Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 314 PM EST Wed Jan 17 2018 Valid 00Z Thu Jan 18 2018 - 00Z Sat Jan 20 2018 ...Heavy rain possible for parts of the Pacific Northwest/Northern California... ...Heavy snow possible for parts of the Cascades and the Sierras... ...Snow possible for the Northern Rockies... A deep upper-level trough over the Mid-Atlantic will move eastward out over the Western Atlantic by Thursday evening. The system will produce light snow over parts of the Southern Mid-Atlantic into the Carolinas that will begin to slowly end over the area overnight Wednesday into Thursday morning. Another area of snow over the Northeast will also end overnight on Wednesday. Additionally, another area of upper-level energy over South-Central Canada will move southeastward over the Great Lakes to New England Coast by Friday. The energy will produce light snow over a small part of the Upper Mississippi Valley on Thursday morning ending Thursday afternoon. The energy will also trigger light snow over parts of the Northeast late Thursday night into Friday. Meanwhile, a front moving onshore over the Pacific Northwest/Northern California will slowly move inland to parts of the Northern Plains to the Great Basin and Southern California by Friday. Moisture will flow into the Northwest and Northern California that will move southward to Southern California by Friday. Rain will develop over the Pacific Northwest Coast on Wednesday evening that will expand inland to the Northern Intermountain Region/Northern California by Thursday afternoon with snow over the higher elevations of the Cascades into the Northern Rockies. Overnight Thursday, snow will develop over the Sierras into parts of the Great Basin northeastward into the Northern High Plains by Friday. In addition, the rain will move into Central California on Thursday that will begin to move into Southern California by Friday. In the wake of the front, onshore flow over the Northwest will aid in the development of coastal rain and higher elevation snow over the region Thursday afternoon into Friday. Elsewhere, upper-level energy over North-Central Mexico will move eastward to the Western Gulf Coast by Friday morning. As the system moves eastward, moisture from the Western Gulf of Mexico will begin to stream northward over the Western Gulf Coast and the Southern Plains overnight Wednesday. The energy and moisture will start to produce light rain over parts of the Western Gulf Coast Thursday afternoon into Friday. Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php