Area Forecast Discussion
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000 FXUS61 KPBZ 191050 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 550 AM EST FRI DEC 19 2014 .SYNOPSIS...
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BUILDING HIGH PRESSURE IS EXPECTED THROUGH THE WEEKEND...THOUGH CLOUDS WILL REMAIN.
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&& .NEAR TERM /THROUGH TONIGHT/...
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MOISTURE TRAPPED UNDER THE INVERSION NEAR H85 CONTINUES TO FALL OUT AS FREEZING DRIZZLE MIXING AT TIMES WITH LIGHT SNOW. BEGINNING TO SEE SOME REPORTS IN THE PITTSBURGH METRO AREA...AND FURTHER SOUTH AND WEST INTO ERN OHIO. HAVE EXPANDED THE WINTER WEATHER ADVISORY TO INCLUDE THIS AREA. THE BULK OF THIS ACTIVITY REMAINS JUST WEST OF THE CWA BOUNDARY WHERE MOISTURE AVAILABILITY IS A LITTLE BETTER DUE TO THE PROXIMITY TO LAKE ERIE. RECENT RADAR TRENDS SHOW A LAKE-ENHANCED BAND NEAR CLE DISLODGE ITSELF FROM THE SRN SHORELINE OF LAKE ERIE. THIS IS IN RESPONSE TO THE WINDS VEERING TO NEARLY NORTHERLY AS THE LLVL SW TROF AXIS SWINGS SOUTHWARD. WHILE THE INDIVIDUAL BAND IS NOT EXPECTED TO IMPACT OUR AREA DIRECTLY...IT CAN BE USED AS A GOOD PROXY FOR WHERE THE DOWNSTREAM MOISTURE IS ENTERING OUR FORECAST AREA. AS THIS BAND CONTINUES TO PIVOT SOUTHWARD...EXPECT TO SEE LIGHT SNOW AND FREEZING DRIZZLE REPORTS IN OUR AREA TO FOLLOW SUIT. THE HI-RES MODELS DID A GREAT JOB HANDLING THE LLVL MOISTURE AND PROGRESSION OF THE TROF...KEYING IN ON THE ATTENDANT MID-LEVEL DEFORMATION ZONE TO GENERATE SHOWER ACTIVITY. AS IT CONTINUES IT TREK SOUTH OF LAKE ERIE...THE MOISTURE BEGINS TO ERODE ALONG WITH THE DEFORMATION ZONE GETTING WASHED OUT. WITH STILL ABUNDANT LLVL MOISTURE AVAILABLE...WOULD EXPECT REPORTS OF DZ TO CONTINUE THROUGH SUNRISE...BUT NOT MUCH BEYOND THAT. HAVE EXTENDED THE ADVISORY THROUGH 9AM. CLOUDS WILL CONTINUE TO PLAGUE THE CWA FOR YET ANOTHER DAY KEEPING DAYTIME HIGHS IN CHECK. INCREASING SUBSIDENCE UNDER HIGH PRESSURE WILL GRADUALLY LOWER INVERSION HEIGHTS THROUGH THE DAY FRIDAY SQUASHING REMAINING PRECIPITATION CHANCES. TAX
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
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HIGH PRESSURE WILL REIGN OVER THE FORECAST AREA THROUGH THE WEEKEND. A WEAK OPEN WAVE TRIES TO SKIRT THE SRN EXTENT OF THE SFC HIGH SAT AFTERNOON...BUT MODELS CONTINUE TO TREND IT FURTHER SOUTH WELL OUT OF OUR REGION. AFTER LARGELY ZONAL FLOW ALOFT THROUGH SUNDAY THE UPPER LEVEL PATTERN FAVORS SWRLY FLOW ON THE BACKSIDE OF THE SFC HIGH. THIS WILL WORK TO DRIVE WARMER TEMPS INTO THE FORECAST AREA WITH HIGHS DRIVING ABOVE AVERAGE HEADING INTO EARLY NEXT WEEK. TAX
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&& .LONG TERM /MONDAY THROUGH THURSDAY/... WHILE THE MODELS AGREE ON A DEEPENING UPPER LEVEL TROUGH TO CLOSE OFF OVER THE GREAT LAKES THROUGH THE PERIOD THE DETAILS OF HOW THIS EXACTLY UNFOLDS WILL BE CRITICAL. BY MONDAY SOUTHERN STREAM SHORTWAVE AHEAD OF MAIN NORTHERN STREAM UPPER TROUGH DIGGING INTO THE NORTHERN PLAINS WILL PRODUCE LOW PRESSURE ACROSS THE CAROLINAS MOVING OFF SHORE OF THE EAST COAST. THE SOUTHEAST RIDGES MAY BE BRUSHED BY LIGHT RAIN FROM THIS SYSTEM. NEXT UP IS DEEPENING LOW PRESSURE OVER THE OHIO VALLEY AHEAD OF SHARPLY DIGGING UPPER TROUGH AND CLOSED LOW MOVING INTO THE WESTERN GREAT LAKES. UPPER OHIO VALLEY LOOKS TO BE ON THE WARM SIDE OF THE SYSTEM TUESDAY INTO WEDNESDAY WITH RAIN...FOLLOWED BY STRONG COLD FRONT AND COLD ADVECTION LATER WEDNESDAY NIGHT AND THURSDAY WITH SNOW SHOWERS. WITH SUCH A STRONG SYSTEM ALOFT AND FAST DEEPENING LOW PRESSURE AT THE SURFACE TIMING OF COLD AIR AND EXACT TRACK WILL LIKELY CHANGE AS WE GET CLOSER TO CHRISTMAS. ALL IN ALL PREVIOUS FORECAST IS LITTLE CHANGED WITH ONLY MINOR ADJUSTMENTS BASED ON NEWEST WPC EXTENDED PROGS. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... UPDATED TAFS TO INCLUDE MENTION OF FREEZING DRIZZLE FOR SITES NORTH OF INTERSTATE 70 THROUGH EARLY THIS MORNING BASED ON LATEST OBS AND LATEST HI RES AND RAPID REFRESH GUIDANCE SHOWING INDICATING MOISTURE IN THE COLUMN LIMITED TO LOWER LEVELS NOT COLD ENOUGH FOR ICE CRYSTAL FORMATION...THUS...FINE MIST AND LIGHT DRIZZLE EXPECTED THROUGH 9AM WILL REMAIN LIQUID AND FREEZE ON CONTACT. DO NOT EXPECT ANY PERIODS OF RAPID ICE DEVELOPMENT BUT WILL LIKELY FOR A LIGHT GLAZE OVER THE NEXT SEVERAL HOURS. ICE POTENTIAL WILL LIKELY BE OVER BY MID MORNING AS MOISTURE POOL BECOMES TOO SHALLOW...WITH CIG RESTRICTIONS LARGELY MVFR THROUGH MUCH OF THE DAY...IMPROVING TO VFR STARTING LATE THIS AFTERNOON. OUTLOOK.../FRIDAY NIGHT THROUGH TUESDAY/... STRATUS AND RESTRICTIONS MAY PERSIST INTO THE WEEKEND. NEXT STORM SYSTEM WILL BRING RESTRICTIONS TUESDAY. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...WINTER WEATHER ADVISORY UNTIL 9 AM EST THIS MORNING FOR OHZ039>041-048>050. PA...WINTER WEATHER ADVISORY UNTIL 9 AM EST THIS MORNING FOR PAZ007>009-013>016-020>022. WV...WINTER WEATHER ADVISORY UNTIL 9 AM EST THIS MORNING FOR WVZ001. && $$

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