058
FXUS61 KPBZ 272111
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
511 PM EDT WED OCT 27 2021
SYNOPSIS
A DRY THURSDAY WILL GIVE WAY TO RAIN ON FRIDAY WITH THE ADVANCE OF
STRONG LOW PRESSURE.
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/
SEASONABLY COOL, BUT DRY WEATHER CAN BE EXPECTED TONIGHT WITH
VARIABLE CLOUDINESS OVER THE REGION AS HIGH PRESSURE BUILDS IN
THE EASTERN MIDWEST. THE STRATUS OVER THE AREA HAS BEEN PARTLY
ALLEVIATED OVER NORTHEASTERN COUNTIES TONIGHT WITH DRY ADVECTION AND
SUBSIDENCE, BUT MOISTURE TRAPPED UNDER THE SUBSIDENCE INVERSION IS
LIKELY TO MAINTAIN AREAS OF THAT CLOUDINESS EVERYWHERE FROM
BUTLER/ARMSTRONG COUNTY AND SW.
WHERE CLEARING OCCURS TO THE NORTHEAST OF PITTSBURGH, SOME PATCHY
FROST IS ANTICIPATED, BUT THIS IS NOT EXPECTED TO BE WIDESPREAD
ENOUGH TO WARRANT AN ADVISORY AT THIS LATE DATE.
SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/
RIDGING IN ADVANCE OF AN ADVANCING SOUTHERN PLAINS LOW WILL MAINTAIN
DRY WEATHER FOR THURSDAY, WITH TEMPERATURE MODERATION ABOUT 5 TO 10
DEGREES ABOVE THE AVERAGES ON THE STRENGTH OF INSOLATION AND ENSUING
WARM ADVECTION.
THE LOW IS PROJECTED TO CUTOFF AS IT DIGS OVER TN AND KY ON
THURSDAY NIGHT AND FRIDAY. STRONG WARM, MOIST ADVECTION ON ITS VAN
WILL FUEL RAIN FOR THE UPR OH VALLEY REGION PROBABLY BEGINNING IN
THE PREDAWN OF FRIDAY OVER EC OH ZONES. CURRENT INDICATIONS ARE OF
TOTALS 1 TO 1.5 INCHES OVER THE 24 HOUR PERIOD AS MID LEVEL DRY PATCH
ENCROACHMENT AND LOW PRESSURE PROGRESSION ARE EXPECTED TO ALLEVIATE A
WIDESPREAD FLOOD THREAT. IN ADDITION, WARM ADVECTION WILL CAP LOW
LEVEL MOISTURE WITH HEAVIER RAIN EXPECTED VIA UPSLOPE ASSISTANCE EAST
OF THE RIDGES. OTHERWISE, DOWNSLOPE WIND WILL PROVIDE LOW LEVEL
SUBSIDENCE FOR EASTERN ZONES AND MID LEVEL CONVERGENCE AREAS ARE NOT
MODEL- SUSTAINED. THAT SOUTHEASTERLY DOWNSLOPE WIND MAY BE
PROBLEMATIC THOUGH GIVEN POTENTIAL GUSTS RESULTING FROM THE INVERSION
AND LOW LEVEL JET CONVERGING WITH HEIGHT UPON RIDGE INTERACTION. FOR
NOW, HAVE MANUALLY ADJUSTED LOCALIZED-GUSTS UPWARD FOR FRIDAY TO
BEGIN AN UPWARD FORECAST TREND.
BY FRIDAY NIGHT, RAINFALL WILL GIVE WAY TO SCATTERED AND LIGHT
SHOWER ACTIVITY AS THE LOW DIGS OVER THE VIRGINIAS AND DROPS
CONVECTIVE TEMPERATURE VIA COOLING MID LEVELS.
LONG TERM /SATURDAY THROUGH WEDNESDAY/
ANOTHER DEEP LOW IS FORECAST TO ACROSS THE CANADIAN PRAIRIES THIS
WEEKEND, THUS FILLING THE UPPER OHIO LOW ON ITS VAN. WEEKEND SHOWER
POTENTIAL IS LIKELY TO BE FOLLOWED BY A DRY PERIOD TO START THE NEW
WORK-WEEK, BUT RAIN CHANCE WILL QUICKLY RETURN WITH SEASONABLE
TEMPERATURE THROUGHOUT THE PERIOD.
AVIATION /21Z WEDNESDAY THROUGH MONDAY/
MVFR CEILINGS WILL CONTINUE TO GRADUALLY IMPROVE OVERNIGHT TO VFR
FROM SITES NORTHEAST TO SOUTHWEST THIS EVENING UNDER WARM ADVECTION.
OUTLOOK
RAIN, RESTRICTIONS, AND WIND SHEAR ARE LIKELY LATE THURSDAY AND
FRIDAY. PERIODIC MVFR AND SHOWERS CAN BE EXPECTED FOR THE WEEKEND.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
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