Area Forecast Discussion
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000 FXUS61 KPBZ 270215 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 915 PM EST MON JAN 26 2015 .SYNOPSIS... LIGHT TO OCCASIONALLY MODERATE SNOW WILL SHIFT EASTWARD TONIGHT AS LOW PRESSURE DEVELOPS TOWARD THE COAST. && .NEAR TERM /THROUGH TUESDAY/... GFS AND NAM SOLUTIONS CONTINUE START TO EDGE THE 850-600 MB DEFORMATION FIELD OVER WESTERN PENNSYLVANIA EASTWARD OVERNIGHT...AND THIS SEEMS TO ALREADY BE MANIFEST IN RADAR AND SATELLITE ENHANCEMENT SIGNATURES. AS THIS OCCURS...HOWEVER...COLD ADVECTION LOOKS TO RAPIDLY BE BRINGING 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 FROM WHAT WE AR SEEING AT THE MOMENT. HOWEVER...GIVEN THAT QPF SHOULD BECOME MUCH LIGHTER OTHER THAN IN THE UPSLOPE AREAS SUCH AS THE RIDGES...ACCUMULATIONS SHOULD SLOW DOWN TREMENDOUSLY OVERNIGHT. GIVEN THE EROSION OF LARGE SCALE LIFT IN THE NON-UPSLOPE AREAS...THE WINTER WEATHER ADVISORIES WERE CANCELED FOR ALL BUT THE EASTERN FRONTIER OF THE CWA. THIS INCLUDES THE RIDGES AS WELL AS FOREST...JEFFERSON...AND INDIANA COUNTY...WHICH ALL REMAIN ON THE CUSP OF THE INTERFACE WITH LARGER SCALE LIFT THAT STILL REMAINS RESIDENT OVER CENTRAL PENNSYLVANIA. ADDITIONALLY...AS UPSLOPE FLOW INCREASES AND DENDRITIC GROWTH MAXIMIZES OVERNIGHT...INCREASINGLY EFFICIENT SNOW SHOWERS IN THE RIDGES SHOULD ALLOW FOR A CONTINUATION OF ACCUMULATION...EVEN AS THE SATURATED LAYER IS EVISCERATED. 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 && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... 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. && .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 /02Z TUESDAY THROUGH SATURDAY/... SLOWLY SEEING IMPROVEMENT FROM IFR THIS EVENING AS THE BACK EDGE OF THE SNOW GRADUALLY SHIFTS EASTWARD. BACK EDGE...CURRENTLY ON A LINE FROM NEAR KFKL TO NEAR KPIT WILL TAKE 6-9 HRS TO CLEAR THE ERN TERMINALS OF DUJ AND LBE. ALL TERMINALS WEST OF THE SNOW WILL HOLD WITH LOW END MVFR CIGS THROUGH THE OVERNIGHT AND INTO TUES. WINDS WILL GRADUALLY SHIFT WSW TUES AND REMAIN LIGHT. TAX .OUTLOOK.../TUESDAY THROUGH FRIDAY/... THE NEXT CHANCE FOR WIDESPREAD RESTRICTIONS IS EXPECTED ON THURSDAY AND FRIDAY WITH CROSSING LOW PRESSURE. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...WINTER WEATHER ADVISORY UNTIL 7 AM EST TUESDAY FOR MDZ001. OH...NONE. PA...WINTER WEATHER ADVISORY UNTIL 7 AM EST TUESDAY FOR PAZ009-016- 023-074-076. WV...WINTER WEATHER ADVISORY UNTIL 7 AM EST TUESDAY FOR WVZ023-041. && $$

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