410
FXUS61 KPBZ 182356
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
656 PM EST MON NOV 18 2024
SYNOPSIS
ABOVE AVERAGE TEMPERATURES WITH OCCASIONAL PRECIPITATION
CHANCES PREVAIL THROUGH WEDNESDAY, WITH A DRASTIC COOL-DOWN
THURSDAY THROUGH THE WEEKEND. A WINTER STORM WATCH HAS BEEN
ISSUED FOR THE POTENTIAL OF IMPACTFUL SNOW WITHIN THE HIGHER
TERRAIN LATE THURSDAY THROUGH SATURDAY.
NEAR TERM /UNTIL 6 AM TUESDAY MORNING/
KEY MESSAGES:
- MILD TEMPERATURES, PATCHY CLOUDS, AND DRY CONDITIONS PREVAIL.
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A STALLED FRONT CONTINUES TO LINGER ACROSS THE REGION AND HAS
CREATED A DECENT SPREAD IN DEW POINTS (UPPER-50S SOUTH OF
I-70; UPPER-30S NEAR I-80). AS A RESULT, LOW-LEVEL CLOUDS REMAIN
FOCUSED SOUTH OF PIT WHILE HIGH CLOUD OR CLEAR SKY REMAINS
FOCUSED NEAR LAKE ERIE.
AFTER MIDNIGHT, FLOW WILL TRANSITION LIGHT AND EASTERLY
AS A SURFACE HIGH RIDGE ADVANCES TOWARDS THE ATLANTIC COAST AND
LOW PRESSURE SYSTEM ADVANCES INTO OHIO. HOWEVER, PROBABILITY OF
PRECIPITATION WILL REMAIN VERY LOW (LESS THAN 10%) THROUGH 6AM,
AND DOESN'T INCREASE UNTIL AFTER 9AM.
SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/
KEY MESSAGES:
- RETURNING RAIN CHANCES AND SLIGHTLY WARMER TEMPERATURES.
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THE AFOREMENTIONED SURFACE LOW IS EXPECTED TO PULL NORTH AND
DROP UNDERNEATH OF THE UPPER LOW, OCCLUDING ALONG THE WAY AND
ALLOWING THE WEAK COLD FRONT TO SURGE BACK NORTH AS A WARM FRONT
INTO TUESDAY AND TUESDAY NIGHT. AS IT DOES SO, DAYTIME HIGH
TEMPERATURES ALONG THE SPINE OF THE APPALACHIANS AND INTO THE
PENNSYLVANIA AND WEST VIRGINIA LOWLANDS MAY INCREASE SLIGHTLY
WHEN COMPARED TO THE DAY PRIOR. THE LOWS ARE ALSO MORE LIKELY TO
BE WARMER THAN THE NIGHT PRIOR WITH A SURGE OF HIGHER DEW POINT
AIR. OVERALL, TEMPERATURES WILL REMAIN 10-20 DEGREES ABOVE
AVERAGE.
THE SURFACE TROUGH PASSAGE WITH INCREASING MOISTURE MAY ALLOW
THE RIGHT CONDITIONS FOR A LIGHT RAIN TUESDAY AFTERNOON AND
EVENING. QPF WILL REMAIN HIGHEST IN EASTERN OHIO AND PARTS OF
NORTHERN WEST VIRGINIA, DECAYING TO THE EAST AS FORCING IS
LOST. THE SPREAD BETWEEN THE LOW AND HIGH END QPF (10TH TO 90TH
PERCENTILE) IN OH/WV IS ROUGHLY 0.2" TO 0.7", WITH MOST
ENSEMBLES HONED IN ON ROUGHLY 0.25" TO 0.5" TOTALS. FOR
PENNSYLVANIA, THE SPREAD DROPS TO 0.1" TO 0.4", WITH MOST
ENSEMBLES AROUND 0.1" TO 0.25". MOST LIKELY PRECIPITATION
TIMING IS LATE MORNING AND EARLY AFTERNOON FOR OHIO, AND
AFTERNOON TO EARLY EVENING FOR PENNSYLVANIA AND WEST VIRGINIA.
LONG TERM /WEDNESDAY THROUGH MONDAY/
KEY MESSAGES:
- INCREASING PROBABILITY OF AN IMPACTFUL WINTER STORM FOR HIGHER
TERRAIN THURSDAY AFTERNOON THROUGH SATURDAY ACCOMPANIED BY
GUSTY WINDS.
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A STRONG COLD FRONT IS LIKELY TO PROGRESS THROUGH THE AREA LATE
WEDNESDAY. ANTECEDENT MOISTURE COMBINED WITH THE STRONG FORCING
AXIS WILL RESULT IN RAIN AHEAD OF AND ALONG THE FRONT.
ENSEMBLES ARE QUITE VARIABLE ON THE AMOUNT OF PRECIPITATION,
WITH MOST OF THE DISTRIBUTION FALLING BETWEEN 0.1" AND 0.75".
TOTALS FALL TOWARD THE LOWER END OF THIS DISTRIBUTION IN OHIO,
AND THE HIGHER END INTO WEST VIRGINIA SN PENNSYLVANIA. WHETHER
WE TREND TOWARDS THE HIGHER OR LOWER END OF THAT SCENARIO WILL
DEPEND ON JET STRENGTH, WITH OUR REGION POSITIONED ON THE LEFT
EXIT REGION OF A CYCLONICALLY CURVED SEGMENT OF A JET MAX.
WITH THE COLD FRONT BEING QUITE POTENT, A TRANSITION TO SNOW
IS POSSIBLE THURSDAY MORNING IN HIGH TERRAIN WITH OROGRAPHIC
INFLUENCE AND DRY ADIABATIC PROFILES IN STRONG COLD ADVECTION.
NONETHELESS, CHANCES OF EXCEEDING AN INCH BY 1PM ON THURSDAY
ARE ROUGHLY 40% TO 60% FOR PEAKS OVER 2KFT FOR NOW. THERE IS
STILL A SCENARIO WITH NO ACCUMULATION BY THEN, AND THERE IS ALSO
A SCENARIO (25% CHANCE) WITH 6" BY THEN. THIS WILL LARGELY BE
DRIVEN BY SHORTWAVE TIMING UNCERTAINTY.
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 MOST LIKELY TIMING FOR
ARRIVAL OF THIS WILL BE THURSDAY AFTERNOON THROUGH FRIDAY
MORNING. THIS WILL BE ACCOMPANIED BY A 50% TO 60% CHANCE OF
MAXIMUM GUSTS EXCEEDING 45MPH FOR THE HIGHLANDS, AND A 40% TO
50% 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.
ALL THIS BEING SAID, THIS IS THE MOST LIKELY SCENARIO. THE
TIMING OF THE HIGHEST RATES WILL BE TIED CLOSELY TO SHORTWAVES,
AND THE EXACT BEHAVIOR OF SHORTWAVES REMAINS MOW 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 IS
ENCOMPASSED IN 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 THURSDAY. 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.
AVIATION /00Z TUESDAY THROUGH SATURDAY/
A WEAK STALLED BOUNDARY CONTINUES TO BISECT THE AREA FROM NORTH
TO SOUTH ALLOWING FOR LOW CLOUDS TO REMAIN SOUTH OF PIT AND
MOSTLY UPPER LEVEL CLOUDS TO THE NORTH. WHERE MVFR CIGS PLAGUED
FOR MOST OF THE AFTERNOON HAVE SEEN THEM LIFT TO THE LOW END VFR
RANGE THIS EVENING, AND EXPECT THAT MOST OF THE REMAINDER OF
THE NIGHT SHOULD REMAIN THE SAME. THE BOUNDARY WILL BEGIN TO
PUSH BACK NORTHWARD AS A WARM FRONT TONIGHT, AND PROBABILITIES
SUGGEST A LOW CONFIDENCE RETURN DOWN TO MVFR (30-40%) AS
MOISTURE CONTINUES TO POOL UP ALONG IT, BUT THINK THAT THE
INDUCED WARM ADVECTION ALOFT SHOULD PRECLUDE A WIDESPREAD DIP TO
MVFR, SO HAVE KEPT ALL SITES RESTRICTION-FREE FOR THE OVERNIGHT
HOURS. SOME ISOLATED PATCHES OF FOG ARE POSSIBLE LATE TONIGHT,
BUT THINK THAT CLOUD COVER WILL LARGELY PRECLUDE THIS.
AFTER 12Z, INCREASING MOISTURE AND ISENTROPIC LIFT, ALONG WITH A
WEAK SHORTWAVE IN INCREASING SOUTHWEST FLOW ALOFT, WILL BEGIN TO
LOWER CIGS ONCE AGAIN. LIGHT RAIN AND MVFR CIGS WILL BEGIN TO
DEVELOP FROM WEST TO EAST, WITH MEAN ENSEMBLE ARRIVAL TIME ~15Z
FOR ZZV, ~19Z FOR PIT, AND ~21Z FOR LBE, BUT STILL EXHIBITING
ABOUT AN HOUR OF UNCERTAINTY IN EITHER DIRECTION. PROBABILITY
FOR MVFR IS HIGH AT 60-90%, AND SUGGESTION FOR IFR AFTER 00Z
WEDNESDAY IS INCREASING AS THE LOW LEVELS CONTINUE TO SATURATE.
OUTLOOK....
A SERIES OF INCREASINGLY POTENT LOW PRESSURE SYSTEMS WILL BRING
BOUTS OF RESTRICTIONS, GUSTY WIND, AND RAIN TURNING INTO
POTENTIAL SNOW SHOWERS FOR THE REST OF THE WEEK.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...WINTER STORM WATCH FROM THURSDAY AFTERNOON THROUGH SATURDAY
EVENING FOR WVZ512>514.
SYNOPSIS...HEFFERAN
NEAR TERM...HEFFERAN/MILCAREK
SHORT TERM...MILCAREK
LONG TERM...MILCAREK
AVIATION...MLB/CL
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