Looking back at September 2017, the month’s weather was divided on the 14th of the month. The first two weeks were mostly very warm and drier then normal. The final half of the month was generally cooler and wetter than normal. The month as a whole ended warmer than normal at all twelve climate sites. Regional monthly precipitation was mixed with the south generally drier then normal (minima at Durango, -0.67 inches below normal) and the north wetter than normal (maxima at Salt Lake City +0.83 inches).
For the first week of October we are in the storm track with a warmer and dry break on Tuesday and Wednesday. Snow levels are quite low the next few days, around 7000ft north and 9000ft south.
In the latest outlook from the CPC, the October storm track looks to favor the northern tier of states including northern Colorado. This may help the short-term drought conditions over NW Colorado. The southern portion of the state shows less forecast skill. For the Oct-Nov-Dec season there are increased chances of warmer than normal, with little precipitation forecast skill.
For hints about the winter to come, we look to the state of the Pacific. In the equatorial Pacific, the Nino 3.4 region’s temperatures are near normal. The current ENSO forecast is now for either neutral or La Nina conditions expected to develop as we head towards winter. Neutral ENSO winters are wildcard seasons with both very dry and very snowy winters in their climate record. La Nina winters tend to have a stormy and snowy January favoring northern and central Colorado.
For the truly geeky, the PDO is still just a bit warmer then normal, down from the record warmth of the last two years. So any signal from the PDO is muted.
Looking out through the next 12 months, the CPC outlooks show a tilt towards a possible La Nina cold season. La Nina winters tend to produce a storm track across the northern tier of states. Therefore the outlooks show increased chances of wetter than normal across the northern tier of states and drier than normal across the south. Temperature outlooks show less La Nina influence and more of the climate change signal with a warmer than normal tendency dominating all but the northern tier states.
Enjoy the fall colors as they will going away quickly.
All the Best,