Summary: May 26, 2020
The majority of the Intermountain West (IMW) was dry for the week, with warmer than average conditions across much of the region. A couple of widespread thunderstorms did occur across the esatern plains of Colorado. For some areas, the benefit was limited and the moisture quickly dried out.
In the Upper Colorado River Basin, snowpack is melting quickly. In the southern portions, most of the snowpack is gone, and it's possible that streams and rivers have already seen their seasonal peak flow. Northern high elevations are still holding onto some snow. For lower elevations, hot, dry, and windy conditions are dominant and fire danger has been high this week.
Extremely dry conditions are evident in precipitation deficits, high temperatures, high evaporative demand, vegetation stress, and dry soil moisture. The outlook shows that more relief may come for the eastern plains, but more warm and dry conditions are expected over the UCRB. Reservoirs are showing modest increases in levels right now, but for the southern reservoirs, it's expected they will receive much less than average.
Northeast CO: Some trimming of D0, D1, and D2 is recommended, staying north of Lincoln and Kit Carson counties. Month-to-date AHPS shows these areas have had at least a 1" surplus of moisture. Areas that received precipitation last week but are still below average for the month should not show improvement.
Central and Western CO: Beginning west of Washington and Lincoln Counties, improvement shifts to deterioration. An expansion of D0 and D1 are recommended in central Colorado. These line up with various SPI timescales from 30-120 days. The D1 should avoid the highest elevations that still have a bit of snowpack and the Arkansas headwaters (in Lake County). Also the headwaters of the Colorado should remain D-nothing.
In southwest CO, the expansion of D3 is recommended to line up with changes across the border in New Mexico. It is also recommended to cover more of the higher elevations of the San Juans and the headwaters of the Upper Rio Grande, supported by D3-D4 SPIs on several timescales and poor conditions in soil moisture, VegDRI, and snowpack.
Utah: Northward expansion of D1 and D2 through the central part of the state is recommended. SPIs are mostly below -1 from 30-days to 120-days. AHPS shows 1-3 inch deficits for the month of May.
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