The slider above (imagery courtesy Tim Wagner, CIMSS, derived from the rooftop cameras on the AOSS Building in Madison WI) compares the relatively clean air of 27 May with the very poor air of 27 June. Smoke from forest fires, mostly in Canada, has overspread the upper midwest. The motion of that smoke on 27 June is plain to see in the animation of true color imagery, below, from the CSPP Geosphere site. Smoke is especially thick over northeastern WI, and the smoke as a whole is moving southward.

There are also roof-top cameras pointing north. That comparison of 27 May and 27 June images is shown below.

Thanks for the imagery Tim!!

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In a sequence of GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Aerosol Optical Depth (AOD) derived product images (above), the hazy appearance of the wildfire smoke was very pronounced in the otherwise cloud-free sky across eastern/southern Wisconsin, southern Lake Michigan, eastern Iowa and northern Illinois — and AOD values of 1.0 and higher (darker red) covered much of the region. In fact, AOD values near Milwaukee (KMKE) were close to 4.0 (below). Surface visibility at Kenosha (located in far southeastern Wisconsin) was as low as 3/4 mile. 

Ground-based lidar in Madison, Wisconsin revealed significant backscatter (due to the dense smoke) from the surface to an altitude of 2-3 km during much of the daytime hours (below). AOD values in the vicinity of Madison were generally in the 1.5-1.8 range during much of the day — and the surface visibility at Madison’s airport was as low as 1-1/4 miles at 19 UTC.

A Pilot Report 15 miles west of Madison MSN at 1300 UTC (below) indicated that the top of the smoke layer was at 10,000 feet (3.0 km).

HYSPLIT model 72-hour back trajectories (below) indicated that the source region for much of the smoke within the boundary layer at Madison WI, Milwaukee WI and Chicago IL — particularly at altitudes of 500 m and 1 km — was Quebec, where wildfire activity had been high since early June. 

Chicago had the worst air quality in the world Tuesday as wildfire smoke from Quebec, Canada, seeps into the Midwest. https://t.co/fYkAOuvtkB

— CBS Evening News (@CBSEveningNews) June 27, 2023

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.3 µm) images (above) include time-matched plots of Local Storm Reports — which showed thunderstorms that produced several tornadoes, hail to 4.00 inches in diameter and wind gusts to 70 mph (SPC Storm Reports) along with some heavy rainfall and flooding across much of Indiana (and parts of adjacent states) on 25 June 2023.

1-minute GOES-16 Visible and Infrared images that included an overlay of GLM Flash Extent Density (below) displayed notable lightning activity with these thunderstorms.

GOES-16 Lifted Index (LI) and Convective Available Potential Energy (CAPE) derived products (below) showed a destabilizing air mass within the pre-convective environment ahead of the approaching frontal boundary — the most unstable LI values were -8 to -9ºC, with CAPE values in the 1500-1800 J/kg range.

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Large hail caused multiple injuries at the Red Rocks Amphitheater to the west of Denver on 21 June 2023 (News story 1, 2, 3; see also this tweet from the NWS in Boulder at 0326 UTC). This occurred in a region that the Storm Prediction Center flagged as in an atmosphere with an Enhanced Risk of severe weather. The principal severe threat was hail. The animation above shows the RealEarth display of ProbSevere (version 3) and it shows the approach of the radar object that produced the hail; a severe thunderstorm warning was in place. The image below shows the probSevere readout at 0330 UTC; the yellow ‘X’ approximates the location of Red Rocks.

ProbSevere allows a readout of the components used in the probability computations. The Radar Object nearing Red Rocks in the image above is #344797 — and time series of the parameters are shown below (available in interactive form here for a few days). Hail has much larger probabilities than either wind or tornado in this case. Maximum Expected Hail Size at 0330 UTC was 2.46″.

Shortly after 0330 UTC, the radar object associated with the large hail over Red Rocks merged with the radar object to its east, radar object #345162, and its time series is shown below. Note the peak in ProbHail probabilities around 0330 UTC.

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ProbSevere LightningCast Probabilities also showed an enhanced threat of lightning for the hours surrounding the hail event, as shown below. The LightningCast contours shown below are not parallax-corrected (the ABI data are not parallax-corrected either). Thus the features are displayed farther from the sub-satellite point (at 0^oN, 75.2^oW) than in reality (as discussed here).

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This tweet describes the ground-based lightning observations near Red Rocks in the hours surrounding the hail event.

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As also discussed in this blog post, large hail injured as many as 90 people at a Red Rocks outdoor concert in Colorado just after local sunset on 21 June 2023. 1-minute Mesoscale Domain Sector “Clean” Infrared Window (10.3 µm) images (with/without an overlay of GLM Flash Extent Density) from GOES-16 (GOES-East) (above) and GOES-18 (GOES-West) (below) showed the east-northeastward motion of the parent thunderstorm, and the resultant path of damaging wind and large hail reports. Red Rocks Park is located near the center of the GOES-16/GOES-18 images.

Pulses of overshooting tops exhibited infrared brightness temperatures as cold as -72ºC at 0317 UTC (below) — which was about 9 minutes prior to the Local Storm Report of 2-inch diameter hail at Red Rocks — and that cold overshooting top occurred during a brief lightning jump (from 0311-0318 UTC), as indicated by GLM Flash Extent Density. Note the differences in parallax offset between the 2 satellites — a 50,000-ft cloud top feature over central Colorado would be displaced about 22 km (13.7 miles) to the northwest of its actual surface location in GOES-16 imagery, but displaced about 23 km (14.3 miles) to the northeast of is actual surface location in GOES-18 imagery. Parallax correction would therefore have displayed the cold overshooting top closer to the location of the 1.75-inch diameter hail report.

The CIMSS-produced full resolution (nominal 2 km) CLAVR-x Cloud Top Height of the coldest overshooting top was around 56,000 ft (below).

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