Area Forecast Discussion
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000 FXUS61 KPBZ 200754 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 354 AM EDT WED AUG 20 2014 .SYNOPSIS... A SERIES OF DISTURBANCES WILL KEEP OCCASIONAL SHOWER AND THUNDERSTORM CHANCES IN THE FORECAST THROUGH THE REST OF THE WEEK. && .NEAR TERM /THROUGH TONIGHT/... SURFACE LOW SPINNING OVER MICHIGAN CURRENTLY...PUSHING A WARM FRONT NORTHWARD ACROSS PBZ CWA. FRONT HAS AIDED REDEVELOPMENT OF TSRA BEHIND INITIAL COMPLEX WHICH HAS WEAKENED. HEAVY RAINFALL TOTALS IN A FEW SPOTS IN OHIO...ON THE ORDER OF 1 TO 2 INCHES. HANGING ON TO LIKELY POPS DURING THE NEXT SEVERAL HOURS. THIS BOUNDARY WILL BE THE FOCUS OF PRECIPITATION OVER THE NEXT 24 HOURS. DEVELOPMENT WILL CONTINUE TO BE AIDED BY A MIDLEVEL SHORTWAVE THIS MORNING...WHICH WILL ROTATE THROUGH BY AFTERNOON. A RELATIVE LULL IN PRECIPITATION MAY BE SEEN DURING THE LATE MORNING. HOWEVER...INSTABILITY AND UPPER LEVEL DIVERGENCE WILL COMBINE WITH THE BOUNDARY TO TRIGGER ADDITIONAL SHOWERS AND THUNDERSTORMS THIS AFTERNOON...WITH LIKELY POPS AREAWIDE. PWAT VALUES OF 1.5 TO 1.8 INCHES WILL CONTINUE TO SUPPORT HEAVY RAINFALL. TOUGH TO PINPOINT AREAS THAT HAVE THE BEST CHANCE OF SEEING WATER PROBLEMS. WILL HIGHLIGHT THREAT IN HWO BUT HOLD OFF ON ANY WATCHES AT THIS TIME. NOT EXPECTING MUCH OF A SEVERE THREAT GIVEN THE UNIMPRESSIVE SHEAR PROFILE. TRIED TO KEEP HIGH TEMPS ON THE LOWER SIDE OF GUIDANCE. ACTIVITY DECREASES SOMEWHAT THIS EVENING WITH THE LOSS OF HEATING AND DEPARTURE OF BETTER UPPER SUPPORT. WE MAY BE ABLE TO SQUEEZE IN A SHORT DRY PERIOD DURING THE PREDAWN HOURS BEFORE ACTIVITY RAMPS UP AGAIN SHORTLY AFTER 12Z. && .SHORT TERM /THURSDAY THROUGH FRIDAY/... A SFC BNDRY IS THEN PROGGED TO SET UP FM SFC LOW PRES OVR THE UPR MIDWEST...SEWD INTO THE OH VLY RGN. THIS WL BCM THE FOCUS FOR SHWRS/TSTMS THU THRU FRI. THE BEST UPR SPPRT...SHEAR AND INSTBY IS PROGGED FOR THU RESULTING IN AT LEAST SOME THREAT FOR SVR WEA MAINLY S AND W OF PIT INVOF THE BNDRY. WITH RATHER HIGH UNCERTAINTY IN THE SPECIFIC DETAILS WL LEAVE MENTION OUT OF HWO FOR NOW. LTL MOVEMENT TO THE BNDRY IS EXPD BY FRI AS THE UPR FLOW TURNS NW AND BCMS ORIENTED WITH THE BNDRY. TEMPS WL RMN NR OR A LTL ABV THE SEASONAL AVGS. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... LITTLE CHANGE IN THE FORECAST IS EXPECTED. THIS WILL MEAN A CONTINUATION OF SHOWER AND STORM CHANCES DEPENDENT ON TIMING AND LOCATION OF ANY UPPER LEVEL DISTURBANCES THRU ERLY NEXT WEEK. UPPER RIDGING IS PROGGED BY TUESDAY. TEMPS SHOULD REMAIN NEAR OR A FEW DEGREES ABOVE AVERAGE. && .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... SHOWERS/STORMS HAVE LOST A LITTLE BIT OF PUNCH BUT CONTINUE TO WORK THEIR WAY ACROSS THE AREA. OUTFLOW BOUNDARY OUT AHEAD OF RAIN IS PRODUCING A 20-30 KNOT GUST AS IT MOVES THROUGH...AND HAVE TRIED TO HANDLE THIS FOR THE NEXT COUPLE OF HOURS. MVFR/SPOTTY IFR CAN BE EXPECTED WITH THIS RAIN BATCH AS IT ACCOMPANIES A SHORTWAVE. KEPT VCSH BEHIND THE MAIN BATCH WITH REDEVELOPMENT ACROSS OHIO. A BRIEF BREAK IN RAINFALL IS POSSIBLE BETWEEN 12Z AND 16Z OR SO LATER THIS MORNING. THEN...DIURNAL INSTABILITY BUILDUP WILL ALLOW SHRA/TSRA TO FIRE THIS AFTERNOON. KEPT VCTS MENTION AS IT IS STILL DIFFICULT TO PINPOINT LOCATION AND TIMING...ALTHOUGH BRIEF IFR RESTRICTIONS ARE POSSIBLE ANYWHERE. ACTIVITY STARTS TO CALM DOWN A BIT AFTER SUNSET. OUTLOOK.../WEDNESDAY NIGHT THROUGH SUNDAY/... SEVERAL CROSSING DISTURBANCES WILL CAUSE PERIODIC RESTRICTIONS INTO THE WEEKEND. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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