146
FXUS61 KPBZ 200116
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
816 PM EST TUE NOV 19 2024
SYNOPSIS
AFTER A ROUND OF LOW CLOUDS, FOG, AND DRIZZLE TONIGHT, A COLD
FRONT TOMORROW WILL BRING ANOTHER CHANCE OF SHOWERS. GUSTY
WINDS ARE POSSIBLE ALONG THE COLD FRONT, CONTINUING THROUGH
LATE- WEEK. A WINTER STORM IS LIKELY FOR HIGHER TERRAIN THURSDAY
THROUGH SATURDAY, WITH LESSER NIGHTTIME ACCUMULATIONS POSSIBLE
FOR THE LOWLANDS.
NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/
KEY MESSAGES:
- LOW CLOUDS, FOG, AND PATCHY DRIZZLE WILL PERSIST THROUGH THE
NIGHT.
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THE WARM FRONT HAS LIFTED ALMOST COMPLETELY THROUGH THE REGION
THIS EVENING, TAKING THE STEADIER LIGHT RAIN WITH IT. BEHIND THE
BOUNDARY, THE LOWER LEVELS REMAIN NEARLY SATURATED. THE 00Z PBZ
SOUNDING SHOWS ABUNDANT MOISTURE BELOW 725MB. BELIEVE THAT THIS
MOISTURE WILL CONTINUE TO MANIFEST MORE AS A LOW STRATUS DECK
THROUGH THE NIGHT ACROSS THE MAJORITY OF THE REGION, WITH PATCHY
DRIZZLE/MIST AT THE SURFACE.
EASTERN OHIO WILL NEED TO BE WATCHED OVERNIGHT. IF CLEARING
BECOMES MORE ESTABLISHED THAN ANTICIPATED HERE, THERE IS THE
POTENTIAL FOR LOCALLY DENSE FOG IN AT LEAST A FEW COUNTIES. WILL
CONTINUE TO MONITOR.
OVERNIGHT TEMPERATURES WILL REMAIN QUITE MILD GIVEN THE WEAK
WARM ADVECTION, WITH MANY NOT DROPPING OUT OF THE 50S.
SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY/
KEY MESSAGES:
- RAIN AND A STRONG COLD FRONT PASS LATE-DAY WEDNESDAY
ACCOMPANIED BY GUSTY WINDS.
- RAIN AND SNOW CHANCES CONTINUE THROUGH THURSDAY WITH
ACCUMULATIONS LIKELY FOR HIGHER TERRAIN.
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THE SHORT TERM PERIOD WILL BE DEFINED BY THREE DISTINCT PERIODS.
THE FIRST PERIOD WILL BE (1) BEFORE THE COLD FRONT, THE SECOND
WILL BE (2) ALONG THE COLD FRONT, AND THE THIRD WILL BE (3) BEHIND
THE COLD FRONT.
1) A LARGE OCCLUDING STACKED LOW WILL SIT IN THE HIGH PLAINS,
ELONGATING AND DIPPING SOUTH ACROSS THE LOWER GREAT LAKES FOR
MOST OF THE DAY WEDNESDAY. THE AREA WILL MAINTAIN WARM,
SOUTHWEST FLOW AHEAD OF THE COLD FRONT PASSAGE THAT WILL ALLOW
WEDNESDAY HIGH TEMPERATURES TO CLIMB 10 TO 20 DEGREES ABOVE
AVERAGE.
2) A POTENT SHORTWAVE TROUGH AXIS WILL PIVOT AROUND THE LOW
BRINGING A STRONG COLD FRONT ACROSS THE REGION. THE MOST LIKELY
TIME OF ARRIVAL WILL BE AROUND 3PM FOR ZANESVILLE, 5PM FOR
PITTSBURGH, AND 8PM FOR DUBOIS AS IT TRANSLATES FROM THE WEST IN
A EAST-NORTHEASTERLY DIRECTION. STRONG FORCING AND AN ABRUPT
DESTABILIZATION MEAN THAT A RUMBLE OF THUNDER COLD NOT BE RULED
OUT ON THE FRONT ITSELF, BUT THE MAIN IMPACT WILL BE GUSTY WINDS
ALONG AND BEHIND THE FRONT IN STRONG COLD ADVECTION. MOST
ENSEMBLES SUGGEST THAT 25MPH TO 35MPH GUSTS ARE MOST LIKELY,
THOUGH LOCALLY HIGHER GUSTS ARE POSSIBLE. ADDITIONALLY, THIS
WILL TANK TEMPERATURES FROM NEAR OR ABOVE THE 60 DEGREE MARK
DOWN TO THE LOW 30S OR EVEN UPPER 20S OVERNIGHT.
3) BECAUSE OF THE POTENT COLD ADVECTION ACTING TO COOL SURFACE
TEMPERATURES AND DESTABILIZE PROFILES, A FEW SNOW SHOWERS COULD
NOT BE RULED OUT WEDNESDAY NIGHT OR EARLY THURSDAY MORNING, BUT,
FOR THE MOST PART, THIS WILL BE DEFINED BY SHORTWAVE RIDGING AND
PREDOMINANTLY DRY WEATHER WITH THE MOST LIKELY SNOW/AND OR
ACCUMULATIONS FOR THE RIDGES WITH OROGRAPHIC INFLUENCE. INITIAL
ACCUMULATIONS WILL BE CHALLENGED BY WARM SURFACE TEMPERATURES.
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.
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
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. 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". 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. 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.
THE TIMING OF THE HIGHEST RATES WILL BE TIED CLOSELY TO
SHORTWAVES, PREDICTABILITY IS INCREASINGLY SLIGHTLY IN THESE
DETAILS. 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 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. TEMPERATURES WILL MODERATE BOTH
DAYS.
AVIATION /01Z WEDNESDAY THROUGH SUNDAY/
RAIN SHOWERS HAVE BEGUN TO EXIT THE REGION THIS EVENING AS A
WARM FRONT LIFTS OFF TO THE NORTH AND FORCING IS LOST. PLENTY OF
LOW-LEVEL MOISTURE REMAINS AS EVIDENT ON THE 00Z PIT SOUNDING
WHICH IS PROVIDING A BLANKET OF IFR TO LIFR LOW CLOUDS AND BR.
THIS WILL LARGELY BE THE THEME THROUGH THE OVERNIGHT HOURS AS
PROBABILITIES FOR MVFR TO IFR REMAIN HIGH AT 90+%. A PATCH OF
WARM ADVECTION IS HELPING TO LIFT CIGS BACK TO MVFR UPSTREAM,
AND THIS COMBINED WITH AN INTRUSION OF SLIGHTLY DRIER AIR
LESSENS IFR PROBABILITIES SOME FOR OVERNIGHT FROM PIT AND
NORTH. DON'T THINK WIDESPREAD DENSE FOG IS HIGHLY PROBABLE
TONIGHT AS SOUNDINGS KEEP THE NEAR-SURFACE LAYER MIXED WITH A
LIGHT WIND WHICH SHOULD FAVOR MORE LOW CEILINGS THAN VISIBILITY
RESTRICTIONS. WHERE WIND CAN GO LIGHTER TO NEAR CALM AND
PROFILES ERR MORE ISOTHERMAL (HIGHEST PROBABILITY AT ZZV/MGW),
MOISTURE MAY MANIFEST MORE AS FOG, SO HAVE ERRED MORE AGGRESSIVE
ON VIS RESTRICTIONS THERE. THAT SAID, IF WIND DOES END UP
CALMER ACROSS THE BOARD, COULD SEE VIS DROP AS A RESULT.
OVERALL, CONFIDENCE IS LOW IN THAT SCENARIO.
CIGS WILL LIFT GRADUALLY ON WEDNESDAY COINCIDENT WITH DAYTIME
MIXING, THOUGH PROBABILITIES AREN'T ALL THAT EXCITED ABOUT A
QUICK EROSION NOR A RETURN TO VFR AS MOISTURE REMAINS ENTRENCHED
BEFORE ADDITIONAL SHOWERS RETURN IN THE AFTERNOON AND REINFORCE
RESTRICTIONS. MIXING INTO A STRENGTHENING LOW-LEVEL JET WILL
PROVIDE SOUTHWESTERLY GUSTS TO 20-30 KNOTS WITH A 70-90%
PROBABILITY, ESPECIALLY ALONG A NARROW LINE OF SHOWERS
ACCOMPANYING A PASSING COLD FRONT WEDNESDAY EVENING.
OUTLOOK...
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...MILCAREK
NEAR TERM...CL/MILCAREK
SHORT TERM...MILCAREK
LONG TERM...22/MILCAREK
AVIATION...MLB
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