943
FXUS61 KPBZ 191227
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
727 AM EST TUE NOV 19 2024
SYNOPSIS
A WARM FRONT WILL BRING THE RISK FOR SHOWERS TODAY. LOW PRESSURE
WILL KEEP IN THE RISK FOR SHOWERS ON WEDNESDAY AND BRING MUCH
COLDER AIR TO THE REGION ON THURSDAY. SNOW IS POSSIBLE THURSDAY
AND FRIDAY, WITH SIGNIFICANT SNOW A RISK IN THE HIGHER
ELEVATIONS.
NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:
- SLIGHTLY WARMER TEMPERATURES AND THE RISK FOR SHOWERS RETURNS.
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UPDATE (725 AM)...
QUICK UPDATE TO ALIGN TEMPERATURES WITH LATEST OBSERVATIONAL
TRENDS AND ALSO SLIGHTLY BUMP UP ONSET TIME OF PRECIPITATION IN
SE OH COUNTIES. OTHERWISE, THE FORECAST IS IN GOOD SHAPE.
PREVIOUS DISCUSSION FOLLOWS...
PREVIOUS...
BRIEF HEIGHT RISES ARE EXPECTED THIS MORNING BEFORE A SERIES OF
SHORTWAVE TROUGHS MOVE ACROSS THE REGION. THE FIRST WAVE WILL
WORK TO FLATTEN THE RIDGE AND THE SECOND WAVE WILL BRING AN
INCREASE IN DEEP MOISTURE AND THE THREAT FOR SHOWERS. MODELS ARE
SHOWING THE WAVES WEAKENING AS THE ENCOUNTER THE WEAK RIDGE.
THE STATIONARY FRONT STRETCHING ACROSS THE REGION WILL BE FORCED
NORTHWARD AS THE WAVES MOVE THROUGH. WARM AIR ADVECTION IS
EXPECTED THROUGHOUT THE DAY WHICH WILL WARM TEMPERATURES 10 TO
15 DEGREES ABOVE NORMAL.
SHOWERS WILL BEGIN TO CROSS OHIO THIS MORNING AND THEN TREK
EASTWARD THROUGHOUT THE DAY. RAINFALL COVERAGE AND INTENSITY
SHOULD WEAKEN AS THE DAY PROGRESSES. PROBABILITIES OF >0.10
INCHES GENERALLY RANGE FROM 20 TO 40% WITH SLIGHTLY HIGHER
VALUES OVER PORTIONS OF OHIO.
SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/
KEY MESSAGES:
- RAIN CHANCES CONTINUE ON WEDNESDAY.
- STRONG COLD FRONT WILL BRING MUCH COLDER AIR TO THE REGION
THURSDAY.
- CONFIDENCE INCREASING FOR SNOW ON THURSDAY, WITH IMPACTS
GREATEST OVER THE RIDGES.
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FOCUS WILL SHIFT TO A LARGE ANOMALOUS UPPER LOW THAT WILL MOVE
ACROSS THE WESTERN GREAT LAKES ON WEDNESDAY. A PIECE OF ENERGY
ROTATING AROUND THE EASTERN FLANK OF THE DEEPENING UPPER LOW
WILL CROSS OHIO WEDNESDAY AFTERNOON. THIS ENERGY WILL RAPIDLY
DEVELOP A SURFACE LOW AND IT WILL DEEPEN AS IT ROTATES NORTHWARD
THROUGH OHIO. THE STRENGTHENING SURFACE COLD FRONT ASSOCIATED
WITH THE LOW WILL DRIVE THROUGH THE AREA WEDNESDAY AFTERNOON.
RAIN SHOWERS WILL DEVELOP AHEAD OF THE FRONT AND SPREAD ACROSS
THE REGION ON WEDNESDAY. THE MOST LIKELY TIME FOR WIDESPREAD
SHOWERS WOULD BE WEDNESDAY AFTERNOON WHEN PROBABILITIES FOR
>0.10 INCHES OF RAIN INCREASES TO 40-70%. THE HIGHEST
PROBABILITIES LOOK TO BE OVER THE NORTHERN HALF OF THE REGION
AS THEY WILL LIE CLOSER TO THE PASSING LOW.
THE STRONG COLD FRONT SHOULD FINALLY CROSS THE AREA WEDNESDAY
EVENING USHERING IN MUCH COLDER AIR. WITH THE COLD FRONT BEING
QUITE POTENT, A TRANSITION TO SNOW OR A MIX OF RAIN AND SNOW IS
POSSIBLE LATE WEDNESDAY NIGHT AND THURSDAY MORNING WITH THE
HIGH TERRAIN THE MOST LIKELY LOCATION TO REMAIN ALL SNOW.
CHANCES OF EXCEEDING AN INCH BY 7PM ON THURSDAY ARE ROUGHLY
60% FOR THE RIDGE TOPS AND GENERALLY LESS THAN 20% FOR THE LOW
LANDS. LOW PROBS OF >3 INCHES ARE SHOWING UP OVER THE HIGHEST
PEAKS OF WV, BUT THESE REMAIN LESS THAN 20%.
THE COLD FRONT WILL NOT ONLY BRING PRECIPITATION AND COLDER AIR
TO THE REGION, BUT STRONG WIND GUSTS AS WELL. A TIGHTENING
SURFACE PRESSURE GRADIENT COMBINED WITH STRONG WINDS ALOFT
MIXING TO THE SURFACE IN THE COLDER ADVECTION WILL PROVIDE
GUSTY WINDS WEDNESDAY NIGHT AND THURSDAY. THE STRONGEST GUSTS
ARE MOST LIKELY ON WEDNESDAY NIGHT. DURING THIS TIME PERIOD NBM
PROBS OF GUSTS > 40MPH ARE GENERALLY 40 TO 60% WITH CLOSE TO 70%
OVER THE RIDGE TOPS OF N WV.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
KEY MESSAGES:
- INCREASING PROBABILITY OF AN IMPACTFUL WINTER STORM FOR HIGHER
TERRAIN FRIDAY AND SATURDAY ACCOMPANIED BY GUSTY WINDS.
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THE MOST LIKELY SCENARIO IS THAT THE STACKED LOW (WHICH EVOLVES
TO A SHORTWAVE PIVOTING AROUND THE TRIPLE POINT LOW), WILL ALLOW
THE MAIN FORCING FOR SNOWFALL. THE BEST TIMING FOR ARRIVAL OF
THIS WILL BE THURSDAY NIGHT THROUGH FRIDAY MORNING. THIS WILL BE
ACCOMPANIED BY A 50% TO 70% CHANCE OF MAXIMUM GUSTS EXCEEDING
45MPH FOR THE HIGHLANDS, AND A 20% TO 30% CHANCE FOR THE
LOWLANDS. THIS WILL BRING STRONG FORCING FOR SNOW IN THE RIDGES,
WITH ADIABATIC PROFILES INTO THE DGZ COMBINED WITH OROGRAPHIC
INFLUENCES. FOR THE LOWLANDS, TEMPERATURES MAY BE TOO WARM FOR
NOTABLE ACCUMULATIONS, BUT ARE POSSIBLE AT NIGHT. THIS WILL
COVER THE BEGINNING OF THE WINTER STORM WATCH. AS THIS SHORTWAVE
ROTATES AROUND THE LOW FRIDAY, IT WILL ELONGATE THE SURFACE
TROUGH AXIS AND POTENTIALLY ALLOW A SECONDARY SHORTWAVE PASSAGE
LATE FRIDAY THROUGH SATURDAY MORNING WITH NORTHWEST FLOW FILLING
IN BEHIND. THIS WILL ALLOW ADDITIONAL CHANCES OF SNOW FOR THE
RIDGES, BUT IT IS STILL A QUESTION AS TO WHETHER PRECIPITATION
WILL FALL AS RAIN OR SNOW FOR THE LOWLANDS DURING THE DAYTIME
HOURS. WIND CHANCES DROP OFF SLIGHTLY, BUT THERE IS STILL A
WIDESPREAD 60% TO 80% CHANCE OF GUSTS EXCEEDING 30MPH. THIS WILL
COVER THE END OF THE WATCH PERIOD.
THE TIMING OF THE HIGHEST RATES WILL BE TIED CLOSELY TO
SHORTWAVES, AND THE EXACT BEHAVIOR OF SHORTWAVES REMAINS LOW TO
MEDIUM PREDICTABILITY. THE TIMING OF HEAVIEST SNOWFALL RATES
WILL LIKELY BE THE MOST IMPACTFUL AFFECTS OF THIS STORM, AND WE
HAVE NOT YET REFINED THIS. FOR THIS REASON, A BROAD TIME PERIOD
REMAINS FOR THE WINTER STORM WATCH.
HERE'S THE TAKE HOME MESSAGE: A NOTABLE WINTER STORM WITH A 80%
TO 90% CHANCE OF EXCEEDING 6" IS LIKELY FOR THE HIGH TERRAIN OF
PRESTON COUNTY AND TUCKER COUNTY BETWEEN THURSDAY AND SATURDAY.
GUSTY WINDS ARE LIKELY THROUGH THE WHOLE PERIOD, WITH THE
HIGHEST GUSTS EXPECTED TO BEGIN WEDNESDAY NIGHT. CHANCES ARE
SLIGHTLY LOWER (~50%) FOR THE LOWLANDS OF PRESTON AND THE RIDGES
OF WESTMORELAND AND FAYETTE, BUT A WATCH EXPANSION MAY BE
NECESSARY SHOULD PREDICTABILITY TREND UP THERE, WHICH WILL
DEPEND ON THE TRACK OF THE STACKED LOW.
PRECIPITATION CHANCES DECREASE SUNDAY AND MONDAY AS THE LARGE
UPPER LOW RACES OUT OVER THE ATLANTIC AND A WEAK RIDGE MOVES
OVER THE UPPER OHIO VALLEY. TEMPERATURES WILL MODERATE BOTH
DAYS.
AVIATION /13Z TUESDAY THROUGH SATURDAY/
LIGHT RAIN IS EXPECTED
TO OVERSPREAD THE REGION BY THIS AFTERNOON AND EVENING AS A WARM
FRONT APPROACHES, WITH A GRADUAL LOWERING OF CIGS BACK TO MVFR.
MODEL SOUNDINGS AND MODEL ENSEMBLE PROBABILITIES INDICATE WIDESPREAD
MVFR CIGS ARE LIKELY BY EVENING AS THE FRONT LIFTS NORTHEASTWARD,
WITH ZZV, FKL AND DUJ LIKELY SEEING IFR WITH BETTER LOW LEVEL
MOISTURE IN PLACE. IFR IS ALSO LIKELY AT OTHER PORTS IN OTHER AREAS
OF WESTERN PENNSYLVANIA, ALONG THE APPALACHIANS, AND IN NORTHERN
WEST VIRGINIA.
OUTLOOK....
RESTRICTIONS AND RAIN REMAIN LIKELY TOMORROW WITH A
CROSSING COLD FRONT. CONTINUED RESTRICTIONS, GUSTY WIND, AND
RAIN/SNOW SHOWERS ARE THEN LIKELY THROUGH SATURDAY AS A SERIES OF
LOW PRESSURE SYSTEMS PERSIST ACROSS THE GREAT LAKES AND UPPER OHIO
VALLEY REGION.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH SATURDAY
EVENING FOR WVZ512>514.
SYNOPSIS...22
NEAR TERM...22/88
SHORT TERM...22
LONG TERM...22/MILCAREK
AVIATION...WM/LUPO
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