Sunday, December 6, 2020
Another bluebird day is over the Steamboat Springs area this Sunday noon with temperatures in the mid-thirties, on their way to over ten degrees above our average high of 31 F. More of the same is expected through midweek before the atmosphere undergoes a pattern change which brings wintry weather back to our area by Friday.
A storm currently over the Oregon - Nevada border has formed an eddy cut off from the main jet stream, and is forecast to move to the south-southwest through the day Monday before vacationing for a few days off the coast of the Baja peninsula. Meanwhile, a piece of a strong storm currently near the Aleutian Islands is forecast to move through the Gulf of Alaska and cross the Pacific Northwest coast on Wednesday, followed by the main part of the Aleutian storm on Thursday.
All three of these storms will interact to some degree, bringing an end to our warm and sunny weather which is expected to last through the day Wednesday. Even as the lead part of the Aleutian storm moves across the northern Rockies on Thursday, it will also force the vacationing eddy to to move along the southern U.S. border with Mexico. There was hope in my earlier forecast that some moisture rotating around the eddy would be pulled northward into the northern storm as it approached our area, but it appears now that we will only see some clouds and cooler temperatures on Thursday as that northern storm will be quite weak.
However, there will be a strong interaction between that eddy and the northern storm as the two storms move to our east; in fact the storms are forecast to merge into a single stronger storm that consolidates around Kansas. Interestingly, moisture originally from that eddy is then forecast to rotate counterclockwise around the merged storm and move over our area by Friday ahead of the bulk of the Aleutian storm. Colder temperatures and snowfall of generally light intensity are expected for Friday into Saturday morning as the main storm moves through. It’s probably too early to throw numbers around for forecast snow amounts at this point due to the complicated interaction between all of these storm pieces, but I should have a good idea of snow accumulations by my next regularly scheduled weather narrative on Thursday afternoon.
A transient ridge of high pressure is then forecast to move over the West behind the storm complex after Saturday, though weather forecast models disagree on the amplitude of the ridge and whether we will see light snow for a time on Sunday. Both agree on a dry start to the following work week, but also agree on a currently good-looking storm for our area around midweek. And for what it’s worth, the longer-range forecasts are predicting an active and wintry weather pattern to continue after mid-month.