Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 203 PM EST Mon Dec 16 2019 Valid 00Z Tue Dec 17 2019 - 00Z Thu Dec 19 2019 ...Winter weather spreading into the eastern Great Lakes, Northern Mid-Atlantic and Northeast tonight into Tuesday... ..Thunderstorms with locally heavy rains and severe weather likely across the South and Southeast tonight into Tuesday, while heavy rains and flash flooding possible from portions of the Tennessee Valley into the Central Appalachians... ...An Arctic blast expected across the Northern Plains/Upper Mississippi Valley and Upper Great Lakes Tuesday and Wednesday, while warm temps spread eastward from the lee of the Northern and Central Rockies... ...High winds likely from Santa Ana conditions across southern California into Tuesday... The winter storm that has produced widespread heavy snows from the Southwest across the Central Rockies, Central Plains, Mid Mississippi Valley and Mid West over the past few days will continue to press off northeastward tonight into Tuesday. This will bring heavy snow and accumulating ice potential from the eastern Great Lakes, Northern Mid-Atlantic and into portions of the Northeast and New England. A widespread region of National Weather Service Winter Weather Advisories are in effect across these regions. The trailing cold front from this storm is currently supporting widespread severe thunderstorms across the Lower Mississippi Valley and Lower Tennessee Valley this afternoon. This cold front will be pressing eastward tonight into Tuesday across the South and Southeast with additional thunderstorm activity likely along and ahead of the front bringing locally heavy rains and severe weather potential across these areas. Heavy rains and flooding will also be a threat with this storm across portions of the Tennessee Valley into the Central Appalachians through Tuesday. In the wake of this storm, an arctic blast will be pushing out of south central Canada and into eastern portions of the Northern Plains, the Upper Mississippi Valley and the Upper Great Lakes Tuesday and Wednesday. High temperatures are expected to be 15 to 25 degree below average across these areas Tuesday-Wednesday. High temperatures in the single digits likely Tuesday across northern North Dakota and northern Minnesota and across northern Minnesota, northern Wisconsin and the U.P. of Michigan on Wednesday. This cold front will also ignite lake effect snows across the Upper Lakes Tuesday and over the lower lakes on Wednesday. Locally heavy snows likely with these lake effect snow squalls. In contrast to the very cold temps across eastern portions of the Northern Plains, the Upper Mississippi Valley and the Upper Great Lakes, downslope/Chinook winds will spread eastward from the lee of the Northern Rockies and across the Northern High Plains Tuesday and southward into the lee of the Central Rockies and across the Central Plains Wednesday. These downslope winds will support much above average temperatures across the Northern High Plains Tuesday and across much of the Northern and Central Plains Wednesday. Strong Santa Ana wind conditions will persist through Tuesday across Southern California. Winds gusts of 35 to 55 mph possible, resulting in potential of downed trees and power lines, along with an increased fire weather threat. These Santa Ana wind conditions will diminish significantly by Wednesday as an area of low pressure moves into Northern California. Rain is possible across Northern California with this low on Wednesday, but amounts are not expected to be heavy. Oravec Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php