Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 237 PM EST Sat Dec 18 2021 Valid 00Z Sun Dec 19 2021 - 00Z Tue Dec 21 2021 ...Heavy rain and severe thunderstorm threat this afternoon and evening from the southern Plains to Ohio Valley... ...Moderate to heavy snow expected across northern New England this evening into Sunday; freezing rain from upstate New York to central New England... ...Heavy snow to impact the Cascades and far Northern Rockies today, lingering into Monday... A low pressure system is lifting through the Ohio Valley Valley today and its attendant cold front is slowly passing through the Ohio/Tennessee Valleys, the Lower Mississippi Valley and the Southern Plains today; which is acting as a focus for showers and thunderstorms. Moderate to heavy rainfall is occurring over parts of Texas and Louisiana with another cluster of storms over Alabama, Florida and Georgia- both areas WPC has highlighted as having an elevated threat for excessive rainfall and local flooding concerns. This system is forecast to intensify as it tracks toward the New England coast by tonight, which will reduce the risk for excessive rainfall along the Gulf while bringing a round of snow and some mixed precipitation across the lower Great Lakes. Moderate to heavy snow is forecast to overspread northern New England from west to east as the low pressure wave intensifies and tracks near the southern New England coast. Areas from upstate New York to central New England should see sleet, freezing rain, and/or snow tonight before the low quickly exits out to sea on Sunday. The wintry mix is expected to taper off/diminish across that region by Sunday afternoon with showers and thunderstorms continuing for the East Coast and Southeast. A few inches of coastal/lower elevation rain is expected across the coastal Northwest along with with heavy snow in the Cascades as another round of moisture moves onshore. Local amounts of 2 feet of snow will be possible in the highest elevations of the northern Cascades. With the system settling a bit into Oregon on Sunday, it will elevate the risk for excessive rainfall and localized runoff concerns. WPC has issued a Marginal Risk area for excessive rainfall for parts of western Oregon. This system is then forecast to push back northward Sunday night into Monday as a cyclone is forecast to expand and push northward off the West Coast. Some of the heavier precipitation will then spread northward from Oregon into Washington by Monday, with the chances for snow expanding eastward into northern Montana and Idaho possibly totaling up to 10 inches. Colder air will enter the Northern Plains Sunday night into Monday behind an Alberta clipper. Snow associated with the cold front is forecast to be light. Elsewhere, rain chances are expected to increase across southern Texas later this weekend as a low pressure system is forecast to develop along a meandering front in the western Gulf of Mexico. Campbell/Kong Graphics are available at https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php