019
FXUS61 KPBZ 210916
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
416 AM EST THU NOV 21 2024
SYNOPSIS
MUCH COLDER AIR WILL CONTINUE TO OVERSPREAD THE REGION TODAY
BEHIND A STRONG COLD FRONT. LOW PRESSURE WILL MAINTAIN AREAS OF
SNOW, POSSIBLE MIXED WITH RAIN AT TIMES TODAY THROUGH SATURDAY.
SIGNIFICANT SNOWFALL IS EXPECTED ACROSS THE LAUREL HIGHLANDS,
AND THE HIGHER TERRAIN AREAS OF WEST VIRGINIA. LIGHT
ACCUMULATIONS ARE EXPECTED ELSEWHERE.
NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:
- MUCH COLDER
- SNOW, POSSIBLY MIXED WITH RAIN, EXPECTED TODAY
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THE DRY SLOT BEHIND THE EXITING COLD FRONT WAS QUICKLY FILLING
IN WITH CLOUDS AND PATCHY LIGHT RAIN WITH MOISTURE ROTATING
AROUND AN UPPER LOW ACROSS THE LOWER GREAT LAKES/MIDWEST REGION.
THE LOW WILL CONTINUE TO DRIFT ACROSS THE UPPER OHIO VALLEY
REGION THROUGH THE DAY, AS A SURFACE LOW ROTATES AROUND IT
ACROSS THE LAKE MICHIGAN REGION.
RAIN AND SNOW WILL BEGIN TO MOVE ACROSS THE REGION THIS MORNING
UNDER INCREASING MOISTURE AND ASCENT. COLD ADVECTION WILL
CONTINUE THROUGH THE DAY, WITH 850 MB TEMPERATURES FALLING FROM
CURRENT VALUES OF -3 DEG C, TO -8 DEG C BY EVENING. UNDERCUT
GUIDANCE TEMPS GIVEN THE COLD ADVECTION. MUCH OF THE
PRECIPITATION WILL CHANGE TO MAINLY SNOW FOR MOST AREAS, WITH
ALL SNOW EXPECTED THROUGH THE DAY ACROSS THE HIGHER TERRAIN
AREAS OF PA AND WV. THE CURRENT WINTER WEATHER HEADLINES BEGIN
AT 18Z TODAY, AD THIS STILL APPEARS VALID.
INITIALLY, WIND DIRECTION WILL BE MORE WESTERLY, AND THIS IS
LESS THAN OPTIMAL FOR MAXIMUM UPSLOPE FLOW. THE DENDRITIC GROWTH
ZONE WILL BECOME SATURATED IN THE HIGHER TERRAIN, AND THIS
SHOULD RESULT IN EFFICIENT SNOW PRODUCTION. ELSEWHERE, THE LOWER
ELEVATIONS SHOULD BE TOO WARM FOR MUCH ACCUMULATION DURING THE
DAY.
SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY NIGHT/
KEY MESSAGES:
- WINTER STORM FOR THE HIGHER TERRAIN
- SNOW AND RAIN CONTINUES ELSEWHERE
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SNOW SHOULD DIMINISH IN COVERAGE THIS EVENING FOR AREAS OUTSIDE
OF THE HIGHER TERRAIN. IN THE HIGHER ELEVATION, WIND DIRECTION
WILL BECOME MORE FAVORABLE FOR UPSLOPE FLOW. THIS, COMBINED WITH
SATURATION IN THE DENDRITIC GROWTH REGION, WILL RESULT IN
EFFICIENT SNOWFALL IN THESE AREAS.
THE UPPER LOW WILL BEGIN TO SHIFT JUST EAST OF THE REGION LATE
TONIGHT AND FRIDAY MORNING. ANOTHER SURFACE LOW WILL ROTATE
AROUND IT, SPREADING ANOTHER ROUND OF SNOW ACROSS THE REGION
OVERNIGHT. A SURFACE TROUGH EXTENDING WEST FROM THE LOW COULD
RESULT IN A BRIEF ENHANCEMENT TO THE SNOW LATE TONIGHT AND EARLY
FRIDAY MORNING, ESPECIALLY AS SOME LIMITED LAKE ENHANCEMENT
OCCURS IN NW FLOW BEHIND THE TROUGH. THIS SHOULD ALSO BE THE
PERIOD OF HEAVIEST SNOW ACROSS THE HIGHER TERRAIN AS THE TROUGH
CROSSES. SNOW SHOULD GRADUALLY MIX WITH, AND CHANGE TO RAIN, FOR
MUCH OF THE AREA BY FRIDAY AFTERNOON AS THE BOUNDARY LAYER, AND
850 MB TEMPS, WARM. THE EXCEPTION WILL BE THE HIGHER TERRAIN
AREAS, WHERE PRECIP TYPE WILL REMAIN SNOW.
A TIGHTENING PRESSURE GRADIENT, AND A LOW LEVEL JET, WILL RESULT
IN GUSTY WIND AGAIN ON FRIDAY. GUSTS FROM 30-35MPH ARE EXPECTED
FOR MOST OF THE AREA, WITH GUSTS UP TO 45 MPH ACROSS THE HIGHEST
TERRAIN AREAS OF WV.
THE UPPER LOW IS PROGGED TO BE OFF THE MID ATLANTIC COAST FRIDAY
NIGHT, AS THE SURFACE LOW ROTATES ACROSS EASTERN PA AND THEN OFF
THE COAST. RAIN AND SNOW SHOULD DECREASE IN COVERAGE ACROSS MUCH
OF THE AREA AS ASCENT WEAKENS, AND MOISTURE DIMINISHES. THE
HIGHER TERRAIN AREAS WILL AGAIN SEE MAINLY SNOW UNDER CONTINUED
UPSLOPE NW FLOW, THOUGH SOME FREEZING DRIZZLE IS POSSIBLE AS
THE MOISTURE IN THE DENDRITIC GROWTH REGION BEGINS TO DECREASE.
A VORTICITY MAXIMUM WILL TRACK ACROSS THE REGION ON SATURDAY,
WITH LIGHT RAIN, AND POSSIBLY SNOW, ESPECIALLY IN THE MORNING.
DIMINISHING ASCENT AND MOISTURE LATER IN THE DAY AND SATURDAY
NIGHT SHOULD BRING A GRADUAL END TO THE PRECIP FOR MOST OF THE
REGION, THOUGH NW FLOW OFF OF THE GREAT LAKES COULD RESULT IN
SOME LIGHT PRECIP CHANCES MAINLY NORTH OF PIT.
OVERALL SNOW TOTALS SHOULD BE AROUND AN INCH OR LESS FOR MUCH OF
THE LOWER ELEVATION AREAS, AS TEMPERATURES WILL BE MARGINAL FOR
ACCUMULATION OTHER THAN AT NIGHT. THE HIGHER TERRAIN AREAS ARE
STILL EXPECTED TO SEE SIGNIFICANT ACCUMULATIONS OF 6-12 INCHES,
WITH 10-15 INCHES ACROSS THE HIGHEST PEAKS OF WV. ALL WINTER
WEATHER ADVISORIES AND WINTER STORM WARNING HEADLINES WERE
MAINTAINED AS IS, WITH NO SIGNIFICANT CHANGE IN THE FORECAST
THINKING.
LONG TERM /SUNDAY THROUGH WEDNESDAY/
KEY MESSAGES:
- DRY ON SUNDAY
- MORE UNSETTLED WEATHER RETURNS MONDAY THROUGH AT LEAST MID
WEEK
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A RIDGE OF HIGH PRESSURE WILL TRACK ACROSS THE UPPER OHIO VALLEY
REGION SUNDAY, RETURNING DRY WEATHER TO THE AREA. SURFACE LOW
PRESSURE IS EXPECTED TO TRACK ACROSS THE LOWER GREAT LAKES
REGION ON MONDAY, PULLING A COLD FRONT ACROSS THE AREA. THIS
WILL RETURN RAIN CHANCES THROUGH THE DAY. AN UPPER TROUGH WILL
FOLLOW THE COLD FRONT MONDAY NIGHT AND TUESDAY, WITH ADDITIONAL
RAIN EXPECTED. THE RAIN COULD MIX WITH OR CHANGE TO SNOW IN COLD
ADVECTION BEFORE ENDING.
AFTER THE TROUGH EXITS THE REGION WEDNESDAY MORNING, MODEL
ENSEMBLES INDICATE FLAT RIDGING WILL RETURN DRY WEATHER TO THE
REGION. TEMPERATURES SHOULD AVERAGE NEAR SEASONABLE LEVELS FOR
MUCH OF THE PERIOD.
AVIATION /08Z THURSDAY THROUGH MONDAY/
AFTER 10Z OR SO, MVFR CEILINGS ARE EXPECTED TO REDEVELOP OVER
THE REGION AS UPPER LEVEL LOW PRESSURE ROTATES INTO THE UPPER
OHIO VALLEY. AN INITIAL MIX OF RAIN/SNOW SHOWERS SHOULD TURN TO
MORE SNOW THAN RAIN DURING THE MORNING HOURS, AND CONTINUE INTO
THE AFTERNOON. FOR NOW, HAVE KEPT MVFR VISIBILITY WITH THIS
ACTIVITY. THERE WILL CERTAINLY BE PERIODS IFR OR POTENTIALLY
EVEN LIFR VISIBILITY IN SNOW WILL BE POSSIBLE ON A LOCALIZED
BASIS. HOWEVER, CONFIDENCE IN LOCATION AND TIMING OF SUCH
SHOWERS IS LOW AT PRESENT. WESTERLY WIND GUSTS WILL ALSO PICK UP
INTO THE 15 TO 25 KNOT RANGE DURING THE DAY.
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 THIS AFTERNOON TO 7 AM EST
SATURDAY FOR PAZ009-016-077-078.
WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 7 AM EST
SATURDAY FOR PAZ074-076.
OH...NONE.
WV...WINTER WEATHER ADVISORY FROM 1 PM THIS AFTERNOON TO 7 AM EST
SATURDAY FOR WVZ510.
WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 7 AM EST
SATURDAY FOR WVZ511>513.
WINTER STORM WARNING FROM 1 PM THIS AFTERNOON TO 7 PM EST
SATURDAY FOR WVZ514.
SYNOPSIS...WM
NEAR TERM...WM
SHORT TERM...WM
LONG TERM...WM
AVIATION...CL
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