MIL-OSI USA: SPC Severe Thunderstorm Watch 489

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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.
SEL9

URGENT – IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 489
NWS Storm Prediction Center Norman OK
110 PM CDT Tue Sep 7 2021

The NWS Storm Prediction Center has issued a

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

* Effective this Tuesday afternoon and evening from 110 PM until
900 PM CDT.

* Primary threats include…
Scattered large hail likely with isolated very large hail events
to 2 inches in diameter possible
Scattered damaging wind gusts to 70 mph likely

SUMMARY…A line of thunderstorms currently developing from northern
Illinois into eastern Iowa will spread across the watch area this
afternoon and early evening. Damaging winds and hail will be
possible with the strongest cells.

The severe thunderstorm watch area is approximately along and 60
statute miles north and south of a line from 85 miles east of
Marseilles IL to 45 miles west northwest of Peoria IL. 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 488…

AVIATION…A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
26035.

…Hart

Note: The Aviation Watch (SAW) product is an approximation to the watch area. The actual watch is depicted by the shaded areas.
SAW9
WW 489 SEVERE TSTM IL IN LM 071810Z – 080200Z
AXIS..60 STATUTE MILES NORTH AND SOUTH OF LINE..
85E MMO/MARSEILLES IL/ – 45WNW PIA/PEORIA IL/
..AVIATION COORDS.. 50NM N/S /41SW GIJ – 43WSW BDF/
HAIL SURFACE AND ALOFT..2 INCHES. WIND GUSTS..60 KNOTS.
MAX TOPS TO 500. MEAN STORM MOTION VECTOR 26035.

LAT…LON 40498704 40059048 41789048 42238704

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

Watch 489 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

Mod (60%)

Probability of 1 or more hailstones > 2 inches

Mod (30%)

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

High (>95%)

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.

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