969
FXUS65 KGJT 171802
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1202 PM MDT Thu Sep 17 2026

.KEY MESSAGES...

- Heavy rainfall could result in flash flooding and debris flows
  through late Friday. A few stronger storms may be capable of
  producing hail and damaging wind as well.

- Flood Watches remain in effect for SE Utah and SW Colorado
  through this evening.

- Coverage of showers and storms decreases on Saturday with most
  locations dry on Sunday and Monday.

&&

.DISCUSSION...
Issued at 1116 AM MDT Thu Sep 17 2026

ABUNDANT MOISTURE THROUGH FRIDAY:

Low pressure located to our west continues to keep us under
southwest flow aloft. This flow has ushered in highly anamolous
moisture, which has resulted in a large rain shield that covers
almost the entire area. As the day progresses this rain will move
off to the northeast and or scatter out. As of now the rainfall
rates are steady and not really exceeding 0.50". The big question
today is how much clearing will happen and where. Additional shower
and storm development is expected though out the day, but will any
of these storms be strong and able to produce heavy rainfall. Places
that get sunshine this afternoon have the better chances of more
robust storms. Given all the rain the past several days soils are
getting saturated with not much break. This increases the potential
for flash flooding and debris flows. Models continue to show
that the southern San Juans could get up to an additional inch
of rain by tonight. Showers and storms are expected to linger
into the evening with a gradual decrease in coverage overnight.

The pocket of record setting moisture will move off to our east
tonight, but the plume stays in place due to the low out west.
Tomorrow that low tracks over the northern Great Basin. It is
uncertain how much forcing we will get if any, but the associated
jet is expected to spread overhead. This could provide some forcing
as well as shear. Given the moisture another round of showers and
storms is expected mainly in the afternoon and evening. Like today
places that get more sunshine have the better chances for stronger
storms. With the shear in place a few severe storms are possible
along with that the potential for heavy rainfall. Showers and storms
look to linger Friday night as the low pressure moves closer to the
area.

MOISTURE DECREASES:

On Saturday the low pressure passes to our north, so expect chances
for showers and storms once again. The mositure values are supposed
to decrease, which may only result in a less coverage of convection.
It uncertain if there will still be a chance for heavy rain. On
Sunday the low lifts out over the Plains causing drier air to filter
in from the west. Also, subsidence may put a cap on any convection.
As a result most places will be dry although lingering moisture
across north central CO could support a few showers there. Is it
possible the models are trying to push the moisture out to quickly
so could not rule our isolated showers mainly over the higher
terrain. Monday looks to be quiet as well. Models are indicating
another low pressure trough moving into the Great Basin and
increasing storm coverage once again mid next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1200 PM MDT Thu Sep 17 2026

A shower/thunderstorm convective pattern continues across the area
through the next 24 hours. Most stations are seeing MVFR conditions
as clouds, BR, and rain lower VIS/CIG. The area of steady rain will
continue to move eastward throughout the afternoon with improving
conditions. However, TAF locations may see reduced flight categories
as the potential for heavier showers and thunderstorms develop this
afternoon and evening. KASE,KEGE,KRIL will remain below ILS
breakpoints through at least 06z. A few showers/storms remain
possible overnight. Gusty outflow winds and heavy rainfall are
expected at times. The mountain TAF sites can expect terrain
obscuration through the period.

&&

.HYDROLOGY...
Issued at 1050 PM MDT Wed Sep 16 2026

The moisture in place through tomorrow will support the potential
for heavy rainfall. Soils are now significantly saturated, which
will lead to a lack of absorption and increase the chances for
flash flooding and debris flows through at least Friday. This is
especially of concern for vulnerable areas like steep terrain,
burn scars and slot canyons. Stay aware of road conditions,
avoid locations prone to flash flooding, and report flooding or
other weather impacts to local law enforcement.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Flood Watch through this evening for COZ018-019-021>023.
UT...Flood Watch through this evening for UTZ022-028-029.

&&

$$

DISCUSSION...TGJT
AVIATION...RJ
HYDROLOGY...TGJT