Severe Thunderstorm Warning 21, NWS Grand Junction, CO

999 
WWUS55 KGJT 130219
SVSGJT

Severe Weather Statement
National Weather Service Grand Junction CO
819 PM MDT Sat Sep 12 2026

UTC019-047-130230-
/O.CON.KGJT.SV.W.0021.000000T0000Z-260913T0230Z/
Uintah UT-Grand UT-
819 PM MDT Sat Sep 12 2026

...A SEVERE THUNDERSTORM WARNING REMAINS IN EFFECT UNTIL 830 PM MDT
FOR SOUTHERN UINTAH AND NORTH CENTRAL GRAND COUNTIES...

At 818 PM MDT, a severe thunderstorm was located 24 miles east of
Sunnyside, or 32 miles north of Green River, moving southeast at 20
mph.

HAZARD...60 mph wind gusts and half dollar size hail.

SOURCE...Radar indicated.

IMPACT...Hail damage to vehicles is expected. Expect wind damage to 
         roofs, siding, and trees.

* Locations impacted include...
  Slough Canyon Fire.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

For your protection move to an interior room on the lowest floor of a
building.

Continuous cloud to ground lightning is occurring with this storm.
Move indoors immediately. Lightning is one of nature's leading
killers. Remember, if you can hear thunder, you are close enough to
be struck by lightning.

&&

LAT...LON 3946 11002 3952 10999 3948 10973 3929 10990
      3938 11002 3942 11001 3943 11002
TIME...MOT...LOC 0218Z 294DEG 17KT 3944 10997 

HAIL THREAT...RADAR INDICATED
MAX HAIL SIZE...1.25 IN
WIND THREAT...RADAR INDICATED
MAX WIND GUST...60 MPH

$$

BW

Area Forecast Discussion
National Weather Service Grand Junction CO
525 PM MDT Sat Sep 12 2026

.KEY MESSAGES...

- Warm and windy today, with isolated shower and storm chances.

- Shower and storm chances increase Sunday, and peak in coverage
  by Monday, bringing in widespread cool, wet, and unsettled
  weather.

- Daytime highs this weekend will be 5 to 10 degrees above
  normal, before a shift to cooler temperatures by Monday.

&&

.DISCUSSION...
Issued at 1023 AM MDT Sat Sep 12 2026

ISOLATED TO SCATTERED STORMS THIS WEEKEND:

Modest moisture has begun to settle over the region this morning,
prompting the sparse, weak showers and thunderstorms over Colorado's
Western Slope. You may have also noticed a breezy morning thanks to
decent mixing under the strong zonal flow, paired with a modest
pressure gradient. These breezy conditions will continue to be
around this afternoon as decent mixing continues to be favored. Also
worth mentioning is shower activity will also contribute to windy
conditions should gusty outflow winds develop. Shower and storm
chances this afternoon will be relatively isolated in nature and so
should impacts. By Sunday, storm coverage becomes more scattered as
the next strong push of moisture begins to move in. PWATs begin to
climb Sunday, with values upwards of 200% of normal, with the likely
chance of exceeding the 75th percentile and approaching, if not
surpassing the max values for mid September.

COOLER AND WETTER PATTERN MONDAY AND BEYOND:

By Monday, a deep trough begins to push into the PacNW. Due to
cyclonic flow around a low, southwesterly flow will be favored over
the southwestern CONUS. This means subtropical moisture will be
pushed further inland, centering the strong plume of moisture over
our CWA. PWATs continue to be forecasted over the 75th percentile
for this time of year, which will be enough to prompt our next
chance for widespread showers and storms.

Cloud cover is expected to be generally widespread come Monday,
especially in the mornings. This has the ability to dictate storm
potential each afternoon, which just might be enough to push storm
mode in the stratiform direction. However, it is worth considering
the dynamic forcing at play during this time period as well.
Firstly, Sunday night into Monday will see a cold frontal passage
which will include pockets of frontogenesis. Secondly, by Monday we
are expected to be under the right entrance region of an upper level
jet. This promotes areas of upper level divergence and surface level
convergence. Both of these factors will go towards supporting
discrete storm development (embedded stronger storms in stratiform
rainfall). Whether these storms are isolated or widespread in
nature, localized heavy rainfall is a possibility. Impacts from this
rainfall will be enhanced in places that experienced multiple
rounds of showers and storms the past weekend.

In terms of QPF, the NBM continues to favor the southwestern facing
slopes, particularly along the San Juans, Grand Mesa, and West Elks.
Playing around with probabilities for those southwestern slopes
shows a 60-80% chance of exceeding 0.75" of rain at least for the
Grand Mesa and San Juans. As for the northeastern slopes, lower
rainfall totals are likely, but still indicating some spots to see
0.25" of rain. Although, if rain stratiforms out, these totals will
likely decrease. It is important to note that there is still time
for these factors to evolve before we can speculate on the likeliest
scenario. Stay tuned for future updates, especially once more HiRes
guidance becomes available.

Look for daytime highs to cool down Monday and beyond due to that
aforementioned frontal passage. For the rest of the work week,
active weather will continue to be present. The moisture pool will
continue to lock in over the Western Slope, with the upper level jet
continuing to stretch across the Intermountain West. But, without
clear signs of additional forcing, impacts from this moisture could
be even more conditional on morning cloud cover. At this time, this
is not a factor we can get too in the weeds about. By Friday, models
are in agreement we see a dissipation of moisture, but not a
complete elimination as PWATs still appear to be above normal.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 522 PM MDT Sat Sep 12 2026

Some showers are passing through the region this evening, though
impacts to terminals are expected to be minimal, if anything at
all. As such, VFR conditions persist through tomorrow morning.
Storms redevelop and become more widespread tomorrow beginning
around 17 UTC. The terminals most likely to be impacted are GJT,
RIL, MTJ, TEX, and GUC. Brief drops in visibility to MVFR cannot
be ruled out, though terminals are expected to remain above ILS
breakpoints. Otherwise, gusts of 20-28 kts are expected to
develop tomorrow afternoon for most, if not all terminals.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

DISCUSSION...BS
AVIATION...TGJT

Preliminary Local Storm Report
National Weather Service Grand Junction CO
213 PM MDT Sat Sep 12 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0135 PM     Hail             5 NE Phippsburg         40.27N 106.85W
09/12/2026  E0.25 Inch       Routt              CO   Cocorahs

&&

MDA

Special Weather Statement
National Weather Service Grand Junction CO
233 PM MDT Sat Sep 12 2026

UTZ028-122100-
La Sal and Abajo Mountains UT-
233 PM MDT Sat Sep 12 2026

...A STRONG THUNDERSTORM WILL IMPACT EAST CENTRAL SAN JUAN COUNTY
THROUGH 300 PM MDT...

At 232 PM MDT, Doppler radar was tracking a strong thunderstorm 8
miles northeast of Monticello, moving northeast at 10 mph.

HAZARD...Wind gusts up to 50 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation and
         outdoor objects is possible.

Locations impacted include...
Summit Point.

This includes U.S. Highway 191 in Utah between mile markers 78 and
80.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3785 10916 3796 10937 3817 10927 3809 10905
      3800 10905
TIME...MOT...LOC 2032Z 212DEG 8KT 3797 10924

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...50 MPH

MDA

Special Weather Statement
National Weather Service Grand Junction CO
237 PM MDT Sat Sep 12 2026

UTZ022-028-122115-
La Sal and Abajo Mountains UT-Southeast Utah UT-
237 PM MDT Sat Sep 12 2026

...A STRONG THUNDERSTORM WILL IMPACT EAST CENTRAL SAN JUAN COUNTY
THROUGH 315 PM MDT...

At 237 PM MDT, Doppler radar was tracking a strong thunderstorm over
Monticello, moving southeast at 15 mph.

HAZARD...Wind gusts up to 50 mph and nickel size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation and
         outdoor objects is possible.

Locations impacted include...
Monticello and Eastland.

This includes the following highways...
 U.S. Highway 191 in Utah between mile markers 66 and 77.
 U.S. Highway 491 in Utah between mile markers 0 and 11.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3789 10946 3797 10939 3783 10911 3771 10926
TIME...MOT...LOC 2037Z 305DEG 14KT 3790 10935

MAX HAIL SIZE...0.88 IN
MAX WIND GUST...50 MPH

MDA

Preliminary Local Storm Report
National Weather Service Grand Junction CO
308 PM MDT Sat Sep 12 2026

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0255 PM     Funnel Cloud     2 N Monticello          37.90N 109.34W
09/12/2026                   San Juan           UT   Public

&&

BW