Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 257 PM EST Tue Nov 17 2020 Valid 00Z Wed Nov 18 2020 - 00Z Fri Nov 20 2020 ...Wet and snowy weather continues across the Northwest... ...Light to moderate lake effect snow occurring downwind of the Lower Great Lakes... ...Chilly temperatures from the Mid-Atlantic to the Northeast, pleasantly mild in the Plains and Mississippi Valley... An active weather pattern over the northwestern U.S. keeps the onslaught of coastal/valley rain and mountain snow in the forecast through Thursday. Portions of the northern Sierra Nevada and Sawtooth mountains are under Winter Storm warnings through Wednesday evening. While these are the only areas under Winter Storm Warnings, many other mountain ranges including the Cascades can expect anywhere from 1 to 2 feet of snow through Thursday evening. In addition to the snow, blustery conditions are also anticipated with High Wind Warnings and Wind Advisories in place from the northern Great Basin and central Oregon to the Pacific Northwest coastline. Expect drier conditions to arrive by week's end as high pressure returns, giving the region a breather from their recent stretch of unsettled weather. Heading east, lake effect showers are unfolding downwind of the Great Lakes this afternoon as a frigid Canadian air-mass races over the warm lake waters. The heaviest snow totals should transpire just downwind of Lakes Erie and Ontario where 3 to 6 inches (locally higher amounts possible) are expected through tonight. Lighter accumulations are possible in the higher elevations of the northern and central Appalachians. The switch will be switched to "off" on the lake effect snow machine by Wednesday morning as high pressure builds in over the eastern third of the Lower 48. This makes for a mostly dry Wednesday and Thursday throughout the East, with the lone exception being the Sunshine state of Florida where spotty passing showers are possible along the eastern coastline. The aforementioned frigid air-mass responsible for the development of lake effect snow bands and showers are also forcing temperatures to plummet 10 to 20 degrees below normal on Wednesday. In fact, some interior locations of the Southeast are under Freeze Warnings and Frost Advisories. Much of the Northeast can expect chilly highs in the 30s on Wednesday, with 20s for highs in northern New England. Meanwhile, an upper-level ridge traverses the Rockies and Heartland ahead of an upper trough that is the root cause to the Northwest's unsettled pattern. Underneath the ridge, temperatures of 10 to 30 degrees above normal are likely from the Intermountain West to the Plains, with the highest anomalies centered in the northern and central parts of the Plains Wednesday. A handful of record warm high and low temps are possible from the Southwest to the Great Plains. Additionally, fire danger will be elevated across the Southern High Plains today given the warm and dry conditions. The upper level ridge warming up the interior locations of the U.S. eventually reaches the East Coast by the end of the week. Mullinax Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php