Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 226 AM EST Thu Jan 21 2021 Valid 12Z Thu Jan 21 2021 - 12Z Sat Jan 23 2021 ...Heavy rain and possible flash flood threat decreasing across portions of the Desert Southwest Thursday morning... ...Heavy rain developing across the Lower Mississippi Valley/Southeast on Thursday... ...Much need snows expected across the Sierra and Wasatch Friday into Saturday... ...An active Lake effect snow pattern begins Thursday and continues through Friday downwind of the Great Lakes... A strong mid to upper level low will be pushing eastward along the Southwest U.S./northwest Mexico border region on Thursday and then accelerate across the Southern Plains and into the Southeast on Friday. This system is currently producing heavy rains over portions of the Desert Southwest with this heavy rain and flash flood threat continuing into Thursday morning before diminishing by Thursday afternoon. While conditions improve over the Southwest, they will become increasingly wet farther to the east from portions of the Southern Plains, into the Lower Mississippi Valley and Southeast Thursday into Friday. Widespread rains are expected across these areas with the heaviest totals in a stripe from far eastern Texas, across central to northern Louisiana, central to southern Mississippi, southern Alabama into southern Georgia. Aside from eastern Texas into far northwest Louisiana, much of this region has had below average precipitation this month resulting in stream flows at or below normal levels. This should reduce the threat of flash flooding with only a marginal risk depicted across portions of this region Thursday into Friday. Another storm system is expected to push into northern California on Friday and move eastward into the Great Basin on Saturday. This system will bring some much needed heavy snows to the Sierra of California and Wasatch of Utah. Much of California into the Great Basin is well below average in precipitation this season, experiencing severe to exception drought levels. Two cold fronts will be sweeping across the Great Lakes Thursday into early Friday producing favorable cold westerly to northwesterly flow across the unfrozen Great Lakes. Lake effect snow showers will increase in coverage and intensity Thursday and continue through Friday. Locally heavy snowfall accumulation are likely with the heaviest totals expected over western and northwestern portions of New York State, downwind of Lakes Erie and Ontario, northern portions of the Lower Peninsula of Michigan, downwind of northern Lake Michigan and along the north coast of the Upper Peninsula of Michigan, downwind of Lake Superior. Oravec Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php