November 2017 has felt more like October. I have been riding and hiking in shorts on many afternoons. Of course all climate sites in the region are warm and dry for the month. As of November 26 the warmth is impressive,ranging from 9.1 degrees above average at Aspen to +4.4 at the Durango airport. Dry conditions are widespread across the SW region for the last 30 days (1st attached). For November through the 26th, deficits run from -1.09 inches at Durango to -0.34 inch at Craig. You have to go up to central Wyoming (Riverton and Yellowstone) to begin the find climate sites that have above average monthly precipitation.
The near-record warmth will be modified tonight, Monday night, as a cold front sweeps over the region. The southern and central mountains will be favored with a forecasted 2-6 inches of snow. The remainder of November looks dry with temperatures down 10 to 15 degrees cooler than Monday’s highs but still remaining above normal.
A significant change towards more winter-like conditions is currently timed for early next week. This storm is currently forecast to have a strong cold core and 150kt jet with significant moisture. If this storm does turn out to be that strong, it could be the start of the Colorado ski season.
Beyond 10 days we look to the state of the Pacific for clues to storm track and intensity. The northern Pacific basin, as measured by the Pacific Decadal Oscillation, has lost the record heat that has been in place since 2014. In the equatorial eastern Pacific, the Nino 3.4 region has been near -1.0C for the last few weeks (2nd attached). La Nina conditions are present and are expected to continue through the winter (3rd attached).
La Nina tends to produce a storm track across the northern tier of states and you can see that trend in the December and Dec-Jan-Feb outlooks (4th attached). Our climate record shows a snowy January often occurs during La Nina winters. Though the second La Nina in a row, like this winter, often is drier. Spring seasons after La Nina tend to be drier than normal.
Beyond the winter outlook the confidence decreases to near zero. Since 1950 we have had two La Nina winters in a row occur six times. The third winter is nearly evenly split, La Nina 3 times, El Nino twice, and ENSO Neutral once.
So the 12 month precipitation outlook (5th attached) beyond this winter show no skill, as the entire nation is in the ‘EC’ or equal chances category. The 12 month temperature outlook shows its typical strong tendency towards climate change with above normal temperatures for much of the nation except across the northern tier (assumed storm track) this winter.
So today may be the last really mild day of fall. Get out and enjoy!