Forecasts of easterly downslope winds in northern Utah have improved considerably in recent years due in part to improved numerical modeling, improved monitoring, and better understanding. Nevertheless, there's always more to be learned.
Amongst the oddities of our most recent event is the duration of the easterlies. Below are 750 mb (near crest-level for the northern Wasatch) wind analyses for 1200 UTC (0600 AM MDT) yesterday and today showing a dramatic drop off in the strength of the easterly crest-level flow.
Although this dropoff can also be seen in mountain-top and pass observations from the Wasatch Range, the corresponding dropoff in wind speed at the base of the Wasatch Mountains is weaker. For example, at the top of the Strawberry Bowl at Snowbasin Saturday night, winds were generally around 50 mph with gusts to 70. Meanwhile, in Farmington (US-89 at Park Lane), winds were just a bit stronger. During the day yesterday, winds at both sites weakened commensurately. However, last night and this morning we clearly entered a new regime. While the flow at the top of Strawberry Bowl weakened, winds of about 30 mph with gusts to 40-50 mph persisted at Farmington.
This potentially suggests two differing regimes for flow dynamics across the Wasatch. In the first, strong flow near the crest plunges into the lee, but experiences only a small acceleration (Saturday night and Sunday morning). In the second, the plunging flow strongly accelerates into the lee (last night and this morning). At least in this event, the latter does not lead to damaging winds, but that's not necessarily the case in all events.
Of course there is always the possibility that the localized nature of the Strawberry Bowl observing site makes it somewhat unrepresentative of the flow moving across the Wasatch Range immediately east of Farmington. It's unfortunate that we don't have a wind observing site in that part of the Wasatch Range and perhaps installing one should be a high priority for the state given the severe impact these events have on the northern Wasatch Front.
It would also be helpful to have soundings taken during future events from along highway 66 south of Morgan. My colleagues at the University of Utah have done this for a couple of events, but it would be great if we could find a way to do it regularly during events. Combined with high-resolution modeling, we could tease out some of these oddities and potentially better predict some of their more fine-scale aspects.