638
FXUS65 KGJT 100932
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
332 AM MDT Fri Oct 10 2025

.KEY MESSAGES...

- Moisture from TS Priscilla will continue to move into the area
  today and tomorrow. Widespread showers and thunderstorms will
  continue through Sunday with moderate to occasionally heavy
  rain expected.

- Flash Flood Watches remain in effect for central and southeast
  Utah, southwest Colorado and portions of central Colorado.

- 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
  will be possible along highway corridors in the mountains.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 156 AM MDT Fri Oct 10 2025

Moisture from TS Priscilla continues to advect into the region
and will continue to do so over the coming days. PWATs yesterday
evening reached 0.82 inches at the Grand Junction airport which
is just shy of the maximum value recorded on that date of 0.87
inches. There is little doubt that the record will be broken
over the next few days as PWAT anomalies will reach upwards of
250 to 350% of normal...by Saturday morning a few spots may
reach 400% of normal. Synoptically speaking, we remain
sandwiched between a closed low off the PacNW coast and high
pressure centered over west Texas which is allowing south
through southwesterly flow to tap into that moisture as
mentioned above. Currently a shortwave is moving across the area
bringing some light to moderate rain to central and SE Utah and
far western and southwestern CO. As the wave continues to move
northward, so too will the rain. Unsettled weather will be the
name of the game for the rest of the day as pieces of energy
move across the region. As previously mentioned, stratiform
precip is expected for much of today thanks to cloud cover
inhibiting daytime heating while the strongest upper level
support stays to our west. Having said that, a few breaks in the
clouds may allow instability to be released allowing some
thunderstorms to form this afternoon. If this occurs, some very
heavy rain may be realized...for obvious reasons the Flash Flood
Watch will remain in effect.

Tonight, another shortwave will move across the CWA bringing
another round of soaking rain, similar to what we`re seeing
currently as the biggest push of moisture really kicks in. This
occurs as upper level dynamics move overhead and a shortwave
moves through the mean flow. The end result will be heavy rain
for the Four Corners region heading into the San Juans and a
secondary push also possible in the Uintah Basin up into the
eastern Uintas themselves. Flash flooding remains a definite
concern so keep abreast of the latest conditions before
considering any hiking, especially near recent burn scars or in
slot canyon country. Drier air is still progged to move in
during the late afternoon hours but `drier` is relative because
PWATs will still remain around 150 to 200% of normal. Despite
this drier air, precip will continue as an upper level trough
becomes the focus for rainfall as described below.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 156 AM MDT Fri Oct 10 2025

High pressure over Texas and troughing along the West Coast will
dominate the weather pattern through the extended forecast period
keeping eastern Utah and Western Colorado in southwesterly flow
aloft tapping subtropical moisture in northern Mexico and off the
Eastern Pacific. Shortwave systems moving through the trough
will allow drier air to get entrained into the flow with more
westerlies aloft as the shortwaves pass to the east and pick up
more moisture with more southerlies aloft as the shortwaves drop
into the trough periodically.

The first shortwave system is the low currently off the Pacific
Northwest opening into an openwave as it moves inland, passing to
the north Saturday evening into Sunday morning dragging a cold-
frontal boundary with it. This cold front moves in over the Uintas
after midnight Saturday and will have exited to the east onto the
Front Range by noon Sunday. The cold front looks to only slide south
to about the I-70 corridor under the zonal flow, but we could see
some stronger thunderstorms over the higher terrain north of I-70
overnight Saturday as this front moves through. With the more zonal
flow aloft, dry-air intrusion will drop dewpoints 20 degrees across
the region by Sunday evening. Residual moisture in the valleys may
be enough to spawn a few isolated afternoon showers and
thunderstorms in the mountains Sunday, but the models haven`t picked
up on this yet.

As the next shortwave drops into the trough Monday, the flow aloft
turns back to the south drawing another surge of moisture north.
Expect widespread showers across and south of the San Juans Monday
through Tuesday morning  with more scattered to isolated showers
spreading north to the Tavaputs, the Roan and the Flat Tops. This
surge of moisture doesn`t seem to be as deep as this weekend`s
surge, but its too soon to say if flooding will be a concern with
this system. Stay tuned. Yet another shortwave system drops into the
trough late Tuesday prompting another surge of moisture mid to late
in the week keeping the forecast on the wet side with more showers
and possible thunderstorms. Come back for updates on these systems
next week to get the latest forecast. &&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1125 PM MDT Thu Oct 9 2025

Deep tropical moisture is moving into the region from the
southwest with scattered showers and isolated thunderstorms
spreading to the north. Look for these showers to increase
through the overnight becoming widespread showers across the
region by about 12Z with embedded isolated thunderstorms.
Ceilings will drop to MVFR heights at most TAF sites and IFR
heights at the mountain TAF sites by 18Z, below ILS breakpoints
for KASE, KEGE, KRIL, and most TAF sites. These conditions will
persist well into Saturday.

&&

.HYDROLOGY...
Issued at 156 AM MDT Fri Oct 10 2025

Tropical moisture will continue to 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 tomorrow 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 will also be possible in the mountains.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Flood Watch through Saturday afternoon for COZ003-009-017>023.
UT...Flood Watch through Saturday afternoon for UTZ022-025-027>029.

&&

$$

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