Hail and Damaging Winds in Iowa, June 4 to 5, 2020

Area Forecast Discussion
National Weather Service Des Moines IA
635 AM CDT Thu Jun 4 2020

.DISCUSSION.../Today through Wednesday/
Issued at 416 AM CDT Thu Jun 4 2020

MCS ongoing across eastern Kansas and into Missouri this morning.
This activity has a significant trailing stratiform region that is
extending into southern IA while a broad cirrus shield is blanketing
much of the state. Outflow from the MCS is lifting north with winds
becoming southerly and gusty now into the Creston and Osceola.
areas. Some uncertainty how far north the outflow will expand though
with light and variable winds to the north, it has very little
resistance. Further more, the outflow could become a trigger
mechanism over northern Iowa later today should it remain intact.
For most of the day, expect the cirrus to erode and much of the day
remaining dry with high temperatures again in the 80s to near 90. A
few storms are possible by late afternoon and early evening over
northern Iowa in vicinity of any remnant boundaries. More
significant activity is possible into the overnight hours with an
MCS originating over South Dakota and Nebraska then dropping
southeast along the instability axis into central Iowa as some of
the CAM solutions suggest. The more coarse guidance is all over the
place temporally and spatially with the afternoon boundary and
subsequent potential MCS. The situation will need to be monitored
closely as the overnight MCS could evolve into a QLCS with damaging
winds and even a few tornadoes. Conditions will also be favorable
for a few supercells given the good instability and sufficient deep
layer shear and could lead to a hail threat as well. Locally heavy
rainfall will also be possible with pwat values near 2 inches as
increasing moisture advection feeds into the state as the low level
jet increases. This is still an evolving situation and the forecast
will likely need fine tuning throughout the day to adjust for
mesoscale impacts from this mornings convection to the south.

Little change to the forecast beyond tonight. The upper low passing
across southern Canada will briefing stall the advancement of the
upper ridge to the west while surface high pressure moves across the
Upper Midwest Friday night into Saturday. A few storms remain
possible over southern Iowa Friday night while an isolated severe
storm, but largely the instability will be suppressed south of the
state as the stability from the high arrives. The upper ridge will
resume its push north and east Saturday night into Sunday and will
lift instability back across the state. This could bring a few
storms to central Iowa but the greatest potential will be over the
far north as the lack of mid-level moisture and weak lapse rates
should limit the areal extent of any activity. Monday is trending
dry. Higher pops remain in for Tuesday/Tuesday night. Long term
guidance continues to lift the remnants of Cristobal into the
Midwest which is plausible considering the upper ridge to the east
and long wave trough approaching from the west would support a more
northerly movement. Still, climatology still suggests a more
southeast path and pops will remain in for this period as regardless
if it is precipitation from Cristobal or from activity as the system
approaches from the west. Cooler air will arrive with the trough
passage, dropping highs back into the 70s. Until then highs in the
80s will be common with a few 90s possible today and again Monday.

&&

.AVIATION.../For the 12Z TAFS through 12Z Friday morning/
Issued at 633 AM CDT Thu Jun 4 2020

Thunderstorm chances will be the main weather during period.
Isolated showers early this morning will dissipate shortly.
Thunderstorms are possible across northern Iowa by mid to late
afternoon. Additional storms are possible throughout the night.
Light wind today except for possible higher gusts near storms. Any
lower ceilings will also be associated with thunderstorms.

&&

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

DISCUSSION...Donavon
AVIATION...Donavon

Hazardous Weather Outlook
National Weather Service Des Moines IA
356 AM CDT Thu Jun 4 2020

IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-
081>086-092>097-050900-
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-
356 AM CDT Thu Jun 4 2020

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

Thunderstorms are likely this evening and overnight. There is a
slight risk for strong to severe storms with large hail and
damaging winds the main threats, however a tornado is possible.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday

Strong to severe thunderstorms will linger across central and
southern Iowa into Friday morning.

Additional thunderstorm chances are forecast Friday and Saturday
afternoon and evenings. At this time, there is a marginal risk of
severe weather.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this evening.

Hagenhoff