879
FXUS61 KPBZ 201153
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
653 AM EST WED NOV 20 2024
SYNOPSIS
A STRONG COLD FRONT WILL BRING THE RISK FOR SHOWERS AND GUSTY
WINDS TO THE REGION TODAY. BEHIND THE FRONT, MUCH COLDER AIR
WILL OVERSPREAD THE AREA. A LARGE UPPER LEVEL SYSTEM WILL BRING
MORE RAIN AND SNOW INTO SATURDAY. WITH A SIGNIFICANT WINTER
STORM POSSIBLE IN THE HIGHER ELEVATIONS.
NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:
- SHOWERS AND A STRONG COLD FRONT PASS LATE-DAY ACCOMPANIED BY
GUSTY WINDS AND POSSIBLY A RUMBLE OF THUNDER.
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A DEEP UPPER LEVEL LOW WILL SPIN TOWARD THE WESTERN GREAT LAKES
TODAY. THE TROUGH AXIS ROTATING AROUND THE SOUTHERN FLANK OF
THE LOW WILL EXTEND TO THE SOUTHEAST OF THE LOW CENTER THE
AFTERNOON. A POWERFUL SHORTWAVE SWINGING AROUND THE BASE OF THE
TROUGH WILL MOVE OVER CENTRAL OHIO THIS AFTERNOON. A SURFACE LOW
WILL RAPIDLY DEVELOP AND STRENGTHEN UNDERNEATH THE WAVE AND
DRIVE A STRONG COLD FRONT THROUGH THE AREA LATE TODAY. SHOWERS
WILL DEVELOP ALONG THE BOUNDARY AND QUICKLY SWING THROUGH DURING
THE AFTERNOON AND EVENING HOURS. RAINFALL WILL BE LIGHT, BUT
THE MAIN CONCERN IS THE THREAT FOR STRONG WIND GUSTS WITH FROPA.
LATEST CAM MODELS ARE SHOWING A THIN LINE OF CONVECTION
DEVELOPING RIGHT AHEAD OF THE FRONT. FORECAST SOUNDINGS ARE
ADVERTISING INSTABILITY ALOFT INCREASING, WHICH WILL ALLOW THE
STRONG WINDS ALOFT TO RUSH TOWARD THE SURFACE. HREF PROBS OF
GUSTS > 40 MPH ARE 40 TO 50% ALONG THE FRONT, WITH 10 TO 20% OF
> 45 MPH.
ANOTHER PERIOD OF WARM AIR ADVECTION IS EXPECTED AHEAD OF THE
FRONT TODAY SO TEMPERATURES WILL ONCE AGAIN BE WELL ABOVE
NORMAL.
SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY/
KEY MESSAGES:
- RAIN AND SNOW CHANCES CONTINUE THURSDAY AND FRIDAY WITH
IMPACTFUL ACCUMULATIONS LIKELY FOR THE HIGHER TERRAIN.
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STRONG COLD AIR ADVECTION IS EXPECTED TONIGHT WHICH WILL TANK
TEMPERATURES DOWN TO THE LOW 30S OR EVEN UPPER 20S OVERNIGHT.
A DRY SLOT ALOFT WILL CROSS THE REGION OVERNIGHT WHICH SHOULD
LIMIT THE THREAT FOR ANY SNOW SHOWERS.
THE UPPER LOW WILL MOVE ACROSS THE UPPER OHIO VALLEY ON
THURSDAY. THIS WILL INITIATE MORE PRECIPITATION AND BRING
ANOTHER SHOT OF COLD AIR. A MIX OF RAIN AND SNOW IS EXPECTED AT
THE ONSET, BUT SNOW BECOMES MORE LIKELY THROUGH THE DAY
THURSDAY AS THE PARENT LOW AND DEVELOPING COASTAL LOW PIVOT
AROUND EAST OTHER. AS THE PARENT LOW DIVES SOUTHEAST, LIFT WILL
INCREASE AHEAD OR IT AND DAYTIME HEATING AND DESTABILIZATION MAY
ALLOW AN INCREASE IN SHOWERS INTO THURSDAY AFTERNOON. DAYTIME
HIGH TEMPERATURES WILL LIKELY BE BELOW AVERAGE BUT ABOVE
FREEZING FOR THE LOWLANDS WHICH WILL CHALLENGE DAYTIME
ACCUMULATIONS. THE SAME CANNOT BE SAID FOR RIDGES OVER 2KFT,
WHERE DAYTIME ACCUMULATIONS WILL BE POSSIBLE. THE WINTER STORM
WATCH BEGINS THURSDAY AFTERNOON FOR THE WEST VIRGINIA RIDGES
ACCORDINGLY. NONETHELESS, THE HIGHEST SNOWFALL RATES APPEAR THE
MOST LIKELY THURSDAY NIGHT AND BEYOND.
THE STACKED LOW WILL ROTATE TOWARD NE PA ON FRIDAY. WAVES OF
ENERGY WILL SWING AROUND THE LOW AND DIVE DOWN ACROSS THE REGION
IN THE STRENGTHENING NW FLOW. THIS SETUP WILL BRING STRONG
FORCING FOR SNOW IN THE RIDGES, WITH ADIABATIC PROFILES INTO THE
DGZ COMBINED WITH OROGRAPHIC INFLUENCES. THIS WILL BE QUITE
EFFICIENT FOR SNOW-MAKING. FOR THE LOWLANDS, TEMPERATURES MAY
BE TOO WARM FOR NOTABLE ACCUMULATIONS, BUT ARE POSSIBLE AT
NIGHT. THE CURRENT GUIDANCE SUGGESTS RELATIVELY HIGH CONFIDENCE
(75% TO 90%) THESE TOTALS WILL BE BELOW 3" WITH MOST GUIDANCE
AROUND ~1".
LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/
KEY MESSAGES:
- WINTER STORM CONDITIONS FOR THE HIGHER TERRAIN CONTINUES INTO
SATURDAY AS DO THE GUSTY WINDS.
- DRY ON SUNDAY.
- UNSETTLED PATTERN FOR THE BEGINNING OF NEXT WEEK.
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ANOTHER SHORTWAVE PASSAGE IS POSSIBLE 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. STILL A GREAT DEAL OF UNCERTAINTY IN STORM TOTAL
ACCUMULATIONS IN THE RIDGES, WITH MOST ENSEMBLE GUIDANCE
CLUSTERED BETWEEN 6" TO 16" IN THE WATCH AREA.
HERE'S THE TAKE HOME MESSAGE: A NOTABLE WINTER STORM WITH A 75%
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.
THE END OF THE LONG TERM LOOKS UNSETTLED ONCE AGAIN, BUT WITH
MILDER TEMPERATURES.
AVIATION /12Z WEDNESDAY THROUGH SUNDAY/
AREAS OF IFR/LIFR STRATUS AND FOG WILL CONTINUE THROUGH EARLY
THIS MORNING WITH LOW LEVEL MOISTURE IN PLACE. SOME CLEARING HAS
OCCURRED NEAR BVI AND FKL, THOUGH ADDITIONAL FOG/STRATUS WAS
BEGINNING TO FILL BACK IN PER LATEST SATELLITE IMAGERY.
A GRADUAL IMPROVEMENT TO MVFR IS EXPECTED BY MID TO LATE MORNING
AS MIXING INCREASES AND LIFTS CIGS HEIGHTS. A STRONG COLD FRONT
APPROACHES THE REGION THIS AFTERNOON AS SURFACE LOW PRESSURE
DEEPENS ALONG IT. A BAND OF SHOWERS IS EXPECTED WITH THE
APPROACH AND PASSAGE OF THE FRONT.
MODEL SOUNDINGS INDICATE ENOUGH INSTABILITY WILL EXIST FOR
ISOLATED EMBEDDED THUNDERSTORMS. ALTHOUGH CHANCES OF ANY ONE
LOCATION OBSERVING THUNDER ARE TOO LOW FOR TAF INCLUSION AT THIS
TIME, INSTABILITY TRENDS WILL BE MONITORED THROUGHOUT THE
MORNING FOR ANY NECESSARY AMENDMENTS OR INCLUSION IN THE NEXT
TAF CYCLE. IFR VSBYS AND, WITH A STRENGTHENING LOW LEVEL JET
AND TIGHTENING PRESSURE GRADIENT, WESTERLY WIND GUSTS FROM
35-40KT ARE EXPECTED WITH THE HEAVIER SHOWERS AND FROPA. GUSTY
WEST WIND WILL CONTINUE AFTER FROPA, THOUGH IMPROVEMENT TO VFR
IS EXPECTED THIS EVENING UNDER DRY, COLD ADVECTION.
OUTLOOK...
RESTRICTIONS ARE EXPECTED TO RETURN TO THE REGION EARLY THURSDAY
MORNING AND CONTINUE THROUGH SATURDAY, AS AREAS OF LOW PRESSURE
SPIN ACROSS THE NE CONUS. PERIODS OF RAIN AND SNOW SHOWERS ARE
ALSO EXPECTED DURING THIS PERIOD. VFR SHOULD RETURN SUNDAY AS
HIGH PRESSURE BUILDS IN.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH SATURDAY
EVENING FOR PAZ074-076-078.
OH...NONE.
WV...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH SATURDAY
EVENING FOR WVZ510>514.
SYNOPSIS...22
NEAR TERM...22
SHORT TERM...22/MILCAREK
LONG TERM...22/MILCAREK
AVIATION...CERMAK/WM
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