SPC Severe Thunderstorm Watch 520

Source: US National Oceanic and Atmospheric Administration

Note:  The expiration time in the watch graphic is amended if the watch is replaced, cancelled or extended.Note: Click for Watch Status Reports.
SEL0

URGENT – IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 520
NWS Storm Prediction Center Norman OK
400 PM CDT Thu Aug 18 2022

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of
Northwest Iowa
South-central to northeast Nebraska
Far southeast South Dakota

* Effective this Thursday afternoon and evening from 400 PM until
900 PM CDT.

* Primary threats include…
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Isolated damaging wind gusts to 65 mph possible

SUMMARY…A couple discrete supercells may develop along a cold
front into early evening. Large hail is the main hazard.

The severe thunderstorm watch area is approximately along and 45
statute miles east and west of a line from 45 miles north of Sioux
City IA to 15 miles west southwest of Hastings NE. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU0).

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.

&&

AVIATION…A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 55 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
34020.

…Grams

Note: The Aviation Watch (SAW) product is an approximation to the watch area. The actual watch is depicted by the shaded areas.
SAW0
WW 520 SEVERE TSTM IA NE SD 182100Z – 190200Z
AXIS..45 STATUTE MILES EAST AND WEST OF LINE..
45N SUX/SIOUX CITY IA/ – 15WSW HSI/HASTINGS NE/
..AVIATION COORDS.. 40NM E/W /40SSE FSD – 54SSW OBH/
HAIL SURFACE AND ALOFT..2 INCHES. WIND GUSTS..55 KNOTS.
MAX TOPS TO 500. MEAN STORM MOTION VECTOR 34020.

LAT…LON 43059549 40509784 40509955 43059727

THIS IS AN APPROXIMATION TO THE WATCH AREA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE WOUS64 KWNS
FOR WOU0.

Watch 520 Status Report Message has not been issued yet.

Note:  Click for Complete Product Text.TornadoesProbability of 2 or more tornadoes

Low (10%)

Probability of 1 or more strong (EF2-EF5) tornadoes

Low (5%)

WindProbability of 10 or more severe wind events

Low (20%)

Probability of 1 or more wind events > 65 knots

Low (10%)

HailProbability of 10 or more severe hail events

Mod (40%)

Probability of 1 or more hailstones > 2 inches

Mod (30%)

Combined Severe Hail/WindProbability of 6 or more combined severe hail/wind events

Mod (60%)

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.