND MOVING TO THE EAST. RADAR HAS
DETECTED SHOWERS WHICH DEVELOPED ON THE WESTERN EDGE OF THIS CLOUD
SHIELD AND HAS MOVED INTO CLEARFIELD COUNTY. SOME HINTS OF WEAK
CONVECTION IN THE HRRR AND 4KM NAM. USED THESE MODELS TO ADD
TEXTURE TO THE FORECAST SHOWING SHOWERS AND ISOLATED THUNDERSTORMS
DRIFTING ACROSS PENNSYLVANIA THIS MORNING AND AFTERNOON.

TRIED TO KEEP POPS IN CHANCE RANGE AS THERE IS LIMITED
ORGANIZATION TO THE CONVECTION. HOWEVER...3KM HRRR UPDATES FROM
NCEPS EXPERIMENTAL HRRR SHOW DIFFERENT AREAS OF SHOWERS IN CENTRAL
PA ALL AFTERNOON AND NOW IMPLY MORE ORGANIZED THUNDERSTORMS IN
S-SE COUNTIES IN LATE AFTERNOON EVENING. SEE HOW THIS EVOLVES.

SKIES SHOULD SLOWLY GET BETTER DURING DAY CENTRAL AREAS.

&&

.SHORT TERM /8 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...

SREF AND NAM CONTINUE TO SHOW CHANCE TO SLIGHT CHANCE OF SHOWERS
OVERNIGHT. THE SURGE OF CAPE AND PW INTO WESTERN PA IN THE SREF
AND NAM...SIMILAR TO OLDER GEFS/GFS IMPLY SOME MORE ORGANIZED RAIN
POSSIBLE ON WEDNESDAY. USED A BLEND TO GET THE POPS AND THE 12KM
NAM TO ADD SOME TEXTURE TO CONVECTION AND RAIN AREA THAT APPEARS
TO BE POISED TO MOVE WEST TO EAST ACROSS THE REGION WEDNESDAY.

THE SREF POPS/PDF IMPLIES SHOWERS COMING INTO WEST AROUND 1500 UTC
AND MOST OF CENTRAL TWO THIRDS OF REGION BY LATE EVENING. SREF IS
KIND OF OPTIMISTIC SOUTHEAST PA COULD HAVE YET ANOTHER MOSTLY
RAIN FREE DAY WEDNESDAY.

THE KEY FEATURES ARE THE RETROGRADING RIDGE OVER EASTERN CANADA
WHICH IS TAKING THE UMPH OUT OF THE SYSTEMS CUTTING UNDER THIS
FEATURE. IN MOST MODELS THE NEAR 1SD ABOVE NORMAL PW SURGES WEAKEN
AS THE MOVE INTO PA. THUS MORE OPTIMISTIC...SREF-LIKE IN THE WEST
THAN THE EAST WITH RAINFALL AND NOT REALLY CONFIDENT GOING LIKELY.


&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
THURSDAY LOOKS LIKE ANOTHER UNSETTLED DAY...AS UPPER LOW MAKES
IT/S CLOSEST PASS TO PA...TRACKING ACROSS UPSTATE NY. COOL TEMPS
ALOFT...COMBINED WITH DIURNAL HEATING...SHOULD YIELD NUMEROUS SHRA
AND TSRA BY AFTN. HAVE RAISED POPS TO THE LIKELY CATEGORY BASED ON
00Z OPER AND GEFS OUTPUT. SOUTHERLY LL JET AND PLUME OF HIGH
PWATS WILL HAVE PASSED NE OF THE AREA THURSDAY...LIMITING THE
THREAT OF ANY HVY RAINFALL. MDL BLENDED QPF IS IN THE QUARTER TO
HALF INCH RANGE THURSDAY. THE NUMEROUS SHOWERS AND COOLER TEMPS
ALOFT WILL RESULT IN HIGH TEMPS BLW NORMAL FOR AUGUST...WITH
MAXES MAINLY IN THE 70S.

LATEST MED RANGE GUIDANCE POINTING TOWARD DRIER WX FRIDAY INTO
EARLY NEXT WEEK...AS SUBTROPICAL HIGH IS PROGGED TO EDGE TOWARD
THE REGION FROM THE MIDWEST. DAILY RING OF FIRE CONVECTION ON NE
PERIPHERY OF THIS RIDGE WILL THREATEN WESTERN PA DURING THE
FRI-SUN TIME FRAME...WHILE EASTERN PA IS LIKELY TO REMAIN DRY.
DESPITE APPROACH OF UPPER RIDGE...NO BIG WARMUP EXPECTED...AS
LARGE SFC HIGH OVR THE CANADIAN MARITIMES WILL CIRCULATE AN
EASTERLY FLOW INTO CENTRAL PA. THERE MAY BE ISSUE WITH AM LOW
CLOUDS/FOG DUE TO THE EXPECTED MOISTLY SERLY FLOW OVR THE AREA.

&&

.AVIATION /15Z TUESDAY THROUGH SATURDAY/...
VFR CONDITIONS WILL GIVE WAY TO FOG AND LOWERING VSBYS OVERNIGHT
UNDER CLEAR SKIES AND LIGHT WINDS. EXPECT WIDESPREAD MVFR TO IFR
VSBYS AND CIGS TO DEVELOP OVERNIGHT AT MOST CENTRAL AND NORTHERN
AIRFIELDS. HOWEVER...HAVE NOT INCLUDED FOG IN THE LOWER
SUSQUEHANNA TAFS OF KMDT AND KLNS...AS CONFIDENCE OF FORMATION IS
LOWER. IF FOG DOES DEVELOP...LIKELY TO BE IN THE MVFR RANGE AT
THESE LOCATIONS.

CURRENT TIMING OF FOG IS FOR DEVELOPMENT AROUND 07Z IN MOST
LOCATIONS...WITH THE DENSEST FOG BETWEEN 09Z AND 12Z.

AFTER MORNING FOG...EXPECT GENERALLY VFR CONDITIONS. THERE IS A
THREAT FOR SHRA/TSRA...MOST LIKELY IN THE SOUTHWEST AND LEAST
LIKELY IN THE NORTHEAST.

A VERY SLOW APPROACHING UPPER LOW WILL SLOWLY INCREASE CHANCES FOR
DAILY SHOWERS AND POTENTIAL AFTERNOON TSRA FOR THE BALANCE OF THE
WEEK. CURRENTLY...LATER WEDNESDAY AND THURSDAY LOOK LIKE THE
HIGHEST LIKELIHOOD OF PRECIPITATION...WITH SURFACE FRONT CROSSING
THE REGION.

OUTLOOK...

TUE...MORNING FOG...THEN MAINLY VFR...WITH SHRA/TSRA POSSIBLE.
WED-FRI...MORNING FOG CHANCES EACH DAY. OVERALL VFR...BUT
INCREASING CHANCES OF MAINLY AFTERNOON SHRA/TSRA AND ASSOCIATED
RESTRICTIONS.
SAT...MAINLY VFR. STILL CHANCE OF SHRA...BUT DECREASING CHANCES.

&&

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

&&

$$
SYNOPSIS...FITZGERALD
NEAR TERM...GRUMM
SHORT TERM...GRUMM
LONG TERM...FITZGERALD
AVIATION...GRUMM/GARTNER



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