WW 578 SEVERE TSTM CO NE WY 122030Z - 130300Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 578
NWS Storm Prediction Center Norman OK
230 PM MDT Wed Aug 12 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Northeast Colorado
The Nebraska Panhandle
Southeast Wyoming
* Effective this Wednesday afternoon and evening from 230 PM
until 900 PM MDT.
* Primary threats include...
Scattered damaging winds and isolated significant gusts to 80
mph possible
Scattered large hail and isolated very large hail events to 2.5
inches in diameter possible
SUMMARY...Isolated storm development is underway across southeast
Wyoming, and additional storms are expected this afternoon into the
Nebraska Panhandle and northeast Colorado. Large hail (potentially
exceeding 2 inches in diameter) will be possible with
initial/discrete supercells, while the threat for severe outflow
gusts of 60-80 mph will increase with storm clustering later this
afternoon through late evening.
The severe thunderstorm watch area is approximately along and 75
statute miles east and west of a line from 20 miles northwest of
Chadron NE to 15 miles southwest of Akron CO. 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 575...WW 576...WW 577...
AVIATION...A few severe thunderstorms with hail surface and aloft to
2.5 inches. Extreme turbulence and surface wind gusts to 70 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
24035.
...Thompson
WW 577 SEVERE TSTM IL IN KY 121920Z - 130100Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 577
NWS Storm Prediction Center Norman OK
320 PM EDT Wed Aug 12 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Extreme southeast Illinois
Southern Indiana
North central and central Kentucky
* Effective this Wednesday afternoon and evening from 320 PM
until 900 PM EDT.
* Primary threats include...
Scattered damaging winds likely with isolated significant gusts
to 75 mph possible
Isolated large hail events to 1.5 inches in diameter possible
A tornado or two possible
SUMMARY...Thunderstorms are expected to evolve into a cluster and
spread southeastward from southern Indiana into Kentucky through
this evening. Wind damage and occasional severe gusts of 60-75 mph
will be the main threat, though isolated large hail of 1-1.5 inches
in diameter will be possible with the strongest storms. An isolated
tornado or two may also occur where storms interact with a residual
outflow boundary.
The severe thunderstorm watch area is approximately along and 80
statute miles east and west of a line from 55 miles northwest of
Louisville KY to 55 miles south of Louisville KY. 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 575...WW 576...
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 550. Mean storm motion vector
32030.
...Thompson
WW 576 SEVERE TSTM SD WY 121905Z - 130200Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 576
NWS Storm Prediction Center Norman OK
105 PM MDT Wed Aug 12 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Western South Dakota
Extreme northeast Wyoming
* Effective this Wednesday afternoon and evening from 105 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 3
inches in diameter possible
A tornado or two possible
SUMMARY...Isolated supercells are expected to move generally
eastward from Wyoming into South Dakota, with additional storm
development possible through the afternoon toward northwest South
Dakota. Isolated very large hail up to 3 inches in diameter will be
a primary threat, though an isolated tornado will be possible near
the Wyoming/South Dakota border. A greater threat for severe
outflow gusts is expected later this afternoon/evening with any
storm clustering.
The severe thunderstorm watch area is approximately along and 65
statute miles east and west of a line from 105 miles north of Rapid
City SD to 70 miles south of Rapid City SD. 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.
&&
OTHER WATCH INFORMATION...CONTINUE...WW 575...
AVIATION...A few severe thunderstorms with hail surface and aloft to
3 inches. Extreme turbulence and surface wind gusts to 65 knots. A
few cumulonimbi with maximum tops to 550. Mean storm motion vector
29025.
...Thompson
WW 575 SEVERE TSTM IN 121535Z - 122100Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 575
NWS Storm Prediction Center Norman OK
1035 AM CDT Wed Aug 12 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Central and northern Indiana
* Effective this Wednesday morning and afternoon from 1035 AM
until 400 PM CDT.
* 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...An ongoing cluster of storms will spread
east-southeastward across northern and central Indiana through the
afternoon, with the potential for occasional 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 60
statute miles east and west of a line from 70 miles north northeast
of Lafayette IN to 35 miles south of Indianapolis IN. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU5).
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 574...
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 550. Mean storm motion vector
30040.
...Thompson
WW 0578 Status Updates
STATUS FOR WATCH 0578 HAS NOT BEEN ISSUED YET
WW 0577 Status Updates
STATUS REPORT ON WW 577
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..MEAD..08/12/26
ATTN...WFO...PAH...LMK...
STATUS REPORT FOR WS 577
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
ILC047-185-122140-
IL
. ILLINOIS COUNTIES INCLUDED ARE
EDWARDS WABASH
INC019-025-037-043-051-061-077-117-123-125-129-143-147-163-173-
175-122140-
IN
. INDIANA COUNTIES INCLUDED ARE
CLARK CRAWFORD DUBOIS
FLOYD GIBSON HARRISON
JEFFERSON ORANGE PERRY
PIKE POSEY SCOTT
SPENCER VANDERBURGH WARRICK
WASHINGTON
KYC005-021-027-029-045-059-067-073-079-085-087-091-093-099-101-
103-111-113-123-137-151-155-163-167-179-183-185-211-215-217-223-
229-239-122140-
WW 0576 Status Updates
STATUS FOR WATCH 0576 HAS NOT BEEN ISSUED YET
WW 0575 Status Updates
STATUS REPORT ON WW 575
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 45 SE IND TO
45 WNW LUK.
..MEAD..08/12/26
ATTN...WFO...IWX...IND...
STATUS REPORT FOR WS 575
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
INC005-013-027-031-055-071-079-083-093-101-153-122040-
IN
. INDIANA COUNTIES INCLUDED ARE
BARTHOLOMEW BROWN DAVIESS
DECATUR GREENE JACKSON
JENNINGS KNOX LAWRENCE
MARTIN SULLIVAN
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 1956 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR PORTIONS OF SOUTHEASTERN WYOMING INTO NORTHEASTERN COLORADO AND THE NEBRASKA PANHANDLE
Mesoscale Discussion 1956
NWS Storm Prediction Center Norman OK
0233 PM CDT Wed Aug 12 2026
Areas affected...portions of southeastern Wyoming into northeastern
Colorado and the Nebraska Panhandle
Concerning...Severe potential...Watch likely
Valid 121933Z - 122130Z
Probability of Watch Issuance...80 percent
SUMMARY...Scattered, initially high-based thunderstorms are expected
to develop along and east of the Front Range over the next couple of
hours. These storms will evolve eastward through this evening,
bringing a threat for severe wind gusts and large hail.
DISCUSSION...Aided by forcing for ascent ahead of a mid-level
perturbation and along/ahead of a surface stationary/cold front,
scattered thunderstorm development is expected along the Front Range
from southeastern Wyoming into northern Colorado over the next 1-2
hours. Storms will be initially high-based given hot temperatures
and well-mixed boundary layer profiles (low-90s F temperatures amid
dewpoints in the mid-40s) ahead of the aforementioned surface
boundary. While effective shear around 35-40 kts will be sufficient
for supercell structures, high cloud bases (LCLs of 2+ km AGL) and
steep low-level lapse rates will favor efficient evaporative
cooling, downdraft formation, and upscale growth/clustering as
convection evolves eastward. Severe wind gusts (a few significant)
will be the main threat with this activity, but large to very large
hail is also expected, especially early in the convective cycle and
with any convection that is able to maintain a discrete mode. A
Severe Thunderstorm Watch will likely be needed for at least a
portion of the discussion area in the next 1-2 hours to cover these
threats.
..Chalmers/Thompson.. 08/12/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LBF...UNR...GLD...BOU...CYS...
LAT...LON 39980444 40550467 41750481 42560476 42960439 43050376
43050296 42820258 42080220 41200211 40260211 39670219
39380251 39180335 39300381 39500414 39980444
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
MD 1955 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF CENTRAL AND EASTERN LOWER MICHIGAN
Mesoscale Discussion 1955
NWS Storm Prediction Center Norman OK
0228 PM CDT Wed Aug 12 2026
Areas affected...portions of central and eastern lower Michigan
Concerning...Severe potential...Watch unlikely
Valid 121928Z - 122130Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated severe storms capable of marginally severe hail
and/or damaging wind gusts appear possible late this afternoon. A
watch is not currently expected due to the limited areal coverage of
the severe weather threat.
DISCUSSION...Recent visible satellite imagery shows areas of
deepening cumulus within a broadly confluent zone stretching through
central lower MI, from KLDM to KD95. While multilevel clouds have
slowed diabatic heating and resultant air mass destabilization,
modification of the 15Z DTX sounding for current surface conditions
yields MLCAPE of 1000-1500 J/kg. Water vapor imagery suggests that
stronger forcing for ascent associated with a weak mid-level
disturbance is currently shifting to the east of the region with
low-level convergence and modest warm advection serving as the
primary sources for widely scattered storm development by late
afternoon. Additionally, surface observations and visible satellite
suggest convective outflow from ongoing storms over IN and OH
surging north, which may also focus storm development.
Regional VWPs are sampling 40-50+ kt west-northwest winds generally
above 4 km AGL, which are yielding sufficient deep-layer shear for
some storm organization, including episodic supercell structures.
Poor mid-level lapse rates of less than 7 C/km should limit hail
sizes, though some marginally severe hail appears possible with the
strongest storms. Damaging wind potential will be contingent on
storms merging into clusters, leading to some cold pool
organization.
..Mead/Thompson.. 08/12/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DTX...APX...GRR...
LAT...LON 42588287 42928372 43608533 44068546 44388481 44088400
43768301 43508243 42938221 42628243 42588287
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
MD 1954 CONCERNING SEVERE POTENTIAL...WATCH LIKELY FOR PORTIONS OF NORTHEASTERN WYOMING AND FAR SOUTHEASTERN MONTANA INTO THE BLACK HILLS AND WESTERN SOUTH DAKOTA
Mesoscale Discussion 1954
NWS Storm Prediction Center Norman OK
0145 PM CDT Wed Aug 12 2026
Areas affected...portions of northeastern Wyoming and far
southeastern Montana into the Black Hills and western South Dakota
Concerning...Severe potential...Watch likely
Valid 121845Z - 122045Z
Probability of Watch Issuance...80 percent
SUMMARY...Scattered thunderstorms will develop eastward into the
Black Hills/western South Dakota vicinity through this afternoon,
bringing a threat for large to very large hail and severe wind
gusts.
DISCUSSION...Latest radar imagery depicts a developing supercell in
close proximity to a surface low across northeastern Wyoming. Aided
by weak ascent ahead of a mid-level perturbation and easterly,
upslope flow (surface dewpoints ranging from the low 60s F to near
70 farther east), convection will expand in coverage through the
afternoon as it evolves eastward into the Black Hills/western South
Dakota vicinity. While the 18z UNR observed sounding depicted
lingering inhibition, filtered diurnal heating should gradually
reduce inhibition through the afternoon. For ongoing/developing
convection, steep mid-level lapse rates (8+ C/km), 40-50+ kts of
effective shear, and relatively straight, elongated hodographs will
support supercells as the initial storm mode, with large to very
large hail the primary hazard. Increasing storm coverage lends
uncertainty to how long discrete supercells will be maintained, with
eventual upscale growth/cluster development expected to yield a
transition towards severe wind gusts as the primary hazard. Should a
discrete mode be maintained for longer, however, very large hail to
3 inches in diameter would be possible. A Severe Thunderstorm Watch
will likely be needed for a portion of the area within the hour.
..Chalmers/Thompson.. 08/12/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ABR...LBF...UNR...CYS...BYZ...
LAT...LON 44660525 44950506 45510373 45500236 45040131 44360096
43600107 43130139 43010175 42850299 42810383 42870451
43100512 43300535 43680538 44220535 44660525
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...2.00-3.50 IN
SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1130 AM CDT Wed Aug 12 2026
Valid 121630Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM ILLINOIS TO
KENTUCKY AND FROM THE NORTHERN HIGH PLAINS TO THE MID MISSOURI
VALLEY...
...SUMMARY...
Scattered severe thunderstorms with occasional wind damage are
possible this afternoon/evening from Illinois/Indiana into Kentucky.
Initial supercells with very large hail will be possible this
afternoon/evening across the central/northern High Plains. The
storms are expected to evolve into a cluster or two overnight while
spreading eastward across Nebraska/South Dakota with the potential
for severe outflow gusts.
...OH Valley area through this evening...
An MCS is ongoing across northern IL with the primary cold pool
surge and bowing segment progressing from northeast IL into
northwest IN. Elevated convection is ongoing in the zone of warm
advection atop the cold pool in IN. This elevated convection will
pose a threat for isolated large hail into this afternoon, while a
feed of steeper midlevel lapse rates and low-level moisture from the
west will help maintain the IL/IN MCS into this afternoon with a
continued threat for occasional wind damage with gusts of 60-75 mph.
The eastern extent of the severe threat into OH is uncertain given
the ongoing/elevated convection and limited recovery time. Thus,
the eastward extent of any wind threat associated with the ongoing
IL/IN MCS is likewise uncertain. Additional thunderstorm
development is possible this afternoon along the trailing outflow
from central IL into southern IN and KY, where occasional wind
damage will be possible into this evening.
...Northern Plains this afternoon through tonight...
A subtle midlevel speed max over southwest WY will progress eastward
around the northwest periphery of the southern Plains ridge. Weak
ascent preceding this wave, in combination with surface heating in
cloud breaks and low-level upslope flow with boundary-layer
dewpoints in the 60s, will support scattered afternoon/evening
thunderstorm development from northeast CO into western SD.
Lingering steep midlevel lapse rates on the fringe of the monsoonal
moisture plume in WY and effective bulk shear near or above 40 kt
(with long hodographs aloft) will favor supercells initially with
the potential for very large hail (2-3 inches in diameter). There
will likely be some upscale growth into a cluster or two this
evening into tonight on the nose of a 30-40 kt low-level jet across
NE/SD, with a transition to severe outflow gusts of 65-80 mph as the
main threat. The storm cluster(s) will likely reach western IA
early Thursday morning.
...Lower MI into western NY/PA through late evening...
Subtle speed maxima will move east-southeastward from Lower MI to
NY/PA through this evening. Midlevel lapse rates of 6-7 C/km and
boundary-layer dewpoints in the mid 60s will support MLCAPE near or
above 1000 J/kg, in an environment with sufficient deep-layer
shear/hodograph length for storms with supercell structures.
Isolated large hail and wind damage will be the main threats, though
a more discrete mode would be less favorable for wind damage, and
storm coverage could remain somewhat isolated. Thus, will maintain
a MRGL risk, though there was some consideration for an upgrade to
SLGT across western NY and vicinity.
...South GA/north FL this afternoon...
Scattered thunderstorm development appears probable from south GA
into north FL this afternoon along a subtle confluence zone with
large buoyancy immediately southwest of a remnant MCV over southeast
GA. A few multicell clusters will be capable of producing isolated
strong outflow gusts/wind damage with downbursts.
..Thompson/Chalmers.. 08/12/2026
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Wed Aug 12 2026
Valid 122000Z - 131200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE NORTHERN AND CENTRAL PLAINS AND LOWER OHIO VALLEY...
...SUMMARY...
Scattered severe thunderstorms with occasional wind damage remain
likely this afternoon/evening from Illinois/Indiana into Kentucky.
Initial supercells with very large hail across the central/northern
High Plains are expected to evolve into a cluster or two overnight
while spreading eastward across Nebraska/South Dakota with the
potential for severe gusts.
...20z Update OH Valley...
Several clusters of strong to severe storms remain ongoing in
proximity to the outflow from the prior complex this morning.
Expectations are for additional storm development to occur along the
southern portions of the outflow across southern IN/IL and
western/northern KY where the air mass remains quite warm and
unstable (MLCAPE 300-4000 J/kg). Deep-layer shear of 25-35 kt would
support a mixed mode of clusters and short line segments, with
severe gusts (some 70-75 mph), isolated hail and a tornado or two
possible into this evening. Have trimmed probabilities behind the
current storms/outflow and adjusted CIG1 wind probabilities farther
southwest.
...WY/SD/NE...
Initial supercells have developed and are maturing within a broad
post-frontal upslope flow regime across eastern WY/MT, western SD
and northwest NE. These storms are expected to remain mostly
supercellular and should continue to pose a threat for large to very
large hail (2-3 inch), severe wind gusts and potentially a tornado
or two into this evening as they track eastward along a diffuse
frontal boundary. Additional, likely higher-based storms should
develop across northeast CO and western NE before spreading
northeastward with a risk for severe gusts and some hail.
Eventually, upscale growth into one or more clusters/bowing segments
appears likely as a 40-50 kt low-level jet and strong low-level warm
advection is forecast to develop across the central/northern Plains.
This would support a risk for severe gusts of 65-80 mph across parts
of central and eastern NE/SD, likely reaching western IA by early
Thursday morning. 2% tornado probabilities have been added to
western SD and eastern WY where the supercellular mode could support
some tornado risk.
..Lyons.. 08/12/2026
.PREV DISCUSSION... /ISSUED 1130 AM CDT Wed Aug 12 2026/
...OH Valley area through this evening...
An MCS is ongoing across northern IL with the primary cold pool
surge and bowing segment progressing from northeast IL into
northwest IN. Elevated convection is ongoing in the zone of warm
advection atop the cold pool in IN. This elevated convection will
pose a threat for isolated large hail into this afternoon, while a
feed of steeper midlevel lapse rates and low-level moisture from the
west will help maintain the IL/IN MCS into this afternoon with a
continued threat for occasional wind damage with gusts of 60-75 mph.
The eastern extent of the severe threat into OH is uncertain given
the ongoing/elevated convection and limited recovery time. Thus,
the eastward extent of any wind threat associated with the ongoing
IL/IN MCS is likewise uncertain. Additional thunderstorm
development is possible this afternoon along the trailing outflow
from central IL into southern IN and KY, where occasional wind
damage will be possible into this evening.
...Northern Plains this afternoon through tonight...
A subtle midlevel speed max over southwest WY will progress eastward
around the northwest periphery of the southern Plains ridge. Weak
ascent preceding this wave, in combination with surface heating in
cloud breaks and low-level upslope flow with boundary-layer
dewpoints in the 60s, will support scattered afternoon/evening
thunderstorm development from northeast CO into western SD.
Lingering steep midlevel lapse rates on the fringe of the monsoonal
moisture plume in WY and effective bulk shear near or above 40 kt
(with long hodographs aloft) will favor supercells initially with
the potential for very large hail (2-3 inches in diameter). There
will likely be some upscale growth into a cluster or two this
evening into tonight on the nose of a 30-40 kt low-level jet across
NE/SD, with a transition to severe outflow gusts of 65-80 mph as the
main threat. The storm cluster(s) will likely reach western IA
early Thursday morning.
...Lower MI into western NY/PA through late evening...
Subtle speed maxima will move east-southeastward from Lower MI to
NY/PA through this evening. Midlevel lapse rates of 6-7 C/km and
boundary-layer dewpoints in the mid 60s will support MLCAPE near or
above 1000 J/kg, in an environment with sufficient deep-layer
shear/hodograph length for storms with supercell structures.
Isolated large hail and wind damage will be the main threats, though
a more discrete mode would be less favorable for wind damage, and
storm coverage could remain somewhat isolated. Thus, will maintain
a MRGL risk, though there was some consideration for an upgrade to
SLGT across western NY and vicinity.
...South GA/north FL this afternoon...
Scattered thunderstorm development appears probable from south GA
into north FL this afternoon along a subtle confluence zone with
large buoyancy immediately southwest of a remnant MCV over southeast
GA. A few multicell clusters will be capable of producing isolated
strong outflow gusts/wind damage with downbursts.
SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1235 PM CDT Wed Aug 12 2026
Valid 131200Z - 141200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN PARTS OF
SOUTHERN/CENTRAL NEVADA...AND FROM THE FRONT RANGE INTO THE MIDDLE
OHIO VALLEY...
...SUMMARY...
Isolated severe storms are possible on Thursday from the parts of
the southern Great Basin, Colorado Front Range, and central High
Plains into the Ohio Valley.
...Central Plains into Ohio Valley...
Model guidance is uniform in placing early morning convection/MCS in
Iowa. This feature will likely track into parts of the Upper Midwest
as has been the case the past couple of days. What will be lacking
on Thursday will be steep mid-level lapse rates owing to the amount
of recent convective overturning. Secondary to that, the morning
convection will likely move through and airmass north of the
effective surface boundary. Isolated wind damage will be possible,
however. There will be strong heating in Missouri with modest
southwest flow into the surface boundary. There will be a
conditional threat for a supercell or two along the boundary during
the afternoon. Forcing will be weak, however, and this scenario is
uncertain.
As the low-level jet intensifies during the evening, areas of
scattered storms will be possible from the central Plains into the
Upper Midwest. These storms are likely to be at least slightly
elevated. Boundary parallel deep-layer shear will also mean activity
will tend to train/interact along the boundary and be only briefly
supercellular. Isolated large hail and wind damage would be the main
concerns.
...Front Range into central High Plains...
Moist upslope flow on the north/northwest side of the surface low in
the central Plains will promote moderate to locally strong
destabilization within these regions. Deep-layer shear of around 30
kt can be expected along the Front Range. Scattered storms should
develop by the afternoon. The strongest of this activity will be
capable of large hail and severe wind gusts. Near the Sangre de
Cristo/Raton Mesa, additional convection is expected to develop
along the surface boundary with strong heating to the south. Severe
winds would be the main hazard with this activity as it moves north
and east. There is some signal for clustering within some of the
CAMs which would promote a locally greater risk in parts of western
Kansas.
...Nevada...
A broad upper trough along the West Coast will bring modest
southwesterly flow across the southern Sierra. Model guidance
suggests that a shortwave perturbation will be favorably timed with
afternoon heating and help to focus a small cluster of convection
moving off of the higher terrain into parts of central/southern
Nevada. Low-level lapse rates are expected to be steep, particularly
in the lee of the Sierra. Severe wind gusts will be possible with
this activity.
...Northeast...
A broad upper trough with one or more embedded shortwave troughs
will move across the region during the period. A strong mid-level
jet will develop into parts of the northern Mid-Atlantic with
decreasing mid-level flow to the north and east. While some
drying/mixing can be expected, MLCAPE of 500-1000 J/kg is possible
given cold temperatures aloft. The core of the mid-level jet will be
offset from the larger instability. Furthermore, modest subsidence
aloft is apparent in forecast soundings likely due to the region
being in between shortwave troughs during the afternoon. Gusty winds
and small hail are possible with the strongest storms, but severe
potential appears too isolated for probabilities.
...Southeast...
A remnant MCV is possible near the southern Appalachians during the
morning. Models differ in the overall strength of this feature. The
NAM has the most robust circulation, but also weakens it with time.
Moderate to strong buoyancy is expected by the afternoon, but shear
will remain weak. While a few strong to locally severe wind gusts
are possible, confidence in an area of greater
concentration/organization remains quite low at present time.
..Wendt.. 08/12/2026
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0225 PM CDT Wed Aug 12 2026
Valid 141200Z - 151200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE FRONT
RANGE INTO THE MIDWEST...OHIO VALLEY...AND MID-ATLANTIC...
...SUMMARY...
Isolated strong to severe storms are possible from the central High
Plains into parts of the Midwest and Mid-Atlantic on Friday.
...Midwest/Ohio Valley...
Convection is expected to be ongoing during the early morning in
parts of these regions. While these storms will be elevated,
sufficient buoyancy/shear will promote an isolated severe risk with
the strongest storms. Whether afternoon destabilization is enough to
promote additional storm development is not clear. An MCV will
likely be moving into Iowa/Missouri out of the central Plains. This
may help develop afternoon storms in the mid-Mississippi Valley
vicinity. Later in the evening, a strengthening low-level jet should
lead to scattered convection along the boundary. These storms will
again be elevated but still pose some severe risk.
...Front Range into central High Plains...
A similar setup to Thursday will be present on Friday. Low-level
moisture will be maintained up against the higher terrain. Scattered
convection is expected during the afternoon with some activity
eventually moving into the High Plains. Shear will remain rather
modest, but the strongest storms could produce isolated wind/hail.
There is some potential for a more organized cluster to move
eastward during the evening. The structure/location of the low-level
jet varies in model guidance (the NAM focuses the jet core farther
west) which makes this potential uncertain.
...Virginia into northern North Carolina...
An MCV associated with convection in the upper Ohio Valley will move
into parts of the Mid-Atlantic during the afternoon. This feature
combined with moderate mid-level flow within the base of the
Northeast upper trough will allow for a few organized storms. Both
the NAM/ECMWF suggest sufficient destabilization will occur south of
the stationary surface boundary. Wind damage would be the main
hazard with the strongest storms.
..Wendt.. 08/12/2026
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1039 AM CDT Wed Aug 12 2026
Valid 121700Z - 131200Z
Slight adjustments were made to portions of the existing Elevated
areas in agreement with the latest forecast guidance this morning.
Across the southern Plains, the extent of the Elevated area was
expanded a bit in almost every direction. Constraining factors over
central/eastern portions of KS and OK are not only the eastern
progression of the driest RHs, but also a gradient of increasingly
green fuels. Over southwest ID and northern NV, stronger winds are
expected to impact areas slightly farther east from the existing
drawn area. No changes were made to the Isolated Dry Thunder area,
which remains on track as previously described over portions of far
northern ID, MT, and WA.
..Stearns.. 08/12/2026
.PREV DISCUSSION... /ISSUED 1251 AM CDT Wed Aug 12 2026/
...Synopsis...
A mid-level trough will pivot into the Pacific Northwest today as a
broader ridge over much of the West begins to shift eastward.
Moisture advection from the Pacific, falling H500 heights and
subsequent increasing instability will promote thunderstorm
development across northern WA, the ID Panhandle and northwestern MT
this afternoon and evening. Dry and breezy conditions between the
Pacific Northwest trough and more expansive monsoon moisture across
the southern Intermountain West will promote elevated fire weather
concerns across portions of northeastern CA, northwestern NV and the
Upper Snake River Plain. A deepening surface low across central KS
will result in enhanced southerly winds across the Southern Plains
this afternoon. Elevated fire weather concerns remain for portions
of the TX/OK Panhandles, northwestern OK and adjacent portions of
KS/CO.
...Southern Plains...
Enhanced southerly winds within a well mixed boundary layer south of
the surface low across KS will evolve late this morning into the
afternoon. South winds of around 15 mph (locally 20 mph at times)
and low relative humidity during peak heating will promote elevated
fire weather concerns across the southern High Plains. Above normal
temperatures in the lower 100s F will contribute to low afternoon
RH, with increasingly dry conditions farther west across
southeastern CO and eastern NM where RH below 10 percent is
possible. Fuels continue to dry, with ERC values climbing into the
97-99th percentiles under multiple days of triple digit heat and dry
conditions, curing fine fuels. Existing elevated highlights were
shifted slightly westward given latest model/ensemble guidance.
...Northeastern Washington, Idaho Panhandle and Northwestern
Montana...
Showers and thunderstorms are expected to initially develop over
more complex terrain of northern WA, ID Panhandle and northwestern
MT this afternoon as a mid-level trough enters the Pacific
Northwest. Wetting rains are possible under heavier rain cores with
PWAT values nearing 1.00". However, fuels should remain receptive to
potential ignitions outside of these heavier cores. Latest CAM
guidance suggests some lingering thunderstorm potential into the
evening and overnight hours in the northern Columbia Basin, in
addition to increasing east-northeast storm trajectories as the
trough pushes farther into WA. This should limit rainfall
accumulations and support a dry lightning threat for portions of the
northern Columbia Basin where isolated dry thunderstorm highlights
have been extended.
...Northern Great Basin and Upper Snake River Plain of Idaho...
Dry and breezy conditions north of an advancing monsoon moisture
plume across the Southwest will bring elevated fire weather concerns
to northeastern CA, northwestern NV, far southern OR and the Upper
Snake River Plain in ID. West winds of around 15 mph combined with
RH locally below 10 percent amid very dry fuels will support an
elevated fire weather threat today. Elevated highlights were
extended eastward into north-central NV and adjacent OR/ID areas.
...Please see www.spc.noaa.gov/fire for graphic product...
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0300 PM CDT Wed Aug 12 2026
Valid 131200Z - 141200Z
All drawn areas were expanded commensurate with the latest forecast
guidance. Over the southern Plains, the existing Isolated Dry
Thunder area was expanded to accommodate the potential for
additional, primarily nocturnal, convection with minimal
precipitation accumulation. Additionally, the Elevated area was
expanded farther west to include much of the OK/TX Panhandles with
gusty southerly winds and dry air in place ahead of the cold front
during peak heating. The front is anticipated to move into far
northwestern portions of the drawn area around sunset.
Over the western US, the two existing Isolated Dry Thunder areas
were combined and expanded. An area of concern includes the western
periphery of the central Sierra Mountains where the latest forecast
guidance shows convection through the morning and early afternoon
hours aided by a passing subtle shortwave trough. Over central OR,
the majority of the latest forecast guidance shows a few
thunderstorms progressing northeastward through this area amid
background precipitable water values of 0.55-0.75" and storms
motions near 25 mph. Farther east across central portions of the
Snake River Plain in southern ID, precipitable water values and
forecast guidance QPF show higher potential for wetting
precipitation. However, lightning starts could also be more numerous
amid drier fuels, extending the threat to the east. The remainder of
the Isolated Dry Thunder area remains on track.
..Stearns.. 08/12/2026
.PREV DISCUSSION... /ISSUED 1252 AM CDT Wed Aug 12 2026/
...Synopsis...
Mid/upper troughing becomes established along the West Coast while
upper ridging edges eastward towards the Great Plains. An embedded
short wave translating northeastward into CA/NV will bring a few
high-based thunderstorms within a corridor of fringe monsoonal
moisture across portions of the northern Great Basin. Additional
thunderstorms associated with another embedded mid-level
perturbation will affect portions of the Northern Rockies.
...Southern Plains...
Persistent southerly winds south of a surface low across KS will
maintain a fire weather threat into D2/Thursday across portions of
the Southern Plains. South winds of up to 15 mph amid low RH and
exceptionally dry fuels will support a few hours of elevated fire
weather concerns for western OK and eastern TX Panhandle. A diffuse
convergence zone will stretch southwestward from the surface low
across KS. Sufficient mid-level moisture and instability atop a well
mixed and dry sub-cloud boundary layer near this boundary will
support afternoon convection across portions of the TX Panhandle,
northwestern OK and adjacent areas of southern KS Thursday
afternoon. Receptive fuels with ERC values in the 97-99th percentile
range and cured fine fuels could promote a few ignitions outside of
heavier rain cores from these initially high-based thunderstorms.
Downdraft CAPE of 1500 J/kg or greater will evolve as surface
temperatures climb into the lower 100s F yet again, increasing
potential for downburst winds impacting any potential ignitions/new
fire starts. Introduced isolated dry thunderstorm highlights to
cover this threat.
...Northern Great Basin and Northern Rockies...
A mid-level short wave will translate into the Great Basin Thursday,
interacting with more diffuse monsoon moisture where PWATs in the
0.6-0.9" range settle across the northern Great Basin. Isolated
high-based thunderstorms are expected to evolve Thursday afternoon
across northeastern CA into southeastern OR, far northwestern NV and
southwestern ID. New ignitions are possible outside more intense
rain cores with ERCs still in the 90-95th percentile. Another
mid-level wave will promote convection across portions of the
Northern Rockies. Northeastward storm trajectories up to 30 mph will
limit rainfall in some thunderstorms, increasing ignition potential
over dry fuels. Some modifications were made to these highlighted
areas based on latest model guidance but largely remain intact.
...Please see www.spc.noaa.gov/fire for graphic product...
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