335
FXUS65 KGJT 102346
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
546 PM MDT Fri Oct 10 2025

.KEY MESSAGES...

- Moisture from Tropical Storm Priscilla will continue to move
  into the area through Saturday with precipitation coming to
  an end on Sunday.

- In general, total rainfall amounts are 1-2 inches with
  locally higher amounts of up to 3-4 inches possible.

- Excessive runoff from rainfall rates in excess of an inch per
  hour may result in flooding of slot canyons, normally dry
  washes, slickrock areas and urban areas. Recent burn scars
  will be especially vulnerable.

- Smaller waterways may respond quickly to heavy rainfall leading
  to localized flash flooding. However, major rivers are not
  expected to exceed flood stages at this time.

- Isolated severe storms are possible on Saturday. Heavy rain
  and damaging winds are the primary threats with large hail as
  the secondary threat.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 151 PM MDT Fri Oct 10 2025

There is no doubt that the tropical moisture has reached the
forecast area today with the 18z sounding showing 1.15" of
PWAT, which is a record for the day and the month of October.
Rainfall amounts of 0.5- 1.5" have already occurred for some
locations with the highest amounts in the southern San Juans and
foothills. This stream of moisture and expansive rainfall
extends all the way to the northern Baja. Models show that this
moisture plume will not budge and continue to send additional
rounds of rain into our area through tomorrow morning. Most of
this will be stratiform, although a few lightning strikes are
possible especially if the clouds can break up. Pockets of
moderate rainfall can not be ruled out as well. Tomorrow the
models show an expansive area of stratiform in the morning
moving eastward around mid day.

As the trough approaches from the northwest it appears that
lapse rates may try to steepen. Also, there are hints that the
clouds could break up and allow for some CAPE. If this happens
instability could build over the western half of the forecast
area for the afternoon. The CAMs have been trending to more
convection in the afternoon. Given the anomalous moisture in
place rainfall rates over 1" per hour are more possible with
the stronger cells. By this time many locations might have
saturated soils therefore any additional rainfall could lead to
flooding and flash flooding, which is why the flood watch was
expanded to most of the CWA. Prolonged rainfall may cause small
waterways to rise so any heavy rain could lead to flash
flooding. Major rivers are not expected to exceed flood stages,
but rapid rises of 2-6 feet are possible. The other potential
threat as shear increases tomorrow due to the main jet is that a
few storms may become severe and capable of producing large
hail and damaging winds. Tomorrow night the main trough and
associated cold front are expected to swing through the area.
Additional storm development is possible along the front since
there may be lingering instability, which could pose a risk for
nighttime flooding. Total rainfall amounts for this event have
increased in and around the San Juans, where 2-4 inches look
more probable. Otherwise the amounts for other locations have
not changed much. Given the possibility for heavy rainfall
ahead and along the front tomorrow night the flood watch has
been extended until 12z Sunday.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 151 PM MDT Fri Oct 10 2025

Remnants of anomalous moisture from TC Priscilla are expected to
begin departing the region on Sunday as the upper-level trough axis
moves through. Colder post-frontal temperatures and drier air
intruding into the area will bring a quick halt to the widespread
precipitation. Should some residual moisture remain, some weaker and
isolated rain and snow showers could develop Sunday afternoon, but
there`s little to suggest that impacts will be of too big a concern.
Relief will be short-lived though as a second wave digs southwards
along the west coast on Monday. As flow returns to southwesterly,
remnants of TC Raymond located near the Desert Southwest will be
pulled northwards over us. PWAT anomalies will be less impressive
this time around, but considering the record-breaking moisture TC
Priscilla gave us, this isn`t saying much. These anomalies could
still push 250% in southern portions of the CWA, so look for
rainfall to be prevalent once again. Deterministic models are
trending in a similar direction as they did leading up to this
weekend`s storm with variability in models regarding instability,
though leaning towards a more stable environment. Dynamics may
become more favorable in the middle of the week as we begin to fall
under the right entrance region of the upper-level jet streak and
height falls become more rapid as the trough treks through the
Intermountain West. Either way, the early messaging for this system
will mimic the lead-up to TC Priscilla`s impacts on the CWA.
Widespread rainfall remains on the horizon, trending towards a more
stratiform event with a potential for stronger storms in the mid-
week depending on available lift and instability. Flooding concerns
may return with TC Raymond`s moisture, though with this pool of
moisture not being quite as extreme, we will need to wait for higher
resolution guidance and better model agreement before confidence in
the details will increase. Stay up-to-date with the latest forecasts
and guidance as more data becomes available.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 532 PM MDT Fri Oct 10 2025

Moderate to heavy rain showers continue along roughly the I-70
corridor, with lighter showers across much of the rest of the
area. These showers will persist through the next 24 hours, with
a possibility of thunderstorms tomorrow afternoon for lower
elevation terminals. VFR to MVFR conditions will prevail through
the period, with periods of IFR to LIFR possible, especially
under heavier rain bands. Winds will be light and variable.
Mountain obscuration will be common.

&&

.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 tomorrow night 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 late Saturday night for COZ001>003-006>014-
     017>023.
UT...Flood Watch through late Saturday night for UTZ022>025-027>029.

&&

$$

SHORT TERM...KJS
LONG TERM...BW
AVIATION...TGJT
HYDROLOGY...TGJT