Issue Date: Sunday, May 10th, 2015
Issue Time: 9:10 AM MDT
Summary:
The late spring storm that barreled across Colorado on Saturday certainly lived up to, if not exceeded, its expectations. Numerous waves of shower and thunderstorm activity moved in a repetitive fashion across Eastern Colorado. The rain fell over saturated soils, quickly leading to flooded fields and eventually roadways. By early evening, Logan and Morgan counties in the Northeast Plains were hit especially hard, with widespread reports of impassable roadways.
There are several interesting things to note about this event. First is that during the entirety of this event, hourly rainfall rates essentially stayed at or below 1 inch per hour. In fact, most of the hourly rain rates were in the 0.4 to 0.7 inch per hour range. Thus, it was the persistence of the rainfall and saturated soils that are equally responsible for the flooding. This shows that high rainfall intensities are not always required to cause very impactful runoff and flooding concerns in Colorado. Second, despite the fact that not everyone likes snow in May, the snowfall acted to tremendously reduce the rate of runoff and has likely saved many rivers and streams from going into much more severe flooding.
Another interesting fact we found this morning relates to consecutive rainy days in Colorado. Despite the fact that consecutive rainy (or snowy!) days in Colorado are rare, there have now been 10 days in a row where Denver has recorded precipitation. Going back to the records from Buckley Air Force Base (in Denver) that date back to 1961, we found only one instance where more consecutive days with precipitation were recorded: 11 back in July of 2011! This makes the past 10 day period as the second highest on record.
Now back to yesterday’s weather. Total 24-hour rainfall amounts over two inches were observed across many counties in eastern Colorado. Some particular amounts include:
• 3.92 in Morgan county
• 3.00 in Logan county
• 2.53 in Douglas county
• 2.11 in Lincoln county
In addition to the rainfall, numerous severe weather reports were received yesterday afternoon. The National Weather Service issued thirteen tornado warnings and over a dozen actual tornado reports were received. Numerous hail reports, stating sizes from 1 inch to 2.5 inches were received from Pueblo, Cheyenne and Kit Carson. In addition to the flooding in Morgan and Logan counties, there were a handful of scattered flooding reports of washed out roadways and high streamflows. Finally, up to 10 inches of snow was officially recorded along the Palmer Ridge. What a day!
As always, please see the map below for estimated precipitation amounts in your area.
