Area Forecast Discussion
Issued by NWS

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461 FXUS61 KPBZ 122248 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 548 PM EST FRI FEB 12 2016 .SYNOPSIS... AN ARCTIC FRONT WILL BRING SNOW SHOWERS TO THE AREA THROUGH SATURDAY. MUCH COLDER TEMPERATURES AND DANGEROUS WIND CHILLS WILL CONTINUE INTO THE WEEKEND. && .NEAR TERM /THROUGH SATURDAY/...
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BASED ON LATEST OBSERVATIONS AND RADAR TRENDS CURRENT TIMING OF POTENTIAL SQUALL CONDITIONS STILL LOOKS GOOD AS WV IMAGERY SHOWS THE JET CORE ROUNDING THE BASE OF THE LONGWAVE PIVOTING OVER THE AREA. NOT MUCH CHANGE IS NEEDED AT THIS TIME TO THE ONGOING FORECAST OTHER THAN MINOR ADJUSTMENTS TO HOURLY TEMPERATURES. PREV DISCUSSION FOLLOWS.. SHORTWAVE PIVOTING ALONG THE BASE OF THE UPPER TROUGH WILL SUPPORT INCREASING SNOW CHANCES IN THE RIDGES AHEAD OF THE ARCTIC FRONT PASSAGE PROGGED FOR THIS EVENING/OVERNIGHT. BOTH HI RES AND LONGER RANGE MODEL SOUNDINGS IN BUFKIT SUGGEST A PERIOD WHERE DEEP MOISTURE...IN A LAYER FROM ABOUT 600MB TO 850MB...WILL BE WELL WITHIN THE DENDRITIC GROWTH ZONE. THIS SHOULD SUPPORT EFFICIENT SNOWFALL FOR A PERIOD...WITH ADDITIONAL SNOW SHOWERS ANTICIPATED WITH AND BEHIND THE FRONT IN UPSLOPE SNOW UNTIL THE WHOLE BOUNDARY LAYER FALLS WELL BELOW THE GROWTH ZONE. WITH THIS IN MIND...A WINTER WEATHER ADVISORY WAS ISSUED FOR THE RIDGES OF PRESTON TUCKER AND GARRETT COUNTIES THROUGH SATURDAY MORNING. ELSEWHERE...THE MODEL GUIDANCE HAS CHANGED LITTLE WITH THE TIMING OF THE SNOW SHOWERS AND POTENTIAL SQUALLS AHEAD OF THE FRONT PROGGED FOR PASSAGE OVERNIGHT. EXPECT THE LINE TO BE INTO EASTERN OHIO AND NORTHWESTERN PA BY 00Z AND PITTSBURGH BY 03Z. VARIOUS RUNS OF THE HRRR AND TO A LESSER DEGREE OTHER SNOW SQUALLS PROGS SUGGEST THAT THERE WILL BE SOME WEAKENING AS THE LINE COMES ACROSS. GENERALLY ANTICIPATE A HALF TO AN INCH OF SNOW...WITH SLIGHTLY HIGHER AMOUNTS NORTH OF PITTSBURGH. BEHIND THE FRONT...STRONG COLD ADVECTION WILL STEEPEN LAPSE RATES AND PROVIDE FOR A PERIOD OF GUSTY WINDS AREAWIDE UNTIL LATE SATURDAY WITH MAXIMUM WIND IN THE BOUNDARY LAYER APPROACHING 25 TO 35KTS. THIS...ADDED TO TEMPERATURES FALLING INTO THE SINGLE DIGITS WILL LEAD TO WIND CHILL VALUES WELL BELOW ZERO. THIS SUPPORTS THE WIND CHILL ADVISORY THAT WAS ISSUED. 40MPH WIND GUSTS OVERNIGHT IN THE RIDGES WILL ALLOW VALUES TO GET VERY CLOSE TO WARNING CRITERIA BUT AT THIS POINT...THE WATCH HAS BEEN UPGRADED TO AN ADVISORY WITH SOME -25 VALUES POSSIBLE IN THE HIGHEST TERRAIN OF TUCKER COUNTY. IN ADDITION TO THE WIND...LAKE EFFECT SNOW SHOWERS WILL BE POSSIBLE IN NORTHWEST FLOW WITH MOST IF NOT ALL OF THE MODEL GUIDANCE SUGGESTING SEVERAL DUAL-LAKE SNOW BANDS. THE LATEST ITERATION OF MODELS HAS THE MORE PROMINENT BAND SHIFTED SLIGHTLY SOUTH FROM LAST NIGHT SO WITH UNCERTAINTY IN THE ACTUAL PLACEMENT OF SNOW BANDS...HAVE OPTED TO UPGRADE THE LAKE EFFECT SNOW WATCH FOR VENANGO COUNTY TO AN ADVISORY FOR MERCER...VENANGO...AND FOREST COUNTIES. ADDITIONAL LAKE PLUMES MAY SUPPORT SNOW BEYOND THESE ADVISORIES THROUGH SATURDAY AFTERNOON...BUT WITH UNCERTAINTY IN THEIR PLACEMENT...NO ADDITIONAL HEADLINES WERE ADDED.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... LAKE EFFECT SNOW SHOWERS WILL CONTINUE TO TAPER OFF AND SHIFT NORTHWARD AS A SURFACE RIDGE ATTEMPTS TO BUILD OVERHEAD FOR SUNDAY. THIS SHOULD ALLOW FOR THE WIND TO BACK OFF...WITH WIND CHILL CONCERNS DIMINISHING IN OHIO. HOWEVER...WITH THE HIGH PRESSURE AND LIGHT WIND...TEMPERATURES WILL FALL CLOSE TO OR BELOW ZERO SATURDAY NIGHT...SO ADVISORIES WILL REMAIN AS IS FOR THE REST OF THE CWA UNTIL SUNDAY MORNING. TEMPERATURES WILL MODERATE A FEW DEGREES ON SUNDAY WITH A RETURN OF SOUTHERLY FLOW AND SCATTERING OF THE CLOUDS. TEMPERATURE FORECAST WAS A BLEND OF GUIDANCE FOR BOTH PERIODS. && .LONG TERM /MONDAY THROUGH FRIDAY/... SHORTWAVE MOVING EAST ACROSS THE GREAT LAKES WILL BRING WARM ADVECTION ALONG WITH AN INCREASE IN DEEPER MOISTURE SUNDAY NIGHT INTO MONDAY. THIS WILL GIVE A PERIOD OF SNOW ESPECIALLY SOUTH OF PITTSBURGH WITH SOME ACCUMULATION EXPECTED. TEMPERATURES LOOK TO RISE LATER SUNDAY NIGHT AND WILL PUSH TO NEAR THE SEASONAL AVERAGE MONDAY. BY LATER MONDAY THROUGH TUESDAY A STRONG SOUTHERN STREAM SHORTWAVE WILL INDUCE LOW PRESSURE ALONG THE GULF COAST WHICH WILL QUICKLY MOVE ACROSS THE MID ATLANTIC STATES. MODELS STILL DIFFER ON EXACT TRACK BUT SYSTEM WILL CROSS THE SOUTHERN APPALACHIANS AND INTENSIFY AS IT MOVES TOWARD NEW ENGLAND BY TUESDAY NIGHT. POTENTIAL FOR SIGNIFICANT SNOW...BUT ALSO POTENTIAL FOR A MIX WITH RAIN OR ALL RAIN WHERE BETTER QPF IS FORECAST. FOR NOW HAVE NOT STRAYED FAR FROM PREVIOUS FORECAST ALTHOUGH EVEN THE WARMER ECMWF WRAPS COLD AIR BACK IN LATER TUESDAY SO HAVE KEPT MAINLY SNOW. SYSTEM EXITS TUESDAY NIGHT...BUT WILL BE FOLLOWED BY FAST MOVING CLIPPER SYSTEM WEDNESDAY WHICH WILL DELIVER ANOTHER PERIOD OF SNOW SHOWERS FOLLOWED BY A QUICK SHOT OF COLD AIR. HEIGHTS ALOFT THEN BEGIN TO RISE THURSDAY INTO FRIDAY WITH STRONG WARM ADVECTION...ESPECIALLY ON FRIDAY. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... LIGHT SNOW HAS DROPPED VSBY TO MVFR OR BELOW FOR A TIME AT KMGW AND KLBE AS A SHORTWAVE SHIFTS EAST TO THE MID ATLANTIC. SNOW SHOWERS ALSO WILL DEVELOP AHEAD OF APPROACHING ARCTIC FRONT...WITH MVFR TO IFR THIS EVENING WITH AND BEHIND THE FRONT. WINDS WILL BE GUSTY OVER 25KTS AND TURNING NORTHWEST WITH AND BEHIND THE FRONT. .OUTLOOK.../FRIDAY NIGHT THROUGH WEDNESDAY/... SCATTERED RESTRICTIONS IN SNOW SHOWERS SATURDAY. LOW PRESSURE SYSTEMS WILL BRING WIDESPREAD RESTRICTIONS LATER SUNDAY NIGHT THROUGH WEDNESDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EST SUNDAY FOR MDZ001. WINTER WEATHER ADVISORY UNTIL 10 AM EST SATURDAY FOR MDZ001. OH...WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 11 AM EST SATURDAY FOR OHZ039-048-049-057>059-068-069. WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EST SUNDAY FOR OHZ040-041-050. PA...WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EST SUNDAY FOR PAZ007>009-013>016-020>023-029-031-073>076. LAKE EFFECT SNOW ADVISORY UNTIL 7 PM EST SATURDAY FOR PAZ007>009. WV...WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 11 AM EST SATURDAY FOR WVZ003-004-012. WIND CHILL ADVISORY FROM MIDNIGHT TONIGHT TO 9 AM EST SUNDAY FOR WVZ001-002-021-509>514. WINTER WEATHER ADVISORY UNTIL 10 AM EST SATURDAY FOR WVZ512>514. && $$

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