Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 352 AM EDT Sun Oct 02 2016 Valid 12Z Sun Oct 02 2016 - 12Z Tue Oct 04 2016 ...Heavy rain possible over parts of the Northern Rockies/High Plains... ...Heavy rain possible over parts of the Pacific Northwest Coast... ...Temperatures will become 10 to 20 degrees below average over parts of California into the Great Basin and the Northern Rockies... The deep upper-level low over the Great Lakes/Ohio Valley is expected to weaken and propagate eastward toward the northern Appalachians by Monday - resulting in the surface front pushing offshore. Scattered to widespread rain, with a few embedded thunderstorms, is forecast for much of the lower Great Lakes and the Northeast through Tuesday. Another deep upper-level low just off the Pacific Northwest Coast will move southeastward to the Great Basin by Monday morning. Coastal areas of Washington and Oregon may have periods of heavy rainfall over the next couple of days - amounts of 1 to 3 will be possible. Much of the Intermountain West and eastern portions of the Great Basin will have rain and thunderstorms - with snow in the favored areas of higher terrain. As the upper-level trough moves inland, the snow levels will fall over parts of the Cascades and Sierras producing wet snow. Likewise as the trough moves even farther inland, the snow levels will fall over parts of the Northern/Central Rockies producing wet snow at highest elevations late tonight into Monday. The surface low pressure system associated with the upper trough will push into northern/central Plains, then lift north-northeastward. Widespread precipitation is expected across Montana, the Canadian Prairie and from the central Plains to the Upper Midwest. The heaviest precipitation will be along and north of the the occlusion that is expected to set up over Montana - 3 day precipitation totals of 1 to 3 will be common, with local areas up to 5.5 inches. Excessive rainfall over Montana may increase the risk for flash flooding. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php