Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 253 AM EST Sun Jan 07 2018 Valid 12Z Sun Jan 07 2018 - 12Z Tue Jan 09 2018 ...Heavy precipitation expected to impact much of California on Monday... ...Ice accumulations are likely as freezing rain spreads from the Missouri valley through the Ohio/Tennessee valleys and into the Mid-Atlantic... ...Bitter cold remains over the East Coast on Sunday with potential for more records... A large pattern shift is underway as the country will move toward a more Pacific dominant flow regime. Amplification in the flow across the Pacific should usher in a very impressive upper low toward the central California coast by late Monday. In advance of this system, abundant subtropical moisture should stream northeastward toward the coast with increasing onshore flow expected. As usual, local orographics will play a key role in focusing heavier precipitation amounts which includes the coastal ranges extending from north of Los Angeles up into northern California. Additionally, a separate axis of heavy rain and snow will be likely across the Sierra Nevada range with up to a foot of snow possible through Tuesday morning. Among the major city hubs, the San Francisco Bay Area could see a brunt of the heavy rainfall with over 2 inches possible during the period. Overall, mudslides and other associated hydrologic issues will be likely anywhere across the state where burn scars exist from the active fire season in late 2017. While the rain is welcome after a slow start to the season, such hydrologic concerns will also need to be monitored as well. A sharpening upper trough pushing through the Southern Plains on Sunday evening will give way to a forming closed low which spins through the central Gulf Coast the following morning. Strong vertical motions underneath this cyclonic circulation will spread moderate rainfall into the Ozarks. Meanwhile, heavier amounts are likely across southern Louisiana/Mississippi where strong low-level convergence should become established along a meandering warm front. Along the northern extent of the precipitation shield, residual low-level arctic air which has not been scoured out may lead to some freezing rain issues. While overall precipitation amounts will be on the light side from the Missouri valley eastward into the Ohio/Tennessee valleys and Mid-Atlantic region, any accumulations of ice could lead to some hazardous road conditions. Given how long much of this region was entrenched in arctic air, it may take longer than expected to warm the surface to change precipitation over to rain. Except for the frigid weather expected along the East Coast on Sunday, much of the country will be on the milder side given the dominance of Pacific air masses. With an arctic ridge of high pressure in place early this morning over the northeastern U.S., overnight readings may dip below 0 degrees from the upper Mid-Atlantic northward as well as into the Central Appalachians, Ohio valley, and lower Great Lakes. While many locations have seen winds go calm, some locations across the northeastern states have a breeze in conjunction with the frigid temperatures. Thus, widespread wind chill warnings and advisories are in place through at least the morning hours. Little relief is expected during the day as highs stay below freezing as far south as eastern North Carolina. Another day of records will likely be approached or broken, particularly for the frigid overnight lows. However, a warm up is in store for next week with the entire country expecting temperatures anywhere from climatology to around 10 to 20 degree above it. These largest departures from average can be found in the High Plains where downsloping flow will prevail. Rubin-Oster Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php