Area Forecast Discussion
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000 FXUS61 KPBZ 121337 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 937 AM EDT FRI SEP 12 2014 .SYNOPSIS... COOL WEATHER WILL CARRY THROUGH MUCH OF THE NEXT SEVEN DAYS. LOW PRESSURE PASSING SATURDAY BRINGS THE CHANCE FOR SHOWERS...OUTSIDE EASTERN OHIO. AFTER A PERIOD OF DRY WEATHER THANKS TO HIGH PRESSURE...THE NEXT COLD FRONT IS PREDICTED TO CROSS TUESDAY INTO WEDNESDAY. && .NEAR TERM /THROUGH TONIGHT/...
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930 AM UPDATE...MINOR CHANGES TO SKY AND TEMPERATURE GRIDS. DESPITE THIN NATURE TO CLOUD DECK AS NOTED VISUALLY AND BY 12Z SOUNDING...MODELS INSIST ON HOLDING THE INVERSION FIRMLY INTO THE AFTERNOON. DID REDUCE SKY GRIDS SLIGHTLY BUT HOLDING ON TO MOSTLY CLOUDY WORDING FOR MOST PART. SLIGHT BUMP UP IN TEMPERATURES AS WELL...BUT STILL BELOW WHAT LAMP WOULD SUGGEST. PREVIOUS DISCUSSION... BUFR SOUNDINGS DO NOT GIVE A LOT OF HOPE TO A SUNNY FRIDAY. THERE IS A FAIRLY STRONG LOW LEVEL INVERSION AROUND 5KFT WHICH PERSISTS INTO EARLY AFTERNOON...BEFORE ENOUGH MIXING TURNS OVER THE BL. CONTINUED WITH PREVIOUS FORECAST THINKING OF PLAYING CLOUDS UNTIL LUNCH TIME THEN BREAK THEM UP FROM EAST TO WEST. BASED ON THE ELROD TECHNIQUE...WOULD EXPECT PARTIAL CLEARING TO OCCUR IN THE MOUNTAINS FIRST...WHILE POCKETS OF BINOVC DEVELOP ELSEWHERE. PATCHY DRIZZLE THIS MORNING WILL SHUT OFF BY MID MORNING. A CHALLENGING CLOUD FORECAST LEADS TO A TEMPERATURE FORECAST THAT COULD GO EITHER WAY. FOR NOW...STILL RESIDE ON THE COOLER ENVELOP OF GUIDANCE WITH WIDESPREAD 60S. LOWER 70S ARE PROJECTED SOUTH OF THE MASON DIXON LINE. THIS CONCURS WITH THE LATEST NAM12BC GRIDS. IF CLOUDS BREAK UP SOONER THEN 70S WILL BE WIDESPREAD GIVEN H8 TEMPS AROUND 12C. EASTERLY FLOW DEVELOPS TONIGHT ALLOWING ADVECTION OF DRIER AIR INTO THE REGION. ANY STRATUS SHOULD BE GONE BY SUNSET...BUT WILL SET THE STAGE FOR A BRIEF PERIOD OF FOG...HOWEVER WITH MID AND UPPER LEVEL MOISTURE ARRIVING FROM THE SW...ANY FOG WILL BE SHORT LIVED. SURFACE TROUGH SETS UP ON THE WINDWARD SIDE OF APPALACHIANS TONIGHT. THIS WILL BE A FOCUS MECHANISM FOR POOLING OF LLVL MOISTURE AS A WAVE OF LOW PRESSURE BEGINS TO RIDE UP THE MTNS. THE MID LVL TROUGH RESIDES ACROSS IL AND IND...THUS DO NOT EXPECT ANY MEASURABLE PCPN OUTSIDE THE FAR SERN PART OF FCST AREA...WHERE CHANCE NUMBERS WERE MAINTAINED. DID BUMP POPS INTO THE LIKELY RANGE FOR THE NRN WV MTNS TOWARD DAYBREAK SAT GIVEN STRONGER CONVERGENCE IN THE LOWEST 10KFT.
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&& .SHORT TERM /SATURDAY THROUGH MONDAY/... A FAIRLY VIGOROUS SHRTWV IS PROGGED TO ADVN ACRS THE GREAT LAKES AND INTERACT WITH MSTR FOCUSED VIA AN INVERTED TROF ACRS WV AND THE SW CORNER OF PA ON FRIDAY NGT AND EARLY SATURDAY. GIVEN MDL CONSISTENCY...HAVE BUMPED POPS TO LIKELY GENLY ALNG AND EAST OF I 79 FOR THE FIRST HALF OF SATURDAY. THAT SYSTEM IS FORECAST TO SHIFT QUICKLY EWD BY SAT AFTN WITH CDFNT PASSAGE AND HIGH PRES BLDG AND SUPPRESSING PCPN FOR SUNDAY AND MONDAY. TEMPS UNDR THIS PTN ARE EXPECTED TO AVG SVRL DEGS UNDR THE AVGS...AND WERE FORECAST USING PERSISTENCE TWEAKED WITH THE LATEST GFS MOS TRENDS. && .LONG TERM /MONDAY NIGHT THROUGH THURSDAY/... ANOTHER SHRTWV IS EXPECTED TO SPAWN SHWRS MONDAY NGT AND EARLY TUES. SFC HIGH PRES...UNDR BROAD ERN CONUS TROFG...IS THEN FORECAST TO MAINTAIN DRY...BUT SEASONABLY COOL WEATHER FOR THE RMNDR OF THE LONG TERM PD. LONG TERM TEMPS WERE FORECAST USING HPC GUIDANCE...TWEAKED UPWARD VIA GFS MOS TRENDS. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... WIDESPREAD MVFR CLOUDS WITH POCKETS OF IFR STRATUS BLANKET THE REGION IN A MOIST NRLY FLOW. POCKETS OF DRIZZLE AND PATCHY FOG ARE LARGELY CONFINED TO THE RIDGES. BKN-OVC CIGS WILL BE AROUND FOR MUCH OF THE DAY AS LOW LEVEL INVERSION HANGS TOUGH AROUND 5KFT. CONTINUED TO STRESS PARTIAL CLEARING IN THE AFTERNOON HOURS AT ALL AIRPORTS...WITH VFR WX RETURNING BETWEEN 20Z-24Z. DUE TO THE LATE DEPARTURE OF STRATUS / STRATOCU...LOOK FOR MVFR VIS RESTRICTIONS AT MORE FAVORABLE SPOTS OF ZZV AND BVI TO DEVELOP BEFORE 06Z. ANY FG SHOULD BE BRIEF DUE TO ARRIVAL OF MID LVL MSTR FROM THE SW. THE ONSET TIME OF VFR CIGS COULD BE LATER THAN FORECAST IF ENOUGH MIXING IN THE BL DOES NOT OCCUR LATER TODAY. CIGS RETURN TO JUST ABOVE MVFR LEVELS AFTER 6Z FROM S TO N. OUTLOOK...THURSDAY NIGHT THROUGH SUNDAY... MVFR RESTRICTIONS ARE EXPECTED SATURDAY...ESPECIALLY AT PA TERMINALS AS PASSING LOW PRESSURE BRINGS SHOWERS. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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