Flood and Hail in Iowa, June 14 to 15, 2022

Area Forecast Discussion
National Weather Service Des Moines IA
644 AM CDT Tue Jun 14 2022

...Updated for the 12z Aviation Discussion...

.DISCUSSION.../Today through Monday/
Issued at 400 AM CDT Tue Jun 14 2022

Key messaging highlights:

* Strong, gusty winds west this morning
* Hot and humid area wide today, and again southeast Wednesday
* Severe storms and heavy rains possible tonight and Wednesday
* Extreme heat possible early next week

There is a lot to consider this morning with impactful weather
possible across several elements for the next few days. At onset
this morning, a small high-based convective cluster producing
strong winds was entering southeast SD, but should remain
northwest of our forecast area based on extrapolation and local
forecast soundings. Of course this cluster shouldn't be there
either based on model soundings, but apparently there is a bit
more moisture there than depicted by the models. Early morning
temps were still in the lower 80s area wide, 3-10 degrees warmer
than this time yesterday, setting the stage for both record or
near record highs today and record maximum lows, the latter
depending on convective trends this evening. The brisk SSW winds
keeping our temperatures up may mix further by mid morning,
tapping what soundings over western sections suggest may be a
brief period of 40-45 mph gusts. The duration shouldn't be more
than a few hours however with the low level jet fading so will not
issue an advisory for wind. The Heat Advisory will remain in
effect today however. Although the 925/850mph thermal ridge is
past to the north, wind and mixing will be stronger today so
expect highs at or above persistence in most locations, with the
biggest difference north where the warm front has now passed.

Our attention this evening will then quickly turn to convective
trends. Expectations are to remain capped through much of the
afternoon, however by the evening hours the combination of
increasing 1-2km moisture, and cooling associated with forcing
from the bottom of the Rockies upper trough and current NM to NE
PV stream should allow convection to develop along and just behind
the current NE/SD frontal boundary as it enters western sections.
With MLCAPEs possibly reaching 4000 J/kg, and effective shear
increasing sharply from just behind the front to the northwest,
some severe weather is certainly possible with hail and wind the
primary threats. Locally heavy rains will be quite possible too
with precipitable water values approaching 2" and warm cloud
depths 4+km. Faster cluster movement driven by a 40kt mean wind
may reduce the locally heavy rain and flash flooding potential
somewhat, especially behind the front, however any cells anchored
along the front or nearby outflow boundaries sufficiently near the
SW 30kt 925/850mb low level jet could see the mean wind oppose
that and result in negligible cell movement boosting flash flood
potential. Recent Nam, NamNest, and NSSL ARW runs all depict three
hour rainfalls of 2-4", exceeding three hour Flash Flood
Guidance. Areal coverage would be minimal, and the HRW FV3 and ARW
convection allowing models are not as bullish, so no headline as
of yet, but cannot argue with Marginal/Slight WPC Excessive
Rainfall potential. The severe potential will ramp up again
overnight into Wednesday morning with with aforementioned upstream
forcing mechanisms developing a trailing MCS across NE into IA.
HREF updraft helicities are actually more aggressive with this
instance than earlier in the evening, so strong to severe storms
are possible north and west approaching daybreak.

Some post-frontal convection may linger into Wednesday, but eyes
will turn to the potential for surface based develop along the
front by late peak heating. 3000 J/kg uncapped MLCAPEs are
expected south and east of Des Moines, and with the upper trough
in closer proximity, deep shear will increase keeping strong to
severe storms and possibly supercells in the picture. The 0-1km
kinematics aren't too favorable for tornadoes in this window
either, but the potential cannot be ruled out considering the
degree of instability both tonight and late tomorrow. With the
front not clearing the forecast area through the afternoon south
and east, heat indices may again reach 100 degrees southeast, so
have blended into adjacent EAX and DVN headlines and added add a
Heat Advisory 1-8pm.

There will be lingering low chances for additional convection
south Thursday, but things should dry out to end the week as the
progressive pattern again builds upper level ridging through the
Rockies. This looks to be even more extreme than our current
situation however with brisk SSW winds and increasing heights
boosting temps well through the 90s and possibly touching the
century mark early next week, making additional heat headlines
quite possible. Although there are some token nocturnal chances in
the forecast through this period, much of the forecast looks dry.

&&

.AVIATION.../For the 12Z TAFS through 12Z Wednesday morning/
Issued at 644 AM CDT Tue Jun 14 2022

There is high confidence in VFR conditions through much of the
day with nothing beyond patchy mid and high cloudiness. SSW winds
will be gusty today however, especially west during the morning
where gusts may reach 40kts. Chances for storms and at least MVFR
conditions increase this evening and overnight, but confidence in
timing and location is not great, thus there is nothing more than
a cursory mention at the moment with thunder omitted until trends
dictate otherwise.

&&

.CLIMATE...
Issued at 400 AM CDT Tue Jun 14 2022

Another day of record or near record heat is expected today,
which may lead to both high and maximum low records for
Tuesday/Today. The records for our five primary climate sites are
noted below. Waterloo, Ottumwa, and Lamoni would be the more
likely record high locations today based on the current forecast.
Record maximum low records appear likely at all five locations,
but this will be dependent on convective trends into this evening
as well.

Today's record highs:

Mason City (100/1987)
Des Moines (101/1886)
Waterloo (99/1987)
Lamoni (96/1987)
Ottumwa (99/1987)

Today's record maximum lows (though 1am CDT/midnight CST):

Mason City (73/1994)
Des Moines (75/1994)
Waterloo (75/1994)
Lamoni (77/1981)
Ottumwa (77/1981)

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 7 PM CDT this evening for IAZ004>006-015-016-
023>025-033>039-044>050-057>062-070>075-081>086-092>097.

Heat Advisory from 11 AM this morning to 7 PM CDT this evening
for IAZ007-017-026>028.

Heat Advisory from 1 PM to 8 PM CDT Wednesday for IAZ062-075-085-
086-095>097.

&&

DISCUSSION...Small
AVIATION...Small
CLIMATE...Small

Hazardous Weather Outlook
National Weather Service Des Moines IA
504 AM CDT Tue Jun 14 2022

IAZ004>007-015>017-023>028-033>039-044>050-057>061-070>074-
081>084-092>094-151015-
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-Cass-
Adair-Madison-Warren-Marion-Adams-Union-Clarke-Lucas-Taylor-
Ringgold-Decatur-
504 AM CDT Tue Jun 14 2022

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

A Heat Advisory is in effect for the area. For more details,
please visit https://www.weather.gov/dmx.

Gusty south to southwest winds expected today with a brief period
of 40-45 mph gusts possible this morning, especially west.

Thunderstorms return to the region this evening into the
overnight hours Wednesday. There is some potential for severe
weather with large hail and damaging wind gusts the primary
threats. Locally heavy rainfall is also possible.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Thunderstorm chances, some strong to severe, continue into
Wednesday morning.

Additional thunderstorms, some severe, are possible Wednesday
afternoon and evening.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed tonight and tomorrow.

IAZ062-075-085-086-095>097-151015-
Poweshiek-Mahaska-Monroe-Wapello-Wayne-Appanoose-Davis-
504 AM CDT Tue Jun 14 2022

This Hazardous Weather Outlook is for portions of central Iowa.

.DAY ONE...Today and tonight

A Heat Advisory is in effect for the area. For more details,
please visit https://www.weather.gov/dmx.

Gusty south to southwest winds expected today with a brief period
of 30-35 mph gusts possible this morning.

Thunderstorms return to the region this evening into the
overnight hours Wednesday. There is some potential for severe
weather with large hail and damaging wind gusts the primary
threats. Locally heavy rainfall is also possible.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

A Heat Advisory is in effect for the area Wednesday. For more
details, please visit https://www.weather.gov/dmx.

Thunderstorm chances, some strong to severe, continue into
Wednesday morning.

Additional thunderstorms, some severe, are possible Wednesday
afternoon and evening.

.SPOTTER INFORMATION STATEMENT...

Spotters may be needed tonight and tomorrow.