Some moisture midweek through the weekend
Sunday, August 20, 2017
A wave traveling over the top of a ridge of high pressure in the Gulf of Alaska has split, with the northern part of the split moving across Montana and the Dakotas tomorrow. The southern end has taken up position off the California coast, and the southwesterly flow ahead of that area of low pressure will encourage northward transport of moisture over the Steamboat Springs area around midweek and heading into next weekend.
There may be some sprinkles this afternoon, though any storms are likely to produce far more wind than rain as the lower atmosphere is quite dry and any precipitation will largely evaporate before reaching the ground.
For Monday, eclipse day, models have generally trended towards a more cloud-free solution for northern Colorado and southern Wyoming. The wave to our north will drag a couple of weak cool fronts through northern Wyoming tonight and early tomorrow. There may be some clouds ahead of and along the fronts, though current forecasts have the fronts east of Casper, Wyoming by noon on Monday. Therefore, skies will be improving through the late morning, hopefully in time for an unobstructed view of the 2017 solar spectacle.
Areas to our south may not be quite as fortunate, though models have trended drier with their noon forecast as well. There will be a chance of some storms across all of Colorado by the afternoon or early evening, most numerous to our south.
After a dry Tuesday, pieces of energy are forecast to eject northeastward from the California low, reaching our area around midweek even as a brief ridge of high pressure builds over the Rockies. There is uncertainty with respect to the interaction between the low to our west and the ridge of high pressure over our area, with models trending weaker with the surges of moisture and energy. The end result is an uptick in chances for storms starting around Wednesday and lasting into the first half of the weekend, though the threat of more than brief heavy rain currently looks small.
By around Thursday, a strong storm crosses the southern British Columbia coast and travels along the U.S. - Canadian border over the weekend. This will sweep the ridge of high pressure and the California low eastward, with the unsettled weather ending by mid-weekend and being replaced by Colorado’s quintessential late summer weather with warm, dry days and cool nights.