WW 584 SEVERE TSTM CO NE WY 152005Z - 160300Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 584
NWS Storm Prediction Center Norman OK
205 PM MDT Sat Aug 15 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Eastern Colorado
Western Nebraska
Eastern Wyoming
* Effective this Saturday afternoon and evening from 205 PM until
900 PM MDT.
* Primary threats include...
Scattered large hail events to 1.5 inches in diameter possible
Isolated damaging wind gusts to 70 mph possible
SUMMARY...Widely scattered strong to severe thunderstorms are
expected to develop, initially near the urban/I-25 corridor, and
gradually spread eastward into this evening, with bouts of severe
hail and locally damaging winds as the primary hazards.
The severe thunderstorm watch area is approximately along and 205
statute miles north and south of a line from 70 miles northwest of
Limon CO to 30 miles east southeast of Akron CO. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU4).
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 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
28025.
...Guyer
WW 0584 Status Updates
STATUS REPORT ON WW 584
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
FOR ADDITIONAL INFORMATION SEE MESOSCALE DISCUSSION 1992
..THORNTON..08/15/26
ATTN...WFO...BOU...PUB...CYS...
STATUS REPORT FOR WS 584
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
COC001-005-009-011-025-035-039-041-061-071-073-075-087-089-099-
101-121-123-160040-
CO
. COLORADO COUNTIES INCLUDED ARE
ADAMS ARAPAHOE BACA
BENT CROWLEY DOUGLAS
ELBERT EL PASO KIOWA
LAS ANIMAS LINCOLN LOGAN
MORGAN OTERO PROWERS
PUEBLO WASHINGTON WELD
NEC007-013-033-045-105-123-157-165-160040-
NE
. NEBRASKA COUNTIES INCLUDED ARE
BANNER BOX BUTTE CHEYENNE
DAWES KIMBALL MORRILL
SCOTTS BLUFF SIOUX
MD 1992 CONCERNING SEVERE THUNDERSTORM WATCH 584... FOR EASTERN COLORADO/WYOMING INTO WESTERN KANSAS
Mesoscale Discussion 1992
NWS Storm Prediction Center Norman OK
0608 PM CDT Sat Aug 15 2026
Areas affected...eastern Colorado/Wyoming into western Kansas
Concerning...Severe Thunderstorm Watch 584...
Valid 152308Z - 160115Z
The severe weather threat for Severe Thunderstorm Watch 584
continues.
SUMMARY...Severe threat continues within WW584.
DISCUSSION...Several clusters of storms and a few more isolated
supercells continue within WW584. A supercell near Denver had
reports of 64 mph winds and hail up to 1.75 inches in diameter.
Large hail and damaging wind will continue to be possible with
supercells through the early evening, given moderate instability and
35-45 kts of effective shear. With cell interactions, mode is
gradually shifting to become more clustered/multi-cell this evening.
Guidance suggests that one or more clusters may evolve eastward into
western Kansas through the evening.
Downstream across western Kansas, steep low to mid-level lapse
rates, temperatures in the mid 80s to low 90s F, and dew points in
the upper 60s to 70s are supporting moderate to strong instability,
though lingering inhibition remains. Should a cluster be able to
organize along a cold pool and shift eastward, damaging wind
potential may increase into the evening. A downstream watch will
probably be needed into western Kansas later this evening.
..Thornton/Gleason.. 08/15/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LBF...DDC...UNR...GLD...AMA...PUB...BOU...CYS...
ABQ...
LAT...LON 36910425 37550483 39000497 40280485 42560523 42940498
42990396 43020344 42950284 42410274 40780274 40530261
40120222 40100201 39680174 38940154 38330145 37650138
37050146 36920174 37010218 36950353 36910425
MOST PROBABLE PEAK WIND GUST...65-80 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0241 PM CDT Sat Aug 15 2026
Valid 152000Z - 161200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE
OHIO VALLEY AND PARTS OF THE CENTRAL HIGH PLAINS...
...SUMMARY...
Thunderstorms with severe wind gusts and isolated large hail remain
possible from late afternoon into the evening across the central
High Plains. Severe wind gusts may also still occur this afternoon
through early evening across parts of the Ohio Valley and Southeast.
...20Z Update...
The previous forecast (see below) remains generally on track, with
only minor changes made to the 20Z Day 1 Convective Outlook Update
to reflect the latest observations and latest guidance consensus.
There were considerations to add a Category 1/Marginal Risk for
severe wind/hail over portions of the Pacific Northwest into the
northern Rockies given appreciable cool temperatures aloft
overspreading a heated boundary layer. Nonetheless, vertical wind
shear should remain quite weak. Therefore, while a 50+ kt gust or
instance of 1+ inch hail may occur with any of the stronger storms,
the severe threat should be very sparse, precluding severe
probabilities this outlook.
..Squitieri.. 08/15/2026
.PREV DISCUSSION... /ISSUED 1135 AM CDT Sat Aug 15 2026/
...Front Range/Central High Plains...
Modestly strong southwesterly flow aloft coupled with strong
daytime heating, low-level upslope flow, and orographic lift will
support another day of thunderstorms regionally. These thunderstorms
should gradually move off the higher terrain into the central High
Plains later this afternoon, where a moderately
buoyant airmass will be in place. Around 30-35 kt of effective
bulk shear is expected over the region, which will support a mixed
mode with supercells and multicell line segments. Isolated large
hail is possible with any supercells, while severe wind gusts will
be possible with both supercells and line segments. The severe
threat should persist into the evening as this complex of storms
moves eastward through the central High Plains including
west/southwest Kansas.
...Midwest/Middle Ohio Valley...
Thunderstorms have generally weakened since the overnight, although
scattered showers/some thunderstorms and plentiful cloud cover
continue in areas progressively north of the Ohio River. An MCV is
readily apparent in observational data as it continues to move into
northwest Indiana, with an enhanced belt (40+ kt) of westerly winds
associated with the MCV per regional WSR-88D VWP data.
As clouds thin/abate, a gradual increase in renewed thunderstorm
coverage and intensity is expected later this afternoon. Mid-level
lapse rates will be poor, but dewpoints in the 70s F will support
moderate buoyancy, particularly in areas where cloud cover does not
overly inhibit diurnal heating, which will tend to generally be
southward toward the Ohio River. Strong updrafts and high
precipitable water will support the potential for wet microbursts
capable of producing damaging gusts, and some enhancement to the
low-level winds could also yield a brief tornado.
...Central Appalachians/Carolinas/Georgia...
A very moist airmass, characterized by dewpoints in the low to mid
70s, is in place regionally. Strong heating will destabilize the
airmass by the early afternoon, resulting in a large reservoir of
moderate buoyancy. Thunderstorm development is anticipated within
this destabilized airmass across the higher terrain of the central
Appalachians as well as any area of low-level convergence across the
remainder of the region. Vertical shear will be weak, and limited
storm organization is anticipated. Even so, the moderate buoyancy
could still support updrafts/downdrafts strong enough to produce
occasional damaging gusts.
...Central Plains/Mid Missouri Valley to Mid Mississippi Valley...
Elevated thunderstorms are expected again tonight, initiated by both
an approaching cold front and warm-air advection. Ample low-level
moisture and moderate buoyancy will be in place, but vertical shear
will be marginal. Isolated strong to severe storms are expected, but
a predominantly elevated and clustered storm mode should limit the
overall severe potential.
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0230 PM CDT Sat Aug 15 2026
Valid 171200Z - 181200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE
NORTHERN PLAINS...
...SUMMARY...
Strong to severe thunderstorms are possible Monday afternoon and
evening across portions of the northern and central Plains, and
parts of the southern Appalachians/Carolinas.
...Central to Northern Plains...
As an upper low moves into northern Ontario, gradual height falls
will occur into the northern Plains on Monday. Midlevel
northwesterlies of 40-50 kt will be common over the Dakotas and MN,
with 30 kt flow southward toward I-80. A cold front will move across
the Dakotas and into MN, with the front stalling over NE. Dewpoints
in the 60s, strong heating and steep lapse rates will favor areas of
moderate instability ahead of the front, with storms developing late
afternoon. Scattered cells may produce large hail along this
boundary, with an additional threat of damaging winds and possibly
evening MCS over NE.
...Southern Appalachians into the Carolinas...
Mid to high level winds of 20-30 kt will remain over the region on
Monday, with relatively warm temperatures aloft. Still, substantial
moisture will remain in place, with areas of moderate instability
developing as the surface trough deepens. An uncapped air mass and
convergence along the wind shift will support scattered afternoon
storms, and some may produce locally damaging gusts as they travel
southeastward through the evening.
..Jewell.. 08/15/2026
SPC Day 2 Fire Weather Outlook
Day 2 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0213 PM CDT Sat Aug 15 2026
Valid 161200Z - 171200Z
...NO CRITICAL AREAS...
No changes were made to the Day 2 Fire Weather Outlook; please see
the previous discussion for more information.
..Elizalde-Garcia.. 08/15/2026
.PREV DISCUSSION... /ISSUED 0140 AM CDT Sat Aug 15 2026/
...Synopsis...
The upper ridge over the central US is forecast to flatten Sunday as
the western US trough and a weak subtropical disturbance move across
the northern periphery. This will help force the stalled front over
the Plains southward. Showers and thunderstorms will remain likely
over the Intermountain West and across the Southern Plains where
monsoon moisture remains.
...Southern Plains...
The stalled front over the Plains is forecast to move southward
Sunday with showers and storms developing along it across parts of
the TX Panhandle into OK. These storms may develop over ares of very
dry fuels with the potential for lightning. While some risk for
strikes is possible, slow storm speeds and increasing moisture along
the front suggest limited potential for dry storms.
...Northwest and northern Rockies...
Another day of showers and storms is likely Sunday as the upper
trough moves eastward and monsoon moisture remains in place. Several
days of preceding storms will limit available dry fuels.
Additionally, slower storm speeds will favor a wetter storm mode
over areas that have received substantial wetting rains. This will
limit ignition potential. However, sporadic strikes are still
possible within locally more receptive fuels from eastern OR/WA into
parts of ID.
...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
0457 PM CDT Sat Aug 15 2026
Valid 171200Z - 231200Z
...Synopsis...
Mid/upper troughing near the West Coast will wane as the upper ridge
across the central US retrogrades westward by Day 3/Monday, allowing
drier conditions to infiltrate much of the Great Basin and Cascades.
A mid-level short wave arriving early next week along with residual
monsoonal moisture could bring additional thunderstorms to portions
of the Northern Rockies Day 3/Monday, while also promoting dry and
breezy conditions across portions of the northern Great Basin.
Extended guidance indicates a pattern shift late week as eastern
Pacific troughing impinges upon the Northwest, bringing additional
fire weather concerns. Forecast uncertainty increases Day 7/Friday
onward as ensemble spread reduces predictability in the longer term
across the western CONUS.
...Day 3/Monday...
...Central Idaho and the Northern Rockies...
As a mid-level shortwave enters the Northwest, lingering monsoonal
moisture and daytime heating will promote a favorable convective
environment across portions of the Northern Rockies, central ID and
perhaps into northeastern OR on Day 3/Monday. However, preceding
days of showers and thunderstorms and good overnight RH recoveries
could temporarily reduce fuel receptiveness leading up to this
event, precluding dry thunderstorm probabilities.
...Northeastern California, southern Oregon and northwestern
Nevada...
The aforementioned shortwave and attendant mid-level speed max will
likely bring dry and breezy conditions to parts of the northern
Great Basin into northeastern CA on Day 3/Monday. A relative minimum
of rainfall has been observed in this area over the last several
days of monsoon-related showers and thunderstorms across the broader
western CONUS. A warming and drying trend is expected with the
arrival of stronger west/southwest winds. Forecast meteorological
conditions amid existing dry fuels will increase fire weather
concerns, where 40% Critical probabilities were maintained.
...Day 4/Tuesday...
...Southern Plains...
Expanding drought and continued above normal 100+ F temperatures
will most likely stay in place through next week across portions of
the Southern Plains. Increasing southerly winds are expected to
evolve south of a nascent Central Plains surface low/trough over
portions of northwest TX and western OK. South winds of 15-20 mph
collocated with low afternoon RH and very dry fuels will bring
enhanced fire weather concerns to the area on Day 4/Tuesday.
...Portions of the Columbia Basin...
A split-flow regime consisting of west-northwesterly flow over
northern WA and southwesterly flow over Oregon will increase winds
in gap flow and terrain favored areas east of the Cascades on Day
4/Tuesday. RH values should decrease to 25% or less amid enhanced
wind gusts of 25-30 mph within an environment that did not receive
accumulating rainfall, despite preceding days of thunderstorm
activity. 40% Critical probabilities were introduced to account for
this threat.
...Days 6-7/Thursday-Friday - Northeastern California, southern
Oregon and northwestern Nevada...
As upper ridging expands into the Great Basin late week, an upper
low will progress towards the West Coast and introduce stronger
south-southwesterly flow over the Pacific Northwest. Despite some
differences in extended guidance, the evolution of upper troughing
depicts a favorable pattern for dry and breezy conditions to overlap
very dry fuels across northeastern CA, southern OR, and northwestern
NV; thus, 40% Critical probabilities were introduced. In addition,
embedded disturbances within the troughing pattern may increase
thunderstorm potential as monsoonal moisture advects northward.
..Elizalde-Garcia.. 08/15/2026
...Please see www.spc.noaa.gov/fire for graphic product...
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