417
FXUS61 KPBZ 020810
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
310 AM EST TUE DEC 2 2025
SYNOPSIS
WIDESPREAD PRECIPITATION EXPECTED THIS MORNING, WITH IMPACTFUL
SNOW ACCUMULATION FOR MUCH OF THE REGION. AFTER A BRIEF BREAK
TUESDAY NIGHT INTO WEDNESDAY, AN ACTIVE WEATHER PATTERN AND
BELOW-NORMAL TEMPERATURES CONTINUE INTO NEXT WEEKEND.
NEAR TERM /THROUGH TODAY/
KEY MESSAGES:
- A WINTER WEATHER ADVISORY REMAINS IN EFFECT FOR THE ENTIRE
AREA UNTIL 1 PM
- WIDESPREAD SNOWFALL ACCUMULATIONS OF 2-5 INCHES, ESPECIALLY
NORTH OF I-70. HEAVIEST SNOWFALL RATES OCCUR BETWEEN 4 AM AND
8 AM, IMPACTING THE MORNING COMMUTE
- MIXED PRECIPITATION IN THE MON VALLEY AND THE RIDGES OF SW PA
AND NORTHERN WV, INCLUDING A CHANCE FOR LIGHT ICE ACCUMULATION
DUE TO PERIODS OF FREEZING RAIN
- PRECIPITATION ENDS FROM WEST TO EAST BY LATE MORNING OR EARLY
AFTERNOON
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LITTLE CHANGE WAS NEEDED TO THE FORECAST THROUGH TODAY, AS THE
SEQUENCE OF EVENTS IS PLAYING OUT LARGELY AS EXPECTED. AN
UPPER TROUGH, CURRENTLY CROSSING THE WESTERN GREAT LAKES, WILL
SWING INTO THE MIDDLE OHIO VALLEY THIS MORNING AND INTO THE
APPALACHIANS BY THIS EVENING. MODELS CONTINUE TO AGREE ON THE
TRACK OF THE ASSOCIATED SURFACE LOW, BRINGING IT UP THE ATLANTIC
COAST TODAY AND TO JUST OFF OF SOUTHERN NEW ENGLAND BY 00Z.
PRECIPITATION IS IN THE PROCESS OF OVERSPREADING THE REGION,
HAVING BEGUN HERE IN MOON AT ABOUT 0715Z.
WARM ADVECTION AHEAD OF THE SYSTEM HAS LED TO RISING
TEMPERATURES SOUTH AND EAST OF PITTSBURGH, WITH LBE, MGW, AND
VVS ALL RISING INTO THE MID 30S AS OF 2 AM. HRRR SOUNDINGS HERE ARE
SUGGESTING A WEAK WARM LAYER ALOFT, OR EVEN NEAR ISOTHERMAL
PROFILES AROUND 0C, SUGGESTING PERHAPS SOME SLEET OR FREEZING
RAIN AT ONSET, BEFORE WET-BULBING CHANGES MUCH OF THIS OVER TO
SNOW. LOWER SNOW-TO-LIQUID RATIOS (6:1 TO 10:1) ARE EXPECTED AS
COMPARED TO AREAS TO THE NORTHWEST. HOWEVER, A STRONGER AND
MORE PERSISTENT WARM LAYER ALOFT REMAINS MORE LIKELY IN THE AREA
OF THE LAURELS AND ESPECIALLY THE WEST VIRGINIA RIDGES, WHERE
FREEZING RAIN IS MORE OF A THREAT. ONLY A LIGHT GLAZE IS
EXPECTED IN MOST CASES, BUT EASTERN TUCKER COUNTY COULD SEE A
MORE MEANINGFUL ICE ACCRETION OF A TENTH OF AN INCH OR SO THIS
MORNING. SOME PLAIN RAIN SHOULD EVEN MIX IN BY THE TAIL END OF
THIS EVENT.
OTHERWISE, IN AREAS WEST OF I-79 AND NORTH OF I-70, ALL SNOW IS
FORECAST FOR THE EVENT, WITH SLRS GENERALLY IN THE 10:1 TO 14:1
RANGE. WE ARE ALREADY SEEING VISIBILITIES OF A MILE OR LESS AT
A FEW LOCATIONS. THE HEAVIEST SNOW RATES ARE STILL PICTURED TO
BE IN THE 4 AM TO 8 AM WINDOW, CREATING WIDESPREAD IMPACTS
DURING THE MORNING COMMUTE. THE HREF CONTINUES TO SUGGEST THAT
INSTANTANEOUS SNOW RATES OF 1 INCH PER HOUR REMAIN POSSIBLE IN
BANDED PRECIPITATION IN THE OVERALL SHIELD, SUPPORTED BY 700MB
FRONTOGENESIS AND JET-AIDED ASCENT. STORM TOTAL SNOWFALL OF AT
LEAST 3 INCHES HAS A 50 TO 80 PERCENT PROBABILITY OF OCCURRENCE
IN THE ALL-SNOW REGION, WITH LOWER PROBABILITIES IN THE MIXED-
PRECIPITATION REGION TO THE SOUTH AND EAST. BEST PROBABILITIES
OF 4 TO PERHAPS 5 INCHES IN SPOTS, AT AROUND 50 PERCENT, LIE
NORTHEAST OF PITTSBURGH. GIVEN ALL OF THIS, SUFFICIENT IMPACTS
TO THE MORNING COMMUTE ARE EXPECTED TO JUSTIFY THE CONTINUED
EXISTENCE OF THE CWA-WIDE WINTER WEATHER ADVISORY, EVEN IF
ACCUMULATION CRITERIA ARE NOT TECHNICALLY MET IN SOME LOCATIONS
TO THE SOUTHEAST OF PITTSBURGH.
PRECIPITATION SHOULD END FAIRLY RAPIDLY FROM WEST TO EAST
DURING THE LATE MORNING AND EARLY AFTERNOON AS THE LOW PULLS
INTO THE ATLANTIC AND AS MOISTURE DEPTH DECREASES WITH THE
PASSAGE OF THE SHORTWAVE TROUGH AXIS. SOME SNOW SHOWERS MAY
LINGER NEAR AND NORTH OF I-80 AS WELL AS IN THE RIDGES WITH A
BRIEF PUSH OF NW FLOW, BUT ADDITIONAL ACCUMULATION SHOULD NOT BE
AS IMPACTFUL, REMAINING UNDER AN INCH. TRENDS WILL CONTINUE TO
BE MONITORED TO SEE IF A LOCALIZED EXTENSION OF THE WINTER
WEATHER ADVISORY COULD BE NEEDED, PARTICULARLY IN THE RIDGES.
SHORT TERM /TONIGHT THROUGH THURSDAY/
KEY MESSAGES:
- MOSTLY DRY AND COLD TUESDAY NIGHT AND WEDNESDAY
- A FRONT WEDNESDAY NIGHT INTO THURSDAY PROVIDES A REINFORCING
COLD SHOT AND SOME MINOR SNOW ACCUMULATION
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ISOLATED SNOW SHOWERS MAY LINGER NORTH OF I-80 AND ALONG THE
RIDGES IN NORTHWEST FLOW, BUT SLOWLY BACKING LOW-LEVEL WIND AND
FALLING INVERSION HEIGHTS SHOULD HELP TO LARGELY SHUT OFF THIS
ACTIVITY BY MIDNIGHT, WITH LITTLE ADDITIONAL ACCUMULATION.
SURFACE HIGH PRESSURE CROSSES THE MIDDLE OHIO VALLEY AND THE
CENTRAL APPALACHIANS LATER TUESDAY NIGHT AND WEDNESDAY, AND
EXTENDS RIDGING UP INTO THE FORECAST AREA. THIS SHOULD PROVIDE
DRY WEATHER AND CONTINUED CHILLY TEMPERATURES. MAXIMUM VALUES ON
WEDNESDAY WILL CONTINUE TO RUN SOME 10 TO 12 DEGREES BELOW
CLIMATOLOGY.
THE NEXT COLD FRONT, EXTENDING FROM LOW PRESSURE OVER HUDSON
BAY, IS FORECAST TO CROSS THE REGION LATE WEDNESDAY NIGHT AND
THURSDAY MORNING. THE ASSOCIATED SHORTWAVE TROUGH IS EXPECTED TO
REMAIN MOSTLY OVER THE NORTHERN GREAT LAKES, KEEPING MUCH OF THE
SYNOPTIC SUPPORT TO OUR NORTH. STILL, THE BOUNDARY WILL PROVIDE
A REINFORCING SHOT OF COLD AIR AS 850MB TEMPERATURES DROP INTO
THE -10C TO -15C RANGE BY THURSDAY AFTERNOON. GIVEN THE SYSTEM'S
NORTHERN ORIGINS, MOISTURE REMAINS LIMITED OVERALL. A SHOT OF
LIGHT SNOW IS FORECAST, WITH QUITE MINOR ACCUMULATION. AREAS
SOUTH OF I-80 HAVE A 30 PERCENT OR LESS CHANCE OF EXCEEDING A
HALF INCH. PORTIONS OF MERCER AND VENANGO THAT MAY BE MORE
FAVORED FOR LAKE-ENHANCED ACTIVITY COULD SEE AN INCH OR SO BY
THE TIME THE SNOW CUTS OFF THURSDAY AFTERNOON. HERE, MODEL
SOUNDINGS HINT AT SOME MODEST INSTABILITY AND REASONABLY STEEP
LAPSE RATES INTO THE DGZ THAT COULD SUPPORT BRIEFLY STOUTER SNOW
SHOWERS DURING PEAK HEATING. HOWEVER, BETTER POTENTIAL FOR SUCH
ACTIVITY, INCLUDING SNOW SQUALLS, LIES TO THE NORTH WITH DEEPER
MOISTURE AND INSTABILITY.
LONG TERM /THURSDAY NIGHT THROUGH MONDAY/
KEY MESSAGES:
- DRY AND COLD THURSDAY NIGHT AND FRIDAY
- BELOW AVERAGE TEMPERATURES AND CONTINUED WINTRY PRECIPITATION
CHANCES INTO EARLY NEXT WEEK
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DRY WEATHER IS FORECAST FOR THURSDAY NIGHT AND FRIDAY AS HIGH
PRESSURE CROSSES IN QUASI-ZONAL FLOW. A MOSTLY CLEAR SKY AND LIGHT
WIND MAY AID RADIATIONAL COOLING ON WHAT LOOKS TO BE THE COLDEST
NIGHT OF THE SEASON THUS FAR. MANY LOCATIONS AWAY FROM URBAN AREAS
AND MAJOR RIVER VALLEYS HAVE A 50 PERCENT OR GREATER CHANCE OF LOW
TEMPERATURES COLDER THAN 10 DEGREES ACCORDING TO THE NBM. BELOW-
FREEZING HIGH TEMPERATURES ARE EXPECTED FRIDAY FOR MANY AREAS NORTH
OF I-70.
FOR SATURDAY, ENSEMBLES GENERALLY DRAG A WEAK 500MB SHORTWAVE ACROSS
THE UPPER OHIO VALLEY WITH A GREAT LAKES SURFACE LOW. THERE ARE SOME
QUESTIONS REGARDING PRECIPITATION TYPE, BUT AMOUNTS APPEAR TO BE
LIGHT OVERALL. SOME MODEST TEMPERATURE RECOVERY MAY OCCUR, INTO THE
MID TO PERHAPS UPPER 30S IN SPOTS. THEREAFTER, ADDITIONAL SHORTWAVE
ACTIVITY MAY CONTINUE TO KEEP A TROUGH CARVED OUT ACROSS THE
NORTHEAST CONUS INTO EARLY NEXT WEEK, PROMISING CONTINUED BELOW-
NORMAL TEMPERATURES AND FURTHER CHANCES OF WINTRY PRECIPITATION.
AVIATION /06Z TUESDAY THROUGH SATURDAY/
KEY MESSAGES:
- SNOW ARRIVES AFTER 06Z BRINGING WIDESPREAD IFR AND LOWER
RESTRICTIONS AREAWIDE
- PERIOD OF WORST CONDITIONS LIKELY BETWEEN 08Z-14Z
- SOUTHEASTERLY WIND VEERS NORTHWESTERLY BY TUESDAY AFTERNOON
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A COASTAL LOW WILL QUICKLY OVERSPREAD SNOW ACROSS THE AREA
AFTER 06Z WITH IFR RESTRICTIONS QUICK TO FOLLOW. HEAVIEST
SNOWFALL STILL APPEARS TO BE ROUGHLY 08-14Z THIS MORNING, DURING
WHICH GENERAL SNOWFALL WILL HAVE HOURLY RATES RANGING FROM 0.5
TO 1 INCHES PER HOUR. HI-RES GUIDANCE CONTINUES TO SUGGEST THE
POTENTIAL FOR ONE OR MORE EMBEDDED SW/NE ORIENTED BANDS DURING
THIS TIMEFRAME WITH A 30-50% CHANCE OF ENHANCED SNOWFALL RATES
EXCEEDING 1 IN/HR. HAVE TIMED TEMPO GROUPS TO ACCOUNT FOR THIS
PERIOD OF ENHANCED SNOWFALL.
WIDESPREAD PRECIPITATION SHOULD QUICKLY END FROM WEST TO EAST
LATER THIS MORNING... ROUGHLY 13-15Z FOR EASTERN OH AND THE WV
PANHANDLE, AND 15-18Z ACROSS WESTERN PA. LIGHT SNOW SHOWERS MAY
LINGER, ESPECIALLY FOR FKL/DUJ/LBE/MGW. CIGS ARE EXPECTED TO
GRADUALLY RISE TO MVFR THROUGH THE AFTERNOON, BUT MAY LOWER
AGAIN (EXCEPT FOR ZZV) THIS EVENING.
SOUTHEASTERLY WIND PREVAILS THIS MORNING, BECOMING NORTHWESTERLY
WITH COLD FRONTAL PASSAGE BEFORE 18Z.
OUTLOOK...
GRADUAL CEILING IMPROVEMENT IS EXPECTED ON WEDNESDAY WITH
EVENTUAL RETURN TO VFR WEDNESDAY AFTERNOON. ADDITIONAL LIGHT
SNOW CHANCES AND RESTRICTIONS ARE POSSIBLE AGAIN WEDNESDAY NIGHT
INTO THURSDAY MORNING (FAVORING LOCATIONS NORTH OF PIT) AND
DURING THE DAY FRIDAY (FAVORING LOCATIONS SOUTH OF PIT).
PBZ WATCHES/WARNINGS/ADVISORIES
PA...WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
PAZ007>009-013>016-020>022-029-031-073>078.
OH...WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
OHZ039>041-048>050-057>059-068-069.
WV...WINTER WEATHER ADVISORY UNTIL 1 PM EST THIS AFTERNOON FOR
WVZ001>004-012-021-509>514.
SYNOPSIS...CL
NEAR TERM...CL
SHORT TERM...CL
LONG TERM...CL
AVIATION...RACKLEY/MLB
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