SPM 08-23-2017: Strong Cap Produces Garden Variety Storms over the Higher Terrains

Issue Date: Wednesday, August 23, 2017
Issue Time: 10:55AM MDT

Summary:

The morning began with quite a bit of cloudiness over the state. This was expected to limit convection over the far eastern plains, which it did, but the cap was strong enough that storms that drifted into the immediate eastern, adjacent plains quickly dissipated. Only weak showers occurred over the eastern mountains. Over the western portion of the state, showers were more widespread in nature as they drifted from the higher terrain into the valleys with the support of the upper-level disturbance. Precipitable Water (PW) values were around 0.8 inches both east and west of the Continental Divide, which over the past two days had helped dropped impressive 1-hour rain rates (up to 1.5 inches). However, lower temperatures and increased cloud cover limited atmospheric instability and capped strong convection throughout the state. The weaker than expected lift from the shortwave was not able to break through this cap and tap into the higher dew points for heavy, local precipitation. Instead, garden variety showers occurred yesterday.

Over the San Juan Mountains, a CoCoRaHS station near Silverton recorded 0.51 inches for the 24-hour period. Most other storms produced between 0.1-0.3 inches with a few reports just under 1 inch in storm cores. A condensation funnel was even reported in Rio Blanco County. East of the Continental Divide, there were a handful of stations that recorded around 0.35 inches over the Front Range and Southeast Mountains. The radar estimated 1-hour rain rates were 0.5 inches. The highest 24-hour rainfall total was estimated just over 1 inch in Park County. There were no flooding reports yesterday as of this morning.

To see how much rain fell in your area, scroll down 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.