An impressive upper-level trough brought significant snowfall to the Rocky Mountains on 17 November 2017. The storm system accelerated east through the evening and deepened a surface low and associated cold front. Convection developed along this front already during the morning of the 18th, including a few early day severe storms. Storms were developing within an SPC slight risk and severe thunderstorm watch, the main threat being damaging wind gusts.

The progression of the upper level trough is diagnosed in GOES-16 water vapor imagery. Entering northwest Colorado at the start of the loop, the shortwave accelerates southeast through the state into the Texas Panhandle and then east into Oklahoma by the end of the loop. Convection initiates at the end of the loop along a cold front ahead of the main shortwave energy.

Figure 1: 18 November 2017 GOES-16 15-min 6.2 um Water Vapor Imagery. Full res

Convection developed within the bounds of the default mesoscale sector 2, so no request was made. It is recommended that offices still make a mesoscale sector request even if the phenomenon is in a default sector, as other requests could move the sector. 1-min visible imagery from early in the day shows the development of strong-to-severe storms along the cold front heading towards Indianapolis.

Figure 2: 18 November 2017 GOES-16 1-min VIS. Full res

-Bill Line, NWS

“The GOES-16 data posted on this page are preliminary, non-operational data and are undergoing testing. Users bear all responsibility for inspecting the data prior to use and for the manner in which the data are utilized.”