608
FXUS65 KGJT 131145
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
545 AM MDT Sun Jul 13 2025

.KEY MESSAGES...

- Temperatures increase today across the region. Afternoon
  thunderstorms develop along the Divide favoring the San Juans.

- Coverage of afternoon showers and storms will gradually
  increase as the week wears on.

- Outflow winds and dry lightning remain a threat today and
  tomorrow, as thunderstorm chances spread across additional
  terrain.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 434 AM MDT Sun Jul 13 2025

Northwesterly flow continues to spill across the front side of high
pressure anchored over the Southwest this morning. A shot of cloud
cover passed over southwest Colorado during the overnight hours,
delivering a brief bit of rain to Pagosa Springs. I suspect it might
have evaporated before anyone wakes up to this discussion. Afternoon
heating will bump up isoheights and shift the high eastward as
expected. This should open the door for a weak plume of moisture to
drift northward along the Divide. Thunderstorm chances will spread
northward today along this moisture including the San Juans, Central
and Northern Mountains. Wetting rain will still be hard to come by
thanks to the persistent dry lower atmosphere. Thus, gusty
outflow winds and dry lightning remain a threat again today.
Unfortunately, this will come as bad news for those hoping for
relief from local wildfires. Afternoon heating is expected to
fan more smoke to the region as well. High res smoke forecasts
keep the densest smoke across southwest Colorado and southeast
Utah today. While dense smoke will remain confined to areas
immediately downwind of fires, some smoke will remain visible to
much of the CWA for the foreseeable future.

Temperatures will notch upward today and tomorrow too, as we likely
crest the 100 degree mark again here in the Grand Valley. Utah
deserts are expected to push well past that mark again today
too. Deterministic models are keen to keep this air mass in
place, which means temperature relief is unlikely until we can
get some cloud cover and rainfall mixing down some cooler air.
The bigger longwave pattern offers no help either, keeping
frontal activity well to the north this week. Monday looks like
a rinse and repeat of today as additional moisture bubbles
beneath the high along the southern Divide. Up north, a weak
clipper system does offer some additional moisture Monday
afternoon. This will increase thunderstorm coverage on regional
terrain, thereby increasing the dry lightning and outflow wind
threat. Hot and dry July continues.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 356 PM MDT Sat Jul 12 2025

The synoptic pattern really doesn`t change much through the
seven-day forecast with high pressure being the driving force
behind much of our weather for the week to come. We`ll be
following two main storylines throughout much of the upcoming
week.

1. Unseasonably Warm Temperatures

Temperatures remain 5-10 degrees above normal for mid-July
through at least mid week. At that time, a shortwave trough is
progged to move track across the Pacific Northwest into the
Northern Plains. Locally, this wave will flatten out the ridge
overhead and could help temperatures cool off a few degrees.
Despite this, the current forecast calls for normal to above-
normal temperatures through the work week.

2. Increasing Moisture

Global ensembles continue to show signs of moisture slowly
seeping back into the region, first along the Divide from the
southeast, then from the north as the aformentioned shortwave
leads to zonal flow aloft, and then from the south once more
late in the period. PWAT anomalies of 100-125% of normal will
not support the widespread rains we need, but will support
convection over the high terrain each afternoon. Storms will
continue to be capable of producing gusty outflow winds, fire
starts, and small hail at times. There are hints of stronger
moisture advection late in the week/next weekend, but it is
still too early to tell if this will be the pattern that ushers
in the monsoon. There`s too much spread between global ensembles
to have much forecast confidence come next weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 540 AM MDT Sun Jul 13 2025

VFR conditions will continue this morning across the region. Mid
and upper level clouds will develop on the terrain today with a
few thunderstorms possible along the Divide favoring the
southern mountains. Left some PROB30 TSRA in TAFs to account for
isolated development. Storms will likely only produce lightning
and gusty winds today. Smoke will remain visible across the
region today, with concentrations immediately downstream of
fires in southwest Colorado and southeast Utah. Winds will be a
bit lighter today under the influence of high pressure, but
terrain based gusts to around 20 mph are possible on the
mountains. VFR conditions are expected to return late tonight to
close out this TAF period.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...LTB
LONG TERM...KAA
AVIATION...TGJT