Alert archive / Iowa / Mesoscale Discussions in 2021

Mesoscale Discussion 740

May 25, 202113 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at May 25, 2021, 7:40 PM CDT for 13 counties in Iowa. It was in force for 95 min.

The area

The outline as issued.

The facts

Issued
May 25, 2021, 7:40 PM CDT (00:40 UTC)
Expired
May 25, 2021, 9:15 PM CDT
In force
95 min
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch unlikely
Chance of a watch
5%

Counties Adair County, IA, Adams County, IA, Audubon County, IA, Boone County, IA, Cass County, IA, Dallas County, IA, Greene County, IA, Guthrie County, IA, Hamilton County, IA, Madison County, IA, Montgomery County, IA, Polk County, IA, Story County, IA

The radar

The Des Moines radar (KDMX), 56 km from the middle of the area, began a volume at 00:41 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

Omaha, NE (KOAX), launched 00:00Z, 0.7 hours before the alert went out and 170 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, Omaha, NE at 00:00Z on 2021-05-26Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 228 joules per kilogram.LCLEL10008507005003002001001 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, Omaha, NE at 00:00Z on 2021-05-26The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 36 square meters per square second.1939587897Sfc1 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
228 J/kg
Mixed-layer CIN
-6 J/kg
Mixed-layer LCL
2355 m above ground
0-6 km bulk shear
29 kt
0-1 km storm-relative helicity
36 m²/s²
0-3 km storm-relative helicity
53 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.5

Open this sounding in Storm Lab

The text

As transmitted.

728 
ACUS11 KWNS 260040
SWOMCD
SPC MCD 260040 
IAZ000-260215-

Mesoscale Discussion 0740
NWS Storm Prediction Center Norman OK
0740 PM CDT Tue May 25 2021

Areas affected...Central Iowa

Concerning...Severe potential...Watch unlikely 

Valid 260040Z - 260215Z

Probability of Watch Issuance...5 percent

SUMMARY...Isolated, marginally severe hail and wind gusts may occur
with weakly organized supercell storms in central Iowa. No WW is
expected as this activity should diminish in an hour or two.

DISCUSSION...Marginal supercell storms have developed along the cold
front moving into central Iowa. Around 1500 J/kg MLCAPE and 25 kts
of effective shear has supported this weak organization. A storm
near the Guthrie/Dallas County line has shown the most organization
so far and would be the greatest short-term threat for marginally
severe hail and a strong wind gust. With temperatures starting to
decrease in the region, the longevity of this activity is not likely
to be more than another hour or two. No WW is expected.

..Wendt.. 05/26/2021

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...DMX...OAX...

LAT...LON   41319537 41999466 42579396 42549343 41979337 41719350
            41489362 41299400 40959468 40989513 41099535 41319537

Nearby

Mesoscale Discussions in Iowa, 2021Every mesoscale discussion in 2021

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.