126
FXUS61 KPBZ 201821
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
121 PM 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 /THROUGH TONIGHT/
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 50 TO 60% ALONG THE FRONT, WITH 20 TO 40% OF
> 45 MPH. WHILE WIND REMAINS THE PRIMARY THREAT, AN ISOLATED
SPIN UP COULD NOT BE RULED OUR WITH STRONG LOW-LEVEL SHEAR AND A
WEAKLY VEERED 0-1KM PROFILE. INTO THIS AFTERNOON, WE WILL BE
MONITORING PRE-FRONTAL CELLS AND MERGERS TO REALIZE THIS THREAT
WITH INITIAL CONVECTION. THIS THREAT DECREASES WHEN CELLS
BECOME LINEAR OR CONGEAL THIS EVENING.
STRONG COLD AIR ADVECTION IS EXPECTED TONIGHT WHICH WILL TANK
TEMPERATURES DOWN TO THE LOW 30S OR EVEN UPPER 20S OVERNIGHT.
THIS WILL ALSO ALLOW WINDS BEHIND THE FRONT TO REMAIN ELEVATED,
JUSTIFYING A WIND ADVISORY FOR THE HIGH TERRAIN. A DRY SLOT
ALOFT WILL CROSS THE REGION OVERNIGHT WHICH SHOULD LIMIT THE
THREAT FOR ANY SNOW SHOWERS.
SHORT TERM /THURSDAY THROUGH SATURDAY/
KEY MESSAGES:
- RAIN AND SNOW CHANCES CONTINUE THURSDAY AND FRIDAY WITH
IMPACTFUL ACCUMULATIONS LIKELY FOR THE HIGHER TERRAIN.
- WINTER STORM CONDITIONS FOR THE HIGHER TERRAIN CONTINUES INTO
SATURDAY AS DO THE GUSTY WINDS.
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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 WARNING AND
WINTER WEATHER ADVISORY BEGINS THURSDAY AFTERNOON FOR THE WEST
VIRGINIA RIDGES ACCORDINGLY. NONETHELESS, THE HIGHEST SNOWFALL
RATES APPEAR THE MOST LIKELY THURSDAY NIGHT AND EARLY FRIDAY
MORNING FOR THE PA ADVISORY/WARNING AREA, AND DURING THE DAYTIME
FRIDAY FOR THE HIGH TERRAIN OF WV.
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".
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. 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 WARNING PERIOD. ACCUMULATIONS IN THE RIDGES VARY FROM
6-12" FOR PA TO UP TO 10-18" FOR WV. WITH SHALLOW SATURATION
AND THE POTENTIAL FOR BELOW FREEZING TEMPERATURES, PRECIPITATION
MAY END AS A BRIEF FREEZING DRIZZLE SATURDAY IN EASTERN TUCKER.
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
MORNING. THIS IS 50% TO 75% LIKELY FOR THE RIDGES OF PA. GUSTY
WINDS ARE LIKELY THROUGH THE WHOLE PERIOD, AND BLOWING SNOW MAY
BE A HAZARD FOR THE RIDGES.
LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/
KEY MESSAGES:
- DRY ON SUNDAY.
- UNSETTLED PATTERN FOR THE BEGINNING OF NEXT WEEK.
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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 /18Z WEDNESDAY THROUGH MONDAY/
FOG HAS DISSIPATED ACROSS THE AREA AND CEILINGS HAVE MOSTLY
LIFTED TO VFR, WITH THE EXCEPTION OF A FEW PATCHY INSTANCES OF
MVFR LINGERING AROUND BVI AND HLG. A STRONG COLD FRONT CAN BE
SEEN IN BOTH SURFACE OBSERVATIONS AND SATELLITE IMAGERY MARCHING
EASTWARD ACROSS OHIO AT THIS TIME, WITH LATEST GUIDANCE
SUGGESTING IT REACHES ZZV AROUND 19Z, PIT/AGC AROUND 22Z, AND
LASTLY DUJ AROUND 00Z. AHEAD OF THIS FRONT, A LINE OF SHOWERS
ARE EXPECTED TO DEVELOP LATE THIS AFTERNOON AND EVENING,
PRIMARILY IMPACTING TERMINALS EAST OF I-77. SOME OF THE
STRONGER CONVECTION COULD PRODUCE WIND GUSTS TO 40 KNOTS AND A
RUMBLE OR TWO OF THUNDER, THOUGH OVERALL PROBABILITIES FOR
THUNDER AT ANY GIVEN LOCATION REMAIN TOO LOW (<20%) TO WARRANT
INCLUDING IN TAFS.
BEHIND THE FRONT, EXPECT BORDERLINE MVFR/IFR CIGS TO FILL IN AND
WESTERLY WINDS INCREASING TO 15-20 KTS WITH GUSTS TO 30-35 KTS.
A BRIEF PERIOD OF VFR IS EXPECTED OVERNIGHT AS WEST WINDS SETTLE
AND DRY AIR ADVECTS IN BEHIND THE FRONT. ADDITIONAL CIG/VIS
RESTRICTIONS BUILD IN BY THURSDAY MORNING, HOWEVER, AS RAIN AND
SNOW SHOWERS DEVELOP AND SPREAD ACROSS THE AREA.
OUTLOOK...
RESTRICTIONS ARE EXPECTED THURSDAY THROUGH SATURDAY AS A SERIES
OF LOW PRESSURE SYSTEMS SPIN ACROSS THE NE CONUS, BRINGING
PERIODS OF RAIN AND SNOW SHOWERS TO THE AREA. VFR SHOULD RETURN
SUNDAY AS HIGH PRESSURE BUILDS IN.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...WINTER WEATHER ADVISORY FROM 1 PM THURSDAY TO 7 AM EST
SATURDAY FOR PAZ009-016-077-078.
WIND ADVISORY FROM 5 PM THIS AFTERNOON TO 1 AM EST THURSDAY
FOR PAZ074-076-078.
WINTER STORM WARNING FROM 1 PM THURSDAY TO 7 AM EST SATURDAY
FOR PAZ074-076.
OH...NONE.
WV...WINTER WEATHER ADVISORY FROM 1 PM THURSDAY TO 7 AM EST
SATURDAY FOR WVZ510.
WIND ADVISORY FROM 5 PM THIS AFTERNOON TO 1 AM EST THURSDAY
FOR WVZ510>514.
WINTER STORM WARNING FROM 1 PM THURSDAY TO 7 AM EST SATURDAY
FOR WVZ511>513.
WINTER STORM WARNING FROM 1 PM THURSDAY TO 7 PM EST SATURDAY
FOR WVZ514.
SYNOPSIS...22/MILCAREK
NEAR TERM...22/MILCAREK
SHORT TERM...22/MILCAREK
LONG TERM...22/MILCAREK
AVIATION...CERMAK/WM
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