Area Forecast Discussion
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000 FXUS61 KPBZ 250418 AFDPBZ Area Forecast Discussion National Weather Service Pittsburgh PA 1218 AM EDT Thu May 25 2017 .SYNOPSIS...
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Slow moving low pressure will keep rain in the forecast through early Friday. Rain chances return for part of the weekend with low pressure.
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&& .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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Ascent with increasing shortwave support ahead of approaching low pressure, and increasing moisture should continue to result in an increase in showers again overnight. Gusty SE winds around 25kt should continue along the ridges with elevated low level flow and a temperature inversion. Temperatures are expected to only drop a couple of degrees from current levels with the cloud cover and rain.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY NIGHT/... Widespread morning rain will subside early in the day as a closed upper low deepens in the Ohio Valley and a dry slot asserts itself. As the moist boundary layer in the wake of the morning rain has a brief window to heat, cold air will be advected aloft, leading to steepening mid-level lapse rates and increasing instability despite only a minimal change in surface temperature. Convection-allowing models suggest that showers and storms will be generated quickly in this increasingly-unstable airmass, with a cluster of storms expected to fill in the dry slot by mid- afternoon Thu. Instability is not expected to be sufficient for organized severe weather, but moderate rain rates will be possible in any storms. By Friday, the upper low will have shifted toward New England with northwesterly flow in control and drier air arriving. This respite will be rather short-lived, however, as the H5 ridge axis will shift through the area by Saturday with deep swly flow becoming established. This shift will allow increasingly- humid and warmer air to arrive for the weekend. However, it will also bring an increasing chance for showers and thunderstorms. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... The pattern going into next week looks to continue to amplify as an upper low again drops into the Mississippi Valley with a downstream ridge popping up rapidly along the eastern seaboard. The Ohio Valley will be stuck between these two areas, with broad southwesterly flow remaining in place and abundant moisture streaming toward the area. As a result, chances for convection will remain in the forecast with temperature near normal. Of interest in the long term is that synoptic models are offering hints at a series of MCSs developing in the Plains and moving ewd toward the Ohio Valley along the nrn edge of the instability axis. These MCSs could impact the region Saturday and Sunday during a busy holiday weekend, so anyone with outdoor plans should monitor forecasts toward the end of the week. && .AVIATION /04Z THURSDAY THROUGH MONDAY/... Conditions will deteriorate overnight from general VFR to MVFR with occasional rain showers. General MVFR is expected on Thursday, with more passing showers/storm. .Outlook... Areas of non-VFR through Thursday in showers and possible thunderstorms and again for the weekend. && .PBZ WATCHES/WARNINGS/ADVISORIES... MD...None. OH...None. PA...None. WV...None. && $$

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