WW 421 SEVERE TSTM SD WY 160050Z – 160700Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 421
NWS Storm Prediction Center Norman OK
650 PM MDT Sun Jun 15 2025
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Western and Central South Dakota
Far Northeast Wyoming
* Effective this Sunday night and Monday morning from 650 PM
until 100 AM MDT.
* Primary threats include...
Widespread damaging winds and isolated significant gusts to 85
mph likely
Isolated very large hail events to 2 inches in diameter possible
SUMMARY...An organized wind-producing squall line is forecast to
organize and move east across a large portion of the Watch area this
evening into the overnight. A few supercells with an attendant risk
for large hail are possible this evening over southern South Dakota.
As the squall line develops and moves east within a very favorable
lapse rate environment, expecting severe gusts (60-85 mph) to
accompany the stronger surges of outflow associated with the
thunderstorm complex.
The severe thunderstorm watch area is approximately along and 95
statute miles north and south of a line from 75 miles west northwest
of Rapid City SD to 30 miles east northeast of Pierre SD. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU1).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 418...WW 419...WW 420...
AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 75 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
27035.
...Smith
