GOES-16 (GOES-East) Day Snow-Fog RGB images (above) showed widespread horizontal convective rolls (HCRs) which highlighted areas where blowing snow was more concentrated across parts of southern Manitoba and the Upper Midwest on 06 February 2021. Snow cover (and glaciated clouds) appeared as shades of red, with bare ground exhibiting lighter shades of green and low-level water droplet clouds appearing as brighter shades of white.

Closer views of the northern, central and southern portions of the region where blowing snow was most prevalent are shown below. The HCRs were evident during the early to late morning hours across southern Manitoba, far eastern North Dakota and northwestern Minnesota — and then became more apparent across western/southern Minnesota extending into far northern Iowa as the day progressed. Surface reports showed that the visibility fluctuated dramatically at some sites as HCRs moved through.

In comparisons of MODIS True Color and False Color RGB images from Terra (above) and Aqua (below), the areal coverage of HCRs could be seen in the False Color imagery.

Farthest to the north, one cluster of HCRs appeared to originate over Lake Manitoba — as seen in 30-meter resolution Landsat-8 False Color imagery from RealEarth (below).

Two notable pilot reports across southern Minnesota (below) showed that flight visibility was restricted to 4 miles at an elevation of 3000 feet, and the tops of HCRs extended to 5000 feet.

Additional material on satellite identification of blowing snow is available here and here.

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GOES-16 (GOES-East) “Red” Visible (0.64 µm) images (above) showed a cyclone (surface analyses) moving off the coast of Uruguay on 05 February 2021. What appeared to be an eye-like feature developed at the storm center toward the end of the day.

A toggle between VIIRS True Color RGB images from Suomi NPP and NOAA-20 as viewed using RealEarth (below) provided a larger scale perspective of the cyclone.

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Suomi NPP VIIRS Infrared Window (11.45 µm) images (above) revealed a large area of cold surface infrared brightness temperatures across much of the North Slope of Alaska on 04 February 2021 — with the coldest IR temperature being -56ºC (darker shades of violet) about 30 miles south-southeast of Umiat (PAUM) on the 1221 UTC image. The surface air temperature at the nearby Umiat RAWS site around that time was -55ºF (-48.3ºC). Narrow fingers of cold air drainage into some of the river valleys along the northern slopes of the Brooks Range (topography) were also apparent.

The corresponding GOES-17 “Clean” Infrared Window (10.35 µm) images (below) also showed the large area of cold surface IR brightness temperatures, but the temperatures were not as cold (in the -40 to -50ºC range), and the small-scale signatures of various topographical features were not depicted.

A toggle between Infrared Window images from Suomi NPP VIIRS and GOES-17 (10.35 µm) at 1223 UTC is shown below.

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A rare, mostly clear day over the Great Lakes (and favorable orbital geometry) allowed NOAA-20, above, and Suomi-NPP, below, to image all 5 Great Lakes in one scene.  These images were produced from data that were downloaded at the Direct Broadcast site at CIMSS and processed with CSPP and Polar2Grid;  imagery is available at this link:  ftp://ftp.ssec.wisc.edu/pub/eosdb.  Although many bays appear ice covered (Green Bay in Lake Michigan, Saginaw Bay in Lake Huron, Chequamegon Bay in Lake Superior, there is otherwise a notable lack of ice in the lakes (the feature in central Lake Michigan is cloud).  Current forecasts of sub-zero weather over the western Great Lakes by this coming weekend suggest an increase in ice cover is likely.

The biggest difference between Lake Erie and the other lakes is color.  Why is Lake Erie not a dark blue?  Part of this is depth:  Lake Erie is the shallowest of the Great Lakes.  The browns and lighter blues are the result of sediment from both rivers and from white clay minerals along the northern shore of Lake Erie.  Phytoplankton is also affecting the water color;  not in the sense of an algal bloom, but a persistent algal presence  (Click here for an estimate of Chlorophyll from 21 January, from this website).  (Thanks to scientists at the Great Lakes node of NOAA’s Coast Watch — part of GLERL — for this explanation).

The (mostly) clear skies over the Lakes allowed for an estimate of Lake Surface Temperatures using VIIRS data and the ACSPO (Advanced Clear Sky Processor for Oceans) algorithm, shown below with colors representing temperatures from 32 to 41ºF (0 to 5º C).  Portions of Lakes Michigan, Huron and Ontario (red and white in the color enhancement) show surface temperatures near 41ºF.  Lakes Superior and Erie are relatively cooler.  Much of central Lake Erie is near 35ºF (cyan in the enhancement);  values in eastern Lake Erie are closer to 38ºF (yellow in the enhancement).  Eastern Lake Superior also shows values in the upper 30s.

GOES ABI

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