Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 229 AM EST Sat Jan 18 2025 Valid 12Z Sat Jan 18 2025 - 12Z Mon Jan 20 2025 ...Winter storm to bring moderate to heavy snow to the Mid-Atlantic and Northeast Sunday... ...Snow showers with moderate accumulations continue Saturday through the central Rockies and adjacent central/southern High Plains... ...Arctic front brings dangerous cold to much of the nation this weekend... Moisture lifting northward ahead of a storm system/cold front pushing through the eastern U.S. will bring wintry precipitation to the north and rain and thunderstorms to the Southeast Saturday. A light to moderate wintry mix is expected to move from the Great Lakes into the Appalachians and interior Northeast, with mostly light rain showers elsewhere in the Ohio Valley/Southeast and along the East Coast. An enhanced flow of Gulf moisture over northern Florida will bring some more intense showers and thunderstorms Saturday night with locally heavy rainfall and the risk for some isolated flash flooding. A changeover to snow is expected Saturday night for the Ohio/Tennessee Valleys following cold frontal passage, though accumulations should generally remain light. Then, an upper-level shortwave traversing the southern U.S. will help to encourage the development/deepening of an area of low pressure as it moves off the coast of the Mid-Atlantic. This will lead to an enhanced swath of snow to the northwest of the low track beginning early Sunday morning across the Appalachians and continuing into the day Sunday from the northern Mid-Atlantic to New England. The swath of heaviest snow (5-8"+) will likely stay just to the north and west of the I-95 corridor. However, 3-6" of snow with locally higher amounts is expected from northern Maryland through Boston. Lake-effect snow will also continue this weekend for favorable locations downwind of the Great Lakes with strong northwesterly flow in place following the frontal passage. Elsewhere, snow showers will continue Friday for portions of the Rockies and adjacent central/southern High Plains in post-frontal upslope flow. Moderate totals of 3-6" are possible in vicinity of the Raton Mesa. Otherwise, the rest of the central/western U.S. will be mostly dry this weekend. Besides the impactful winter weather, dangerously cold temperatures spreading across much of the Lower 48 this weekend and into next week will be the other big weather story. Arctic air will plunge southward Saturday over the Rockies, Plains, and Midwest following the cold frontal passage, and will reach the East Coast Sunday night as the front moves off into the Atlantic. Forecast highs by Sunday range from below zero to the single digits in the northern Plains/Upper Midwest, the teens and 20s across the central Plains and Midwest, the 20s and 30s for the southern Plains and Lower Mississippi Valley, and the 40s along the western and central Gulf Coast. These temperatures will spread to the East Coast for highs Monday, just beyond the forecast period. Dangerously cold wind chills of 30-55 degrees below zero are expected across the Rockies, northern Plains, and Upper Midwest Sunday and continuing into next week. This will pose a life-threatening risk of hypothermia and frostbite to exposed skin. Wind chills below zero will reach as far south as Oklahoma and the Tennessee Valleys. Temperatures will remain near average west of the Rockies, with 30s and 40s for the Interior West/Pacific Northwest, the 50s and 60s in California, and the 60s and 70s in the Desert Southwest. Putnam Graphics available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php