Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 238 PM EST Sat Dec 29 2018 Valid 00Z Sun Dec 30 2018 - 00Z Tue Jan 01 2019 ...A new Pacific storm system will bring locally heavy snow across the Pacific Northwest and the Rockies... ...Much colder than normal temperatures will be focused over much of the West and High Plains going through New Year's Eve... ...Very mild temperatures will arrive across portions of the Southern and Eastern U.S. along with a new storm system that will bring additional heavy rain and thunderstorms... A new storm system dropping in across the Pacific Northwest will advance gradually southeast and inland across the Intermountain Region for tonight and Sunday. This will bring a new round of rain along the coast and some heavy snow for the higher terrain including the Cascades and the central and northern Rockies. Some locations over the far northern Rockies including the Bitterroots will see as much as 1 to 2 feet of new snow going through Sunday. By New Year's Eve, the moisture and energy associated with this system will then quickly advance east out across the northern Plains and the upper Midwest. A stripe of light to moderate snow and perhaps even some freezing rain will impact these areas making for locally hazardous travel conditions. Meanwhile, much colder air will filter south in behind this system with many areas of the Intermountain West and the High Plains high temperatures well below freezing and as much as 15 to 25 degrees below normal. Farther east, the weather will again tend to trend much milder and wetter, as a storm system develops over the lower Mississippi Valley region on New Year's Eve and lifts north up across the lower Great Lakes region. Southerly flow ahead of a low center and attendant cold front will result in notably warmer temperatures lifting north from the Gulf Coast states and overspreading much of the Eastern half of the nation. High temperatures especially along and just west of the Appalachians including the Tennessee and Ohio Valleys will be as much as 15 to 25 degrees above normal on New Year's Eve. With the influx of warmer air will also be a substantial amount of moisture, and the expectation is for a rather widespread area of heavy rainfall and embedded thunderstorms to impact the Southern and Eastern U.S. from the lower and middle Mississippi Valley east to the Ohio Valley and Mid-Atlantic region. Some localized runoff and flooding concerns will be possible given rainfall amounts of as much as 1 to 3 inches with this next system, and based on this, the Weather Prediction Center has issued a Marginal Risk of excessive rainfall. In addition to the rainfall, there will be a localized concern for some severe weather, especially across the Gulf Coast states, and this is where the Storm Prediction Center has highlighted a Marginal Risk of severe thunderstorms. The concerns for heavy rainfall and severe weather will both need to be closely monitored over the next couple of days. Orrison Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php