869
FXUS65 KGJT 220533
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1133 PM MDT Mon Sep 21 2026

.KEY MESSAGES...

- Wetter weather returns to the region by Tuesday, with showers
  and storms possible each day through the end of the work week.

- There is a potential for moderate and heavy rainfall that
  could lead to flooding mainly in the southern San Juans and
  surrounding valleys Tuesday through Thursday. A Flood Watch is
  in effect for SW San Juans and San Juan River Basin Wednesday
  afternoon through Thursday night.

&&

.DISCUSSION...
Issued at 1100 PM MDT Mon Sep 21 2026

PRECIPITATION CHANCES RETURN:

After a drier and quiet day yesterday and today (Monday),
moisture will make its return as a deeper low pressure trough
works into the Great Basin and high pressure sits over Texas,
allowing southerly flow to bring up sub-tropical moisture once
again. Showers will begin increasing across eastern Utah and the
Four Corners as the trough approaches from the west. Showers and
storms will increase across western Colorado Tuesday afternoon
with scattered storms. A shortwave also moves across northeast
Utah into southwest Wyoming with a robust jet streak and our CWA
in the right entrance region. So storms that do form Tuesday
could be strong given the better shear environment with more
localized heavy rainfall possible.

PWATs increase to 180 to 200 percent of normal across SW
Colorado by Tuesday evening with the deepest moisture Wednesday
and Thursday focused more across SW Colorado. Models seem to
indicate a robust shortwave moving through the area overnight
Wednesday with a low circulation focused across southeast San
Juans and southern valleys, but the SW San Juans and adjacent
southern valleys appear to have the best potential for a few
inches of precipitation and best forcing. The highest QPF for
this round is focusing around the southern San Juans and
southern valleys. In fact, there are indications some spots
could get several inches, which increases the potential for
flooding. Rainfall is possible in the central and northern
mountains, but in general the amounts as lower. In coordination
with PUB and ABQ, went ahead and issued a Flood Watch for
Wednesday afternoon through Thursday night for the SW San Juans
(COZ019) and San Juan River Basin (COZ023) where QPF amounts are
higher, forcing is better and confidence is higher. This area
has also seen plenty of rainfall over the last week with the
most recent stretch of moisture so even with two days of dry
weather, the ground remains saturated.

Uncertainty increases on whether the moisture gets pushed out
of the area or leaves enough to support showers on Friday but
some models are indicating another shortwave trough moving
through on Friday keeping the weather active. Either way it
appears that moisture will not go far so it will not take much
to return.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1128 PM MDT Mon Sep 21 2026

Clouds will continue to increase from the southwest overnight
bringing few to scattered skies becoming more broken
midafternoon onwards. Showers and storms will make an
appearance from 21Z onwards with TAF sites either seeing some
precip on station or in the vicinity. Heading towards the
evening hours, midlevel broken to overcast skies will be the
rule. VFR conditions are still expected though MVFR may be
reached heading towards the end of the TAF period.

&&

.HYDROLOGY...
Issued at 1100 PM MDT Mon Sep 21 2026

After a couple days of dry weather, moisture returns Tuesday
with the deepest moisture expected Wednesday and Thursday,
focused across southwest San Juans and southern valleys. Decided
to issue a Flood Watch Wednesday afternoon through Thursday
night for SW San Juans and San Juan River Basin. This area has
seen plenty of rainfall over the last week and remains
saturated with the forecast indicating several inches of
additional precipitation possible during the Wednesday and
Thursday timeframe. Forcing from a robust shortwave will result
in multiple rounds of showers and storms with potential for
heavy rainfall and flash flooding.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Flood Watch from Wednesday afternoon through Thursday evening
     for COZ019-023.
UT...None.

&&

$$

DISCUSSION...MDA/TGJT
AVIATION...TGJT
HYDROLOGY...MDA