Flash Flooding and Hail in Iowa, June 22 to 23, 2019

Area Forecast Discussion
National Weather Service Des Moines IA
544 AM CDT Sat Jun 22 2019

.DISCUSSION.../Today through Friday/
Issued at 356 AM CDT Sat Jun 22 2019

Convective complex which developed in northern Missouri and far
southern Iowa late last evening has moved east as the low level jet
veered overnight.  In the wake of the convection, ample low level
moisture is trapped underneath the frontal inversion with widespread
low ceilings across central Iowa.  The clouds will likely linger for
a good portion of the day as the inversion remain in place for much
of the area.  The exception will be in the far south to southwest
where the front may slip into the state allowing for some clearing.
With a few storms having formed recently just south of the border,
will let the flash flood watch continue until 7AM, but it should be
able to be dropped at that point.  Have dropped highs slightly give
the widespread clouds expected today but should insolation increase
more than expected, temperatures will need to be raised.

850MB flow will increase from the south today into this evening as
moisture advection strengthens.  Models are indicating surfaced
based CAPE values rising to around 3500-4000 J/KG in southern Iowa
by this afternoon as the warm front pushes north. Given proximity of
weak surface low near KOMA by early evening along with a warm front
extending eastward, there appears to be sufficient shear for storm
organization.  Storms are likely to develop by late afternoon to
early evening as the CAP erodes near the surface low and first cells
are likely in the southwest.  Given somewhat favorable low level
profiles and strong instability, some of the initial cells are
likely to be supercellular with all threats possible.  The
convection will likely transition quickly from any discrete cells
into a linear feature moving east northeast across the state during
the evening with wind and hail threat.  The convective threat will
persist overnight as the front approaches from the west and moisture
transport persist into the state.  A flash flood watch may also be
needed tonight in portions of the forecast area although given the
somewhat progressive nature of convection, the threat may be
relatively isolated.

The threat of storms/rainfall persists into Sunday and Sunday night
as the upper low moves northeast across the state.  There are
varying solutions on progression of the low with NAM and CAMS
somewhat faster with slower movement from GFS and Euro.  The blends
have broadened out the window of precipitation threat during this
time and have gone this route.  Much of Monday into early Tuesday
should be dry with brief cooling into Monday before warm advection
begins late Monday into early Tuesday.  Another weak boundary slips
into the state by then with the next threat of storms late Tuesday
afternoon into the evening.  Upper ridging will then slowly build
into the central United States with warming temperatures throughout
the rest of the forecast.  Highs by late in the week will be
approaching 90 with humidity kicking in as well.  This should push
heat indicies toward 100 degrees by late in the week.

&&

.AVIATION.../For the 12Z TAFS through 12Z Sunday morning/
Issued at 544 AM CDT Sat Jun 22 2019

Low MVFR ceilings will continue through much of the day with low
stratus persisting. Surface flow will be easterly as a warm front
approaches from the south. Showers and thunderstorms will be
likely tonight with continued MVFR conditions in most locations
with IFR conditions in and around thunderstorms.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Flash Flood Watch until 7 AM CDT this morning for IAZ092>097.

&&

DISCUSSION...Cogil
AVIATION...Cogil

Hazardous Weather Outlook
National Weather Service Des Moines IA
439 AM CDT Sat Jun 22 2019

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-231100-
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-
439 AM CDT Sat Jun 22 2019

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

A few thunderstorms will be possible in southern and western Iowa
during the day with the main threat from heavy rain. By late
afternoon into tonight, thunderstorms will become likely with a
slight risk of severe thunderstorms across all of central Iowa.
Damaging winds and large hail will be the main threat, however a
tornado or two is possible when the storms first develop. Heavy
rainfall leading to localized flash flooding also remains
possible.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Thunderstorm chances persist into Sunday evening across central
Iowa. The main concern will be from heavy rainfall. There will be
an additional threat for thunderstorms later Tuesday into Tuesday
night. The threat of severe weather will be determined as the
event approaches.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed later today into tonight.