Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 AM EDT Thu Apr 20 2017 Valid 12Z Thu Apr 20 2017 - 12Z Sat Apr 22 2017 ...Severe thunderstorms and heavy rain possible for portions of the central U.S... ...Rain and snow possible for much of the western U.S... ...A mix of rain and snow possible for the Great Lakes region and northern Maine... Two persistent frontal systems -- one traversing through southern Canada/northern U.S and a second lifting the Southern/Central Plains into the Great Lakes/Northeast, will generate scattered to widespread precipitation, as well as, serve as a dividing line between above average temperatures across much of the eastern U.S. through Friday, and below average temperatures from the central and northern plains to portion of the Upper Midwest. An area of low pressure will track through through the Upper Midwest/Great lakes region today and into southern Ontario and Quebec Friday/Saturday. As associated front advances eastward, showers and thunderstorms are expected to fire along and ahead of the boundary. Severe thunderstorms will be possible across portions of the Texas panhandle and west-central Oklahoma today and across portions of the lower Great Lakes/Ohio valley. Please refer to products issued by the Storm Prediction Center for further details on the severe weather threat. In addition to strong or severe thunderstorms, locally heavy rainfall may also occur. Along the northern fringes of this system, sufficient cold air will be in place for rain to mix with or change to snow from portions of northern Minnesota east to portions of the Upper Peninsula of Michigan through Thursday, and potentially across portions of northern Maine tonight and Friday. Another wave will develop over the Southern Plains on this boundary and will strengthen as upper-level disturbances cross the Rockies. Showers and thunderstorms will trigger across much of the the Southern/Central Plains to the lower/mid-Mississippi valley and Tennessee valley through Friday. Severe thunderstorms and heavy rainfall will be possible from the southern plains to the mid-Mississippi valley. Onshore flow combined with an upper-level disturbance moving across the Pacific Northwest will spread precipitation from the Northwest into the Intermountain West and northern Rockies today. Precipitation will fall in the form of snow at the higher elevations with rain and potentially even a few thunderstorms in the valleys. Heavy snow is possible at the highest elevations. Campbell/Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php