Area Forecast Discussion
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000 FXUS61 KPBZ 170952 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 452 AM EST WED DEC 17 2014 .SYNOPSIS... COLDER AIR MOVING IN FROM THE WEST WILL KEEP HIGH TEMPERATURES TODAY LOW. CLOUDS WILL REMAIN IN THE AREA THROUGH MID-WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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CURRENT RADAR IMAGERY CONTINUES TO SHOW SCATTERED WEAK ECHOES INDICATING LIGHT RAIN SHOWERS WITH SOME PATCHY DRIZZLE. THE BULK OF THE REMAINING SHOWERS SHOULD REMAIN LIGHT...AS MOISTURE ABOVE H85 BEGINS TO DRY UP. NOW THROUGH 15Z...BEFORE H85 CAA KNOCKS TEMPS DOWN TO ENOUGH TO GENERATE ICE CRYSTALS...DRIZZLE LOOKS TO BE QUITE FAVORABLE. MENTIONED PATCHY DRIZZLE THIS MORNING ACROSS THE SRN 2/3 OF THE CWA. FURTHER NORTH...THE DEEPER MOISTURE LOOKS TO HOLD THROUGH MIDDAY...SO HELD DZ/FZDZ OUT ALONG I-80. IN THE HIGHER ELEVATIONS IN THE RIDGES...TEMPS COULD DROP OFF ENOUGH TO SEE SOME LIGHT PATCHY FZDZ...BUT NOT EXPECTING WIDESPREAD OR APPRECIABLE ICING. COLDER AIR WILL CONTINUE TO INVADE THROUGH THE MORNING WITH SFC TEMPS FOLLOWING A NON-DIURNAL TREND. LATEST HRRR/LAMP HANDLE THE COLD AIR PROGRESSION WELL. OPTED FOR A BLEND OF THESE THROUGH MIDDAY...FAVORING THE MET BEYOND THAT PERIOD. TEMPS REGISTERED EARLY THIS MORNING SHOULD LARGELY STAND AS THE HIGH TEMPS TODAY. 00Z NAM SOUNDINGS CONTINUE TO LOOK EERILY SIMILAR TO LAST THURS/FRI WHERE MOISTURE GETS TRAPPED UNDER AN H85 INVERSION AND IS UNABLE TO DISLODGE FOR SOME TIME. TONIGHT THE BULK OF THE DEEP MOISTURE EXITS NORTH AS A STRONG JET TURNS THE FLOW MORE ZONAL. HI-RES NEAR TERM MODELS INDICATING A DEEPENING OF THE BL MOISTURE DUE TO INJECTION OF LAKE MOISTURE NOT FROM LAKE ERIE...BUT FROM THE SRN END OF LAKE MICHIGAN. MOISTURE UP TO H8 SHOULD BE ENOUGH TO GENERATE SNOW SHOWERS TONIGHT ACROSS THE I-80 CORRIDOR AND NORTH...ESPECIALLY AS ENHANCED COOLING IN THE MID-LEVELS BRINGS THE SNOW GROWTH ZONE LOW ENOUGH TO OVERLAP THE TOP OF THE MOISTURE. STILL...OVERALL MOISTURE IS LIMITED ULTIMATELY KEEPING ANY SNOW ACCUMULATION LIGHT. TAX
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&& .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
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PERSISTENCE WILL BE THE THEME OF THE SHORT TERM FORECAST AS SNOW CHANCES WILL HOLD ACROSS THE NORTH AND CLOUDS WILL BE EVER-PRESENT. LLVL CLOUDS EXPECTED TO LAST THROUGH THE SHORT TERM AS A MID-LEVEL INVERSION TRAPS THE MOISTURE BELOW...SIMILAR TO WHAT WAS SEEN LATE LAST WEEK. AS THE GREAT LAKES SFC LOW TRANSITIONS TO A DEEPENING LOW OVER THE THE NEW ENGLAND COASTLINE ...MID-LEVEL FLOW VEERS TO THE NW SUPPORTING ADDITIONAL LLVL MOISTURE INJECTION FROM THE UPSTREAM GREAT LAKES. KEEPING AT LEAST A CHC OF SNOW SHOWERS ACROSS THE NORTH THURS AS LAKE MOISTURE IS SQUEEZED OUT OVER OUR NRN TIER OF COUNTIES. SHOWERS MAY DWINDLE AT TIMES THROUGH THE EVENING HOURS...BUT ARE EXPECTED TO RE-INVIGORATE DURING THE OVERNIGHT HOURS INTO EARLY FRI MORNING AS ANOTHER WEAK SW STREAMS THROUGH. OUTSIDE OF THE LAKE EFFECT AREAS...PRECIPITATION SHOULD LARGELY REMAIN OUT OF THE FORECAST WITH INSUFFICIENT MOISTURE PROGGED. MODELS HAVE HINTED AT A WEAK WAVE CROSSING OUR SRN ZONES EARLY FRI MORNING...WITH THE 00Z NAM BULLISH ON THIS FEATURE. DECIDED TO HANG WITH ALL OF THE OTHER GUIDANCE WHICH KEEPS THE SOUTH AND WEST ZONES DRY...BUT CLOUDY. TAX
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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A SOUTHERN STREAM MID-LEVEL TROUGH WILL QUICKLY MIGRATE EAST AND BRUSH ACROSS THE SOUTHERN EDGE OF THE FORECAST AREA ON SATURDAY WITH THE BEST CHANCES OF ANY PRECIPITATION ON SATURDAY EVENING AND OVERNIGHT ACROSS SOUTHERN AND EASTERN PORTIONS OF THE FORECAST AREA. ANY PRECIP SHOULD FALL IN THE FORM OF SNOW...BUT OVERALL AMOUNTS WILL BE LIGHT AS FORCING LOOKS TO BE RELATIVELY WEAK AND IN TEMPERATURES NOT FAVORABLE FOR SIGNIFICANT SNOW GROWTH. DRY CONDITIONS THEN EXPECTED SUNDAY AFTERNOON AND INTO THE BEGINNING OF NEXT WEEK AS THE LONGWAVE PATTERN AMPLIFIES AND AN UPPER TROUGH DEEPENS ACROSS THE EASTERN CONUS. MODELS HAVE SHOWN DECENT CONTINUITY WITH THIS FEATURE AND ANTICIPATE ABOVE NORMAL TEMPERATURES DURING THE FIRST HALF OF NEXT WEEK AS WAA RAMPS UP AHEAD OF THE TROUGH UNDER STRENGTHENING SOUTHWESTERLY FLOW. HAVE OPTED TO KEEP THE FORECAST DRY THROUGH EARLY TUESDAY EVENING AND INCREASE TEMPERATURES BOTH MONDAY AND TUESDAY FOR NOW BASED ON THE LATEST BLEND OF THE EC AND GEFS...AND AN OVERALL RUN TO RUN TREND AMONG MODELS IN SHOWING A DEEPER/SLOWER SOLUTION. 24HR QPF AMOUNTS AT THIS TIME BETWEEN MODELS FOR THE MIDDLE OF NEXT WEEK RANGE BETWEEN ONE HALF AND THREE QUARTERS OF AN INCH.
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&& .AVIATION /09Z WEDNESDAY THROUGH SUNDAY/... IFR CIG RESTRICTIONS EXPECTED THE MAJORITY OF THE NIGHT FOR MOST LOCATIONS WITH -RA COVERAGE DECREASING. WINDS WILL REMAIN GUSTY AT OVERNIGHT AND CONTINUE DURING THE DAY AFTER A REINFORCING SHOT OF COLD AIR MOVES THROUGH LATE THIS MORNING/EARLY AFTERNOON. GUIDANCE CONTINUES TO MAINTAIN THE HIGH MVFR/LOW VFR STRATOCU FORECAST DURING THE AFTERNOON WITH TRAPPED LOW LEVEL MOISTURE AND CONTINUED CAA. MAIN CONCERN IS THE POSSIBILITY OF FREEZING DRIZZLE AFTER TEMPERATURES FALL TO BELOW FREEZING THROUGHOUT THE COLUMN THIS AFTERNOON ACROSS THE NORTH AND LATE AFTERNOON/EARLY EVENING ACROSS SOUTHERN LOCATIONS...COUPLED WITH THE POTENTIAL THAT MOISTURE MAY NOT BE DEEP/HIGH ENOUGH FOR ICE CRYSTAL DEVELOPMENT ALOFT. FOR NOW HAVE OPTED TO REFRAIN FROM ANY MENTION OF PRECIPITATION DURING THE DAY AS ANY PRECIP WOULD LIKELY BE LIGHT FLURRIES MAINLY FOR KFKL AND KDUJ...BUT MAY NEED TO INCLUDE MENTION OF FREEZING DRIZZLE WITH THE 12Z TAF SUITE AFTER ASSESSMENT OF MORNING SOUNDINGS. OUTLOOK.../TUESDAY NIGHT THROUGH SUNDAY/... PERIODIC CIG RESTRICTIONS EXPECTED THROUGHOUT THE WEEK WITH TRAPPED LOW LEVEL MOISTURE AND CONTINUED CAA MAINTAINING STRATOCU IN THE LOWER LEVELS. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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