Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 236 PM EST Mon Dec 09 2024 Valid 00Z Tue Dec 10 2024 - 00Z Thu Dec 12 2024 ...Widespread heavy rain threat from the central to eastern Gulf Coast region, northeastward across all of the east... ...Active Lake effect snows to begin Wednesday and continue through Thursday downwind of the Lakes... ...Record warm morning lows likely along the east coast Wednesday morning... ...Arctic air to surge south into the Northern Plains/Upper Mississippi Valley region late Tuesday into Wednesday... ...Critical to Extreme fire weather danger across portions of Southern California... The upper level flow will undergo significant amplification across much of North America over the next few days, producing active and impactful weather events across nearly all of the Lower 48. This amplifying pattern will be comprised of a building upper ridge along the West coast and a deepening upper trof across the central to eastern U.S. Precipitation currently falling across portions of the central to eastern Gulf coast and the Northeast will be followed a more widespread heavy precipitation event developing Tuesday night into early Wednesday from the central Gulf coast into the Upper Ohio Valley. This area of precipitation will continue to expand eastward during the day Wednesday across all of the east, producing widespread heavy precipitation from the central to eastern Gulf coast, across the Southeast, Mid-Atlantic, Northeast and New England. With much of these areas currently in moderate to extreme drought conditions, this rainfall will be beneficial. Still, given the potential for periods of heavy rains over a short period, there will be a threat of localized flash flooding, especially in more urbanized regions. This heavy rain will be occurring along and ahead of a strong front pushing east across the eastern U.S. on Wednesday. Ahead of this front, there is the potential for widespread record high morning low temperatures on Wednesday across the Southern Mid-Atlantic, Mid-Atlantic and portions of the Northeast. In the wake of this front, much colder temperatures will begin to push across the Great Lakes from west to east, beginning on Wednesday. This will ignite active lake effect snows, initially downwind of lakes Superior and Michigan on Wednesday and then downwind of lakes Erie and Ontario Wednesday night into early Thursday. Before these lake effect snows diminish by early Friday, snowfall totals of 1 to 2 feet are possible in the favored lake effect snow regions across portions of northwest and western New York State, far northwest Pennsylvania, far northeastern Ohio, the Upper Peninsula of Michigan and the western portions of the Lower Peninsula of Michigan. The above mentioned lake effect snows will be driven by arctic air that will be first surging east southeastward late Tuesday into early Wednesday across the Northern Plains into the Upper Mississippi Valley and then eastward trough the Great Lakes into the Ohio Valley on Wednesday. While there are not expected to be any records with this arctic outbreak, temperatures will be much below average on Wednesday across the Northern Plains into the Upper Mississippi Valley. These much below average temperatures will then push farther southeast into the Great Lakes and Ohio Valley region on Thursday. Across these regions, high temperatures will be 10 to 25 degrees below average during the height of the cold temperatures during Wednesday and Thursday. In contrast to the wet and cold conditions across portions of the north central to eastern U.S., dry condition and milder temperatures are in store across the West coast, Great Basin and Rockies region. However, the dry air, low relative humidities and windy Santa Ana conditions over Southern California will produce critical to locally extreme fire weather conditions. These fire weather conditions will be greatest in the higher terrain areas to the north and east of the Los Angeles to San Diego region. 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. Across these areas, red flag warnings are currently in effect, affecting nearly 13 million people. Oravec Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php