SPM 09-23-2017: Increasing Rainfall as the Trough Moves West

Issue Date: Saturday, September 23, 2017
Issue Time: 11AM MDT


The upper level tough that has been building to our west finally started to move into the state yesterday. West of the Continental Divide, showers began early yesterday morning over the San Juan Mountains with embedded shortwaves moving across the region. By early afternoon, shower coverage increased across the Western Slope and higher terrains. Limited atmospheric moisture over these areas helped keep rainfall totals under flood threat criteria. Over the eastern plains, a surface low pressure helped pull in higher moisture on its east side. To the west, dew points remained in the 30s and 40s, which kept accumulating rainfall over the higher terrains. The increased moisture over the far eastern plains paired with upper level energy from the approaching trough, which sparked another round of showers and thunderstorms beginning around 7am this morning. As the cold front continues to drop south and moisten the low levels, the frontal zone will also promote an area of lift for showers to organize on.

Due to the lack of moisture over the majority of the state, gusty outflow winds were reported with many of the stronger thunderstorms that formed yesterday. The highest reported gust was over Rio Blanco County where an automated station captured a gust of 55 mph. These strong winds are often associated with the inverted-V atmospheric soundings. Over western Colorado, several CoCoRaHS stations reported rainfall ranging from about 0.25 inches to 0.4 inches. The highest rainfall reported by a CoCoRaHS station was in Rio Grande County, and it reported 0.61 inches. Radar estimated rainfall was up to 0.5 inches west of the Continental Divide. Over the mountains, east of the Continental Divide, a CoCoRaHS station near Westcliffe recorded 0.41 inches near the Hayden Pass burn scar. Luckily no flooding was reported. Rainfall over southeastern Colorado began after 7am, so those totals will be rolled over into tomorrow’s rainfall totals.

There was no flooding reported on Friday. To see how much rain fell 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.