Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 231 PM EST Mon Nov 18 2013 Valid 00Z Tue Nov 19 2013 - 00Z Thu Nov 21 2013 ...Moist conditions across the Intermountain West.... ...Colder conditions invading the Northwest/Northern Plains on Wednesday... A deep cyclone moving through eastern Canada and a strengthening high pressure system in its wake will team forces and sweep a defined frontal zone across the western Atlantic slowly southward through Florida through Wednesday evening. Thunderstorms are expected to focus near the quasi-stationary front from northeast Mexico and southern Texas eastward across the Gulf of Mexico into Florida over the next couple days. The cold air in the wake of the cyclone driven across the unfrozen Great Lakes will spread snow showers across Michigan late Monday, shifting eastward into northern and western New York and northern New England Tuesday into early Wednesday morning. Conditions will become increasingly wet across the northwestern states as a Pacific front and associated moisture in its wake washes onshore on Monday as cold air spreads into the region aloft. Showers and thunderstorms should erupt skyward within this unstable airmass, with snows at higher elevations and rains near valley floors. A strengthening surface high moves into the region from western Canada, leading to colder conditions across the Northwest and northern Plains by Tuesday night. Within the cold air mass, forced ascent within a low-level upslope flow regime will lead to light to moderate snows along eastern slopes of the northern Rockies across central Montana Tuesday into Wednesday. Roth Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php