Alert archive / Iowa / Severe Thunderstorm Warnings in 2020

Severe Thunderstorm Warning 98, NWS Omaha, NE

June 26, 2020Mills County, Montgomery County, Pottawattamie County, Iowa

NWS Omaha, NE issued this severe thunderstorm warning at Jun 26, 2020, 6:32 PM CDT for Mills County, Montgomery County, Pottawattamie County, Iowa. It was in force for 28 min. No storm report in the archive falls inside the area while it was in force.

The area

The counties it named.

The facts

Issued
Jun 26, 2020, 6:32 PM CDT (23:32 UTC)
Expired
Jun 26, 2020, 7:00 PM CDT
In force
28 min
Issued by
NWS Omaha, NE
Area
Storm-based polygon
Hail
1.0 in
Wind
50.0 mph

Counties Mills County, IA, Montgomery County, IA, Pottawattamie County, IA

The radar

The Omaha radar (KOAX), 80 km from the middle of the area, began a volume at 23:31 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Topeka, KS (KTOP), launched 12:00Z, 11.5 hours before the alert went out and 238 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Topeka, KS at 12:00Z on 2020-06-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 113 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Topeka, KS at 12:00Z on 2020-06-26The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 153 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
113 J/kg
Mixed-layer CIN
-475 J/kg
Mixed-layer LCL
1770 m above ground
0-6 km bulk shear
29 kt
0-1 km storm-relative helicity
153 m²/s²
0-3 km storm-relative helicity
119 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

What forecasters said that day

The local office's own words before this severe thunderstorm warning went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Omaha, NE wrote its last area forecast discussion before this severe thunderstorm warning went out at Jun 26, 6:19 PM CDT, 13 minutes earlier.

Area forecast discussion, Jun 26, 6:19 PM CDT, 13 minutes before
Area Forecast Discussion
National Weather Service Omaha/Valley NE
619 PM CDT Fri Jun 26 2020

...Updated Aviation Forecast Discussion...

.DISCUSSION...
Issued at 236 PM CDT Fri Jun 26 2020

Weak frontal boundary at 2 pm was located just south of Lincoln
extending east to near Plattsmouth, then northeast toward
Atlantic. A few showers/sprinkles had developed along the front
before noon, and this trend continues into mid afternoon. No
lightning has been observed thus far. The boundary will continue
to be the focus for a few showers, and possible thunderstorms late
this afternoon as the front continues to slowly move toward the
NE/KS border by mid to late evening. CAMs suggest a storm or two
may pop along the front by about 5-7 pm, with scattered coverage
through the remainder of the evening. All of this activity will
be south of I80, with areas to the north likely remaining dry
tonight. SPC has our southern forecast area in a slight risk for
wind and hail and this seems reasonable. After midnight, there
remains a threat for scattered storms across southeast NE and
southwest IA. And again, some of these overnight storms could have
some hail, and it's possible that a few locations get more than
one or two storms, thus locally heavy rainfall will also be
possible, but flooding is not expected.

Previous forecasts indicated that Saturday would be mainly dry,
but models now appear to be latching onto a weak wave moving out
of the central Rockies. This is also what may help to energize the
overnight activity, but this wave could also still be present
Saturday, to at least bring a slight chance of showers/storms
along and east of the Missouri River.

Meanwhile, another upper wave moving out of the Rockies could
bring more storm chances to the area Saturday night into Sunday.
This may help push the previously mentioned frontal boundary
north, and thus there's at least a marginal risk of a stronger
storm south of I80 Saturday night as indicated by a few of the
CAMs, but confidence is not great.

After upper 80s on Saturday, highs head back into the lower 90s
probably through at least Wednesday. With dewpoints heading back
into the lower 70s, afternoon heat index values increase to 96 to
103, and while not hot enough for a heat advisory, we're probably
looking at several very muggy days with uncomfortable humidity.
There will also be occasional shower/storm chances in there, and
while continuous rain isn't expected, there will be at least a
daily 20-40% chance somewhere in our forecast every day next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 617 PM CDT Fri Jun 26 2020

VFR conditions will prevail for the TAF period. Rain and a
possible thunderstorm may pop up in the vicinity of KLNK but
should not impact the terminal. A weak frontal boundary has passed
through the area and may retreat northward. Due to this, winds
will be light and variable for most of the TAF period.

&&

.OAX WATCHES/WARNINGS/ADVISORIES...
NE...None.
IA...None.
&&

DISCUSSION...DeWald
AVIATION...Fajman
Hazardous weather outlook, Jun 26, 3:32 PM CDT, 3 hours before
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The office that day

Everything else NWS Omaha, NE issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jun 25, 11:18 PM CDTSpecial Weather StatementOAXKnox27 min
Jun 26, 6:56 PM CDTSevere Thunderstorm WarningOAXMontgomery, Pottawattamie20 min

Nearby

Severe Thunderstorm Warnings in Iowa, 2020Every severe thunderstorm warning in 2020

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.