Area Forecast Discussion
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793 FXUS61 KPBZ 221608 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1208 PM 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/...
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A line of showers and thunderstorms ahead of a shortwave should continue to move SE across the area through early afternoon. Earlier hi res model guidance didn`t handle this so well, but pops have been adjusted to reflect the current and future placement based on radar trends. It remains in question how much development we will have north of the current broken line this afternoon, as lingering cloud cover may prohibit destabilization. Opted to leave the chance pops that were inherited for now. If anything does develop, we will still need to monitor the threat for strong storms with marginal shear present. Rain and cloud cover this morning will most likely keep much of the region from hitting 90 today. Shower/storm chances should gradually diminish tonight as instability decreases, though low chances will continue overnight in proximity to the shortwave trough with it`s advancement to the I 70 corridor by morning.
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&& .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 /15Z 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. && $$ is the U.S. government's official web portal to all federal, state and local government web resources and services.