498
FXUS65 KGJT 252048
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
248 PM MDT Sat May 25 2024

.KEY MESSAGES...

- Showers and thunderstorms continue this afternoon and evening
  before dissipating overnight. Gusty winds and some hail is
  possible with these showers and storms.

- Mountain snow is possible generally above 9 kft with minor
  impacts to the roads occurring tonight. Highest chances for
  upwards of several inches of snow will be in the northern and
  central mountains.

- Temperatures running below normal through the weekend will
  warm to five to ten degrees above normal by mid week.
  Precipitation chances remain low through mid week.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 236 PM MDT Sat May 25 2024

Models seem to be tracking well with satellite imagery trough axis
moving through central Utah and will push into eastern Utah late
this afternoon. H700 GFS has indicated three thermal boundaries, two
ahead of the trough (not really frontal boundaries) and the primary
cold front aligned more with the trough. Each of these boundaries
has showers and thunderstorms associated with it. The first of these
passed across the northern areas along and north of the I-70
corridor late this morning and is now just pushing east of the
Divide. It was mostly showers, but did produce a few thunderstorms
and a strong outflow gust over 60 mph. These storms are not expected
to be especially strong as there is little upper level support with
the left entrance region of the jet aloft, but the cool air through
the mid levels and max diurnal heating this afternoon is producing
surface CAPE values well over 300 J/kg and MLCAPE around 160 J/kg
through the afternoon and early evening.

The next wave of convection is now moving through eastern Utah and
will push through Western Colorado between now and about 7 PM before
moving east of the Divide. Close on the heals of the second wave is
the frontal boundary that will produce the stronger storms late this
afternoon and this evening with showers and thunderstorms extending
south to the northern face of the San Juan Mountains as it moves
east to west through the region. With the dry airmass in the lower
levels, expect strong outflow winds exceeding 55 mph. Also dime
sized to penny size hail and frequent lightning is likely with these
storms and can`t rule out an isolated stronger storm with one inch
hail stones possible. If you will be out through this evening, stay
tuned for weather alerts and, if thunder roars, go indoors.

The front will push east of the Divide around midnight with
lingering showers over the northern and central Colorado mountains
overnight into Sunday morning, ending around noon. Sunny skies under
the subsidence as a ridge starts building in from the west Sunday
will feel warm, but temperatures will stay about five degrees below
normal across the region under the northwesterly flow.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 236 PM MDT Sat May 25 2024

A ridge of high pressure will move in from the west and build across
the Northern Rockies with dry conditions to start the week. A low
pressure trough will move onto the Pacific Northwest coast, causing
the flow to shift to southwesterly over the region by Tuesday. A
shortwave looks to eject out ahead of this low and result in some
isolated to scattered showers and storms mainly over the higher
terrain along the Continental Divide. The better moisture and
instability resides east of the Divide though over the Front Range
and Plains. As this PacNW trough tracks east across the US-Canada
border, several embedded shortwaves will move through the flow,
resulting in daily isolated storms over the Divide during the
afternoon as enough instability remains present with daytime heating
for this to occur each afternoon. Drier conditions will still remain
on the western slope as the better moisture resides over the Front
Range and Plains. The flow shifts to more westerly on Friday due to
the passage of this trough across the north which looks to drag a
cold front through the area, affecting the north and possibly
central areas. PWAT anomalies come up quite a bit on Friday, so
better chances exist for showers and thunderstorms. The
deterministic models seem to be latching onto this potential while
the NBM has yet to catch on, leaning more towards a drier solution
with continued isolated convection over the higher terrain along the
Divide. To what extent this trough affects us on Friday remains to
be seen though as confidence is low this far out.

This drier southwest flow will allow temperatures to warm up to
above normal levels through the week by about 5 to 10 degrees above
normal. Most lower valleys look to rise into the 80s with near 90 in
the Grand Valley and low to mid 90s possible in the lower desert
valleys of east-central and southeast Utah. Northern higher valleys
look to rise into the upper 70s to low 80s in this pattern.
Temperatures look to cool off some Friday, closer to normal, as a
result of the potential increase in moisture and cold front boundary
moving through.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1156 AM MDT Sat May 25 2024

Expect scattered showers this afternoon into the early evening
with coverage expanding into lower valleys later in the day.
VCTS is possible at most terminals with brief MVFR conditions.
Winds will increase aloft leading to areas of LLWS and mountain
wave turbulence. Winds will remain breezy this afternoon with
gusts in the 30 to 40 mph range, potential above 40 mph near or in
any shower/storm activity. Showers should dissipate late this
evening, with clearing skies overnight into Sunday morning.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...DB
LONG TERM...MDA
AVIATION...MDA