Mesoscale Discussion 2032
NWS Storm Prediction Center Norman OK
0854 PM CDT Tue Aug 18 2026

Areas affected...Parts of western/southwest SD

Concerning...Severe potential...Watch unlikely 

Valid 190154Z - 190330Z

Probability of Watch Issuance...20 percent

SUMMARY...An isolated severe hail/wind threat may continue this
evening. Watch issuance is unlikely.

DISCUSSION...A cell which formed earlier over the Black Hills in
western SD has recently intensified into a supercell while
approaching Rapid City. The 00Z UNR sounding showed relatively
modest instability (MUCAPE less than 1000 J/kg) and mid-level lapse
rates, but strong deep-layer shear around 50 kt. This ongoing
supercell should continue to pose a threat for severe hail in the
short term per recent MRMS MESH estimates. But, it remains unclear
whether it will be able to persist downstream of the higher terrain
of the Black Hills given increasing MLCIN with nocturnal cooling
occurring across southwest SD. Some short term guidance suggests a
small cluster may evolve over the next couple of hours, with some
increase in severe/damaging outflow winds possible if this occurs.
Regardless, the presence of weak instability and overall isolated
nature of the severe threat suggest that watch issuance is unlikely.

..Gleason.. 08/19/2026

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

ATTN...WFO...UNR...

LAT...LON   44100353 44470321 44110146 43350148 43080203 43180275
            43810362 44100353 

MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN

Mesoscale Discussion 2031
NWS Storm Prediction Center Norman OK
0746 PM CDT Tue Aug 18 2026

Areas affected...portions of northern and northeastern Kansas into
western Missouri

Concerning...Severe potential...Watch possible 

Valid 190046Z - 190315Z

Probability of Watch Issuance...60 percent

SUMMARY...Thunderstorms should increase through the evening and
early overnight hours, accompanied by a risk of severe hail and
perhaps a few severe gusts. If convective trends continue to
indicate an increase in storm coverage, a WW issuance may be needed.

DISCUSSION...Isolated thunderstorms are attempting to develop ahead
of a surface low, at the terminus region of a geostrophic low-level
flow regime. Here, 850 mb frontogenesis/convergence and warm-air
advection are maximized, likely resulting the intensifying storms.
Though the 00Z mesoanalysis depicts appreciable MLCINH over
northeast KS into western MO, isentropic lift should support the
increase in elevated convection above the inhibition layer, where
storms may take advantage of available instability (e.g. 7.5-9 C/km
mid-level lapse rates per 00Z regional observed soundings). 3000
J/kg MLCAPE amid 50 kts of effective bulk shear will support a mix
of multicells and supercells tonight, with severe hail and wind the
main threats. An instance or two of 2+ inch hail cannot be ruled
out. A WW issuance may be needed pending favorable trends in greater
storm coverage.

..Squitieri/Gleason.. 08/19/2026

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

ATTN...WFO...EAX...TOP...ICT...GID...

LAT...LON   39259832 39489729 39579572 39459427 39109349 38709350
            38469404 38449501 38459598 38539681 38609756 38709806
            39259832 

MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0800 PM CDT Tue Aug 18 2026

Valid 190100Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE CENTRAL PLAINS AND LOWER MISSOURI VALLEY...

...SUMMARY...
Thunderstorms with severe wind gusts and hail will be possible this
evening from parts of the central Plains into the lower Missouri
Valley. Isolated severe gusts and hail will also be possible in
parts of the central and northern High Plains, and from the Midwest
into the Great Lakes.

...Central Plains/Lower Missouri Valley...
The latest water vapor imagery shows west-northwesterly mid-level
flow over the central U.S. with a shortwave trough embedded in the
flow over western Kansas. At the surface, a moist airmass is located
from the mid Mississippi Valley westward into the central Plains,
where surface dewpoints are mostly from the upper 60s and lower 70s
F. Low-level convergence is maximized along and near a well-defined
outflow boundary located across central Kansas. Isolated severe
thunderstorms are ongoing near this boundary. In this area, moderate
deep-layer shear and steep low to mid-level lapse rates will be
favorable for isolated large hail and severe wind gusts over the
next few hours.

Further to the north across northern Kansas and southern Nebraska,
the RAP has strong instability analyzed with MLCAPE in the 3000 to 
3500 J/kg range. Thunderstorms are currently ongoing in western
Nebraska and northeastern Colorado. These storms will move toward
the stronger instability over the next few hours. As this happens,
the storms may increase in intensity. If this were to occur, the
strong instability and moderate deep-layer shear over northwest
Kansas and southwest Nebraska would support a threat for hail and
isolated severe wind gusts. A second severe threat area is expected
to become active further east from northeast Kansas into
west-central Missouri as low-level flow increases this evening.
Thunderstorms are now developing in north-central Kansas and this
convection should expand in coverage over the next couple of hours.
The primary threat would be wind damage, especially if a short
intense line segment can become organized. Along its path, severe
wind gusts could exceed 70 mph...see MCD 2031.
 
...Midwest/Great Lakes...
The latest water vapor imagery shows a distinct shortwave trough
over the mid Mississippi Valley within west-northwesterly flow
aloft. At the surface, a moist airmass is located from the mid
Missouri Valley east-northeastward into the lower Michigan, where
surface dewpoints are mostly in the upper 60s and lower 70s F. An
axis of low-level convergence is located from northern Iowa into far
southern Wisconsin, along which thunderstorms are ongoing. A couple
of cells have remained discrete across northwestern Iowa, where an
axis of moderate instability is analyzed. As these cells move
southeastward into north-central Iowa this evening, isolated large
hail and a few severe wind gusts will be possible. Further east, the
storms have organized into a line segment over far southern
Wisconsin. These storms will have an isolated wind-damage threat
over the next couple of hours. A marginal severe threat may also
continue over parts of lower Michigan early this evening.

...Central and Northern High Plains...
West-northwesterly mid-level flow is currently located across the
northern Rockies and northern High Plains, with a distinct shortwave
trough moving through Montana. At the surface, an axis of low-level
moisture is present from eastern Wyoming into eastern Montana, along
which surface dewpoints are near 60 F. This is contributing to
MLCAPE around 1000 J/kg along parts of the moist axis. Isolated
strong to severe storms are ongoing near the moist axis in far
northeast Wyoming and in northeast Montana. Moderate deep-layer
shear and steep low to mid-level lapse rates will support a
potential for isolated severe gusts and hail this evening.

..Broyles.. 08/19/2026

Day 3-8 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0448 PM CDT Tue Aug 18 2026

Valid 201200Z - 261200Z

...Synopsis...
An established ridge over the Intermountain West will amplify and
the pressure gradient will tighten on Day 3/Thursday as a trough
approaches the west CONUS coast. A mid-level low pressure system
will near the Pacific Northwest coast on Day 4/Friday as the
upper-level jet max peaks over southern/central OR. This will
provide widespread lift to portions of north-central OR and then
much of central/eastern WA under the left exit region of the jet
streak on the afternoon of Day 4/Friday. The trough will begin to
lift northeastward as it becomes slightly negatively-tilted
progressing into Day 5/Saturday. High pressure remains in place over
much of the southwestern half of the CONUS with shortwave trough
passages periodically moving across the crest of the high through
the northern states. While slight differences in timing of the
aforementioned trough remain, the overall pattern evolution remains
similar amongst various ensemble forecast guidance. As we turn the
corner toward next week, the ridge broadens and builds over the
Intermountain West once again.

...Pacific Northwest/Northern California/Great Basin...
The Pacific Northwest and immediately neighboring areas of northern
California and the Great Basin will remain foci through at least the
first half of the extended forecast. Starting on Day 3/Thursday and
continuing through Day 5/Saturday, expect multiple consecutive days
of gusty southwesterly winds combined with warm and dry weather as
the aforementioned large trough approaches from the west.
Near-normal conditions in the short-term followed by increasing
above-normal temperatures Day 2/Wednesday through Day 4/Friday will
culminate in a cold front passage on Day 5/Saturday as the trough
approaches. Given the jet aloft and surface conditions that would
support deep daytime mixing, a favorable pattern remains in place
for dry and breezy weather to overlap very dry fuels across
northeastern CA, southern OR, and northwestern NV. 40% Critical
probabilities were maintained on Day 4/Thursday through Day
6/Saturday along with a widespread 10% probability of Dry
Thunderstorms over much of the Pacific Northwest and the nearby
northern Rockies. This pattern of aforementioned upper-level
support, limited but adequate (precipitable water values near
0.5-0.7") moisture, fast-moving (25-35 mph) storms, and dry fuels
(ERCs near the 80-95th percentile) remaining in place with minimal
precipitation expected from the previous day, an area of 10% Dry
Thunderstorm risk was introduced over portions of the northern
Pacific Northwest and the nearby northern Rockies regions. Some of
this activity may linger through the night between the two risk
areas as well given the strong dynamic lift from aloft.

...Southern Plains...
On Day 6/Sunday and Day 7/Monday, a cold front will move across the
southern Plains, increasing fire weather risk in southwesterly flow
ahead of the front as it progresses southeastward. Current ensemble
forecast guidance suggests sustained 10-20 mph south to
southwesterly winds will combine with afternoon RHs near 15-20%
across the TX/OK Panhandles and surrounding areas with critically
dry fuels.

...Northern Plains...
Evolution of the post-frontal northwesterly winds over the northern
High Plains remains a concern on Day 6/Sunday. However, current
forecast guidance suggests that RHs are unlikely to reach Critical
thresholds and fuels also remain marginally receptive in some areas.
This region will be monitored with future outlook issuances as
guidance becomes more clear.

..Stearns.. 08/18/2026

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