Area Forecast Discussion
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000 FXUS61 KPBZ 221158 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 758 AM EDT FRI JUL 22 2016 .SYNOPSIS... Hot and humid weather is forecast for today into early next week, along with intervals of scattered thunderstorms. && .NEAR TERM /THROUGH TONIGHT/... A line of showers and thunderstorms ahead of a shortwave should continue to move SE across the area this morning, with a continued weakening trend as they outrun the best instability and shear. Additional scattered thunderstorm development is expected this afternoon as a weak surface trough slowly advances south toward the region. With dry mid level air progged to move in this afternoon, sufficient instability and marginal shear, a few strong to severe storms are possible with damaging winds the main threat. The marginal outlook from SPC appears reasonable. Highs near 90 are expected for much of the area, though heat indices should remain near or below advisory criteria. Shower/storm chances should gradually diminish tonight as instability decreases, though low chances will continue overnight in proximity to the trough with it`s advancement to the I 70 corridor by morning. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... A weak boundary will stall out over the southern third of the forecast area by Saturday morning. Models continue to activate showers and thunderstorms along this boundary through the afternoon, but a lack of upper- level support and dry air through the column should limit development. Opted to continue with slight chance/isolated shower or thunderstorms south of Pittsburgh. Remaining mid-level moisture will clear the southern border by late Saturday, ending the low rain chances. Near-surface moisture and high surface dewpoints will linger, resulting in another warm and humid night with lows well above average. Surface high pressure will shift east Sunday as the next system moves through the southern Canadian Plains. This will return southerly flow, and re-enforce the warm and humid airmass. A few showers could develop across our western zones Sunday afternoon as the weak boundary returns north as a warm front. Heat indices Saturday and Sunday will reach into the mid and upper 90s for a majority of our forecast area, and approach 100 for a few of our southwestern counties. An HWO mention will be maintained for this. Warm and humid conditions will carry into the new work week, although an increase in clouds will limit high temperatures. A weak, sweeping cold front will drag across the area Monday, bringing a chance of rain for all, but the progressive nature of the system will limit amounts. && .LONG TERM /MONDAY THROUGH THURSDAY/... Rain chances will quickly dissipate in the wake of the cold front, Tuesday, bringing a return to dry conditions. The upper-level flow pattern will temporarily flatten to nearly zonal, as high pressure builds at the surface. Temperatures will moderate under the zonal flow aloft, but will remain a few degrees above normal. Consistent model agreement on the digging of a trough over the cornbelt in the latter part of next week. This will bring rain chances back to the forecast Thursday and Friday. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/... A line of thunderstorms with MVFR/local IFR restrictions should continue to advance across the region this morning with an approaching shortwave, though coverage should be more scattered across OH ports. Additional scattered thunderstorms are expected to develop this afternoon as a surface trough slowly advances toward the region. Maintained a VCTS mention for this as uncertainty remains in amount and timing of coverage. VFR should prevail much of tonight as instability decreases, though some patchy MVFR fog is possible with low level moisture in place. .OUTLOOK /SATURDAY THROUGH TUESDAY/... Restrictions will be possible late Sunday and Monday with crossing disturbances. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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