...Additional heavy to excessive rainfall could lead to flash floodingacross much of coastal California......Heavy rainfall likely over much of the Florida Peninsula for theremainder of the weekend......Colder than normal conditions across the eastern and southern U.S. willbe followed by a warming trend across the mid-section of the country...The West Coast will once again be the focus of inclement weather over thenext couple of days as more energetic low pressure systems from thePacific line up to push onshore.  The first system of concern has alreadybrought widespread moderate to locally heavy rain for the coastal PacificNorthwest and down into the northern half of California today (Saturday). The moisture will advance farther inland to bring a period of mountainsnow across the interior sections of the northwestern U.S. and northernRockies through Sunday.  A more potent low pressure system will quicklyfollow in its wake to deliver the next round of heavy precipitation, thistime mainly across California starting Sunday night/early Monday.  WPC hasa Slight Risk of Excessive Rainfall covering a good portion of northernCalifornia and central coastal California into Sunday and Monday, with aModerate Risk in effect for the Santa Barbara to Santa Maria region forthe same time period.  Very heavy snowfall will then impact the SierraNevada on Monday where a few feet of new snow can be expected. Elevation-dependent rain/snow will then spread northeastward into theGreat Basin on Monday.After a quick round of locally heavy snow Saturday morning, theMid-Atlantic states will clear out behind a departing low pressure system. Colder than normal conditions initially blanketing much of the easternand southern U.S. will be followed by a warming trend across themid-section of the country--emerging first over the northern Plains thengradually spreading south to reach Texas by Monday.  Meanwhile,lake-effect snows downwind from the Great Lakes will gradually taper offby Sunday.  Farther north, a clipper system sliding across southern Canadawill only bring light snow across the upper Midwest and upper Great Lakeson Sunday, before brushing the lower Great Lakes and northern New Englandon Monday.Meanwhile, rain and thunderstorms associated with a slow-moving front areforecast to expand across the Florida Peninsula through tonight.  BySunday, a low pressure center developing along the front over the Gulf ofMexico will traverse the Florida Peninsula later that night before movingout into the Atlantic on Monday.  Generally a couple of inches of rain,with locally higher amounts, can be expected with this system.