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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