The NWS Storm Prediction Center has issued a

• Severe Thunderstorm Watch for portions of
  Iowa
  Northwest Illinois
• Effective this Wednesday morning from 355 AM until 1100 AM CDT.
• Primary threats include…
  Scattered large hail and isolated very large hail events to 2.5
  inches in diameter possible
  Scattered damaging wind gusts to 60 mph possible
  A tornado or two possible

SUMMARY…Severe thunderstorms are expected to develop through the
predawn hours across a large part of Iowa with large hail possible,
potentially including some significant hailstones (larger than
golfballs) on a localized basis. Storms may organize as they spread
east-southeastward toward the I-80 corridor of eastern Iowa and
eventually northwest Illinois toward/after sunrise, with damaging
wind potential also developing and possibly even some tornado risk
later this morning.

The severe thunderstorm watch area is approximately along and 75
statute miles north and south of a line from 30 miles west of Storm
Lake IA to 10 miles north northeast of Moline 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.

&&

AVIATION…A few severe thunderstorms with hail surface and aloft to
2.5 inches. Extreme turbulence and surface wind gusts to 50 knots. A
few cumulonimbi with maximum tops to 550. Mean storm motion vector
27045.