293
FXUS65 KGJT 211119
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
519 AM MDT Thu Aug 21 2025

.KEY MESSAGES...

- Near-record heat lingers through Saturday, before increased
  clouds and showers bring a significant cool-down for early
  next week.

- Isolated to widely scattered convection is expected over the
  higher terrain today, with gusty winds and lightning still the
  main threats. Light to moderate rainfall will be possible over
  the San Juans.

- Moisture is expected to continue increasing over the next
  several days, with widespread shower and storm activity
  expected. Potential for heavy rain and debris flows over burn
  scars will increase from Sunday into early next week.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 247 AM MDT Thu Aug 21 2025

As far as the synoptic pattern is concerned, very little has changed
for the Four Corners region, as high pressure is still firmly in
control. That said, on a finer scale, things are starting to change.
The much anticipated moisture has begun to sneak into the region,
indicated by rising dew points and lingering clouds and showers
across southwest Colorado, as well as increasing PWATs on the Grand
Junction upper air soundings. The best moisture is still to our
west, but will be working its way east over the next several days.
Coverage of showers and storms will increase day by day, with
isolated to scattered showers and storms today followed by more
widespread activity tomorrow afternoon. Dry surface levels today
will keep the chances of wetting rain limited (<20%), although some
spots of light to moderate rainfall will be possible for the
southern mountains and highest terrain of the eastern Uintas. Of
more concern will be gusty outflow winds and lightning. Chances of
wetting rain come up tomorrow afternoon (20-40%), especially over
the San Juans, meaning we`ll start to see a transition away from the
gusty wind threat and toward a heavy rain threat.

Temperatures remain in near-record territory today and tomorrow,
running 10-15 degrees above normal. Highs tomorrow will drop a
degree or two in response to the increasing moisture and shower
activity, but we really won`t see relief from the heat until Sunday
and beyond.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 247 AM MDT Thu Aug 21 2025

Saturday the moisture could get shunted slightly to the south by a
passing trough, but overall not much changes. Temperatures drop by a
few degrees overall although still above normal. On Sunday, the
moisture once again fills back into the high pressure that begins to
migrate southward. This could be the point at which we see more
measurable rain and the chances for heavy rain increases. The longer
the moisture stays around the better are the chances for beneficial
rainfall. Increasing rainfall rates would be an issue with the
recent burn scars and other susceptible spots, so debris flows
cannot be ruled out during this stretch. One unknown is how the very
dry soils are going to react to any rainfall. Early next week the
high continues southward, but moisture remains in our area under the
large- scale ridge. Like with every moisture push morning cloud
coverage will have a significant impact on whether strong convection
forms in the afternoon or a more stratiform event occurs. If daytime
heating is at a maximum, some storms will likely bring heavy showers
while cloudiness will bring a more soaking type of rain.
Temperatures will cool substantially from Sunday into next week,
thanks to the lingering moisture and cloud cover. Current guidance
has temperatures falling to close to 10 degrees below normal by the
middle of next week, which, along with the moisture, will be a
welcome relief.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 517 AM MDT Thu Aug 21 2025

Winds will remain light and follow typical terrain driven
patterns through the next 24 hours. Mid and high level clouds
will pass through, as moisture increases across the area. The
southern mountains and the eastern Uintas will see increased
coverage today, impacting KTEX and KDRO in particular, with
gusty winds and lightning the main concerns. Smoke from the
Derby Fire will lead to periods of reduced visibility at KEGE
and KASE. VFR conditions will prevail, though occasional drops
to MVFR due to smoke or brief heavy rainfall will be possible.


&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...BGB
LONG TERM...KJS/TGJT
AVIATION...TGJT