SPC Severe Thunderstorm Watch 391

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.
SEL1

URGENT – IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 391
NWS Storm Prediction Center Norman OK
330 PM CDT Sat Jul 24 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of
Northern Illinois
Northern Indiana
Southwest Lower Michigan
Lake Michigan

* Effective this Saturday afternoon and evening from 330 PM until
1000 PM CDT.

* Primary threats include…
Scattered damaging wind gusts to 70 mph possible
Isolated large hail events to 1.5 inches in diameter possible

SUMMARY…Thunderstorms are slowly intensifying along a line from
north of Chicago into northwest Illinois. These storms will spread
southward through the afternoon, posing a risk of locally damaging
wind gusts and hail.

The severe thunderstorm watch area is approximately along and 45
statute miles north and south of a line from 50 miles west southwest
of Marseilles IL to 35 miles southeast of Kalamazoo MI. 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 390…

AVIATION…A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
30025.

…Hart

SEL1

URGENT – IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 391
NWS Storm Prediction Center Norman OK
330 PM CDT Sat Jul 24 2021

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of
Northern Illinois
Northern Indiana
Southwest Lower Michigan
Lake Michigan

* Effective this Saturday afternoon and evening from 330 PM until
1000 PM CDT.

* Primary threats include…
Scattered damaging wind gusts to 70 mph possible
Isolated large hail events to 1.5 inches in diameter possible

SUMMARY…Thunderstorms are slowly intensifying along a line from
north of Chicago into northwest Illinois. These storms will spread
southward through the afternoon, posing a risk of locally damaging
wind gusts and hail.

The severe thunderstorm watch area is approximately along and 45
statute miles north and south of a line from 50 miles west southwest
of Marseilles IL to 35 miles southeast of Kalamazoo MI. 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 390…

AVIATION…A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
30025.

…Hart

Note: The Aviation Watch (SAW) product is an approximation to the watch area. The actual watch is depicted by the shaded areas.
SAW1
WW 391 SEVERE TSTM IL IN MI LM 242030Z – 250300Z
AXIS..45 STATUTE MILES NORTH AND SOUTH OF LINE..
50WSW MMO/MARSEILLES IL/ – 35SE AZO/KALAMAZOO MI/
..AVIATION COORDS.. 40NM N/S /4SSE BDF – 54N FWA/
HAIL SURFACE AND ALOFT..1.5 INCHES. WIND GUSTS..60 KNOTS.
MAX TOPS TO 500. MEAN STORM MOTION VECTOR 30025.

LAT…LON 41748957 42528507 41228507 40438957

THIS IS AN APPROXIMATION TO THE WATCH AREA. FOR A
COMPLETE DEPICTION OF THE WATCH SEE WOUS64 KWNS
FOR WOU1.

Watch 391 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 ( 65 knots

Low (20%)

HailProbability of 10 or more severe hail events

Low (20%)

Probability of 1 or more hailstones > 2 inches

Low (10%)

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.