296
FXUS65 KGJT 281750
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1150 AM MDT Mon Sep 28 2026

.KEY MESSAGES...

- Increased moisture will arrive Monday, bringing widespread
  precipitation chances through midweek.

- This rainfall increases flooding concerns across vulnerable
  terrain and burn scars, as well as areas that received
  substantial rain from the last system.

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

&&

.DISCUSSION...
Issued at 942 PM MDT Sun Sep 27 2026

WIDESPREAD PRECIPITATION MONDAY + TUESDAY:

Moisture advection from the tropical storm activity in the Eastern
Pacific will bring anomalous moisture to our region through at least
midweek. PWAT anomalies will be upwards of 250% of normal for a good
chunk of the CWA, especially south of I-70. This means a return to
widespread precipitation chances for much of the region. Shower
activity is expected to start in the Four Corners area in the early
morning hours on Monday, spreading northward by sunrise.
Additionally, this moisture will be accompanied by synoptic forcing,
as a closed upper level low digs southward through California on
Monday, 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 showers and storms. This means
there may be enough forcing from those factors to create embedded
thunderstorms, but even recent HiRes guidance continues to favor the
stratiform rainfall storm mode. The potential for widespread
precipitation sticks around for Tuesday as well before the trough
axis begins tracking eastwards across the Divide by Wednesday.

The potential for prolonged periods of rainfall, including in areas
that have recently received substantial rainfall poses flooding
concerns for the coming days. Hence, a Flood Watch is in effect for
southeast Utah and southwest Colorado from 6AM Monday through 6AM
Wednesday. Please see the hydrology section below for more
information on those flooding concerns. Additionally, if you
plan on recreating outdoors over the next few days, continue to
keep on eye on the forecast and make yourself aware of any
active watches or warnings in your area.

Rainfall amounts carry some uncertainty because models disagree on
the exact track of the closed low and key areas of forcing. Still,
south- and southwest-facing slopes in the San Juans are favored.
Most of the Four Corners area has an 80-90% chance of exceeding 1"
of rain by 6AM Wednesday, while locations like Durango, Pagosa
Springs, and Ignacio have a 60-70% chance of exceeding 2.5" for the
same time period.

Lastly, increased cloud cover will knock temperatures down quite a
bit from Sunday`s highs. Most spots will stay cooler than average
for the first half of the work week.

MOISTURE BEGINS TO EXIT THE REGION WEDNESDAY:

By Wednesday, the elevated moisture and closed low will move east of
the Rocky Mountains, bringing back drier weather for the area.
However, lingering moisture may be enough to support additional
convection over the higher terrain Wednesday afternoon.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1149 AM MDT Mon Sep 28 2026

Showers continue to fill in across the CWA and will be ongoing
through the afternoon/evening hours. Broken to mostly overcast skies
are being reported at many TAF sites, with a continuation of those
conditions into the overnight hours. 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 942 PM MDT Sun Sep 27 2026

Strong southwesterly winds ahead of a closed low centered over
California will pull tropical moisture from Tropical Storm Odalys
and Hurricane Polo towards eastern Utah and western Colorado, with
atmospheric moisture peaking in our area on Monday. The northerly
extent of the expected excessive rainfall poses a threat to our
southern San Juan river basins. Current forecasts suggest 1 to 4
inches of rain Monday morning through early Wednesday. At face
value, rivers and tributaries will see a rise due to the forecast
rainfall. However, localized heavier amounts could result in
flooding across the southern San Juan foothills and communities
further downstream.

Rivers have responded rapidly to recent rainfall due to saturated
soils and increased runoff potential. Thus, prolonged periods of
additional rainfall over these regions would trigger a similar
response. The current precipitation forecast suggests larger peaks
in several creeks and rivers than what has been recently observed.
However, high end probabilistic rainfall amounts (i.e. above 90th
percentile) may lead to rivers exceeding action stage to minor
flooding. Most probable basins to see significant rises include; the
Rio Blanco, San Juan, Piedra, Los Pinos/Vallecito Creek, and the
Animas River Basins.

Convective storms and periods of heavy rainfall fed from said
tropical moisture could result in localized flooding impacts across
the CWA. However, confidence decreases rapidly north of the San
Juans. Confidence has increased enough for a Flood Watch to be
issued for southern portions of the forecast area valid from 6AM
Monday through 6AM Wednesday. Continue to monitor the latest
forecasts especially for those who reside and/or plan to
recreate in the Watch areas.

&&

.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...BS
AVIATION...TGJT
HYDROLOGY...ERW/TGJT