Area Forecast Discussion
Issued by NWS State College, PA

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000
FXUS61 KCTP 271058
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
658 AM EDT WED AUG 27 2014

.SYNOPSIS...
A COLD FRONT WILL MOVE ACROSS THE REGION TODAY AND PROVIDE A
FOCUS FOR THUNDERSTORMS. HIGH PRESSURE WILL ARRIVE BEHIND THE
FRONT AND BRING DRY WEATHER TO THE AREA THROUGH THE END OF THE
WEEK. ABOVE NORMAL TEMPERATURES AND INCREASINGLY HUMID CONDITIONS
ARE FORECAST OVER THE LABOR DAY HOLIDAY WEEKEND AND INTO THE FIRST
WEEK OF SEPTEMBER.

&&

.NEAR TERM /THROUGH TONIGHT/...
PATCHY FOG IN THE RIVER/STREAM VALLEYS OF SCENTRL/SERN PA WILL
ERODE SHORTLY AFTER SUNRISE WITH LCL VISBYS IMPROVING BY 14Z.
CLOUDS ARE INCREASING OVER THE NW MTNS IN ADVANCE OF SFC COLD
FRONT SHIFTING SEWD FROM THE LAKE ERIE SHORELINE.

A LOW AMPLITUDE UPPER TROUGH OVER THE GREAT LAKES REGION THIS
MORNING WILL TRANSLATE EWD INTO THE NORTHEAST STATES TONIGHT AND
MOVE OFFSHORE DURING THE D2 PERIOD. AT THE SFC...A COLD FRONT
ANALYZED FROM THE ST. LAWRENCE VLY SWWD BACK ACRS THE LWR LKS
WILL PUSH SEWD ACRS CENTRAL PA THIS AFTN BEFORE SHIFTING SOUTH OF
THE MASON DIXON LINE AFTER 00Z. THE GLOBAL MODELS ARE WELL
CLUSTERED WITH THE UPPER TROUGH AND ASSOCIATED COLD FRONT CROSSING
THE NORTHEAST...WITH A NON-NAM CONSENSUS SOLUTION PREFERRED BY WPC
AS IT APPEARS TO BE STRONGER ALOFT AND A TAD SLOWER WITH THE
ADVANCE OF THE SFC FRONT.

THE MAIN FCST CONCERN IN THE NEAR TERM IS THE POTENTIAL FOR
STRONG TO LOCALLY SVR STORMS THIS AFTN. MODELS ADVECT RICH BLYR
MSTR EWD FROM THE OH VLY INTO CENTRAL PA IN ADVANCE OF THE SFC
COLD FRONT...WITH 60-65F DEWPOINTS PROGGED BY THE CONSENSUS
GUIDANCE. THE NAM IS LKLY TOO MOIST WITH LOW 70S DEWPOINTS.
STRONG HEATING AND DESTABILIZATION WILL LEAD TO MU CAPES IN
EXCESS OF 1000 J/KG ALONG A NARROW CORRIDOR PRECEDING THE COLD
FRONT. THE LOW-MID LVL BACKGROUND WIND FIELDS WILL NOT BE
PARTICULARLY STRONG...AND THE BEST DEEP SHEAR LAGS THE FRONT.
HOWEVER...A FEW CELLS CAPABLE OF PRODUCING SMALL TO MARGINALLY
SEVERE HAIL AND LOCALLY STRONG TO DMGG WIND GUSTS WILL BE POSSIBLE
GIVEN COMBO OF "SUFFICIENT" SHEAR AND DECENT INSTABILITY. THE D1
SPC OUTLOOK PLACES THE ERN ZONES IN THE CATEGORICAL SEE TEXT WITH
5% SVR PROBS BUT COULD SEE AN ISOLD SVR STORM FURTHER WEST ACROSS
S-CENTRAL PA TO THE LAUREL HIGHLANDS. CONVECTIVE ACTIVITY SHOULD
WEAKEN QUICKLY WITH THE LOSS OF DAYTIME HEATING AND EVENTUALLY
DISSIPATE/SHIFT S-SEWD AFTER MIDNIGHT.

AFTERNOON TEMPS WILL APPROACH 90F FROM THE SCNTRL RIDGE/VALLEY
REGION INTO THE LWR SUSQ VLY...WITH UPPER 70S TO LOW 80S COMMON
IN THE NW/NCNTRL HIGH TERRAIN.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
HIGH PRESSURE AND MUCH DRIER AIR WITH LOW/COMFORTABLE HUMIDITY
WILL OVERSPREAD THE AREA ON THURSDAY. ENS DATA SHOWS TEMPS ALOFT
SLIGHTLY BLW NORMAL OVER NRN/NERN PA WHICH SHOULD PROMOTE AFTN
CU/SC CLOUDS. TEMPS RANGE FROM AROUND 70F IN THE NW TO 80F IN THE
SE. THU NGT LOOKS SEASONABLY COOL WITH VALLEY FOG PROBABLE UNDER
SFC RIDGE WITH M/CLR SKIES AND NEARLY CALM WINDS. WAA CLOUDS MAY
IMPACT MIN TEMP FCST BUT FOR NOW SEE NO REASON TO DEVIATE FROM
CONSENSUS GUIDANCE.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
MEDIUM RANGE FLOW PATTERN ACRS THE CONUS WILL FEATURE TROUGHING
IN THE WEST AND FAIRLY HIGH HEIGHTS FCST TO PREVAIL OVER THE EAST
(FOR A CHANGE) SUPPORTED BY SUBTROPICAL RIDGE ANCHORED OVER THE
SOUTHEAST. HIGH PRESSURE CENTERED OVER UPSTATE NY AT THE START OF
THE PERIOD WILL MOVE OFF THE NRN NEW ENGLAND COAST ON SATURDAY AS
TODAYS FRONTAL BOUNDARY PIVOTS BACK NWD AS A WARM FRONT...IN
RESPONSE TO SHORTWAVE/SFC WAVE FCST TO TRACK NEWD FROM THE ERN
PLAINS/MS VLY. OVER THE PAST 12-24 HOURS THE LATEST GUIDANCE HAS
TRENDED NWD WITH SFC LOW TRACKS THRU THE GREAT LAKES AROUND D4/SUN
AND WITH LEADING FRONTAL BOUNDARY WHICH IS NOW PROGGED BY WPC TO
STAY NORTH OF PA. A MORE DEFINED COLD FRONT SHOULD APPROACH THE
AREA BY THE MIDDLE OF NEXT WEEK.

A RATHER MOIST RETURN FLOW AROUND SOUTHEAST RIDGE AND AHEAD MID
LVL SHORTWV TRACKING NEWD FROM THE ERN PLAINS/MS VLY ALONG WITH
INTERACTION WITH ASSOCIATED SFC WAVE/WAVY LEADING FRONTAL ZONE
SHOULD SPELL AN INCREASING PROBABILITY/OPPORTUNITY FOR RAIN INTO
THE WEEKEND. HOWEVER CONFIDENCE IN PCPN DETAILS (I.E. POPS) IS
MEDIUM AT BEST DUE TO MODEL SPREAD/DEPENDENCE ON SMALLER SCALE
FEATURES. THE FCST MAY BE PERCEIVED AS SOMEWHAT PESSIMISTIC WITH
NEARLY DAILY CHC FOR SHWRS/TSTMS HOWEVER PCPN WILL CERTAINLY NOT
BE CONTINUOUS WITH PERIODS OF DRY WX MIXED IN BTWN GENERALLY SCT
AND LARGELY DISORGANIZED/WEAKLY FORCED PCPN.

THERE IS HIGHER CONFIDENCE IN A WARMING TREND WITH MAX TEMPS 5-10F
ABOVE NORMAL OVER THE WEEKEND AND INTO THE FIRST WEEK OF SEPT.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
LEADING EDGE OF STRATO CU AND LOW-END ALTO CU ASSOCIATED WITH AN
AXIS OF MUCH HIGHER PWAT AIR /NEAR 1.75 INCHES FROM NERN OHIO TO
SWRN NEW YORK/ WERE DRIFTING INTO THE CENTRAL RIDGE AND VALLEY
REGION AT SUNRISE...WHILE SKIES WERE MAINLY CLEAR ACROSS THE
SOUTHEASTERN HALF OF THE STATE. LIGHT AND VARIABLE...TO LIGHT
SOUTHWESTERLY WIND WAS NOTED AT ALL AIRFIELDS.

SFC COLD FRONT WAS SLIDING JUST SE OF THE I-90 CORRIDOR FROM KCLE
TO KERI AND KROC ATTM. CLOUD BASES AT KBFD AND KJST SHOULD DIP
INTO THE MVFR RANGE AT TIMES LATER THIS MORNING AND EARLY THIS
AFTERNOON /WITH SOME OCNL IFR POSSIBLE AT BRADFORD BETWEEN
11-14Z/.

THE COLD FRONT WILL DRIFT SLOWLY SE AND CROSS CENTRAL PA AIRFIELDS
DURING THE LATE AFTERNOON HOURS...BEFORE REACHING THE LOWER
SUSQUEHANNA VALLEY /KMDT AND KLNS/ LATER THIS EVENING.

INSTABILITY AND MOISTURE WILL BE QUITE HIGH AHEAD OF THE COLD
FRONT...SO INCLUDED VCTS FOR ABOUT A 4-HOUR PERIOD PRECEDING THE
FRONTAL PASSAGE. BRIEF MVFR CONDITIONS ARE POSSIBLE IN THE
THUNDERSTORMS.

MAINLY VFR IS EXPECTED TONIGHT INTO THURSDAY IN THE WAKE OF THE
CFROPA. A 6-10 HOUR PERIOD OF NW WINDS AVERAGE 8-10 KTS...WITH GUSTS
IN THE MID-UPPER TEENS IS EXPECTED LATE TODAY AND TONIGHT IN THE
MDTLY TIGHT LLVL PRESSURE GRADIENT FOLLOWING THE COLD FRONT.

OUTLOOK...

THU-FRI...LATE NIGHT-EARLY MORNING RESTRICTIONS IN FOG
POSSIBLE...OTHERWISE VFR.

SAT-SUN...MAINLY VFR. CHC OF AFTERNOON SHOWERS/ISOLD TSTMS.

&&

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

&&

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



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