Everything remains on track for the big storm in California and eventually more October snow for the central Wasatch.
Current forecasts show a very well-defined precipitation system moving across California and the Great Basin Sunday and Monday. The GFS forecast valid 0600 UTC 25 October (0000 MDT Monday) shows heavy precipitation (>1" water equivalent in 3 h) in the Tahoe area, to the southeast along the Sierra Nevada, and then along the cold front in the northern Great Basin.
|Source: Center for Western Weather and Water Extremes|
The time height section for Alta helps summarize the next few days and sheds some insights into the the atmospheric river forecast for Utah. Recall that time increases to the left in this diagram. First up is today's storm, which will bring 2-5" of wet-snow scraps to upper Little Cottonwood. On Monday, warm, moist southwesterly flow develops aloft. Freezing levels (thick blue line) rise to over 11,000 feet, which sounds scary, but the low levels are drier with lower relative humidity levels. This, and the lack of any well define warm-frontal feature to drive large scale lift, is why the GFS isn't generating much in the way of precipitation until the arrival of the cold front later in the day.
|Source: Rutz, Steenburgh, and Ralph (2014)|