Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 301 PM EST Sat Dec 23 2017 Valid 00Z Sun Dec 24 2017 - 00Z Tue Dec 26 2017 ...Heavy snow possible over parts of the Northeast and the Upper Great Lakes... ...Snow possible for part of the Cascades and the Northern/Central Rockies... ...Snow, rain, and freezing rain mixed over parts of the Northeast... A frontal zone dropping through the Intermountain West along with a wave of low pressure approaching from the Pacific will promote coastal rains for Washington, Oregon, and eventually northwest California with areas of snow across the Cascades and Interior Northwest, as well as, the northern/central Rockies over the next couple of days. Numerous Winter Weather Advisories and a handful of Winter Storm Warnings are in effect from Oregon to western Nebraska. Heavy snow is expected for portions of the Cascades, from the Wasatch Range to south of the Beartooths and for the Front Range and surrounding area. A clipper system will drop through the Northern and Central Plains; which will reinforce cold air over the central U.S. and the Great Lakes region. This does not bode well for travel over the next few days as precipitation will likely be a mix of ice and snow from the Great Lakes to New England. Please see WPC's winter weather products and discussion for more information pertaining to the winter weather hazards associated with this system. Arctic air will surge southward along the Northern Rockies and into the Northern Plains in the wake of the cold front moving through the Southeast and a secondary boundary dropping into the northern Plains on Sunday. Temperatures across this sector will plummet into the teens above zero, which on average will be 20 degrees below normal for late December, though no record lows or record cold high temperatures are anticipated until at least Monday. Widespread showers and thunderstorms from the Southern Plains to Lower/Middle Mississippi Valley and Tennessee Valley are due to warm, moist Gulf air advecting north ahead of a cold front. Air within the warm sector is high enough to threaten record high temperatures across portions of Louisiana and Mississippi this afternoon. With an expected slow eastern progression with this system, an axis of higher rainfall amounts is forecast to span from southern Arkansas to central Kentucky. Concerns for flooding are already elevated across this region - numerous counties are in a flash flood watch, with a handful of counties near the boot hill of Missouri in Flood/Flash Flood Warnings. Later today, the area of concern will shift to the eastern Tennessee Valley/Central Appalachians as the cold front shifts to the East. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php