Monday, October 16, 2017
High pressure is in control of the weather for almost the entire United States, and this will bring more warm and dry days with cool nights for the Steamboat Springs area through most of the work week. A quick moving storm along the northern U.S. border may knock temperatures back a bit for Wednesday, but the dry weather will persist until later Thursday when a stronger Gulf of Alaska storm crosses the West Coast and affects our region through the early part of the weekend.
As this moves eastward, southwest winds first carry some moisture northward, bringing some high and mid-level clouds to the area later Thursday and possibly some light showers by Thursday night. As the storm moves across Idaho on Friday, southwest winds will increase over our area and become breezy to windy, with showers becoming likely by later Friday ahead of a cold front currently timed for Friday night.
Showers will stay as rain in the Yampa Valley ahead of the front before changing over to snow by overnight Friday. Like the last Saturday storm, this one will also be quick moving, bringing a cool start to the weekend with showers ending early in the day.
High pressure builds in behind the storm for a nice Sunday, though there is some uncertainty for early next week regarding additional Pacific energy that will carry some more moisture and winds inland across the Pacific Northwest. This energy may sag far enough south to bring some clouds and slightly cooler temperatures for Monday and Tuesday, or stay north of the area for less clouds and warmer temperatures.
It appears La-Nina is back in the news, as the National Weather Service issued an advisory last Thursday indicating a 55%- 65% chance of a La-Nina winter. El-Nino is a warming of the ocean waters in the southern Pacific, while its counterpart, La Nina, is a cooling of those same waters, and its appearance can affect global weather patterns. Closer to home, El-Nino is associated with a strong, relatively stationary ridge of high pressure in the eastern Pacific, while La-Nina has a much suppressed or even absent ridge.
While some weather forecasters insist that all of Colorado is affected by El-Nino or La-Nina, the fact is that northern Colorado is not well correlated with either. During El-Nino years, the location and amplitude of the ridge of high pressure in the Pacific is critical, and the Steamboat Ski Area may be in favorable northwest flow if the ridge is far enough west, or benign weather if the ridge is further east and closer to our area.
However, the suppression or absence of the ridge during La-Nina years means that storms moving across the Pacific are not influenced by a relatively stationary weather pattern. This tends to keep the storms moving, and long stretches of either quiet or stormy weather are less likely. In my view, an accurate seasonal forecast for northern Colorado based upon the slightly-better-than-chance probability of a La-Nina event, combined with the absence of strong correlations in our area to that event, is impossible.