Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 259 AM EST Mon Feb 19 2018 Valid 12Z Mon Feb 19 2018 - 12Z Wed Feb 21 2018 ...Heavy snow over the Northern Plains into the Central Rockies and the Upper Great Lakes... ...Heavy rain and flooding possible for portions of the Midwest Monday and likely for Southern Plains and Mid-Mississippi Valley on Tuesday... ...Rain/freezing rain possible from of the Middle/Upper Mississippi Valley to the Upper Great Lakes and northern Maine... ...Temperatures will plummet across the Northern Rockies and the adjacent Northern and Central Plains, averaging 15 to 40 degrees below seasonal average... Widespread snow will persist through late Tuesday across portions of the Wasatchs, Central/Northern Rockies and into the High Plains as a strong cold front southward through the Rockies and into the Central U.S. Accumulations will be heavy at times, especially for the Central Rockies. Arctic air will continue to spill into the northern states allowing a significant drop in temperatures over the next couple days. Another cold front dropping south from Canada will reinforce snow generation across the Northern Plains and portions of the Upper Great Lakes. A vast area from coastal Oregon/northern California to upper Michigan have Winter Storm Warnings and Winter Weather Advisories. The front's progression through the central U.S. will be fairly slow over the next few days which will set the stage for a potentially long duration wet period for portions of the Southern/Central Plains and the Mississippi Valley. A steady plume of warm Gulf moisture will transport northward along this boundary. Scattered to widespread rain and thunderstorms are forecast from Texas to the Great Lakes region. An axis of 2 to 4 inches is forecast from eastern Texas to lower Michigan, with pockets of 5+ inches over northeast Texas to the Ozarks. Thunderstorms will have little movement and/or track over the same area; which will greatly increase the likelihood of flooding conditions. A moderate risk for excessive rainfall is in effect for Tuesday into Wednesday. Additionally along the rain/snow line, rain and freezing rain will develop over parts of the Central Plains into parts of the Upper Great Lakes Monday morning into Tuesday. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php