NIDIS Intermountain West
Drought Early Warning System
May 21, 2019
Friendly Version of current Drought and Water Assessment
Summary: May 21, 2019
Over the last week much of the Intermountain West Region continued seeing cooler than average temperatures while eastern Colorado experienced temperatures that were slightly warmer than average. However, month-to-date temperatures are showing cooler than average temperatures across the all of the IMW, including eastern Colorado, with the biggest anomalies being 6 to 10 degrees cooler in eastern Wyoming. Cooler temperatures associated with the current spring snow storm has brought decent snowfall over the past 24 hours to eastern Wyoming and central Colorado. El Paso county in Colorado seeing up to 20.00' of snow.
Looking at the precipitation maps you see that there was a mix of dry conditions in southwestern Wyoming, eastern Colorado, and southeastern Utah, and at least 0.25" through the rest of the region, with the exception of northwestern Utah, southern Arizona and parts of southern New Mexico. Parts of eastern Colorado also saw drier conditions: El Paso County, Pueblo County and northeastern Colorado. However, over the past 24 hours much of the IMW saw decent precipitation/snowfall. The bulk of precipitation was seen through central Colorado where they received over 1.00" and up to 3.00" in areas in central Colorado.
SPIs are still showing dryness on the short term in eastern Colorado and Wyoming. This is the beginning of the wet season in eastern Colorado and Wyoming, so deficits quickly show up on the SPI. Current SPI data does not include precipitation from the current storm and short term SPIs could improve once this storm is taken into account next week. SPIs through the rest of the IMW region are still looking good.
With the cooler temperatures in the mountains, snowmelt slowed down and there was a slight increase in snowpack in most basins throughout the Upper Colorado River Basin. Current snowpack through the UCRB are still at or near record numbers in the southern mountains and median or better to the north. The slowing in melt was seen in the streamflow with decreases in streamflow being observed over the past 2 weeks.
Evaporative demand season is just starting up and with the cooler than normal temperatures, demand is off to a slow start, which is a positive. More on this as the season progresses.
The outlook for the rest of the week looks cooler than normal with the remnants of the current storm adding more precipitation to the beginning of this week. Utah and Wyoming are expected to see decent precipitation throughout the following week and central through eastern Colorado has a good chance of pop up showers and thunderstorms throughout the week. The 8-14 day outlook is showing good chances for below normal temperatures for the UCRB and eastern Colorado and above normal precipitation over most of the UCRB with the greatest probability over northern Utah.
UCRB: We are recommending an improvement of the D0 depiction in southwestern Colorado through Utah. Additional precipitation in southern CO near the Four Corners, coupled with the hydrologic rebound from snowmelt, suggest that more improvements can be made. We are open to any improvements in the area (in-line with NM recommendations) up to and including removing the D0/D1 from southwest CO and southeast UT.
We are recommending status quo in Wyoming. We are leaving the current D0 and D1 categories in Wyoming since precipitation in eastern Wyoming did not fare as well as western Wyoming with the current spring storm. SPIs are in agreement with the current depiction. Improvements might be implemented next week as outlook is showing a good chance of decent precipitation in this area over the next two weeks.
Eastern Colorado: We are recommending a category improvement of the D0 over south central Colorado. SPI data for the last week does not support this as the current spring storm precipitation and temperature data has not been included. However, the current spring storm did bring cooler than average temperatures and decent precipitation into this region over the past 24 hours. Much of south central Colorado saw at least half an inch of new precip with areas such as El Paso county seeing over 2.50" of new precip and 10-20" of new snow.
We are also recommending a category improvement, from D0 to D nada, over Yuma county Colorado. This region experienced about 0.50' of precipitation in the past 24. This region has seen above average precipitation in the past week thanks to the precipitation over the past 24 hours. This is not shown on SPI data as the current storm is not included.
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