SPM 09-15-2017: Widespread Showers as the West Coast Trough Moved Through Colorado

Issue Date: Friday, September 15, 2017
Issue Time: 10:20AM MDT


Much more active weather pattern yesterday as the ridge moved east and the upper-level trough from the west coast made its way into the state. The low tracked across southern Utah in the morning and the first wave of showers and thunderstorms reached the SW corner of the state by mid-afternoon. The system then tracked NE across the NW corner of the state and initiated widespread showers and thunderstorms through the evening. Showers decreased from SW to NE with the last remaining shower over the Northeast Plains ending just after midnight.

The trough weakened quiet rapidly as it moved through the state. With instability also decreasing after sundown and the negligible presence of low-level moisture, severe thunderstorm dynamics lacked. Faster wind speeds aloft also helped limit heavy rainfall over one area. None the less, the system brought a few areas of widespread rain.

Several SNOTEL stations had over 0.75 inches of rain for the 24-hour period. Over the San Juan Mountains near Telluride, two SNOTEL stations reported 0.9 inches with CoCoRaHS stations in the same range. Radar rainfall estimates were as high as 1 inch. Only minor increases to river discharges were recorded at nearby gages. A CoCoRaHS site in Delta County recorded 0.97 inches. Radar rainfall estimates were highest in this area estimating 1.5 inches of rain. As expected, these thunderstorms produced very gusty winds. An automated station over Rio Blanco County recorded a gust of 67 mph. Over the Northeast Plains, storms did not produce very much precipitation due to strong steering winds and dew points in the 40s. One exception was a severely warned cell over Southern Yuma County where dew points made it into the low 50s. Radar total rainfall estimates were 1.5 inches with 1 inch hail reported at 6PM.

There was no flooding reported Thursday. For rainfall estimates in your neighborhood, take a peek at the State Precipitation Map below.

Click Here For Map Overview

The map below shows radar-estimated, rainfall gage-adjusted Quantitative Precipitation Estimates (QPE) across Colorado. The map is updated daily during the operational season (May 1 – Sep 30) by 11AM. The following six layers are currently available: 24-hour, 48-hour and 72-hour total precipitation, as well as maximum 1-hour, 2-hour and 6-hour precipitation over the past 24 hour period (to estimate where flash flooding may have occurred). The accumulation ending time is 6AM of the date shown in the bottom right corner. Also shown optionally are fire burn areas since 2012. The home button in the top left corner resets the map to the original zoom.

Note: We have identified a possible underestimation in QPE over the southwest part of the state. We are working to on this issue, and will provide an update as soon as possible.