114  
FXUS61 KPBZ 270526  
AFDPBZ  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PITTSBURGH PA  
126 AM EDT THU JUL 27 2017  
   
SYNOPSIS
 
 
SHOWERS AND THUNDERSTORMS RETURN THURSDAY AND FRIDAY AS A COLD  
FRONT AND UPPER LEVEL LOW PRESSURE SYSTEM MOVE THROUGH. DRY AND  
SEASONABLE WEATHER RETURNS THIS WEEKEND.  
 

 
   
NEAR TERM /UNTIL 6 AM THIS MORNING/
 
 
NO MAJOR CHANGES NEEDED TO THE OVERNIGHT FORECAST. PREVIOUS  
DISCUSSION FOLLOWS...  
 
HIGH CLOUDS CONTINUE TO FILTER THROUGH THE AREA WITH A LONG  
UPSTREAM FETCH. WHILE THE LAYER BELOW THE CIRRUS IS LARGELY  
BONE DRY, HIGH CLOUDS SHOW NO SIGNS OF ABATING. AS SUCH,  
GENERALLY MOSTLY CLOUDY BUT STILL DRY CONDITIONS ARE EXPECTED.  
LIKEWISE, WITH HIGH CLOUDS IN PLACE, LOW TEMPERATURES WILL BE UP  
A TAD FROM LAST NIGHT. FRIES  
 

 
   
SHORT TERM /6 AM THIS MORNING THROUGH SATURDAY/
 
 
SIMILAR TO PREVIOUS FORECAST, FORECAST CONFIDENCE FOR THIS  
PERIOD REMAINS LOW. THE ONE GENERAL CONCEPT THAT THE  
DETERMINISTIC MODELS AGREE ON IS THAT THE OVERALL RAIN SHIELD ON  
THURSDAY SHOULD BE SOMEWHAT FARTHER TO THE SOUTH. HAVE  
INCREASED THE GRADIENT IN POPS FROM NORTH TO SOUTH, PUSHING THE  
LINE OF LIKELY POPS FARTHER SOUTH AND KEEPING CHANCE POPS TO THE  
NORTH. HOWEVER, OVERALL PRECIPITATION ALONG THE COLD FRONT  
REMAINS SOMEWHAT UNORGANIZED. DUE TO CONCERNS ABOUT INSTABILITY,  
THE RISK OF CONVECTIVE WEATHER ON THURSDAY HAS BEEN LOWERED BY  
THE STORM PREDICTION CENTER DOWN TO A MARGINAL AREA ACROSS ALL  
COUNTIES. DAMAGING WINDS REMAIN THE PRIMARY THREAT.  
 
THERE SHOULD BE A BIT OF A LULL IN PRECIPITATION THURSDAY NIGHT  
AS THE SURFACE FRONT PLUNGES SOUTH, BUT PRECIPITATION WILL  
REDEVELOP AS AN UPPER LEVEL LOW DROPS INTO THE OHIO VALLEY ON  
FRIDAY AND HELPS TO RESTRENGTHEN LOW PRESSURE ALONG THE FRONT.  
ALL LOCATIONS HAVE LIKELY POPS ON FRIDAY. FORECAST MODELS  
CONTINUE TO SLOW DOWN THE DEPARTURE OF PRECIPITATION FRIDAY  
NIGHT INTO SATURDAY, AND HAVE DECIDED TO KEEP POPS IN THE  
FORECAST LONGER THROUGH THIS TIME PERIOD, WITH MORNING SHOWERS  
ON SATURDAY ONLY EXPECTED IN PITTSBURGH AND LOCATIONS EAST.  
 
WHILE THE SEVERE THREAT HAS DIMINISHED ON THURSDAY AND IS NOT  
PRESENT ON FRIDAY, FLOODING COULD STILL BE A POSSIBLE CONCERN.  
THE ENTIRE VERTICAL SOUNDING REMAINS QUITE MOIST, AND WARM CLOUD  
DEPTHS COULD SUPPORT PLENTY OF DOWNPOURS. IN ADDITION, FLOW WILL  
BE RATHER WEAK ON FRIDAY, MEANING THAT ANY STORMS THAT DO  
DEVELOP WILL BE SLOW MOVING IN NATURE. RAINFALL COULD RANGE  
ANYWHERE FROM A HALF INCH ALONG INTERSTATE 80 TO MORE THAN 2  
INCHES IN SOUTHERNMOST TUCKER COUNTY FROM THURSDAY MORNING  
THROUGH SATURDAY. HOWEVER, NO FLOOD WATCHES HAVE BEEN ISSUED AT  
THIS TIME BECAUSE OF THE EXTENDED TIME PERIOD OVER WHICH THE  
RAIN IS EXPECTED TO FALL.  
 

 
   
LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
 
 
HIGH PRESSURE ACROSS THE GREAT LAKES SHOULD KEEP WEATHER DRY  
THROUGH THE EXTENDED FORECAST, WITH TEMPERATURES REMAINING  
SEASONABLE THROUGH THE PERIOD. A FRONT MAY APPROACH FROM THE  
NORTHWEST BY THE MIDDLE OF NEXT WEEK, BUT THE TIMING REMAINS  
HIGHLY UNCERTAIN.  
 

 
   
AVIATION /05Z THURSDAY THROUGH MONDAY/
 
 
WITH DEWPOINTS CREEPING UP AROUND THE REGION AND CALM WINDS  
STILL IN PLACE, THE ONLY FOG INHIBITOR THIS MORNING WILL BE THE  
PRESENCE OF HIGH CLOUDS. LATEST SATELLITE IMAGERY DOES SHOW SOME  
BREAKS IN THE CLOUD COVER. WILL CONTINUE TO CARRY A FOG-FREE  
FORECAST AREAWIDE, BUT CANNOT RULE OUT A BOUNCE DOWN TO MVFR OR  
WORSE, IF A CLOUD BREAK CAN PERSIST OVER A GIVEN TERMINAL IN THE  
PRE-DAWN HOURS.  
 
HIGH CLOUDS WILL CONTINUE TO PUSH IN FROM DECAYING UPSTREAM  
CONVECTION. AS THE FIRST IN A SERIES OF WAVES APPROACHES FROM  
THE WEST TODAY, THE ENERGY DISSIPATES, LOSING ORGANIZED ASCENT.  
AS A RESULT, MODEL GUIDANCE IS CONTINUING IT'S TREND TOWARDS A  
DRIER SOLUTION. THIS SEEMS PRUDENT, GIVEN THE COPIOUS DRY AIR  
PRESENT IN THE LOWEST 10KFT. TAF FORECAST WILL REFLECT A  
CONSERVATIVE APPROACH TO SHOWER AND THUNDERSTORM CHANCES THIS  
AFTERNOON. BEST CHANCES WILL RESIDE SOUTH OF KPIT, BUT ACTIVITY  
LOOKS TOO SCATTERED TO MENTION IN ANY ONE TERMINAL.  
 
DRY AIR WILL CONTINUE TO ERODE TOWARDS THE END OF THE TAF PERIOD  
WITH PERHAPS MVFR CIGS BEGINNING TO SHOW UP FROM KZZV TO KMGW.  
 
SURFACE WINDS WILL REMAIN LIGHT THROUGH THE PERIOD.  
   
OUTLOOK
 
 
RESTRICTION CHANCES MAY CONTINUE THROUGH FRIDAY AND POSSIBLY  
INTO SATURDAY AS LOW PRESSURE IMPACTS THE OHIO VALLEY.  
 

 
   
PBZ WATCHES/WARNINGS/ADVISORIES
 
 
MD...NONE.  
OH...NONE.  
PA...NONE.  
WV...NONE.  
 

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab OH Page
The Nexlab PA Page
The Nexlab WV Page
The Nexlab MD Page Main Text Page