The setup for this persnickety weather was a slow moving upper-level trough over the 4-coners with an upper-level ridge over the west coast and Pacific Northwest. Both of these features are what meteorologists call "positively tilted" in that they tilt toward the east as you move northward. Often one can find an upper-level front between the ridge and trough in a scenario like this. An upper-level front is a region with a strong temperature gradient and wind speed in the middle and upper troposphere that is not necessarily connected with the surface.
|NAM analysis valid 1800 UTC (1100 MST) 8 Jan 2011|
Notice how the winds at the base of the stable layer (near 775 mb) are light (5 knots), but at 700 mb they are much stronger (30 knots). 700-mb is near 10,000 feet. These are the winds that buffeted the ridges during the day. If you were skiing in the Wasatch today, you were embedded in the upper-level frontal zone and bore the full brunt of the strong winds in the associated wind-shear layer on the ridge tops. These winds were particularly nasty along ridges and saddles that were oriented perpendicular to the northerly flow.
Pacific moisture sneaking over the ridge, which can be seen in the 700 mb analysis (lower-left hand panel above) as an area of higher relative humidity crossing southern BC and then diving southward through Montana, Idaho, and Wyoming, provided the moisture for the altostratus clouds that refused to dissipate today. A few sun breaks in the morning provided the best ego-building turns of the day.