Area Forecast Discussion
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000 FXUS61 KPBZ 121845 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 145 PM EST FRI FEB 12 2016 .SYNOPSIS... AN ARCTIC FRONT WILL BRING SNOW SHOWERS TO THE AREA LATER TODAY THROUGH SATURDAY. MUCH COLDER TEMPERATURES AND DANGEROUS WIND CHILLS WILL CONTINUE INTO THE WEEKEND BEHIND IT. && .NEAR TERM /THROUGH SATURDAY/... SHORTWAVE PIVOTING ALONG THE BASE OF THE UPPER TROUGH WILL SUPPORT INCREASING SNOW CHANCES IN THE RIDGES LATER THIS AFTERNOON 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 THIS AFTERNOON AHEAD OF THE ARCTIC FRONT...WITH ADDITIONAL SNOW SHOWERS ANTICIPATED WITH AND BEHIND THE FRONT IN UPSLOPE SNOW UNTIL THE WHOLE BOUNDARY LAYER FALLS WELL BELOW VALUES FOR EFFICIENT SNOWFALL. 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 PROGSSUGGEST 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 WITH ADDITIONAL CONCERN FOR THE RIDGES...AS 40MPH WIND GUSTS MAY SUPPORT AN UPGRADE OF THE WIND CHILL WATCH THIS AFTERNOON. FURTHER ANALYSIS WILL BE MADE WITH A DECISION LATER IN THIS SHIFT. 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 GUAL-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. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/... LAKE-EFFECT SNOW SHOWERS ACROSS THE NORTH WILL BE WANING LATE SATURDAY NIGHT AS THE UPPER-LEVEL LOW MOVES EAST AND A SURFACE HIGH APPROACHES FROM THE WEST. NORTHWEST FLOW BEHIND THE EXITING FRONT WILL BRING TEMPERATURES NEAR THE ZERO DEGREE MARK FOR SUNDAY MORNING LOWS. WITH HIGH PRESSURE STARTING TO BUILD IN...WINDS WILL BE DECREASING ACROSS EASTERN OHIO. TO THE EAST AND NORTH HOWEVER...SEVERAL MORE HOURS OF STRONG AND GUSTY WINDS WILL MEAN WIND CHILL VALUES BELOW -10F. THE HIGHEST ELEVATIONS COULD SEE WIND CHILLS AT OR BELOW -25F. WITH THIS IN MIND...THE WIND CHILL ADVISORY WILL CONTINUE FOR MUCH OF THE CWA INTO SUNDAY MORNING...WITH A WIND CHILL WATCH ACROSS GARRETT AND EASTERN TUCKER COUNTIES. BRIEF RIDGING SUNDAY AFTERNOON WILL FINALLY DISRUPT THE MEAN NORTHWEST FLOW PATTERN ALOFT. WARM AIR ADVECTION WILL GRADUALLY KICK INTO GEAR...BUT WITH SUCH A LOW STARTING POINT...HIGHS WILL STAY WELL BELOW AVERAGE SUNDAY. THE NEXT WEAK WAVE ARRIVES MONDAY MORNING SPREADING CLOUDS AND LIGHT SNOW BACK ACROSS THE FORECAST AREA. AN INCREASE OF CLOUD COVER AND RELATIVELY WARMER AIR SURGING NORTHWARD WILL KEEP LOWS FROM BOTTOMING OUT MONDAY MORNING. TAX && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... A DIGGING TROUGH WILL DEEPEN A SURFACE LOW NEAR THE LOWER MISSISSIPPI VALLEY MONDAY. STRONG SUPPORT FROM THE UPPER-LEVEL JET WILL DEEPEN THE LOW FURTHER AS IT ADVANCES THROUGH THE SOUTHEASTERN CONUS MONDAY AFTERNOON. INCREASED SOUTHERLY FLOW WILL TAP INTO GULF AND ATLANTIC MOISTURE...SPREADING IT NORTHWARD INTO OUR REGION AND EAST. STRONG ISENTROPIC ASCENT WILL BRING PRECIPITATION THROUGH AT LEAST OUR EASTERN ZONES BY LATE MONDAY INTO TUESDAY MORNING. STILL QUESTIONS SURROUNDING THE EXACT TRACK OF THE LOW AND THE RESULTANT WESTWARD EDGE OF PRECIPITATION...PRECIPITATION TYPE...AND INTENSITY. AS OF THE 00Z RUNS...GUIDANCE IS FAIRLY CONSISTENT ACROSS THE MODEL SUITE...BUT ALL HAVE NUDGED THE SURFACE LOW WEST OF THEIR POSITION 24HRS AGO. CURRENT FORECAST CALLS FOR LIKELY SNOW TUESDAY MORNING REACHING WEST TO THE OHIO RIVER INCLUDING PITTSBURGH. SIGNIFICANT MODEL SPREAD DOES EXIST FOR HIGH TEMPERATURE VALUES TUESDAY...AND WITH THE WESTWARD TREND...HAVE BUMPED UP HIGHS A FEW DEGREES. THIS WOULD FAVOR AT LEAST SOME MIX OF RAIN/SNOW TUESDAY AFTERNOON THAT COULD ULTIMATELY CUT INTO THE POTENTIAL FOR ACCUMULATING SNOW. BEHIND THIS SYSTEM...THE BROAD UPPER TROUGH WILL BRIEFLY RE-ESTABLISH OVER THE NORTHEAST. TEMPERATURES WILL INITIALLY DROP BELOW AVERAGE THURSDAY...BEFORE REBOUNDING WITH WARM AIR ADVECTION BY THE WEEKEND. TAX && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... VFR CONDITIONS WILL CONTINUE THROUGH THE MORNING BEFORE THE NEXT SYSTEM BRINGS ANOTHER ROUND OF SNOW AND FLIGHT RESTRICTIONS THIS AFTERNOON/EVENING. GUSTY NORTHWEST WINDS WILL COMMENCE BY EVENING AS A COLD FRONT MOVES THROUGH THE AREA WITH A BURST OF SNOW SHOWERS ALONG IT. .OUTLOOK.../FRIDAY NIGHT THROUGH TUESDAY/... RESTRICTIONS WILL BE POSSIBLE IN SNOW SHOWERS LATER FRIDAY INTO SATURDAY. THE NEXT CHANCE FOR WIDESPREAD IFR WILL BE WITH LOW PRESSURE MONDAY AND TUESDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 10 AM EST SATURDAY FOR MDZ001. WIND CHILL WATCH FROM MIDNIGHT EST TONIGHT THROUGH SUNDAY MORNING 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 FROM 7 PM THIS EVENING TO 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>513. WINTER WEATHER ADVISORY FROM 4 PM THIS AFTERNOON TO 10 AM EST SATURDAY FOR WVZ512>514. WIND CHILL WATCH FROM MIDNIGHT EST TONIGHT THROUGH SUNDAY MORNING FOR WVZ514. && $$

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