Alert archive / Iowa / Mesoscale Discussions in 2022

Mesoscale Discussion 1663

August 7, 20227 counties in Iowa

The Storm Prediction Center issued this mesoscale discussion at Aug 7, 2022, 2:08 PM CDT for 7 counties in Iowa. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued
Aug 7, 2022, 2:08 PM CDT (19:08 UTC)
Expired
Aug 7, 2022, 4:15 PM CDT
In force
2 hr
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch unlikely
Chance of a watch
20%

Counties Boone County, IA, Calhoun County, IA, Carroll County, IA, Greene County, IA, Pocahontas County, IA, Sac County, IA, Webster County, IA

The radar

The Des Moines radar (KDMX), 112 km from the middle of the area, began a volume at 19:09 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 12:00Z, 7.1 hours before the alert went out and 176 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 12:00Z on 2022-08-07Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 438 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, Omaha, NE at 12:00Z on 2022-08-07The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 182 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
438 J/kg
Mixed-layer CIN
-301 J/kg
Mixed-layer LCL
1361 m above ground
0-6 km bulk shear
27 kt
0-1 km storm-relative helicity
182 m²/s²
0-3 km storm-relative helicity
198 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.0

Open this sounding in Storm Lab

The text

As transmitted.

407 
ACUS11 KWNS 071908
SWOMCD
SPC MCD 071908 
IAZ000-072115-

Mesoscale Discussion 1663
NWS Storm Prediction Center Norman OK
0208 PM CDT Sun Aug 07 2022

Areas affected...northwest IA

Concerning...Severe potential...Watch unlikely 

Valid 071908Z - 072115Z

Probability of Watch Issuance...20 percent

SUMMARY...Transient storm-scale rotation possible if storms can
become surface based this afternoon.  A brief tornado is possible.

DISCUSSION...Subjective mesoanalysis shows an area of weak
southeasterly surface flow over northwest IA to the southeast of a
surface front draped from southwest to northeast across the middle
MO Valley.  Temperatures have warmed to around 80 deg with mid 70s
degree F dewpoints.  Forecast soundings (NAM, RAP) show some
enlargement in the low-level hodograph with a very moist boundary
layer (17 g/kg lowest 100 mb mean mixing ratio).  The Des Moines 88D
VAD shows a veering and strengthening wind profile with height from
the surface through 3-4 km, largely validating the forecast sounding
prognostication.  It remains unclear whether one or two storms will
root into the boundary layer and become surface based over the next
1-2 hours.  If this occurs, the potential for a transient supercell
will probably increase and a localized risk for a brief tornado.

..Smith/Hart.. 08/07/2022

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

ATTN...WFO...DMX...FSD...

LAT...LON   42569543 42769495 42679385 42299368 41919402 42019530
            42229554 42569543

Nearby

Mesoscale Discussions in Iowa, 2022Every mesoscale discussion in 2022

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.