029
FXUS65 KGJT 050911
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
311 AM MDT Wed Jun 5 2024

.KEY MESSAGES...

- The warmup to well above normal temperatures begins today as
  high pressure builds overhead, providing mostly sunny skies
  and dry conditions with high temperatures rising to around 10
  degrees above normal.

- Some of the hottest temperatures are expected late week with
  highs running 10-15 degrees above normal and triple digits
  likely for the lower desert valleys.

- Chances of mountain showers and storms will return for the
  weekend into early next week.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 311 AM MDT Wed Jun 5 2024

The warmup to well above normal temperatures begins today and
lasts through this weekend, peaking on Friday with some of the
hottest temperatures we have seen so far this year on the
Western Slope. High pressure will continue to build over the
Great Basin with a dry northwest flow overhead. High
temperatures today will be about 5 degrees warmer than
yesterday, with highs settling around 10 degrees above normal.
Very little instability and moisture exists in this pattern with
mixing ratios down to about 1 to 2 g/kg and CAPE basically non-
existent, so like yesterday afternoon, do not expect any
convection to fire over the high terrain, resulting in a quiet
day. The winds will be breezy at times but lighter than previous
days, with gusts to 25 mph possible at times, but not
widespread by any means.

The ridge moves overhead by Thursday, with highs jumping up
another 5 degrees to end up 10 to 15 degrees above normal. Under
this heat dome, strong WAA looks to take place, especially later
in the week as the flow shifts to a more southwesterly
direction. For Thursday though, we stand a good chance to see
our first 100 degree day in the Grand Valley, or at least pretty
close with triple digit heat more likely in the desert valleys
of east-central and southeast Utah. The latest probabilities
show the Grand Valley at a 50-60% chance of exceeding 99 degrees
on Thursday with some lower desert valleys of east-central and
southeast Utah at greater than 90% chance. When you change this
value to greater than 98 degrees, that probability jumps up to
80% for the Grand Valley and near 100% for the lower desert
valleys of east-central and southeast Utah. So, needless to say,
confidence is high that highs will be near 100 degrees for these
areas, if not upper 90s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 311 AM MDT Wed Jun 5 2024

Thursday night sees the dome of high pressure firmly in place
over the Desert Southwest while an area of cutoff low pressure
lurks off the coast of southern Baja California. Despite the
expected clear skies and light winds, the heat associated with
this dome of high pressure will keep overnight lows 10-15
degrees above normal from Thursday night through the weekend.
Likewise, daytime highs will soar for Friday, with the current
forecast carrying upper 90s to low 100s for all of the desert
valleys of eastern Utah and western Colorado. Multiple ensemble
suites also are hitting on this unusual heat, with both the
ECENS and NAEFS situational awareness tables indicating record
high values against the 30-year climatology. In fact, for the
Grand Junction Regional Airport, the record for June 7th, this
Friday, is 100F. So we have a good shot of at least tying, if
not breaking, this record. With such unusual early season heat,
make sure to take precautions if spending time outside. Stay
well hydrated, wear light colored and loose fitting clothing,
and, if possible, stay somewhere cool during the hottest part of
the day, whether that be in an air conditioned building or just
in a shaded area out of the sun.

These hot temperatures will stay with us through the weekend as
the ridge of high pressure remains overhead, but a gradual
cooling trend will start up on Saturday. Increasing moisture
aloft as the clockwise flow around the high and counterclockwise
flow around the previously mentioned cutoff low pumps some
subtropical moisture northward will lead to increasing clouds
and chances for mountain showers beginning Saturday afternoon.
This will knock high temperatures down a few degrees compared to
Friday. Passing weak shortwaves to the north of eastern Utah
and western Colorado will add an occasional boost to storm
coverage through the weekend. With dry surface air in place, the
main threats with any showers or storms this weekend will be
gusty outflow winds and lightning. By Saturday night, a Pacific
trough approaches the West Coast and model agreement begins to
fall apart on a lot of details. Looking at the broadest take on
model guidance, the ridge axis should pass overhead on Sunday,
while a portion of energy associated with that Pacific trough
dives south and begins to cut off over the SoCal coast. Models
are indicating a pretty good fetch of moisture making it into
the Four Corners region during this period, so mountain showers
and storms will remain in the forecast into early next week. As
the California low continues drifting southwest, flow over
eastern Utah and western Colorado becomes westerly to
northwesterly, allowing some cooler air to build in. This,
combined with increasing cloud cover and storm coverage, will
allow high temperatures to drop to within 5 degrees of normal to
kick of the coming workweek.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1116 PM MDT Tue Jun 4 2024

Clear skies and light northerly winds will continue through the
night, with typical terrain driven patterns really kicking in
around 10z. Gusty westerly winds will start up after 18z
tomorrow afternoon, with gusts up to 25 knots possible. Skies
will remain clear and VFR conditions will prevail through the
period.

&&

.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. As a result, we`ll see creeks, streams and major
tributaries along the Upper Colorado River Basin rise. Seasonal
peak flows are expected over the next 10 days, with the Upper
Gunnison, Upper Yampa and Colorado Headwaters basins potentially
peaking this weekend. Current guidance oscillates diurnal peaks
cresting the Action Stage for portions of Gore Creek and Eagle
River in Eagle County and the Elk River in Routt County
Colorado. We will continue to monitor these evolving forecasts
to see if any Flood products are warranted. But for now, we
just want to pass on the message.

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...MDA
LONG TERM...BGB
AVIATION...TGJT
HYDROLOGY...ERW