023
FXUS65 KGJT 270008
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
608 PM MDT Fri Jul 26 2024

.KEY MESSAGES...

- Scattered to numerous showers and storms continue into the
  evening.

- Storms will be capable of producing gusty winds, hail up to 1"
  in diameter, and heavy rainfall. Localized flash flooding is
  possible, particularly in the steep terrain and other
  vulnerable areas.

- Warm and dry conditions return Sunday and persist through
  much of next week.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 212 PM MDT Fri Jul 26 2024

We continue to anticipate scattered convection across much of the
forecast area this afternoon and evening as monsoonal moisture
interacts with pulses of shortwave energy advecting through the
southwesterly flow aloft. Dew point temperatures this morning were
in the 50s area wide, but it became apparent that most of the CAMs
were underdoing dew point temperatures. For example, the HRRR has
dew points upwards of 10 degrees too cool compared to ground
observations. The NAM Nest seems to be the most representative at
this time. With satellite imagery showing sufficient clearing after a
cloudy start to the day, convection this afternoon will likely
realize forecasted mixed-layer CAPE values of 500-1200 J/kg. Deep-
layer shear on the order of 15-25 knots could support a few isolated
severe storms, but organized severe convection is not likely with
limited shear in place. Gusty outflow winds up to 50 mph and hail up
to 1" in diameter are the primary threats. Localized heavy rainfall
is also on the table. CIN increases quickly after sunset but a few
showers and storms may continue into the evening.

A similar story again tomorrow afternoon and evening with the
biggest difference being increased shear with an upper-level jet
moving in overhead. The biggest forecast uncertainty is how quickly
monsoonal moisture will begin to erode. All of the hi-res models
show decreasing PWATs late tonight into tomorrow, but given that
they are struggling with the moisture currently available and that
the models are usually too quick to clear the monsoonal moisture
from the region, we cannot rule out scattered convection similar to
what we will see today. If the mositure does decrease, the coverage
of convection will also decrease. A drier atmosphere could also lead
to elevated fire weather conditions in parts of eastern Utah
tomorrow afternoon with surface winds gusting up to 25 mph, but
given our lower confidence in mositure clearing by tomorrow
afternoon we opted against fire weather headlines at this time.

&&

.LONG TERM /SATURDAY NIGHT THROUGH FRIDAY/...
Issued at 212 PM MDT Fri Jul 26 2024

On Sunday a trough tracks from the Great Basin to the Northern
Rockies bringing a midlevel dry punch into the region from the
southwest. Guidance remains aggressive in scouring out moisture from
west to east by Sunday morning, dropping PWATs down to near 50
percent of normal that afternoon. It is always a bit tricky to get
rid of residual moisture post-monsoonal surge, so can`t rule out a
few storms over the mountains Sunday afternoon. If conditions dry
out as anticipated, the potential for near critical fire weather
conditions will be possible. This will be due to the presence of a
60 to 70 kt jet overhead across much of eastern Utah and western
Colorado, resulting in surface gusts right around 25 mph. The
gradient relaxes on Monday which would lead to more localized near
critical fire weather conditions. Continued warm southwest flow
aloft will bring about a warming trend into the midweek point with
temperatures returning to several degrees above normal and even back
to the low triple digits for some of the lower valleys. Early next
week will also see the next trough of low pressure begin to dig into
the Pacific Northwest. Its progression east on Tuesday will usher
the Subtropical High closer towards the Southern Plains, allowing
for monsoon moisture to slowly trickle back into the Four Corners
region on Tuesday and Wednesday. That might be short lived as the
trough to the north suppresses the moisture back to the south.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 605 PM MDT Fri Jul 26 2024

Isolated to scattered storms will continue this evening with
gusty outflow winds, small hail and brief heavy rain possible,
reducing conditions to MVFR at times. Most activity should
lessen by sunset with some nocturnal convection possible across
the north overnight. Expect redevelopment of thunderstorms,
favoring the higher terrain, Saturday afternoon with potential
drift into lower elevations late in the day.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...KAA
LONG TERM...KJS
AVIATION...TGJT