Area Forecast Discussion
Issued by NWS

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000 FXUS61 KPBZ 291351 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 851 AM EST THU JAN 29 2015 .SYNOPSIS... CROSSING LOW PRESSURE WILL BRING A WINTRY MIX OF PRECIPITATION TO THE UPPER OHIO REGION TODAY AND SNOW EARLY ON FRIDAY. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... QUICK UPDT TO EXPAND THE FRZG RAIN ADVY ACRS MUCH OF THE AREA WITH AN APCHG SHRTWV AND CDFNT. PCPN IS ALREADY IN THE OH COUNTIES MOVG E...AND SHOULD RCH THE AREA THRU THE REST OF THE MRNG/ERLY AFTN. AIR TEMPS WL BE RISING...THOUGH LOW DEW PTS SHOULD RESULT IN SOME WET BULBING LIMITING THAT RISE. WITH RECENT COLD WEA ROAD TEMPS ARE BLO FRZG AND WL LIKELY RMN THERE INTO ERLY AFTN...EVEN IF AIR TEMPS CLIMB JUST ABV FRZG. FURTHER N AND IN THE RIDGES...CONTD WITH WINTER WEA ADVYS AS THUICKNESSES/SOUNDING PROFILES INDICATE PCPN WL LIKELY BE A MIX OF SNW AND FRZG RAIN. NUDGED TEMPS TO THE LATEST LAMP AND NAM NMBRS. && .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... THERMAL PROFILES QUICKLY BECOME MORE UNSTABLE TONIGHT. COLD ADVECTION BEGINS IN EARNEST ALOFT AS TWO SHORT WAVE TROUGHS ARE SET TO CROSS THE AREA THROUGH FRIDAY MORNING. THIS WILL OCCUR SIMULTANEOUSLY TO THE DRIER AIR COMING IN...HOWEVER THE DENDRITIC GROWTH LAYER LOOKS TO CRASH TOWARD THE SURFACE TONIGHT IN THE RIDGES...WELL BEFORE THE MOISTURE PEELS OFF. CONSENSUS SNOW TO LIQUID RATIOS FROM THE NAM AND GFS VIA BUFKIT SUGGEST AROUND 25 TO 1 BEGIN OVERNIGHT. GIVEN INSTABILITY AND UNIDIRECTIONAL UPSLOPE...THIS SHOULD RESULT IN VERY EFFICIENT SNOW GROWTH. MODEL QPF IS GENERALLY ONLY A COUPLE OF TENTHS...AND GIVEN ICE COVER UPSTREAM ON LAKE ERIE...A TON OF QPF IS VERY UNLIKELY. HOWEVER...EVEN LIGHT QPF IN THIS CASE IS LIKELY TO ADD UP TO SEVERAL INCHES OF SNOW. GIVEN THAT AHEAD OF THE SYSTEM ON THURSDAY THERE COULD BE AN INCH OR SO IN SOME OF THE SHELTERED HIGHER ELEVATIONS...AND ANOTHER 2 TO 5 SEEM LIKELY IN THE UPSLOPE THROUGH FRIDAY WITH ADDITIONAL SYNOPTIC HELP VIA TWO ADDITIONAL WAVES CROSSING THE AREA...3 TO 6 INCH TOTALS SEEM REASONABLE IN THE RIDGES BY FRIDAY MORNING. WINTER WEATHER ADVISORIES WERE EXPANDED TO ACCOMMODATE THIS. && .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/... HIGH LEVELS OF UNCERTAINTY IN THE LONG TERM PARTICULARLY WITH THE SYSTEM THAT COULD AFFECT THE AREA DURING THE SUNDAY/MONDAY TIME FRAME. FOR NOW...CONSISTENCY WILL BE THE NAME OF THE GAME UNTIL THE MODELS PROVIDE A BETTER PICTURE. COLD PATTERN WILL CONTINUE THROUGH THE REMAINDER OF THE LONG TERM. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... HANGING ON TO VFR CONDITIONS AT THE START OF THE TAF PERIOD WITH MID CLOUDS INVADING...BUT THIS WILL START TO CHANGE SOON. PRECIPITATION BEGINS TO MOVE IN AFTER 14Z ASSOCIATED WITH GREAT LAKES LOW. STILL LOOKING AT BEST FZRA POSSIBILITIES AT ZZV...FKL...AND DUJ. STILL CANNOT RULE OUT BRIEF PERIOD OF FZRA AT HLG AND PIT/AGC...BUT STILL UNCERTAIN ENOUGH TO NOT INCLUDE YET. OTHERWISE...RA OR A RA/SN MIX. FLIGHT CONDITIONS WILL DETERIORATE THROUGH MVFR LATER THIS MORNING/MIDDAY TO IFR DURING THE AFTERNOON. COLD FRONT SWEEPS THROUGH AFTER 00Z CHANGING ALL PRECIP TO SNOW WITH CONTINUED IFR CONDITIONS...WITH ZZV/MGW CLINGING TO MVFR. SLIGHT IMPROVEMENT TOWARDS 12Z AT WESTERN TERMINALS AS MORE OF A NW FLOW/UPSLOPE PATTERN TAKES HOLD. CL .OUTLOOK.../THURSDAY NIGHT THROUGH MONDAY/... RESTRICTIONS WILL CONTINUE THROUGH FRIDAY MORNING...WITH IMPROVEMENT DURING THE AFTERNOON. NEXT CHANCE OF WIDESPREAD RESTRICTIONS ARRIVES SUNDAY WITH NEXT STORM SYSTEM. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER WEATHER ADVISORY UNTIL 10 AM EST FRIDAY FOR MDZ001. OH...FREEZING RAIN ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR OHZ039>041-048>050-057>059-068-069. PA...WINTER WEATHER ADVISORY UNTIL 10 AM EST FRIDAY FOR PAZ007>009- 015-016-023-074-076. FREEZING RAIN ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR PAZ013-014-020>022-029-031-073-075. WV...FREEZING RAIN ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR WVZ001>004-012. WINTER WEATHER ADVISORY UNTIL 10 AM EST FRIDAY FOR WVZ023-041. FREEZING RAIN ADVISORY UNTIL 4 PM EST THIS AFTERNOON FOR WVZ021-022. && $$

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