000 FXUS61 KCTP 091556 AFDCTP AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE STATE COLLEGE PA 1056 AM EST THU FEB 9 2012 .SYNOPSIS... HIGH PRESSURE OVER THE MID MISSISSIPPI VALLEY WILL SLIDE EAST TO THE CAROLINA COAST THROUGH FRIDAY...PROVIDING FAIR AND DRY WEATHER IN PENNSYLVANIA. AN AMPLIFYING UPPER LEVEL TROUGH OVER THE EASTERN U.S. WILL SEND A STRONG COLD FRONT ACROSS THE STATE FRIDAY NIGHT. A WEAK WAVE OF LOW PRESSURE PASSING TO THE SOUTH WILL ALSO MAKE LIGHT SNOW ACROSS THE SOUTHEAST ON FRIDAY NIGHT. BEHIND THE FRONT...MODIFIED ARCTIC AIR TO POUR INTO THE REGION FOR THE WEEKEND. && .NEAR TERM /THROUGH TONIGHT/... TRAPPED MOISTURE OVER THE NW MTNS WILL ONLY SLOWLY BURN OFF. SFC RIDGE OVER THE EASTERN UNITED STATES WILL WEAKEN ONLY SLIGHTLY TONIGHT. CLEAR OR CLEARING SKIES WILL ALLOW TEMPS TO GET INTO THE MID 30S IN THE W AND LOWER 40S IN THE SE....PRETTY NORMAL OVERALL. LOWS TONIGHT SHOULD ALSO DROP BACK TO NEAR NORMALS OF UPPER TEENS AND 20S...BUT COULD GO LOWER DEPENDING ON HOW MUCH OF THE SNOW CAN MELT TODAY UNDER THE MID-FEB SUNSHINE. BETTER SNOW PACK WOULD ALLOW FOR MORE RADIATIONAL COOLING. && .SHORT TERM /FRIDAY THROUGH SATURDAY/... HIGH PRESSURE RIDGE WILL EXTEND FROM THE LOWER MISSISSIPPI VALLEY TO THE CAROLINA COAST ON FRIDAY. TIGHTENING LLVL PRESSURE GRADIENT AND DEEP MIXING /THROUGH ABOUT 6 KFT AGL/ OF THE MEAN WESTERLY FLOW WILL LEAD TO A RATHER WINDY LATE MORNING AND AFTERNOON. GUSTS OF 25 TO 30 MPH ARE LIKELY FOR SEVERAL HOURS DURING THE MIDDLE OF THE DAY. MULTI-LAYERED CLOUDS WILL THICKEN-UP FROM WEST TO EAST LATER IN THE AFTERNOON AND EVENING AHEAD OF AN AMPLIFYING MERIDIONAL TROUGH THAT WILL EXTEND FROM JAMES BAY...SOUTH ACROSS THE GLAKES...TO THE GULF COAST STATES. A DEVELOPING WAVE OVER THE DEEP SOUTH WILL START TO BRING MOISTURE NORTHWARD INTO THE CWA LATE IN THE DAY. PRECIP FROM THE WEAK ISENTROPIC LIFT COULD BEGIN BEFORE DARK. THIS COULD MAKE IT BE RAIN AT FIRST...BUT AFTER TEMPS DIP A LITTLE...THE VERTICAL THERMAL PROFILE IS DECIDEDLY SNOW. HIGHS WILL BE IN THE MID 30S ACROSS THE MTNS...AND UPPER 30S TO LOWER 40S ELSEWHERE. SEVERAL OF OUR SE ZONES WILL LIKELY SEE THE MERCURY TOP OUT IN THE MID 40S. THESE TEMPS WILL BE 5-6F ABOVE NORMAL. LEAD SHORTWAVE AND A SHIELD OF LIGHT SNOW WILL LIKELY STREAK ENE FROM THE OHIO VALLEY AND BRUSH PARTS SRN AND EASTERN PENN WITH A PERIOD OF MAINLY LIGHT SNOW...WITHIN THE WARM ADVECTION PATTERN AND ENHANCED LARGE SCALE LIFT SUPPLIED BY THE THERMALLY DIRECT...RIGHT ENTRANCE REGION OF A 115 KT...300 MB JET MAX THAT WILL SLIDE ACROSS PENN FRIDAY NIGHT. PAINTED A COATING TO 1.5 INCHES OF SNOW ACCUM IN OUR GRIDS ASSOCIATED WITH THIS INITIAL FEATURE. THE BIGGER STORY FOR THE FIRST HALF OF THIS EXTENDED PERIOD WITH BE THE BLAST OF MUCH COLDER AIR THAT WILL PUSH INTO THE REGION FOR VERY LATE FRIDAY NIGHT /NW MTNS/...THROUGH THE UPCOMING WEEKEND. THE ARCTIC FRONT WILL LIKELY BE ACCOMPANIED BY PERIODS OF MDT SNOW SHOWERS AND EVEN A FEW BLINDING NORTH/SOUTH BANDS OF SQUALLS AS THE SHARPENING MID/UPPER LEVEL TROUGH AXIS MOVES OVER THE REGION WITH 700 MB TEMPS DOWN TO NEAR -22C OVER WRN PENN BY LATE SAT /WITH 500 MB TEMPS APPROX -38C/. THIS WILL BE ABOUT THE COLDEST AIR WE/VE SEEN AT THESE LEVELS THIS WINTER. A POCKET OF VERY STEEP LAPSE RATES AROUND 7.5C/KM WILL MOVE EAST ACROSS THE WEST IN THE MORNING...SUPPORTING THE SQUALLS. BUT THESE SHSN SHOULD WEAKEN AND BREAK UP IN THE DOWNSLOPE EAST OF THE MOUNTAINS. SNOW ACCUMS FRIDAY NIGHT AND SATURDAY ACROSS THE CENTRAL AND NW MTNS WILL VARY FROM A COATING TO ONE INCH IN THE VALLEYS WITH A GOOD 2-3 INCHES COMMON ACROSS THE ALLEGHENY PLATEAU. '' MAX TEMPS THAT WILL BE ALMOST 10F BELOW NORMAL SATURDAY...WILL REBOUND BY A FEW DEG F ON SUNDAY. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... SNOW SHOWERS SAT NIGHT AND SUNDAY /UNDER DEEP NW FLOW AND A SUBSIDENCE INVERSION BASE BETWEEN 4-7 KFT AGL/ WEILL BE CONFINED MAINLY ACROSS THE LAUREL HIGHLANDS AND NW MTNS...WHERE ADDITIONAL LIGHT ACCUMULATIONS WILL OCCUR. THE COLDEST TEMPS OF THIS BRIEF...ARCTIC OUTBREAK WILL OCCUR SAT NIGHT WHEN LOWS WILL BE IN THE SINGLE DIGITS ACROSS THE NRN MTNS...AND GENERALLY BETWEEN 10-15 F ELSEWHERE. IT WILL BE WINDY OVER THE WEEKEND...ESPECIALLY SUNDAY AS A SECONDARY SHORT WAVE IF FOLLOWED BY THE DESCENDING BRANCH/RIGHT EXIT REGION OF AN UPPER JET STREAK. VERT MIXING TO AROUND 5 KFT AGL SUNDAY MAY TAP SOME PRETTY STRONG WNW WINDS OF NEARLY 40 KTS. THEREFORE...THERE WILL BE SOME SIGNIFICANT/LOW WIND CHILLS TO CONTEND WITH...WHICH WILL BE A SHOCKING CHANGE FROM WHAT WE/VE BECOME USED TO OVER RECENT WEEKS. MODERATING TEMPS...MUCH LESS WIND...AND DRY CONDITIONS ON MONDAY WILL BE FOLLOWED BY ANOTHER RELATIVELY LIGHT WINTRY PRECIP EVENT FOR TUESDAY. && .AVIATION /16Z THURSDAY THROUGH MONDAY/... BUILDING SFC RIDGE HAS CLEARED THE SKIES FOR ALL BUT THE AREAS BETWEEN BFD AND JST. EVEN THOSE LOCATIONS ARE VFR FOR NOW. BUT WEAK UPSLOPE WILL CONTINUE TO PROVIDE ENOUGH LIFT FOR AT LEAST SCT IF NOT BKN CLOUDS OVER THE WRN MOUNTAINS THIS AFTN. SOME INCREASE IN LOW CLOUD IS POSSIBLE OVER THE WEST AFTER SUNSET. THERE SHOULD BE SOME GUSTY WINDS DUE TO THE MIXING TODAY...THOUGH ANY GUST WILL BE 20MPH AT MOST. THE RIDGE WILL STAY FAR ENOUGH AWAY TO PROVIDE VERY LIGHT WIND THROUGH THE NIGHT. GOOD FLYING CONDITIONS WILL PERSIST TONIGHT...THRU MOST OF THE DAY FRIDAY. BUT TWO FEATURES WILL PUT A SQUEEZE ON THE REGION. A WEAK WAVE WILL MOVE ACROSS THE CENTRAL APPALACHIANS FRIDAY NIGHT AND CREATE LIGHT SNOW AND LOW CIGS FRIDAY NIGHT OVER THE SRN THIRD OF THE AREA...MAINLY IN MDT AND LNS. THE SECOND FEATURE IS A STRONG COLD FRONT WHICH WILL BRING SNOW SHOWERS AND SQUALLS LATE FRIDAY NIGHT AND EARLY SAT MORNING TO THE NW HALF OF THE AREA. EXPECT GUSTY WINDS...VERY LOW VISBYS AND CIGS IN THE NW HALF /BFD-JST/ BETWEEN 03 AND 12Z SAT. LOW CIGS AND VISBYS ARE ALSO POSSIBLE AT IPT-UNV-AOO AS WELL - MAINLY SAT MORNING WITHIN 3-4 HRS OF 12Z. OUTLOOK... SAT AFTN-SUN...MVFR/OCNL IFR NW IN SHSN. VFR ELSEWHERE. MON...VFR. && .CTP WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...DANGELO NEAR TERM...DANGELO SHORT TERM...DANGELO/LAMBERT LONG TERM...LAMBERT/MARTIN AVIATION...DANGELO/CERU