835
FXUS65 KGJT 102129
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
329 PM MDT Fri May 10 2024

.KEY MESSAGES...

- Scattered to numerous showers and some thunderstorms continue
  into the early evening hours with a brief downturn in coverage
  tonight.

- Widespread showers and scattered storms develop by early
  Saturday morning as a system lifts over the Four Corners. Snow
  levels will generally be above 9500 ft though storms could
  drive levels down to the higher valleys. Little travel
  impacts are expected during the day.

- Unsettled conditions will persist through the weekend along
  with a slow warming trend...however temperatures will remain
  below normal. Above normal temperatures return next week.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 329 PM MDT Fri May 10 2024

A quick glance at the radar this afternoon would make you
believe it was summertime as scattered to numerous showers and
some storms persist across the Western Slope. The stubborn area
of low pressure retrograded back towards southern Nevada early
this morning and has since stalled over the southern Utah /
northern Arizona border this afternoon. This has allowed ample
moisture to wrap around the low into the Four Corners region
with this morning`s 12Z sounding recording a PWAT of 0.43
inches, or one that is just slightly above the norm for almost
mid May. As moisture continues to advect into the region in the
south / southwest flow PWAT will increase to 130 to 150 percent
of normal by early evening before the better moisture begins to
shift east over the San Juan Mountains. This will be due to the
gradual lifting of the low to the northeast on Saturday. During
this transition the more widespread showers will taper off in
coverage tonight, though activity will persist across the San
Juans and adjacent foothills into Saturday morning.

For Saturday itself the vort max associated with the low will
swing through and, with moisture once again trending to above
normal levels, ample forcing and diurnal support will fuel
another round of widespread showers and storms. Under a well
saturated profile periods of moderate precipitation and even
some small hail can be expected. And, though snow levels will on
average be above 9500ft, these convective showers could drive
those snow levels down. Snow totals remain relatively unchanged
with an additional 2 to 4 inches of snow likely in the southern
and central Colorado mountains, though locally higher amounts of
6 or so inches will be possible. Either way, travel impacts will
be limited with this late spring system and roads will remain
wet for most areas. Elsewhere much of the region stands a good
chance to see a soaking shower or storm sometime on Saturday, or
at least plenty of clouds to keep temperatures unseasonably
cool. Subsidence settles in for Saturday night in the wake of
the departing low which will lead to a decrease in shower and
thunderstorm activity. Showers will be slow to end along the
Divide but elsewhere partly cloudy skies will close out the
short term.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 329 PM MDT Fri May 10 2024

The current weather pattern and the one developing through next
week has been one of the most maddening exercises in
prognostication for a while. It really will be a roll of the
dice looking at most probable ensemble cluster solutions for a
first guess. The northern stream will be the main player...or so
it appears now...but there will be a SoCal upper low being
absorbed into the flow that may have to be dealt with. All said
the models are in somewhat fair agreement Sunday into Tuesday as
the next upstream high latitude wave drops into the PacNW and
helps kick this upper low off into the central CONUS. There will
be brief transitory ridging moving through on Monday between
these systems but residual moisture and instability will keep a
threat of mountain showers in place. Tuesday the trough swings
across the region and we can again expect an increase in shower
activity across all but the far Southwest portion of the CWA.
Ensemble cluster-wise the monopole signature appears over the
PacNW and only strengthens through Thursday as models struggle
to agree on either a strong EPac ridge moving onshore or the
arctic folding southward into the same region. The former
pattern is reflected as more probable in the clusters through
Thursday before flattening as a compromise by late week. For now
higher confidence in showers being limited to the higher
terrain Sunday into Monday with warming temperatures. Showers
expand across the CWA Tuesday into Wednesday with the trough
passage and temperatures drop back slightly as a result. No
comment beyond this.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1126 AM MDT Fri May 10 2024

Convective showers of rain and snow will impact the region
through the afternoon with the chance of lightning in some
storms. ILS/VFR conditions appear to hold at most locations with
temporary MVFR or lower possible as showers move over the
airfield. Confidence is low due to the spotty coverage of the
precipitation today. Better moisture is located closer to the
divide so KGUC will be more likely to linger under MVFR
conditions through the day. Overall conditions look to improve
overnight as the convection tapers off and then redevelops
through the day on Saturday.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MMS
LONG TERM...15
AVIATION...TGJT