Cooler Weather for the West

Get ready for winter! A strong long wave trough is about to impact the western states, primarily causing winter havoc in Montana, Wyoming, Colorado, and the Dakotas. It looks like the first real snow of the year is on tap for the higher elevations, including even the Black Hills of South Dakota (which really aren't that high). Right now forecasts range from 6-12 inches in north central Wyoming and 2-4 inches in the Black Hills.

This long wave trough has been forecasted by the models for quite a while now. The GFS, European, and CMC all had the trough digging into the western states starting tomorrow. However, there was disagreement on the placement 3-5 days ago. The European dug the trough into southern California and Arizona, then pulling it out quickly through the Dakotas. The GFS dug the trough into the Colorado/New Mexico area and cut it off...bringing it slowly up through the Midwest. The CMC was a mix of the two, closer to the Euro.

Now the GFS has switched to the European result, digging the trough into southern California and then pulling it up quickly through the Dakotas...and then traversing west through the Midwest. This seems like a reasonable solution, and I expect it will pan out. After e-mailing with Doug, we have hypothesized that the GFS was underestimating the strength of the sub-tropical ridge int he eastern US. Thus, the GFS wanted to push the trough in a bit further to the east. When the model finally figured out the ridge was stronger, it moved towards the European solution.

But what does this all mean? Get ready for cold weather and possible snow in the higher elevations of Wyoming (and even possibly in the valleys in this area as well), Montana, Colorado, and South Dakota. The original threat of snow from the GFS in Denver is gone now with the correct European solution panning out. However, don't worry...the Denver snow will come later this year. :)

PS: The GFS/NOGAPS/Euro are all showing a tropical system developing in the western Caribbean over the next week. The steering currents are interesting, and might even pull the system to the EAST rather than the west. This has happened in the past, so it is not unprecedented. All three models forecast a rather strong storm.