030
FXUS65 KGJT 081118
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
518 AM MDT Sat Jun 8 2024

.KEY MESSAGES...

- Afternoon showers and storms will favor the north today, but
  will expand to include all terrain features Sunday and Monday.
  Main threats will be gusty winds and lightning.

- Temperatures will cool to near normal values by Monday before
  warming back to 10-15 degrees above normal mid to late next
  week.

- High pressure from Tuesday onward will keep conditions hot,
  dry, and quiet.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 316 AM MDT Sat Jun 8 2024

It`s hard to believe this is early June and not July or August, with
how late-summer, monsoonal conditions appear to be. The PWAT value
in the 00z Grand Junction sounding came in at 0.73 inches, which is
in the top 10% of PWAT values for that date and time, and is much
closer to a normal PWAT in late July. This moisture does seem to be
focused mainly north of the I-70 corridor, which is also where some
very modest instability has lingered into the night. This, in
combination with some weak dynamic lift from a passing shortwave to
the north, has allowed for convection to continue well into the
night across Northwest Colorado. Very dry surface levels have
limited the amount of moisture making it to the ground, but has
resulted in some quite gusty winds. As the shortwave providing the
necessary lift continues tracking east, so too will these showers,
and will be east of the Divide by daybreak.

Ridging is expected to push northwestward into the Great Basin
today, with the ridge axis directly over the Four Corners. This will
push drier air across southeast Utah and southwest Colorado today,
limiting chances of clouds and showers, and allowing temperatures to
climb 10 or so degrees above normal. Meanwhile, areas north of I-
70, will see plenty of low to mid level moisture still in place.
Guidance is also hitting at pockets of 500-1000 J/kg of CAPE,
meaning there will be plenty of instability to play with. Another
shortwave is expected to move across the north this afternoon and
evening, providing some modest dynamic lift to combine with daytime
heating and fire off another round of afternoon convection. Dry
surface air is forecast to remain stubbornly in place, meaning the
main threats will be gusty winds and lightning, although there is
still a chance for some moderate to heavy rain across the higher
terrain. As this wave moves east of the Divide tonight, expect a
downturn in shower activity across the area as high pressure
reasserts itself. A tap of subtropical moisture being pulled north
by the clockwise flow associated with the ridge will help fuel more
widespread activity on Sunday. The remnants of the Baja cutoff low
will be an open wave over the Desert Southwest on Sunday afternoon,
providing some modest lift across the southern portion of the CWA,
while yet another passing wave to the north will help with
convection over Northeast Utah and northwest Colorado. Expect to see
activity fire along the terrain first before drifting off over
adjacent valleys. Multiple days of uninterrupted moisture across the
north will see increasing chances of heavy rain with afternoon
convection, along with the usual threats. Gusty winds and lightning
remain the main threat across the south.

High temperatures this afternoon will be similar to what we saw
yesterday, with the desert valleys of Southeast Utah standing the
best chance to see triple digits thanks to drier air. Portions of
northeast Utah and northwest Colorado, along with the Central Divide
Mountains, stand the best chance to see cooler temperatures this
afternoon thanks to clouds and storms. By tomorrow, with increased
moisture across the entire region and greater coverage of clouds and
storms, temperatures will run around 5 degrees cooler, though still
above normal. Overnight lows will remain mild.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 316 AM MDT Sat Jun 8 2024

The next closed low will be dropping off the Baja Coast Sunday Night
into Monday as the prior Baja low works across New Mexico to the
Southern High Plains during this time. Shearing energy from this low
and the tail end of a northern stream system will continue to
interact with above normal moisture over the area to produce
afternoon showers and thunderstorms. The cloud cover and
precipitation should contribute to the coolest day of the forecast
on Monday through temperatures will remain slightly above normal.
High pressure builds back into the 4 Corners region on Tuesday and
persists through Thursday before the Baja low begins to lift into
the Southwest. So another string of hot and mainly dry days will
return until the late week period when this low brings the next
chance of precipitation and likely cooling temperatures back toward
normal. There are some models variances as we get out to the late
week time frame and beyond. These include the timing and exact
trajectory of the SW low as it moves across the Rockies into the
weekend. An anomalously strong system will be arriving into the
PacNW by late Friday and should dig deeper across the West into
early next week. CPC guidance hints at the changes coming upstream
and this system could be strong enough to bring more Spring-like
weather back to our region in the form of gusty gradient winds. The
scenario would definitely heighten fire weather concerns and will be
something to monitor over the next several days of models and
associated ensemble runs.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 515 AM MDT Sat Jun 8 2024

Some lingering midlevel clouds and a shower or two are moving
through the higher terrain along the Colorado Divide at this
hour, but should be east within the next two hours. Winds this
morning will be light and terrain driven outside of the
influence of these showers. Mountain showers and storms will
fire this afternoon, favoring the terrain along and north of
I-70, and impact terminals including KVEL, KHDN, KASE, and KRIL.
These showers and storms will produce gusty and erratic winds
along with lightning and potentially brief heavy rain. South of
I-70 look for gusty southwesterly winds up to 25 knots this
afternoon. All activity will die down after sunset, with winds
once again becoming light and terrain driven. VFR conditions
will prevail for the next 24 hours.

&&

.HYDROLOGY...
Issued at 332 PM MDT Fri Jun 7 2024

High elevation snow will continue to melt under these anomalously
warm spring conditions. Cloud cover from today`s showers and storms
could suppress the rate of snowmelt, however, additional precip
would have the opposite effect. Thus, some areas under today`s
passing clouds may see some temporary relief in runoff, while
localized basins will see a ramp up from measurable rain and/or rain
on snow. Due to these highly localized influences, confidence in how
major streams and rivers respond remains low.

Following current guidance and river trends, we`re expecting an
increase in flows along the Colorado Headwaters. More specifically,
Gore Creek, Eagle River and the Roaring Fork River Basin have all
shown an increasing trend over the last 24 hours. Current advisories
all remain in place through the weekend, and we`ll continue to
monitor for any expansions to highlights or for any chance these
could upgrade to a warning.

Flow/stage in the Elk River in Routt County have slowed down, coming
in just under Action Stage last night/this morning. Forecasts have
dropped below minor flood stage, however, I am hesitant to take down
the warning due to uncertainty in rain on snow potential and another
crest approach minor flood stage tonight/Saturday morning. Improving
conditions are anticipated following this weekend, as large diurnal
swings taper off next week.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...BGB
LONG TERM...15
AVIATION...TGJT
HYDROLOGY...ERW