Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 411 AM EDT Mon Oct 31 2016 Valid 12Z Mon Oct 31 2016 - 12Z Wed Nov 02 2016 ...Heavy rain possible over parts of Northwest Washington and the Cascades... ...Snow possible for the highest elevations of the Sierras, Cascades, and Northern Rockies... ...Highs will be 10-30 degrees above average for most of the Plains... A low pressure system will cross the Rockies today, move eastward through the northern and central Plains on Tuesday and into Midwest, Upper Midwest and Great Lakes region by Wednesday. Scattered to widespread rain will develop along and ahead of the front. The highest amounts are expected to set from the Midwest to the Great Lakes on Wednesday as that portion of the front becomes nearly stationary over the central Plains. Flash flooding may become a concern on Wednesday. Much of the Plains states will continue to have much warmer temperatures than usual. Many locations will have highs ranging 10 to 30 degrees above average through at least midweek. Portions of eastern Texas and Oklahoma will have scattered showers and thunderstorms as a cold front slides southward through the central and southern Plains. Otherwise, most of the southern-tier states will remain fairly dry under the surface high pressure. Tropical moisture and onshore flow off the Atlantic will aid in producing showers and thunderstorms over part of Southeastern Florida through Monday afternoon when the tropical moisture moves south of the area. A steady stream of anomalous moisture will be directed toward the British Columbia and Washington coast through midweek and will interact with multiple waves moving through the Pacific Ocean. Widespread rain will extend from the Coastal Mountains of British Columbia southward to portions of the Northwest Washington, the Olympics, the Cascades, and northern California today- focusing primarily over the Olympics and the Cascades on Tuesday and Wednesday. A mix of rain and snow ifs forecast for the higher elevations of Washington. Periods of heavy rainfall will likely increase the risk for flash flooding conditions today. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php