031
FXUS65 KGJT 091716
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1116 AM MDT Thu Oct 9 2025

.KEY MESSAGES...

- A surge of tropical moisture arrives today with peak impacts
  tomorrow and Saturday. Widespread showers and storms are
  expected with periods of moderate to heavy rain rates.

- Excessive rainfall may result in flooding of slot canyons,
  normally dry washes, slickrock areas, recent fire scars,
  urban areas, and other low-lying locations.

- Rockslides and mudslides are possible along the highway
  corridors in the mountains.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 440 AM MDT Thu Oct 9 2025

Models remain in good agreement with each other and are tracking
well with satellite imagery on placement of the low off the Pacific
Northwest, the mid-level high over southwest Texas a strong
southwesterly flow across the Desert Southwest drawing tropical
moisture to the northeast across Arizona into the Four Corners area.
Showers and thunderstorms fed by a band of moisture are moving up
from Arizona into southeastern Utah supported by the nose of a
jetstreak pushing up across northern Baja/SoCal into southern Utah.
Look for these storms to continue to push to the north across the
region through the morning as this moist band rides the
southwesterly flow aloft. A dry slot behind  this band will curtail
showers through the late morning, but showers and thunderstorms will
pick up again in the Four Corners area and push into the southern
mountains and the Uncompahgre Plateau through the afternoon with
another band of moisture. Through this evening and overnight, the
main push of tropical moisture out of northern Mexico and possible
some from TS Priscilla moves into eastern Utah and Western Colorado
with widespread showers becoming predominant across the region.
These showers will mostly be orographically driven warm rain processes
that can be very efficient rain makers, especially on the
southwestern faces of rising terrain. For this reason, a Flood Watch
is in place for southeastern Utah and southwestern Colorado from the
New Mexico Border up into the San Juan Mountains and to the
northeast along the Uncompahgre Plateau to the Tavaputs from 6 PM
this evening through Saturday afternoon for heavy rain leading
to possible Flash Flooding in these areas. Note that areas near
recent fire scars and areas prone to flooding are especially
susceptible to flash flooding.

These heavy rain showers will continue Friday morning, but may taper
off through the afternoon as some drier air gets entrained in the
southwesterly flow. This will be short lived as the main push of TS
Priscilla moisture arrives Friday evening, but more on that below.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 440 AM MDT Thu Oct 9 2025

The heavy rain potential continues Friday night through Saturday
night with PWATs along and south of I-70 remaining 300-350% above
normal. The axis of heavy rain will slowly track eastward as a
trough centered along the West Coast moves inland. Not only will the
axis of heavy rain be more centered across the Utah/Colorado border
on Saturday with plentiful upslope flow, but we`ll see an uptick in
synoptic forcing as well. With the atmosphere already saturated form
a couple days of rainfall, it will be hard to get enough CAPE for
stronger storms but this extra forcing will increase the efficiency
of the rainfall rates. These moderate to heavy rainfall rates over
increasingly saturated soils make flash flooding (15-30% chance) the
primary concern through Saturday evening. River rises are also
anticipated, but current river forecasts keep flows below action
stage. A Flood Watch remains in effect until 6 PM Saturday.

Dry air quickly overtakes the region Saturday night into Sunday as
the trough to our west and its attendant cold front move through. An
unseasonably cool and breezy day will follow. Fog may develop in low-
lying areas Sunday morning as cool air moving over moist soils. Be
ready for rapidly changing visibilities on area roadways!

A southwesterly flow pattern quickly returns in the wake of Sunday`s
frontal passage. By Monday afternoon, the moisture-rich airmass that
retreated south into Arizona and New Mexico will return to the
forecast area. PWATs don`t look quite as strong as the incoming
tropical moisture, but will likely exceed 200% of normal, especially
across southwest Colorado. This pulse of moisture looks to peak on
Tuesday, but we`ll likely see periods of scattered to widespread
showers and storms for the first half of the new week.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1111 AM MDT Thu Oct 9 2025

Isolated to scattered showers and storms this today will become
more widespread tonight through the taf period. Most if not all
taf sites will see impacts from this event especially late in
the period at KTEX, KDRO and KMTJ. Wind gusts up to 30 mph are
possible during the period.

&&

.HYDROLOGY...
Issued at 216 PM MDT Wed Oct 8 2025

Tropical moisture will stream northward into the region today,
bringing widespread heavy rain and increasing the threat of
flash flooding across portions of southeastern Utah and
southwest Colorado. An increased risk of flash flooding will
continue through at least Saturday evening across the watch
area. Excessive rainfall may result in flooding of slot canyons,
normally dry washes, slickrock areas, recent burn scars, urban
areas, and other low-lying and flood-prone locations. Rockslides
and mudslides are possible in the mountains.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Flood Watch from 6 PM MDT this evening through Saturday
     afternoon for COZ017>023.
UT...Flood Watch from 6 PM MDT this evening through Saturday
     afternoon for UTZ022-025-027>029.

&&

$$

SHORT TERM...DB
LONG TERM...KAA
AVIATION...TGJT
HYDROLOGY...TGJT