640
FXUS65 KGJT 091146
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
546 AM MDT Thu May 9 2024

.KEY MESSAGES...

- Snowfall will favor the eastern Uinta mountains in northeast
  Utah and the higher elevations of the San Juans and central
  Colorado mountains today through Friday.

- Snow amounts in excess of 6 inches have a 50 to 60 percent
  probability of occurring over the highest peaks of the eastern
  Uintas...eastern San Juans and Elk mountain over the next 48
  hours...with lesser probability of at least 30 percent along the
  travel corridors.

- Unsettled conditions will persist through the weekend along
  with a slow warming trend...however temperatures will remain
  below normal.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 315 AM MDT Thu May 9 2024

Satellite indicates the low circulation is descending southward
somewhere over west-central to southwest Utah early this
morning. This low will eventually become closed and cut off from
the main flow somewhere around east-central Utah late this
morning into early afternoon and settle over southern Utah by
late this afternoon and evening. Two particular areas are
favored for snowfall in this pattern. The first is the eastern
Uinta mountains under northeast flow this morning through early
afternoon as the low circulation descends. The second is the
eastern San Juans and spine of the Sawatch Range in the central
Continental Divide, including Monarch Pass and Wolf Creek Pass
which are actually in PUB`s CWA. The eastern spine of our
Sawatch and San Juans picks up late this afternoon and continues
through Friday afternoon for the most part as the cut off low
spins over southern Utah and retrogrades a bit westward towards
Las Vegas. This will advect some moisture around the low, along
with daytime instability and orographics to generate snow at the
higher elevations. The probability that snowfall amounts over
this 48 hour period exceed 6 inches in these higher elevations
along the eastern fringe of our Sawatch Mountain zone and San
Juans is 50 to 60 percent...same with the higher elevations of
the eastern Uintas. The majority of these zones however as you
get further away from the eastern spine in the San Juans and
West Elks towards our main travel corridors has a 30 to 40
percent chance of exceeding 6 inches. The main travel corridors
on the western side of the divide remain limited in terms of
impacts as roads should remain wet with maybe 2 to 4 inches of
snow, possibly up to 5 at the highest elevations, for each 24
hour period both today and Friday. Snow accumulations appear
limited to areas mainly above 10,000 feet. The flow pattern
around this cut off low also is favoring the eastern upslope
areas of the eastern San Juans and central mountains, which is
more on the Front Range side than our western slope side.
Therefore, opted not to issue any Winter Weather Advisories with
this package as impacts appear limited to the higher elevations
along the eastern spine of our shared San Juan and Sawatch
Mountain zones. Winter just won`t let go for our mountain areas.

Elsewhere, expect scattered showers with light accumulations
favoring the mountains and some lower elevations seeing light
rain showers from time to time. Steep lapse rates and
instability will help drive the convective element and this time
of year, the QPF seems to be infiltrated with convective
feedback and bullseyes in random areas, so had to dial this back
a bit. Throughout this period over the next few days,
temperatures should be slowly moderating and trending upwards
despite the clouds and showers around. We will see about a 5
degree bump in high temperatures today compared to yesterday and
another 5 or so increase for Friday. Highs will still be below
normal but will be inching closer to normal by this weekend.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 315 AM MDT Thu May 9 2024

Showers will linger over San Juan Mountains and portions of the
Sawatch and adjacent valleys Friday night as the low continues to
spin over south-central Utah. 00Z/Thu operational models were in
good agreement carrying the low over the forecast area Saturday
through Sunday morning, moving the system as an open wave over the
southern Plains on Sunday. Decent dynamic forcing and steep lapse
rates below the 500 mb cold pool is expected to generate widespread
shower activity along with some embedded thunderstorms as the system
moves overhead Saturday. The mountains and south will be favored but
precipitation chances are good for a vast majority of the forecast
area. Expect showers to decrease Saturday night as the atmosphere
becomes less unstable and dynamic forcing decreases. Despite the low
being well east of the area on Sunday, lingering moisture will keep
showers in the picture, mainly over the mountains during the
afternoon. In fact, even as flow shifts to the northwest and modest
drying is indicated in the 700-500 mb layer for the first half of
the coming week, diurnally driven showers and thunderstorms can
still be expected each day, but coverage will be more scattered.
Temperatures will be warming throughout the long term, so mountain
snow will largely be confined to areas above 9000 feet with
accumulating snow expected to be fairly light and occurring mainly
above treeline. Temperatures are expected to be near normal by
Saturday then hover from 5 to 10 degrees above normal during the
remainder of the period.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 546 AM MDT Thu May 9 2024

Cloud cover and scattered showers will become more prevalent
across the area with high terrain most favored with MVFR
conditions and ILS breakpoints reached at times. Isolated
thunderstorms are possible as well. VFR will prevail otherwise
with breezy winds out of the east late this afternoon into the
evening.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MDA
LONG TERM...NL
AVIATION...TGJT