371
FXUS65 KGJT 100540
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1140 PM MDT Thu Oct 9 2025

.KEY MESSAGES...

- A surge of tropical moisture is moving into the region,
  bringing peak impacts tomorrow and Saturday. Widespread
  showers and storms are expected with periods of moderate to
  heavy rain rates.

- Excessive rainfall may result in flooding of slot canyons,
  normally dry washes, slickrock areas, recent fire scars,
  urban areas, and other low-lying locations.

- Rockslides and mudslides are possible along the highway
  corridors in the mountains.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 255 PM MDT Thu Oct 9 2025

Showers and thunderstorms are ongoing across the CWA as
moisture moves into the region. This moisture, which is embedded
in southwesterly flow between high pressure over Texas and low
pressure off the coast of the Pacific Northwest, comes from
Tropical Storm Priscilla. So far today we have mostly seen
lighter showers, but there have been a few stronger
thunderstorms producing stronger rainfall rates. Today`s storms
have generally been where CAPE is relatively the greatest,
along the Utah and Colorado border. As moisture continues to
advect into the region tonight, precipitation chances increase,
and remain elevated through at least Saturday night. Today`s
sounding shows that PWATs have increased, as the previous
sounding (00Z) had 0.42 inches, and the 18Z launch earlier
today had 0.74 inches. PWATs in Grand Junction are expected to
continue increasing to over an inch, which is well above
climatology for this time of the year, and near record setting.
By tomorrow morning, PWAT values will exceed 250% of normal
across the CWA, even surging above 300% of normal for some
areas. As a result, PoPs and QPF really begin to pick up after
midnight tonight from southwest to northeast, and will remain
elevated through at least Saturday. In general, Stratiform
precipitation is expected tomorrow, as cloud cover limits
daytime heating and upper level support primarily remains to our
northwest. However, orographic lift, breaks in cloud cover, and
weak bits of energy passing through may support localized
stronger thunderstorms and periods of heavier rain. This raises
concerns for flash flooding, particularly over recent burn scars
and flood prone areas. Rockslides and mudslides are possible in
the higher terrain. As such, a Flood Watch remains in effect
from 6 PM this evening through Saturday at 6 PM.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 255 PM MDT Thu Oct 9 2025

Increased forcing on Saturday, and more breaks in cloud cover, may
allow for some stronger thunderstorms with greater rainfall
rates. Although moisture gradually begins to move out during
the day Saturday, it still remains abundant through Sunday
morning. PWATs are not expected to drop below 200% of normal
until overnight Saturday into Sunday. So, considering the rain
expected through this event, and the increased potential for
heavier rain on Saturday, flash flooding concerns prevail
through at least Saturday evening. Thus, the Flood Watch remains
in effect from 6 PM this evening through 6 PM Saturday.

Drier air pushes in Sunday morning, but the trough passage just
to our north, and the passage of a cold front, should support
some scattered showers and thunderstorms through Sunday
afternoon. This support will mostly be in the northern half of
our CWA, so expect precipitation to favor the higher terrain
north of I-70. The cold front will drop high temperatures on
Sunday, mostly along our northern border, but temperatures will
warm a bit early next week.

After a brief period of drier weather Sunday evening and night,
another push of moisture looks possible Monday afternoon.
Ensembles seem to agree on timing, but not the extent of the
strongest moisture push, which creates some uncertainty on the
details. Regardless, precipitation looks to be in the forecast
Monday onwards.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1125 PM MDT Thu Oct 9 2025

Deep tropical moisture is moving into the region from the
southwest with scattered showers and isolated thunderstorms
spreading to the north. Look for these showers to increase
through the overnight becoming widespread showers across the
region by about 12Z with embedded isolated thunderstorms.
Ceilings will drop to MVFR heights at most TAF sites and IFR
heights at the mountain TAF sites by 18Z, below ILS breakpoints
for KASE, KEGE, KRIL, and most TAF sites. These conditions will
persist well into Saturday.

&&

.HYDROLOGY...
Issued at 216 PM MDT Wed Oct 8 2025

Tropical moisture will stream northward into the region today,
bringing widespread heavy rain and increasing the threat of
flash flooding across portions of southeastern Utah and
southwest Colorado. An increased risk of flash flooding will
continue through at least Saturday evening across the watch
area. Excessive rainfall may result in flooding of slot canyons,
normally dry washes, slickrock areas, recent burn scars, urban
areas, and other low-lying and flood-prone locations. Rockslides
and mudslides are possible in the mountains.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Flood Watch through Saturday afternoon for COZ003-009-017>023.
UT...Flood Watch through Saturday afternoon for UTZ022-025-027>029.

&&

$$

SHORT TERM...GF
LONG TERM...GF
AVIATION...DB
HYDROLOGY...TGJT