Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EST Mon Dec 09 2024 Valid 12Z Mon Dec 09 2024 - 12Z Wed Dec 11 2024 ...Heavy rain threat across the central to eastern Gulf Coast region today will expand and move up the East Coast late Tuesday into Wednesday morning... ...Periods of mixed rain and snow linger across interior New England through tonight... ...Snow/blizzard conditions across the northern High Plains will gradually taper off later today... ...Strong Santa Ana winds prompting critical fire danger across Southern California... ...Well above average temperatures will overspread the central and eastern U.S. as cold air surges into the western and then central U.S.... Increasingly active weather will progress toward the eastern U.S. through the next couple of days as a weather pattern reversal continues to unfold across the mainland U.S. One of the ingredients of this pattern change is manifested by an expanding area of moderate to heavy rain moving through the Ohio and Tennessee Valleys this morning with embedded thunderstorms across the Deep South. The associated jet stream aloft will send the rain rapidly northeastward across the Mid-Atlantic states today, reaching into southern New England tonight. Temperatures will be cold enough to support snow across northern New England Monday night into Tuesday morning before tapering off for the time-being Tuesday afternoon. Meanwhile, an extensive surge of cold air into the mid-section of the country will reinvigorate the jet stream across the Deep South on Tuesday, leading to an expanding area of moderate to locally heavy rain from the Gulf Coast into the Deep South and interior Southeast. Tuesday night into Wednesday morning will likely see the rain quickly expanding up the Appalachians and into the interior section of the Mid-Atlantic, and then up into New England with some ice possible at the onset. Meanwhile, organized lines of thunderstorms could form ahead of a potent cold front across the interior Southeast early on Wednesday along with sharply colder temperatures and blustery northwesterly winds behind the front. Across the northern High Plains, colder air and gale force winds behind a low pressure system have prompted winter weather advisories/warnings, Blizzard Warnings, as well as wind advisories/high wind warnings this morning. 4-7" of snow is expected across the northern High Plains. Meanwhile, strong onshore flow off Lake Superior will further enhance local snow totals across the Arrowhead of MN range where 9-12"+ totals are expected. On Tuesday, a more intense surge of cold air will be funneled southward from Alaska and western Canada into the Plains associated with an intensifying arctic high pressure system. A 'Blue Norther' cold front will be driving well through the Southern Plains into northern Mexico by Tuesday night, dropping temperatures into the 30s into southern Texas by Wednesday morning. Meanwhile, a reinforcing cold front will drop temperatures below zero degrees over the northern Plains by then. High temperatures will be about 5-10 degrees below normal across much of the Rockies, Southwest and eventually into the Plains. Across the western U.S., a cold surge directed through the Great Basin into the lower Colorado River Valley today will bring very strong Santa Ana winds into southern California by later today. Given dry/low humidity conditions already in place, Red Flag Warnings have been issued for the eastern Transverse and all of the Peninsular Ranges; as well as a Critical Fire (level 2 of 3) from the Storm Prediction Center. Winds of 35 to 45 mph in the valleys and gusts of 50 to 65 mph in the mountains will help fan any fires that do develop quickly and may reduce visibility with blowing smoke and dust adding to travel concerns in the region. Kong/Gallina Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php