Mesoscale Discussion 1143

Issued

Jul 3, 2021, 1:53 PM MDT (19:53 UTC)

Expired

Jul 3, 2021, 3:30 PM MDT

In force

97 min

Issued by

the Storm Prediction Center

Concerning

Severe potential...watch possible

Chance of a watch

40%

Counties Lincoln County, CO, Logan County, CO, Morgan County, CO, Phillips County, CO, Sedgwick County, CO, Washington County, CO, Banner County, NE, Box Butte County, NE, Cheyenne County, NE, Dawes County, NE, Deuel County, NE, Garden County, NE, Grant County, NE, Kimball County, NE, Morrill County, NE, Scotts Bluff County, NE, Sheridan County, NE

The Cheyenne radar (KCYS), 164 km from the middle of the area, began a volume at 19:55 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.

• Severe Thunderstorm Watch 332Jul 3, 3:35 PM MDT

656 
ACUS11 KWNS 031954
SWOMCD
SPC MCD 031953 
NEZ000-COZ000-032130-

Mesoscale Discussion 1143
NWS Storm Prediction Center Norman OK
0253 PM CDT Sat Jul 03 2021

Areas affected...Central High Plains

Concerning...Severe potential...Watch possible 

Valid 031953Z - 032130Z

Probability of Watch Issuance...40 percent

SUMMARY...Scattered strong/severe thunderstorms are expected to
develop across the High Plains this afternoon/evening. A few storms
may produce damaging wind gusts or severe hail. Convective trends
will be monitored for a possible weather watch.

DISCUSSION...As of 1930 UTC, afternoon visible satellite imagery
showed deepening cumulus/thunderstorms developing across the High
Plains of Colorado, Nebraska, and Wyoming beneath a weak upper level
trough. SPC mesoanalysis indicates that remaining inhibition will
likely dissipate within the next hour or two, as convective
temperatures are breached. Regional observations show temperatures
well into the 80s to near 90 F, with surface dewpoints ranging from
the mid 50s to low 60s F. The warming surface temperatures, weak
upslope flow, and mid-level lapse rates between 7.5 and 8.5 C/km are
supporting moderate MLCAPE of 1500 to 2000 J/kg. 

Mid-level flow remains quite weak owing to the diffuse upper air
pattern. As a result, vertical shear is lacking, with regional VWPs
only sampling 20-25 kts of effective shear. This should limit storms
to a multicellular storm mode through this afternoon. Given the
degree of buoyancy and steepening low and mid-level lapse rates, a
few stronger storm clusters may produce damaging wind gusts or
severe hail. As storms track south and east this evening, slightly
greater vertical shear will likely develop with the nocturnal
low-level jet. A more organized cluster or weak MCS may evolve
across portions of eastern Colorado and western Kansas with a risk
for damaging wind gusts. 

The degree of the severe threat and the need for a watch remains
uncertain with storms exhibiting limited organization thus far. CAM
guidance suggests some clustering may develop by 21-22z as outflow
from additional development coalescence. Should the severe threat
increase, a weather watch could be needed.

..Lyons/Guyer.. 07/03/2021

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

ATTN...WFO...LBF...GLD...PUB...BOU...CYS...

LAT...LON   40760230 39130266 38560304 38430338 38870391 39520405
            40070409 41670401 42610355 42900260 42890185 42600156
            42030162 40760230

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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.