Area Forecast Discussion
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000 FXUS61 KPBZ 220149 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 949 PM EDT THU JUL 21 2016 .SYNOPSIS... Warm temperature, increased humidity, periodic thunderstorm chances can be expected into early next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... 900pm update...convection to the northwest has all but dissipated as the activity has run into a wall of stability and a capped atmosphere. Would expect just additional cloud cover overnight. Pops and temperatures have been updated. Previous discussion. Changes for the near term period included precip probability adjustments for the potential that ongoing convection over the Great Lakes Region survives mid level warmth, or spawns outflow that ploughes into the diurnally destabilizing airmass over the area. An escalation through "chance" numbers was thus included for the evening hours, and maintained tonight basically north of Interstate 70 as isolated to scattered convection may accompany the actual shortwave. Limitations include the aforementioned CAPE- robbing mid level warmth, fading diurnal support, and lack of inflow support. Morning lows in the moderating airmass were progged close to the previous forecast, i.e. about 5 degrees above the averages. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY NIGHT/...
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A better chance for rain is expected with another disturbance on Friday. Improved boundary layer moisture and instability with a marginally cooler mid level should be more conducive for showers and storms, although limited deep layer shear should keep the threat of severe isolated. Thereafter, a shortwave ridge extending from the broad Central CONUS high is forecast to continue the warmth and humidity over the immediate area. Dewpoints in the upper 60s, to around 70 F with temperature about 7 to 10 degrees above the averages will generate heat indices in the 95 to 100 degree range for Saturday and Sunday afternoons. A Hazardous Weather Outlook mention was maintained for the Ohio counties as those heat indice projections are flirting with the 100 degrees heat advisory criteria. Convection in the warmth will be limited by warm mid levels and a lack of forcing, so small PoPs will be the rule with hedges dependent of weak disturbances and mesoscale effects.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/... A stronger disturbance is forecast to carve the ridge over the Upper Ohio early next week. That system will provide the next, best chance of rain with a shortwave ridge quickly rebuilding in its wake. The flatter flow pattern will moderate temperature in this time frame, although readings are expected to remain above the averages. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/...
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VFR conditions expected overnight. Thunderstorms remain a possibility tomorrow with low-level moisture increasing, however, with warm air aloft and the lack of a strong trigger, the threat looks low and coverage should be minimal. .OUTLOOK /FRIDAY NIGHT THROUGH TUESDAY/... Restrictions will be possible in thunderstorms Friday evening, and again late Sunday and Monday with crossing disturbances.
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&& .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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