Summary

Northwest flow will continue to bring snow to the mountains along and north of I-70 with the heaviest snow falling Friday afternoon through Saturday morning (6+ inches). Then we'll dry out and warm up through next week, with rain and snow showers returning for Memorial Day Weekend.

Details

Ah, northwest flow. It giveth, and it maketh me feel like I'm not that good at my job. We've been talking for days about the mountains along and north of I-70 seeing afternoon and evening snow showers as moisture moves over the state in northwest flow. Yesterday I said that each afternoon could bring 1-3 inches of snow to favored areas. Well, last night the northwest flow keyed in on the Loveland Pass area and dropped about 0.5 inches of snow-water equivalent, which translated into 7 inches of overnight snow for Abasin. This is a snow ratio of 14:1, similar to what you'd see in mid winter, not mid May. A few of the models forecasted about 0.3 inches of snow-water equivalent last night, but that would usually translate to 3-4 inches at this time of the year, not 7 inches.

The blue and green dots show that the highest accumulations fell near Loveland Pass on Wednesday night.

Last weekend, the European model forecasted that northwest flow would continue all of this week and that snow would fall over the northern mountains. I actually wrote a draft post where I said that Thursday (today) could be a powder day, but then deleted that because it's impossible to predict the times of heavier snow in northwest flow one week out, and because I didn't think we'd have snow ratios high enough to turn 0.2-0.4 inches of liquid equivalent precipitation into signifcant snow. Funny how that worked out, eh?

This northwest flow will continue through Saturday. Another wave of moisture and energy should arrive Friday afternoon and last through Saturday morning, and some models are highlighting another 0.5 inches of SWE along the divide mountains, along and north of I-70. Using history as a guide, this could translate into 6 inches of snow or more by Saturday mid morning.

Precipitation forecast from Thursday through Saturday from the high resolution NAM 4km model. Notice the blue dots along the northern divide, showing the likely location of the heaviest precipitation. Source: WeatherBell.com

We'll finally lose the northwest flow on Sunday, and most of next week should be dry over the mountains with thunderstorms on the eastern plains along and north of I-70.

A slow-moving storm will hang out over California and Nevada next week, and it will finally move east over Colorado during the Memorial Day Weekend. This means that rain (and high elevation snow showers) should fall over the holiday weekend, and while it won't be a washout, you'll likely get rained or snowed on at some point if you're in the mountains all weekend.

JOEL GRATZ