639
FXUS65 KGJT 062340
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
540 PM MDT Mon Oct 6 2025

.KEY MESSAGES...

- A Freeze Warning is in place for the Yampa and White River
  Basins through Tuesday morning.

- Non zero chances for isolated showers and thunderstorms on the
  San Juans Tuesday and Wednesday.

- Drier conditions continue through Wednesday. However, moisture
  returns Thursday and beyond, bringing the potential for
  widespread precipitation.

&&

.UPDATE...
Issued at 537 PM MDT Mon Oct 6 2025

Upgraded the freeze watch to a warning for the Upper Yampa River
Valley and White River Valley near Meeker for temperatures in
the 27-30 degree range in many areas overnight.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 302 PM MDT Mon Oct 6 2025

Drier conditions continue to develop this afternoon on the backside
of the trailing edge of a system working across the Great Lakes.
Light west-northwest winds, abundant sunshine, and some fair weather
cumulus fields over the terrain are making for a pleasant early
autumn day here on the West Slope. Cooler air, light winds, and
clearing skies will drop temperatures again tonight across the
region. The Freeze Watch for the Central Yampa Basin is still
in effect for Tuesday morning, where temperatures will drop into
the upper 20`s. Elsewhere in our other freeze susceptible
valleys, climatology is on our side and temperatures will remain
above the freezing threshold.

High pressure continues to develop across the Rockies and on the
Plains Tuesday afternoon. This will send area temperatures back up
near normal Tuesday. Abundant sunshine will once again make for a
nice autumn day. Return flow from the surface high on the
southern Plains will push some weak moisture into the
southeastern portion of our CWA around Pagosa Springs. A few
clouds will come about, along with non zero precipitation
chances on the San Juans. Wetting rains are not likely though.
Southwesterly flow and subsidence will keep lows on the warm
side of climatology Tuesday night, likely not requiring
additional freeze headlines.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 302 PM MDT Mon Oct 6 2025

The dry air residing over us is expected to budge as the Rex Block
to our west diminishes, the California closed low being absorbed
into the descending PacNW wave. Upper-level flow gains more of a
southerly direction as a result, pulling the Desert Southwest pool
of anomalous moisture northwards. This pool moves slow enough that
Wednesday will still be on the drier side with little more than
orographically-driven isolated showers over the San Juans expected,
as far as precipitation goes. But as we progress into the late-week
period, PWAT`s will be on the rise. Latest model guidance is higher
than it was 24 hours ago, with both the ECMWF and GEFS reaching
PWAT`s 250-300% of normal by Friday (and localized higher values
according to the former). Confidence is high in a widespread
precipitation event from Thursday through Sunday as a result. Rain
will dominate due to warming low- and mid-level temperatures.

With lacking instability coinciding with this strong surge of
moisture, current forecasts look to favor more of a stratiform and
steady rainfall event, though stronger embedded thunderstorms will
be possible. Because of the juicy atmosphere from Thursday through
the weekend, the potential for flash flooding is there. In the event
of a stratiform-dominated storm setup though, flash flooding impacts
should be less prominent. Focal points would be on burn scars, stray
embedded thunderstorms where localized rainfall would be heavier,
and areas experiencing longer periods of moderate rainfall. While
stratiform is the higher likelihood storm mode, should instability
become more favorable or frontal passage occur sooner (thus
coinciding better with the stronger moisture pool), more intense
rainfall rates associated with discrete thunderstorms could pose a
heightened flash flood risk. Deterministic models are hinting at
relatively slow storm motion as well, which would exacerbate the
threat.

With low certainty in storm mode right now, I wouldn`t go betting
one way or another on how things will set up Thursday onwards
just yet. Stay up-to-date with the latest information and
guidance, especially as we begin to see high-resolution model
data become available over the next few days. Regardless of what
scenario unfolds, it is imperative to stay weather aware
throughout this event. If you are planning to be outdoors,
ensure you have a way of receiving weather alerts and have a
plan in the event that inclement weather moves overhead.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 519 PM MDT Mon Oct 6 2025

A few mild showers have developed over the eastern portions of
the CWA, but impacts to terminals are not expected. Winds are
gusting to 20-25 kts at many terminals, but winds should calm as
we head into the evening period. Otherwise, look for clouds to
clear out overnight into tomorrow, and VFR conditions should
continue.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Freeze Warning from midnight tonight to 10 AM MDT Tuesday for
     COZ002.
UT...None.

&&

$$

UPDATE...15
SHORT TERM...LTB
LONG TERM...BW
AVIATION...TGJT