WW 580 SEVERE TSTM IA NE 130630Z - 131300Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 580
NWS Storm Prediction Center Norman OK
130 AM CDT Thu Aug 13 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Western Iowa
Eastern Nebraska
* Effective this Thursday morning from 130 AM until 800 AM CDT.
* Primary threats include...
Scattered damaging winds and isolated significant gusts to 85
mph likely
Isolated large hail events to 1 inch in diameter possible
SUMMARY...A severe linear thunderstorm cluster will continue east
into the Watch area during the overnight and move east into western
Iowa during the early morning. Scattered severe gusts 60 to 85 mph
are expected with the more intense portions of the squall line.
The severe thunderstorm watch area is approximately along and 55
statute miles north and south of a line from 45 miles west of
Columbus NE to 65 miles east southeast of Denison IA. 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 579...
AVIATION...A few severe thunderstorms with hail surface and aloft to
1 inch. Extreme turbulence and surface wind gusts to 75 knots. A few
cumulonimbi with maximum tops to 550. Mean storm motion vector
27040.
...Smith
WW 0580 Status Updates
STATUS REPORT ON WW 580
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 WSW LNK
TO 5 N OLU TO 20 NNE OFK.
..KERR..08/13/26
ATTN...WFO...DMX...OAX...FSD...
STATUS REPORT FOR WS 580
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
IAC001-003-009-025-027-029-047-073-077-085-093-129-133-137-155-
161-165-175-193-130940-
IA
. IOWA COUNTIES INCLUDED ARE
ADAIR ADAMS AUDUBON
CALHOUN CARROLL CASS
CRAWFORD GREENE GUTHRIE
HARRISON IDA MILLS
MONONA MONTGOMERY POTTAWATTAMIE
SAC SHELBY UNION
WOODBURY
NEC021-023-025-037-039-043-051-053-055-109-153-155-159-167-173-
177-179-130940-
NE
. NEBRASKA COUNTIES INCLUDED ARE
BURT BUTLER CASS
COLFAX CUMING DAKOTA
DIXON DODGE DOUGLAS
LANCASTER SARPY SAUNDERS
WW 0579 Status Updates
STATUS REPORT ON WW 579
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 10 N HSI TO
20 SE ONL TO 35 ESE ONL AND 10 NNE EAR TO 10 NNW EAR.
REMAINING VALID PORTION OF WW WILL PROBABLY BE ALLOWED TO EXPIRE AS
SCCHEDULED AT 13/08Z.
..KERR..08/13/26
ATTN...WFO...LBF...GID...
STATUS REPORT FOR WS 579
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
NEC121-125-143-130800-
NE
. NEBRASKA COUNTIES INCLUDED ARE
MERRICK NANCE POLK
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 1964 CONCERNING SEVERE THUNDERSTORM WATCH 580... FOR PARTS OF EAST CENTRAL NEBRASKA THROUGH CENTRAL IOWA
Mesoscale Discussion 1964
NWS Storm Prediction Center Norman OK
0242 AM CDT Thu Aug 13 2026
Areas affected...parts of east central Nebraska through central Iowa
Concerning...Severe Thunderstorm Watch 580...
Valid 130742Z - 130945Z
The severe weather threat for Severe Thunderstorm Watch 580
continues.
SUMMARY...Strongest gusts are likely to continue in at least a
narrow swath across east central Nebraska, and the Missouri River
vicinity between Omaha and Tekamah, into the I-80 corridor of
western Iowa through 4-5 AM CDT.
DISCUSSION...The most intense convection remains concentrated near a
new MCV evolving from an initial supercell now approaching the
Norfolk vicinity, with an intense westerly rear inflow jet in excess
of 80 kt still being sampled, at least in mid-levels in recent radar
imagery. Based on its current storm motion, it still appears on
track to reach the Missouri River vicinity near/north of Omaha into
the Tekamah vicinity by around 09Z. Although latest objective
analysis suggests that the magnitude of potentially unstable inflow
could gradually begin to weaken along or just north of the I-80
corridor into central Iowa, it still seems probable that activity
could maintain severe strength into the Greater Des Moines vicinity
by around 11-12Z.
..Kerr.. 08/13/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DMX...OAX...GID...
LAT...LON 41759762 41849759 41959528 41379514 41299733 41309783
41519749 41759762
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...UP TO 1.25 IN
SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Thu Aug 13 2026
Valid 131200Z - 141200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
IOWA INTO ILLINOIS...
...SUMMARY...
Isolated to scattered severe thunderstorms appear possible today
from parts of the southern/central High Plains to the mid
Mississippi and lower Ohio Valleys. Damaging winds should be the
main threat, but occasional hail may also occur.
...Iowa into Illinois/Indiana...
An MCV has developed early this morning with an ongoing cluster of
thunderstorms across central NE. This activity is expected to spread
eastward through the morning, and should be in the vicinity of
western/central IA by the start of the period. There is still
uncertainty regarding how intense this cluster will be due to the
presence of fairly substantial MLCIN downstream into IA. Even so,
warm/moist advection associated with a low-level jet over the
southern/central Plains and the presence of a rather moist/unstable
airmass into IA suggest some potential for an organized cluster to
pose a risk for scattered severe/damaging winds as it moves eastward
through the morning. A brief embedded tornado may also occur if
convection can remain surface based.
Even greater uncertainty exists this afternoon regarding potential
convective evolution, with most guidance showing the cluster
weakening as it moves into IN. Regardless, the airmass downstream
and to the south of outflow associated with the morning cluster will
destabilize through the day, and any additional thunderstorms that
form could pose at least an isolated threat for damaging winds and
perhaps some hail given the strong buoyancy forecast.
...Southern/Central High Plains...
High-based thunderstorms are forecast to initially develop over the
higher terrain of the central Rockies/Front Range this afternoon,
with post-frontal low-level upslope flow persisting across the
central High Plains. As this activity spreads east-northeastward and
encounters greater instability, consolidating outflows should
support some increase for isolated severe gusts given steepened
low-level lapse rates. Occasional hail may also occur with the
stronger cores that develop. Consideration was given to including
greater severe wind probabilities across eastern CO into parts of
KS, but modest deep-layer shear casts some doubt on overall
thunderstorm organization/intensity. A somewhat separate area of
thunderstorms may also develop farther south across the southern
High Plains in a very hot and well-mixed boundary layer. This
activity should also pose a threat for isolated severe gusts through
the afternoon.
...Great Basin...
Modestly enhanced southwesterly mid-level flow will persist today
across the Great Basin downstream of a weak mid-level trough over
CA. Weak to locally moderate instability is forecast to develop
through the afternoon as filtered diurnal heating occurs. Scattered
to numerous thunderstorms are expected to form and spread
northeastward across this destabilizing airmass, with strong to
severe gusts possible. Based on latest guidance trends (00Z HREF),
have expanded the Marginal Risk for severe/damaging winds to include
more of the Great Basin.
...Northeast...
Seasonably cool mid-level temperatures are forecast today across
parts of the Northeast, with a mid-level trough expected to move
east-southeastward from Quebec into New England. While instability
is forecast to remain fairly limited, strong west-northwesterly flow
aloft may support a risk for isolated damaging winds with
thunderstorms that develop and spread southeastward through the
afternoon. Isolated hail may also occur with the stronger cells.
..Gleason/Moore.. 08/13/2026
SPC 0600Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Thu Aug 13 2026
Valid 141200Z - 151200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
HIGH PLAINS EASTWARD INTO PARTS OF 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, Ohio Valley, and Mid-Atlantic on
Friday.
...Synopsis...
An upper ridge initially covering parts of the lower MS Valley and
Southeast is forecast to build northward on Friday. Despite the
building ridge, multiple MCVs may traverse the periphery of the
ridge, helping to focus strong to locally severe storm development
within a moist and unstable environment extending from the central
Plains into the Midwest, Ohio Valley, and Mid-Atlantic/Carolinas.
...Ohio Valley into parts of the Mid-Atlantic...
Elevated convection and possibly a remnant MCS may be ongoing Friday
morning across parts of the Ohio Valley. Guidance varies regarding
the organization/intensity of this morning convection, and whether
it is associated with a well-defined MCV. In general, an isolated
wind-damage threat could accompany the morning convection before it
weakens, with some rejuvenation of wind-damage potential possible
into parts of the Mid-Atlantic and NC, in conjunction with diurnal
heating/destabilization. Some clustering and locally greater
wind-damage potential may evolve across some part of the region, but
uncertainty remains rather high regarding the details.
The 12/00Z NAM is an aggressive outlier, depicting a strong MCV
approaching the Mid-Atlantic region during the afternoon, and
substantial destabilization farther north across the Mid-Atlantic
compared to other guidance. While confidence in this particular
scenario is low, some expansion was made to the Marginal Risk across
the Mid-Atlantic and NC, to account for uncertainty regarding the
most favored corridor.
...East-central Plains into the Midwest...
Elevated convection will also likely be ongoing Friday morning from
eastern NE into parts of IA/IL and vicinity. An isolated severe
threat cannot be ruled out with this convection, though early-day
storms may tend to diminish in conjunction with a weakening
warm-advection regime.
In the wake of morning convection, moderate to strong buoyancy is
expected to develop near/north of the outflow-influenced frontal
zone during the afternoon, aided by rich low-level moisture. Veering
low-level wind profiles near/north of the front will result in
favorable effective SRH, though mid/upper-level flow will be modest
at best and may weaken somewhat with height.
Most guidance suggests an MCV may emerge from the central High
Plains and move along the periphery of the ridge through the
afternoon/evening, though the timing and trajectory of such a
feature remains uncertain. Any MCV-related uptick in storm coverage
would result in a greater potential for organized severe storms.
Otherwise, isolated strong to severe storms will still be possible.
The favorable effective SRH could support initial supercell
development, with some potential for all severe hazards. The weak to
modest mid/upper-level flow could result in a quick transition to
more of a cluster mode, potentially increasing wind-damage
potential.
...CO Front Range into the central High Plains...
Low-level east/southeasterly flow will again promote moderate
destabilization and scattered storm development in the vicinity of
the CO Front Range Friday afternoon. Deep-layer flow/shear will
generally be weak to modest, but the strongest cells may become
capable of producing isolated hail and localized severe gusts.
Farther south/east, high-based convection may develop into parts of
the south-central High Plains, within a hot and well-mixed
environment. Localized severe gusts could accompany these high-based
storms.
Friday evening into the overnight, expanding outflow and an
increasing low-level jet may allow for one or more upscale-growing
clusters to develop and move across western KS (and perhaps
southwest NE). The intensity and longevity of any such clusters
could be limited by weak mid/upper-level flow, but some threat for
strong to severe gusts could persist into early Saturday morning.
..Dean.. 08/13/2026
SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CDT Thu Aug 13 2026
Valid 151200Z - 161200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
HIGH PLAINS INTO PARTS OF THE MIDWEST AND OHIO
VALLEY...SOUTHERN/CENTRAL APPALACHIANS...AND CAROLINAS...
...SUMMARY...
Strong to locally severe storms are possible on Saturday from the
central High Plains eastward into parts of the Midwest, Ohio Valley,
southern/central Appalachians, and Carolinas.
...Synopsis...
An upper ridge is forecast to remain anchored over parts of the
southern Plains and lower MS Valley vicinity on Saturday. A
warm-frontal zone initially extending from IA into the OH Valley is
forecast to move northward as a warm front, while the western
extension of this front may remain nearly stationary across the
central Plains. Farther north, a weak surface low is forecast to
move across northern MN, as a trailing cold front begins to move
southeastward across parts of the Dakotas and eventually into parts
of MN/IA/NE.
...Central High Plains eastward into parts of the Midwest/Ohio
Valley...
Another day of at least isolated severe potential is evident on
Saturday along the periphery of the upper ridge. However,
predictability is typically low regarding the details within this
regime, and generally modest midlevel lapse rates and deep-layer
shear may tend to limit the magnitude of severe potential. A broad
Level-1/Marginal Risk has been included where the greatest relative
severe potential is currently expected, though confidence in the
details is low.
Despite the relatively modest lapse rates, rich low-level moisture
will again support moderate to strong buoyancy near and north of the
front extending from the central High Plains into parts of the
Midwest/Ohio Valley. Given the generally modest deep-layer
flow/shear and nebulous large-scale ascent, any greater organized
severe potential may be dependent on optimally timed MCVs moving
along the periphery of the ridge.
Early-day convection across IA/MO may pose some severe threat,
especially if any storm cluster is able to propagate along the
frontal zone into parts of the OH Valley. Some guidance suggests
that an MCV may develop across the central High Plains late
D2/Friday and move east-northeastward across parts of NE/IA/southern
MN through the day Saturday, which may aid in storm development
near/north of the front during the afternoon/evening.
Farther west, diurnal storm development is again expected in the CO
Front Range vicinity, which could result in some storm clustering as
convection moves across the central High Plains Saturday night.
Given the favorable low-level moisture and buoyancy, the strongest
storms within any of these regimes could pose a threat for damaging
winds and perhaps isolated hail, though it is also possible that the
bulk of convection remains somewhat disorganized, due to relatively
weak deep-layer flow/shear.
...Southern/central Appalachians and Carolinas...
Modest northwesterly mid/upper-level flow will overspread a moist
and moderately unstable environment across parts of the
southern/central Appalachians and Carolinas during the afternoon. A
few stronger cells/clusters capable of damaging wind will be
possible within this regime.
..Dean.. 08/13/2026
SPC Day 1 Fire Weather Outlook
Day 1 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
1249 AM CDT Thu Aug 13 2026
Valid 131200Z - 141200Z
...Synopsis...
Upper troughing present along the West Coast, monsoon moisture
entrenched across much the Intermountain West, and daytime
instability will support a broad region of showers and thunderstorms
across the much of the western U.S. today. Convection on the fringes
of the monsoon moisture will be higher based and less likely to
produce appreciable rainfall across portions of the Sierra Nevada
and northern CA, northern Great Basin into the northern Rockies of
ID and far northwestern MT. A surface low and attendant frontal
boundary across the Kansas will bolster southerly winds across the
Southern Plains. The hot, dry and breezy south winds will bring an
elevated fire weather concern to portions of the TX Panhandle,
western OK and adjacent southern KS. An additional fire weather
threat of isolated afternoon high-based thunderstorms is forecast
across portions of the TX Panhandle into northwestern OK and
southern KS.
...Northern California, southeastern OR into ID and far northwest
MT...
Some minor expansion of isolated dry thunderstorm highlights were
made into the Siskiyous of northern CA. Increasing daytime
instability along with some lift provided from troughing along the
coast should support isolated convection across higher terrain of
northern CA this afternoon. A more pronounced short wave moving
northeastward into central CA could similarly aid in thunderstorm
development across the central Sierra Nevada range this afternoon.
Peripheral monsoon moisture with PWATs ranging from 0.70-0.90" will
inhibit considerable surface rainfall with passing showers and
thunderstorms across much of OR, western ID and into northwestern MT
this afternoon and evening. Fuels remain quite receptive with some
new ignitions possible. The existing isolated dry thunderstorm
threat remains largely in place.
...Southern Plains...
A slowly strengthening surface low currently in southeastern CO will
shift into central KS later today. This should sustain modest
southerly winds through the morning hours across portions of north
TX and western OK. Sustained south winds will accelerate back to 15
mph (locally 20 mph) by early afternoon. These winds combined with
low RH in the lower teens, hot surface temperatures in the lower
100s and exceptionally dry fuels will support an elevated fire
weather conditions this afternoon across portions of the TX
Panhandle, western OK and adjacent southern KS. Elevated highlights
were extended farther north into southern KS based on latest model
guidance and a potentially delayed cold front. The intense surface
heating and subsequent instability, along with a subtle embedded
mid-level wave will support a corridor of high-based convection
across the TX Panhandle, northeastward into southern KS. Strong
outflow winds emanating from slow moving/collapsing thunderstorms
could exacerbate any new fire starts from lightning. No significant
changes to the isolated dry thunderstorm highlights were made.
..Williams.. 08/13/2026
...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
1251 AM CDT Thu Aug 13 2026
Valid 141200Z - 151200Z
...Synopsis...
Troughing will remain along the West Coast while upper ridging will
continue to edge eastward into the Upper Midwest and Deep South for
D2/Friday. This troughing along with monsoon moisture across much of
the West should bring another round of isolated afternoon showers
and thunderstorms to the northwest CA mountains into southwestern
and central OR. Persistent dry and breezy conditions south of a
surface trough and attendant frontal boundary across the central
plains will bring elevated fire weather concerns to portions of the
Southern Plains.
...Southern Plains...
Relentless heat with highs in the lower 100s will result in RH
reductions to 15-20 percent by Friday afternoon. Breezy southerly
winds of 15-20 mph south of a lingering surface trough across the
Central Plains will present an elevated fire weather threat to
portions of northwestern TX and western OK as very dry fuels remain
across the region. A corridor of thunderstorms in proximity to a
diffuse frontal boundary is expected to evolve over the TX/OK
Panhandles and northeastward into southern KS. However, the
sub-cloud boundary layer could be modified by convection on
D1/Thursday, inhibiting the overall threat of additional dry
thunderstorms.
...Northwest California and southwest/central Oregon...
An isolated dry thunderstorm threat exists for portions of
northwestern CA and OR Friday. Upper-level troughing across the West
Coast, monsoon moisture and increasing instability will likely bring
isolated convection back into the mountains of northwestern CA,
Oregon Cascades and central OR. PWATs generally below 0.90" and
faster northeastward thunderstorm trajectories bolstered by a
mid-level wave moving towards the Cascades, will promote limited
rainfall in some locations. Although monsoon moisture will generally
improve fuels over the next several days, ERC values still nearing
the 90th percentile and should promote the potential for new
ignitions Friday.
..Williams.. 08/13/2026
...Please see www.spc.noaa.gov/fire for graphic product...
|
