SPM 06-28-2021: Second Debris Flow in Glenwood Canyon

June 28, 2021 by ·

Issue Date: Monday, June 28, 2021
Issue Time: 9:55 AM MDT

Summary:

Scattered thunderstorms began to form along the Front Range Mountains and Urban Corridor in the early afternoon yesterday, as well as the Northeast Plains. Storms generally moved northeastward and allowed for training cells, especially on the Northeast Plains. By late afternoon-early evening, storm coverage had also filled in in the Northern, Central, and San Juan Mountains. Rainfall rates with these storms were generally low however, resulting in low 24-hour accumulations. For rainfall estimates in your area, check out the State Precipitation Map below.

Even with lower total storm accumulations, after several days of consistent rainfall burn scars were particularly vulnerable to flood conditions. For the second time this weekend, a debris flow from rainfall on the Grizzly Peak burn scar closed I-70 in Glenwood Canyon. Rainfall over the burn area on Sunday was light, less than 0.25 inches, but still enough to produce a debris flow coverage area of 80 feet wide and 5 feet deep, as seen in the pictures tweeted from CDOT.

There was also flooding on the Calwood burn scar in Jamestown yesterday. A flood advisory was issued in the evening, followed by a upgrade to flash flood warning after Doppler radar indicated heavy rain. Law enforcement in Jamestown reported a 3-4 foot surge of debris and water flowing down Geer Canyon.

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.
Filed Under: State Precipitation Map ·

SPM 06-27-2021: Mud Flow on Grizzly Creek Burn Scar

June 27, 2021 by ·

Issue Date: Sunday, June 27, 2021
Issue Time: 9:40 AM MDT

Summary:

While Saturday was less exciting than Friday, there was still moderate precipitation that fell, largely in the high elevations. Early morning showers were already taking place in the Southeast Mountains and spilled over to the Southeast Plains. As the morning progressed, storms also began to form further in the Northern, Central, and Front Range Mountains as well, before spilling over into the Urban Corridor and then Eastern Plains. The Western Slope and Grand Valley were mostly dry, but some isolated showers did produce quick 0.01-0.15 accumulation in some locations.

The high elevation rainfall was both helpful and harmful yesterday. Scattered showers over the Muddy Slide Fire and Sylvan Fire helped keep fire behavior low yesterday and aid in firefighting efforts. However, a flash flood warning was issued for the Grizzly Creek Burn area yesterday after Doppler radar indicated heavy rainfall. A few days of moderate rain over the burn scar in addition to this heavy rain was enough to cause a mud and debris flow in Glenwood Canyon. I-70 was closed for a period of time yesterday, though has since reopened. MetStorm Live grids in the State Precipitation Map show rainfall over the burn scar as just around 0.50-1.00 inches over the last 72-hours, but still enough to saturate soils and cause runoff. CPR’s Ryan Warner and Stina Sieg tweeted information, including a photo of the slide from CDOT, about the I-70 closure yesterday.

For rainfall estimates in your area, check out 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 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.
Filed Under: State Precipitation Map ·

SPM 06-26-2021: Heavy Rain Across State – Flooding Along Urban Corridor

June 26, 2021 by ·

Issue Date: Saturday, June 26, 2021
Issue Time: 9:00 AM MDT

Summary:

As discussed in the Flood Threat Bulletin yesterday, there was plenty of available moisture in the atmosphere on Friday and it materialized as heavy rain across the state. There were lots of heavy rain reports in the Central Mountains, Grand Valley, and Southwest Slope including another 1.75 inches reported in Olathe (who got over 1.5 inches yesterday). Other reports in this region yesterday range between 0.50 – 1.00 inches, all of which will help improve drought conditions in the very dry west.

Along the Northern Mountains, Front Range Mountains, and Urban Corridor flash flood warnings or flood advisories were issued yesterday, especially for small and urban streams after significant rainfall. The Calwood Burn Scar, Cameron Peak Burn Scar, and Hayden Pass Burn Scar we also included in these advisories. While no flooding was reported on the burn scars themselves, there was a report of flooding in Masonville, near Horsetooth Mountain, west of Fort Collins (text below).
Remark: BUCKHORN ROAD SOUTH OF BIG BEAR ROAD CITIZEN REPORTED WATER RUNNING 5 TO 6 INCHES DEEP AND GROWING RAPIDLY.

Further south, over 2 inches fell across South Denver and surrounding Metro Area, including 2.91 inches in Parker. A majority of that rainfall, 1.97 inches, fell in just an hour! The time series plot below shows the breakdown of hourly rainfall at Newlin Gulch in Parker. A rainfall rate of 1.97 inches/hour is nearly a 50-year rainfall event in this area.

Urban streams responded to the heavy rain, and there are social media reports of fast-moving creeks and streams overflowing their banks all over Twitter, including the following from Littleton. Additionally, the Big Dry Creek below C-470 at Highlands Ranch and Sand Creek at Mouth near Commerce City are reporting all-time high flow for this day of year.

Last, but certainly not least, we have our first flood reports from the “Report a Flood” tab! Thank you to Jon Person and Evan Mitchell for making the following flood reports yesterday.

“I haven’t seen a flood like this in the Cherry Creek corridor since 2013. The creek is over its banks and is even flooding part of the Happy Canyon bike trail. No damage to report, but significant sediment will likely be deposited by this event. Here are some videos: https://www.youtube.com/watch?v=uOYmpfcEYSM https://www.youtube.com/watch?v=BRZfRPzFzgw” – Jon Pearson, Cherry Creek near Parker, CO

The creek’s response to the heavy rain can also be seen in the hydrograph below, where Cherry Creek near Parker briefly reached “Action” stage overnight.

“soccer field is slowly filling up and drainage gutters on either end are not able to drain it quickly enough. There are several inches of standing water on the field and the creek that runs through govenor grant park is well out over ita banks and is flowing very quickly. The gutters’ drainage holes maybe clogged with debris and may need to be unblocked, but the creek it drains into is still extremely full, it may just not be able to low enough out to drain it.” – Evan Mitchell, west of Littleton

Please continue to utilize the Report a Flood tool if you seen flooding in your area. For rainfall estimates in your area, check out 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 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.
Filed Under: State Precipitation Map ·

SPM 06-25-2021: Heavy Rain East and West

June 25, 2021 by ·

Issue Date: Friday, June 25, 2021
Issue Time: 10:00 AM MDT

Summary:

Thursday was even cooler across Colorado compared to Wednesday, and especially welcome after the recent heatwave. Thursday was also very active in terms of precipitation across the state. A surge of monsoonal moisture brought precipitation to the Northwest and Southwest Slopes, as well as the Grand Valley, and east of the divide a weak trough allowed for thunderstorm development, some severe, on the Palmer Ridge and Eastern Plains. Widespread 0.25-0.50 inches of rain can be seen in the State Precipitation Map across much of the central portion of the state, with pockets of even heavier rainfall embedded.

In fact, heavy rain and flood reports were made on both the Western Slope and Eastern Plains. 3.50 inches of rain was reported in Burlington (Kit Carson County) via social media after the evening storms. In addition to heavy rain, high winds and large hail were reported with the severe-warned thunderstorms, including an 80-mph wind gust, also in Burlington. On the Palmer Ridge, 60mph winds were reported at Peterson AFB, and 0.88-inch hail in nearby Falcon. Thunderstorm outflow caused an RV to be blown over and reduced visibility to near zero in Sheridan Lake (Kiowa County), according to storm chaser reports.

Total storm magnitudes were less on the Western Slope, but still impressive. Meeker reported 0.66 inches of rain in 6-hours, and Olathe reported 1.60 inches in 3 hours. The 200-year 3-hour precipitation frequency estimate from NOAA Atlas 14 for Olathe is 1.58 inches, so Olathe saw just over a 200-year storm, or an event with 0.5% chance of occurrence in any given year.

A couple flood advisories were issued for the Cameron Peak burn scar in Larimer County, Central Delta and Northeastern Montrose Counties, and Central Rio Blanco and Northwestern Garfield Counties. No flooding was reported on the Cameron Peak burn scar, but flooding was reported near Olathe, including the following two remarks indicating road and field flooding.


The Muddy Slide fire burning in the Northern Mountains benefited from about 0.2 inches of rain, helping to briefly reduce fire behavior, and the Sylvan Fire burning in the Central Mountains also benefited from 0.1-0.5 inches of rain over the fire area.

For rainfall estimates in your area, check out 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 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.
Filed Under: State Precipitation Map ·
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