Area Forecast Discussion
Issued by NWS Grand Junction, CO

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000
FXUS65 KGJT 140510
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1110 PM MDT Wed Mar 13 2024

.KEY MESSAGES...

- Winter Weather Advisories remain in effect through tonight and
  early Thursday morning. Additional snow will mainly be light,
  but can lead to slick roads in spots.

- A Winter Storm Warning begins this evening for the eastern
  Uintas, where significant snow is expected through Thursday.
  Blowing snow will make travel difficult around the Flaming
  Gorge area and along US 191 and state highway 44.

- Precipitation will shift to southern regions later Thursday
  and Friday as a closed low brings more substantial moisture in
  from the south. Winter Storm Warnings/Advisories continue for
  the Uncompahgre, San Juan Mountains and the La Sal/Abajo
  Mountains.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 303 PM MDT Wed Mar 13 2024

GOES-16 satellite imagery shows a well defined shortwave trough
moving across eastern Utah and western Colorado this afternoon.
This wave is helping to push a cold front southward across most
of the CWA. Together, these features combined with a good deal
of moisture are producing fairly widespread shower activity at
this hour. There`s definitely a more convective flavor to these
showers given cold and agitated cloud tops and even a lightning
strike here and there. For the most part, precipitation is
falling primarily as snow, though the lowest valleys have
generally either been rain, a rain/snow mix, or a brief period
of all snow under more intense showers. This activity will
generally continue through this evening before drier air works
in from west to east and diminishes showers for all except the
Continental Divide mountains. Winter Weather Advisories remain
in place for this package, though it`s possible some may be able
to be brought down early depending on impacts and how quickly
things dry out. Overall, it`s been a pretty cold and raw day
today with temperatures much colder than normal and much colder
than they have been recently.

After today`s waves exit east, a large and deepening closed low
pressure system will take hold of the prevailing weather for
our CWA and won`t relinquish it until possibly sometime next
week. The low will dig southward through the Great Basin
overnight and be somewhere near the triple point of California,
Nevada, and Arizona by 12Z Thursday. As this occurs, wrap around
moisture will surge in from the north and east through the
night and into the day on Thursday, allowing showers to
redevelop across northwest Colorado and northeast Utah. The
snowfall trends for the eastern Uinta mountains continue to go
up, and combined with a strengthening pressure gradient, the
winds are cranking up too. Definitely a good call by the
midnight shift to upgrade UTZ023 to a Winter Storm Warning. Wind
gusts up to 60 mph will make travel especially difficult with
snow and blowing snow leading to near whiteout conditions at
times. The strong pressure gradient will also to lead to strong
and gusty winds across the eastern Uinta Basin and far northwest
Colorado for much of Thursday and Thursday night with gusts up
to 55 mph... possibly even approaching 60 mph which would be
flirting with High Wind Warning criteria. In coordination with
WFO SLC, decided to issue a Wind Advisory for those areas to
cover this fairly localized wind threat.

The band of showers that starts up north Thursday morning will
gradually shift southward through the day with the focus
shifting towards the southeast Utah and southwest Colorado
mountains by late Thursday afternoon and evening. As the showers
shift south, places up north will start drying out as drier air
works in. Thursday will be more or less a day of transition as
this occurs, which means a rather cool and unsettled day with
variable periods of wet and dry. The closed low will settle and
meander around the triple point Thursday night, setting up a tap
of enhanced moisture from the south. This moisture will be
pointed directly at our southern mountains. With favorable
orographic and large scale ascent, precipitation will become
widespread across the south and become more and more intense
through the night. Heavy snow will favor the mountains above
6000 feet and will fall at rates up to 2 inches per hour at
times. This will make for significant winter weather driving
conditions across Highway 550, especially over the high passes.
The Winter Storm Warning goes into effect at 18Z Thursday, but
the highest impacts will be after dark and continue through
Friday morning. For more on how this system evolves through the
end of the week and weekend, see the long term discussion below.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 303 PM MDT Wed Mar 13 2024

The cutoff low that settles in over the Mohave Desert area
tends to set up camp through the extended period with the models
in general good agreement. This will allow the low pressure
system to pull deep moisture with Pwats over two standard
deviations above normal up off the eastern Pacific and Gulf of
California into southwestern Colorado and southeastern Utah to
feed extended showers across the San Juan mountains and the Four
Corners area Friday and Saturday. Some snow showers will even
push into the central Colorado mountains Saturday afternoon with
moisture overrunning the San Juans and the Divide. The Winter
Storm Warning for the San Juan, Abajo ans La Sal Mountains
mentioned above will continue through Friday night with more
than 12 inches snow expected at the higher elevations above
about 7500 feet. Stay tuned on this as this system is very
dynamic and may have significant impacts for the southern
mountains.

The models agree on a shortwave system orbiting the low causing
it to wobble east into Arizona Saturday night into Sunday
before retreating west again to the Mohave. The GFS has the most
extreme eastward excursion as far as the Arizona - New Mexico
border Sunday night before retreating. The GEFS ensemble also
shows more dispersion among its members by Sunday on the
position of the low while the European ensemble has a pretty
tight cluster through Monday. The Canadian ensemble stays in
good agreement with the European to early Monday before its
solutions disperse. With cutoff lows it`s hard to say what
they`ll do or how long they`ll stick around, but for now it
looks to stay into early next week. Tend to lean towards the
European ensemble on this one with the tighter grouping keeping
the system more to the west. As it wobbles east, it will tend to
push the moist plume to the east of the Divide allowing the
southern mountains a pause in the showers Sunday, but with the
westward retreat, expect showers to return Sunday evening into
early next week across the southern mountains. Current guidance
doesn`t indicate winter weather headlines for early next week,
but that is yet a long ways out and there is potential for
another good storm for the southern mountains. Confidence is low
either way this one wants to go, but we should have a better
idea by Friday afternoon, so stay tuned again.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1102 PM MDT Wed Mar 13 2024

The next phase of this system will begin this morning as flow
comes out of the east. Several rounds of showers are possible
during the taf period. ALso, gusty winds are expected at some of
the sites. The easterly flow will disrupt the typical diurnal
wind directions. Low-level wind shear is possible. Showers along
with the wind will worsen flying conditions at times at just
about all sites.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Wind Advisory from 9 AM Thursday to midnight MDT Thursday
     night for COZ001.
     Winter Weather Advisory until midnight MDT tonight for COZ004-
     013-017>019.
     Winter Weather Advisory until 6 AM MDT Thursday for COZ009-010-
     012.
     Winter Weather Advisory from noon Thursday to 6 AM MDT
     Saturday for COZ017-018.
     Winter Storm Warning from noon Thursday to 6 AM MDT Saturday
     for COZ019.
UT...Wind Advisory from 9 AM Thursday to midnight MDT Thursday
     night for UTZ024.
     Winter Weather Advisory until midnight MDT tonight for UTZ028.
     Winter Storm Warning from noon Thursday to 6 AM MDT Saturday
     for UTZ028.
     Winter Storm Warning until 6 PM MDT Thursday for UTZ023.

&&

$$

SHORT TERM...MDM
LONG TERM...DB
AVIATION...TGJT


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