019
FXUS65 KGJT 151909 CCA
AFDGJT

Area Forecast Discussion...CORRECTED
National Weather Service Grand Junction CO
109 PM MDT Tue Sep 15 2026

.KEY MESSAGES...

- There is a chance for strong to severe storms over the next
  few days, capable of producing hail, gusty winds, and heavy
  rainfall.

- Moderate to heavy rainfall could lead to localized flash
  flooding, rockfalls, and mudslides at times this week.

- Flood Watch in effect for SE Utah and SW Colorado Wednesday
  through Thursday with multiple rounds of heavy rain impacting
  burn scars, slot canyons and areas of susceptible terrain on
  already saturated ground.

- Temperatures run near to around 5 degrees below normal through
  the end of the week.

&&

.DISCUSSION...
Issued at 1258 PM MDT Tue Sep 15 2026

STRONG TO SEVERE STORMS POSSIBLE TODAY:

Storms are already ongoing this morning across southeast Utah
with storms beginning to fire over the western Colorado high
terrain with daytime heating and spreading into some valleys. We
remain plenty unstable and moist as evident in our 18Z GJT
sounding with surface CAPE of around 1400 J/kg and a forecast
surface CAPE around 2000 J/kg. Plenty of shear out there as well
with 30 kts so enough to sustain updrafts. Like yesterday, we
could see strong to potentially severe storms, capable of large
hail and damaging winds in addition to heavy rain and frequent
lightning. Hi res CAMs seem to indicate storm coverage and
intensity ramping up late this afternoon into the evening hours.
We remain in the favored right entrance region of the upper level
jet giving us that dynamic forcing needed to support robust
convection.

FLOOD WATCH WEDNESDAY AND THURSDAY:

A strong low pressure trough remains to our west with high
pressure across the southeastern CONUS, keeping our CWA in the
direct moisture feed from the south that stretches from the Baja
across Arizona and New Mexico through the Four Corners and up
into eastern Utah and western Colorado. PWAT anomalies will
remain around 200 percent of normal through the end of the week
with a surge in moisture Wednesday evening through Thursday
afternoon where PWAT anomalies surge close to almost 300 percent
of normal, mainly across southwest Colorado. Areas around SW
Colorado have received 1 to 2 inches of rainfall based on
reports over the last 24 hours so this area remains saturated.
Storm coverage will become more widespread Wednesday and
Thursday due to some robust shortwaves moving through Wednesday
afternoon as well as another Wednesday night into Thursday.
Given the surge in deeper moisture, already saturated ground
from recent rains, and burn scars in the region...decided to
issue a Flood Watch for portions of SW Colorado including the SW
CO valleys and San Juan mountains from Wednesday afternoon
through Thursday night. Also, issued a Flood Watch for portions
of SE Utah from midnight tonight through 6 am Thursday. This
includes the Babylon, Ferris, Gold Mountain and Elk burn scars
in particular among other susceptible flood prone locales. Heavy
rain is a near certainty with any storm that develops so other
areas outside the Flood Watch could see impacts, but the Flood
Watch is for where the best potential and highest confidence
lies. Cannot rule out strong to severe storms as well given the
dynamic forcing of the jet, instability and shear...but this may
all depend on the amount of cloud cover as deeper moisture moves
in Wednesday evening through Thursday night.

FRIDAY AND BEYOND:

Friday onward, forecast confidence decreases. Models are in
poor agreement as to what happens once the West Coast trough
ejects to the northeast, with some solutions building a ridge,
and others developing a Rex Block over the Southwest. Ensembles
do indicate a gradual drying trend, but keep PWATs of 100-150%
of normal around through the weekend. That`s enough to keep a
chance of isolated to scattered terrain based showers and
storms in the forecast. However as we`ve seen with this type of
pattern in the past, models tend to be too quick to exit this
moisture and we could see stronger storms possible along that
moisture gradient as dry air tries to move in from the west.
With abundant cloud cover and shower activity expected through
the end of the week, temperatures will run near to around 5
degrees below normal.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1141 AM MDT Tue Sep 15 2026

Showers and thunderstorms are expected to develop during the
afternoon. TEMPO groups were added for most sites with the main
threats being locally heavy rain reducing visibility along with
gusty winds. Lesser coverage of showers and storms are expected
overnight with PROB30 groups included in most groups. This
active pattern will continue for the 24 hour period. MVFR and
IFR conditions will be likely in showers and thunderstorms.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Flood Watch from Wednesday afternoon through Thursday evening
     for COZ018-019-021>023.
UT...Flood Watch from midnight MDT tonight through late Wednesday
     night for UTZ022-028-029.

&&

$$

DISCUSSION...MDA/TGJT
AVIATION...RJ/TGJT