Mesoscale Discussion 1099

Issued

Jun 25, 2021, 4:54 PM MDT (22:54 UTC)

Expired

Jun 25, 2021, 6:00 PM MDT

In force

66 min

Issued by

the Storm Prediction Center

Concerning

Severe thunderstorm watch 316

The Goodland radar (KGLD), 149 km from the middle of the area, began a volume at 22:54 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.

791 
ACUS11 KWNS 252254
SWOMCD
SPC MCD 252254 
NEZ000-KSZ000-COZ000-260000-

Mesoscale Discussion 1099
NWS Storm Prediction Center Norman OK
0554 PM CDT Fri Jun 25 2021

Areas affected...northeast Colorado...northwest Kansas...and central
Nebraska

Concerning...Severe Thunderstorm Watch 316...

Valid 252254Z - 260000Z

The severe weather threat for Severe Thunderstorm Watch 316
continues.

SUMMARY...Thunderstorms continue across many portions of Severe
Thunderstorm Watch 316. The main threats this evening will be hail
and strong, gusty thunderstorm winds. The overall severe threat
should diminish later this evening with the loss of diurnal heating.

DISCUSSION...Several areas of thunderstorms are ongoing across the
Severe Thunderstorm Watch: one in northeast Colorado, one across
central Nebraska, and across northwest Kansas.

Across central Nebraska, discrete thunderstorms are ongoing along a
convergence zone associated with, and to the south of, a remnant MCV
over north-central Nebraska. Despite weak lapse rates, a warm, moist
boundary layer across the region has allowed surface-based CAPE to
increase to in excess of 2000 J/kg ahead of the ongoing
thunderstorms. Given the degree of instability, coupled with
deep-layer shear around 40 knots, thunderstorms may continue to pose
a severe threat through the evening. Hail and gusty thunderstorm
winds would be the main threats. The threat should lessen with time
this evening as diurnal heating and boundary-layer decoupling reduce
surface-based CAPE and the weakening of the convergence zone limits
forcing for ascent.

Across northeast Colorado, several areas of linear thunderstorms
continue to move broadly east toward western Kansas. The strongest
such storms are currently moving northeast through Cheyenne County,
Colorado. Additional thunderstorms are moving southeast across Yuma
County, Colorado, and will enter northwest Kansas shortly.
Instability here is less than areas farther east given a drying of
the lower levels. Consequently, however, greater
temperature-dewpoint spreads should allow for at least some risk for
strong, gusty thunderstorm outflows. This threat should continue for
a few more hours before generally weakening later this evening with
cooling/decoupling of the boundary layer.

Across northwest Kansas, thunderstorms have recently developed out
of the persistent cumulus field associated with a weak convergence
zone that is apparent on KGLD radar. Here, low-level moisture is
greater than areas farther east. The result is surface-based
instability between 1500 and 2000 J/kg. However, effective-layer
shear is less than across Nebraska given the lessening influence of
the aforementioned MCV. Current expectation is that these
thunderstorms should move very little this afternoon until being
impinged upon by the outflow associated with the thunderstorms
moving out of Colorado. Given the degree of instability, gusty
thunderstorm outflows and hail will be possible with the strongest
thunderstorms. This threat should diminish with time this evening.

..Marsh.. 06/25/2021

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

ATTN...WFO...OAX...TOP...GID...LBF...DDC...GLD...PUB...BOU...

LAT...LON   38540405 38860403 38860372 40020369 40000346 40440345
            40440202 40360204 40360134 40700132 40710122 41390125
            41420024 41740023 41749830 41929828 41919781 42119783
            42089736 41769738 41769725 41389723 41459689 41049689
            41049735 40009736 39999791 39589794 39569903 39139905
            39120014 38700013 38690113 38290113 38260204 38620204
            38600317 38520317 38540405

Mesoscale Discussions in Nebraska, 2021Mesoscale Discussions in Kansas, 2021Mesoscale Discussions in Colorado, 2021Every mesoscale discussion in 2021

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.