SPC MD 1213

MD 1213 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR NORTHERN UTAH INTO SOUTHEAST IDAHO

Mesoscale Discussion 1213
NWS Storm Prediction Center Norman OK
0233 PM CDT Sat Jun 20 2026

Areas affected...Northern Utah into southeast Idaho

Concerning...Severe potential...Watch unlikely 

Valid 201933Z - 202130Z

Probability of Watch Issuance...20 percent

SUMMARY...Isolated strong to severe downburst winds will be possible
through early evening across the northern Great Basin into far
southwest Wyoming. This threat should remain sufficiently isolated
to preclude watch issuance.

DISCUSSION...The early stages of thunderstorm initiation are ongoing
across northern NV and into adjacent portions of southern ID and
northwest UT. This activity is largely being driven by large-scale
ascent in proximity to a mid-level vorticity maximum evident in
recent water-vapor imagery, and is being aided by localized
orographic ascent within the higher terrain features. Across much of
northeast NV into UT/ID, temperatures are warming into the mid 70s
to low 80s with dewpoint depressions increasing into the 30-40 F
range, indicative of deep boundary-layer mixing. Recent RAP
mesoanalyses corroborate these observations and suggest 0-3 km lapse
rates are nearly dry adiabatic. 

While dry low-level conditions are limiting overall buoyancy, the
boundary-layer thermodynamic conditions are favorable for downdraft
accelerations capable of producing strong to severe downburst winds.
Additionally, 20-30 knots of bulk shear through the CAPE-bearing
layer should provide some storm longevity, further supporting the
potential for strong/severe winds. In general, thunderstorm coverage
should remain isolated to perhaps widely scattered, and the
downburst wind threat associated with any particular storm should
remain relatively transient (10-30 minutes). These factors limit
confidence in the need for a watch.

..Moore/Hart.. 06/20/2026

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

ATTN...WFO...RIW...SLC...PIH...BOI...LKN...

LAT...LON   41531057 41021089 40531174 40031345 39981385 40021433
            40441523 40811592 40871709 40931777 41061807 41201818
            41511820 41861812 42031794 42181770 42331727 42501398
            42661310 43191149 43181097 42971074 42511070 41531057 

MOST PROBABLE PEAK WIND GUST...55-70 MPH

SPC MD 1212

MD 1212 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR PARTS OF EASTERN COLORADO...SOUTHWESTERN NEBRASKA...WESTERN KANSAS

Mesoscale Discussion 1212
NWS Storm Prediction Center Norman OK
0211 PM CDT Sat Jun 20 2026

Areas affected...parts of eastern Colorado...southwestern
Nebraska...western Kansas

Concerning...Severe potential...Watch likely 

Valid 201911Z - 202115Z

Probability of Watch Issuance...80 percent

SUMMARY...Intensifying scattered thunderstorm development
increasingly probable by 2-4 PM MDT, with a few supercells evolving
thereafter.   This may be accompanied by increasing potential for a
couple of strong tornadoes, mainly in a corridor west through south
of the Imperial, NE vicinity toward early evening.

DISCUSSION...Beneath a plume of very warm (including 14-16 C+
temperatures around 700 mb) elevated mixed-layer advecting east of
the southern Rockies, a surface low is beginning to develop within
rapidly deepening surface troughing across eastern Colorado.  This
is coinciding with strong boundary heating and deep mixing, to the
south of a zone of strengthening differential surface heating
evolving to the north of the developing low, across parts of
northwestern Kansas into the southern slopes of the Cheyenne Ridge. 

Along and to the cooler side of this boundary, higher boundary-layer
moisture content and potential instability (including CAPE exceeding
2000 J/kg) are forecast to be maintained through the afternoon. 
Even to the south of this boundary, the more deeply mixed
boundary-layer is forecast to become characterized by modest (but
increasing across the plains toward the Kansas state border) CAPE,
as convective temperatures are approached later this afternoon.

Inhibition may remain strong along the zone of differential heating,
but forcing for ascent associated with focused low-level convergence
and warm advection may eventually contribute to isolated supercell
development.  In the presence of strengthening deep-layer and
low-level shear, this may be accompanied by increasing potential for
a strong tornado or two, in addition to large hail, by early
evening, if not earlier.

Otherwise, high-based convective development now underway across and
to the east of the higher terrain is expected to continue to spread
eastward across the plains and intensify, with scattered
thunderstorms increasingly probable by 20-22Z.  This will be
accompanied by increasing potential for large hail, locally damaging
wind gusts, and perhaps at least some risk for a couple of tornadoes
as well.

..Kerr/Hart.. 06/20/2026

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

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

LAT...LON   41060388 41090243 40420074 39400063 38270150 37160181
            37170326 37510356 38450320 39330408 40290403 41060388 

SPC MD 1211

MD 1211 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR WYOMING
        

Mesoscale Discussion 1211
NWS Storm Prediction Center Norman OK
0150 PM CDT Sat Jun 20 2026

Areas affected...Wyoming

Concerning...Severe potential...Watch possible 

Valid 201850Z - 202045Z

Probability of Watch Issuance...40 percent

SUMMARY...High-based thunderstorms capable of severe downburst winds
will spread across central and northeast Wyoming through the
afternoon. Trends are being monitored for the need for a watch
issuance, though thunderstorm coverage remains uncertain.

DISCUSSION...Over the past 1-2 hours, relatively shallow, but
high-based, convection has begun spreading across western WY with a
second region of storms more recently developing within the Wyoming
Basin/southern WY. Across both regions, clearing skies ahead of the
developing storms has allowed surface temperatures to warm into the
70s with dewpoints mixing into the mid to upper 30s. Based on recent
forecast guidance, these surface conditions suggest that the
boundary-layer has now fully mixed to around 3 to 3.5 km deep with
around 250-500 J/kg of MLCAPE. Although buoyancy is fairly meager,
the combination of a deeply mixed boundary layer and 30-35 knots of
effective shear should promote persistent convection capable of
producing strong to severe downburst winds. Latest CAM guidance
continues to depict this threat well and suggests swaths of 50-75
mph winds may emerge across central to northeast WY through the
early evening hours. 

The primary uncertainty in the short-term forecast is the lingering
cloud cover further downstream across central/northeast WY, which is
muting diurnal heating (temperatures remain in the 60s) and limiting
boundary-layer depth. Although this cloud cover is rapidly
progressing northeast, it is unclear if the window of mostly clear
skies will be sufficient to produce a deeply-mixed boundary layer
conducive for severe winds. Consequently, confidence in the severe
wind threat is greatest in the near-term, but some severe wind
threat may materialize further downstream through the evening if
sufficient heating can occur. Convective trends are being monitored,
and watch issuance may be needed.

..Moore/Hart.. 06/20/2026

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

ATTN...WFO...UNR...CYS...BYZ...RIW...

LAT...LON   41590803 41560864 41810917 42790999 43380985 43820942
            44730731 44770647 44650585 44370528 44010471 43560421
            43280411 43290414 42950408 42050407 41540430 41260460
            41160491 41210540 41490579 41700619 41790658 41750715
            41590803 

MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN


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