NIDIS Intermountain West
Drought Early Warning System
February 12, 2019

Precipitation


The images above use daily precipitation statistics from NWS COOP, CoCoRaHS, and CoAgMet stations. From top to bottom, and left to right: most recent 7-days of accumulated precipitation in inches; current month-to-date accumulated precipitation in inches; last month's precipitation as a percent of average; water-year-to-date precipitation as a percent of average.

Standardized Precipitation Index


Standardized Precipitation Index standardizes precipitation accumulations for a specified time period into percentile rankings. -1.0 to -1.5 is equivalent to a D1 to D2. -1.5 to -2.0 is equivalent to a D2 to D3. -2.0 and worse is equivalent to a D3 to D4. 30- and 60-day SPIs focus on short-term conditions while 6- and 9-month SPIs focus on long-term conditions. SPI data provided by High Plains Regional Climate Center.

Snotel and Snowpack

The above image shows SNOTEL snowpack percentiles for each SNOTEL site in the Intermountain West. The images below show accumulated snow water equivalent in inches (green) compared to average (blue) and last year (red) for several different sub-basins across the UCRB (and were created by the Colorado Basin River Forecast Center).

Streamflow





The top left image shows 7-day averaged streamflows as a percentile ranking across the UCRB. The top right image shows 7-day averaged discharge over time at three key sites around the UCRB: The Colorado River at the CO-UT state line; the Green River at Green River, UT; and the San Juan River near Bluff, UT. All streamflow data provided by United States Geological Survey.

Surface Water

The top left image shows VIC modeled soil moisture as a percentile ranking. The top right image shows satellite-derived vegetation from the VegDRI product (which updates on Mondays).

The graphs shown below are plots of reservoir volumes over the past full year and current year to date (black). The dashed line at the top of each graphic indicates the reservoir's capacity, and the background color-coded shading provides context for the range of reservoir levels observed over the past 30 years. The data are obtained from the Bureau of Reclamation. Some of the reservoir percentiles don't line up at the new year due to differences in reservoir levels at the beginning of 1985 and the end of 2014.  Dead storage has been subtracted. Note: Lake Granby data are obtained from the Colorado Division of Water Resources, and only goes back to the year 2000.


Evaporative Demand


The above images are available courtesy of NOAA’s Evaporative Demand Drought Index (EDDI). Drought classification listed is a function of the depth of reference evapotranspiration accumulated over a given period of record with respect to a climatology of 1981-2010. The drought categories displayed are in line with the US Drought Monitor's Percentile Ranking Scheme. Data used to generate these maps come from the North American Land Data Assimilation System Phase-2 (NLDAS-2) project, which assimilates observations of temperature, wind speed, radiation, and vapor pressure deficit. The date indicates the last day of the period of record, and the week number indicates the window size for the period of record.

Temperature

All images show temperature departures from average over different time periods (last 7 days on top left; month-to-date on top right; last full month on bottom). Temperature departure maps provided by HPRCC ACIS.

Condition Monitoring and Impacts

Map of current condition monitoring reports submitted to CoCoRaHS in the last week overlaid on the current U.S. Drought Monitor depiction. Specific impacts reports from local experts listed below.

Box Elder County, UT, FSA

Have had some moisture, but most of the months since October have still been below average. While snowpack in the Bear River drainage just went over 100% with the most recent storms, the west part of the county has still been a little below average for snowfall and precip. In Tooele County, they've gotten a lot of snow south of Great Salt Lake, but the west part of the county is about like Box Elder. They are still far behind from a dry spring and summer last year.

Central UT, FSA

There has been quite a bit of activity recently, but with moisture more confined to the mountains than the desert valleys. Things are looking good right now, but still waiting to see what happens in the spring.

Gunnison, CO, BLM

West facing terrain in the region have been hammered by high winds lately out of the northwest. It has been blowing out the snow in some areas, which could possibly mean less available snowpack (not being measured by SNOTEL) for melting in the spring.

Pueblo, CO, DWR

Area is doing very well, with the nearby Sangre de Cristos looking really good. Storms have moved northward lately, so it has dried up a bit closer to Trinidad. Soil moisture is holding up in the lower elevations though, thanks to the passage of consistent smaller storms.

Outlook


The top two images show Climate Prediction Center's Precipitation and Temperature outlooks for 8 - 14 days. The middle image shows the Weather Prediction Center's Quantitative Precipitation Forecast accumulation for seven days. The bottom left image shows the 3-month precipitation outlook from Climate Prediction Center, and the bottom right image shows the Climate Prediction Center's most recent release of the U.S. Seasonal Drought Outlook.
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Summary and Recommendations


Above is the most recent release of the U.S. Drought Monitor map for the UCRB region. Below shows the proposed changes for this week, with supporting text.

Summary: February 12, 2019

Last week was a very climatologically typical winter week for the Intermountain West - low elevations experienced windy days with a couple of small accumulating events, while the high elevations throughout the Upper Colorado River Basin received between half an inch to over 2 inches of moisture. For most of the IMW, temperatures were a bit cooler than average, with much colder than average temperatures in parts of Wyoming.

Since the beginning of the calendar year, snowpack has rebounded in many of the areas of concern. Mountain ranges in southern CO and western WY that had been struggling at the beginning of the winter season have seen a bump. Now, most of the basins in the IMW show near to above normal snowpack, which is a strong indicator of heading toward a better runoff season this spring.

Short-term standardized precipitation index (SPIs) show that developing dryness throughout New Mexico may be a concern and should be monitored closely. A widespread wet signal shows up throughout Utah, though there are still some low lying areas that are drier.  And given the water supply concerns at the beginning of the cold season, they are not out of the woods yet, in terms of drought.

The outlook shows a continued active and wet pattern for much of the IMW. High elevations are expected to receive an addition half to 3 inches of precipitation over the next 7 days. And the 8-14 day outlook indicates an increased likelihood of wetter than average conditions to continue, along with colder than average temperatures. The area that may be missing out on all this excitement over the next week will be southeast NM.

Recommendations:  

UCRB: Some improvements are recommended in northern UT and western CO. Most improvements were limited to areas that received a surplus (above and beyond their average) of half an inch of moisture since the beginning of the month. In these regions of improvement, SNOTEL snowpack sites are mostly above the 50th percentile, water year precipitation is near to above average, and SPIs on all time scales show improvements. In southwest CO, there are no more SPIs below -2 on the 12-month timescale.

We will continue to be conservative with improvements over the region as we wait to see how the snowpack will translate into actual water supply. Reports of recent high wind events, and very dry soils and low streamflows at the beginning of the cold season, are all going to play a role in determining how much of a recovery the region is experiencing. If the time for major improvements comes, it will likely be during the critical snowmelt/runoff season.

Eastern Colorado:  Status quo is recommended for eastern CO this week. Much of the region has received little to no precipitation since the beginning of the month. This is a time of year when a larger number of dry days (or very small accumulation days) is common. Some consistent small accumulating events have helped prevent total drying of the soils. Colder temperatures over the next couple of weeks will also help to minimize impacts of dry spells.