Synopsis... Multiple system, most of them weak and moisture-starved in this rather zonal flow pattern, could affect the area over the forecast period.
Short Term (Mod-Wed)... Watching a weak cold front to the north and a weak upper-level disturbance to the southwest. For the cold front, progressive model runs move the southern extent of rain farther north, but keeping chance of showers and t'storms for northeast. And for the other system, we were impressed by the verification of WRF 12Z of showers and t'storms in northern Illinois around 4Z Monday, so our forecast for Pittsburgh is probably too conservative on rain. On Tues. night, another weak system approaches the area, and with this the WRF 12Z (Sunday) and SREF 21Z have been the most impressive with rain, while other runs are almost rain-free. Our forecast remarks call for slight chance of showers, but wx icons are cloudy/dry.
Long Term (Thurs-Fri)... A larger system (but still just a short-wave) enters the picture Thursday. Models are consistently showing a decent amount of moisture and rain as Gulf of Mexico moisture seems more accessible with this than with the systems previous. Timing at this point looks to be rain entering west PA during the afternoon/evening Thursday, exiting east sometime in the morning or early afternoon.
Scott Sieron
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