Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 421 PM EDT Fri Oct 20 2017 Valid 00Z Sat Oct 21 2017 - 00Z Mon Oct 23 2017 ...Heavy snow possible over the Northern Cascades into parts of the Northern Rockies... ...Heavy rain possible over the Pacific Northwest... ...Heavy rain possible over the Southern Plains/Lower Mississippi Valley... A front over the Northern High Plains extends roughly southwestward to the Great Basin will slowly move eastward to the Upper Great Lakes/Middle Mississippi Valley and parts of the Southern Plains by Sunday. Overnight Friday, showers and thunderstorms will develop along and ahead of the boundary over parts of the Upper Mississippi Valley in to the Central/Southern Plains that will slowly move eastward to the Upper Great Lakes/Upper Mississippi Valley into the Middle/Lower Mississippi Valley and parts of the Southern Plains by Sunday morning. In addition, moisture from the Western Gulf Coast will flow northward over the Southern Plains/Lower Mississippi Valley that will protrude into the Upper Mississippi Valley/Upper Great Lakes through Sunday. Weak upper-level energy over the Southern Plains will aid in producing showers and thunderstorms over parts of the Western/Central Gulf Coast through Saturday afternoon. Meanwhile, strong onshore low-level flow will stream moisture into the Pacific Northwest will aid in producing rain over parts of the Pacific Northwest with snow over the higher elevations of the Cascades through Saturday morning. Rain and higher elevations snow will develop over parts of Northern California into the Northern Intermountain Region/Northern Rockies into parts of the Great Basin and Central Rockies through Saturday afternoon. On Saturday, the snow levels will rise over the west as upper-level ridging moves onshore. Additionally, moisture will surge onshore over the Pacific Northwest producing rain, heavy at times, over the Northwest into the Northern Intermountain Region/Northern Rockies Saturday afternoon into Sunday. ...More to Follow... Ziegenfelder Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php