Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 155 PM EST Fri Dec 27 2019 Valid 00Z Sat Dec 28 2019 - 00Z Mon Dec 30 2019 ...A major winter storm will produce moderate to heavy snow over the south-central Rockies and across the northern Plains with freezing rain from the central Plains to the Upper Midwest... ...Strong to severe thunderstorms and areas of heavy rainfall may develop on Saturday across portions of the southern Plains and Lower Mississippi Valley... A major winter storm ejecting out of the Southwest U.S. will cross the south-central Rockies tonight and then lift northeast across the central Plains and Upper Midwest this weekend. Low pressure associated with the system will interact with sufficient cold air for a swath of heavy snow from eastern Colorado to Minnesota, and winter storm watches and warnings are already in effect for many of these areas. The expectation is for snowfall amounts of as much as 12 to 18 inches with the heaviest totals from northern Nebraska to northwest Minnesota where isolated totals near 20 inches will be possible. Strong winds will likely develop on the back side of the evolving low pressure center, and this coupled with the heavy snowfall is expected to create near-blizzard conditions with significantly reduced visibilities at times. Travel conditions as a result will become difficult to impossible. Areas just to the southeast of the heavy snowfall axis, including areas from eastern Nebraska to northern Wisconsin, are expected to see a period of sleet and freezing rain, with the potential for locally in excess of a quarter inch of ice accretion. Farther south across the southern Plains and through the Lower Mississippi Valley, a cold front will be approaching and then crossing these areas. The front will be interacting with much warmer air and a fetch of moisture from the Gulf of Mexico that will help to support the threat of strong to severe thunderstorms and areas of heavy rainfall. The Storm Prediction Center and Weather Prediction Center have highlighted a Marginal Risk of severe weather and excessive rainfall respectively with a focus predominantly on the Lower Mississippi Valley on Saturday. On Sunday, this threat will shift northeast into the Tennessee and Ohio Valleys. Elsewhere across the continental U.S., showers will impact the Pacific Northwest as a weakening cold front approaches the region. Scattered showers and a few thunderstorms are likely for the Florida Peninsula with a sustained period of moist southeasterly Atlantic flow. Generally mild weather is expected for much of the East, although there will be sufficient cold air pooling over the Northeast for a developing threat of freezing rain by the end of the weekend as moisture from the upstream winter storm over the Midwest begins to arrive. A greater threat of significant icing is expected to set up for early next week across eastern New York and interior areas of New England. Orrison Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php