Area Forecast Discussion
Issued by NWS State College, PA

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FXUS61 KCTP 301513
AFDCTP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1113 AM EDT THU OCT 30 2014

.SYNOPSIS...

HIGH PRESSURE WILL MOVE INTO THE APPALACHIANS TONIGHT. A VIGOROUS
UPPER LEVEL TROUGH DIGGING THROUGH THE CAROLINAS WILL SUPPORT THE
DEVELOPMENT OF A STRONG COASTAL STORM TRACKING JUST OFF THE EAST
COAST THIS WEEKEND. THIS WILL LEAD TO A BRISK NORTH NORTHWEST
WIND WITH MUCH COLDER AIR SUPPORTING SNOW SHOWERS OVER THE WESTERN
ALLEGHENIES SATURDAY NIGHT. HIGH PRESSURE WILL RETURN TO THE AREA
BEHIND THE DEPARTING STORM SYSTEM ON MONDAY WITH MODERATING
TEMPERATURES INTO THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...

HIGH PRESSURE OVER THE OHIO VALLEY WILL BUILD EAST AND HELP MIX
OUT MUCH OF THE LOW CLOUDINESS THAT IS OVER THE REGION EARLY
TODAY. DOWNSLOPE FLOW WILL LEAD TO THE BEST CHANCE OF SUN OVER
EASTERN AREAS BY LATE MORNING INTO THE AFTERNOON.

HIGH TEMPS WILL RANGE FROM THE MID 40S IN THE NW TO NEAR 60F IN
THE LWR SUSQ.

SHORTWAVE RIDGING ALOFT AND HIGH PRES AT THE SFC WILL COMBINE TO
BRING DRY WX TO CENTRAL PA FROM THIS AFTERNOON INTO TONIGHT. AN
AMPLIFYING UPPER TROUGH WILL PIVOT INTO THE UPPER GREAT LAKES BY
12Z FRI WITH A SFC LOW DEVELOPING NEAR LAKE HURON. THERE IS A
CHANCE FOR A FEW SHOWERS TO REACH FAR NW PA BY MORNING.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
ALL MEDIUM RANGE GUIDANCE STILL SHOWS A POTENT SHORTWAVE DIVING
SE THRU THE GRT LKS AND CARVING OUT A DEEP TROUGH OVR THE
NORTHEAST CONUS BY FRI NIGHT. TRACK OF THIS FEATURE NOW
APPEARS RELATIVELY CERTAIN BASED ON LACK OF SPREAD IN MDL
RUNS...ALL OF WHICH INDICATE A PATH ACROSS EASTERN OHIO FRIDAY PM.
BEST LG SCALE FORCING OVR PA...AS IMPLIED BY MDL 300-500MB Q-VEC
CONVERGENCE...SHOULD BE ACROSS THE WESTERN HALF OF THE STATE.
LATEST GEFS/SREF OUTPUT SUPPORT CATEGORICAL POPS ACROSS THE
ALLEGHENY PLATEAU FRI AFTN/FRI NIGHT AND ONLY CHC POPS ACROSS THE
SUSQ VALLEY. LACK OF DEEP MOISTURE SHOULD RESULT IN FAIRLY LIGHT RAINFALL
WITH THIS FEATURE...PERHAPS UP TO A QUARTER INCH OVR THE W MTNS.

RISK OF SNOW OVR THE ALLEGHENIES FRIDAY NIGHT APPEARS LOW GIVEN
LATEST OPER MDL SOUNDINGS...AS WELL AS GEFS/SREF PROBS. HAVE
REMOVED CHC OF SNOW AND RAISED OVERNIGHT LOWS TO ABOVE FREEZING
EVERYWHERE FRI NIGHT.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
ALL MED RANGE GUIDANCE CUTS OFF UPPER LOW SOUTH OF PA SATURDAY.
REMNANTS OF ASSOC CLIPPER LOW SHOULD DIE OVR THE CENTRAL
APPALACHIANS AS ENERGY IS TRANSFERRED TO DEVELOPING COASTAL LOW
NR CAPE HATTERAS. AS COASTAL STORM LIFTS NE...A TIGHTENING
PRESSURE GRADIENT AND NW FLOW WILL DRAW MUCH COLDER/DRIER AIR INTO
PA. OPERATIONAL RUNS AND NEARLY ALL ENSEMBLE MEMBERS KEEP COASTAL
LOW FAR ENOUGH OUT TO SEA TO NOT DIRECTLY IMPACT CENTRAL PA.
HOWEVER...COLD NW FLOW WILL LIKELY PRODUCE SCT LAKE EFFECT SNOW
SHOWERS ACROSS THE ALLEGHENY PLATEAU SATURDAY NIGHT. GIVEN DRYNESS
OF AIR MASS MOVING IN...DON/T EXPECT ANY SIG ACCUMS...BUT A
COATING OF SNOW DOES APPEAR POSSIBLE OVR THE W MTNS.

TEMPS THIS WEEKEND WILL ALMOST CERTAINLY BE THE COLDEST YET THIS
SEASON. ENSEMBLE MEAN 8H TEMPS POINT TOWARD DAYTIME HIGHS FROM
THE U30S-L40S OVR THE ALLEGHENIES TO 45-50F ACROSS THE LOWER SUSQ
VALLEY. THE COLDEST NIGHT OF THIS OUTBREAK WILL LIKELY BE SUNDAY
NIGHT...WHEN SFC HIGH BUILDS OVR THE REGION. THOSE LOCATIONS THAT
HAVE YET TO SEE A FREEZE WILL LIKELY GET IT BY MONDAY AM.

HIGH CONFIDENCE IN A PERIOD OF DRY WEATHER SUNDAY/MONDAY...WHEN
ALL GUIDANCE BUILDS SFC HIGH AND ASSOC DRY AIR MASS ACROSS PA. AN
APPROACHING COLD FRONT WILL BRING THE NEXT CHC OF SHRA BY
MIDWEEK. DEEP UPPER TROF WILL LIFT OUT QUICKLY EARLY NEXT
WEEK...ALLOWING A MUCH MILDER RETURN SW FLOW TO OVERSPREAD THE
REGION. TEMPS LIKELY TO RETURN TO ABV NORMAL READINGS BY TUESDAY.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...

LOW CLOUDS COVER MOST OF THE FCST AREA...WITH MVFR CEILINGS
PREDOMINATING OVER NORTHERN AND WESTERN HIGH TERRAIN. EXPECT THE
MVFR CEILINGS TO GRADUALLY MIX OUT OR LIFT UP AS WE GET INTO THE
AFTERNOON HOURS. THE HIGHER ELEVATIONS FROM JST UP THRU BFD WILL
TYPICALLY HOLD ONTO REDUCED CONDITIONS THE LONGEST...POSSIBLY
REMAINING UNDER 3000` THROUGH MID AFTERNOON.

LAYERED MID AND HIGH CLOUDS WILL BE INCREASING LATE TONIGHT INTO
FRIDAY AS A POTENT UPPER TROUGH MOVES OVER THE REGION.

OUTLOOK...

FRI...VFR/MVFR EARLY WITH RAIN SHOWERS DEVELOPING WRN SXNS BY EVE.
REDUCED CONDS LKLY FRI NIGHT WEST-CENTRAL 1/2 OF AIRSPACE WITH
RAIN SHOWERS MIXING WITH/CHANGING TO SNOW SHOWERS WESTERN 1/3.

SAT...MVFR/IFR WITH SCATTERED RAIN/SNOW SHOWERS WEST. VARYING
CONDS FROM VFR-MVFR CENTRAL/EAST WITH OCNL -SHRA. N-NW WIND GUSTS
25-40 MPH.

SUN...RAIN/SNOW SHOWERS ENDING WEST. LOW CIGS WEST BECOMING
VFR. GUSTY NNW WINDS GRADUALLY DECREASING AREA-WIDE.

MON...VFR.

&&

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

&&

$$
SYNOPSIS...LA CORTE/STEINBUGL
NEAR TERM...LA CORTE
SHORT TERM...FITZGERALD
LONG TERM...FITZGERALD
AVIATION...LA CORTE/STEINBUGL



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