Area Forecast Discussion
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000 FXUS61 KPBZ 181422 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 922 AM EST THU DEC 18 2014 .SYNOPSIS...
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A WEAK DISTURBANCE WILL CROSS THE REGION THIS EVENING...FOLLOWED BY BUILDING HIGH PRESSURE FRIDAY.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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CLDS WL CONT TDA WITH MRNG RAOBS SHOWING LLVL MSTR TRAPPED BLO A TEMP INVERSION. A FEW FLURRIES OR LGT SNW SHWRS ARE PSBL...BUT WITH THE SHALLOW MSTR LYR NOTHING SGFNT IS EXPD. TEMPS SHOULD AVG A FEW DEG BLO THE SEASONAL AVG.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/...
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A WK SHRTWV IS PROGGED TO ADVN ACRS THE RGN TNGT. WITH THE CONTD LLVL MSTR AND TEMP INVERSION JUST SCT FLURRIES ARE EXPD...THOUGH A FEW LGT ACCUMULATING SNW SHWRS ARE PSBL WITH SOME LTD LK AND TERRAIN ENHANCEMENT N OF I 80 AND IN THE RIDGES. BLDG HIGH PRES SHOULD END ANY RMNG SNW SHWRS AND FLURRIES FRI MRNG...THOUGH INVERSION TRAPPED LLVL MSTR SHOULD KEEP CLDS ACRS THE RGN. A SHRTWV ACRS THE SERN CONUS IS PROGGED TO BRING LOW CHCS FOR LGT SNW WELL SE OF PIT LT SAT...THOUGH MDLS CONT TO TREND FURTHER S WITH PCPN FM THIS SYSTEM. TEMPS SHOULD AVG A LTL BLO THE SEASONAL AVGS.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/... THE LONGWAVE PATTERN WILL BECOME MORE MERIDIONAL SUNDAY THROUGH THE FIRST HALF OF NEXT WEEK AS A TROUGH OF LOW PRESSURE DIGS SOUTH OVER THE CENTRAL US AND DEEPENS AS IT TRANSITIONS EASTWARD. LATEST GUIDANCE SHOWS GOOD CONTINUITY WITH THIS FEATURE AND OVERALL ARE IN FAIRLY GOOD AGREEMENT. WITH THAT AND LATEST RMOP AND MODTRENDS VERY SIMILAR TO 24HRS AGO...OPTED TO ADJUST THE EXTENDED TO BE MORE IN LINE WITH A BLEND OF THE 00Z WPC...EC...AND GEFS....WHICH RESULTED IN A FAIRLY BIG INCREASE IN BOTH LOW AND MAX TEMPERATURES TOWARDS THE MIDDLE OF THE WEEK WITH HIGHER CONFIDENCE IN TIMING. CURRENTLY...THE BRUNT OF PRECIPITATION LOOKS TO FALL OVERNIGHT TUESDAY THROUGH WEDNESDAY MORNING AS RAIN AHEAD OF THE COLD FRONT UNDER STRONG WAA AND MOISTURE ADVECTION...WITH LATEST ENSEMBLE GUIDANCE INDICATING V-COMPONENT ANOMALIES BY TUESDAY AFTERNOON AROUND 2 STANDARD DEVIATIONS ABOVE NORMAL. TEMPERATURES ARE FORECAST TO BE AROUND 10 DEGREES ABOVE NORMAL BY TUESDAY AFTERNOON...AND STAYING RELATIVELY WARM TUESDAY NIGHT AS STRONGER SOUTHWEST SURFACE WINDS AHEAD OF THE SYSTEM KEEPS STRONG WAA IN PLAY AND THE LOWER LEVELS MIXED. WHILE THE FINER DETAILS CERTAINLY COULD CHANGE...LATEST MODEL PROGS SHOW COLD AIR BEHIND THE FRONT FULLY INTO THE FORECAST AREA BY CHRISTMAS MORNING AT WHICH TIME ALL PRECIPITATION WOULD CHANGEOVER TO SNOW. CHANGEOVER SHOULD HAPPEN RELATIVELY QUICKLY...BUT THERE IS SOME UNCERTAINTY ON HOW LONG WE MAY SEE MIXED PRECIPITATION BASED ON LATEST PROGGED CRITICAL THICKNESSES. IN GENERAL...CURRENTLY AROUND ONE HALF INCH OF LIQUID PRECIPITATION IS EXPECTED AT THIS TIME AHEAD OF THE COLD FRONT WITH LIGHT SNOWFALL ON THE BACKSIDE. NOMADS REANALYSIS BASED ON THE LATEST 00Z RUN GIVES AROUND A 50 PERCENT CHANCE OF AN INCH OR SO OF SNOW FALLING ON THE BACKSIDE OF THE FRONT THE NIGHT OF THE 24TH AND INTO THE 25TH. && .AVIATION /14Z THURSDAY THROUGH MONDAY/...
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A PERSISTENT LOW LEVEL DECK OF STRATOCUMULUS WILL KEEP SITES UNDER MVFR CIG RESTRICTIONS THROUGH THE MORNING...WITH SITES SOUTH OF INTERSTATE 80 OCCASIONALLY IMPROVING TO VFR. THERE IS A SLIGHT CHANCE SITES NORTH OF INTERSTATE 80 MAY BRIEFLY SEE IFR AT TIMES WITH OCCASIONAL LIGHT FLURRIES. OUTLOOK.../TONIGHT THROUGH MONDAY/... PERIODIC CIG RESTRICTIONS WILL CONTINUE UNTIL BOUNDARY LAYER FLOW BACKS TO THE SOUTHWEST ON SATURDAY AHEAD OF AN APPROACHING MID- LEVEL TROUGH OF LOW PRESSURE.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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