WW 239 SEVERE TSTM CO NE 212055Z - 220400Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 239
NWS Storm Prediction Center Norman OK
255 PM MDT Thu May 21 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Northeast Colorado
Nebraska Panhandle
* Effective this Thursday afternoon and evening from 255 PM until
1000 PM MDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Isolated damaging wind gusts to 70 mph possible
A tornado or two possible
SUMMARY...Thunderstorms will develop this afternoon and spread
eastward across the watch area. A few supercells are possible,
posing a risk of large hail. A tornado or two is possible by early
evening as storms track into the eastern half of the watch.
The severe thunderstorm watch area is approximately along and 50
statute miles east and west of a line from 55 miles north northwest
of Sidney NE to 50 miles southwest of Burlington CO. 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 238...
AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
28030.
...Hart
WW 238 SEVERE TSTM CO KS NM OK TX 211920Z - 220300Z
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 238
NWS Storm Prediction Center Norman OK
220 PM CDT Thu May 21 2026
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Southeast Colorado
Southwest Kansas
Northeast New Mexico
Western Oklahoma Panhandle
Northwest Texas Panhandle
* Effective this Thursday afternoon and evening from 220 PM until
1000 PM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Isolated damaging wind gusts to 70 mph possible
A tornado or two possible
SUMMARY...Thunderstorms developing off the higher terrain of
northeast New Mexico will build eastward across the watch area
through the afternoon and evening. Large hail is the main concern
with the strongest cells.
The severe thunderstorm watch area is approximately along and 75
statute miles east and west of a line from 15 miles northeast of
Lamar CO to 40 miles south southwest of Clayton NM. 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.
&&
AVIATION...A few severe thunderstorms with hail surface and aloft to
2 inches. Extreme turbulence and surface wind gusts to 60 knots. A
few cumulonimbi with maximum tops to 500. Mean storm motion vector
27030.
...Hart
WW 0239 Status Updates
STATUS REPORT ON WW 239
THE SEVERE WEATHER THREAT CONTINUES ACROSS THE ENTIRE WATCH AREA.
..KERR..05/21/26
ATTN...WFO...GLD...BOU...CYS...
STATUS REPORT FOR WS 239
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
COC017-039-063-073-075-087-121-125-220040-
CO
. COLORADO COUNTIES INCLUDED ARE
CHEYENNE ELBERT KIT CARSON
LINCOLN LOGAN MORGAN
WASHINGTON YUMA
NEC007-033-105-123-220040-
NE
. NEBRASKA COUNTIES INCLUDED ARE
BANNER CHEYENNE KIMBALL
MORRILL
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 0238 Status Updates
STATUS REPORT ON WW 238
SEVERE WEATHER THREAT CONTINUES RIGHT OF A LINE FROM 35 WSW DHT
TO 20 ESE SPD TO 30 ENE LAA.
..KERR..05/22/26
ATTN...WFO...PUB...DDC...ABQ...AMA...
STATUS REPORT FOR WS 238
SEVERE WEATHER THREAT CONTINUES FOR THE FOLLOWING AREAS
COC009-220140-
CO
. COLORADO COUNTIES INCLUDED ARE
BACA
KSC067-075-093-129-187-189-220140-
KS
. KANSAS COUNTIES INCLUDED ARE
GRANT HAMILTON KEARNY
MORTON STANTON STEVENS
OKC025-139-220140-
OK
. OKLAHOMA COUNTIES INCLUDED ARE
CIMARRON TEXAS
MD 0821 CONCERNING SEVERE THUNDERSTORM WATCH 239... FOR PARTS OF SOUTHWESTERN NEBRASKA...NORTHEAST AND EAST CENTRAL COLORADO...ADJACENT NORTHWESTERN KANSAS
Mesoscale Discussion 0821
NWS Storm Prediction Center Norman OK
0616 PM CDT Thu May 21 2026
Areas affected...parts of southwestern Nebraska...northeast and east
central Colorado...adjacent northwestern Kansas
Concerning...Severe Thunderstorm Watch 239...
Valid 212316Z - 220115Z
The severe weather threat for Severe Thunderstorm Watch 239
continues.
SUMMARY...Isolated to widely scattered supercell development is
likely to persist through 6-8 PM MDT, accompanied by the risk for
large hail and perhaps some increase in potential for a tornado near
the Colorado/Kansas state border to the west-northwest of Goodland.
DISCUSSION...Isolated thunderstorm development has undergone notable
intensification the past few hours, aided by destabilization
associated with continued boundary-layer warming and moistening.
This appears to have contributed to CAPE on the order of 1000-1500,
in the presence of strong westerly deep-layer shear, though with
mean ambient winds on the order of 20-30 kt, due to the veering of
winds with height.
Of the ongoing storms, the prominent supercell to the
north-northeast of Limon CO appears to have the longest access to
unstable inflow as it propagates eastward toward the Kansas state
border to the west-northwest of Goodland through 7-8 PM MDT. It
appears that this may coincide with enlarging low-level hodographs
accompanying strengthening east-southeasterly 850 mb flow, which may
promote some further increase in potential for a tornado or two.
..Kerr.. 05/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...GLD...BOU...CYS...
LAT...LON 39890379 40800380 41420371 40840280 39750194 39040262
39020312 39380365 39890379
MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
MOST PROBABLE PEAK WIND GUST...55-70 MPH
MOST PROBABLE PEAK HAIL SIZE...1.50-2.50 IN
MD 0820 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PORTIONS OF EASTERN NEW MEXICO INTO THE WESTERN TEXAS PANHANDLE
Mesoscale Discussion 0820
NWS Storm Prediction Center Norman OK
0610 PM CDT Thu May 21 2026
Areas affected...portions of eastern New Mexico into the western
Texas Panhandle
Concerning...Severe potential...Watch unlikely
Valid 212310Z - 220045Z
Probability of Watch Issuance...20 percent
SUMMARY...Isolated large hail will remain possible with ongoing
thunderstorms for another couple of hours. Watch issuance remains
unlikely.
DISCUSSION...Several ongoing thunderstorms are noted within a narrow
corridor of locally greater surface-based buoyancy (1000-1500 J/kg
MLCAPE per latest objective analysis) on the cool side of a
quasi-stationary surface boundary where low-level moisture is
greater. Modestly steep mid-level lapse rates (generally 7-8 C/km as
sampled by the 18z AMA observed sounding) and greater effective
shear (25-35 kts) within the vicinity of the surface baroclinic zone
will continue to support a threat for isolated large hail with these
ongoing storms. Recent MRMS and other MESH estimates support this,
with values having ranged from 1-2" with these storms over the past
hour. This potential is expected to persist for another 1-2 hours
before convective intensity gradually wanes amid increasing
inhibition and low-level cold advection.
Farther west, an isolated, high-based thunderstorm has recently
developed on the Sacramento Mountains. Isolated marginally severe
hail and gusty winds may also accompany this cell as it develops
eastward amid a drier, more well-mixed boundary layer.
Given the limited spatial/temporal extent of this severe potential,
watch issuance remains unlikely.
..Chalmers/Thompson.. 05/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...LUB...AMA...MAF...ABQ...
LAT...LON 32940305 32850395 32940489 33260506 33590490 34120414
34630381 35330341 35800289 35880253 35700228 34480214
33650237 33180258 32940305
MOST PROBABLE PEAK WIND GUST...UP TO 60 MPH
MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN
MD 0819 CONCERNING SEVERE THUNDERSTORM WATCH 238... FOR PARTS OF SOUTHEASTERN COLORADO...SOUTHWESTERN KANSAS...AND THE OKLAHOMA/TEXAS PANHANDLES
Mesoscale Discussion 0819
NWS Storm Prediction Center Norman OK
0546 PM CDT Thu May 21 2026
Areas affected...parts of southeastern Colorado...southwestern
Kansas...and the Oklahoma/Texas Panhandles
Concerning...Severe Thunderstorm Watch 238...
Valid 212246Z - 220045Z
The severe weather threat for Severe Thunderstorm Watch 238
continues.
SUMMARY...The evolving thunderstorm cluster may organize further
with increasing potential to produce strong to severe gusts, in
addition to severe hail, through 7-8 PM CDT.
DISCUSSION...Latest Rapid Refresh suggests that upscale convective
growth the past few hours has been aided by focused lift driven by
near-surface convergence within lee surface troughing and
lower/mid-tropospheric warm advection. The evolving cluster now
appears to be processing inflow of moistening boundary-layer air
characterized by CAPE on the order of 1000-2000 J/kg in the peak
late afternoon heating. In the presence of strong deep-layer
westerly shear, further intensification and organization of
convection appears probable through 23-01Z.
Due to the pronounced veering of winds with height, southwesterly
deep-layer ambient mean flow is only on the order of 20 kt, so
eastward propagation may be modest, at least until the evolution of
a strengthening cold pool supports possible acceleration this
evening.
..Kerr.. 05/21/2026
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...DDC...GLD...AMA...PUB...
LAT...LON 38120234 38460169 38110099 37070141 36200213 36120299
36750250 37540226 38120234
MOST PROBABLE PEAK TORNADO INTENSITY...UP TO 90 MPH
MOST PROBABLE PEAK WIND GUST...55-70 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
0256 PM CDT Thu May 21 2026
Valid 212000Z - 221200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ...
...SUMMARY...
Thunderstorms capable of producing large hail and isolated severe
gusts should occur across parts of the central/southern High Plains
this afternoon and evening. A tornado or two may also occur.
...Discussion...
The ongoing forecast remains on track. Moved Slight back farther
west to where ongoing storms are in southeast Colorado and northeast
New Mexico. MRMS MESH currently shows around 1 inch hail with these
cells with some strengthening anticipated as they move into a more
unstable airmass to the east. For additional information, see MCD
812.
A few stronger cells have developed across West Texas where greater
instability has developed. Isolated large hail and severe wind gusts
are possible, but the overall threat is expected to remain
sub-severe. See MCD 813 for additional information about the storms
in this area.
Strong to isolated severe storms have developed across North
Carolina and southern Virginia and are expected to persist through
the afternoon and early evening. See MCD 814 for additional
discussion.
..Bentley.. 05/21/2026
.PREV DISCUSSION... /ISSUED 1115 AM CDT Thu May 21 2026/
...High Plains...
Water vapor imagery shows an upper trough moving across western
WY/CO. This feature will spread weak/broad large scale forcing for
ascent across much of the High Plains from SD to NM this afternoon.
At the surface, southerly low level winds have resulted in an axis
of 40s/50s dewpoints along this corridor. Low clouds are slowly
eroding, which should result in moderate CAPE values and aid in the
development of widely scattered afternoon thunderstorms.
Isolated storms will likely form first over parts of eastern NM.
This activity will build slowly eastward toward west TX with a risk
of large hail.
By mid/late afternoon, storms will likely develop off the Raton and
Palmer ridges, spreading eastward toward western KS this evening.
Shear profiles in this area will be stronger than farther south,
supporting longer-lived storms capable of large hail, damaging
winds, and perhaps a tornado or two.
An isolated cell or two may also produce occasional severe hail over
parts of eastern WY and into the Black Hills region later this
afternoon.
...Carolinas/VA...
Clear skies are leading to strong heating over parts of southern VA
into part of NC/SC. Scattered afternoon thunderstorms are expected
to form in this zone, with steep low-level lapse rates and
sufficient CAPE supporting a risk of gusty/damaging winds in the
strongest cells.
SPC 1930Z Day 3 Outlook
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0227 PM CDT Thu May 21 2026
Valid 231200Z - 241200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL AND SOUTH TEXAS TO THE MIDDLE TEXAS COAST AND IN THE
VICINITY OF THE RATON MESA INTO THE TEXAS AND OKLAHOMA PANHANDLES...
...SUMMARY...
Scattered strong to potentially severe storms appear possible across
portions of central and south Texas toward the middle Texas coast.
Isolated strong to severe storms are also possible from the Raton
Mesa vicinity into the Oklahoma and Texas Panhandles.
...Synopsis...
Broader-scale troughing will be maintained over the north-central
U.S. Saturday into Saturday night, with an embedded short-wave
trough moving through the central Plains. To the immediate east, a
short-wave trough initially over the OH Valley will lift northeast
through the Great Lakes. Meanwhile, a lower-latitude disturbance is
forecast to slowly track through TX. At the surface, an area of low
pressure will gradually undergo occlusion over OH into southwest
Ontario with a trailing front extending southwest through the lower
OH Valley into the southern Plains.
...Central and Southern Texas to the Middle Texas Coast...
There is general agreement in 12z model guidance that thunderstorms
will develop fairly early in the day across the Edwards Plateau,
east of a weak surface low and approaching short-wave trough. The
downstream air mass across central and southern TX is expected to be
moist with dewpoints in the 60s to low 70s, and within the eastern
fringe of a steep mid-level lapse rate plume, yielding moderate to
strong afternoon instability. As such, the early-day thunderstorms
are expected to increase in coverage and intensity through the
afternoon while advancing east/southeast into central and deep south
TX, and eventually toward the TX coast. Some enhancement of
deep-layer shear is forecast across south TX, which will aid in hail
production and cold pool organization, and resultant damaging wind
potential.
...Raton Mesa into the Oklahoma and Texas Panhandles...
Southeasterly, upslope flow will contribute to isolated thunderstorm
development by mid to late afternoon along favored terrain. The
combination of a moderately unstable, steep-lapse-rate environment
and around 30 kt of deep-layer shear will support some potential for
supercell storm modes with an attendant risk for large hail. Storms
will tend to drift southeast into the OK and TX panhandles before
weakening.
...Southeast...
A moist and moderately unstable air mass is expected to develop
Saturday afternoon, with terrain and sea-breeze boundaries serving
as the main foci for diurnally enhanced thunderstorm development.
The models focus the most concentrated thunderstorm activity from
the Savannah River Valley into north FL. There is some model signal
for a weak mid-level disturbance and slightly stronger deep-layer
shear to potentially enhance that thunderstorm regime. Low wind
probabilities may eventually need to be added if confidence
increases in the existence of those features.
...Upper Ohio Valley...
A conditional risk of severe storms exists across the upper OH
Valley Saturday afternoon, east of the surface low and associated
surface front, where vertical shear will be enhanced. The main
uncertainty is the degree of instability within the narrow warm
sector, which varies considerably from model to model. Low
severe-weather probabilities may eventually be included, should
subsequent model trends indicate a more consistent signal for
stronger air mass destabilization.
..Mead.. 05/21/2026
SPC Day 3-8 Fire Weather Outlook
Day 3-8 Fire Weather Outlook
NWS Storm Prediction Center Norman OK
0442 PM CDT Thu May 21 2026
Valid 231200Z - 291200Z
A ridge of high pressure will build across the West this weekend,
gradually sliding towards the central U.S. as guidance depicts a
robust upper trough to enter the Pacific Northwest early next week.
An Atlantic ridge over the Eastern Seaboard is likely to persist
through the forecast period, with multiple rounds of mid-level
perturbations promoting repeat opportunities for precipitation. The
overall pattern suggests dampened fire weather concerns through the
weekend, with the exception of localized breezy conditions across
parts of the West.
Increasing southwesterly flow ahead of the aforementioned incoming
upper trough and a strengthening surface low over eastern OR/western
ID is expected to promote widespread dry and breezy conditions on
Day 5/Monday. 40% Critical probabilities have been introduced to
portions of the Great Basin and Northwest where drying fine fuels
may present fire concerns. As the trough continues dig southward on
Day 6/Tuesday, fire weather highlights may be warranted in future
outlooks as confidence increases in the evolution of the overall
pattern, and the overlap of dry/breezy conditions atop receptive
fuels is recognized.
..Elizalde-Garcia.. 05/21/2026
...Please see www.spc.noaa.gov/fire for graphic product...
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