The persistent deep trough of low pressure will remain entrenched over the forecast area for one more day, with some weak disturbances rounding the base of the trough. What this will amount to is very cold arctic air at all elevations. Some light snow will occur across mainly the southern mountains and adjacent valleys as moisture and a little instability overrun the cold dome of air. Little accumulation is expected. Temperatures will remain well below normal through mid-week, with clearing skies tonight as the trough shifts eastward over the Great Plains and Midwest. High pressure will approach the area and build along the west coast starting tomorrow, with drier air moving in from the west. This dry air and high pressure will remain in control through the rest of the week into the following week. Strong inversions will rebuild over the valleys, keeping very cold air trapped, while the higher elevations will see a gradual moderation of temperatures up towards seaso! nal values by the end of this week.   (Please visit for more information.)