21.   Farther inland, freezing rain will glaze portions of the Columbia River Valley as the moist Pacific air begins to dislodge weighty cold air hovering near the ground.

22.   Farther south, Pacific air will stream inland, bringing snows to the Wasatch and the northern mountains of Arizona.

23.   Farther south, heat over the deserts of southern California and Arizona will recede only slightly as milder Pacific air gradually presses southward and patchy cirrus clouds drift overhead.

24.   Farther west, moisture laden Pacific air behind the front will ascend the mountains, leading to numerous showers on the western slopes of the Cascades and the Bitterroots.

25.   Following suit, areas of dense fog will shroud the immediate southern California coast on Saturday morning as cooler Pacific air forges onshore.

26.   Frigid arctic air will remain locked in central and northern Canada for the next several days as a vigorous jet stream delivers Pacific air across the nation.

27.   Heavy snow will fall on many mountain peaks from the Northwest to western Colorado as a surge of moist Pacific air accompanies a cold front.

28.   However, shifting weather patterns suggest that incursions of mild Pacific air will be replaced by Canadian chill in the week before Christmas.

29.   However, warmer weather will approach from the west as mild Pacific air moves inland.

30.   If not, a battle over Pacific air routes becomes a possibility.