242
FXUS65 KGJT 031111
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
511 AM MDT Wed Sep 3 2025

.KEY MESSAGES...

- Temperatures trend about 5 degrees above normal through
  Wednesday before a cooler and more active storm system moves
  in by Friday.

- More widespread precipitation is possible on Friday and into
  the weekend as rich extra-tropical moisture moves into the
  region with a potential for heavier rain on the recent fire
  scars.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 337 AM MDT Wed Sep 3 2025

Satellite imagery shows the high pressure extending from the Four
Corners to the north-northwest through Utah, Idaho and Washington
into British Columbia has pulled deep moisture up into the Great
Basin and Oregon, priming the atmosphere for active weather this
weekend across eastern Utah and Western Colorado. With the dry
northerly flow of the eastern flank of the high across the region
today, we`ll see another warm, dry day with temperatures running
about four to six degrees above the climatological normal for early
September. Look for isolated showers and thunderstorms again along
the southern face of the San Juans as the moisture across northern
New Mexico pushes north under the high.

Satellite imagery also shows a shortwave disturbance rotating
around the deep low off the Pacific Northwest has moved inland
over Northern California. Models are in good agreement with this
disturbance undercutting the ridge Wednesday night into
Thursday as it tracks east across northern Nevada into Utah by
Thursday evening, dragging the deep moisture with it into
eastern Utah and Western Colorado. This influx of moisture ahead
of this disturbance will bring increased convection to the
region with scattered to numerous showers and thunderstorms to
the southern mountains and isolated storms farther north along
the I-70 corridor and into the Uintas. With the westerly to
southwesterly moist flow, there is concern for training storms
over the Stoner Mesa fire scar leading to possible flash
flooding and debris flows Thursday. Uncertainty is too high at
this point to issue a watch. Will re-evaluate this on the day
shift today, so stay tuned.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 259 PM MDT Tue Sep 2 2025

A pattern shift will allow for a return of moisture beginning
Thursday afternoon. A trough pushing inland off the Pacific will
begin to break down the high pressure centered over the Four
Corners region. As it does so, moisture will advect into the
TAF period with mostly scattered mid to high clouds across the
region. Isolated showers and thunderstorms will develop over the
San Juan Mountains in southern Colorado between 18Z and 00Z
with lightning and gusty outflow winds the primary
threats.region, first in southeastern Utah before becoming
widespread over the CWA late this week. On Thursday elevated
PoPs are mostly confined to south of I-70, where moisture is
most abundant during the afternoon hours. PoPs in this region
remain elevated overnight, and less tied to the terrain, as a
passing weak wave of energy provides upper-level support while
moisture continues moving in. By Friday PWATs will be
anomalously high across the whole region, peaking near 150% of
normal through Saturday. This means widespread chances for
showers and thunderstorms across the CWA over the weekend, even
outside of the high terrain. A factor adding uncertainty into
the forecast is the impact of a tropical disturbance in the
Pacific, which recently became Tropical Storm Lorena. If the
remnants of Lorena move into the Southwest, there could be
potential for additional moisture advection to occur with the
monsoonal push from the pattern change. However, the forecast
for this is still uncertain between models, so not much can be
said with confidence. Moisture looks to slowly move out of the
area towards the end of the long term. Temperatures are expected
to cool this weekend with the increase in moisture, dropping
highs below normal.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 508 AM MDT Wed Sep 3 2025

Expect VFR conditions and light terrain driven winds through
the TAF period with mostly scattered mid to high clouds across
the region. Isolated showers and thunderstorms will develop over
the San Juan Mountains in southern Colorado between 18Z and 00Z
with lightning and gusty outflow winds the primary threats.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...None.
UT...None.

&&

$$

SHORT TERM...DB
LONG TERM...DB/GF
AVIATION...DB