Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 313 PM EST Wed Dec 20 2017 Valid 00Z Thu Dec 21 2017 - 00Z Sat Dec 23 2017 ...Heavy snow over parts of the Central Rockies... ...Snow possible from parts of the Northern Plains across the Great Lakes into the Northeast... ...Heavy rain possible over parts of the Lower Mississippi Valley/Tennessee Valley... Strong storm over Great Basin/Central Plains will lift northeastward to the Ohio Valley by Friday. The system will produce coastal rain and higher elevation snow over parts of the Pacific Northwest with snow over parts of the Northern Intermountain Region/Northern Rockies and the Great Basin. The rain and snow will come to an end over the Pacific Northwest/Northern Intermountain Region overnight Wednesday. In addition, snow over the Northern Plains will spread into the Upper Great Lakes also overnight Wednesday as snow moves into the Central Rockies ending overnight Thursday. On Thursday, snow and some rain will develop over parts of the Northern/Central Plains into the Upper Great Lakes. Overnight Thursday, snow will move into the Northeast while rain moves into parts of the Ohio Valley and parts of the Northern Mid-Atlantic by Friday morning. The associated warm front will be dammed up against the Appalachians Thursday afternoon into Friday. With the damming, there is a risk of rain/freezing rain may develop over parts of the Lower Great Lakes/Northern Appalachians also overnight Thursday into Friday. Additionally, as the associated cold front moves from the Plains into parts of the Mississippi Valley, moisture from the Gulf of Mexico will flow northeastward over the Southern Plains into the Lower Mississippi/Tennessee Valleys on Thursday afternoon into Friday. Likewise, overnight Thursday into Friday, showers and thunderstorms will develop over parts of the Southern Plains into the Lower Mississippi/Tennessee Valleys. More to Follow Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php