181
FXUS65 KGJT 161553
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
953 AM MDT Wed Sep 16 2026

.KEY MESSAGES...

- Flash flooding will be possible for the coming days as record
  moisture propagates through eastern Utah and western
  Colorado.

- Flood Watches remain in effect for SE Utah and SW Colorado
  today through Thursday.

- Impacts from flash flooding could observed at multiple
  locations across the CWA, with the highest risk likely around
  slot canyons and burn scars.

&&

.DISCUSSION...
Issued at 944 AM MDT Wed Sep 16 2026

WET WEDNESDAY + THURSDAY:

Another surge of sub-tropical moisture is forecast to enter the
region today and stick around for the next 24-48 hours, making for
an even wetter environment than observed over the past few days.
Persistent  flow will continue to dominant over eastern Utah
and western Colorado. Additionally, PWATs are forecast to be
upwards of 300% of normal in some places, particularly focused
on the southwestern corner of Colorado. At this magnitude, PWAT
values are likely to break records.

With this much moisture, cloud cover will certainly be around for
the next few days, keeping the daytime highs on the cooler side.
While on the topic of cloud cover, it is important to note that
cloud cover has the ability to dictate storm mode. Increased morning
cloud cover is indicative of more stratiform rain showers,
whereas less morning cloud cover can lead to an eventful
afternoon with more intense thunderstorms. Both of these
outcomes could be observed over the next 24-48 hours, or even a
mix of both. While we often talk about stratiform rainfall being
less threatening to flash flooding concerns due to weaker
rainfall rates, that is not quite the case through tomorrow. For
one, the lower levels are significantly saturated from previous
days rainfall in most places. This will lead to efficient
rainfall and minimal absorption by soils. We`ve already seen
some vulnerable locations produce flash flooding and debris
flows with weaker rainfall rates, which is an indication that
there is little room left for the land to take on more water. On
the other hand, just because stratiform showers may dominate
does not mean that embedded stronger cells cannot develop. There
are upper level dynamic forcing parameters in place that could
lead to strong updrafts and localized heavy rainfall. With all
that being said, the hail and wind threat will be on the
downturn as hydrologic threats take precedence. Refer to the
hydrology section below for more detailed information about the
threat.

FRIDAY + BEYOND:

By Friday, the moisture pool driving this wet pattern rapidly
diminishes. However, even with this decrease in moisture, we remain
confident that the majority of the region will still see above
normal PWATs through the weekend. With the low pressure beginning to
track eastwards, storm activity should become less pronounced.
Bottom line is that storm chances will be around Friday, but more
scattered in nature. By the end of the weekend, storm activity looks
to be mostly confined to the higher terrain as convection will
mainly be driven by orographics.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 549 AM MDT Wed Sep 16 2026

A convective shower/thunderstorm pattern will be anchored across the
area through the next 24 hours and impacting all TAF sites. Through
the morning hours, a bulk of the storms will lift up across northern
TAF locations as storms move southwest to northeast. Gusty outflow
winds and heavy rainfall rates will generate MVFR cigs/vsby at times
in any storm. Thunderstorms and heavier showers are expected to pick
up again across the entire region after 18Z. Heavy rain and
downburst with 50KT gusts are possible with these storms. The
mountain TAF sites can expect periods of low ceilings and reduced
visibility with these storms along with areas of terrain
obscuration.

&&

.HYDROLOGY...
Issued at 944 AM MDT Wed Sep 16 2026

HiRes guidance continues to suggest stratiform rain bring the
dominant storm mode for the next 24-48 hours. A few embedded
stronger cells should not be ruled out, which have the ability to
produce localized heavy rainfall. Soils have also been allowed to
significantly saturate over the past few days, which will lead to a
lack of absorption in many places. Therefore, with this period
of record moisture (for this time of year), it`s safest to
assume that flash flooding will be a possibility across most to
all portions of the CWA through at least tomorrow. This is, as
usual, especially of concern for vulnerable areas like slot
canyons and burn scars. Additionally, QPF for multiple forecast
cycles continues to highlight the southern slopes of the San
Juans and into the Animas and San Juan River Basins where
48-hour totals are exceeding 2 inches. As a result, southern
portions of the CWA are in a Flood Watch for portions of the
next 24 hours. 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 Thursday evening for COZ018-019-021>023.
UT...Flood Watch through late tonight for UTZ022-028-029.

&&

$$

DISCUSSION...BS
AVIATION...TGJT
HYDROLOGY...BS