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Wildfires force the closure of the Boundary Waters Canoe Area Wilderness in northeastern Minnesota

By Scott Bachmeier •

1-minute GOES-19 Visible images with an overlay of the Fire Mask derived product, along with plots of METAR and RAWS surface reports, from 1501 UTC on 13 July to 0100 UTC 14 July

1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Visible images with an overlay of the Fire Mask derived product (above) showed the smoke plumes and thermal signatures associated with numerous wildfires across far northeastern Minnesota and southern Ontario on 13 July 2026. An elevated fire risk was in place, due to very warm surface air temperatures (near to above 100 F), low relative humidity and winds occasionally gusting over 20 mph. With the recent trend of increasing wildfire activity across the immediate area, a decision was made to close all entrances to the Boundary Waters Canoe Area Wilderness at the end of the day on 13 July (this was only the third time that the BWCAW has been completely closed).

As the smoke drifted eastward across the airport at Thunder Bay, Ontario (METAR identifier CYQT), the surface visibility was reduced to 2.5-3.0 miles at times (below).

Plot of surface report data from Thunder Bay, Ontario from 1600 UTC on 13 July to 0100 UTC on 14 July [click to enlarge]

A closer view using 1-minute GOES-19 GeoColor RGB images with an overlay of Next Generation Fire System (NGFS) Fire Detection polygons (below) displayed the hot thermal signatures and dense smoke plumes of these wildfires. Over 33000 acres were burned in northeastern Minnesota on this day, with some of the wind-driven fires crossing the border into Ontario.

1-minute GOES-19 GeoColor RGB images with an overlay of NGFS Fire Detection polygons, along with plots of surface observations, from 1500 UTC on 13 July to 0100 UTC on 14 July

One example of the rapid rate of wildfire intensification is shown below — just 1.7 hours after initiation, a fire northeast of Ely, Minnesota exhibited the GOES-19 Band 7 detector saturation temperature of 138 C.

GOES-19 GeoColor RGB image with an overlay of NGFS Fire Detection polygons at 2029 UTC on 13 July — with/without a probe of NGFS parameters

Farther to the north over Ontario, one of the wildfires produced 3 pyrocumulonimbus (pyroCb) clouds (below), which exhibited cloud-top infrared brightness temperatures in the -40s C (shades of blue to cyan) and -50s C (shades of red) — and some GLM-detected lightning activity was seen with the 2 larger pyroCbs.

10-minute GOES-19 Infrared Window images combined with the Fire Mask derived product and GLM Flash Points, from 2200 UTC on 13 July to 0100 UTC on 14 July

The largest pyroCb (which appeared to be a merger of the initial 2 pyroCbs) eventually exhibited a minimum cloud-top infrared brightness temperature of -58.96 C at 0030 UTC (below).

GOES-19 Infrared Window image combined with the Fire Mask derived product at 0030 UTC on 14 July, with a cursor sample of the coldest cloud-top infrared brightness temperature [click to enlarge]

The cloud-top temperature of -58.96 C was not far below the tropopause, according to a plot of rawinsonde data from Pickle Lake, Ontario (below).

Plot of rawinsonde data from Pickle Lake, Ontario at 0000 UTC on 14 July [click to enlarge]

Categories: Air quality, Fire detection, GLM, GOES-19, Lightning, NGFS, RealEarth, Red-Green-Blue (RGB) images