Elevated smoke levels have been present in the upper Midwestern United States for well over a week, but recent synoptic-scale pattern shifts have started to bring in clearer (albeit warmer and more humid) air from the south. The following animation shows GOES-19-observed aerosol optical depth (AOD) for 1400 UTC (9:00 AM local time) for each day between 25 July and 8 August 2025. Even as far back as the beginning of this loop, Wisconsin, Michigan, and the western Great Lakes are shown to have very high levels of smoke.

The smoke has not disappeared from the midlatitudes of the northern hemisphere; it has simply propagated out to sea. The same aerosol optical depth product (this time viewing a larger portion of the GOES-19 disk) shows that very high levels of aerosol remain. While the air over the midwestern United States is in better shape, the same cannot be said for the northeastern United States and the maritime provinces of Canada. (Note: the high AOD in the lower right hand corner, behind the SSEC logo, is Saharan dust that has blown off into the Atlantic.)

The poor air quality observed by satellite can be verified by looking at a contemporaneous map of in situ air quality observations. The following image depicts PM2.5 s observed by the global network of in situ PurpleAir sensors. While not a governmental network, PurpleAir has the advantage of transcending national borders. There is clearly a strong relationship between the satellite-identified regions of high AOD and surface-based data.

This change in air quality was largely driven by shifts in the synoptic scale flow. Consider the two 500 mb charts displayed side by side. The one on the left is from 1200 UTC on 2 August 2025 while the right is from the same time but on 8 August 2025. For the earlier map, when air quality was at its worst for the Midwest, a high amplitude ridge was present over the western United States and the prairies of Canada. Temperatures were cool and dew points were lower than typical for early August, but the air was originating from the Canadian wildfires and advecting smoke into the central United States. Contrast that with the later map. A ridge is now present over the upper midwest, bring with it heat and humidity, but also air from smoke-free regions.

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5-minute PACUS sector GOES-18 (GOES-West) Clean Infrared Window (10.3 µm) images and Red Visible (0.64 µm) images with an overlay of the FDCA Fire Mask derived product (above) showed that the Bronco Fire in southeast Arizona produced a pyrocumulonimbus (pyroCb) cloud as it was experiencing very active to extreme fire behavior on 07 August 2025. The pyroCb cloud exhibited cloud-top 10.3 µm infrared brightness temperatures (IRBTs) in the -40s C (denoted by shades of blue to cyan) — a necessary condition to be classified as a pyroCb — beginning at 2156 UTC on 07 August.

Note that smoke drifting north-northeastward from the Bronco Fire eventually reduced the surface visibility to 4 miles at Show Low (METAR identifier KSOW) by 0100 UTC on 08 August (below).

The hazy signature of northward-drifting smoke was apparent in GOES-18 True Color RGB images from the CSPP GeoSphere site (below).

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The coldest pyroCb cloud-top IRBT was -51.59ºC at 0016 UTC on 08 August (above). On a plot of rawinsonde data from Tucson, Arizona (below) the air temperature of -51.59ºC occurred at an altitude around 11.3 km — not far below the Most Unstable (MU) air parcel’s Maximum Parcel Level (MPL) of 11.6 km.

The Bronco Fire burned very hot, intermittently exhibiting 3.9 µm infrared brightness temperatures as high as 137.88ºC — which is the saturation temperature of the GOES-18 ABI Band 7 detectors — from 2111 UTC on 07 August to 0016 UTC on 08 August (below).

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1-minute Mesoscale Domain Sector GOES-19 (GOES-East) Clean Infrared Window (10.3 µm) images (above) showed a cluster of thunderstorms that eventually congealed into a large Mesoscale Convective System, producing a tornado, hail as large as 2.75″ in diameter and wind gusts as high as 99 mph (SPC Storm Reports) across parts of eastern South Dakota on 05 August 2025. Frequent pulses of overshooting tops were apparent with these thunderstorms.

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A radiometrically retrieved Himawari-9 Ash Height product from the NOAA/CIMSS Volcanic Cloud Monitoring site (above) showed the volcanic cloud produced by the first recorded eruption of Krasheninnikov on the Kamchatka Peninsula of Russia, which began around 1650 UTC on 02 August 2025 (KVERT advisory). The Ash Height reached the 7-8 km range (darker shade of green) at times.

A Himawari-9 Ash Loading product (below) indicated that portions of the volcanic cloud occasionally contained fairly high levels of ash loading (shades of red).

Himawari-9 Ash RGB images produced using Geo2Grid (below) suggested that the volcanic cloud was composed of both primarily ash (shades of red/pink) and a mixture of ash and SO₂ (shades of yellow).

NEW: Incredible video of The FIRST HISTORICALLY RECORDED ERUPTION of Krasheninnikov Volcano in Kamchatka, Russia.

Scientists think it may have been triggered by the M8.8 earthquake that struck off the coast of Kamchatka, Russia on 30 July 2025, at 11:24:52 local time.… pic.twitter.com/1ZQcZxSs1G

— Volcaholic ? (@volcaholic1) August 3, 2025

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