874
FXUS65 KGJT 120552
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1152 PM MDT Sun Aug 11 2024

.KEY MESSAGES...

- Showers and thunderstorms continue each afternoon and evening
  until further notice with gusty outflow winds, small hail, and
  frequent lightning possible.

- Heavy rain rates with storms will bring an enhanced threat of
  flash flooding and debris flows today through early next week.
  Saturated soils and steep terrain will be most susceptible to
  flooding.

- Temperatures will remain near to several degrees below normal
  thanks to the abundance of clouds and showers.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 235 PM MDT Sun Aug 11 2024

Storms have been slow to re-develop this afternoon, but we`ve
finally seen some cumulus popping and cells firing in the last
hour or so. CAM guidance remains consistent in projecting
another active day as a shortwave embedded in the westerly flow
aloft tracks across eastern Utah and western Colorado through
this evening. This system and the continued presence of a 60 to
70 kt jetstreak overhead will act on the abundance of deep
moisture in place as precipitable water values remain in the
0.75 to 0.90 inch range across the western zones with 1 to 1.20
inches in the central and eastern zones. Scattered convection
is expected through around 6 PM this evening before a line of
showers and storms pushes into southeast and east-central Utah.
This swath of precipitation will push through the Western Slope
into the midnight hour before another cluster of showers moves
into the Four Corners region later tonight. As has been the
trend the last several days, storms will be capable of producing
gusty outflow winds to around 45 mph, small hail, frequent
lightning, and of course periods of moderate to heavy rain.
Given the well saturated soils from the last several days of
precipitation, flash flooding will be possible. Therefore, a
Flood Watch remains in effect through 10 PM this evening.

Isolated shower activity is expected to prevail into mid Monday
morning before we see daytime heating kick off another round of
scattered showers and thunderstorms Monday afternoon. While
we`ll lose the jet tomorrow, yet another embedded wave will push
through, leading to a couple of stronger storms. Opted to hold
off on any additional flood highlights for now but, as always,
be sure to stay tuned to the latest forecast for any updates.
Nocturnal showers and some embedded storms once again look
likely for Monday night as the wave exits to the east while yet
another approaches from the west. Outside of any convection
through the short term, look for dry weather and passing clouds.
Temperatures will begin to drop back to below normal area-wide
thanks to the abundance of clouds and showers.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 235 PM MDT Sun Aug 11 2024

The combo of low pressure driving into the PacNW and a monsoon plume
will maintain a swath of anamolous moisture stretched along the spine
of the Rockies on Tuesday. Widespread showers and storms are
expected, once again, with nocturnal storms persisting through the
night thanks to upper level support. The trough passage, though,
will nudge high pressure into eastern Texas/Louisiana by Wednesday,
which, in turn, shifts both sources of moisture east of the Divide.
A new area of high pressure builds back in over the Desert Southwest
in the wake of Tuesday`s wave. This hot and dry air mass will work
its way into the CWA from the southwest, reducing storm coverage
across the Four Corners and lower valleys on Wednesday. However,
lingering moisture will still be sufficient for afternoon convection
to flourish atop the high terrain. Ridge of high pressure shifting
overhead on Thursday and Friday will continue to support dry air
advection across the Western Slope, as such, we`ll see a downturn in
terms of storm coverage and likely rainfall intensity for the end of
the work week. Confidence in forecasting the evolution of the high
decreases leading into next weekend. Half of the ensemble cluster
analyses show above average moisture across the Western Slope by
Days 6 and 7, which would allude to the monsoon redeveloping.
However, subtle shifts in the high`s center may keep the monsoon
plume to our west, and a dry air mass overhead.

Temperatures during the long term start off approximately 3 to 8
degrees below normal, thanks to cloud cover and the abundance of
moisture. We`ll see a rise mid week through Friday as the new area
of high pressure builds overhead, with highs hovering right around
normal as we end the work week.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1152 PM MDT Sun Aug 11 2024

Showers with embedded thunderstorms will continue through the
early morning hours across southeast Utah and southwest Colorado
but will decrease in coverage and intensity, coming to an end by
10Z for the most part. Scattered to broken skies will remain
through the morning with storms redeveloping over the high
terrain by 18Z Monday. Best potential for storms appears to be
across eastern Utah and into northwest Colorado late Monday
afternoon into the evening as a disturbance tracks across that
area with less coverage across western Colorado with exception
of some high terrain sites.

&&

.HYDROLOGY...
Issued at 1152 PM MDT Sun Aug 11 2024

Monsoonal moisture will keep showers and thunderstorms over the
region through at least mid week with rainfall rates of 1 to 2
inches per hour possible with storms. Given how saturated soils
have become over the recent days, there is increased potential
for flash flooding and debris flows across much of the area.
Stay weather aware over the coming days, especially if you live
in terrain vulnerable to flooding, or are planning to recreate
outdoors.

Stay tuned to the latest forecast updates for any additional
flood watches, warnings, and / or advisories over the coming
days.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MMS
LONG TERM...ERW
AVIATION...MDA
HYDROLOGY...TGJT