Issue Date: Monday, June 29th, 2020
Issue Time: 9:35AM MDT

Summary:

It was a hot one yesterday! High temperatures reach 100F over the plains, 90Fs over the lower elevations, and the mountain valleys reached the 80Fs. With the majority of the remaining moisture above the boundary layer, rain rates were not very efficient and storms produced more wind than rainfall. Afternoon storms over western Colorado (northwest corner, Northern/Central Mountains) generally produced only traceable amounts/cloud cover with isolated totals up to 0.10 inches near the Continental Divide. Surface gusts between 45 and 60 mph were recorded in the area on Sunday. A new fire was reported on Sunday around 1:15PM – Goose Creek Fire. The fire is located south of Lake Humphreys (Mineral County) and is burning in steep rugged terrain. It has currently burned 115 acres.

Storms over the Front Range had slightly higher moisture content, so isolated rainfall totals were between 0.10 and 0.25 inches for the stronger storms. The highest rainfall was recorded over Sedgwick and Phillips Counties where just under 0.50 inches fell; however, these storms also produced damaging 60 to 70 mph wind gusts. As anticipated, flooding was not reported on Sunday

For precipitation estimates in your neighborhood over the last 24 to 72-hours, scroll down to the State Precipitation Map below.

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Issue Date: Sunday, June 28th, 2020
Issue Time: 9:30AM MDT

Summary

Shower and thunderstorms activity subsided sharply after Friday’s active day, as a disturbance moved east out of Colorado. However, some residual moisture and favorable dynamics support isolated to widely scattered activity mainly across the Palmer Ridge, Northeast Plains and Southeast Plains. Due to large dewpoint depressions (dry sub-cloud layer), it was once again difficult to estimate the highest rainfall. The highest rainfall amounts came from Yuma, Kit Carson and Cheyenne counties. This morning’s AHPS analysis suggested more than 1.5 inches of rain fell in an isolated stretch between Kirk and Idalia in Yuma county. On the one hand, this seems to be supported by an official report of 14 inches of floodwater in the vicinity of Idalia. On the other hand, of the three rain gages in the area of this rainfall, two from the CSU CoAgMet network and one from the RWIS network (all available through the University of Utah MesoWest data archive), the highest amount recorded at the three was less than 0.5 inches. This is supported by our official MetStormLive product shown below. The current thinking is that there was likely a very isolated region that measured a quick 0.5 to 1.0 inch of rain in less than 15 minutes, which resulted in a localized area of flooding where drainage was poor. Further substantiating this idea is the fact that there was almost no response in the nearby streamflow gauges on the North Fork and South Fork of the Republican River and a few nearby irrigation ditches (see the updated Colorado Department of Water Resources for a useful summary of near real-time streamflow data).

Elsewhere, isolated showers and thunderstorms produced generally less than 0.25 inches of rainfall leading to a warm and pleasant summer day.

For precipitation estimates in your neighborhood over the last 24 to 72-hours, scroll down to the State Precipitation Map below.

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Issue Date: Saturday, June 27th, 2020
Issue Time: 10AM MDT

Summary:

Boy did it rain yesterday! The 10- to 30-minute totals from storms were quite impressive as low-level moisture returned behind a cold front and paired with shortwaves moving through the flow at peak heating. Although storms were moving at a moderate pace it did not keep them from dumping buckets of rain. That was to be expected with dew points in the 50Fs over the adjacent eastern plains. Enhance convergence along the Palmer Ridge helped enhance rain rates and produce a brief funnel cloud (spotter network). I don’t love the QPE below as I think it underestimates some of the localized totals yesterday, so I’m going to focus on totals produced by rainfall gages.

First, over the Denver Metro area, the Lakewood area had a couple rounds of rainfall. The highest ALERT gage recorded 1.69 inches (Upper Sloan Detention Pond) for the 24-hour period. Of the 1.69 inches, 1.20 inches fell in a span of 10 minutes – that translate to between a 100- and 200-year rainfall at the 10-minute duration! The Willow Creek gage just south of Castle Rock was also impressive, which was the same storm that later produced a Tornado Warning near the Springs. In a 30-minute span, there was 1.48 inches of rainfall, which is about a 1 in 25-year event. NWS Boulder issued a handful of Flood Advisories for the storms and one Flash Flood Warning.

Further south, over the USAF Academy, a gage recorded about the same for the same storm, 1.57 inches (1.42 inches in less than an hour). From 4:10 to 4:30PM, 0.75 inches of rain were recorded, and a Flash Flood Warning was issued at 4:35PM. Along with heavy rainfall, the storm produced golf ball sized hail (1.75 inches) and stalled cars on Voyager Parkway due to high water. As storms rolled east, the produced strong winds (55 mph), which caused damage in Yuma and Kit Carson Counties. Storms that moved into Logan County produced not only 50-mph winds but also baseball sized hail that knocked out car windows (2.75 inch)! All storms over eastern Colorado produced spikes in small streams, but no gulch or small streams reported flooding as of this morning.

Back to the west, gusty outflow winds were the main hazard as the low-levels were quite dry. A 63-mph gust was recorded in Mesa County, and this same storm produced ½ inch hail in Grand Junction. Radar estimated another 0.20 inches of rain or so for the area. That puts 48-hour totals around a half inch for the area.

For precipitation estimates over your area in the last 24-hours, scroll down to the State Precipitation Map below.

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Issue Date: Friday, June 26th, 2020
Issue Time: 10:20AM MDT

Summary:

Storm coverage increased yesterday as some mid-level dynamics and moderate mid-level moisture moved into the state. With the majority of the moisture in the mid to upper levels of the atmosphere, there was a large, dry boundary layer (lower level of the atmosphere). This promoted strong outflow winds from storms and some evaporation of rainfall before it reach the surface – those actually go hand in hand. Additionally, storm movement was a bit quicker and pulse-like storms prevented heavy rainfall for lasting more than a few minutes. So once again, QPE from Stage IV, MRMS, and MetStrom looked a little bit different.

It looks like MRMS/Stage IV slightly overestimated totals and MetStrom slightly underestimated totals. This is typically what we’ve seen from these products lately on marginal rainfall days. This was further examined by looking at a WxUnderground station in Genoa, CO where a storm core passed directly overhead. The station recorded 0.51 inches, but and MRMS showed 0.75 inches. Stage IV was slightly lower, but still overestimated. Looking at MetStorm below, it looks like bias corrected 24-hour value was slightly underestimated. Totals from MetStorm were closer to reality over that area without the bias correction (see max 2-hr). There are still plenty of reasons that the bias correction has helped improve MetStorm, so the pros outweigh the cons the majority of the time. QPE is not a perfect science, but this illustrates that the truth is often a blend of the solutions, the dry sub-layer can cause issues in estimations over CO, and the importance of rainfall gages to calibrate the QPE. Please consider joining the CoCoRaHS network if you live in a rural area – https://www.cocorahs.org/application.aspx

Anyway, back to the storms yesterday. There several wind gusts reported over the northern portion of the state (especially west). Gusts from outflow boundaries were recorded between 45 and 65 mph. A strong thunderstorm over Grand Junction produced minor street flooding where QPE was estimated around 0.25 inches. CoCoRaHS in the area of flooding showed between 0.15 and 0.20 inches. Hail in Prowers County reached up to 1.25 inches in diameter. NWS Pueblo issued a Flash Flood Warning for this storm where radar indicated up to 2 inches of rain and MRMS estimated 2.50 inches. QPE was estimated closer to a half inch, which was confirmed by another range gage in the area that recorded 0.26 inches. Flash Flood Warnings were also issued for the Spring Creek and Decker burn area. Rain totals up to a half inch were estimated by MetStorm, but flooding was not reported as of this morning.

For precipitation estimates in your neighborhood over the last 24 to 72-hours, scroll down to the State Precipitation Map below.

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