124
FXUS65 KGJT 111137
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
537 AM MDT Sat Oct 11 2025

.KEY MESSAGES...

- Moisture from Tropical Storm Priscilla will continue to move
  through the area today with precipitation coming to an end
  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 to flash flooding.

- 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 today and tonight. Heavy
  rain and damaging winds are the primary threats with large
  hail as the secondary threat.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 344 AM MDT Sat Oct 11 2025

Satellite imagery continues to show the deep plume of moisture
extending from northern Baja up through Arizona into Utah and
Western Colorado. Look for more warm rain processes producing areas
of heavy rain this morning favoring the southwest faces of rising
terrain, especially in the Four Corners up into the San Juan
Mountains. Breaks in the clouds along the southeastern edge of the
plume look to track to the south of the region today keeping the
Four Corners area mostly cloud covered and thereby limiting diurnal
heating, but upper-level dynamics of the right entrance region of a
jetstreak moves over the region by noon and with the upper-level
trough approaching from the northwest with drier, cooler air aloft,
CAPE of 300-600 J/kg are forecast across eastern Utah into Western
Colorado. This along with the pressure gradient aloft tightening,
increasing sheer to 45-55 kts, expect more widespread thunderstorms
today with some stronger storms producing large hail, winds over 60
mph and periods of heavy rain. Storm total rain fall today look to
be around an inch along and south of I-70 with another two to three
inches possible in the San Juans. Flooding and flash flooding remain
a risk today and tonight.

A cold front moves across the northern half of the region tonight
after midnight. Expect winds gusting 40-50 mph and a band of strong
thunderstorm ahead of this front. These storms will be capable of
producing large hail, gusts over 60 mph and heavy rain leading to
areas of flash flooding. The Flood Watch remains in effect across
eastern Utah and most of Western Colorado today and overnight
tonight.

As the trough passes to the north late today and tonight, a zonal
flow aloft sweeps the moisture to the east out of the region with
Sunday being much drier than the past couple days. Though models
have downplayed convective activity Sunday afternoon, we can`t rule
out a few lingering showers and thunderstorms favoring the higher
terrain through the afternoon. Temperatures today will run near
normal to a few degrees below normal across the region. Tomorrow
areas north of I-70 will see temperature 10 degrees cooler behind
the cold front.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 344 AM MDT Sat Oct 11 2025

Drier air will continue to move into the region Sunday night after
the cold frontal passage that happened earlier in the day. However,
it won`t last long because now we`ll have to contend with the
moisture from TD Raymond. This increased moisture will start
advecting from the south early Monday morning and by daybreak will
have overspread much of the CWA. Values will continue to increase
through the day with anomalous PWATs reaching around 200 to 250% of
normal for, roughly, the southern half of the CWA and around 150%
elsewhere. While these values aren`t as high as what we`re seeing
with Priscilla, they`re still high enough to allow another round of
rain to move into the area. Favored areas include the southern
valleys into the San Juans where current forecast QPF amounts are
around an inch. Would not be surprised if these numbers change as
support aloft will be in the form of a strong jet streak that should
provide ample lift to bump those precip numbers up. Time will tell.
There will be plenty of cloud cover accompanying this increase in
moisture so while some embedded convection will be possible, a more
soaking, stratiform precip looks to be the end result. Ensembles are
indicating this precip continuing through Tuesday afternoon before
coming to an end...sort of. Once the push of moisture from Raymond
ends, a closed low will approach the CWA from the west before
turning northeast into Wyoming. Shortwave energy will move through
the mean flow as this occurs bringing more chances for showers and
thunderstorms Wednesday and Thursday. Suffice to say, prolonged
unsettled weather will continue through the next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 530 AM MDT Sat Oct 11 2025

Low clouds, rain, and some fog are all in play this morning as
widespread precipitation has overspread much of eastern Utah and
western Colorado. Rain is expected to continue for much of the
day with some thunderstorms possible this afternoon and evening
which are covered by PROB30 groups for just about all TAF sites.
Flight conditions will vary from VFR to MVFR. Under and near
any of the heavier showers/storms IFR to LIFR can be expected
due to low ceilings and visibilities. ILS breakpoints will also
likely be met thanks to those same low ceilings. Mountain
obscurations will occur across the region.

&&

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

&&

$$

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