Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 210 PM EST Fri Dec 27 2024 Valid 00Z Sat Dec 28 2024 - 00Z Mon Dec 30 2024 ...Atmospheric river to bring low elevation rain and high elevation snow to the West through the weekend... ...Increasingly wet pattern forecast to develop over the eastern U.S. this weekend... ...Mild and much above average temperatures will persist across most of the country... A slow moving frontal boundary will move into the Pacific Northwest tonight and direct a plume of Pacific moisture at the West Coast, which will be the next atmospheric river to impact the West. Moisture will spread from the coast across the Intermountain West, resulting in widespread low elevation rain and high elevation snow. Heavy rain with intense rain rates could produce instances of flooding in coastal Oregon and northern California, and there is a Slight Risk of Excessive Rainfall (level 2/4) for this region on Saturday and Sunday. Heavy mountain snow could cause moderate to major impacts for the higher elevations of the Cascades and northern Rockies. Heavy snow combined with strong winds could lead to blowing and drifting snow with reduced visibility, and travel conditions may be very difficult to impossible. The recent wet weather pattern across the Northwest and likelihood of additional widespread heavy precipitation amounts this weekend will result in increasing stream flows and soil saturation levels, leading to an increasing threat of river flooding, and rock and mudslides. Precipitation is also forecast to spread across the eastern U.S. this weekend as a series of frontal systems move northeast from the Lower Mississippi Valley to the Great Lakes and Northeast. The first frontal system will bring rain to the Lower Mississippi, Tennessee, and Ohio Valleys and mixed wintry precipitation to the Upper Midwest today. Rain will spread towards the East Coast as another frontal system develops over the Lower Mississippi Valley on Saturday, and rain will continue through Sunday as the second system tracks northeast. Rain will likely be beneficial for many areas that are experiencing drought conditions, especially in the Lower Mississippi Valley and along the East Coast. However, locally heavy rain may also result in isolated instances of flash flooding. While stormy weather dominates the West and East, much of the Central U.S. and Southwest will remain dry through the weekend. Most of the nation will experience much above average temperatures over the weekend, with high temperatures reaching 15-25 degrees above average and low temperatures reaching 20-30 degrees above average. This will be a continuation to the above average pattern for areas west of the Mississippi River, but a reversal of the overall below average pattern that has dominated areas east of the Mississippi during December. This much above average pattern will support the potential for record high morning low temperatures across the Midwest, Mid-Atlantic, and Northeast. Dolan Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php