Unsettled weather for the West Friday as heavy snow continues for theSierra and spreads into the Great Basin and Rockies.Widespread thunderstorms shift from the Southern Plains to the LowerMississippi Valley/Gulf Coast today through Saturday, with a threat forsevere weather and flash flooding.Mild, well above average temperatures will persist across centralportions of the country this weekend.Mountain snow and a rain/snow mix for lower elevation valleys willcontinue across the West as an upper-level trough and accompanying surfacefrontal system will push eastward through the Great Basin and Rockies. Asecondary upper-level trough/area of low pressure offshore of the PacificNorthwest will also keep weather unsettled along the West Coast. Heavyhigher elevation snow is expected for many of the local mountain rangesacross the West including in California, the Great Basin, and the Rockies,which will likely see at least a foot of new snow through Sunday morning.Accumulations is expected to be lighter for most lower elevations, and anysnow that mixes in should lead to little to no accumulations. Some heaviershowers will be possible along the northern California/southern Oregoncoast where thunderstorms are expected. As the system advances further tothe east precipitation chances will decrease for California and the GreatBasin on Saturday meanwhile the heavy snow across the Northern/CentralRockies will persist. However, the first wave of heavy precipitationassociated with another Atmospheric River may begin to impact portions ofCalifornia as early as Saturday night, and likely by Sunday morning.Warm moist air will advect northward from the Gulf of Mexico into theSouthern Plains ahead of an approaching upper-level trough/surface frontalsystem moving through the West Friday. Isolated shower and thunderstormswill become more widespread by tonight. Some severe thunderstorms arepossible for central Texas as cooling temperatures aloft with theapproaching trough should lead to sufficient CAPE, along with expectedstrong wind shear, for some more robust updrafts. There is a Slight Riskfor severe storms in effect for most of central Texas per SPC with themain threat being large hail. Additionally, these storms are expected toorganize into a line that will be capable of producing heavier downpoursand an isolated risk of flash flooding. The potential for storms willcontinue eastward into the Lower Mississippi Valley on Saturday where adeveloping coastal low may help to locally enhance stormcoverage/intensity, leading to a bit higher threat of heavier rain andflash flooding. WPC has a Slight Risk of Excessive Rainfall in effectalong the central Gulf Coast. The progressive nature of the system willbring clearing conditions through the region late Saturday night/earlySunday morning as storm chances increase across the Southeast and Florida.Meanwhile central portions of the country will have an amplifiedupper-level ridge in place that will maintain above average temperaturesfor the Plains and the Midwest. Daily maximums will range from the 30s to40s for the Northeast and the Great Lakes, the 40s and 50s for theNorthern Plains and the Ohio Valley, the 50s and 60s for the CentralPlains and Carolinas, and the 60s and 70s for the Southern Plains andSoutheast. Temperatures will remain on the cooler side of average acrossmuch of the West given the upper-level trough, cloudy cover andprecipitation. Highs mainly in the 40s for the Great Basin, 50s for thePacific Northwest and northern California, and 60s for the DesertSouthwest and southern California.