Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 238 PM EST Tue Jan 29 2019 Valid 00Z Wed Jan 30 2019 - 00Z Fri Feb 01 2019 ...Arctic air plunging south from Canada will drive temperatures down to as much as 30 to 40 degrees below normal over the Midwest and Ohio Valley by Wednesday... ...Dangerous wind chill values of as low as 40 to 60 degrees below zero are expected over portions of the northern Plains, Midwest and Ohio Valley tonight and Wednesday... ...Very heavy lake-effect snow will occur downwind of the Great Lakes... Low pressure will gradually pivot north across southern Ontario tonight before then lifting into western Quebec by Wednesday evening. Meanwhile, low pressure developing over the central Mid-Atlantic region this evening will lift northeast along or just inland of the New England coast through Wednesday morning. This redeveloping wave will bring a swath of accumulating snow to the interior areas of the Northeast where as much as 6 to 12 inches of snow can be expected before the low center pulls away into southeast Canada by Wednesday night. The story in behind the departing low pressure over New England will be the advance of extremely cold air coming down through the Midwest and through the Ohio Valley as an Arctic cold front crosses the region. Arctic air associated with a strong area of high pressure dropping south from Canada will allow high temperatures across these areas to be as much as 30 to 40 degrees below normal on Wednesday. This coupled with locally strong winds will result in wind chill values of as much as 40 to 60 degrees below zero. This bitterly cold airmass will modify a bit as it arrives across the Mid-Atlantic and Northeast through Wednesday night and Thursday, but temperatures will be considerably below normal and with dangerously cold wind chills expected. Wind Chill Advisories and Warnings are in effect across a large area of the northern Plains, Midwest, Ohio Valley and parts of the northern Mid-Atlantic to address the extremely low wind chills that are anticipated. Meanwhile, the fetch of deep layer Arctic air over the Great Lakes region around the south side of the aforementioned low centers pulling away through southeast Canada will set the stage for significant lake-effect snowfall over the next couple of days. Snowfall amounts locally in excess of 1 foot can be expected downwind of Lake Superior and Lake Michigan involving areas of the Upper Peninsula of Michigan and western Lower Michigan respectively through Thursday. However, even heavier snow will be possible downwind of Lake Erie and Lake Ontario where a somewhat more favorable low level fetch of wind will support some areas seeing in excess of 2 feet of snow. This will include areas of western New York, and especially areas near and just south of Buffalo, NY relative to Lake Erie, but also the Tug Hill plateau region downwind of Lake Ontario. A large area of Winter Storm Warnings are in effect for these areas. Elsewhere, the Western U.S. will see considerably milder temperatures by comparison and generally dry weather. One exception will be California as a storm system offshore moves east and brings rain inland by Thursday across central and southern California with an emphasis on the coastal ranges. Rainfall amounts are not expected to be too heavy, but locally over 1 inch of new rain is expected through Thursday with the heaviest amounts likely focusing on the Transverse Ranges of southern California. Temperatures associated with the rain in California will be a little below normal, but should be normal to somewhat above normal across the remainder of the West. Orrison Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php