WW 637 SEVERE TSTM ND SD 302140Z - 310400Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 637
NWS Storm Prediction Center Norman OK
440 PM CDT Sun Aug 30 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Central North Dakota
North-Central South Dakota
* Effective this Sunday afternoon and evening from 440 PM until
1100 PM CDT.
* Primary threats include...
Scattered damaging winds and isolated significant gusts to 75
mph likely
Isolated large hail events to 1.5 inches in diameter possible
SUMMARY...A squall line will move east across the northern portion
of the severe thunderstorm watch with a mix of cells and line
segments farther south near the Dakotas' state border. The main
threats with the stronger storms will be severe gusts 60 to 75 mph
and perhaps isolated large hail with the stronger cores.
The severe thunderstorm watch area is approximately along and 50
statute miles east and west of a line from 55 miles north northeast
of Minot ND to 45 miles southwest of Mobridge SD. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU7).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 636...
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 65 knots. A
few cumulonimbi with maximum tops to 450. Mean storm motion vector
25020.
...Smith
WW 636 SEVERE TSTM MT ND SD WY 301925Z - 310300Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 636
NWS Storm Prediction Center Norman OK
125 PM MDT Sun Aug 30 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Far Eastern Montana
Western North Dakota
Northwestern South Dakota
Far Northeastern Wyoming
* Effective this Sunday afternoon and evening from 125 PM until
900 PM MDT.
* Primary threats include...
Scattered damaging winds and isolated significant gusts to 75
mph possible
Isolated large hail events to 1.5 inches in diameter possible
SUMMARY...Ongoing line of storms moving across northeast Montana has
recently produced gusts over 60 mph. This line is expected to
continue northeastward this afternoon. Additional thunderstorm
development is anticipated across southeast Montana and adjacent far
northeastern Wyoming. This activity is expected to gradually
strengthen, potentially producing strong to severe wind gust from 65
to 80 mph as it moves eastward. Thunderstorm development is also
possible along a cold front is western North Dakota. Large hail and
strong gusts are possible with these storms.
The severe thunderstorm watch area is approximately along and 85
statute miles east and west of a line from 40 miles north northeast
of Williston ND to 75 miles east of Gillette WY. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU6).
PRECAUTIONARY/PREPAREDNESS ACTIONS...
REMEMBER...A Severe Thunderstorm Watch means conditions are
favorable for severe thunderstorms in and close to the watch area.
Persons in these areas should be on the lookout for threatening
weather conditions and listen for later statements and possible
warnings. Severe thunderstorms can and occasionally do produce
tornadoes.
&&
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 65 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
24030.
...Mosier
WW 0637 Status Updates
STATUS FOR WATCH 0637 HAS NOT BEEN ISSUED YET
WW 0636 Status Updates
STATUS FOR WATCH 0636 HAS NOT BEEN ISSUED YET
MD 2176 CONCERNING SEVERE THUNDERSTORM WATCH 636... FOR WESTERN NORTH DAKOTA...NORTHWESTERN SOUTH DAKOTA...ADJACENT PORTIONS OF SOUTHEASTERN MONTANA AND NORTHEASTERN WYOMING
Mesoscale Discussion 2176
NWS Storm Prediction Center Norman OK
0349 PM CDT Sun Aug 30 2026
Areas affected...western North Dakota...northwestern South
Dakota...adjacent portions of southeastern Montana and northeastern
Wyoming
Concerning...Severe Thunderstorm Watch 636...
Valid 302049Z - 302245Z
The severe weather threat for Severe Thunderstorm Watch 636
continues.
SUMMARY...A developing line of thunderstorms across western North
Dakota may begin to become better organized with increasing
potential to produce strong to severe wind gusts while approaching
the Minot through Bismarck ND and Mobridge SD vicinity through 5-7
PM CDT (4-6 PM MDT). Trends will continue to be monitored for the
possibility of a downstream severe weather watch.
DISCUSSION...A surface cold front, enhanced by convective outflow,
continues to strengthen while advancing east-southeastward into and
across the Montana/western Dakotas state border vicinity, with
2-hourly surface pressure rises on the order of 2-3+ mb evident in
20Z surface observations across a broad area of eastern Montana into
the lee of the Bighorn Mountains. A downstream surface pressure
fall center appears to be developing near/southwest through west of
the Bismarck into Minot ND vicinity, ahead of increasing
thunderstorm development within the moderately unstable
boundary-layer near the pre-frontal surface trough axis.
Thunderstorm initiation across western North Dakota has been aided
by eroding inhibition, in the presence of continuing insolation and
the onset of weak cooling aloft. As the leading edge of lower-level
cooling continues to overtake the surface trough, initially discrete
storm development may quickly grow upscale into at least a narrow
evolving line. Although shear is initially modest, with further
strengthening, convection probably will better organize, accompanied
by evolving lower/mid-tropospheric meso-beta scale cyclonic
circulations with increasing potential to produce strong to severe
surface gusts.
..Kerr.. 08/30/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ABR...BIS...UNR...BYZ...GGW...
LAT...LON 49070279 48660132 45740124 44880222 44430405 45050505
46370444 47250416 47980416 48760357 49070279
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0246 PM CDT Sun Aug 30 2026
Valid 302000Z - 311200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND
EVENING FROM SOUTHEAST MONTANA AND FAR NORTHEAST WYOMING INTO THE
CENTRAL DAKOTAS...
...SUMMARY...
Severe storms capable of damaging wind gusts are possible across
portions of the northern Plains this afternoon and evening.
...20z Update...
Only minor changes were made to remove the Marginal Risk from behind
ongoing convection in eastern Montana. Otherwise, the D1 Convective
Outlook remains on track. See previous discussion and MCD #2174 for
more information.
..Thornton.. 08/30/2026
.PREV DISCUSSION... /ISSUED 1129 AM CDT Sun Aug 30 2026/
...Northern High Plains into the northern Plains...
Recent satellite imagery shows a well-defined shortwave trough
moving eastward across southern Saskatchewan and western MT/eastern
ID. A belt of stronger westerly flow aloft likely exists within the
base of this trough from eastern ID into western WY. Recent
mesoanalysis estimates 50 to 60 kt at 500 mb, but its actual
magnitude is uncertain. Showers and isolated thunderstorms are
already ongoing downstream of this wave, and the general expectation
is for these showers and thunderstorms to persist as the wave moves
eastward, eventually encountering a notably more unstable airmass
downstream.
Current surface observations show mid 60s dewpoints into the western
Dakotas, with upper 50s/low 60s dewpoints farther west in eastern
MT. Afternoon high temperatures are expected range from the low to
mid 80s along the MT/ND border into the low 90s farther south into
southwest SD. Despite relatively poor pre-frontal mid-level lapse
rates, the resulting temperature/dewpoint combination will support
MLCAPE ranging from around 500-1000 J/kg across eastern MT and the
western Dakotas to closer to 2000 J/kg across the central Dakotas.
Some low-level stability may linger, but should be overcome by the
strong forcing, and the development of a line of strong to severe
storms is anticipated. Strong to severe gusts will be the primary
risk, with some instance of gusts from 65 to 80 mph possible.
Maximum storm intensity and highest severe coverage is currently
forecast to occur from the ND/SD/MT border intersection vicinity
eastward into south-central ND and north-central SD. Decreasing
buoyancy is expected from the central Dakotas eastward, with
gradually decreasing storm intensity expected as the line of storms
moves into this region this evening.
...Central High Plains...
Increased coverage and depth of the thunderstorms across UT indicate
the presence of secondary area of ascent south of the primary
shortwave trough, perhaps tied to a convectively augmented vorticity
maximum. Expectation is for this vorticity maximum to progress
eastward, persisting across the central Rockies before entering
deeply mixed boundary-layer in place over the central High Plains.
High-based storm character coupled with steep low-level lapse rates
will support the development of strong outflow, and gusts from 60 to
75 mph are possible.
...UT/Western CO...
Thunderstorms are already ongoing from eastern UT into western CO,
and deep-layer vertical shear is already strong enough to support
organization within any more persistent updrafts. A few instances of
hail and/or damaging gusts are possible with this activity.
Additionally, considerable low-level moisture will remain over UT
today, leading to another round of strong to isolated severe
thunderstorms this afternoon. Deep-layer shear will remain
sufficient for rotating storms capable of damaging wind gusts and
hail. This additional activity should also spread into western CO
before weakening this evening.
...Central/Southern AZ...
Ample low-level moisture remains in place across much of AZ, with
upper 50s dewpoints across northern AZ increasing into the mid 60s
across southern AZ. Another day of afternoon thunderstorms is
anticipated as this moist airmass destabilizes amid strong diurnal
heating. High-based storms coupled with moderate buoyancy and steep
low-level lapse rates could result in a few strong to severe gusts
across the region this afternoon and evening.
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1222 PM CDT Sun Aug 30 2026
Valid 311200Z - 011200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM NORTHEAST
COLORADO TO WISCONSIN...
...SUMMARY...
Sparse severe thunderstorms, accompanied by wind and hail, are
possible Monday from the central Plains toward parts of the Upper
Midwest.
...Synopsis and Discussion...
A deep upper low will move eastward across southern SK/MB on Monday,
with 40-50 kt midlevel winds spreading across the Northern Plains
and Upper MS Valley. Meanwhile, an upper high will centered from the
Ozarks to the Mid MS/Lower OH Valleys. Farther west, modest
southwest flow aloft will persist over much of the West, with a
stronger shortwave trough moving into CA late.
At the surface, low pressure will occlude over SK/MB, with dry
westerly winds over the Dakotas and into MN. South of this area, a
weak surface trough/wind shift will remain, roughly from WI into IA
and NE. Here, a moist air mass will exist, with 2000-3000 J/kg
MUCAPE from IA into WI and northern IL. Lesser CAPE values will
develop farther west across NE/KS/CO, with perhaps 1000-1500 J/kg
MUCAPE.
Despite the larger instability over northern areas, forcing for
ascent will be weak. However, areas of uncapped air mass may
develop, possibly supporting isolated afternoon thunderstorms over
WI. Conditionally, hail over 1.00" will be possible. Additional
isolated activity is possible from IA into northern IL overnight.
A greater probability of thunderstorms in general will exist from CO
into NE as an upper wave aloft travels northeast across the region
late in the day. Strong heating over the central High Plains will
support afternoon initiation near the Front Range, with clusters of
storms producing strong to severe outflow, and propagating
northeastward into NE. Initial activity could also produce
marginally severe hail as effective shear averages near 45 kt.
..Jewell.. 08/30/2026
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0234 PM CDT Sun Aug 30 2026
Valid 011200Z - 021200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM WESTERN NEW
YORK ACROSS PENNSYLVANIA AND INTO NEW JERSEY...
...SUMMARY...
Scattered strong to severe storms are possible Tuesday over parts of
New York, Pennsylvania and New Jersey. Isolated severe storms may
also extend westward into Nebraska.
...Synopsis...
A zone of moderate instability is forecast to stretch from the Upper
Midwest eastward into parts of NY, PA and NJ on Tuesday. This will
also be along a weak surface trough, where various areas of rain and
thunderstorms will exist throughout the period. Anticyclonic flow
aloft around the northern periphery of an upper ridge will yield
30-40 kt midlevel northwesterlies, and minor cooling aloft may occur
as embedded disturbances move across the Great Lakes and into the
Northeast.
...Northeast...
The greatest concentration of thunderstorms will be from NY into PA,
both during the day and overnight. Early day storms will be possible
from southern New England into NY, where elevated instability will
exist. Destabilization will then occur south of this zone and
possible outflows, with additional activity possible. Forcing for
ascent should remain relatively weak, but sufficient convergence
near any boundaries or an afternoon surface trough may support
redevelopment. Elongated mid to upper level hodographs suggest
cellular storm mode is possible, with hail and locally damaging
gusts most likely. Overnight, additional activity is forecast as
height falls occur upstream, and westerly winds at 850 mb maintain
theta-e. Several models suggest storms moving out of Ontario
overnight, with wind potential.
...Nebraska into northwest Iowa and vicinity...
Moderate southwest winds aloft will persist over this area, as
daytime heating yield moderate instability. Some of this area may be
affected by early day rain/storms, with boundary reinforcement.
Strong heating and a developing southerly low-level jet should
support new development, perhaps a supercell or two producing hail.
Storm coverage may then increase during the evening and spread
northeastward.
..Jewell.. 08/30/2026
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0245 PM CDT Sun Aug 30 2026
Valid 311200Z - 011200Z
Minor changes were made to the existing Elevated area over far
northeastern CA and south-central OR. The latest forecast guidance
has maintained 15-20 mph southwest surface winds amid 10-20% minimum
RH across the drawn area. While coincident elevated winds and low
RHs may persist slightly farther east into the western Great Basin,
recent rainfall and cool temperatures have reduced fuels below
critical thresholds for now over much of NV.
Meanwhile, the trough axis progressing across the northern tier of
the CONUS on Day 2/Monday will lead to elevated westerly winds near
15-20 mph amid low RHs down to 20-25% over portions of western ND
and nearby areas. However, fuels remain marginally receptive
(especially given preceding precipitation possible on Day 1/Sunday)
across this area, leading to more of a curing event than an
immediate wildfire risk. Given the continued above normal
temperatures amid drier than normal conditions and periodic wind
events, this region will be watched closely as troughing continues
to impact the northern portion of the CONUS.
..Stearns.. 08/30/2026
.PREV DISCUSSION... /ISSUED 1231 AM CDT Sun Aug 30 2026/
...Synopsis...
A broad trough will persist across much of the West on Monday. A
compact shortwave trough will move through the Great Basin through
the day. In its wake, mid-level flow will relax before quickly
increasing again into Tuesday morning. At the surface, a broad and
modest surface trough will develop within the Northwest into the
northern Great Basin. A small zone of favorable overlap of 15-20 mph
winds with marginally lowered RH (15-20%) is forecast from northeast
California into south-central Oregon. Here, marginally elevated fire
weather concerns will exist during the afternoon given the very dry
fuels.
...Please see www.spc.noaa.gov/fire for graphic product...
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