Feb 8-9th Heavy Snow

Summary

A potent low pressure system slid from the northern US Rockies to across southern South Dakota on February 8th and 9th, and produced a relatively narrow band of heavy snow across the area as it did so by the time it exited on the morning of the 9th. These types of events are known in the field as "banded snow", and are notorious for producing locally heavy (sometimes very heavy) snow surrounded by very little snow. In this case, 16" of snow reportedly fell in Estelline, but only 2" fell in Milbank just 45 miles further north. This system also produced thundersnow. The SDDOT marked many roads as "No Travel Advised" by Sunday morning across central and east central South Dakota. 

Surface weather map at midnight on the 9th	Snowfall reports map	Snowfall map, estimated from NOHRSC	GOES-16 post-event satellite imagery
Radar reflectivity from 3pm to 9pm on the 8th	Radar reflectivity from 9pm on the 8th to 3am on the 9th	Snowfall rates of 1-3" per hour as estimated by radar. A public report of 8" in 4 hours just north of Huron helps verify that this is reasonable	Thundersnow occurred as this system produced lightning in the Brookings area and across southern Minnesota
14 miles north of Estelline, courtesy of Henry Ladner Jr	About 5" of snow in Watertown, courtesy of Brent Nathaniel	Just before the bridge east of Lake Norden, courtesy of the Lake Poinsett Estates Campground	Heavy snow of about 14" at Lake Poinsett, courtesy of the Lake Poinsett Estates Campground
Heavy snow of about 14" at Lake Poinsett, courtesy of the Lake Poinsett Estates Campground	About 4" of new snow in Pierre (bare ground previously), courtesy of Anthony Lueck	Couple vehicles in ditches across Hamlin County, courtesy of the Sheriff's Office	Area SDDOT webcams around 5:30 am on the 9th
Area SDDOT cams around 9:30 am on the 9th	Peak wind gusts during the heavy snow event	Banded snow explained

Listing of snowfall reports

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...        ..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....

            ..REMARKS..

0815 AM     Heavy Snow       Estelline               44.58N 96.90W        02/09/2020  E16.0 inch       Hamlin             SD   Public          

            14 to 16 inches of snow.

0745 AM     Heavy Snow       Bryant                  44.59N 97.47W        02/09/2020  M15.6 inch       Hamlin             SD   Public     

0700 AM     Heavy Snow       3 NNW Estelline         44.62N 96.93W        02/09/2020  M14.0 inch       Hamlin             SD   Public     

0800 AM     Heavy Snow       2 S Clear Lake          44.74N 96.68W        02/09/2020  M10.0 inch       Deuel              SD   Public           

            8 to 10 inches of snow.

0830 AM     Heavy Snow       Highmore                44.52N 99.44W        02/09/2020  M9.0 inch        Hyde               SD   Public          

0700 AM     Heavy Snow       1 WNW Hayti             44.66N 97.23W        02/09/2020  M8.9 inch        Hamlin             SD   CO-OP Observer  

            0.47 inches liquid. 24 hour report.

0800 AM     Heavy Snow       3 NW Spottswood         44.68N 98.54W        02/09/2020  M8.7 inch        Spink              SD   Cocorahs      

1120 AM     Heavy Snow       Hayti                   44.66N 97.20W        02/09/2020  E8.5 inch        Hamlin             SD   Public     

0948 PM     Heavy Snow       Gary                    44.79N 96.46W        02/09/2020  M8.0 inch        Deuel              SD   Trained Spotter 

            Snow total from last night.

0728 PM     Heavy Snow       4 WNW Onida             44.73N 100.14W         02/09/2020  M8.0 inch        Sully              SD   CO-OP Observer  

            Snow total from last night.

1130 AM     Heavy Snow       Gettysburg              45.01N 99.95W        02/09/2020  M7.5 inch        Potter             SD   Trained Spotter  

0730 AM     Heavy Snow       1 SSW Clear Lake        44.76N 96.68W        02/09/2020  M7.5 inch        Deuel              SD   Public          

0800 AM     Heavy Snow       Castlewood              44.73N 97.03W        02/09/2020  M7.1 inch        Hamlin             SD   CO-OP Observer  

            0.63 inches liquid. 24 hour report.

0230 AM     Heavy Snow       Estelline               44.58N 96.90W        02/09/2020  E6.0 inch        Hamlin             SD   Public          

            Report on social media saying easily 6 inches or more. Still snowing.

0900 AM     Snow             3 ESE Watertown         44.90N 97.11W        02/09/2020  M5.5 inch        Codington          SD   CO-OP Observer  

            CO-OP Observer station WRTS2 2.7 E Watertown.

0740 AM     Heavy Snow       3 ESE Watertown         44.90N 97.11W        02/09/2020  E5.5 inch        Codington          SD   Public          

            5 to 6 inches of snow.

0600 AM     Snow             Clark                   44.88N 97.74W        02/09/2020  M5.1 inch        Clark              SD   CO-OP Observer  

            CO-OP Observer station CAKS2 Clark.

0800 AM     Heavy Snow       4 S Garden City         44.90N 97.58W        02/09/2020  M5.0 inch        Clark              SD   Public   

0700 AM     Snow             9 N Holabird            44.65N 99.60W        02/09/2020  M5.0 inch        Hyde               SD   Cocorahs        

            Cocorahs station SD-HY-8 Holabird 8.5 N.

0800 AM     Snow             Faulkton                45.04N 99.13W        02/09/2020  M4.0 inch        Faulk              SD   CO-OP Observer 

0745 AM     Heavy Snow       Pierre                  44.37N 100.32W        02/09/2020  E4.0 inch        Hughes             SD   Public          

            Between 4 and 5 inches.

0600 AM     Heavy Snow       6 E Hayes               44.37N 100.90W        02/09/2020  M4.0 inch        Stanley            SD   CO-OP Observer  

            0.54 inches liquid. 24 hour report.

0600 PM     Snow             Timber Lake             45.43N 101.07W        02/09/2020  M3.8 inch        Dewey              SD   CO-OP Observer  

            Storm total.

0800 AM     Snow             La Bolt                 45.05N 96.68W        02/09/2020  M3.8 inch        Grant              SD   Cocorahs        

            Cocorahs station SD-GT-9 LaBolt.

0840 AM     Heavy Snow       2 ENE Pierre            44.38N 100.29W        02/09/2020  M3.6 inch        Hughes             SD   CO-OP Observer  

            0.32 inches liquid. 24 hour report.

1030 AM     Snow             7 S Whitlocks Bay Rec A 44.94N 100.24W        02/09/2020  E3.5 inch        Potter             SD   Public    

0855 AM     Heavy Snow       Doland                  44.90N 98.10W        02/09/2020  M3.0 inch        Spink              SD   CO-OP Observer  

            0.20 liquid. 24 hour report.

0800 AM     Snow             12 ESE Canning          44.36N 99.80W        02/09/2020  M3.0 inch        Hughes             SD   CO-OP Observer  

0700 AM     Heavy Snow       Mellette                45.15N 98.50W        02/09/2020  E3.0 inch        Spink              SD   Public          

            2 to 3 inches of snow.

1003 AM     Heavy Snow       1 S Pierre              44.35N 100.32W         02/09/2020  M2.5 inch        Hughes             SD   Cocorahs        

            0.15 inches liquid.

0710 AM     Snow             3 NNE Gann Valley       44.08N 98.97W        02/09/2020  M2.5 inch        Buffalo            SD   CO-OP Observer  

            CO-OP Observer station GNVS2 Gann Valley 3 NNE.

0700 AM     Snow             1 S Pierre              44.35N 100.32W         02/09/2020  M2.5 inch        Hughes             SD   Cocorahs        

            Cocorahs station SD-HG-10 Pierre 1 S.

0700 AM     Heavy Snow       Turton                  45.05N 98.10W         02/09/2020  M2.5 inch        Spink              SD   Public          

            COOP Observation.

0900 AM     Heavy Snow       Fort Pierre             44.36N 100.37W        02/09/2020  M2.0 inch        Stanley            SD   Cocorahs        

            0.12 inches liquid. 24 hour report.

0730 AM     Heavy Snow       1 NE Milbank            45.23N 96.62W        02/09/2020  M2.0 inch        Grant              SD   CO-OP Observer  

            0.10 inches liquid. 24 hour report.

0700 AM     Heavy Snow       Webster                 45.34N 97.52W        02/09/2020  M2.0 inch        Day                SD   Public 

0700 AM     Snow             Fort Pierre             44.36N 100.37W        02/09/2020  M2.0 inch        Stanley            SD   Cocorahs        

            Cocorahs station SD-ST-6 Fort Pierre 0.5 SE.

1001 AM     Heavy Snow       9 NNE Vivian            44.05N 100.25W        02/09/2020  M1.0 inch        Lyman              SD   Cocorahs        

            0.08 inches liquid.

0831 AM     Heavy Snow       Ipswich                 45.45N 99.04W        02/09/2020  M1.0 inch        Edmunds            SD   CO-OP Observer  

Feb 12th Blizzard

Summary

An arctic front raced southward across the Northern Plains during the morning and early afternoon across the area on Wednesday, Feb 12th. This front brought with it very cold air, a trace to ~1" of new snow, and strong wind gusts of 40 to 60 mph. The combination of either new or existing blowable snow (from the Feb 8-9th event) and strong winds led to widespread blizzard or near blizzard conditions during the morning commute. A blizzard by definition requires at least 3 hours of 35+ mph winds and at least 1/4 mile visibility, but even if this time criteria isn't met, conditions can still be extremely dangerous. The SDDOT marked many roads as "No Travel Advised" during the course of the event. By Thursday morning (13th), wind chill values ranged between -30 and -50 F for much of the area. 

Surface weather map at 6am on the 12th	Radar reflectivity from 3 to 11am on the 12th	Zoomed-in radar reflectivity from 4:37 to 7:12am, showing an initial fine line (strong wind gusts lofting snow) followed by a heavier band/snow squall	Hourly temperature from 4am to 2pm, showing the rapid advancement of cold air
Weather observations at the NWS office in Aberdeen. The red line is temperature - we dropped from 30 to 0 in 6 hours from 6am to noon	Peak wind gusts across the area on the 12th	24 hour temperature chance across the region, from 8pm on the 11th to 8pm on the 12th, of 30 to 45 degrees	Coldest observed air temperatures over the past 24 hours as of 11am on the 13th
Coldest observed wind chills over the past 24+ hours as of 11am on the 13th	Coldest observed wind chills over the past 24+ hours as of 11am on the 13th, continued	Significantly reduced visibility at Mellette at 8:50 am, courtesy of Marc @LanceCasual	Significantly reduced visibility on Hwy 81 in the Lake Poinsett area at 11:45 am, courtesy of the Lake Poinsett Estates Campground
<1/4 mile visibility at Mina Lake at 8:16 am, courtesy of a NWS employee	Significantly reduced visibility in the Summit area during the morning hours, courtesy of the SD Highway Patrol	Significantly reduced visibility on US281 & US212 near Redfield at 10:30am, courtesy of the SD Highway Patrol	SDDOT cam 9 miles west of Brandt on I-29 at 1:30pm
SDDOT cam near Harrold on US14 at 8:30 am	SDDOT cam ~20 miles north of Highmore on SD47 at 10am	SDDOT cam near Lake City on SD10 at 9am	SDDOT cam near Mellette at US281&SD20 at 8:30 am
SDDOT cam near Orient on US212&SD45 at 9am	SDDOT cam near Sisseton on I-29 at 9:30 am	SDDOT cam near Summit on I-29 at 7:30 am	SDDOT cam near Tolstoy on SD20 at 9am
SDDOT cam near Victor on I-29 at 9am	SDDOT cam near Watertown on I-29 at 10:30 am	SDDOT cam near Waubay on US12 at 9am