WW 621 SEVERE TSTM ND 232200Z - 240300Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 621
NWS Storm Prediction Center Norman OK
400 PM MDT Sun Aug 23 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Southwest North Dakota
* Effective this Sunday afternoon and evening from 400 PM until
900 PM MDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Isolated significant damaging wind gusts to 75 mph possible
SUMMARY...A few supercells with large hail up to 2 inches in
diameter and isolated severe outflow gusts of 60-75 mph will be
possible into this evening.
The severe thunderstorm watch area is approximately along and 60
statute miles east and west of a line from 55 miles north of
Dickinson ND to 30 miles west of Lemmon SD. For a complete depiction
of the watch see the associated watch outline update (WOUS64 KWNS
WOU1).
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 617...WW 618...WW
619...WW 620...
AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 65 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
32015.
...Thompson
WW 620 SEVERE TSTM MT 232150Z - 240400Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 620
NWS Storm Prediction Center Norman OK
350 PM MDT Sun Aug 23 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Eastern Montana
* Effective this Sunday afternoon and evening from 350 PM until
1000 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...Scattered high-based thunderstorms will spread eastward
from central into eastern Montana through late evening. A few
supercell structures with large hail will be possible initially.
The threat for severe outflow gusts of 60-75 mph will increase as
storms cluster over time.
The severe thunderstorm watch area is approximately along and 100
statute miles east and west of a line from 55 miles north northeast
of Glasgow MT to 80 miles southeast of Billings MT. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU0).
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 617...WW 618...WW 619...
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
27030.
...Thompson
WW 619 SEVERE TSTM ID UT WY 232130Z - 240400Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 619
NWS Storm Prediction Center Norman OK
330 PM MDT Sun Aug 23 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Southeast Idaho
Northern Utah
Extreme southwest Wyoming
* Effective this Sunday afternoon and evening from 330 PM until
1000 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...Scattered thunderstorms are expected through late evening
as a mix of cells and clusters capable of producing severe outflow
gusts of 60-75 mph and isolated large hail up to 1.5 inches in
diameter.
The severe thunderstorm watch area is approximately along and 70
statute miles east and west of a line from 10 miles east northeast
of Pocatello ID to 50 miles southwest of Salt Lake City UT. For a
complete depiction of the watch see the associated watch outline
update (WOUS64 KWNS WOU9).
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 617...WW 618...
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
25030.
...Thompson
WW 618 SEVERE TSTM NE SD 232040Z - 240200Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 618
NWS Storm Prediction Center Norman OK
240 PM MDT Sun Aug 23 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Western and Northwestern Nebraska
Western South Dakota
* Effective this Sunday afternoon and evening from 240 PM until
800 PM MDT.
* Primary threats include...
Scattered damaging winds and isolated significant gusts to 75
mph possible
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
SUMMARY...Widely scattered severe thunderstorms are forecast through
the late afternoon and evening within the Watch area. A couple of
supercells and severe multicells will yield a risk for large hail
(mainly 1 to 2 inches in diameter) and severe gusts (60 to 75 mph).
The severe thunderstorm watch area is approximately along and 60
statute miles east and west of a line from 35 miles northeast of
Buffalo SD to 50 miles southeast of Alliance NE. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU8).
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 617...
AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 65 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
29020.
...Smith
WW 617 SEVERE TSTM MT 231955Z - 240100Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 617
NWS Storm Prediction Center Norman OK
155 PM MDT Sun Aug 23 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Central and Southwest Montana
* Effective this Sunday afternoon and evening from 155 PM until
700 PM MDT.
* Primary threats include...
Scattered damaging winds and isolated significant gusts to 80
mph possible
Isolated large hail events to 1.5 inches in diameter possible
SUMMARY...Scattered thunderstorms are forecast to develop and
intensify and spread from west to east across the Watch area this
afternoon into the early evening. The threat for isolated large
hail will accompany a few cells along with a risk for severe gusts.
As additional storms develop and outflow congeals into one or more
small clusters, an increase in the threat for scattered severe gusts
(60 to 80 mph) will probably occur.
The severe thunderstorm watch area is approximately along and 75
statute miles east and west of a line from 35 miles north northwest
of Havre MT to 50 miles south southwest of Livingston MT. 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.
&&
AVIATION...A few severe thunderstorms with hail surface and aloft to
1.5 inches. Extreme turbulence and surface wind gusts to 70 knots. A
few cumulonimbi with maximum tops to 400. Mean storm motion vector
25030.
...Smith
WW 0621 Status Updates
STATUS REPORT ON WW 621
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..WEINMAN..08/23/26
ATTN...WFO...BIS...
STATUS REPORT FOR WS 621
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
NDC001-007-011-025-033-037-041-053-057-059-065-085-087-089-
240040-
ND
. NORTH DAKOTA COUNTIES INCLUDED ARE
ADAMS BILLINGS BOWMAN
DUNN GOLDEN VALLEY GRANT
HETTINGER MCKENZIE MERCER
MORTON OLIVER SIOUX
SLOPE STARK
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
WW 0620 Status Updates
STATUS FOR WATCH 0620 HAS NOT BEEN ISSUED YET
WW 0619 Status Updates
STATUS REPORT ON WW 619
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..LYONS..08/23/26
ATTN...WFO...PIH...SLC...
STATUS REPORT FOR WS 619
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
IDC005-007-011-019-029-031-041-071-077-240040-
ID
. IDAHO COUNTIES INCLUDED ARE
BANNOCK BEAR LAKE BINGHAM
BONNEVILLE CARIBOU CASSIA
FRANKLIN ONEIDA POWER
UTC003-005-011-029-033-035-043-045-049-051-057-240040-
UT
. UTAH COUNTIES INCLUDED ARE
BOX ELDER CACHE DAVIS
MORGAN RICH SALT LAKE
SUMMIT TOOELE UTAH
WASATCH WEBER
WYC041-240040-
WY
. WYOMING COUNTIES INCLUDED ARE
WW 0618 Status Updates
STATUS REPORT ON WW 618
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..WEINMAN..08/23/26
ATTN...WFO...CYS...LBF...UNR...
STATUS REPORT FOR WS 618
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
NEC013-031-045-069-075-123-161-240040-
NE
. NEBRASKA COUNTIES INCLUDED ARE
BOX BUTTE CHERRY DAWES
GARDEN GRANT MORRILL
SHERIDAN
SDC007-019-033-047-055-063-071-081-093-102-103-105-240040-
SD
. SOUTH DAKOTA COUNTIES INCLUDED ARE
BENNETT BUTTE CUSTER
FALL RIVER HAAKON HARDING
JACKSON LAWRENCE MEADE
OGLALA LAKOTA PENNINGTON PERKINS
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
WW 0617 Status Updates
STATUS REPORT ON WW 617
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 20 SE DLN TO
25 SW LWT TO 50 N LWT TO 55 WSW GGW.
..LYONS..08/23/26
ATTN...WFO...TFX...BYZ...
STATUS REPORT FOR WS 617
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
MTC009-027-031-037-057-067-095-097-107-240040-
MT
. MONTANA COUNTIES INCLUDED ARE
CARBON FERGUS GALLATIN
GOLDEN VALLEY MADISON PARK
STILLWATER SWEET GRASS WHEATLAND
THE WATCH STATUS MESSAGE IS FOR GUIDANCE PURPOSES ONLY. PLEASE
REFER TO WATCH COUNTY NOTIFICATION STATEMENTS FOR OFFICIAL
INFORMATION ON COUNTIES...INDEPENDENT CITIES AND MARINE ZONES
CLEARED FROM SEVERE THUNDERSTORM AND TORNADO WATCHES.
MD 2108 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF NORTHEASTERN OHIO AND NORTHWESTERN PENNSYLVANIA
Mesoscale Discussion 2108
NWS Storm Prediction Center Norman OK
0702 PM CDT Sun Aug 23 2026
Areas affected...Parts of northeastern Ohio and northwestern
Pennsylvania
Concerning...Severe potential...Watch unlikely
Valid 240002Z - 240130Z
Probability of Watch Issuance...5 percent
SUMMARY...A couple strong to locally damaging wind gusts will be
possible during the next hour or two.
DISCUSSION...A loosely organized band of thunderstorms is tracking
southeastward across Lake Erie -- ahead of a midlevel vort max
rotating around a deep upper low over southeastern Ontario. While
cool surface temperatures downstream may limit the overall severe
risk, steepened low-level lapse rates, enhanced unidirectional
low/midlevel flow, and the strengthening cold pool may support a
couple strong to locally damaging wind gusts across parts of
northeastern OH and northwestern PA.
..Weinman/Thompson.. 08/24/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...PBZ...CLE...
LAT...LON 41398201 41658179 41958092 42118001 42007978 41827965
41527981 41158076 41038165 41208196 41398201
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
MD 2107 CONCERNING SEVERE THUNDERSTORM WATCH 617...620... FOR PORTIONS OF MONTANA
Mesoscale Discussion 2107
NWS Storm Prediction Center Norman OK
0656 PM CDT Sun Aug 23 2026
Areas affected...portions of Montana
Concerning...Severe Thunderstorm Watch 617...620...
Valid 232356Z - 240130Z
The severe weather threat for Severe Thunderstorm Watch 617, 620
continues.
SUMMARY...Severe gusts remain possible across portions of MT this
evening. Ongoing storms may gradually evolve into a linear or
cluster or two later this evening.
DISCUSSION...Across WW 617 and 620, several clusters of strong to
severe storms remain ongoing this evening. The air mass downstream
is hot and sufficiently unstable to support the ongoing storms. Some
CAM guidance and radar trends suggest some upscale growth into one
or more clusters is possible this evening. This appears most likely
across northern portions of MT where more robust convection is
ongoing. Stronger vertical shear may also support better
organization of these storms with time. With steep lapse rates in
the lowest several km, severe gusts remain likely this evening.
..Lyons.. 08/23/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...BIS...UNR...BYZ...GGW...RIW...TFX...PIH...
LAT...LON 45401191 46910951 49070834 49070393 44900404 44801039
44691149 44691192 45401191
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
MD 2106 CONCERNING SEVERE THUNDERSTORM WATCH 619... FOR NORTHERN UTAH...SOUTHEAST IDAHO AND FAR SOUTHWEST WYOMING
Mesoscale Discussion 2106
NWS Storm Prediction Center Norman OK
0556 PM CDT Sun Aug 23 2026
Areas affected...northern utah...southeast Idaho and far southwest
Wyoming
Concerning...Severe Thunderstorm Watch 619...
Valid 232256Z - 240030Z
The severe weather threat for Severe Thunderstorm Watch 619
continues.
SUMMARY...Severe wind gusts and hail remain possible with strong to
severe storms across UT/ID and far western WY this evening.
DISCUSSION...Across WW 619, a band of strong to severe storms have
matured across eastern ID with more isolated strong storms ongoing
over northwest UT late this afternoon. A modestly moist, hot and
moderately unstable air mas remains in place ahead of these storms
which should continue to support them over the next several hours.
Steep low-level lapse rates will primarily favor severe wind gusts,
but enhanced mid-level flow at the base of the northern Rockies
upper trough is supporting some cellular structures. Hail is
possible, especially with any persistent supercells.
Expectations are for convection to gradually spread northeastward
across UT and far southwestern WY into this evening. Some clustering
is possible, based on recent CAM solutions. This appears most likely
over northern UT into southwest WY. This could support a localized
corridor of more concentrated severe wind gusts later this evening.
Given the ongoing storms and a generally favorable environment, the
severe risk continues for much of WW619.
..Lyons.. 08/23/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...RIW...SLC...PIH...LKN...
LAT...LON 40841426 42451323 42961137 42831076 42161028 41791002
41361001 40651007 40011066 39891240 39851330 39921368
40001404 40841426
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Sun Aug 23 2026
Valid 232000Z - 241200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN ROCKIES/PLAINS AND GREAT BASIN...
...SUMMARY...
Thunderstorms capable of producing large hail and severe wind gusts
are forecast across parts of the northern Rockies/Plains this
afternoon and evening. Other thunderstorms with mainly a severe
wind threat are probable over portions of the northern Great Basin.
...20z Update...
...Northern Rockies/Plains and Great Basin...
Subtle adjustments were made to the existing Marginal/Slight risk
areas based on ongoing convective trends. Recent CAM/TLE guidance
suggests that upscale growth of convection into one or more linear
clusters may result in localized corridors of greater
damaging/severe wind coverage across portions of northern Utah and
central Montana. The evolution of this scenario remains somewhat
uncertain, however, which precludes the addition of 30% wind
probabilities at this time. See MCDs 2099, 2100, and 2101 for
additional short-term details.
...Coastal Carolinas...
Recent mesoanalysis and observational data depict modestly elongated
hodographs and effective shear around 35 kts in place across
portions of the Coastal Carolinas. Despite poor mid-level lapse
rates, this may allow for the occurrence of isolated, marginally
severe hail with the most robust updraft cores. Thus, a targeted 5%
hail probability area was included with this update, which is
similarly supported by AI/ML guidance and recent CAM solutions.
Elsewhere, the forecast remains largely on track, with only minor
adjustments made based on the latest forecast and observational
trends. See the discussion below for additional details.
..Chalmers/Moore.. 08/23/2026
.PREV DISCUSSION... /ISSUED 1135 AM CDT Sun Aug 23 2026/
...Great Basin into the Northern Rockies/High Plains...
Water-vapor imagery this morning shows an eastward-migrating
shortwave trough over the Pacific Northwest. A belt of 40-50 kt of
west-southwesterly mid-level flow will overspread the northern
Rockies and adjacent High Plains of central/eastern MT by this
afternoon. Heating along with ascent attendant to the disturbance
will favor initial storm development over the higher terrain over
southwest/western MT. Steepening lapse rates over the High Plains
will favor the potential for scattered severe gusts as thunderstorms
move/develop over the plains during the late afternoon and evening.
A mix of multicells and supercells may yield a risk for severe hail
early before upscale growth into linear clusters (60-80 mph gusts)
likely evolves during the evening.
A somewhat separate area of convection should develop this afternoon
across parts of the northern Great Basin and Upper Snake Valley.
While mid-level flow will be somewhat weaker across this region
compared to locations farther north, the presence of generally 50s
surface dewpoints across northern UT and vicinity suggests that
sufficient low-level moisture exists to support robust updrafts.
Very steep lapse rates will favor ample evaporative cooling in the
stronger downdrafts. Scattered severe gusts (60-80 mph) are
possible with the stronger thunderstorm cores and outflow.
...Northern/Central Plains...
Morning surface analysis places a moisture plume (lower to mid 60s
deg F dewpoints) extending from the TX-OK Panhandles
north-northwestward through eastern CO/NE Panhandle and into the
Black Hills vicinity. It is within this corridor moderate to strong
instability is forecast by mid-late afternoon along/east of a lee
surface trough. At least isolated thunderstorms should develop by
peak afternoon heating across these areas, with west-northwesterly
flow strengthening with height through mid/upper levels. Around
35-45 kt of deep-layer shear will support supercells and associated
threat for large hail from northeast CO northward into the western
Dakotas.
Farther south, high-based convection is forecast to slowly
spread/move east of the Raton Mesa into the TX-OK Panhandles during
the early evening. Very steep lapse rates and inverted-V profiles
will favor evaporative cooling and an isolated threat for severe
gusts with the stronger downdrafts and outflow surges.
...Northeast...
Midday satellite imagery shows an upper trough/low over Ontario with
a series of embedded shortwave impulses rotating through its base.
A lead disturbance over the Lower Great Lakes will continue to
rotate northeastward across the western portion of the Northeast and
influence scattered thunderstorm development this afternoon.
Heating of an adequately moist airmass but relatively meager
mid-level lapse rate environment will result in weak buoyancy
developing through mid afternoon as convection deepens. Around
30-35 kt of deep-layer shear will support some updraft organization
mainly in the form of bands of storms. An isolated risk for strong
to locally severe gusts is expected across much of this region this
afternoon. Towards early evening, an upstream impulse will approach
the Lake Erie vicinity with some uptick in storm coverage and
perhaps a lingering risk for wind damage before this activity
weakens by the mid evening.
...Southeast...
Isolated to scattered thunderstorms will likely develop along/south
of a weak front draped across the lower MS Valley into the Gulf
Coast states, and continuing northeastward into the Carolinas. An
isolated threat for strong to locally severe gusts may result in
pockets of wind damage with the more intense wet microbursts.
...Northeast Oklahoma/Southeast Kansas into the Ozarks...
Some modest increase in isentropic ascent associated with
a south-southwesterly low-level jet, may aid thunderstorm
development late tonight into early Monday morning across parts of
northeast OK/southeast KS into the Ozarks. Instability is forecast
to remain fairly weak (MUCAPE generally less than 1000 J/kg), but
some clustering may occur with a low chance for localized severe
gusts.
...Arizona...
On the western periphery of a mid-level anticyclone centered over
eastern NM, weak southeasterly mid-level flow will remain across
southern/central AZ. Model guidance only depicts weak buoyancy
across much of central and southern AZ, with the exception of
perhaps over far southern AZ. Nonetheless, hot temperatures and a
deeply mixed boundary layer lend some potential for a localized
microburst risk.
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 PM CDT Sun Aug 23 2026
Valid 251200Z - 261200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL AND SOUTHERN HIGH PLAINS...
...SUMMARY...
At least widely scattered severe storms are likely across portions
of the central Plains on Tuesday. More isolated severe storms may
also occur across parts of the Southeast and the Upper Mississippi
Valley.
...Synopsis...
A synoptic scale mid-level anticyclone will overspread most of the
western and central CONUS on Tuesday, with multiple mid-level
impulses poised to pivot around the anticyclone across the Plains
states into the Upper- and Mid-MS Valleys. The most pronounced
impulse, in the form of a mid-level shortwave trough, will traverse
the northern Plains Tuesday afternoon, supporting a surface trough
with a cold front draping southwestward across the Plains. Along and
ahead of the cold front, enough deep-layer shear and ascent, in
tandem with adequate buoyancy, will support at least scattered
severe storms across the southern and central High Plains into the
Upper MS Valley.
...Central and southern High Plains...
As a mid-level impulse crests the ridge and tracks southeastward
across the northern Plains, a cold front will drift
south-southeastward across NE. Meanwhile, upslope moist low-level
flow will encourage both increased instability and convergence along
the immediate lee of the Rockies over NM and CO. 8 C/km mid-level
lapse rates will overspread 60s F surface dewpoints, yielding
2000-4000 J/kg MLCAPE, with the strongest buoyancy expected
immediately ahead of the cold front over northeast CO into NE. Here,
the greatest severe threat exists since 40 kts of effective bulks
shear will also coincide with the aforementioned buoyancy, with
severe wind- and hail-producing multicells and supercells expected.
There is some indication for the potential of cold-pool mergers and
subsequent development of an MCS. If this occurs, a severe wind
swath would manifest across the central High Plains. Farther south
into the southern High Plains, a deep and dry boundary layer will
compensate for weaker vertical wind shear to support a severe gust
threat in association with dry downbursts, driven by evaporative
cooling.
...Upper MS Valley...
A narrow tongue of at least mid 60s F surface dewpoints will advect
ahead of a surface trough/cold front Tuesday afternoon. Though
mid-level lapse rates may be modest, the rich low-level moisture
will support 2000-3000 J/kg MLCAPE. Furthermore, southwesterly
surface winds beneath stronger northwesterly flow aloft support
modestly elongated and curved hodographs, with supercells possible.
All severe hazards are possible with these storms, including an
instance or two of 2+ inch diameter hail and perhaps a couple of
tornadoes. An upgrade to Slight Risk may be needed in future
outlooks if consensus and consistency among guidance members
indicates relatively greater storm coverage.
...Portions of the Gulf Coast...
Another day of deep-layer north-northwesterly flow, atop a very
moist boundary layer (i.e. 70s F surface dewpoints), will encourage
multicellular development amid 1000-2000 J/kg MLCAPE. The stronger
storm cores may support wet downdrafts, the strongest of which may
produce isolated wind damage.
..Squitieri.. 08/23/2026
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0218 PM CDT Sun Aug 23 2026
Valid 241200Z - 251200Z
...Northern Great Basin...
A subtle upper-level wave still off the CA coast will glance through
northern CA and the northern Great Basin D2/Monday. This feature
along with a transient mid/upper level moisture plume and increasing
afternoon instability, will promote isolated high-based convection
across portions of northern NV, southeast OR, southwest ID and far
northeast CA Monday afternoon and early evening. A dry, well-mixed
boundary layer and faster shower/thunderstorm trajectories should
limit surface precipitation and promote an increased ignition
potential amid a receptive fuelscape.
...Southern Plains...
Dry west/southwest flow south of an emergent surface low across
western OK will bring elevated fire weather conditions to the
Rolling Plains of northwest TX and far southwestern OK on D2/Monday.
Although some rainfall has occurred in parts of northwest TX, above
normal temperatures in the lower 100s and relative humidity
reductions to around 15 percent by peak afternoon heating will
quickly dry out overall dormant/cured fine fuels. The existing
Elevated Highlights were shifted slightly southward based on latest
model guidance.
..Williams.. 08/23/2026
.PREV DISCUSSION... /ISSUED 0158 AM CDT Sun Aug 23 2026/
...Synopsis...
Embedded within a belt of enhanced southwesterly flow aloft, a
subtle/low-amplitude wave will overspread parts of the northern
Great Basin. Here, sufficient midlevel moisture atop a diurnally
deepening boundary layer will promote isolated high-based
thunderstorms across parts of northern NV, southeast OR, southwest
ID, and far northeast CA during the afternoon and early evening. PW
values around 0.6 inches will favor mostly dry thunderstorms, which
will pose a risk of isolated lightning-induced ignitions, given a
dry/receptive fuelscape (90th-95th percentile ERCs).
Farther south, a surface low will evolve eastward across parts of
the southern Plains during the day. A tightening pressure gradient
peripheral to this feature will aid in the development of 15-20 mph
sustained west-southwesterly surface winds across parts of the TX
South Plains into southwest OK during the afternoon. These winds,
combined with 15-20 percent RH, will lead to elevated fire-weather
conditions.
...Please see www.spc.noaa.gov/fire for graphic product...
SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0433 PM CDT Sun Aug 23 2026
Valid 251200Z - 311200Z
...Synopsis...
An upper-level ridge extending northward from broad high pressure
across the Southwest will bring warmer and drier conditions to much
of the Northwest and Northern Rockies. Dry southwesterly flow aloft
and departure of deeper monsoon moisture will keep fire weather
concerns in the form of dry and breezy conditions for portions of
the Great Basin and Columbia Basin for the middle of the week,
reaching the central ID mountains by Day 5/Thursday as fuels dry.
The threat of dry thunderstorms returns to the northern Rockies Day
4/Wednesday with the arrival of an upper-level trough into the
Pacific Northwest. Diurnal showers/thunderstorms along higher
terrain will likely shift eastward, mainly along the Rockies by the
end of the week with another possible upper-level wave entering the
Pacific Northwest by the weekend, although forecast uncertainty
increases during this time frame.
...Northwest, Northern Great Basin and Northern Rockies...
A drier southwest flow pattern will bring a multi-day fire weather
threat back into portions of the northwestern U.S., with fire
weather concerns extending eastward into the central ID mountains
later this week as fuels recover from recent monsoon moisture. The
40 percent critical probabilities have generally been expanded for
Days 3-5/Tuesday-Thursday, with additional threat areas for both
Days 6-7/Friday-Saturday. West to southwest winds of 15-20 mph and
afternoon relative humidity between 15-20 percent will bring at
least daily elevated fire weather concerns to this region. Critical
fire weather conditions with winds of 20+ mph are likely but only in
localized areas, particularly from northeastern CA into far
northwestern NV and southeastern OR where afternoon relative
humidity reached 10 percent under more robust mid-level flow.
Enhanced onshore flow develops across the Pacific Northwest as the
next upper-level trough impacts the region midweek. This will
bolster downslope drying across the Columbia Basin where afternoon
relative humidity reductions of around 15 percent are possible. This
dry atmospheric and fuel environment, coupled with west/southwest
winds of 15-20 mph, will likely bring a fire weather threat for the
Columbia Basin both Wednesday and Thursday.
...Dry Thunderstorms...
The arrival of the next upper-level wave will bring additional
opportunities for afternoon showers and thunderstorms across the
northern Rockies on Day 4/Wednesday. The eastward shunting of deeper
monsoon moisture under a drier southwest flow regime and building
ridge over the northern Rockies on Day 3/Tuesday will likely
contribute to a drying boundary layer in advance of the next
mid/upper wave on Day 4/Wednesday. This should set the stage for at
least isolated high-based thunderstorm development over the northern
Rockies Wednesday afternoon where fuels will have undergone two days
of drying. Given the modest mid-level moisture with PWATs less than
0.8", widespread thunderstorm activity is not expected at this time
with a 10 percent probability area maintained.
..Williams.. 08/23/2026
...Please see www.spc.noaa.gov/fire for graphic product...
|
