Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 401 AM EST Sun Nov 01 2015 Valid 12Z Sun Nov 01 2015 - 12Z Tue Nov 03 2015 ...Heavy rain possible across portions of the Pacific Northwest through Tuesday... ...Snow possible over the higher elevations of the Sierras, Northern Cascades, and Northern Rockies... ...Heavy rain possible across portions of the Mid-Atlantic on Monday... The low pressure system that has brought heavy rain to the Gulf states over the past several days will persist in its eastward trek through the lower Mississippi Valley and Deep South. This system will continue to pull very moist air in, resulting in numerous showers and thunderstorms over the Gulf of Mexico and the southern tier of the U.S. today and extending northward into the Mid-Atlantic by Monday. Periods of heavy rain will increase the threat of flash flooding across the Mid-Atlantic region -- please refer to the Excessive Rainfall Outlook from WPC for additional information. Forecast 3-day totals show the axis of the highest amounts will span from New Orleans, LA to Norfolk, VA, where amounts of 2 to 5 inches will be possible. A series of upper-level disturbances will move through the Pacific Northwest, resulting in multiple, fast-moving cold fronts to sweep through the Intermountain West and into the Northern and Central Plains. A plume of very moist air will accompany the front southward to Southern California by Monday. Rain is expected for parts of the Pacific Northwest, Northern California, Northern Rockies and the High Plains. The Precipitation will expand into Central/Southern California and into the Great Basin/Central Rockies by Monday. Snow will also develop over some of the higher elevations of the Sierras, Northern Cascades, and Northern Rockies. The highest moisture totals are forecast for the mountains -- 1 to 3 inches for the Cascades, 2 to 4 for the Sierras and the Central/Northern Rockies. Lower elevations will generally have less than 1 inch. Flash flooding will be possible for western Washington and northwest Oregon through Monday morning. The Upper Mississippi Valley, Great Lakes, Northeast and Mid-Atlantic will showers through Monday as the front moves through. Amounts will generally be light for the northern tier of the U.S. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php