Unsettled weather for the West, with a late season Atmospheric Riverimpacting California into the weekend...Precipiation chances continue for New England Friday.Warming trend for portions of the central/eastern U.S. into theweekend.Higher elevation/mountain snow showers and lower elevation coastal/valleyrain will continue across the West Thursday evening and into the dayFriday as a frontal system moves through the region, eventually stalling,and underneath energetic upper-level flow aloft. Precipitation amounts,especially further inland, should remain mostly light to moderate exceptin the vicinity of the boundary across the Great Basin and into thecentral Rockies were some higher snow accumulations and more widespreadlower elevation showers are expected. Then, along the West Coast, anamplifying upper-level trough/deepening closed low and the approach of astronger Pacific system will help usher in a late season influx of highermoisture/Atmospheric River into central and southern California beginningby late Friday. The best overlap of moisture and onshore/upslope flow willinitially be along the Transverse Ranges, where a Slight Risk of ExcessiveRainfall (level 2/4) is in place through Saturday morning. A few inches ofrainfall may lead to some flooding concerns, especially along terrainsensitive areas. The threat will continue into the day Saturday, expandingsouthward along the Peninsular Ranges, with another Slight Risk in effectas additional rainfall, on top of increasingly saturated conditions, willbring the threat for more instances of flooding. Some heavier rainfall isexpected over portions of central California, and spreading into the LowerColorado Basin by Saturday, but the flood threat looks to remain lower forthese regions for now. Some heavier snow is also forecast for higherelevations of the Sierra Friday and into the weekend. In the East, showers along the Coast should begin to come to an end fromsouth to north in the Carolinas/Mid-Atlantic Thursday evening as a coldfront pushes away from the coast. Rain, heavy at times, will linger intoFriday for coastal New England as an area of low pressure intensifiesoffshore and continues to advect additional moisture in. While the rainwill not be particularly intense, instances of flooding will remain aconcern with some higher water levels due to additional snowmelt/runoffexpected. The greatest risk will be through Friday morning, with a SlightRisk in effect, though some threat may linger into Saturday for DowneastMaine. Further inland, some snow will mix in, with some lightaccumulations possible through northern Maine. Precipiation should taperoff through the day Saturday as the low pressure system moves away. Anupper-level shortwave and accompanying surface frontal system passingthrough the Northern Plains will bring a wintry mix Friday, with someincreasing chances for accumulating snowfall along the Canadian borderfrom North Dakota into the Upper Midwest/Great Lakes. As the wave movesfurther east, shower and thunderstorm chances will increase Saturday alonga quasi-stationary frontal boundary through portions of the GreatLakes/Midwest. Increasingly moist southerly flow may bring some moremoderate to heavy showers as well as some thunderstorm chances by Saturdayevening.An expanding area of warmer, above average temperatures is expected forportions of the central U.S. Thursday, from the Southern Plainsnortheastward into the Middle Mississippi/Lower Ohio Valley, asupper-level heights rise across the region. Some chilly morning lows  intothe 30s are forecast for the Tennessee Valley into the SouthernAppalachians Thursday morning, with Frost Advisories in place for portionsof the regi