To summarize, Sunday-Tuesday sees a gradual shift from stable to unstable weather. Then, a storm Wednesday and another around Friday drop substantial snow over the interior West.
Compared to the previous week, we’re under somewhat zonal flow during the weekend. Zonal flow means air in the jet stream moves along latitude lines or east-west. The difference between zonal and north-south flow is that zonal flow tends to propagate systems more quickly. However, these systems tend to have less “spin” to them. Nevertheless, zonal flow doesn’t necessarily mean fewer storms.
In fact, I think the next few days are looking like intermittent low-impact storm systems before a few harder-hitting late-week storms hit the area.
Sunday through Tuesday sees gradually decreasing low-level stability and increasing mid-level moisture.
At the same time, an upper-level trough moves in slowly until it’s blocked outside of the jet stream just off-shore of Washington state. It seems like this setup works well for pivoting shortwaves around the upper-level trough and into the interior west. Our area’s mountains may get some weak precipitation from passing unstable air between now and Wednesday. The chance of experiencing these weak systems increases every day as moisture infiltrates the mid-levels. However, their timing is not easily predictable at this point.
Two Late-Week Systems
Otherwise, we’re looking at two stronger storms that arrive here next week. The first hits sometime Wednesday. It is a shortwave that loops around the blocked upper-level trough I mentioned earlier. Another system sometime Friday may be stronger. This system is a product of the strengthened upper-level trough itself, as it’s finally pulled into the jet stream and propagated across the US. Ultimately, the impact of each of these systems will depend on their available moisture and instability.
As far as precipitation goes, I’m staying away from the late-week systems. Look out for that forecast later this week. Otherwise, NAEFS ensembles are confident that Sunday will be clear of new snow, but Monday and Tuesday each have a chance for 1-3 inches of snowfall per day. The confidence in the occurrence of this somewhat random precipitation increases closer to Wednesday. On the other hand, snowfall totals are still quite uncertain.
Wind and Temperature
Next, expect winds to increase over the next few days gradually. Short-term I don’t think this means anything more than a bit of a breeze for resort skiers, Monday and Tuesday for example, even at the summits. Wednesday-Friday, however, may be pretty windy. Just a heads up.
Finally, we can expect that temperatures this week will decrease somewhere between 7 and 9 degrees C (or 12-16 degrees F) for every kilometer above the surface because low-levels are conditionally unstable. You might think resort temperatures would then be frigid. However, early-week daytime temperatures in the valley will be increasingly mild (the 40s and 50s), so resort temperatures may be somewhat average in the 20s and 30s.
That’s all for now. Enjoy the unsettled weather if you can early this week!