During the first week of September, 2020, Colorado had some unusual weather, even by Colorado standards. For example, Denver set its all-time record high for September, reaching 101 degrees during the afternoon of September 5. This was also the latest date a 100-degree reading has ever been observed in Denver and tied the record for the number of 90-degree days for a year (73), and was the warmest temperature ever recorded before a day of measurable snowfall. Just two days later, a series of cold fronts dropped the temperature down to the low 30s by early Tuesday morning and broke earliest snowfall records in many places in eastern Colorado. Total snowfall accumulations were 1 to 3 inches across much of the eastern plains, 3 to 6 inches for cities along the mountains, and 4 to 10 inches for the mountains and foothills of the Front Range. (Source: National Weather Service Denver/Boulder Office)
Impacts to the research centers from this storm varied across the state from none to significant. The San Luis Valley received the most snow accumulation with 12- 15 inches of new snow and 1.5 to 2 inches of moisture. While the moisture was welcome, the storm closed the Research Center for two days and delayed the potato harvest for about a week. Potato vines were already terminated and waiting to be harvested so storm effects on yield was minimal.
The location with the most extreme weather among the AES sites was the Arkansas Valley Research Center (AVRC). The nearby CoAgMet station in LaJunta hit a maximum temperature record of 107.4 ⁰F on September 6 only to record a daily minimum temperature of 31.5 ⁰F three days later. Additionally, the AVRC had 4 – 6” of wet heavy snow, which was not expected and the earliest on record for that location as well. This heavy snow, along with high winds heavily damaged their large forage sorghum variety trials, causing lodging, which required a herculean effort combined with a lot of creativity for AVRC staff to harvest and record plot yields. The good news for all sites was that the predicted lows for the storm were never realized avoiding wide spread early frost damage for crops not yet at maturity.