510
FXUS65 KGJT 180818
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
218 AM MDT Sat May 18 2024

.KEY MESSAGES...

- Warm and breezy this weekend with temperatures remaining at
  least 5 to 10 degrees above normal.

- Isolated to scattered showers are storms are expected today
  and Sunday. The higher terrain along the Divide will be
  favored with gusty outflow winds and small hail being the
  primary concerns from storms.

- A larger system moves through early next week resulting in
  cooler and wetter conditions. Drier weather looks to return by
  midweek.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 218 AM MDT Sat May 18 2024

This morning`s synoptic pattern features a prominent trough of
low pressure extending south from the Yukon with several waves
of energy wrapping around this parent system. The first, which
was responsible for yesterday`s breezy conditions and light
showers up north, has lifted into the Northern Great Plains.
Upstream, the next trough is just shy of the Washington border,
while the Polar jet remains firmly settled over the remainder
of the northwest CONUS. Flow aloft across western Colorado and
eastern Utah will remain zonal as we start the day, gradually
shifting to the southwest by this evening. The reason for this
will be two-fold; it will not only be in response to the trough
dropping into the Pacific Northwest, but also the progression
of a separate shortwave inland across the Desert Southwest. We
will finally begin to see some better moisture advection during
this transition with PWATs beginning to increase from southwest
to northeast throughout the day. The Four Corners will see PWATs
that are 130 to 150 percent of normal by midday before this
spreads into the central zones (and even climbs to almost 180
percent of normal) this evening. The northern third of the
forecast area will rebound from their slightly below normal
PWATs early this morning to around 150 percent of normal
tonight. Ahead of the shortwave orographics will be the primary
lifting mechanism but, with daytime heating and the uptick in
available moisture, we can still expect to see scattered showers
and thunderstorms throughout the day. Even though the higher
terrain will be favored, weak lift provided by some embedded
ripples in the flow will allow for some drift into the adjacent
valleys, most notably in southwest and west-central Colorado.
Strong outflow winds will be possible with storms with gusts of
40 to 50 mph likely. Outside of convection today, we can expect
mostly to partly sunny skies with occasional breezy conditions
as 700mb winds remain in the 20 to 25 kt range.

The shortwave will begin to push through before stalling later
tonight, resulting in nocturnal showers north of I-70 with
continued partly to mostly cloudy skies elsewhere. Upper level
troughing becomes more pronounced across the entirety of the
western CONUS on Sunday, but the boundary will remain stalled up
north. As a result, look for another round of afternoon showers
and storms up north with generally dry weather elsewhere. The
entirety of the area will experience breezy conditions as the
gradient tightens overhead with gusts of 25 to 35 mph expected
throughout the day.

Temperatures will continue to be unseasonably warm both today
and tomorrow. We were close to hitting the 90 degree mark for
some of the lower desert valleys yesterday and, looking at the
potential to exceed 90 degrees this weekend, we should still be
able to hold off. The probability is less than 5 percent for the
southwest and west-central Colorado valleys with a 10 to 20
percent chance of exceeding 90 degrees in southeast and east-
central Utah. Some localized pockets of 30 to 50 percent are
there but, overall, nothing too impressive.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 218 AM MDT Sat May 18 2024

A deepening trough to our northwest will act upon residual moisture
and a stalled frontal boundary to keep showers going across portions
of northeast Utah and northwest Colorado Sunday night into Monday.
Elsewhere, mainly dry, but breezy weather will be the rule,
particularly during the afternoon hours on Monday. This is in
response to the tight pressure gradient and a 110kt 250mb jet draped
overhead in between the trough to our northwest and a ridge to our
southeast. Gusts up to 45 mph will be common. Monday night into
Tuesday, the trough to our northwest digs across the region with a
strong cold front and brings more widespread precipitation to the
CWA, especially in the higher terrain. The exceptions to that may be
across extreme southeast Utah and southwest Colorado where the
trough has less influence and it`s more likely to stay dry. Despite
the cooler air associated with the trough, snow levels are progged
to stay mostly above 10,000 feet. Even at and above those
elevations, snow accumulations are likely to be minor with minimal
to no impacts. The storm system exits to the east Tuesday night into
Wednesday, taking most of the precipitation with it. Showers may
linger the longest across the northern Colorado mountains given
unstable northwesterly orographics, but even these should dissipate
by early Wednesday afternoon. Any break in the action is not
expected to last long as another couple of shortwaves are forecast
to skirt across the north through the end of the long term period.
This should lead to more showers across northeast Utah, northwest
Colorado, and the high terrain along the Continental Divide Thursday
and Friday.

Temperatures through next week are expected to start off near to a
few degrees above normal on Monday before falling well below normal
for Tuesday and Wednesday. Temperatures moderate some for Thursday
and Friday, but are still expected to stay near to below normal for
this time of year.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1052 PM MDT Fri May 17 2024

VFR conditions will prevail for the next 24 hours. Quiet
weather persists into Saturday morning before scattered showers
and isolated thunderstorms begin to develop over the higher
terrain Saturday afternoon. TAF sites along the Divide, such as
KASE, KGUC, KEGE, and KTEX will likely have storms in the
vicinity with lower confidence elsewhere. Winds will become
breezy again with gusts up to 35 mph possible. Clouds with some
nocturnal showers are expected for Saturday night with winds
weakening overnight.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MMS
LONG TERM...MDM
AVIATION...TGJT