FXUS61 KCTP 111224
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
724 AM EST FRI DEC 11 2009
.SYNOPSIS...
A BRISK WESTERLY FLOW WILL BRING SIGNIFICANT LAKE EFFECT SNOW TO FAR
NORTHWESTERN PENNSYLVANIA TODAY AND TONIGHT. HIGH PRESSURE BUILDING
NE FROM THE TENNESSEE VALLEY WILL BRING FAIR AND COLD WEATHER
ELSEWHERE TODAY THROUGH SATURDAY. LOW PRESSURE ALONG THE GULF COAST
LATE SATURDAY WILL MOVE TO THE NORTHEAST AND BRING A MIXED BAG OF
GENERALLY LIGHT PRECIPITATION TO THE REGION SUNDAY MORNING...BEFORE
CHANGING TO MAINLY RAIN THE AFTERNOON. AFTER A BRIEF PERIOD OF DRY
WEATHER WITH MODERATING TEMPERATURES ON MONDAY...A SHARP COLD FRONT
WILL PUSH ACROSS THE COMMONWEALTH TUESDAY USHERING IN ANOTHER BLAST
OF ARCTIC AIR...WITH GUSTY WINDS AND SNOW SHOWERS FOR THE MIDDLE AND
LATTER PART OF NEXT WEEK.
&&
.NEAR TERM /THROUGH TONIGHT/...
COLD CYC BL FLOW WILL CONT ACROSS THE REGION TDY BEFORE GRADUALLY
WANING INTO THE WEEKEND. SFC HIGH PRES INITIALLY CENTERED OVER THE
TN VLY WILL SLIDE ENEWD INTO THE VA TIDEWATER BY 12/12Z...WHILE THE
MID/UPPER LEVEL FLOW TRANSITIONS TWD A MORE ZONAL ORIENTATION.
EARLY MORNING READINGS IN THE SINGLE DIGITS AND TEENS COMBINED
WITH A BRISK AND GUSTY WEST WIND WILL RESULT IN WIND CHILLS OF
ZERO TO 10 BELOW ZERO EARLY THIS MORNING. NO OFFICIAL REPORTING
STATIONS OBSERVED -15F OR COLDER WIND CHILLS OVERNIGHT OR THIS
MORNING...SO THE WIND CHILL ADVISORY HAS BEEN CANCELLED.
REGIONAL RDR SHOWS INTENSE SINGLE LES BAND EXTENDING ENEWD FM ERI
ACROSS THE WESTERN SOUTHERN TIER OF NYS. EARLY SEASON RELATIVE
WARMTH OF LAKE ERIE HAS CERTAINLY BEEN CONTRIBUTING TO ENHANCED
INSTABILITY WITH DELTA T VALUES IN EXCESS OF 20C. LATEST HI RES MDLS
SUGGEST THIS BAND WILL EVENTUALLY TAKE ON A WEST-EAST ORIENTATION
THRU THE DAY AS IT SAGS SWD TO ALONG THE PA/NY BORDER. UPSTREAM STLT
IMAGERY AND SFC OBS APPEAR TO BE CONFIRMING THE SLIGHT VEERING OF
THE MEAN LLVL WIND TO PURE WLY 270-280 DEGS BY THIS AFTN. A BLEND OF
HI RES MDL QPF AND 15-20:1 SLR RESULTS IN LOCALIZED 24HR SNOW ACCUMS
OF 6-8" ACROSS THE SNOWBELT OF NORTHERN WARREN COUNTY...WITH LESSER
AMOUNTS OF 2-4" FURTHER EAST OVER NORTHERN MCKEAN COUNTY.
THEREFORE...HAVE ISSUED A LAKE EFFECT WARNING AND ADVISORY FOR THESE
AREAS THRU 12Z SAT. INC BL SHEAR AND LOWERING INVERSION HGTS WILL
SPELL AN END TO THE LAKE EFFECT INTO EARLY SATURDAY.
&&
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
SFC HIGH PRESSURE RIDGE SLIDING ENE FROM THE CENTRAL APPALACHIANS
WILL PROVIDE MORE TRANQUIL CONDITIONS FOR SATURDAY...WITH RATHER
ABUNDANT SUNSHINE ACROSS THE SOUTHERN TWO THIRDS OF THE STATE.
LITTLE MORE THAN A FEW ISOLATED/MAINLY MORNING SNOW SHOWERS ARE
EXPECTED ACROSS THE FAR NORTH.
AFTER A COLD START TO THE DAY...EVEN THE PLENTIFUL SUNSHINE WON'T BE
ABLE TO WARM TEMPS BACK TO NORMAL...GIVEN THE 850 MB TEMPS OF -6 TO
-10C ACROSS THE REGION. MAX TEMPS SAT WILL BE ABOUT 5 DEG F BELOW
NORMAL...RANGING FROM THE U20S ACROSS THE NW MTNS...TO THE U30S IN
THE SE VALLEYS.
AFTER A MAINLY CLEAR START DURING THE EVENING...CLOUDS WILL
INCREASE/THICKEN UP FROM THE SW SAT NIGHT. A SHARP TEMP DROP WILL
OCCUR IN THE EVENING (THANKS TO LIGHT AND VARIABLE WINDS AND
DEWPOINTS IN THE SINGLE DIGITS/TEENS). TEMPS WILL LEVEL OFF LATE
WITHIN A FEW DEG F OF NORMAL LOWS IN THE UPR TEENS TO MID 20S.
&&
.LONG TERM /MONDAY THROUGH THURSDAY/...
AFTER THE HIGH PRESSURE AREA DEPARTS EAST OF THE MID ATLANTIC COAST
LATE SAT NIGHT...A COUPLED 300 MB JET CIRCULATION WILL
DEVELOP/ADVECT EAST FROM THE OHIO RIVER VALLEY. THIS WILL HELP TO
ENHANCE THE SOUTH TO SSW...850 MB JET TO 40-50 KTS (OR 1-2 ST
DEVIATIONS ABOVE NORMAL) - WITH PRECIP WATER (VIA THE SUPER
ENSEMBLE) INCREASING TO AROUND 0.75" BY 18Z SUNDAY.
IN CONTRAST TO THE PREVIOUS FEW WINTRY STORMS...THIS SYSTEM APPEARS
TO LACK SIGNIFICANT LLVL COLD AIR AND AN EAST TO NE COMPONENT TO THE
SFC-925 MB WIND. THEREFORE...PRECIP TYPE WILL BE SKEWED MUCH MORE
TWD A BRIEF MIX IN THE MORNING...THEN MAINLY LIGHT RAIN FOR THE
AFTERNOON AS 925-850 MB WET BULB TEMPS RISE TO ABOVE ZERO WITH SFC
TEMPS IN THE MID TO U30S IN MOST PLACES. THE NRN MTNS COULD HANG
ONTO ENOUGH COLD AIR DURING THE DAY TO MAINTAIN A LIGHT WINTRY MIX
THROUGHOUT THE AFTERNOON. LIGHT SNOW/SLEET (OR POSS FZRA) ACCUMS
WILL BE LIMITED TO THE EARLY TO MID MORNING IN MOST LOCATIONS PER
THE 03Z SREF PTYPE AMD THE SIMILAR OPERATIONAL 00/06Z NAM/GFS.
A BRIEF LULL IN THE PRECIP...WITH PARTLY SUNNY SKIES AND SLIGHTLY
ABOVE NORMAL TEMPS WILL ARRIVE TO START THE NEW WEEK AS ANOTHER AREA
OF HIGH PRESSURE SLIDES NE TO THE MID ATLANTIC SEABOARD.
FOR THE MONDAY NIGHT/WED TIMEFRAME...AN AMPLIFYING UPPER TROUGH AND
ARCTIC FRONT WILL PLOW EAST FROM THE MIDWEST. RAIN SHOWERS WILL BE
THE PRIMARY PRECIP TYPE AHEAD OF THIS FRONT...WITH EVEN A RUMBLE OF
THUNDER ALONG THE CFROPA EARLY TUESDAY GIVEN THE STRONG DYNAMICS AND
COLLOCATED ENTRANCE REGION OF A 160+ KT UPPER JET.
AS THE PRIMARY LIFT FROM THE JET SLIDES ABOVE THE MAIN BAROCLINICITY
CLOSER TO THE MID ATLANTIC COAST...A SECONDARY SFC LOW MAY SPIN UP
CLOSE ENOUGH TO EXTEND THE PRECIP THROUGH THE LATE AFTERNOON TUESDAY
ACROSS OUR ERN ZONES (AND POSSIBLY LEAD TO A PERIOD OF STEADY SNOW).
ELSEWHERE...MAX TEMPS WILL BE ACHIEVED DURING THE MORNING...WITH
STEADY OR FALLING TEMPS IN THE AFTERNOON...AS WESTERLY WINDS
INCREASE AND GUST OVER 40 MPH LATER IN THE DAY AND TUESDAY
NIGHT/WED. NUMEROUS SNOW SHOWERS AND AREAS OF LES EXPECTED ACROSS
THE NRN AND WESTERN MTNS WITH MUCH BELOW NORMAL TEMPS FOR THE MID TO
LATE WEEK PERIOD (DEC 16-18).
&&
.AVIATION /13Z FRIDAY THROUGH TUESDAY/...
COLD CYC FLOW WILL GRADUALLY RELINQUISH ITS GRIP ON THE REGION
OVER THE NEXT 24 TO 48 HOURS...AS SFC HIGH PRES SLIDES ENE FM THE
TN VLY INTO THE VA TIDEWATER. MDL GUID SHOWS THE HEAVY LES BAND
CURRENTLY ACROSS WRN NYS TO BECOME ORIENTED W-E ALONG THE PA/NY
BORDER. XPC MVFR/IFR RESTRICTIONS IN SHSN AT BFD AS A RESULT.
ELSEWHERE XPC MAINLY VFR WITH SCT-BKN CIGS 3-6KFT AGL. WLY SFC
WNDS WL REMAIN GUSTY 20-30KTS BEFORE RELAXING THIS EVE. PD OF VFR
WILL BE BRIEF ON SAT WITH CONDS DETERIORATING LATE SAT NGT THRU
SUNDAY AS A LOW PRESSURE SYSTEM LIFTS NORTHWARD FROM THE SOUTHEAST
COAST TO THE DELMARVA.
OUTLOOK...
SAT...VFR.
SUN/MON...MVFR/IFR LKLY IN MIXED PRECIPITATION.
TUE...VFR/MVFR WITH A CHANCE OF SHSN/RASN.
&&
.CTP WATCHES/WARNINGS/ADVISORIES...
LAKE EFFECT SNOW ADVISORY UNTIL 7 AM EST SATURDAY FOR PAZ005.
LAKE EFFECT SNOW WARNING UNTIL 7 AM EST SATURDAY FOR PAZ004.
&&
$$
SYNOPSIS...LAMBERT
NEAR TERM...DEVOIR/STEINBUGL
SHORT TERM...LAMBERT
LONG TERM...LAMBERT
AVIATION...STEINBUGL
