FXUS61 KCTP 120122
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
822 PM EST FRI DEC 11 2009
.SYNOPSIS...
A BRISK WESTERLY FLOW WILL BRING SIGNIFICANT LAKE EFFECT SNOW TO FAR
NORTHWESTERN PENNSYLVANIA THROUGH 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 /UNTIL 6 AM SATURDAY MORNING/...
COLD CYC BL FLOW WILL CONT ACROSS THE REGION TONIGHT BEFORE
MODERATING THIS WEEKEND. SFC HIGH PRES INITIALLY CENTERED OVER
THE TN VLY WILL SLIDE ENEWD TO THE MID ATLANTIC COAST BY EARLY
SATURDAY AS UPPER FLOW RELAXES AND BECOMES ZONAL.
STORM TOTALS OF UP TO 8 INCHES HAVE BEEN RECEIVED THIS EVENING BY
SPOTTERS OVR EXTREME NW WARREN COUNTY. HOWEVER...REGIONAL RADAR
MOSAIC NOW SHOWING AN OVERALL WEAKENING OF THE SNOW BANDS OF LK
ERIE. EXPECT WEAKENING TREND TO CONTINUE OVERNIGHT...AS INVERSION
HGTS FALLS. MAY BE ABLE TO CANCEL WARNING/ADVISORY LATER TONIGHT
ACROSS THE NW MTNS.
REGARDING AMOUNTS: A BLEND OF HI RES MDL QPF AND 15-20:1 SNOW
RATIOS GIVES 1-3 INCHES OF ADDITIONAL ACCUM ACROSS PARTS OF
NORTHERN WARREN/MCKEAN COUNTIES...MOST OF WHICH WILL FALL BEFORE
MIDNIGHT. INC BL SHEAR AND LOWERING INVERSION HGTS WILL SPELL AN
END TO THE LAKE EFFECT INTO EARLY SATURDAY.
&&
.SHORT TERM /6 AM SATURDAY MORNING THROUGH 6 PM SATURDAY/...
SFC HIGH PRESSURE RIDGE SLIDING ENE FROM THE CENTRAL APPALACHIANS
WILL PROVIDE MORE TRANQUIL CONDITIONS FOR SATURDAY...WITH 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...MAINLY IN THE MORNING.
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.
&&
.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
AS LONG TERM PERIOD BEGINS SFC HIGH SHOULD BE CENTERED EAST OF
PA...PLACING MUCH OF OHIO VALLEY IN A BROAD REGION OF SURFACE
WAA...RESULTING IN THE DEVELOPMENT IN A LARGE AREA OF PRECIPITATION
THAT WILL ARRIVE IN THE CWA BY DAWN SUNDAY. LATEST BUFKIT SOUNDINGS
SUGGEST...ESPECIALLY IN THE LAURELS AND ACROSS THE NORTHERN
TIER...THERE COULD BE A FEW HOURS OF -ZR DURING THE MORNING...BEFORE
ALL AREAS CHANGE OVER TO RAIN BY THE AFTERNOON.
12Z GFS INDICATES THAT SFC LOW DEVELOPS AND QUICKLY DEEPENDS OFF
THE VA COAST AHEAD OF 500MB VORT MAX LATE SUNDAY...BUT QUICKLY
MOVES WELL EAST OF THE CWA...ALLOWING WEAK SFC HIGH TO NOSE IN AND
DRY THE REGION OUT OVERNIGHT...STAYING IN PLACE THROUGH THE DAY
MONDAY. HIGH SLIDES EAST DURING THE DAY AS ANOTHER SFC LOW
APPROACHES FROM THE MID WEST...PLACING THE CWA IN STRONG SW FLOW
THAT WILL PROMOTE WHAT LOOK TO BE THE WARMEST CONDITIONS OF THE
WEEK...WITH TEMPS NEARING THE 50S ACROSS THE LOWER SUSQ.
NEXT CHANCE OF RA/SN COMES DURING THE DAY ON TUESDAY AS SFC LOW
AHEAD OF AMPLIFYING UPPER TROUGH BRINGS A COLD FRONT THROUGH THE
REGION...WITH ANOTHER SHOT OF COLD AIR RUSHING IN BEHIND IT. 12Z
MREF IN RATHER GOOD AGREEMENT THAT UPPER TROUGH WILL STALL AND
DEEPEN OVER THE REGION THROUGH THE REST OF THE WEEK...KEEPING COLD
AIR IN PLACE THROUGH THE FORECAST PERIOD...WITH DAYTIME HIGHS IN THE
20S AND 30S AND OVERNIGHT LOWS DROPPING INTO THE TEENS AND 20S.
&&
.AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
BFD AT TIMES WILL BE MVFR TONIGHT...AS THEY WILL BE ON THE SOUTHERN
EDGE OF THE BAND OF SNOW SHOWERS OFF LAKE ERIE. WINDS WILL TEND
TO SHIFT A LITTLE MORE TO THE NW OVERNIGHT...BUT MODELS MAY TRY
TO BRING WINDS AROUND TOO MUCH...AS LAKES ARE STILL WARMER THAN
NORMAL. OTHERWISE...MAINLY CLEAR SKIES AND VFR CONDITIONS WILL
PREVAIL ACROSS THE REST OF THE AREA. THE MAIN THING IS IT WILL
BE WINDY UNTIL LATE TONIGHT.
SATURDAY WILL FEATURE PLENTY OF CLEAR SKIES AND VFR CONDITIONS...
AND LIGHTER WINDS.
MVFR AND IFR CONDITIONS DEVELOP SUNDAY MORNING ACROSS THE AREA
AS A SW FLOW OF WARMER AIR MOVES OVER THE SNOW PACK. SOME RAIN...
WILL LIKELY START AS FREEZING RAIN AND SLEET...GIVEN TIME OF
DAY AND COLD GROUND TEMPERATURES. RAINFALL AMOUNTS ARE EXPECTED
TO BE LESS THAN A THIRD OF AN INCH.
WEAK HIGH PRESSURE BUILDS IN ON MONDAY. BY LATE MONDAY INTO
WED...THE NEXT FRONTAL SYSTEM MOVES IN FROM THE PLAINS...WITH
SOME RAIN SHOWERS. VFR CONDITIONS WILL BECOME MVFR AND IFR
MONDAY NIGHT ACROSS THE NW AND SPREAD EASTWARD ON TUESDAY.
RAIN SHOWERS MAY END AS A BRIEF PERIOD OF SNOW SHOWERS ACROSS
THE WEST AND NORTH TUESDAY NIGHT AND WED MORNING.
OUTLOOK...
SUN...MVFR/IFR LKLY IN MIXED PRECIPITATION.
MON...VFR BECOMING MVFR AND IFR LATE IN RAIN SHOWERS.
TUE-WED...IFR/MVFR WITH A CHANCE OF RAIN SHOWERS...
PERHAPS ENDING AS A BRIEF PERIOD OF SNOW SHOWERS.
&&
.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...DEVOIR
NEAR TERM...DEVOIR/FITZGERALD
SHORT TERM...LAMBERT
LONG TERM...ONDREJIK/DICKEY
AVIATION...MARTIN
