Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 400 PM EST Sat Dec 20 2014 Valid 00Z Sun Dec 21 2014 - 00Z Tue Dec 23 2014 ...A very wet period is in store for the northwestern U.S... ...A stalled boundary will keep conditions unsettled over the Southeast... A powerful Pacific jet accompanied by anomalous moisture content will allow for very heavy rainfall across the Pacific Northwest coast with moderate to heavy snows over the interior terrain. This vast transport of moisture, also known as an Atmospheric River, is known for bringing some of the heaviest precipitation events to the western states. The current forecast suggests anywhere between 4 and 8 inches of precipitation will fall across the Washington/Oregon Cascades, mostly in the form of rain across the latter section of the mountain range. The WPC winter weather desk indicates that the Washington Cascades may see snow ranging from 1 to 2 feet through Monday evening. Farther inland, much of the Intermountain West and Central/Northern Rockies will get in on the action with similar accumulations across the Blue Mountains, Bitterroots, Sawtooth, Tetons, Wasatch, along with the Colorado Rockies. The mid-level energy tracking from the northwestern U.S. toward the Great Plains will eventually lead to the development of a robust system spinning over the Middle Mississippi Valley. However, this feature is not expected to be a large precipitation maker as a frontal zone along the Gulf Coast will rob most of the incoming moisture. Expect light snow/ice accumulations anywhere from the Northern High Plains eastward to the Upper Midwest. The other active system on the map is the aforementioned stalled frontal boundary across the Gulf of Mexico and along the southeastern U.S. coast. Weak disturbances within the southwesterly flow aloft will help spark areas of showers and thunderstorms along this front keeping conditions unsettled throughout the next couple of days. The heaviest axis of rainfall is expected along the Florida panhandle and just offshore of the Carolinas where waves of low pressures will track. Temperatures as a whole will be above normal throughout the period given the dominance of Pacific air masses into the country. Even in the wake of the closed low across the middle of the U.S., high temperatures over the Northern Plains should still reach the freezing mark. It is expected to become rather breezy though as the pressure gradient tightens over the Plains in response to the deep area of low pressure. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php