Area Forecast Discussion
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000 FXUS61 KPBZ 250820 AFDPBZ AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PITTSBURGH PA 420 AM EDT FRI JUL 25 2014 .SYNOPSIS... DRY AND COOLER WEATHER WILL CLOSE THE WORK WEEK...WITH SHOWER AND THUNDERSTORM CHANCES RETURNING FOR THE WEEKEND. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... SURFACE HIGH WILL KEEP THE AREA DRY AND COMFORTABLE. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/... WEEKEND WEATHER WILL BE DEPENDENT ON TIMING AND PLACEMENT OF A SERIES OF UPPER LEVEL WAVES AND THE MOVEMENT AND LOCATION OF A COMPLEX SURFACE BOUNDARY. FLOW ALOFT EVENTUALLY BECOMES MORE ZONAL SATURDAY. THE FIRST UPPER LEVEL WAVE WILL QUICKLY SWING THROUGH SOMETIME ON SATURDAY. MODEL DIFFERENCES WITH THE DETAILS BEGIN SATURDAY AND CARRY THROUGH FOR THE REST OF THE WEEKEND. AT THIS TIME...CLARIFYING THE DETAILS IS AN ARDUOUS TASK. FOR CURRENT FORECAST WILL LEAN TOWARD SUNDAY AS BEING THE BEST TIME TO SEE WIDESPREAD SHOWER AND STORM ACTIVITY. BEGINNING LATE SATURDAY NIGHT AND CONTINUING THROUGH SUNDAY... EXPECT TO SEE MULTIPLE MCS DEVELOPMENT WHICH EVENTUALLY COULD PASS THROUGH THE REGION. AGAIN...STILL NEED TO WORK OUT MANY OF THE DETAILS. MAY ALSO SEE STORMS DEVELOP SATURDAY. HOWEVER...CURRENT MODEL DATA IS SHOWING LIMITED INSTABILITY AT THE SURFACE AND ALOFT. ADDITIONALLY...FORECAST SOUNDINGS FOR SATURDAY SHOW A CAPPED ATMOSPHERE THROUGH MUCH OF THE DAY. 6KM SHEAR IS ABOVE 40KTS...BUT WITH THE ABSENCE OF STRONG BUOYANCY AND HIGH CONVECTIVE TEMPS NOT POSITIVE CONVECTION CAN GET STARTED. WOULD LEAN TOWARD ELEVATED CONVECTION BUT EVEN MUCAPE VALUES ARE NOT IMPRESSIVE. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... THE BEGINNING OF THE LONG TERM PERIOD WILL FEATURE THE CONTINUED RISK FOR SHOWERS AND STORMS AS A SURFACE LOW AND COLD FRONT WITH PLENTY OF UPPER LEVEL SUPPORT SWINGS THROUGH. SYSTEM FINALLY EXITS MONDAY NIGHT...USHERING IN ANOTHER PERIOD OF DRY WEATHER WITH BELOW NORMAL TEMPS. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... CLEAR SKIES AND CALM WINDS UNDER HIGH PRESSURE WILL LEAD TO THE FORMATION OF MAINLY VALLEY FOG TOWARD DAYBREAK. THE TERMINALS THE ARE TYPICALLY IMPACTED BY VALLEY FOG LOOK TO HAVE A SMALL WINDOW OF IFR BUT WITH DEW POINTS CONTINUING TO DROP HAVE NOT PUSHED ANY VSBY BELOW 2SM. ANY FOG THAT DEVELOPS TONIGHT WILL BURN OFF AFTER SUNRISE WITH MOSTLY CLEAR SKIES AND VFR CONDITIONS. OUTLOOK.../FRIDAY NIGHT THROUGH TUESDAY/... RESTRICTIONS ARE LIKELY BY SUNDAY AS LOW PRES SPREADS SHWRS AND TSTMS OVR THE UPR OH REGION. THE POTENTIAL WL CONT INTO MONDAY WITH PASSAGE OF THAT SYSTEMS CDFNT. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...NONE. OH...NONE. PA...NONE. WV...NONE. && $$

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