540  
FXUS61 KPBZ 090635  
AFDPBZ  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE PITTSBURGH PA  
235 AM EDT WED JUL 9 2025  
   
SYNOPSIS
 
 
A MEANDERING BOUNDARY REMAINS IN OUR REGION INTO THE WEEKEND,  
WITH OCCASIONAL SHOWER AND THUNDERSTORMS CHANCES. LOCALLY HEAVY  
RAINFALL REMAINS POSSIBLE AT TIMES, WITH SEVERE THUNDERSTORM  
CHANCES REMAINING FAIRLY LIMITED.  
 

 
   
NEAR TERM /UNTIL 6 AM THIS MORNING/
 
 
KEY MESSAGES:  
 
- DRY WEATHER FAVORED OVERNIGHT  
- FOG DEVELOPMENT EXPECTED AGAIN TONIGHT  
---------------------------------------------------------------  
 
AS THE SURFACE BOUNDARY SETTLES NEAR TO JUST SOUTH OF INTERSTATE  
68 AND THE UPPER SHORTWAVES REMAINS EAST, THE REGION IS FAVORED  
TO EXPERIENCE DRY WEATHER OVERNIGHT AS SUBSIDENCE ALOFT TAKES  
HOLD.  
 
THE APPROACH OF A WESTERN GREAT LAKES TROUGH WILL ATTEMPT  
TO INCREASE HIGH TO MID LEVEL CLOUDS STARTING AROUND MIDNIGHT  
THROUGH WEDNESDAY MORNING; TIMING AND THICKNESS OF THESE CLOUDS  
LAYERS WILL PLAY A CRITICAL ROLE IN THE DEVELOPMENT AND AREAL  
COVERAGE OF FOG. LATEST MODEL GUIDANCE FAVORS RIVER VALLEY  
LOCATIONS AND LOCATIONS SOUTH OF PITTSBURGH WHERE LIMITED DRY  
INTRUSION OCCURRED BEHIND THE FRONT. GIVEN UNCERTAINTY IN THE  
SPACIAL COVERAGE AND IMPACTS OF INCOMING HIGHER CLOUD DECKS WILL  
PRECLUDE ANY FOG HAZARD PRODUCTS AT THIS TIME.  
 

 
   
SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/
 
 
KEY MESSAGES:  
 
- STALLED BOUNDARY KEEPS MOST OF THE ISOLATED CONVECTION SOUTH  
OF PITTSBURGH ON WEDNESDAY.  
- BETTER COVERAGE OF SCATTERED STORMS THURSDAY AS BOUNDARY LIFTS  
BACK NORTH.  
- TEMPERATURES JUST ABOVE NORMAL.  
----------------------------------------------------------------  
 
THE BOUNDARY LIKELY CONTINUES TO MEANDER SOUTH OF OUR REGION  
WEDNESDAY, KEEPING THE DEEPER MOISTURE/INSTABILITY TO THE SOUTH AND  
EAST. SOME ISOLATED DIURNAL CONVECTION REMAINS POSSIBLE, ALTHOUGH  
MODEL SOUNDINGS SHOW SOME LIMITED CAPPING POTENTIAL IN THE MIDDLE  
LEVELS, KEEPING A LID ON COVERAGE. ANY LIMITED SEVERE POTENTIAL  
WOULD EXIST IN PORTIONS OF NORTHERN WEST VIRGINIA, WHERE BETTER  
INSTABILITY/STRONGER UPDRAFT POTENTIAL WOULD LIE, ALONG WITH  
ANY POTENTIAL FOR LOCALIZED HEAVY RAINFALL, BUT THE OVERALL  
THREAT APPEARS QUITE LOW. TEMPERATURES SHOULD RISE A DEGREE OR  
TWO AS COMPARED TO TODAY, GIVEN INCIPIENT WEAK SOUTHWEST FLOW.  
 
CONVECTION FADES WEDNESDAY NIGHT, WITH THURSDAY LIKELY DAWNING  
DRY. A CROSSING SHORTWAVE TROUGH SHOULD BEGIN TO PUSH THE  
BOUNDARY NORTH AGAIN AS A WARM FRONT, WITH A BIT MORE WIDESPREAD  
DIURNAL CONVECTIVE COVERAGE POSSIBLE. SKINNY CAPE PROFILES AND  
LOW SHEAR SUGGEST THAT THE SEVERE THREAT REMAINS LOW, BUT THAT  
LOCALIZED HIGH RAINFALL RATES REMAIN POSSIBLE, ESPECIALLY AS  
PWAT LEVELS BEGIN TO RECOVER.  
 

 
   
LONG TERM /FRIDAY THROUGH TUESDAY/
 
 
KEY MESSAGES:  
 
- STALLED BOUNDARY LINGERS INTO THE WEEKEND AT LEAST WITH  
CONTINUED DAILY RAIN CHANCES, CURRENTLY HIGHEST SUNDAY.  
- LOW RAIN CHANCES NEXT WEEK AS PATTERN UNCERTAINTY INCREASES.  
- CONTINUED NEAR TO ABOVE-NORMAL TEMPERATURE.  
-------------------------------------------------------------------  
 
ON FRIDAY, A WAVE OF LOW PRESSURE ALONG THE BOUNDARY MAY PUSH IT  
BACK SOUTH OF PITTSBURGH, PERHAPS TOWARDS THE MASON-DIXON LINE. THIS  
WOULD KEEP HIGHER DIURNAL SHOWER/STORM CHANCES ACROSS OUR SOUTHERN  
ZONES. PRECIPITABLE WATER REMAINS ELEVATED NEAR AND SOUTH OF THE  
BOUNDARY, WITH A REASONABLE RANGE OF 1.3 TO 1.6 INCHES, SO LOCALLY  
HEAVY RAINFALL WILL REMAIN POSSIBLE.  
 
MORE ORGANIZED SURFACE LOW PRESSURE LIKELY LIFTS ACROSS THE WESTERN  
GREAT LAKES ON SATURDAY, WHICH WOULD PUSH THE BOUNDARY BACK NORTH,  
BEFORE A POTENTIAL COLD FRONTAL PASSAGE SATURDAY NIGHT OR SUNDAY.  
THERE REMAINS ENSEMBLE DISAGREEMENT ON HOW THIS COULD PLAY OUT,  
PARTICULARLY WITH THE TIMING. FOR NOW, SUNDAY APPEARS TO HAVE BETTER  
RAIN CHANCES THAN SATURDAY, AND GIVEN THE FROPA UNCERTAINTY, THE  
SECOND HALF OF THE WEEKEND ALSO HAS GREATER HIGH TEMPERATURE  
UNCERTAINTY. NBM 10TH TO 90TH PERCENTILE SPREADS EXCEED 10 DEGREES  
FOR MOST OF THE REGION, WITH POSSIBLE MAX VALUES RANGING FROM AROUND  
80 TO THE LOWER 90S. SEVERE POTENTIAL WILL DEPEND ON TIMING AS WELL,  
WITH ENSEMBLE SOUNDINGS AND MACHINE LEARNING ADVERTISING AT LEAST  
LOW-END POTENTIAL - FORECAST DEEP SHEAR REMAINS ON THE LOW SIDE,  
LIMITING ORGANIZED CONVECTION POTENTIAL. LOCALIZED HEAVY RAIN  
REMAINS POSSIBLE AS WELL.  
 
UNCERTAINTY THEM PROPAGATES INTO NEXT WEEK. ELEVATED 500MB HEIGHTS  
AND ZONAL FLOW ALOFT ARE MOST LIKELY, KEEPING TEMPERATURES NEAR TO  
ABOVE NORMAL, BUT DIFFERENCES IN DISTURBANCES IN THAT FLOW  
REQUIRE LOW-END POPS FOR BOTH MONDAY AND TUESDAY.  
 

 
   
AVIATION /07Z WEDNESDAY THROUGH SUNDAY/
 
 
THERE IS STILL SOME UNCERTAINTY REGARDING THE AREAL COVERAGE AND  
DEGREE OF INTENSITY FOR FOG FORMATION THIS MORNING. FACTORS FAVORING  
FOG INCLUDE ENOUGH BOUNDARY LAYER MOISTURE, VERY LIGHT WIND, AND A  
PERIOD OF CLEARER SKIES FOSTERING STRONG RADIATIONAL COOLING.  
FACTORS THAT COULD LIMIT FOG INCLUDE THE INFLUX OF MID-HIGH LEVEL  
CLOUDS OVERNIGHT AHEAD OF THE NEXT SHORTWAVE AND ITS TIMING TO  
DISRUPT COOLING PROCESSES. CLOUD COVER HAS REMAINED OVER EASTERN  
OHIO, ALLOWING FOR SOME RADIATIVE COOLING TO OCCUR OVER WESTERN PA  
AND PARTS OF NORTHERN WV. THIS HAS RESULTED IN THE DEVELOPMENT OF  
RIVER VALLEY FOG.  
 
THE FOLLOWING TERMINALS HAVE A HIGHER LIKELIHOOD OF OBSERVING FOG:  
FKL, DUJ, LBE, AND MGW. THERE IS A MODERATE CHANCE FOR PIT/AGC  
SINCE THE RIVER VALLEY FOG DEVELOPMENT HAS BEEN SLOWER AND CLOUD  
COVER WILL REACH THIS AREA SOONER THAN THE EASTERN TERMINALS.  
THERE IS A LOWER PROBABILITY FOR FOG AT BVI/HLG SINCE THESE  
TERMINALS WILL SOON HAVE CLOUD COVER.  
 
DIURNAL HEATING/MIXING WILL ERODE ANY FOG/LOW STRATUS BY 14Z, WITH  
VFR EXPECTED THE REST OF THE DAY. SHORTWAVE MOVEMENT IS LIKELY TO BE  
DISPLACED TOO FAR NORTH/SOUTH TO GENERATE PRECIPITATION, HOWEVER,  
THERE IS A LOW PROBABILITY (30%) FOR A SHOWER BETWEEN 18Z-00Z AT ZZV  
AND MGW. FOLLOWING SUNSET, THE PROBABILITY FOR A RAIN SHOWER  
DECREASES.  
 
OUTLOOK...  
A WEAKLY FORCED BUT WARM/HUMID ENVIRONMENT IS FAVORED  
THROUGH THE END OF THE WEEK THAT WILL ALLOW FOR INTERMITTENT PERIODS  
OF SHOWERS/THUNDERSTORMS; CONFIDENCE IS LIKELY TO BE LOWER ON TIMING  
VARIOUS ROUNDS OF PRECIPITATION AS WELL AS THE RESULTANT CIG/VIS  
IMPACT THEY COULD HAVE DURING THE MORNING HOURS.  
 
MORE SIGNIFICANT UPPER LEVEL AND SURFACE BOUNDARY MOVEMENT APPEARS  
TO ARRIVE OVER THE WEEKEND THAT WILL CREATE A MORE FOCUSED AND  
BETTER TIMED PERIOD FOR CONVECTION AND RESTRICTION DEVELOPMENT.  
 

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

 
 

 
 
SYNOPSIS...88  
NEAR TERM...88  
SHORT TERM...CL  
LONG TERM...CL  
AVIATION...FRAZIER/LUPO  
 
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