SPM 09-05-2017: Heat and Haze with Isolated Showers

Issue Date: Tuesday, September 5, 2017
Issue Time: 10:30AM MDT


The most notable weather feature yesterday was the lack of visibility. Ongoing fires in Montana, western South Dakota and Idaho continue to produce massive plumes of smoke. With the High pressure centered just west of Colorado, the smoke particles were advected clockwise around the High and into the state. During the peak of the day, visibility was limited to 3-4 miles around Denver and was less than 2 miles over portions of the eastern plains. West of the divide, visibility in the north was in the 2-3 mile range. A visible satellite image from the GOES-16 from 12PM is below. Other than in the Grand Valley, high temperatures yesterday were reduced by 5-10F across the state. The passage of a cold front over the eastern plains helped thin some of the haze and enrich low-level moisture for afternoon shower over the Palmer Ridge. The front was too shallow to alleviate smoke and temperatures west of the Continental Divide.

Showers yesterday were confined to the southern high terrain and Palmer Ridge. While showers also attempted to form over the Front Range, only trace amounts of rainfall reached the surface. With low moisture, storm totals were not very high. Over Las Animas County, a CoCoRaHS station recorded 0.23 inches of rain. In the San Juan Mountains, a SNOTEL station recorded 0.4 inches. The highest estimates of rainfall by radar were over Elbert County where 0.5 inches were estimated to have fallen along the Palmer Ridge with the passage of the cold front.

Flooding was not reported on Monday. To see where rain fell over the state, scroll down to 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.