295
FXUS65 KGJT 282355
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
555 PM MDT Mon Sep 28 2026

.KEY MESSAGES...

- Scattered to widespread precipitation showers and storms are
  expected through midweek.

- This rainfall increases flooding concerns, especially within
  and adjacent to the southern San Juans.

- A Flood Watch is in effect for southeast Utah and southwest
  Colorado through 6AM Wednesday.

&&

.DISCUSSION...
Issued at 1256 PM MDT Mon Sep 28 2026

WIDESPREAD PRECIPITATION THROUGH TUESDAY:

Moisture advection from tropical storm activity in the Eastern
Pacific will bring anomalous moisture to our region through at
least midweek. PWAT anomalies will be upwards of 200-250% of
normal for a good chunk of the forecast area, especially south
of I-70. This means widespread precipitation chances for much of
the region.

A closed upper-level low digs southward through California on
today, and then across the Desert Southwest on Tuesday and
Wednesday. A jet streak aloft and energy from a trough axis will
work in tandem to create lift for continuous showers and storms
for the rest of the day. As the low continues to track just
south of the AZ/NM/UT/CO state lines on Tuesday, drier periods
are possible with the best forcing skirting south of the
forecast area. However, The potential for moderate to heavy
precipitation will continue to pose a threat for the Southern
San Juans and adjacent valleys.

The potential for prolonged periods of rainfall, including in
areas that have recently received substantial rainfall, poses
flooding concerns through Wednesday. As a result, a Flood Watch
is in effect for southeast Utah and southwest Colorado through
6AM Wednesday. Please see the Hydrology Section below for more
information on those flooding concerns.

MOISTURE BEGINS TO EXIT THE REGION WEDNESDAY:

By Wednesday evening, the elevated moisture and closed low will
move east of the Rocky Mountains, leading to drier weather for
much of the forecast area.

High pressure looks to drive the remainder of the seven-day
forecast. As such, predominately dry conditions with
temperatures running around 5 degrees above normal for early
October can be expected late week through next weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 542 PM MDT Mon Sep 28 2026

Showers and a few embedded thunderstorms are ongoing with broken
to overcast skies being reported at most TAF sites. These
conditions are expected to persist tonight before a break near
sunrise. Showers are expected to redevelop over southern
Colorado tomorrow morning. Winds will be generally light and
terrain driven under these showers. Where heavier rainfall is
present, expect flight conditions to vary between low end VFR
and MVFR, due to low cigs and visibility constraints. ILS
breakpoints will likely be met for some terminals and mountain
obstructions will be common.

&&

.HYDROLOGY...
Issued at 153 PM MDT Mon Sep 28 2026

The bulk of tropical moisture will be streaming across eastern
Utah and western Colorado today. Integrated water vapor
transport (IVT) maximizes this evening across the San Juans, so
anticipate precipitation amounts to wane as our moisture fetch
declines, too. River responses will be highly dependent on
precipitation totals, and peak flows will lag behind periods of
moderate rainfall. Forecast guidance shows peak arrival times
between midnight tonight to Tuesday morning, depending on river
segments and proximity to the watershed`s headwaters.

The Navajo River, Rio Blanco and San Juan River are forecast to
inch towards bankfull conditions and near action stage by early
Tuesday morning, with 2 to 2.5" of precipitation expected in
their upper basins. However, if locally higher amounts are
observed (i.e. exceeding the 90th percentile forecasts of 4.5 to
5.5 inches) then minor flooding is possible. Elsewhere, rivers
and creeks will also see a notable rise, but probabilities of
exceeding flood stage are lower. Nonetheless, a significant rise
in several streams, rivers and creeks is expected in response
to today`s tropical surge, and minor flood poses a threat,
namely across our southern counties.

The northern extent of moisture maintains some ambiguity as the
systems merge over the next 48 hours. However, after a brief
lull on Tuesday, wrap around moisture on the northern periphery
of the low could support another wave of precipitation across
the southern half of the CWA on Wednesday. As a result, river
forecasts reveal a secondary peak Wednesday evening, albeit,
less than its predecessor.

A Flood Watch remains in effect across southeast Utah and
southwest Colorado, where the higher precipitation totals are
favored. However, keep an eye on evolving conditions and
conditions upstream. Flooding continues to be a concern,
especially with rivers rising overnight.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Flood Watch through late Tuesday night for COZ017>023.
UT...Flood Watch through late Tuesday night for UTZ022-028-029.

&&

$$

DISCUSSION...TGJT
AVIATION...TGJT
HYDROLOGY...ERW