SPC Mesoscale Discussion
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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SPC MD 1210
MD 1210 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR THE BIG BEND REGION OF FLORIDA INTO FAR SOUTHERN GEORGIA
Mesoscale Discussion 1210
NWS Storm Prediction Center Norman OK
1242 PM CDT Sat Jun 20 2026
Areas affected...The Big Bend region of Florida into far southern
Georgia
Concerning...Severe potential...Watch unlikely
Valid 201742Z - 201945Z
Probability of Watch Issuance...5 percent
SUMMARY...A localized corridor of higher wind potential may be
emerging across the Big Bend region of Florida and into adjacent
portions of far southern Georgia. Watch issuance is not expected.
DISCUSSION...Recent GOES IR imagery shows steady deepening of
incipient convection to the west of Tallahassee, FL that has
developed within a weak low-level confluence zone. This activity may
be influenced by a weak MCV noted in visible imagery and regional
VWP observations across extreme southwest GA. Over the past hour,
the KTLH VWP has shown a slight increase in 6 km winds that is
supporting some hodograph elongation as the MCV passes to the north.
Consequently, it appears plausible that a loosely organized
convective band may emerge over the next 1-2 hours across the Big
Bend region as convection continues to intensify. Further warming of
the downstream environment will likely yield low-level lapse rates
on the order of 7-8 C/km that should support some potential for
damaging wind gusts over the next few hours. Despite this potential,
the modest kinematic environment and a pocket of drier, less buoyant
air far downstream across northern FL will likely limit the overall
intensity, duration, and spatial extent of this threat and negate
the need for watch issuance.
..Moore/Hart.. 06/20/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...JAX...TAE...
LAT...LON 29738470 30078479 30278494 30428500 30578495 30648476
30768283 30698258 30558243 30318246 29988258 29718287
29658298 29608338 29878365 29998385 30068406 30038422
29898439 29738470
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SPC MD 1209
MD 1209 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR EASTERN FLORIDA PENINSULA
Mesoscale Discussion 1209
NWS Storm Prediction Center Norman OK
1206 PM CDT Sat Jun 20 2026
Areas affected...Eastern Florida Peninsula
Concerning...Severe potential...Watch unlikely
Valid 201706Z - 201930Z
Probability of Watch Issuance...5 percent
SUMMARY...Sporadic damaging wind gusts associated with wet
downbursts will be possible through late afternoon. This threat will
remain sufficiently isolated and transient to negate the need for a
watch.
DISCUSSION...Thunderstorm initiation has been well underway over the
past hour per regional radar and GOES imagery. Minimal capping
within a very moist environment, combined with weak ascent along a
subtle confluence axis, has resulted in convective initiation
slightly earlier than anticipated by most 12z solutions. Despite
around 2000 J/kg MLCAPE, negligible deep-layer wind shear will
promote mainly pulse convection and multi-cell clusters with several
outflow boundaries from this initial activity already apparent in
radar imagery. With surface temperatures still relatively early in
the diurnal heating cycle, low-level thermodynamic conditions
(primarily low-level lapse rates) are currently not optimal to
support a more robust downburst threat. However, continued heating
through the afternoon should yield pockets of higher MLCAPE and
steeper low-level lapse rates that should favor a greater potential
for strong to severe downbursts as convection spreads
east/southeast. Based on latest radar/satellite trends, this appears
most likely along the east-central to southeastern FL Peninsula.
Regardless, the overall severe wind risk will likely remain fairly
isolated and transient.
..Moore/Hart.. 06/20/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...MFL...MLB...TBW...
LAT...LON 25408019 25448049 25678077 26148116 26788136 27768181
28088188 28538174 28778154 28858108 28858073 28438045
28178045 27848037 27408018 27098007 26837999 26638000
25718007 25408019
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
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