It was a colder than normal year for trick-or-treaters across most all of the Intermountain West, as an early cold season arctic airmass dug into the region. Weekly temperature anomalies were more than 15 degrees below normal for much of Utah, Wyoming, and Colorado. October temperatures were a sharp contrast from the much warmer than average September. Utah, Wyoming, and Colorado October temperatures were among the top ten coldest on record going back to 1895.
Last week’s deep cold frontal passage did lead to some decent moisture totals east of the Continental Divide, and some more modest moisture west of the Continental Divide. Headwaters of the South Platte and Arkansas Basins recorded 0.50-1.00″ of precipitation. Most of this moisture fell as snow. Snowpack levels for major river basins across Wyoming, northern Utah, and most of Colorado are above normal to start the season. However, southern Utah and southwest Colorado are still behind on snow. Furthermore, it’s still early. Two weeks of dry weather would erase existing snowpack surpluses.
The Intermountain West continues to balance the impacts of short-term dryness against the impacts of a great 2019 snow season. Surface water supplies in stream and reservoirs are still, by and large, healthy. 7-day average streamflows are beginning to lean dry in the Four Corners area. Meanwhile, southest Colorado is reporting precipitation defictis of 5-10″ since the beginning of July. It will likely take more than a couple storms to close these deficits. Impacts from short-term drought include dry soils, stressed vegetation, difficult winter wheat planting conditions, and stunted late season grass growth for ranchers.
Recent cold weather and snow in the high country has at least mitigated fire concerns. The Decker Fire south of Salida, CO is now 100% contained. As the temperatures cool and the snow settles, we say “farewell” to the 2019 growing season (and hopefully fire season as well). We now play the waiting game to see how WY 2020 snowpack will build across the UCRB. The southern portion of the UCRB will be disadvantaged come springtime by the dry soils in place now. The Variable Infiltration Capacity model is indicating bottom 10th percentile soil moisture storage for southern Utah and western Colorado.
The near-term weather outlook shows dry conditions prevailing across most of the Intermountain West. A large high pressure ridge off the West Coast is blocking Western US access to some much needed Pacific moisture. Models are suggesting 0.25-0.50″ of moisture is likely for southern New Mexico this week, and that another cold front or two may clip eastern Wyoming and northern Colorado. Relief is not currently in sight for the drought-stricken Four Corners area.