Severe Thunderstorm Watch 521

Issued

Jul 17, 2019, 4:38 PM MDT (22:38 UTC)

Expired

Jul 17, 2019, 11:00 PM MDT

In force

6 hr

Issued by

the Storm Prediction Center

Largest hail expected

2.5 in

Strongest gust expected

60 kt

Two or more tornadoes

20%

One or more EF2 to EF5 tornadoes

2%

Ten or more severe wind reports

40%

One or more gusts of 65 knots or more

20%

Ten or more severe hail reports

50%

One or more hailstones of 2 inches or more

40%

Six or more combined severe hail and wind reports

80%

• Mesoscale Discussion 1505Jul 17, 2:41 PM MDT
• Mesoscale Discussion 1507Jul 17, 3:04 PM MDT
• Mesoscale Discussion 1512Jul 17, 6:46 PM MDT
• Mesoscale Discussion 1514Jul 17, 10:06 PM MDT

238 
WWUS20 KWNS 172236
SEL1  
SPC WW 172236
NDZ000-SDZ000-WYZ000-180500-

URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 521
NWS Storm Prediction Center Norman OK
440 PM MDT Wed Jul 17 2019

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Extreme southwestern North Dakota
  Western South Dakota
  Extreme northeastern Wyoming

* Effective this Wednesday afternoon and evening from 440 PM
  until 1100 PM MDT.

* Primary threats include...
  Scattered large hail and isolated very large hail events to 2.5
    inches in diameter possible
  Scattered damaging wind gusts to 70 mph possible
  A tornado or two possible

SUMMARY...Thunderstorms are expected to increase in coverage this
evening from Wyoming into western South Dakota, and other more
isolated storms will likely persist across southwestern North
Dakota.  The storm environment favors supercells capable of
producing large hail as the primary threat, though an isolated
tornado cannot be ruled out near the Black Hills.  Some clustering
of storms will also be possible by late evening across western South
Dakota, with an attendant threat for damaging winds.

The severe thunderstorm watch area is approximately along and 75
statute miles east and west of a line from 45 miles northeast of
Lemmon SD to 55 miles south of Rapid City 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 516...WW 517...WW
518...WW 519...WW 520...

AVIATION...A few severe thunderstorms with hail surface and aloft to
2.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 550. Mean storm motion vector
28030.

...Thompson

Severe Thunderstorm Watches in South Dakota, 2019Severe Thunderstorm Watches in North Dakota, 2019Every severe thunderstorm watch in 2019

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive.