222
FXUS65 KGJT 062040
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
240 PM MDT Thu Jun 6 2024

.KEY MESSAGES...

- Hot and dry into weekend, with desert valleys approaching
  100.

- Mountain showers and thunderstorms develop Friday afternoon. A
  few storms will produce strong outflow gusts.

- Low valleys remain warm and dry, while afternoon mountain
  showers and thunderstorms remain a threat into the early half
  of next week.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 229 PM MDT Thu Jun 6 2024

Warm and dry conditions continue on the West Slope this afternoon.
Relative humidities in the teens under a broad ridge of high
pressure are keeping skies mostly clear, aside from a cloud or two
forming on terrain features, where melting snow continues to produce
some localized moisture. A couple of weak shortwaves push across the
Great Basin this evening and overnight. This will cut into the
ridge`s amplitude and begin to whittle away its stranglehold on the
region.(more to follow on this) Likewise, southward over Baja
Mexico, a cutoff low will do its best to send some weak moisture up
across the Four Corners on Friday. Some model guidance had
temperatures surging north of 100 Friday afternoon. Some cloud cover
and less subsidence from the flattening ridge looks like the early
forecasts were a touch aggressive. Followed this morning`s shift and
backed off of the highs a touch. Still looks like much of the lower
deserts of southeast Utah will come pretty close to triple digits
tomorrow, while across the state line we`ll stick around the upper
90`s tomorrow in our low valleys. Up the hill, high temperatures
will depend on the depth of cloud cover and any shower activity we
see Friday afternoon. Temperatures will still hover around 10
degrees over early June climatology. Shower development Friday
afternoon will favor terrain features, then shift more widespread
across the northern half of the CWA thanks to another weak shot of
moisture pushing through on a series of shortwaves. Some scattered
convection is expected, with storms capable of dropping some strong
wind gusts into the dry boundary layer at the surface. A few showers
will likely continue into the overnight hours Friday night, but
meager moisture supplies probably will keep things mostly cloud
cover and a few showers on the terrain of northwest Colorado.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 323 AM MDT Thu Jun 6 2024

The relocation of the SubTrop High from the Desert SW to the
Southern Plains will be complete by early Saturday. Easterly flow
around the southern periphery of this High will begin to transport
Gulf of Mexico moisture back toward our southern CWA...which gets
enhanced later in the day as a cold front dives along the lee of the
Rockies into New Mexico and the upslope flow drives it through the
gaps. Finally...a low pressure system will be drawn northward out of
the Baja region on Sunday into Monday tapping into another moisture
source with a Pacific origin. The bigger picture of this is PWAT is
pushed up to near and above 3/4 of an inch for the weekend into
early next week...which for early June is in the region of the 90th
percentile. The moisture will help fire daily afternoon
thunderstorms while also easing the temperatures back a bit each day
back to just a single digits above normal instead of 10 to 15
degrees. With the higher then normal moisture in the profile there
will be a threat of some of the organized storms producing moderate
to maybe even heavy rainfall rates. However sounding profiles in the
lower to mid elevations suggest gusty outflow winds will likely be
more of a threat than wetting rainfall. Sunday afternoon looks to be
the peak of the convective activity as the Baja low rotates south of
the 4 Corners. As we get later into the week the SubTrop High looks
to try and re-establish itself over the Desert SW with greater
uncertainty on where the next cutoff low in the SoCal/Baja region
will reside. Moisture will begin to wane by Tuesday with afternoon
storms mainly becoming focused on the higher terrain. The decrease
in moisture and storms will allow the temperature trend to increase
with highs once again approaching the triple digits in the lower
desert valleys by midweek.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1130 AM MDT Thu Jun 6 2024

High pressure will remain in place with VFR conditions expected
through the period. A few clouds will begin to invade late in
this period. This will be mostly mid and upper level clouds with
no precipitation expected during the period. Winds will remain
light and terrain driven, with a few gusts this afternoon around
terrain.

&&

.HYDROLOGY...
Issued at 229 PM MDT Tue Jun 4 2024

High pressure building overhead through the end of the week
will result in an unseasonably warm period across the Western
Slope. Simultaneously, as those temperatures rise, so will the
rate of snowmelt across our high terrain. Even though low to mid
elevations have already melted out, there`s still an abnormally
high amount of snow left over basins generally at and above
11,000 ft...and it`s melting...fast. As a result, creeks,
streams and major tributaries along the Upper Colorado River
Basin are on the rise. Seasonal peak flows are expected over
the next 10 days, with the Upper Gunnison, Upper Yampa and
Colorado Headwaters basins likely peaking for the season this
weekend.

Current guidance oscillates diurnal peaks cresting the
Action Stage for portions of Gore Creek and Eagle River in Eagle
County. No highlights needed, yet, for that area after
discussion with local officials but we will keep an eye on
things over the coming days.

The Elk River near Milner in Routt County, on the other hand,
is expected to exceed Minor Flood Stage each morning through
Sunday. This increase in forecast stage/flow warranted an
upgrade from Flood Advisory to a Flood Warning. Also, the East
River near Almont is forecast to exceed Action Stage each
morning through Sunday, with the potential for exceeding Flood
Stage by Saturday. For now, a Flood Advisory is in effect for
this stretch of river. However, stay tuned for the potential
upgrade to a warning and/or extending the advisory downstream
into the Gunnison at Gunnison.

As scorching temperatures lure folks to the water, please
remember the potential hazards associated with high flows during
the snowmelt season. Fast flows are not just dangerous for
those choosing to float the rivers. In addition, high diurnal
swings may drastically change the depth and flow for normally
small creeks and streams. Swift currents and cold water
temperatures can catch you off guard, so please be vigilant with
current conditions and look for forecast updates when
recreating or working near the water`s edge.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...BGB
LONG TERM...15
AVIATION...TGJT
HYDROLOGY...ERW