Area Forecast Discussion
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000 FXUS61 KPBZ 220654 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 254 AM EDT Sat Jul 22 2017 .SYNOPSIS... Warm and humid through the weekend. Showers and storms are also expected today and Sunday. Storms could be severe and produce heavy downpours. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... For the overnight, will be dealing with a dying line of convection that has developed along a boundary that has been stuck over the region for the last couple of days. As the storms move southward, they are encountering drier air aloft which will work to diminish the activity. Warm and muggy overnight. All signs are pointing to an active Saturday. Large MCS over the Western Great Lakes/Upper Midwest will be moving into my western counties around daybreak. H7-H5 lapse rates approach 6.5ckm-1 while MUcapes push 2.0kjkg-1. Wind shear is impressive as well with nearly 40 knots of shear. All of this will create an atmosphere that could yield strong to severe storms, really at any time today. Atmosphere keeps its tropical characteristics with PWATS around two inches and warm cloud depths nearing 13KFT. This will lead to heavy downpours with any storm which will increase the flash flooding threat. Limitations to the severe threat will be dependent on the amount of cloud cover today, which in turn will keep temperatures down and prevent the area from reaching forecasted convective temperatures. Additionally, still have plenty of warm air aloft and morning showers/storms will work to cool the lower levels and increase atmospheric stabilization. All of this will need to be monitored throughout the day. && .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... The risk for showers and storms will continue overnight, with the focus shifting southward as the surface boundary is pushed toward West Virginia. Another shortwave, moving southeastward in the northwest flow aloft, will work to move the boundary into the Mid-Atlantic region by dawn on Sunday. Sunday confidence is lower in organized convection moving through the region however we still remain in northwest flow with disturbances riding through. Activity wanes Sunday night with the loss of daytime heating, but again expect a muggy night with temps well into the 60s and lower 70s. Mid level trough sweeps through Monday afternoon so this will be the last round of showers/storms before a welcome break occurs. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Highlights: - Lower humidity - Active weather regime end of next week returns H5 heights build Tuesday into Wednesday offering a reprieve from daily chance of storms. After Tuesday being the coolest day of the week, temperatures ramp back up towards normal values in the lower 80s. A two standard deviation below normal trough establishes across eastern Canada Wednesday night through the balance of the week. This will return passing shortwave troughs permitting the return of precipitation under northwest flow. Much the case for this week, thunderstorm complexes could traverse the region given we are on the southern periphery of the trough, however confidence not high enough to warrant anything greater than climo pops. && .AVIATION /07Z SATURDAY THROUGH WEDNESDAY/...
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MVFR/IFR restrictions will improve briefly by mid-morning shortly before showers develop as a shortwave crosses the area. There is a chance of thunderstorms later in the afternoon but will largely hinge on instability. At this time devlopment looks less likely in the absence of a trigger and cloud coverage limiting surface-based instability. showers or so, one or two round of storms are possible. Handled with VCTS for much of the daylight hours for now, pending improved timing in future issuances. Gusty winds and hail will be possible with any storm. .OUTLOOK... Periodic restrictions are expected through the weekend in morning fog and daily rounds of thunderstorms.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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