MD 2059 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF SOUTHEASTERN SOUTH DAKOTA TO THE NEBRASKA AND IOWA BORDERS
Mesoscale Discussion 2059
NWS Storm Prediction Center Norman OK
0713 PM CDT Thu Aug 20 2026
Areas affected...portions of southeastern South Dakota to the
Nebraska and Iowa borders
Concerning...Severe potential...Watch possible
Valid 210013Z - 210115Z
Probability of Watch Issuance...40 percent
SUMMARY...An isolated severe hail threat will persist for a few more
hours. However, storms will move into stronger MLCINH, which may
limit the spatial and temporal extent of the severe threat.
DISCUSSION...Multiple splitting supercells have developed over the
last couple of hours, with an instance of golfball hail recently
reported on a storm in Minnehaha County, SD. These storms are
benefiting from 3000+ J/kg MLCAPE and 50 kts of effective bulk shear
in place. Nonetheless, these storms are also approaching a region of
appreciable MLCINH. The current thinking is that these storms should
gradually weaken as they move off of the surface trough/boundary and
move into the inhibition. As such, while a few more instances of
severe hail could occur, the severe threat should remain confined
along the surface trough for just a few more hours.
..Squitieri/Guyer.. 08/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FSD...OAX...LBF...
LAT...LON 42619823 42829877 42999891 43109886 43149818 43279774
43529727 43839692 43899669 43889644 43849622 43709612
43249616 42859627 42639654 42579705 42619823
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
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MD 2058 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF SOUTHEAST OK...SOUTHWEST AR...AND FAR NORTHEAST TX
Mesoscale Discussion 2058
NWS Storm Prediction Center Norman OK
0607 PM CDT Thu Aug 20 2026
Areas affected...Parts of southeast OK...southwest AR...and far
northeast TX
Concerning...Severe potential...Watch unlikely
Valid 202307Z - 210130Z
Probability of Watch Issuance...20 percent
SUMMARY...Thunderstorms will be capable of producing strong to
locally damaging wind gusts for the next few hours. A watch is not
currently expected, though convective trends are being monitored.
DISCUSSION...Thunderstorms are increasing in coverage along a
stationary boundary draped across southeast OK and southwest AR.
Along/south of the boundary, temperatures have warmed to near 105 F
amid lower/middle 60s dewpoints -- resulting in a strongly unstable
air mass. This activity is largely displaced from a midlevel trough
and enhanced flow aloft moving across the lower OH Valley, which
should tend to reduce overall convective organization. Nevertheless,
around 25 kt of midlevel northwesterly flow oriented perpendicular
to the stationary boundary and evolving cluster of storms could
support a loosely organized cluster capable of producing locally
damaging wind gusts for the next few hours.
..Weinman/Guyer.. 08/20/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LZK...SHV...TSA...FWD...
LAT...LON 33729526 34039560 34349570 34669553 34799505 34629348
34429306 34089284 33579283 33249314 33179369 33299431
33729526
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
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MD 2056 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR PORTIONS OF CENTRAL INTO SOUTHWESTERN MINNESOTA AND FAR EASTERN SOUTH DAKOTA
Mesoscale Discussion 2056
NWS Storm Prediction Center Norman OK
0531 PM CDT Thu Aug 20 2026
Areas affected...portions of central into southwestern Minnesota and
far eastern South Dakota
Concerning...Severe potential...Watch possible
Valid 202231Z - 210030Z
Probability of Watch Issuance...60 percent
SUMMARY...The risk for severe hail will increase through the evening
hours as storms gradually develop through the evening. A few severe
gusts and a tornado or two may also occur. Timing of storm
development is uncertain, but convective trends will be closely
monitored for the need of a WW issuance.
DISCUSSION...A few discrete storms have developed and sustained
themselves along a surface trough over northern MN, where MRMS MESH
depicts some hail potentially falling with these storms. As the
surface trough continues to move southeast, storms should gradually
increase in coverage and intensity, especially after 0Z. Surface
temperatures approaching 80 F, amid mid 60s F dewpoints and 7-8 C/km
boundary-layer lapse rates, is yielding over 2000 J/kg MLCAPE.
Furthermore, increased southwesterly 850 mb flow beneath modest 500
mb westerlies is contributing to 40 kts of effective bulk shear,
especially over central and southern MN. Currently, the MPX VAD
shows a modestly curved and elongated hodograph, supportive of
supercell structures. The current thinking is that any storm that
can mature and sustain itself in this environment will become
supercellular, accompanied by a severe hail threat (some potentially
exceeding 2 inches in diameter). A few severe gusts may also occur,
and given the appreciable low-level hodograph, a tornado or two
cannot be rule out either.
Visible satellite shows an overall lack of agitated CU, with several
billow clouds remaining (indicative of some residual stability). It
is thus unclear when convective initiation and the subsequent need
for a WW issuance will occur. Given the favorable ambient
environment though, convective trends will be closely monitored.
..Squitieri/Guyer.. 08/20/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DLH...MPX...FGF...FSD...ABR...
LAT...LON 43719738 45259588 46249498 46669442 46899402 46919341
46689310 46059276 45309267 44639294 44129357 43669477
43429560 43389667 43719738
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
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