SPM 09-18-2017: Severe Thunderstorms over the Eastern Plains with Garden Variety Showers over the Mountains

Issue Date: Monday, September 18, 2017
Issue Time: 10:45AM MDT

Summary:

Showers and thunderstorms kicked off yesterday just after noon over the higher terrains. In the mountains, the moist, upslope flow created garden variety storms during the afternoon hours. Increasing moisture with southwesterly flow aloft paired with upper level dynamics helped support stronger storms over the plains as the storms moved northeast off the mountains. Throughout the day, a stationary front sat just east of the mountains, which created southerly flow at the surface to its east. This not only helped dew points reach the low to mid-50s, but it also created enough shear for a couple severe thunderstorms over the Northeast and Southeast Plains. A Severe Thunderstorm Watch was issued for the Southeast Plains from late afternoon into the evening. Storms to the north exited the state by about 9PM, but storms over the SE corner of the state lingered up until midnight.

Over the mountains, the highest rainfall totals were along the Front Range. A UDFCD gage between Aspen Park and Evergreen recorded 0.59 inches of rain with other gages in the area recording the same. As mentioned, more severe storms formed over the Northeast and Southeast Plains. Large hail and gusty winds were reported with a local storm report of 1.5 inch hail in Las Animas County. A CoCoRaHS station in eastern into Baca County recorded 0.96 inches.

Radar rainfall estimates in the SPM are as high as 4 inches, but likely overestimated. As mentioned, the Pueblo radar is down for maintenance through the end of September. Thus, the radar estimated totals are from nearby radars, which were out of range to make an accurate estimation. This is also a very rural area, so the storms centers did not pass through any gages in Colorado or northern New Mexico. There was a USGS gage in the western Oklahoma panhandle that recorded just over 1 inch of rain. Streamflow also spiked at this gage to over 2000 cfs yesterday afternoon from the storms to the west. So while the true rainfall total may not be known, there was a significant amount rain along the CO/NM border.

There was no flooding reported Sunday as of this morning. For an estimate of rainfall totals in your area, 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.