Midlatitude cyclone producing snow and high winds across the Upper Midwest

May 9th, 2020 |

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly surface weather type plotted in red (R=rain; S=snow; F=fog) [click to pay animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly surface weather type plotted in red (R=rain; ZR=freezing rain; S=snow; L=drizzle; F=fog) [click to play animation | MP4]

GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed the circulation associated with a midlatitude cyclone that moved southeastward from southern Canada across the Upper Midwest on 09 May 2020. This system brought a variety of precipitation to the region, including snow with several inches of accumulation in parts of North Dakota and Minnesota.

Anomalously strong winds were associated with this storm, which produced peak wind gusts of 60 mph or higher in North Dakota and South Dakota — hourly surface winds with gusts are plotted on GOES-16 Water Vapor images (below).

GOES-16 Mid-level Water Vapor (6.9 µm) images, with plots of hourly wind barbs and gusts [click to pay animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with plots of hourly wind barbs and gusts [click to play animation | MP4]

GOES-16 Day Cloud Phase Distinction RGB images (below) revealed the northwest-to-southeast oriented swath of fresh snowfall (brighter shades of green) from eastern Saskatchewan ad western Manitoba into north-central North Dakota. The edges of the snow swath began to rapidly melt during the day, due to the warming power of the early May sun.

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

===== 10 May Update =====

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

As the surface low’s occluded front moved across southern Wisconsin on the morning of 10 May, GOES-16 Day Cloud Phase Distinction RGB images (above) provided a nice depiction of of the brief period of dynamic cooling and transition from rain to snow as glaciated cloud tops (shades of green) blossomed over the Madison (KMSN) area.

Melting snow cover across the High Plains and Midwest

April 17th, 2020 |

GOES-16

GOES-16 “Red” Visible (0.64 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm) and Day Cloud Phase Distinction Red-Green-Blue (RGB) images (above) revealed the rapid melting of parts of a broad swath of fresh snow cover (green in the RGB images) across the High Pains and Midwest on 17 April 2020. The snow melted quickly in central Nebraska (where storm totals were generally less than 4 inches), but persisted in the Foothills of Colorado (where storm totals amounts of 10-20 inches were common).

A closer look at the eastern segment of the snow cover over eastern Nebraska, southern Iowa and northern Missouri (below) showed the effect of snow-cooled surfaces on suppressing the formation of cumulus clouds as diurnal heating increased into the afternoon hours. Surface air temperatures warmed into the upper 40s to low 50s F in areas where the snow melted — but were held in the upper 30s to low 40s F where deeper snow cover existed near the Iowa/Missouri border (where storm total amounts were as high as 12-16 inches).

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 Day Cloud Phase Distinction RGB images [click to play animation | MP4]

Snow squalls across the Upper Midwest

April 9th, 2020 |

GOES-16

GOES-16 “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

The NWS Aberdeen forecast office issued a Snow Squall Warning on the morning of 09 April 2020 — and a sequence of GOES-16 (GOES-East) “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction Red-Green-Blue (RGB) images (above) showed the southeastward movement of numerous convective cloud features responsible for the snow squalls. Cloud elements whose tops were glaciating exhibited shades of green in the RGB images; however, most cloud-top infrared brightness temperatures were generally rather warm (therefore lacking a color enhancement). No signatures of lightning were seen in GLM Flash Extent Density data with this shallow, low-topped convection. Of particular interest was the ~20 mile wide northwest-to-southeast oriented swath of fresh snowfall produced by these snow squalls, which passed through Aberdeen (KABR) and could be seen through gaps in the clouds on Visible (shades of white) and RGB images (shades of green); Aberdeen received 0.3 inch of snowfall.

Farther to the south and east, NWS Sioux Falls also issued a Snow Squall Warning — similar signatures of convective elements were seen in the GOES-16 imagery (below), including the glaciation of some of the cloud tops. Snowfall amounts were generally light (around 0.1 inch), but surface visibility was reduced to zero in some of the snow squalls.

GOES-16 "Red Visible (0.64 µm), "Clean" Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

In addition, NWS Duluth issued a Snow Squall Warning; the corresponding GOES-16 imagery is shown below. Snowfall reports included 1.4 inches at Duluth (accumulating within 30 minutes) and 2.5 inches at Butternut, Wisconsin.

GOES-16 "Red Visible (0.64 µm), "Clean" Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm), “Clean” Infrared Window (10.35 µm) and Day Cloud Phase Distinction RGB images [click to play animation | MP4]

It should be noted that these were the first Snow Squall Warnings issued by each of the 3 NWS forecast offices.



Important aspects of the boundary layer across the Upper Midwest were revealed by plots of rawinsonde data from Aberdeen, South Dakota and International Falls, Minnesota (below) — steep low-level lapse rates (surface – 3 km values of 7ºC per km) with ample moisture, and strong winds. The upper portion of the shallow convective layers were within the important -12 to -18ºC dendritic growth zone.

Plots of 12 UTC rawinsonde data from Aberdeen, South Dakota and International Falls, Minnesota [click to enlarge]

Plots of 12 UTC rawinsonde data from Aberdeen, South Dakota and International Falls, Minnesota [click to enlarge]

A time-lapse video of snow squalls that moved through Madison, Wisconsin can be seen here.

Signature of ice accrual across the Upper Midwest

April 4th, 2020 |

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly precipitation type plotted in red [click to play animation | MP4]

GOES-16 Mid-level Water Vapor (6.9 µm) images, with hourly precipitation type plotted in red [click to play animation | MP4]

GOES-16 (GOES-East) Mid-level Water Vapor (6.9 µm) images (above) showed a variety of precipitation types as a strong cold front moved slowly eastward across the Upper Midwest during the 02 April03 April 2020 period — including thundersnow snow at Aberdeen, South Dakota and Oakes, North Dakota (at 18 UTC on 02 April) and freezing rain at a few sites in northern Iowa, the eastern Dakotas and western Minnesota.

On the following day, in a comparison of GOES-16 “Red” Visible (0.64 µm) and Day Snow Fog Red-Green-Blue (RGB) images (below), the RGB images revealed darker red swaths across southeastern South Dakota, northwestern Iowa and western Minnesota (at the 1.61 µm wavelength, ice absorbs radiation more strongly than snow — which contributed to the darker appearance of those swaths). Note that these ice accrual swaths exhibited no signature in the Visible imagery.

GOES-16 "Red" Visible (0.64 µm) and Day Snow Fog RGB images [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm) and Day Snow Fog RGB images [click to play animation | MP4]

Props to Carl Jones (NWS Grand Forks) for pointing this feature out.