Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 312 PM EST Thu Dec 10 2015 Valid 00Z Fri Dec 11 2015 - 00Z Sun Dec 13 2015 ...Heavy rain possible over the Pacific Northwest to Northern California... ...Heavy snow for the Oregon Cascades, the Sierras, and the Salmon River/Sawtooth range in Idaho... ...Severe thunderstorms and heavy rain possible for the portions of the Southern Plains... Two low pressure systems will move across the country over the next few days bringing widespread precipitation to more than half of the lower 48. The first system will track across the Great Lakes and through the Northeast/New England by late Saturday. Scattered to widespread showers will accompany the front as it passes through. Rain, possibly snow on the northwest side of the low center, will linger over the Upper Midwest and Great Lakes through Friday afternoon. Moisture from the Gulf of Mexico will start to overrun the boundary over Western Ohio Valley and expand into the Great Lakes throughout the day on Friday, which may result in scattered areas of light rain for the lower Mississippi Valley. The second system will cross the Rockies and move into the Central Plains by Friday. Onshore flow associated with the system will aid in producing rain over the Pacific Northwest to Central California - with snow over the higher elevations of the Cascades, Sierras as well as the Northern Intermountain Region/Northern Rockies. Periods of heavy rain can be expected for coastal areas of the Pacific northwest. A mix of rain and snow will be possible for much of the Intermountain West, Great Basin and Four Corners regions through the weekend. Snow will be heavy at times for the Oregon Cascades, the Sierras and the Salmon River/Sawtooth range in Idaho. Conditions will be favorable for thunderstorm activity this weekend once reaches the Central/Southern Plains. The Storm Prediction Center has highlighted a large portion of the Southern Plains as having a slight risk for severe thunderstorms on Saturday. Please refer to the Convective Outlook issued by SPC for additional information. This region may also have periods of heavy rain with these storms. Upper-level energy moving over Southern Florida will aid in producing scattered light rain over parts of Southern Florida. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php