Mesoscale Discussion 755

Issued

May 26, 2021, 4:44 PM MDT (22:44 UTC)

Expired

May 26, 2021, 6:45 PM MDT

In force

2 hr

Issued by

the Storm Prediction Center

Concerning

Tornado watch 209...210

The Goodland radar (KGLD), 124 km from the middle of the area, began a volume at 22:43 UTC, the scan nearest the moment this went out.

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• Severe Thunderstorm Watch 212May 26, 5:05 PM MDT

476 
ACUS11 KWNS 262245
SWOMCD
SPC MCD 262244 
KSZ000-NEZ000-COZ000-270045-

Mesoscale Discussion 0755
NWS Storm Prediction Center Norman OK
0544 PM CDT Wed May 26 2021

Areas affected...Parts of northeastern Colorado...southwestern
Nebraska...northwestern and north central Kansas

Concerning...Tornado Watch 209...210...

Valid 262244Z - 270045Z

The severe weather threat for Tornado Watch 209, 210 continues.

SUMMARY...Increasing and intensifying thunderstorm development into
the 7-9 PM CDT time frame.  This will probably continue to include a
few supercells with increasing tornadic potential, along with
potential for the evolution of organizing thunderstorm clusters. 
Areas to the east of the Tornado Watches will continue to monitored
for additional severe weather watches.

DISCUSSION...Although isolated to widely scattered thunderstorms are
now initiating along the dryline, a much more substantive increase
in thunderstorms is underway along a corridor from the Russell, KS
vicinity northwestward through the McCook and Scottsbluff areas of
western Nebraska.  This appears focused within a broad zone of
lower/mid tropospheric warm advection, northeast of somewhat warmer
and more strongly capping elevated mixed-layer air (as inferred from
700 mb thermal fields).

Storms near Russell also appear focused near a zone of locally
enhanced boundary-layer convergence, near the eastern periphery of a
20-30 kt southerly 850 mb jet, which is forecast to strengthen to 40
kt this evening.  While there may be a tendency for this convection
to begin to advect eastward, in the presence of 20-30 kt
west-southwesterly ambient deep-layer mean flow, until the low-level
jet begins to veer later this evening, strong storm development
probably will remain focused near/west-northwest of the Russell
vicinity.

Otherwise, a general increase and intensification of thunderstorm
activity probably will continue across parts of the Nebraska
Panhandle and southwestern into south central Nebraska through
00-02Z, with a tendency for activity to advect east/northeast of the
Tornado Watch area.  However, strongest storms, including discrete
supercells and upscale growing clusters, probably will remain
focused near the edge of the warmer/more strongly capping elevated
mixed-layer air, where the more moist and strongly heated
boundary-layer is characterized by large CAPE (up to 3000 J/kg).  

As the southerly low-level jet begins to strengthen by early
evening, the risk for tornadoes in discrete supercells will probably
continue to increase, include potential for a couple of strong
tornadoes.

..Kerr.. 05/26/2021

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

ATTN...WFO...TOP...ICT...GID...LBF...DDC...GLD...BOU...CYS...

LAT...LON   41500332 41890128 40199887 39159704 38459875 38990054
            40200205 40930315 41500332

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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.