Alert archive / Nebraska / Mesoscale Discussions in 2021

Mesoscale Discussion 1398

July 30, 20218 counties in Iowa; Atchison County, Missouri; 11 counties in Nebraska

The Storm Prediction Center issued this mesoscale discussion at Jul 30, 2021, 8:16 PM CDT for 8 counties in Iowa; Atchison County, Missouri; 11 counties in Nebraska. It was in force for 59 min.

The area

The outline as issued.

The facts

Issued
Jul 30, 2021, 8:16 PM CDT (01:16 UTC)
Expired
Jul 30, 2021, 9:15 PM CDT
In force
59 min
Issued by
the Storm Prediction Center
Concerning
Severe potential...watch possible
Chance of a watch
60%

Counties Adams County, IA, Cass County, IA, Fremont County, IA, Mills County, IA, Montgomery County, IA, Page County, IA, Pottawattamie County, IA, Taylor County, IA, Atchison County, MO, Cass County, NE, Douglas County, NE, Gage County, NE, Johnson County, NE, Lancaster County, NE, Nemaha County, NE, Otoe County, NE, Saline County, NE, Sarpy County, NE, Saunders County, NE, Seward County, NE

The radar

The Omaha radar (KOAX), 59 km from the middle of the area, began a volume at 01:15 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Omaha, NE (KOAX), launched 00:00Z, 1.3 hours before the alert went out and 59 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 2021-07-31Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 2669 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 00:00Z on 2021-07-31The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 52 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
2669 J/kg
Mixed-layer CIN
-3 J/kg
Mixed-layer LCL
967 m above ground
0-6 km bulk shear
40 kt
0-1 km storm-relative helicity
52 m²/s²
0-3 km storm-relative helicity
279 m²/s²
Significant tornado parameter
3.4
Supercell composite
19.5

Open this sounding in Storm Lab

The text

As transmitted.

838 
ACUS11 KWNS 310117
SWOMCD
SPC MCD 310116 
IAZ000-MOZ000-NEZ000-310215-

Mesoscale Discussion 1398
NWS Storm Prediction Center Norman OK
0816 PM CDT Fri Jul 30 2021

Areas affected...Southeast NE...Southwest IA...Northwest MO

Concerning...Severe potential...Watch possible 

Valid 310116Z - 310215Z

Probability of Watch Issuance...60 percent

SUMMARY...Severe threat is increasing across parts of the
Mid-Missouri Valley.

DISCUSSION...Remnants of early-day MCS that formed over SD have
progressed southeast and new convection is intensifying along the
southwestern flank of this activity across southwestern IA. A bit
farther west, latest satellite imagery depicts a strengthening
supercell just northeast of LNK, per expanding anvil and overshoot.
00z sounding from OAX exhibited 40kt surface-6km bulk shear with
substantial turning in the lowest 6km. Over the next few hours LLJ
should strengthen across southeast NE into southwest IA. This could
aid upscale growth along the cool side of the boundary. This
activity should propagate south-southeast at only 10-15kt and a new
watch is being considered.

..Darrow/Goss.. 07/31/2021

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

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

LAT...LON   41279711 41549493 40699440 40269519 40179664 40609729
            41279711

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Jul 30, 8:47 PM CDTSevere Thunderstorm WatchSPCAdams, Decatur, Fremont, Mills, Montgomery, Page and 4 more5 hr
Jul 31, 1:06 PM CDTMesoscale DiscussionSPCAllamakee, Bremer, Chickasaw, Clayton, Fayette, Howard and 2 more2 hr
Jul 30, 11:05 PM CDTMesoscale DiscussionSPCAndrew, Daviess, DeKalb, Gentry, Harrison, Holt and 2 more85 min
Jul 30, 11:09 PM CDTMesoscale DiscussionSPCAndrew, Daviess, DeKalb, Gentry, Harrison, Holt and 2 more96 min
Jul 31, 12:54 AM CDTMesoscale DiscussionSPCAndrew, Buchanan, Caldwell, Carroll, Chariton, Clay and 16 more66 min
Jul 31, 11:00 AM CDTMesoscale DiscussionSPCBollinger, Butler, Cape Girardeau, Carter, Dent, Howell and 16 more2 hr
Jul 31, 5:09 PM CDTMesoscale DiscussionSPCBarton, Bates, Bollinger, Butler, Camden, Carter and 37 more2 hr
Jul 30, 9:36 PM CDTMesoscale DiscussionSPCBrown, Garfield, Loup, Rock24 min
Jul 30, 9:46 PM CDTSevere Thunderstorm WatchSPCAntelope, Blaine, Boone, Brown, Garfield, Greeley and 8 more4 hr

Nearby

Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in Iowa, 2021Mesoscale Discussions in Missouri, 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.