An SPC Marginal/Slight risk for severe storms existed across much of the eastern Colorado plains on 26 May 2017. Severe hail and wind would be the primary threat with storms that managed to develop. The tornado threat was quite low, but an isolated tornado was possible.
Storms began initiating near the I-25 corridor over the front range around Noon, primarily north of Pueblo. By early afternoon, cu were becoming increasingly agitated over the southeast mountains. An orphan anvil was observed drifting over Pueblo around 1:20 pm (Fig 1). Orphan anvils signify a failed convective initiation attempt due to loss of continued buoyancy, possibly due to the presence of a CAP. Oftentimes convection will initiate from the same general location shortly thereafter.
A little later, a long-lived supercell thunderstorm had developed in northeast Colorado and strengthened as it moved east towards the Kansas border. This storm produced large hail and a tornado. Severe signatures obvious in the 0.5 km, 5-min visible imagery from GOES-16 include overshooting tops and above-anvil cirrus plumes. Cumulus clouds are seen racing toward the core updraft region indicating rapid inflow. New rapid development is observed just west of the main supercell, and would quickly become tornado warned as well.
Severe storms were also present over northern El Paso County through much of the afternoon (Fig 3). Once again, overshooting tops and above anvil cirrus plumes were apparent with the strongest storms. These storms produced hail up to 2″ in diameter. Towards early evening, radar indicated strong low-level rotation with a storm prompting a tornado warning, though no tornado was observed.
– Bill Line, NWS
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