Monday, July 10, 2017
Pacific energy moving eastward from a complex of storms in the Gulf of Alaska has flattened the dominant western U.S. ridge and nudged it eastward, allowing the first significant surge of the Southwestern U.S. Monsoon to reach the Steamboat Springs area this season.
The tropical storm system discussed in the last forecast did indeed turn into hurricane Eugene and contributed to the moistening of the atmosphere over the southwestern U.S. As a result, there is a good chance of wetting rains over the Steamboat Springs area later this afternoon and early this evening. Short range models show another batch of showers that may reach far enough northward to produce more rain around midnight.
As weak Pacific energy moves eastward to our north, drier air moves in behind the wave, and our weather will depend on the outcome of the battle between this dry air to our west and north and the monsoonal moisture to our south and southwest. Current models have a chance of showers for Tuesday and Wednesday as the boundary between the dry and moist air is close to northern Colorado.
By Thursday, the western U.S. ridge rebuilds, bringing drier air across the region under hot temperatures. The strong surface heating will cook any remaining low-level moisture to produce a chance of afternoon storm for the remainder of the work week and into the weekend.
Significant differences between the models arise for the second half of the weekend, with the American GFS further rebuilding the western U.S. ridge and further warming temperatures as cool Canadian air moves southward across the Eastern U.S. The European ECMWF, on the other hand, slides this cool Canadian air westward and tries to phase it with some incoming Pacific energy, flattening the western U.S. ridge and moderating temperatures for the second half of the weekend and early next week.