-- Discussion containing changed information from previous version are highlighted. --
826
FXUS65 KGJT 152327
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
527 PM MDT Sat Jun 15 2024

.KEY MESSAGES...

- A few isolated showers, maybe a quick thunderstorm, possible
  this afternoon mostly in the mountains.

- Hot and dry weather continues as southwesterly winds pick up
  resulting in critical fire weather conditions on Sunday and
  Monday.

- The Red Flag Warning is in effect for southeast Utah and
  portions of southwest and west-central Colorado for Sunday and
  Monday afternoon.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 307 PM MDT Sat Jun 15 2024

The synoptic pattern continues with a longwave trough/low pressure
over Western Canada and ridging over the Eastern CONUS. A shortwave
system digging down into the Pacific Northwest Sunday will tighten
the gradient aloft generating stronger winds that will mix down
through the day. By Monday morning, this low will begin its eastward
trek across Idaho towards Montana and Wyoming further increasing the
pressure gradient over the region.

With the residual moisture across eastern Utah and Western Colorado
and a weak shortwave moving overhead, isolated showers and
thunderstorms have developed this afternoon mostly over the
mountains. Look for this convection to continue into the early
evening before ending with some areas seeing the activity becoming
more scattered. This morning`s sounding indicated significant
moisture remained in the area with a 0.72 pwat, and forecast heating
generated CAPE in excess of 500 which agreed well with the DESI
solutions. The high resolution models were more bullish on the
convection and needed only slight tweaks to bring it up to match
observations; hence, went with them over the other guidance. Models
continue to advect much drier air into the region to kill convection
tomorrow, but can`t rule out an isolated shower in the mountains,
especially up north where yet another shortwave passes.

The dry air over the region with warm temperatures will drop the RH
into single digits to low teens. Combined with the stronger winds
mixing down Sunday, Critical Fire Weather conditions will develop
from late morning into the evening hours. A Red Flag Warning is in
effect for eastern Utah and Western Colorado along and south of the
I-70 corridor to the Arizona and New Mexico Borders beginning at 11
AM running through 10 PM. A Red Flag Warning means that critical
fire weather conditions will occur. A combination of strong winds,
low relative humidity, and warm temperatures can contribute to
extreme fire behavior. If you plan to be outside in the these areas,
exercise care with vehicles and equipment that can generate sparks,
and heed all fire restrictions in place.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 307 PM MDT Sat Jun 15 2024

As mentioned in previous discussions, a mid-level trough will move
into the northern Rockies on Monday driving a cold front to
northeast Utah/extreme northwest Colorado later in the day. Strong
southwesterly prefrontal winds combine with low relative humidity
and above normal heat to create critical fire weather conditions
across the entire region. A Red Flag Warning remains in place for
much of the southern portion of the forecast area where fuels are
critical.

The trough moves to the northern High Plains Monday night while its
cold front continues south overnight. However, model consensus
indicated insufficient moisture will be available to generate
showers/thunderstorms with its passage. The pressure gradient eases
over the area Tuesday in the wake of this system so less breezy and
cooler conditions are expected, though flow will continue from the
southwest as a long wave trough settles over the West.

Temperatures rebound as the trough persists to the west during the
remainder of the work week. Wednesday will be dry and warmer except
for a slight chance for afternoon showers/thunderstorms along the
northern and central Colorado mountains along the Continental
Divide. Diurnal shower/thunderstorm chances increase over the San
Juan and central Colorado mountains on Thursday as high pressure
over the central Plains causes moisture to advect into the area from
the southeast. This pattern holds on Friday and, as a result, shower
activity is expected to spread into the northern mountains and
farther west as well. While mountains are favored, chances extend
into the high valleys and lower elevations of southwest Colorado as
well. Meanwhile, temperatures will settle out at around 5 to 10
degrees above normal at the end of the week.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
-- Changed Discussion --
Issued at 527 PM MDT Sat Jun 15 2024

High based showers and thunderstorms with gusty outflow winds
will continue to bring through the evening hours before things
settle down or move east of the divide. KGUC and KASE may have
the best chance of a nearby passing storm through 02Z looking at
the latest radar trends but even virga can throw out some gusty
winds. Quiet overnight conditions will then turn to a
widespread gradient wind threat on Sunday with gust of 25 to 40
mph possible by early afternoon and persisting through sunset.
Otherwise VFR conditions are expected.
-- End Changed Discussion --

&&

.FIRE WEATHER...
Issued at 234 AM MDT Sat Jun 15 2024

Strong southwest winds and low relative humidity Sunday and
Monday remain in the forecast and will generate critical fire
weather conditions for both days. Model consistency has been
steadfast in these stronger winds and dry conditions materializing
so confidence continues to grow with the forecast. The latest
HDWI still peaks just below the 90th percentile for this time of
year so decided to upgrade the Fire Weather Watch to a Red Flag
Warning for Sunday for southeast Utah and portions of southwest
Colorado and west- central Colorado from late Sunday morning
through Sunday evening. Winds are forecast to be stronger on
Monday so another day of critical fire weather conditions is
expected. With that in mind, went ahead and issued another Red
Flag Warning for the same areas and times for Monday.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Red Flag Warning from 11 AM to 10 PM MDT Sunday for COZ203-207-
     290>293.
     Red Flag Warning from 11 AM to 10 PM MDT Monday for COZ203-207-
     290>293.
UT...Red Flag Warning from 11 AM to 10 PM MDT Sunday for UTZ490-491.
     Red Flag Warning from 11 AM to 10 PM MDT Monday for UTZ490-491.

&&

$$

SHORT TERM...DB
LONG TERM...NL
AVIATION...TGJT
FIRE WEATHER...TGJT