Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 328 AM EST Thu Dec 10 2015 Valid 12Z Thu Dec 10 2015 - 12Z Sat Dec 12 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... A front extending from Upper Mississippi Valley to the Central Plains then westward across the Rockies to low pressure over the Great Basin will move eastward to the Lower Great Lakes/Middle Mississippi Valley by Friday evening. As the system moves from the Upper Midwest into East-Central Canada light rain will develop over parts of the Northern Plains into the Upper Great Lakes on Thursday morning moving to the Upper Great Lakes by Friday morning before moving into Canada by Friday evening. Moisture from the Gulf of Mexico will start to overrun the boundary over Western Ohio Valley and expand into the Great Lakes on Friday morning into evening. Some scattered light rain will develop over parts of the Lower Mississippi Valley by Friday evening, too. As cold air filters in over the Northern Plains/Upper Mississippi Valley, light snow will develop over the area on Friday. Meanwhile, low pressure over the Northern Intermountain Region will move southeastward to the Central Plains by Friday. Onshore flow associated with the system will aid in producing rain over the Pacific Northwest to Central California on Thursday. Snow will also develop over the higher elevations of the Cascades and Sierras as well as the Northern Intermountain Region/Northern Rockies on Thursday. On Friday the rain will expand southward to Southern California and eastward to parts of the Southwest/Southern Rockies. Snow will likewise expand into parts of the Northern High Plains and parts of the Central/Southern Rockies also on Friday. Elsewhere, upper-level energy moving over the Northeast on Thursday morning will move out over the Western Atlantic by Thursday evening. The energy will trigger light rain over parts of the Northeast on Thursday. In addition, upper-level energy moving over Southern Florida will aid in producing scattered light rain over parts of Southern Florida. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php