665
FXUS65 KGJT 160943
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
343 AM MDT Tue Jul 16 2024

.KEY MESSAGES...

- Temperatures are expected to remain a few degrees above normal
  with daily thunderstorm chances through the remainder of the
  week and into the weekend as moisture is recycled under the
  area of high pressure over the region.

- Threats from thunderstorms will mainly be from gusty outflow
  winds though a few storms will be capable of producing smaller
  hail and moderate to heavy rainfall rates. Overall flooding
  threats remain low.

- The combination of high based storms...gusty outflow winds and
  lightning will keep also keep a threat of new wildfire starts
  in the picture.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 341 AM MDT Tue Jul 16 2024

The high pressure to the south that is dominating the weather
pattern over eastern Utah and Western Colorado has shifted farther
southeast over northern New Mexico over the last 12 hours. Models
are in good agreement with the high retrograding to the west to the
Arizona-New Mexico Border over the next 24 hours as a trough
descends down over the Northern Plains. This will shift the
monsoonal flow more to the south with most shower and thunderstorm
activity along and south of the I-70 corridor while the northern
areas will see more isolated convection than they had Monday with
drier air starting to move in from the northeast. Pwats continue at
about 0.80 inches across the region today, high enough to produce
some localized heavy rain rates with some of the stronger
thunderstorms, but again, the treats of flooding remains low. Expect
the convection today to be triggered off orographics with little
upper level support over the southern areas. There is some weak
upper-level divergence across the northern areas that could trigger
some surprise storms today over the northern areas, but guidance and
the high resolution CAMS are playing it down with the dryer push of
air. This is something to watch, so stay tuned to the forecast
through the late morning. Look for the convection to initiate
around noon over the higher terrain, increasing through the
afternoon with max heating and tapering off going into the evening
hours. Lingering showers and thunderstorms will continue over the
higher terrain through the late evening, likely ending along the
Divide sometime after midnight.

Pwats Wednesday look to decrease a bit to about 0.60 inches across
the region as the drier air continues to push in over eastern Utah
and Western Colorado. This will push the convective activity more to
the east along the divide through the early afternoon. As the high
pressure along the Arizona-New Mexico Border moves to the north to
the Four Corners area through Wedensday afternoon, the scattered
showers and thunderstorms will shift south over the San Juan
Mountains with isolated activity extending west to the Abajos and La
Sals.

Temperatures today will remain near normal to a little above normal
under the ridge as the clouds will limit the diurnal heating with
little change tomorrow. Though temperatures are near normal, mid
July is the hottest time of the year for eastern Utah and Western
Colorado with highs running around the century mark through the
lower valleys. If you plan to be out in the hotter time of day, it`s
best to avoid strenuous activities and keep plenty of water on hand.
Be aware that heat exhaustion can sneak up on you quickly.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 341 AM MDT Tue Jul 16 2024

According to strong model consensus, high pressure shifts slowly
westward from the border of southwest Colorado to southeast Utah
Thursday and Friday. Concurrently, a slug of moisture from the
Mexican Plateau moves across Arizona and is carried northeastward
across the area on Thursday. This will bring an uptick in
shower/thunderstorm coverage Thursday afternoon/evening. The slow
influx of moisture continues Friday with precipitable water levels
rising to 120 to 150% of normal, or from 0.8 to 1" of moisture in
the column. Consequently, coverage of moist convection increases
further with increased chances of localized heavy rain. Though ECMWF
and GFS ensembles disagreed on values, a drying trend begins this
weekend as the high retrogrades to Great Basin. Flow from the north
will bring drying and the region will experience a decrease of
precipitable water with levels falling to 0.5 to 0.75" later this
weekend and early next week. However, since drying occurs at mid-
levels low level moisture will still be sufficient to generate
scattered showers and thunderstorms each day from Saturday to
Monday, especially across the south. However, with less moisture in
the column the threat of excessive rainfall declines. Temperatures
are expected to show little change, hovering near or a few degrees
above normal throughout the long term period.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1135 PM MDT Mon Jul 15 2024

Late evening showers and a few thunderstorms continued over
portions of eastern Utah and western Colorado. This activity
could bring light showers to KRIL, KEGE and KASE through 08Z.
Even should this occur, VFR conditions should persist and
ceilings below ILS breakpoints are unlikely. Elsewhere, and
outside of the next couple of hours, VFR conditions are expected
at all TAF sites through the next 24 hours. Expect showers and
thunderstorms to redevelop on Tuesday from late morning through
early afternoon with this activity carrying on through evening.
Higher moisture levels bring better chances for showers to
impact TAF sites Tuesday afternoon/evening. Under high pressure
winds will continue to be relatively light and terrain driven,
but unpredictable outflow winds to 45 mph are possible at all
TAF sites during the period.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...DB
LONG TERM...NL
AVIATION...NL