Mesoscale Discussion 1800
NWS Storm Prediction Center Norman OK
1140 PM CDT Wed Jul 29 2026
Areas affected...much of central South Dakota...north central
Nebraska
Concerning...Severe potential...Watch unlikely
Valid 300440Z - 300645Z
Probability of Watch Issuance...5 percent
SUMMARY...Ongoing cluster of thunderstorms may be slow to weaken,
but associated strong to severe wind gusts probably will diminish
through 1-3 AM CDT.
DISCUSSION...Beneath mid/upper ridging, weakly sheared,
southwesterly deep-layer mean flow on the order of 10-15 kt prevails
across much of the middle Missouri Valley. However, forcing for
ascent along the leading edge of the surface cold pool associated
with consolidating outflows has been sufficient to maintain vigorous
thunderstorm development east of the Black Hills into central South
Dakota the past few hours. This, and an associated increase in
strong to severe surface gusts, probably has been supported by a
nocturnally strengthening boundary-layer jet (up to around 30 kt
below 850 mb), near a weak surface low migrating across the Pierre
vicinity.
Despite the loss of daytime heating, moistening southeasterly
near-surface flow ahead of activity across central South Dakota has
been maintaining, or even contributing to a subtle increase in,
potential instability. Whether this is enough to maintain
convection supportive of continuing strong to severe surface gusts
remains somewhat unclear. 04Z surface observations still indicate
2-hourly pressure rises on the order of 2-6+ mb within the cold
pool. However, most recent radar, satellite and lightning data
suggest that a more notable weakening trend in convective intensity
may now be underway. As activity advances into an environment with
progressively less steep mid-level lapse rates, and higher low-level
moisture content with reduced latent cooling potential, the risk for
severe wind gusts seems likely to diminish.
..Kerr/Smith.. 07/30/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...FSD...ABR...LBF...UNR...
LAT...LON 45350080 45229945 44139813 42929920 42260065 42770095
43590033 44140028 45050115 45350080
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
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