Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 306 PM EST Tue Dec 29 2020 Valid 00Z Wed Dec 30 2020 - 00Z Fri Jan 01 2021 ...Heavy snow for Iowa, Southern Wisconsin, and West-Central Michigan... ...Rain/Freezing rain from the Central Plains into the Midwest; Heavy Rain in Deep South... ...Heavy snow for the Cascades and the Northern Intermountain Region... An amplified upper-level trough which is currently diving through northwestern Mexico will cross the Sierra Madre and eventually spawn a new surface low pressure system Thursday evening. As the upper-level trough expands, and eventually splits, it will stretch the surface low pressure system out from the Central Plains and into the Great Lakes region tonight. Heavy snow is expected to spread from the Great Plains into the Upper Midwest/Great Lakes through Wednesday, where 4-8 inches of snow is likely with the possibility of localized amounts exceeding 8 inches. Ice is expected from the Middle Mississippi Valley into the Midwest with up to 0.1 inches of ice possible to accumulate around the Iowa-Illinois border. Winter Storm Advisories and Warnings are currently in effect from the Plains into the Midwest. Tonight, scattered to isolated thunderstorms are expected to spread from the Central/Southern Plains to the Midwest and Mississippi Valley tomorrow and eventually the eastern third of the country on Thursday. A Slight Risk of Excessive Rainfall leading to Flash Flooding is in effect for parts of the Southern Plains and Lower Mississippi Valley on Wednesday. Heavy snow is likely to develop over western Texas tomorrow as cold air surges south on the backside of the system. Between 4-8 inches of snow is likely to fall over this area through Thursday. As the Upper-level trough splits into two distinct pieces of energy, the northern stream will weaken while the southern stream develops a new system over the Southern Plains. The northern stream will produce some snow and rain over the Lower Great Lakes and Northeast Wednesday night into Thursday, while the southern stream is likely to continue pulling Gulf moisture and producing heavy rain from the Southern Plains to the Lower/Middle Mississippi and Tennessee Valleys on Thursday. A Slight Risk of Excessive Rainfall is in effect over parts of the aforementioned area as a result. Meanwhile, heavy snow and rain will impact the Pacific Northwest as a deep area of low pressure approaches the region on Wednesday. Up to 2 feet of snow may fall over parts of the Cascades with isolated amounts exceeding that figure possible. Around a foot of snow is likely over parts of the Northern Rockies during this period as well. Kebede Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php