SPM 09-16-2020: Smoke Surrounds Mountain Clouds

Issue Date: Wednesday, September 16th, 2020
Issue Time: 09:55AM MDT

Summary:

Some clouds and weak showers developed over the mountains again yesterday with diurnal heating, but some clouds were already present over the San Juan Mountains by sunrise, indicating some increased mid-level moisture. These clouds eventually produced virga and a few sprinkles for some locations of the San Juan and Southeast Mountains. CoCoRaHS observers reported up to 0.07 inches of rain accumulation near Pagosa Springs, with only traces of precipitation further west along the southern San Juan Mountains and along the northern & eastern edges of the San Luis Valley. A couple automated weather stations from MesoWest reported 0.01 inches of rain along the southern San Juan Mountains. Overall, rain was very limited yesterday as it was dry for the majority of the state.

One interesting observation from yesterday is the “donut hole” in the smoke over Colorado, with the southwestern part of the state generally staying smoke-free. This is very evident in the true-color satellite image last evening (see image below). Interestingly, within this hole in the smoke coverage was the majority of the cloud cover and instability, as shown by overlaid convective available potential energy (CAPE) contours (purple lines in image below). With small differences in moisture across the state yesterday, the additional sunshine and diurnal heating over the southwestern mountains appears to have allowed more clouds and convective showers to develop. This shows the impact that smoke can have on keeping conditions dry by suppressing precipitation, especially in the absence of more large-scale lift when relying on convection is your only option for precipitation.

Ongoing Colorado wildfires update (as of 9:45AM from InciWeb):
Middle Fork in the Park Range: 4,795 acres; 0% contained
Cameron Peak in the Medicine Bow Mountains: 102,596 acres; 8% contained (increased containment)
Williams Fork in the Arapaho National Forest: 12,157 acres; 12% contained (increased containment)

Not much to see on our State Precipitation Map below as less than 0.25 inches of rain have fallen over the last few days.

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 24-hour, 48-hour and 72-hour total precipitation contain bias corrections that are not disaggregated into the hourly estimates, so there will likely be some differences. The accumulation ending time is 7AM of the date shown in the bottom right corner. Also shown optionally are vulnerable fire burn areas (post 2012), which are updated throughout the season to include new, vulnerable burn areas. The home button in the top left corner resets the map to the original zoom.