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000
FXUS65 KGJT 132020
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
220 PM MDT Sat Apr 13 2024

.KEY MESSAGES...

- Much above normal temperatures can be expected again on Sunday
  along with an increase of afternoon winds with gusts of 25 to
  35 mph possible.

- Bigger changes arrive Monday as the next storm emerges from
  the Intermountain West bringing mountain snow and valley rain
  Monday into Tuesday.

- Monday will be much cooler followed by a slow warmup the
  remainder of the week. Moisture moving through the zonal flow
  aloft looks to keep a threat of showers over the North through
  Saturday.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 220 PM MDT Sat Apr 13 2024

Temperature really are not too far off from this time yesterday
and should be fairly similar tomorrow before bigger changes
arrive to start the week. The system responsible for this
change is still off the NorCal coast feeding a bunch of moisture
into the Sierras and coastal areas north of LA. The best height
falls on the H500 13/12Z hand analysis map were to the
southeast of the main circulation. This suggests the system will
continue to dig down through SoCal overnight as the main jet
core emerges over the Great Basin by sunrise. This will also
cause the energy in the system to split into two pieces which
will swirl around each other as it progresses through the
Intermountain West tomorrow into tomorrow night. Mid level winds
will be on the increase due to the upstream height falls and as
we warm up tomorrow will be tapping into this energy. Expect
windier conditions on Sunday than the past few days with gusts
in the 25 to 35 mph range over much of the eastern Utah and far
western Colorado valleys in the PM hours. The upstream terrain
looks like it will soak up a lot of the moisture and this system
will have to wait until it taps the Gulf to get recharged.
There will be some light showers/virga likely forming in the
pre-dawn hours over the eastern Utah mountains and valleys as a
cold front lift northward into the region and begins to release
some of the available instability. Amounts through the sunrise
Monday look negligible attm however. Temperatures this
afternoon and again tomorrow should stay in the 8 to 13 degrees
above normal for mid April which will help melt that snowpack.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Issued at 220 PM MDT Sat Apr 13 2024

The large cutoff Pacific low that we`ve been discussing over the
last several days will be on our doorstep Monday morning. Strong
southwesterly ahead of the low will maintain breezy conditions
through the morning hours, especially across the southern half of
the area, as well as help enhance the dynamic lift associated with
this system. And this low does have some quite substantial dynamics
associated with it, but alas there is minimal moisture to work with.
The limited moisture combined with the quick moving nature of this
system, which is expected to traverse the region in 12-18 hours,
will limit snow accumulations to just a few inches at the highest
elevations through Monday evening. Valley locations can expect light
rain showers during this period as well.

As the low ejects into the Plains late Monday night it taps into
deeper Gulf of Mexico moisture that is forecast to wrap around into
northern portions of the forecast area. Cooler air on the back side
of this system, increased moisture, and favorable orographic flow
will lead to a substantial increase in snow activity for the
northern and central Divide mountains Monday night into Tuesday
morning. On top of the 1-3 inches forecast to fall during the day,
the San Juans can expect another 2-4 inches by Tuesday morning at
elevations above 9500 feet. For the central and northern Divide
mountians, locations above 9500 feet can expect an additional 6-12
inches by Tuesday morning, with the Park Range currently favored to
see highest storm totals. The magic of late season snowstorms is
that roads often fair better than expected due to warm surface
temperatures melting snow almost as quickly as it accumulates.
However, these substantial accumulations occurring overnight could
lead to a period of messy driving over mountain passes such as Vail
and especially Rabbit Ears on Tuesday morning. While it is still too
early to issue highlights, do stay tuned for updates as winter
highlights for the northern and central mountains are looking
increasingly likely.

A transient ridge builds in Tuesday afternoon, bringing some
clearing to eastern Utah and the lower elevations of western
Colorado. Light shower activity remains possible across the Colorado
mountains through the evening hours. In areas that do see sunshine,
temperatures are expected to rebound to around 5 degrees above
normal. Wednesday sees the next large low dropping into the Northern
Rockies, pushing a cold front nearly to the Wyoming/Colorado border.
Models do agree that this system will have better moisture to work
off of, but are in poor agreement over how far south the influence
of the cold front will reach. The northern mountains stand to see a
few more inches of snow with this front, and the lower elevations of
northwest Colorado could see some rain showers. Otherwise, the main
impact will be increased cloud cover and some cooler air filtering
south from Wyoming. South of the front, the tight pressure gradient
aloft and a 70-80 knot jet will bring strong, gusty winds to areas
along and south of the I-70 corridor. Temperatures through the end
of the week will run 5-10 degrees above normal along and south of I-
70 and near to a few degrees above normal for areas north of
I-70.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1115 AM MDT Sat Apr 13 2024

Mostly sunny skies and afternoon breezes can be expected until
sunset when downvalley winds will take over. VFR conditions can
be expected over the next 24 hours.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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