406
FXUS65 KGJT 040550
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1150 PM MDT Wed Sep 3 2025

.KEY MESSAGES...

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

- Scattered showers and storms return to the forecast tomorrow
  becoming more widespread this weekend.

- The potential for burn scar flash flooding increases into the
  weekend.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 228 PM MDT Wed Sep 3 2025

Isolated to scattered thunderstorms are ongoing around the San
Juan mountains and in southeastern Utah. The activity seems to
have been a bit underestimated by CAMs, but even so the
convection has been pretty limited while dry air is still in
place. Tomorrow monsoonal moisture begins to make a push into
our CWA as a trough moving inland off the Pacific supports the
break down of a ridge of high pressure. Tomorrow most of the
increased moisture, and subsequently the elevated precipitation
chances, will be south of I-70 while the synoptic setup supports
moisture advection primarily into this part of the CWA. PoPs
are expected to remain elevated overnight Thursday into Friday
as a weak wave of energy provides additional support.
Temperatures begin to cool tomorrow as moisture moves into the
area, but only by a few degrees. In the northern half of our
CWA, Where moisture will still be limited, highs will be around
5 degrees above normal. The southern half of our CWA will be
closer to normal. Temperatures will continue to cool beyond the
short term period.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 228 PM MDT Wed Sep 3 2025

Monsoonal moisture remains in place through the weekend with
scattered to widespread showers and storms likely. Weak
northwesterly flow follows the shortwave`s passage on Thursday
night helping precipitation chances spread northward. It may
take some time for the lower levels to saturate so the highest
precipitation chances remain south of I-70, but as soon as the
vertical column moistens it will be game on area wide. It`s
looking like this will happen on Saturday, but there may be
refinements in the forecast over the next couple of days as the
CAMs are introduced into model blends. With drier near-surface
air to work through north of I-70 on Friday, any storms that
develop will be capable of producing gusty outflow winds up to
45 mph. South of I-70, gusty outflow winds will become less
likely Friday and beyond.

The peak of this monsoonal push occurs on Saturday with
widespread showers and storms becoming more likely. A weak
shortwave is also progged to pass through later in the day on
Saturday which could be enough to support a few stronger storms
capable of producing large hail up to 1" in diameter. There is
also the potential for heavy rainfall with the added synoptic
support teaming up with PWATs 150- 175% of normal. The one
caveat here is that the GEFS is running drier across northwest
Colorado on Saturday so that will be something to watch. This
signal is not present in the ECMWF ENS.

If heavy storms/downpours track over recent burn scars,
localized flash flooding and debris flows are possible through
Sunday.

Moisture begins lifting north away from the local area on
Sunday into Monday. Model guidance diverges beyond this
timeframe so we will have to wait and see which direction the
models trend over the next couple of days. High temperatures
remain seasonable through much of the extended forecast.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1131 PM MDT Wed Sep 3 2025

Expect mostly VFR conditions with mid-level scattered to broken
skies across the region through the TAF period. The exceptions
will be showers and thunderstorms moving in from the southwest
after 15Z with possible impacts to KDRO and KTEX after 18Z and
KMTJ and KCNY after 23Z.Winds will be generally light terrain
driven through the period with a few westerly to northwesterly
gusts in the lower valleys after 18Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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