Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 227 PM EDT Wed Apr 19 2017 Valid 00Z Thu Apr 20 2017 - 00Z 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 persistent frontal boundary across the central and eastern U.S. will 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. The front will also bring a couple rounds of precipitation to a wide area through the next couple days. An area of low pressure across the central plains today is forecast to move east toward the Great Lakes tonight and Thursday, and into southern Ontario and Quebec by Friday. Showers and thunderstorms are possible tonight and Thursday from the central plains and mid/upper-Mississippi valley to the Great Lakes, Mid-Atlantic, and Northeast. Severe thunderstorms are possible through tonight across portions of the central plains and mid/upper-Mississippi valley, and on Thursday across portions of the Great Lakes. Please refer to products issued by the Storm Prediction Center for further details on the severe weather threat. Locally heavy rainfall is also possible. 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 Thursday night and Friday. By late Thursday, a second wave of low pressure is forecast to develop along the same frontal boundary across the southern plains as a strengthening upper-level disturbances crosses the Rockies. This will bring another round of scattered to numerous showers and thunderstorms from the southern and portions of the central plains to the lower/mid-Mississippi valley and Tennessee valley through Friday. Severe thunderstorms and heavy rainfall will also be possible Thursday and Friday from the southern plains to the mid-Mississippi valley. Farther west, and upper-level disturbance is forecast to move onshore in the Pacific Northwest tonight, spreading precipitation from the Northwest into the Intermountain West and northern Rockies through Thursday. 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. Ryan Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php