Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 432 AM EDT Fri Oct 30 2015 Valid 12Z Fri Oct 30 2015 - 12Z Sun Nov 01 2015 ...Flash flooding possible on Friday across portions of the Southern Plains... ...Severe thunderstorms possible for portions of Texas on Friday... ...Flash flooding possible on Saturday across portions of the lower Mississippi valley... ...Heavy rainfall expected for the Pacific Northwest ... An upper-level trough will move eastward, reaching central U.S. by early Sunday morning. A surface low pressure will materialize over Texas and will track across the Southern Plains and into the lower Mississippi Valley this weekend. Copious amounts of moisture will pump into the area ahead of the system and will aid in the development of numerous showers and thunderstorms over the Southwest, Southern /Central Rockies and the Southern Plains. Snow will be possible along the higher terrain in Colorado. The low pressure system and the plume of deep moisture will shift east toward the Gulf Coast and lower Mississippi valley on Saturday. Periods of heavy rain will likely bring widespread amounts of 2 to 4 inches for these areas, with up to 6 inches possible for south-central Texas -- may lead to the possibility of flash flooding for portions of the Southern Plains today and portions of the lower Mississippi valley Saturday and Sunday. Most of the eastern third of the U.S will be be cooler and unsettled through the weekend as a series of cold fronts sweep through. The region spanning from the Central/Northern Plains across the Great Lakes and into the Northeast will have widespread rain over the next couple of days, however, amounts will are expected to remain less than 1 inch. Snow showers possible in the higher elevations of the Northeast -- little to no accumulations are expected. The Pacific Northwest will be rather wet as a series of Pacific frontal systems, and a rather constant plume of moisture will affect the area through Saturday. Most of northwest Washington is under a flood watch as significant precipitation is forecast for the Olympic and Cascade Ranges along with the surrounding areas. Totals over the next 3 days will vary based on elevations. Lower elevations could see up to 4 inches by Sunday morning, 5 to 10 inches at the higher elevations of western Washington and northwestern Oregon. Isolated amounts up to 15 inches will be possible in the Cascades. Moisture will also spread into the northern Intermountain West with a combination of mountain snow and valley rain possible today and Saturday. The Northern Rockies of Idaho and Montana could see 1 to 6 inches by Sunday morning. Rapid runoff from the higher terrain will likely increase the threat for flash flooding. Refer to WPC's excessive rainfall statements for additional information. Campbell Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_wbg.php