Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 417 AM EDT Mon Mar 23 2015 Valid 12Z Mon Mar 23 2015 - 12Z Wed Mar 25 2015 ...Heavy precipitation expected across the Pacific Northwest coast... ...A winter storm is forecast to affect the Upper Midwest and Great Lakes on Tuesday/Wednesday... ...Severe weather will be possible over the Ozarks on Tuesday... The upper pattern setting up across the nation will feature a series of low-amplitude systems with Pacific air generally being the dominant air mass moving into the U.S. Throughout the next couple of days, the coldest air on the map should remain north of the international border with Canada. An active period of weather is in store for the northwestern states as a series of impulses track through the region. Enhanced onshore flow will drag a well-defined plume of moisture inland spreading moderate to heavy precipitation across the Pacific Northwest. As usual, the most concentrated activity should be confined to the favored upslope terrain with the heaviest forecast amounts over the Coastal Ranges and Cascades. The latest WPC winter weather desk outlook shows the heaviest snowfall over the Oregon Cascades, Sawtooth, and Tetons where a foot of snow is expected through Wednesday morning. All of this activity will translate eastward spreading unsettled conditions to the northern tier. Before the Pacific system moves toward the Northern Plains and Upper Midwest, an area of wintry precipitation is currently advancing through the Middle Mississippi Valley. Some of the early morning activity has produced some lightning within the heavier snow bands showing how dynamic this initial system is. This system should continue migrating eastward spreading a few inches of snow to Chicago, Illinois before the impulse aloft weakens by Monday evening across the Ohio Valley. In its wake, there will be a brief lull before the Pacific energy reaches the Upper Midwest by Tuesday and into Wednesday. While a majority of the system will produce rain, enough cold air is expected to loom along the northern tier to spread snow and ice to Minnesota eastward through the Great Lakes. 4 to 6 inches of snow may be possible along the Minnesota/Wisconsin border accompanied by accumulating ice. The other aspect of this system is the potential for severe weather across the Ozarks. A strong cold front is forecast to march eastward which will be intercepting copious amounts of Gulf moisture. The latest Storm Prediction Center forecast suggests severe thunderstorms may be break out on Tuesday with the activity continuing into the following day. Elsewhere, a slow-moving frontal boundary will gradually exit the southeastern U.S. This will bring the threat for showers and thunderstorms with the areal coverage of convection diminishing in time as the system weakens and moves offshore. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php