Hail and Damaging Winds in Iowa, June 22, 2021

Area Forecast Discussion
National Weather Service Des Moines IA
303 PM CDT Tue Jun 22 2021

.DISCUSSION.../Tonight through Tuesday/
Issued at 302 PM CDT Tue Jun 22 2021

Forecast Highlights:
* Scattered Storms (a Few Severe) to persist this evening. Main
  hazards will be large hail and damaging winds.
* Widespread showers and thunderstorms (a Few Severe) Thursday and
  Friday to bring beneficial rain to Iowa
* Storm chances will linger over the weekend and into early next
  week. Uncertainty in storm coverage, especially early next week.

Shallow shower and weak t-storms have been gradually developing
early this afternoon in an area of weak instability along warm
frontal boundary. Sfc dew points have been climbing steadily into
the upper 50s most locations. Latest CAM guidance continues to show
destabilization through early evening, yielding MLCAPE's in the
vicinity of 1000 j/kg (should low 60s sfc dew points be
realized). Meanwhile, weak shortwave energy dropping into the
state will assist in mid-level thermal destabilization. Effective
shear values of 45-55 knots will be more than enough to aid
convective organization. Unseasonably low freezing level suggests
hail will be the primary threat initially, eventually
transitioning to a damaging wind threat as convection congeals by
late afternoon/early evening. Shortwave trof and nose of LLJ
continues to push east overnight, taking any lingering
shower/thunderstorm activity with it.

Wednesday will be dry as northwest flow prevails. H85/H7 WAA will be
effective in capping any daytime convective chances. Lacking any mid-
level moisture/clouds, temperatures tomorrow will warm back into the
mid-upper 80s for most places. The pattern is flattened Wednesday
night by shortwaves ejecting from close low on the south end of
developing eastern Pacific Rex Block. Lead shortwave will push
storms into western IA after midnight Wednesday night. Damaging
winds would be the more likely hazard with this activity.

Widespread shower and thunderstorm chances return statewide on
Thursday and will continue into Friday as sfc boundary pulls up
stationary E-W across Iowa. PWATS climb above 2" during the period
and along with a series of embedded shortwaves will set the stage
for very good chances for widespread precipitation, some of which
may be heavy. Any flash flood concerns would be confined to urban
areas, as low soil moisture and crops in agricultural land will
mitigate substantial run-off. Looks like 1-3 inches of rain (lighted
amount in NW; heaviest SE), with locally higher amounts possible.
Day 3 WPC ERO is well positioned to capture this. Severe threat will
be possible on Thursday as well, with large hail/damaging winds once
again the primary associated hazards.

The front sags south on Friday, gradually dragging rainfall chances
with it. Best chance for severe looks to move into southeast IA and
MO. Although lingering convection will still be a possibility,
especially Friday Morning.

Upper trough will move into the upper midwest Sat-Tue will yield
nearly daily afternoon/evening shower/thunderstorm chances along
with temps that fall short of seasonal values.

&&

.AVIATION.../For the 18Z TAFS through 18Z Wednesday afternoon/
Issued at 1248 PM CDT Tue Jun 22 2021

Aviation impacts for the period will center around isolated to
scattered thunderstorms this afternoon. A few showers have been
able to develop across central IA, but not much organization noted
w/ this activity yet. Expect add'l weak development through around
20z, with strengthening and better organization expected
thereafter. Best chances look to be KFOD to KDSM initially,
spreading into KALO and KOTM afterwards. Will lean on VCTS at area
terminals until initiation occurs. There is some severe weather
threat in the stronger storms today...hail and damaging winds
primary associated hazards. Activity will fester this evening
before shifting east of central IA terminals by midnight. With the
exception of lowered visibilities in thunderstorms, VFR conditions
expected through the period.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

DISCUSSION...Hahn
AVIATION...Hahn

Hazardous Weather Outlook
National Weather Service Des Moines IA
230 PM CDT Tue Jun 22 2021

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-231930-
Emmet-Kossuth-Winnebago-Worth-Palo Alto-Hancock-Cerro Gordo-
Pocahontas-Humboldt-Wright-Franklin-Butler-Bremer-Sac-Calhoun-
Webster-Hamilton-Hardin-Grundy-Black Hawk-Crawford-Carroll-Greene-
Boone-Story-Marshall-Tama-Audubon-Guthrie-Dallas-Polk-Jasper-
Poweshiek-Cass-Adair-Madison-Warren-Marion-Mahaska-Adams-Union-
Clarke-Lucas-Monroe-Wapello-Taylor-Ringgold-Decatur-Wayne-
Appanoose-Davis-
230 PM CDT Tue Jun 22 2021

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...This afternoon and tonight

Scattered thunderstorms are anticipated this afternoon and evening
and a few may be strong to severe with large hail and damaging
wind gusts the primary threats.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Thunderstorm chances return Thursday into Friday. Strong to severe
storms may be possible on Thursday. Heavy rainfall and localized
water issues may occur as well with potential for multiple rounds
of storms.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not anticipated.