Area Forecast Discussion
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000 FXUS61 KPBZ 262321 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 621 PM EST MON JAN 26 2015 .SYNOPSIS...
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LIGHT TO OCCASIONALLY MODERATE SNOW WILL SHIFT EASTWARD TONIGHT AS LOW PRESSURE DEVELOPS TOWARD THE COAST.
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&& .NEAR TERM /THROUGH TUESDAY/...
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GFS AND NAM SOLUTIONS CONTINUE TO LINGER 850-600 MB DEFORMATION FIELD OVER WESTERN PENNSYLVANIA THROUGH MUCH OF THE EVENING...AND REALLY ONLY START TO EDGE IT SUBSTANTIALLY EASTWARD OVERNIGHT TOWARD MORNING. AS THIS OCCURS...HOWEVER...COLD ADVECTION SHOULD BEGIN TO START IN EARNEST...AND BRING THE DENDRITIC GROWTH LAYER DOWN TOWARD THE BOUNDARY LAYER SATURATION. THIS SHOULD SLOW DOWN THE EROSION OF RADAR COVERAGE...SO WHILE THE MECHANISM FOR SNOW GENERATION WILL BE CHANGING FROM MORE LARGE SCALE SYNOPTIC LIFT TO INSTABILITY DRIVEN SNOW SHOWERS...THE CHANGE IN REALITY IN COVERAGE MAY NOT BE THAT STARK. HOWEVER...GIVEN THAT QPF SHOULD BECOME MUCH LIGHTER OTHER THAN IN THE UPSLOPE AREAS SUCH AS THE RIDGES...ACCUMULATIONS SHOULD SLOW DOWN TREMENDOUSLY BY THE OVERNIGHT HOURS. DUE TO THE FACT THAT FLOW REMAINS FAIRLY WELL ALIGNED AND SOME INSTABILITY REMAINS IN THE BOUNDARY LAYER...SNOW SHOWERS AND FLURRIES SEEM LIKELY TO CONTINUE IN THE RIDGES INTO THE DAYTIME ON TUESDAY...HOWEVER WEAKER SATURATION AND LOWER DEWPOINTS WILL LIKELY BEING TO TAKE A TOLL EVEN ON THIS ACTIVITY BY THAT JUNCTURE. THIS SHOULD ALLOW FOR POPS TO BE ROLLED BACK BY THE DAYTIME TUESDAY A BIT. ALL THAT SAID...DUE TO THE SLOW MIGRATION OF THE WESTERN EDGE OF THE DEFORMATION FIELD THIS EVENING...WINTER WEATHER ADVISORIES FOR THE PITTSBURGH METRO AREA WERE EXTENDED UNTIL 10 PM...ALL OTHER ADVISORIES REMAIN IN EFFECT THROUGH THE NIGHT. ONE SIDE NOTE...DUE TO THE FACT THAT DAYTIME TEMPERATURES WERE AROUND FREEZING IN MANY SPOTS SOUTH OF THE TURNPIKE...WITH THE LOSS OF DAYTIME INSOLATION EVEN THOUGH IT WAS CLOUDY...MANY ROADS WILL LIKELY START TO BECOME ICY THIS EVENING. A SPECIAL WEATHER STATEMENT WAS ISSUED FOR THIS THROUGH 9 PM. PLEASE REFER TO PITSPSPBZ FOR MORE INFORMATION. FRIES
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&& .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
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SNOW SHWR POTENTIAL WL CONT TO DECLINE THROUGH TUESDAY AS HIGH PRES BLDS. A COLD WEDNESDAY MRNG WL FOLLOW WITH LOWS IN THE SINGLE DIGITS TO NR ZERO OVR NRN COUNTIES. READINGS WERE ADJUSTED FOR THE LATEST DETERMINISTIC TRENDS AND COLLABORATION. FAST MOVING LOW PRES IS PROJECTED OFF THE GREAT LAKES ON THURSDAY. CURRENT LOW TRACK ALNG I 76 SUGGESTS SUFFICIENT WARMTH OVR SRN ZONES TO PRECLUDE AN ACCUMULATING ICE OR SNOW EVENT. PROGRESSION SHOULD LIMIT ELSEWHERE. MORE ON THAT SYSTEM IN FUTURE PACKAGES.
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&& .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... MAIN CONCERN FOR THE EARLY PART OF THE LONG TERM WILL BE THE SPEED IN WHICH THE UPPER LEVEL TROUGH/CLIPPER CROSSES THE REGION. THE MOST RECENT RUN OF THE GFS SEEMS TO BE THE FASTEST...SO OPTED TO STAY CLOSER TO A BLEND OF THE ECMWF AND PREVIOUS RUNS. THIS WOULD KEEP PRECIP INTO THE EARLY PART OF FRIDAY WITH NW FLOW AND SNOW SHOWERS LINGERING INTO FRIDAY AFTERNOON. BEYOND THIS TIME PERIOD THE MODEL SOLUTIONS DIVERGE A BIT MORE AT THE SURFACE...MAKING IT HARD TO PUT ANYTHING MORE THAN CHANCE POPS IN THE FORECAST. WILL MAINTAIN AN OVERALL COOLING TREND IN TEMPERATURES AS A BROAD TROUGH REMAINS OVERHEAD THROUGH TUESDAY...WHICH IS CLOSE TO WPC FORECAST VALUES. && .AVIATION /00Z TUESDAY THROUGH SATURDAY/... AS WESTERN EDGE OF STORM MOVES TO THE EAST...IFR VISIBILITIES IN WIDESPREAD SNOW SHOULD COME TO AN END BY THE EVENING. MVFR SNOW SHOWERS WILL CONTINUE INTO THE EVENING...WITH COVERAGE DIMINISHING ENOUGH AT TERMINALS TO ONLY INCLUDE A FLURRY MENTION AFTER MIDNIGHT. WHILE MOST MODEL GUIDANCE THINKS THAT WIDESPREAD IFR CIGS WILL PERSIST OVERNIGHT...THINK THIS IS TOO PESSIMISTIC...AND HAVE GONE WITH GENERAL MVFR CIGS. EXCEPTION TO THIS IS FKL/DUJ...WHERE IFR CIGS SHOULD CONTINUE OVERNIGHT. .OUTLOOK.../TUESDAY THROUGH FRIDAY/... THE NEXT CHANCE FOR WIDESPREAD RESTRICTIONS IS EXPECTED ON THURSDAY AND FRIDAY WITH CROSSING LOW PRESSURE. && .PBZ WATCHES/WARNINGS/ADVISORIES...
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MD...WINTER WEATHER ADVISORY UNTIL 7 AM EST TUESDAY FOR MDZ001. OH...NONE. PA...WINTER WEATHER ADVISORY UNTIL 7 AM EST TUESDAY FOR PAZ007>009- 013>016-022-023-073-074-076. WINTER WEATHER ADVISORY UNTIL 10 PM EST THIS EVENING FOR PAZ020-021-029. WV...WINTER WEATHER ADVISORY UNTIL 7 AM EST TUESDAY FOR WVZ023-041.
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&& $$

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