Storm Prediction Center Severe Thunderstorm Watch 639

Note: 
The expiration time in the watch graphic is amended if the watch is
replaced, cancelled or extended.
Note: Click for Watch Status Reports.

   SEL9

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 639
   NWS Storm Prediction Center Norman OK
   350 PM CDT Tue Sep 1 2026

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Far Northwest Iowa
     Far Southwest Minnesota
     North-Central and Northeast Nebraska
     Southeast South Dakota

   * Effective this Tuesday afternoon and evening from 350 PM until
     1100 PM CDT.

   * Primary threats include...
     Scattered damaging winds likely with isolated significant gusts
       to 80 mph possible
     Scattered large hail likely with isolated very large hail events
       to 2 inches in diameter possible
     A tornado or two possible

   SUMMARY...Initial supercells will likely pose a threat for large
   hail up to 2 inches in diameter. A tornado or two may also occur
   with any sustained supercell, especially if thunderstorms can remain
   at least semi-discrete through early evening as low-level shear
   increases. Otherwise, a bowing cluster is expected to eventually
   develop and pose a greater threat for severe/damaging winds up to
   70-80 mph as it tracks generally eastward across southeast South
   Dakota/northeast Nebraska and vicinity.

   The severe thunderstorm watch area is approximately along and 60
   statute miles north and south of a line from 60 miles northwest of
   Burwell NE to 35 miles east southeast of Sioux Falls SD. For a
   complete depiction of the watch see the associated watch outline
   update (WOUS64 KWNS WOU9).

   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 638...

   AVIATION...A few severe thunderstorms with hail surface and aloft to
   2 inches. Extreme turbulence and surface wind gusts to 70 knots. A
   few cumulonimbi with maximum tops to 550. Mean storm motion vector
   25030.

   ...Gleason

   SEL9

   URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 639
   NWS Storm Prediction Center Norman OK
   350 PM CDT Tue Sep 1 2026

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Far Northwest Iowa
     Far Southwest Minnesota
     North-Central and Northeast Nebraska
     Southeast South Dakota

   * Effective this Tuesday afternoon and evening from 350 PM until
     1100 PM CDT.

   * Primary threats include...
     Scattered damaging winds likely with isolated significant gusts
       to 80 mph possible
     Scattered large hail likely with isolated very large hail events
       to 2 inches in diameter possible
     A tornado or two possible

   SUMMARY...Initial supercells will likely pose a threat for large
   hail up to 2 inches in diameter. A tornado or two may also occur
   with any sustained supercell, especially if thunderstorms can remain
   at least semi-discrete through early evening as low-level shear
   increases. Otherwise, a bowing cluster is expected to eventually
   develop and pose a greater threat for severe/damaging winds up to
   70-80 mph as it tracks generally eastward across southeast South
   Dakota/northeast Nebraska and vicinity.

   The severe thunderstorm watch area is approximately along and 60
   statute miles north and south of a line from 60 miles northwest of
   Burwell NE to 35 miles east southeast of Sioux Falls SD. For a
   complete depiction of the watch see the associated watch outline
   update (WOUS64 KWNS WOU9).

   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 638...

   AVIATION...A few severe thunderstorms with hail surface and aloft to
   2 inches. Extreme turbulence and surface wind gusts to 70 knots. A
   few cumulonimbi with maximum tops to 550. Mean storm motion vector
   25030.

   ...Gleason

Note:
The Aviation Watch (SAW) product is an approximation to the watch area.
The actual watch is depicted by the shaded areas.

   SAW9 
   WW 639 SEVERE TSTM IA MN NE SD 012050Z - 020400Z
   AXIS..60 STATUTE MILES NORTH AND SOUTH OF LINE..
   60NW BUB/BURWELL NE/ - 35ESE FSD/SIOUX FALLS SD/
   ..AVIATION COORDS.. 50NM N/S /11S ANW - 34ESE FSD/
   HAIL SURFACE AND ALOFT..2 INCHES. WIND GUSTS..70 KNOTS.
   MAX TOPS TO 550. MEAN STORM MOTION VECTOR 25030.

   LAT...LON 43269998 44259609 42529609 41529998

   THIS IS AN APPROXIMATION TO THE WATCH AREA.  FOR A
   COMPLETE DEPICTION OF THE WATCH SEE WOUS64 KWNS
   FOR WOU9.

Watch 639 Status Report Message has not been issued yet.

Note:
 Click for Complete Product Text.

Tornadoes

Wind

Hail

Combined Severe Hail/Wind

For each watch, probabilities for particular events inside the watch
(listed above in each table) are determined by the issuing forecaster.
The “Low” category contains probability values ranging from less than 2%
to 20% (EF2-EF5 tornadoes), less than 5% to 20% (all other probabilities),
“Moderate” from 30% to 60%, and “High” from 70% to greater than 95%.
High values are bolded and lighter in color to provide awareness of
an increased threat for a particular event.