Severe Thunderstorm Warning 4, NWS Rapid City, SD

078 
WWUS53 KUNR 202211
SVSUNR

Severe Weather Statement
National Weather Service Rapid City SD
411 PM MDT Thu May 20 2021

WYC005-202245-
/O.CON.KUNR.SV.W.0004.000000T0000Z-210520T2245Z/
Campbell WY-
411 PM MDT Thu May 20 2021

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 445 PM MDT
FOR NORTHWESTERN CAMPBELL COUNTY...

At 411 PM MDT, a severe thunderstorm was located 12 miles north of
Spotted Horse, or 45 miles southwest of Broadus, moving northwest at
15 mph.

HAZARD...60 mph wind gusts.

SOURCE...Radar indicated.

IMPACT...Expect damage to roofs, siding, and trees.

This severe thunderstorm will remain over mainly rural areas of
northwestern Campbell County.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

&&

LAT...LON 4500 10575 4480 10584 4479 10601 4499 10602
      4500 10581
TIME...MOT...LOC 2211Z 155DEG 13KT 4489 10593 

HAIL...<.75IN
WIND...60MPH
 
$$

Eagan

538 
WWUS53 KUNR 202216
SVSUNR

Severe Weather Statement
National Weather Service Rapid City SD
416 PM MDT Thu May 20 2021

WYC005-202226-
/O.CAN.KUNR.SV.W.0004.000000T0000Z-210520T2245Z/
Campbell WY-
416 PM MDT Thu May 20 2021

...THE SEVERE THUNDERSTORM WARNING FOR NORTHWESTERN CAMPBELL COUNTY
IS CANCELLED...
                
The storm which prompted the warning has weakened below severe
limits, and no longer poses an immediate threat to life or property.
Therefore, the warning has been cancelled.  However gusty winds are
still possible with this thunderstorm.

LAT...LON 4500 10575 4480 10584 4479 10601 4499 10602
      4500 10581
TIME...MOT...LOC 2214Z 154DEG 22KT 4492 10595 

$$

Eagan

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
248 PM MDT Thu May 20 2021

.DISCUSSION...(This Evening Through Thursday)
Issued at 223 PM MDT Thu May 20 2021

Upper analysis this aftn shows southwesterly flow aloft over the
forecast area ahead of an upper low over the western CONUS. Latest
surface analysis shows low pressure centered over SW WY/NE UT
with a trough/front extending northeastward into SE MT, resulting
in breezy to windy southeasterly low level flow across the
forecast area. Current dewpoints are mainly in the 40s across
northeastern Wyoming and in the 50s over western SD.

MLCAPE is currently around 1000J/KG with 0-6KM bulk shear ranging
from 30-45kt to the southwest of our northeastern Wyoming zones.
An upper shortwave, combined with diurnal heating and steepening
lapse rates, has helped to develop scattered thunderstorms over
the higher terrain of eastern Wyoming. Storms will continue to
move northeastward into the forecast area this afternoon and
evening. A few strong to severe storms are possible, with large
hail and damaging wind gusts.

The frontal boundary will move southeastward as a cold front
tonight. Behind the front, low stratus and possibly some drizzle,
will develop over northeastern Wyoming and parts of far western
South Dakota with the stratus expected to linger at least through
the morning.

On Friday, the cold front will stall somewhere east of the Black
Hills. Southwesterly flow aloft will continue to strengthen with
embedded waves. 1000-2000J/KG MLCAPE will develop along and to the
east of the cold front by afternoon. Relatively strong MLCIN will
be an issue, but suspect forcing along cold front will be
sufficient for surface based convection, some of which could be
strong/severe. However, notable uncertainty exists given forecast
soundings and potential for an extended period/area of stratus.

On Saturday and Sunday, deep southwesterly flow will continue as
moisture deepens. The upper low will eject into MT late Sunday.
This will promote rather high pops for the weekend with diurnally
driven convection. Temperatures will be near/slightly cooler than
average.

Next week looks drier, but storm track along US/Canadian border will
support periodic frontal passages and chances for showers and
thunderstorms.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1111 AM MDT Thu May 20 2021

VFR conditions are expected area-wide through about 21Z. Around
21Z, showers and thunderstorms will begin to move into
northeastern WY from the southwest, with activity generally moving
toward the northeast, entering far western South Dakota and the
Black Hills area around 00Z. Thunderstorm activity will continue
across northwest South Dakota through the evening hours. Isolated
to scattered severe storms could produce hail, brief strong wind
gusts, and localized MVFR/IFR conditions.

Following the thunderstorm activity, a cold front will cross the
area this evening. Behind the front, conditions will deteriorate
toward IFR as low stratus develops and persists through Friday
morning, across northeastern WY and far western SD. LIFR
conditions will be found across higher elevations late tonight
into Friday morning.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

DISCUSSION...10
AVIATION...15

Hazardous Weather Outlook
National Weather Service Rapid City SD
525 AM MDT Thu May 20 2021

SDZ001-002-012>014-024>032-041>044-046-047-049-072>074-WYZ054>058-
071-211300-
Harding-Perkins-Butte-Northern Meade Co Plains-Ziebach-
Northern Black Hills-Northern Foot Hills-Rapid City-
Southern Foot Hills-Central Black Hills-Southern Black Hills-
Custer Co Plains-Pennington Co Plains-Haakon-Fall River-
Oglala Lakota-Jackson-Bennett-Mellette-Todd-Tripp-
Sturgis/Piedmont Foot Hills-Southern Meade Co Plains-
Hermosa Foot Hills-Northern Campbell-Southern Campbell-
Western Crook-Wyoming Black Hills-Weston-Northeastern Crook-
525 AM MDT Thu May 20 2021 /625 AM CDT Thu May 20 2021/

This Hazardous Weather Outlook is for portions of western South
Dakota and northeastern Wyoming.

.DAY ONE...Today and Tonight

Isolated to scattered thunderstorms are expected this afternoon
and evening, potentially lingering into tonight. Some of these
storms could be severe, with damaging winds and large hail the
primary threats. Highest coverage of thunderstorms and potential
for severe storms will be over northeastern Wyoming and far
western South Dakota, including the Black Hills.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Shower and thunderstorm chances will continue across the area
through the weekend. Isolated strong to severe storms will also be
possible, particularly on Friday and Sunday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will not be needed today.

&&

Stay tuned to NOAA weather radio for further updates...or check
our web site at weather.gov/rapidcity

Special Weather Statement
National Weather Service Rapid City SD
352 PM MDT Thu May 20 2021

WYZ054-202215-
Northern Campbell WY-
352 PM MDT Thu May 20 2021

...STRONG THUNDERSTORM OVER NORTHWESTERN CAMPBELL COUNTY...

At 352 PM MDT, Doppler radar was tracking a strong thunderstorm 5
miles north of Spotted Horse, or 40 miles northwest of Gillette,
moving north at 30 mph.

Penny size hail and wind gusts up to 50 mph will be possible with
this storm.

Locations impacted include...
Spotted Horse.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4500 10581 4500 10564 4466 10579 4470 10601
      4499 10602
TIME...MOT...LOC 2152Z 186DEG 28KT 4479 10587

Eagan