057
FXUS65 KGJT 111153
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
553 AM MDT Tue Aug 11 2026

.KEY MESSAGES...

- Terrain based showers and thunderstorms will continue Tuesday.
  Gusty outflow winds, lightning and especially dry lightning
  will remain threats.

- Available moisture increases through the week with an uptick
  in convection and precipitation coverage and intensity
  expected Wednesday onwards.

- Wednesday evening through Friday morning will see a
  significant threat for heavy rain and training storms leading
  to areas of flash flooding, and debris flows from fire scars.

- Above normal temperatures will gradually cool closer to normal
  with a cooling trend brought on by monsoonal moisture
  Wednesday and beyond.

&&

.DISCUSSION...
Issued at 1034 PM MDT Mon Aug 10 2026

Satellite imagery shows a classic monsoonal pattern with a Four
Corners high wrapping moisture up out of Arizona into Utah and the
Great Basin before turning east across Utah and into Colorado. This
pattern doesn`t tend to produce heavy rains across eastern Utah and
Western Colorado because the Wasatch Range taps the moisture of the
lower levels leaving the mid to high level moisture to push east,
but this pattern can produce significant lightning with only light
rain. Otherwise the pattern is controlled by high pressure that the
models are positioning across the southeast, but satellite imagery
puts it more over southern Louisiana/southeast Texas which is more
favorable for pushing the moisture off the Gulf up into West Texas,
New Mexico and ultimately southern Colorado. Look for pwats ranging
from 3/4 inch to an inch across the region tomorrow with the heavier
moisture to the west  mostly over eastern Utah. Though we are nor
expecting heavy rain from these showers and thunderstorms, be aware
that the major fire scars can produce significant flash flooding and
debris flows with only a half inch of rain falling in under a half
hour. Always be alert to the weather and your surroundings that may
pose possible hazards. Flash flooding can occur miles from the
thunderstorm.

Tomorrow will see low pressure forming off Southern California that
will develop into a trough along the West Coast by Wednesday. This
will bring a more south-southwesterly flow up through Arizona into
eastern Utah and Western Colorado with a more direct path for deeper
moisture to move up into the region Wednesday night and Thursday
with pwats peaking at an inch or more across much of the region.
This is when we are likely to see areas of heavy rain and training
thunderstorms, especially along the southern to southwestern
exposures of rising terrain. SPC has the entire region under
marginal (>5%) chances for excessive rainfall with slight (>15) along
the Divide extending west across the higher terrain of central and
southern Colorado, and to the south over southeastern Arizona into
west central New Mexico. Would not be surprised if these two areas
of higher probability for excessive rain connect in the next day or
two. This will be the greatest threat for flash flooding from heavy
rains and debris flows from the fire scars. Stay alert to changes
and updates to the forecast over the next few days.

Beyond a few days, forecast confidence fall off as the models, and
even the ensembles are diverging in their solutions. They are in
agreement with the flow aloft becoming more southwesterly Friday
which tends to dry out the region, but the European models push the
high back to to the east keeping the Southwest under a drier
southwesterly flow while the GFS/GEFS models keep the high farther
west over Texas with a more southerly flow across Arizona and New
Mexico to bring a return of the deeper moisture going into early
next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 545 AM MDT Tue Aug 11 2026

Some lingering light shower activity is still ongoing but TAF
site impacts are not occurring with this. Today`s convective
shower and thunderstorm activity will pick up in the afternoon,
bringing potential for gusty outflow winds and brief periods of
MVFR conditions some sites. Gusty and erratic outflow winds
around 25 kts are possible with showers and thunderstorms.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

DISCUSSION...DB
AVIATION...TGJT