Debris Flow in Colorado, August 23, 2025

Area Forecast Discussion
National Weather Service Grand Junction CO
341 PM MDT Sat Aug 23 2025

.KEY MESSAGES...

- Scattered showers and thunderstorms are expected throughout
  this afternoon, mostly along the high terrain Gusty winds,
  frequent lightning, and moderate to heavy rain are all
  possible.

- Moisture continues to increase over the next several days,
  with widespread shower and storm activity expected. Potential
  for heavy rain and debris flows over burn scars will be
  heightened from Sunday into early next week.

- Temperatures are trending downwards, with near-normal highs
  expected tomorrow and well below normal highs throughout the
  work week.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 341 PM MDT Sat Aug 23 2025

Moisture continues its upward trend as a plume of anomalously
high PWAT's continues to rotate around the Desert Southwest high
into the Intermountain West. As of the 18Z Grand Junction
sounding, PWAT's have risen to just short of an inch.
Thunderstorms have gotten going already along the San Juans and
the Uncompahgre Plateau, but with some relatively deep CIN still
hampering convection, most storms to this point have been mild
and short-lived. This CIN should continue to erode over the
afternoon, though we should still see most storm development
remain along the high terrain. Should we be able to break that
cap, particularly over southwestern Colorado where mesoanalysis
suggests CAPE is exceeding 1000 J/kg, it's possible that we
could have a few small hail-producing storms alongside the
strong 40+ mph outflows we've already seen occur today. Flash
flooding will continue to be a concern going forward as well,
particularly over burn scars and known flashy areas. Stay
weather- aware, especially if you plan on being outdoors.

The aforementioned plume of moisture spills back into the CWA
tomorrow as the Desert Southwest high migrates southeastwards
and flow turns more westerly. Ensembles are hinting at PWAT's
surpassing an inch across most portions along the CO-UT border
during the afternoon, roughly 170-190% of normal. This should
transition us into a pattern of more widespread storm coverage,
not just on Sunday, but throughout much of the week. With the
push of moisture just getting going, morning cloud cover looks
to be scattered across much of the region. Models are keying in
on this being enough to bump the CAPE up quite a bit,
particularly in west-central Colorado along the I-70 and US-50
corridors. The more conservative models are still exceeding 500
J/kg, with more eager models reaching 1000 to 1500 J/kg.
According to deterministic models, this pairs with the
expectation for a weak shortwave to cross through the CWA in the
afternoon. This results in a fairly favorable setup for more of
a convective storm mode south of I-70, evident in CAM's.
Morning cloud cover may be a little more stubborn north of I-70
though, and CAM's are leaning towards more stratiform-type
showers tomorrow afternoon. As far as timing goes, some weaker
showers may form early in the morning, with stronger storms
developing around noon and persisting into the evening, possibly
well beyond sunset. Look for high temperatures to really begin
turning downwards at this point as well, with most of the region
returning to near-normal highs tomorrow.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 341 PM MDT Sat Aug 23 2025

High pressure remains in place for much of the week ahead, as
does monsoonal moisture. This weather pattern supports a cooler,
wetter week with daily precipitation chances and below normal
temperatures.

On Monday, the global ensembles support PWATs 150-185% of
normal area wide. Areas that see a little clearing in the
morning could see stronger convection develop in the afternoon,
but with the amount of moisture present it is more likely that
broken to overcast clouds will limit the amount of daytime
heating. This favors a transition to stratiform rains across
much of the region with some embedded storms here and there. If
this scenario does play out, the potential for burn scar flash
flooding will be low (10-30% chance).

Moisture advection strengthens Tuesday evening into Wednesday
which will keep stratiform precipitation chances elevated
through the overnight hours. Once again, we may see a decrease
in afternoon thunderstorm coverage in favor of a more stratiform
rain across much of eastern Utah and western Colorado.

Moisture begins to retreat to the north late Wednesday into
Thursday. Depending on the timing of this moisture retreat, we
could see a transition back to convective precipitation south of
I-70 on Thursday. If so, periods of moderate to heavy rainfall
and lightning chances will reenter the forecast.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1138 AM MDT Sat Aug 23 2025

The southern half of western Colorado and most of eastern Utah
will see rounds of showers and thunderstorms this afternoon
with gusty and erratic winds, frequent lightning, and brief
heavy rain all possible. VFR conditions will prevail for most
terminals, but drops to MVFR conditions due to heavy rain are
possible, especially for KTEX and KDRO where shower and storm
activity is most likely to occur.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

SHORT TERM...BW
LONG TERM...KAA
AVIATION...TGJT

Hazardous Weather Outlook
National Weather Service Grand Junction CO
311 AM MDT Sat Aug 23 2025

COZ001>014-017>023-UTZ022>025-027>029-240915-
Lower Yampa River Basin-Central Yampa River Basin-
Roan and Tavaputs Plateaus-Elkhead and Park Mountains-
Upper Yampa River Basin-Grand Valley-Debeque to Silt Corridor-
Central Colorado River Basin-Grand and Battlement Mesas-
Gore and Elk Mountains/Central Mountain Valleys-
Central Gunnison and Uncompahgre River Basin-
West Elk and Sawatch Mountains-Flat Tops-Upper Gunnison River Valley-
Uncompahgre Plateau and Dallas Divide-Northwest San Juan Mountains-
Southwest San Juan Mountains-Paradox Valley/Lower Dolores River-
Four Corners/Upper Dolores River-Animas River Basin-
San Juan River Basin-Southeast Utah-Eastern Uinta Mountains-
Eastern Uinta Basin-Tavaputs Plateau-Arches/Grand Flat-
La Sal and Abajo Mountains-Canyonlands/Natural Bridges-
311 AM MDT Sat Aug 23 2025

This Hazardous Weather Outlook is for northwest Colorado, southwest
Colorado, west central Colorado, east central Utah, northeast Utah
and southeast Utah.

.DAY ONE...Today and tonight.

Scattered to widespread storms are possible this afternoon,
with areas along and south of I-70 most favored. Storms will be
capable of producing gusty outflow winds up to 40 mph and frequent
lightning. Moderate to heavy rainfall will be possible.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

Chances of widespread heavy rain, along with potential flash
flooding or debris flows, will be on the increase daily as moisture
increases through early next week. Temperatures will run near to
below normal.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected today or tonight, however
spotters are encouraged to relay rainfall amounts or any observed
flooding to the National Weather Service in Grand Junction.

Preliminary Local Storm Report
National Weather Service Grand Junction CO
1205 PM MDT Sat Aug 23 2025

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

1053 AM     Rain             5 SW Cortez             37.30N 108.63W
08/23/2025  M0.92 Inch       Montezuma          CO   ASOS

            ASOS station KCEZ Cortez Municipal Airport
            0.58 between 4:30 and 5:00 PM Fridy, 22 Aug.

&&

db

Preliminary Local Storm Report
National Weather Service Grand Junction CO
1206 PM MDT Sat Aug 23 2025

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

1045 AM     Rain             2 SSE Mayday            37.32N 108.06W
08/23/2025  M0.54 Inch       La Plata           CO   Mesonet

            Mesonet station LCDC2 1.9 S Mayday.

1104 AM     Rain             4 NW Redmesa            37.14N 108.22W
08/23/2025  M0.53 Inch       La Plata           CO   Mesonet

            Mesonet station EW3867 Marvel.

&&