URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 673
NWS Storm Prediction Center Norman OK
345 PM MDT Sun Sep 20 2026

The NWS Storm Prediction Center has issued a

* Severe Thunderstorm Watch for portions of 
  Eastern Colorado
  Far Western Kansas

* Effective this Sunday afternoon and evening from 345 PM until
  900 PM MDT.

* Primary threats include...
  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...Storms may remain relatively isolated, but a supercell or
two could pose a risk for large hail and severe-caliber wind gusts
through early/mid-evening across the region.

The severe thunderstorm watch area is approximately along and 60
statute miles east and west of a line from 25 miles east northeast
of Burlington CO to 30 miles southeast of Lamar CO. For a complete
depiction of the watch see the associated watch outline update
(WOUS64 KWNS WOU3).

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 550. Mean storm motion vector
30020.

...Guyer

STATUS FOR WATCH 0673 HAS NOT BEEN ISSUED YET

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0244 PM CDT Sun Sep 20 2026

Valid 202000Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
CENTRAL AND EASTERN OKLAHOMA AND FROM EASTERN COLORADO INTO FAR
WESTERN KANSAS...

...SUMMARY...
Thunderstorms with severe wind gusts and large hail remain possible
this afternoon and evening across parts of Oklahoma and from eastern
Colorado into far western Kansas. Isolated severe gusts and hail
will also be possible in parts of the southern Plains and from the
Ozarks eastward into the Ohio Valley.

...20z Update...
The forecast remains generally on track, with only minor adjustments
made to the existing outlook. See the discussion below for
additional information.

..Chalmers/Wendt.. 09/20/2026

.PREV DISCUSSION... /ISSUED 1126 AM CDT Sun Sep 20 2026/

...Central/North TX into central/eastern OK...
Surface analysis places a low over central OK, along a cold front
that arcs from northeast OK into southwest OK and then back up
through the central TX Panhandle. This low also precedes a shortwave
trough moving into western OK. The cold front is forecast to shift
southward/southeastward today as the shortwave continues eastward.
The airmass ahead of this front will be warm, moist, and moderately
buoyant, and thunderstorm development is expected from
central/eastern OK into central TX. Mid-level flow is slightly
stronger across OK, supporting a greater potential for strong to
severe storms. A more isolated severe risk exists across TX where a
more disorganized storm mode is likely. Primary threat is damaging
gusts from 55 to 65 mph.

...Central High Plains... 
An easterly component to low-level flow north of the surface front
will maintain a fetch of moisture (50s deg F surface dewpoints)
across eastern CO this afternoon. This moisture, combined with
heating and cool temperatures aloft, will enable moderate
destabilization by afternoon. Thunderstorm development is expected
as ascent attendant to the mid-level cyclone over WY persists across
the region. Moderate mid-level westerly flow will also persist
throughout the base of this cyclone, resulting in moderate to strong
vertical shear across the region this afternoon and evening. Storm
coverage is expected to remain isolated to widely scattered (largely
due to cooler surface temperatures and some lingering convective
inhibition), but any storms that do form and mature will likely be
supercellular. Primary severe hazard is large hail (1 to 2.5 inches
in diameter), but isolated severe gusts are possible as well. Some
lingering severe risk may eventually develop over southeast CO late
this evening and spread into the OK Panhandle overnight.

...Ozarks into the Mid Mississippi and Ohio Valleys...
Recent surface analysis places lows over central PA, central IL,
central MO, and central OK. An arcing stationary boundary extends
between these features, with this boundary largely demarcated by a
subtle wind shift. Current water vapor satellite imagery shows
several convectively augmented vorticity maxima within this corridor
as well. These vorticity maxima are forecast to progress
eastward/northeastward along the northern periphery of a weakened
mid-level anticyclone centered over the northwest Gulf Coast,
augmenting low-level convergence and helping to support
afternoon/evening thunderstorms from the OH Valley into
central/southern MO.

Despite ample low-level moisture, relatively warm temperatures aloft
will likely mitigate the overall buoyancy. Even so, steep low-level
lapse rates and moderate mid-level flow could still support some
bowing line segments capable of damaging gusts. Highest thunderstorm
coverage this afternoon and evening is expected from
central/southern IN into southern OH, with another corridor of
relatively higher coverage developing across central MO later this
evening as well. Both of these corridors are downstream of a
previously mentioned vorticity max, and represent areas of greater
severe potential.

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0116 PM CDT Sun Sep 20 2026

Valid 221200Z - 231200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM FAR
EAST-CENTRAL MISSISSIPPI INTO THE SOUTHERN APPALACHIANS...

...SUMMARY...
Isolated wind damage may occur with stronger storms from far
east-central Mississippi into portions of the southern Appalachians
on Tuesday.

...Far east-central MS into parts of the southern Appalachians...

A surface cold front will be in place across the TN to Lower MS
Valleys Tuesday morning. Meanwhile, the CAD/wedge front will develop
south across the Carolinas through Tuesday evening. Ahead of the
surface boundaries, upper 60s to low 70s dewpoints will be in place
beneath weak midlevel lapse rates. Abundant low-level moisture and
stronger heating will support a corridor of moderate destabilization
from far east-central MS toward far western NC. Deep-layer westerly
flow will remain weak, and effective shear magnitudes less than 20
kt. However, steepened low-level lapse rates and PW values near
1.75-2 inches could support sporadic strong gusts from wet
microbursts within thunderstorm clusters during the afternoon and
early evening. The CAD/wedge front across the Carolinas will limit
northeast extent of the severe risk, and probabilities have been
removed from that area with the Day 3 update.

..Leitman.. 09/20/2026

Day 2 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0208 PM CDT Sun Sep 20 2026

Valid 211200Z - 221200Z

...NO CRITICAL AREAS...

No changes were made to the Day 2/Monday Outlook with minimal fire
weather concerns across the CONUS; please see the previous
discussion for more information.

..Elizalde-Garcia.. 09/20/2026

.PREV DISCUSSION... /ISSUED 1248 AM CDT Sun Sep 20 2026/

...Synopsis...
Fire weather concerns will remain low across the CONUS on D2/Monday.
A cold front will continue southward into the Southern Plains, with
continued opportunities for wetting rainfall. Temperatures will cool
behind the front across the central/southern Plains with increasing
relative humidity. This in combination with expected rainfall
D1/Sunday through D2/Monday will bring some relief to dry fuels and
keep fire weather potential low across the southern Plains.

...Please see www.spc.noaa.gov/fire for graphic product...

Day 3-8 Fire Weather Outlook  
NWS Storm Prediction Center Norman OK
0433 PM CDT Sun Sep 20 2026

Valid 221200Z - 281200Z

...Discussion...
Weak mid-level impulses embedded within zonal flow will support
precipitation chances across the eastern CONUS through Day
4/Wednesday. Meanwhile, a shallow cold front will slowly progress
southward across southern Texas and the Deep South, promoting
isolated thunderstorm activity. Hot and mostly dry conditions will
continue across the lower Mississippi Valley through next week,
contributing to forecast ERCs approaching the 90-95th percentile
beyond Day 4/Wednesday; but, prevailing light winds should suppress
overall fire weather concerns. 

A weak mid-level trough will traverse the Desert Southwest on Day
3/Tuesday, bringing thunderstorms to Nevada. Some mixed receptive
fuels may reside across portions of eastern Nevada, though forecast
ERCs range from the 50-70th percentile. Ensemble guidance is in
general agreement for ridging to build over the central-western
CONUS late in the workweek as an upper trough evolves across the
Eastern Pacific and impinges upon the Northwest. The overall pattern
indicates stronger southwest winds could return to the northern
Great Basin and Pacific Northwest beginning Day 5/Thursday; however,
an expected marginal fuelscape should limit a broader fire weather
threat. If fuels guidance trends drier, critical probabilities may
be needed in future outlook cycles.

..Elizalde-Garcia.. 09/20/2026

...Please see www.spc.noaa.gov/fire for graphic product...