558
FXUS65 KGJT 140642
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1242 AM MDT Tue Oct 14 2025

.KEY MESSAGES...

- A Flood Watch remains in effect for the southern San Juans
  and adjacent valleys. Total rainfall amounts of 1-2 inches are
  expected with locally higher amounts up to 3-4 inches.

- Unsettled weather continues for much of the week as another
  system moves in from the west bringing more showers and storms
  to eastern Utah and western Colorado.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 421 PM MDT Mon Oct 13 2025

Tropical moisture has returned and will continue to provide
heavy rain to the southern San Juans and adjacent valleys
through tomorrow morning. After a round of stratiform rain this
morning, clearing across southwest CO and southeast UT led to
stronger convection than we`ve seen in previous days. Stronger
storms have been capable of producing hail up to 1 inch in
diameter and torrential rainfall. Thankfully plentiful shear has
kept these storms moving, reducing the threat for flash
flooding unless storms train over the same area.

After sunset we are anticipating another swath of stratiform
rain to move into southwest Colorado from the south. Additional
rainfall around 0.5-1 inches will be commonplace in the Flood
Watch area with locally higher amounts of 1-2 inches, mainly
over the San Juans. This efficient rainfall is thanks to PWATs
upwards of 250-300% of normal for mid October. Please see the
Hydrology section for more on the potential flooding impacts.

Rainfall will taper off tomorrow morning as "drier" air begins
to work in from the west- although PWATs remain elevated at
150-175% of normal. As the jet stream responsible for our
tropical airmass moves off to the east, some of the moisture
gets trapped by the terrain in the Archuleta/La Plata County
area where PWATs will remain around 200% of normal despite the
decrease elsewhere. It`s not entirely clear how this will impact
the potential for additional heavy rain after the Flood Watch
expires at noon tomorrow, but the CAMs support scattered
convection in that area through the afternoon hours, tapering
off Tuesday night. Elsewhere, drier conditions are expected
tomorrow afternoon with isolated showers and storms favoring
northeast Utah and northwest Colorado.

&&

.LONG TERM /TUESDAY NIGHT THROUGH MONDAY/...
Issued at 421 PM MDT Mon Oct 13 2025

After a brief lull in precipitation Tuesday night (with the
exception of some higher terrain areas), moisture makes another
push on Wednesday. This moisture, which does not look to be as
abundant as what we have seen the last couple of days, should be
sufficient enough to support another round of widespread
precipitation. However, with PWATs only elevated to 150-200% of
normal, PoPs and QPF are limited throughout the day. But, upper
level support may help to produce periods of heavier rain from
what moisture is available. A broad region of PVA will pass
through the CWA Wednesday into Thursday as the low pressure
system to our west approaches. Jet support may also be present,
but the most favorable region for this support will likely be to
our north on Wednesday, where diffluence and the left exit
region of a jet streak is positioned. The southwestern portion
of our CWA will be close to the right entrance region of the
same jet streak, which could provide additional support for
heavier rain in this area of our CWA. But, very slight cyclonic
curvature to the jet streak could reduce this effect from the
right entrance region.

Given the recent rainfall and flooding near the southern San
Juans, this remains an area of concern on Wednesday. Favorable
orographics from southwesterly flow should allow for
precipitation regardless of any enhancement from upper level
support, so additional support from the synoptic setup would
elevate concerns.

A cold front looks to move through the CWA Wednesday night,
which may help to produce some precipitation, primarily north of
I-70. The cold front will drop high temperatures by around 10
degrees on Thursday to well below normal for this time of the
year. Moisture moves out on Thursday, leading to drier
conditions and a decrease in cloud cover. With colder air in
place, and reduced cloud cover, overnights lows will drop as
well beginning Thursday night.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1150 PM MDT Mon Oct 13 2025

Scattered to wide spread showers with embedded isolated
thunderstorms will continue to to move across the region through
12Z after which Coverage will decrease through about 18Z with
clearing southwest to northeast. Isolated to scattered showers
and thunderstorms will be possible through the afternoon
favoring the higher terrain, but otherwise, VFR conditions will
prevail through the remainder of the TAF period. With the strong
southwesterly flow aloft, Low-Level Wind Shear will affect
mountain TAF sites with some south to southwest winds mixing
down to the surface gusting over 20 kts through about 01Z.

&&

.HYDROLOGY...
Issued at 421 PM MDT Mon Oct 13 2025

The Flood Watch continues for portions of the San Juans and
southern valleys as TD Raymond brings another surge of moisture
from the south . Soil moisture in the watch area is very high
due to all of the preceding rainfall last weekend, therefore
runoff will be more efficient this round. Many rivers, creeks,
and streams in the watch area are anticipated to crest between
midnight and 6AM tomorrow morning meaning the peak of flood
impacts will likely occur in the dark. This can be more
impactful due to the lack of visibility. Use extreme caution if
you are driving in low-lying areas or next to waterways
overnight!

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Flood Watch through Tuesday morning for COZ019-022-023.
UT...None.

&&

$$

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