The Decker Wildfire has been burning just a few miles south of Salida, CO in the far northern Sangre de Cristo wilderness since 8 September 2019. As of 13 October 2019, the fire had burned 8,118 acres and has prompted periodic evacuations and pre-evacuations. On 13 October 2019, the fire had broken containment during critical fire weather conditions. The intensification could be seen in GOES-East 3.9 um SWIR imagery via the flare up in brightness temperature south of Salida around 18Z (Fig 1).
Figure 1: 13 October 2019 GOES-East 3.9 um SWIR imagery over Colorado. Full res
The smoke plume was easily diagnosed in GOES-East visible imagery extending well east of the fire within strong westerly flow (Fig 2). A significant increase in smoke production was observed after 18Z, following the flare up seen in the SWIR imagery.
Figure 2: 13 October 2019 GOES-East 0.64 um visible imagery over Colorado. Full res
SNPP VIIRS True Color imagery with VIIRS Active Fires product overlaid during the early afternoon shows numerous thermal anomalies (~750 m spatial resolution) associated with the fire along with the extensive smoke plume (Fig 3).
Figure 3: 13 October 2019 SNPP VIIRS True Color Imagery and VIIRS Active Fires product over Colorado. Full res
The IMET tasked to the fire requested that WFO PUB request a mesoscale sector in support of the fire fighting activities. WFO PUB requested another mesoscale sector the following day (10/14) given continued critical fire weather conditions over the fire.
A photo taken around 2300 UTC from between Canon City and Pueblo shows the impressive smoke plume around sunset (Fig 4).
Figure 4: 13 October 2019 photograph taken of smoke plume extending from Decker Fire. Full res
A S-NPP pass during the night of the 13th provided VIIRS Day Night Band imagery over Colorado with favorable illumination. The Decker Fire is readily apparent in the imagery as a cluster of bright light south of Salida in a region that would otherwise be dark.
Figure 5: 14 October 2019 S-NPP VIIRS Day Night Band Near Constant Contrast Product. Full res
An early season winter storm brought much colder temperatures and widespread snowfall to portions of the eastern Rockies and high plains October 9-10. Analysis of GOES-16 water vapor imagery shows key large scale features associated with the system as it digs south into the Great Basin and WY/CO (Figure 1) through 12Z. Overlaid on the animation are 700-300 mb GFS-derived Quasi-Geostrophic Omega, highlighting regions of greatest ascent and descent, correlating with what is observed in the imagery. The surface cold front is also seen pushing south through the high plains.
Figure 1: 9-10 October 2019 GOES-16 6.2 um water vapor imagery with GFS QG omega contours and feature labels overlaid. Full res
Now analyzing GOES-16 IR imagery over the same period and zooming in, the southward progression of the cold front is easily diagnosed in the imagery, including the banking of cold air up against the Colorado front range and Sangre de Cristo Mountains. An overlay of a surface wind analysis confirms the progression of the front. 60 mph winds were measured behind the front across southern Colorado.
Figure 2: 9-10 October 2019 GOES-16 IR-Window imagery with MSAS surface wind analysis and location of cold front at 12Z overlaid. Full res
Behind the front in northern Colorado during the evening of the 9th, thunderstorms managed to develop, producing heavy graupel and small hail. GLM Flash Extent Density from GOES-16 showed a lightning jump during the development of the strongest storm, which produced up to 3/4″ hail.
Figure 3: 9 October 2019 GOES-16 IR-Window imagery (gray) with GLM Flash Extent Density (color) overlaid. Full res
The Suomi NPP VIIRS Day Night Band (DNB) Near Constant Contrast (NCC) product provided high resolution “visible” imagery during the night as the front pushed south and low clouds expanded across the plains, thanks to illumination from the moon.
Figure 4: 0820 UTC 10 October 2019 Suomi-NPP DNB NCC. Bright areas are cities, while dull gray areas are clouds. Full res
The storm system resulted in widespread snowfall amounts of up to around 5 inches over the portions of the Colorado I-25 corridor and eastern plains. The Day Cloud Phase Distinction RGB can be utilized during winter weather events to diagnose developing bands of snow or track ongoing snow bands during (especially in poor radar coverage areas). Using this event over southeast Colorado as an example, shades of cyan colored clouds (water clouds) transitioning to bright green represent increase of ice in the cloud top and a potential snow producing cloud/band (Fig 5). Multiple snow bands developed in the vicinity of Pueblo and areas south, expanding east through the afternoon in the presence of strong upper forcing and low-level easterly/northeasterly upslope flow.
Figure 5: 11 October 2019 GOES-16 Day Cloud Phase Distinction RGB. Full res
Overlaying base radar reflectivity, one can see the snow bands as observed in radar imagery match up well with our analysis of the bands in RGB imagery (Fig 6).
Figure 6: 11 October 2019 GOES-16 Day Cloud Phase Distinction RGB with base radar reflectivity overlay. Full res
NOAA-20 VIIRS DNB NCC imagery from the next evening provided an early view of snow cover over eastern Colorado from the previous day’s storm (Fig 7). Widespread snow cover is observed along the I-25 Corridor from Colorado Springs to Fort Collins, and much of the plains to the east. Further south, snow cover resulting from the banded snowfall is diagnosed near and south of Pueblo. Low clouds are masked with the GOES fog difference (blue).
Figure 7: 0801 UTC 11 October 2019 NOAA-20 VIIRS DNB NCC and GOES-16 10.3 – 3.9 um fog difference (values >2 K) over eastern Colorado. Full res
