Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 429 AM EDT Wed Apr 11 2018 Valid 12Z Wed Apr 11 2018 - 12Z Fri Apr 13 2018 ...Major storm system to bring heavy snowfall across parts of the northern Rockies and into the northern High Plains by Friday... ...Temperatures well above normal expected to spread from the Southwest and southern Plains today, into the Ohio Valley by Thursday... ...Critical to extreme fire weather conditions possible across parts of the Southwest into the central and southern High Plains... Precipitation should develop this morning to the north of a surface low as it progresses eastward from the northern High Plains to the Great Lakes region by Thursday. Light accumulating snowfall will be possible across far northern parts of the northern Plains, the Upper Mississippi Valley and upper Great Lakes. Moderate to locally heavy rainfall and embedded thunderstorms will be possible Thursday into Friday across parts of the Upper Midwest and eventually into the Northeast. The bigger weather story will be a strong upper level system making its way inland across the Northwest U.S. by late Wednesday. This will drive a cold front across the Western U.S., eventually spinning up a deep cyclone across the central Plains by early Friday. Widespread precipitation will accompany this system and is expected to initially bring heavy snowfall to the Cascade and Sierra Nevada mountain ranges on Wednesday. However, by Thursday, heavy accumulating snowfall will spread into the Northern Rockies and northern High Plains where upwards of a foot or more of snow is in the forecast through Friday morning and winter storm watches have been posted. Snowfall will spread eastward into the northern Plains and northern Mississippi Valley by Friday morning as well, with organized moderate to locally heavy rainfall to the south. Behind the cold front, temperatures should be well below normal which will bring down snow levels across the entire intermountain West, bringing snow showers to even parts of the lower elevations as well. Ahead of this system, temperatures across the central and southern Plains will be very warm, with afternoon highs expected to be as much as 10 to 20 degrees above normal from the Southwest into the southern and central Plains on Wednesday, spreading into the Ohio Valley by Thursday. Within this warm airmass, a dryline should set up across the Plains states with very low relative humidity values and gusty winds expected behind the boundary across the Southwest into the high Plains. Combined with possibly record breaking warmth, this will lead to dangerous fire weather conditions. The Storm Prediction Center has highlighted much of this region as critical to extreme in their outlook for Thursday and widespread red flag warnings are in effect. Santorelli Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php