109
FXUS65 KGJT 011000
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
400 AM MDT Sat Jun 1 2024

.KEY MESSAGES...

- Isolated to scattered thunderstorm development remains a
  threat each afternoon through early next week with gusty
  outflow winds more likely than wetting rainfall.

- Temperatures remain above normal this weekend into early next
  week...an expanding ridge aloft next week suggests
  temperatures are likely to climb even higher by midweek.

- The warmer temperatures means runoff will be well underway
  with most major stem rivers showing rises over the next
  several days.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 400 AM MDT Sat Jun 1 2024

Even though transitory ridging works in from the west today, the
flow will stay primarily zonal with several embedded shortwaves
moving through the flow this weekend. One such weak shortwave
tracks across this afternoon with a more robust shortwave this
evening, which should work on available moisture and instability
to generate isolated to scattered showers and thunderstorms.
Most activity will initially favor the high terrain but with
the more robust shortwave this evening, activity could spread
into the northwest Colorado valleys. Areas north of I-70 still
hold the best instability with CAPE north of 500 J/kg, while
areas south of I-70 are less than 200 J/kg. Storm coverage could
be a bit better today than previously indicated based on these
reasons as well as latest hi-res guidance which shows a bit more
coverage, especially up north. Although moisture is elevated
with mixing ratios upwards of 4 g/kg today, the low levels still
remain dry with inverted V sounding profiles, so expect gusty
outflow winds to be more of a threat than wetting rain. Not
expecting much in the way of rainfall but winds could gust 40 to
50 mph with any storm outflows, especially across the north.
Overall, mostly dry conditions and above normal temperatures
are expected today despite any showers/storms which should be
more high based and virga producing, again isolated to scattered
in coverage. Some storms could linger past sunset given forcing
from the shortwaves, with any remnant isolated activity likely
clearing out or dissipating by midnight.

Following on the heels of today`s activity is another shortwave,
again clipping the northern areas Sunday afternoon. Coverage
looks to favor the high terrain for areas mainly north of I-70
with this shortwave with limited precipitation and more gusty
outflow winds from any convection. Temperatures are expected to
be warmer today than yesterday and similar on Sunday with highs
4 to 8 degrees above normal.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 400 AM MDT Sat Jun 1 2024

Flow aloft turns northwesterly Sunday night as the shortwave
slides over the Front Range and out onto the Plains. Another low
pressure system drops south out of the Gulf of Alaska off the
BC Coast Sunday and turns east to track along the Canadian
Border Sunday night into Monday. With the approach of this
trough, look for gusty west winds Monday generally along and
north of I-70. Though this system stays well to the north, the
southern edge of the trough will brush the northern areas of
eastern Utah and Western Colorado Monday night into Tuesday.
Models are indicating that this trough will drag a significant
patch of moisture currently south of the Aleutian Islands over
the North Pacific into the Pacific Northwest and down into the
region with IVT`s of 300 to 400 kg/m/s along and north of the
I-70 corridor, and IVT`s approaching 200 kg/m/s pushing south
into the Four Corners area. Pwats climb above 200% across the
region with this surge. Guidance still isn`t picking up on this
limiting PoPs to 20% over the Uinta and Park Mountains and less
than 10% elsewhere. With the left exit region of the jet passing
over the northern areas Monday night, expect nocturnal
thunderstorms possible generally north of the I-70 corridor. The
trough also tightens the pressure gradient with linear shear
values around 30 kts, and a cool front pushes south into the
region to about I-70, so wouldn`t be surprised to see an
isolated stronger storm possible. This is definitely something
to keep an eye on over the next day or two to see if the models
pick up on this.

As the trough and associated jet moves east, the right exit
region moves in over the northern areas and ridging builds in
from the southwest putting eastern Utah and Western Colorado
under subsidence, clearing out the skies somewhat Tuesday
allowing diurnal heating to spawn isolated orographic showers
and isolated thunderstorms over the region through the
afternoon. The high pressure continues to build in over
Intermountain West Wednesday and even though the subsidence will
tend to cap convection, expect diurnal heating to spark
isolated light showers over the higher terrain with a possible
isolated clap of thunder. Models are in concurrence with a
Pacific low moving in off the Baja Coast Wednesday and the high
pressure sliding southeast over New Mexico, Texas and northern
Mexico Thursday which opens the door to a subtropical flow under
the high and up into the region Thursday into next weekend.
Look for afternoon and evening showers and thunderstorms
becoming widely scattered across the region through the latter
half of the week.

Temperatures start the week at six to eight degrees above normal
Monday with a slight dip Tuesday as the trough passes.
Wednesday onward will see temperatures climb to 10 to 15 degrees
above normal with high sitting over the region. Look for the
lower desert valleys to possibly hit the century mark late in
the week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1130 PM MDT Fri May 31 2024

Expect VFR conditions with light terrain driven winds through
about 18Z. Then look for isolated light showers to develop over
the higher terrain through the afternoon that may produce gusty
outflow winds up to 45 kts and occasional lightning. Convective
activity will end by about 03Z with light terrain driven winds
setting up across the region tomorrow night. Brief periods below
ILS breakpoints are possible at KASE, KEGE and KRIL between 18Z
and 01Z with passing showers.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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