546
FXUS65 KGJT 192313
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
513 PM MDT Fri Jul 19 2024

.KEY MESSAGES...

- Temperatures are expected to remain a few degrees above normal
  with daily thunderstorm chances slowly decreasing through
  early next week.

- Threats from thunderstorms the remainder of today will be
  localized flooding...small hail and gusty outflow winds.
  Storms with more wind than rainfall will be the threats beyond
  this.

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

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 209 PM MDT Fri Jul 19 2024

Satellite/radar imagery started the day with plenty of gravity
waves/boundaries floating around...forcing weak elevated
convection and a clue of the added moisture to the sounding.
The initial round of storms had little to no lightning yet still
produced rainfall rates in excess of 1.2 inches per
hour...another clue that localized flooding will likely be the
primary threat today. That said storms in the South have been a
bit more robust where the cloud cover was limited this morning
so a few storms will also still be able to drop some hail even
with low to moderate shear in place. The southern mountains are
still favored for storm coverage and where flooding will be more
of a concern. This area has had several days of storms with
moderate to heavy rainfall rates and Highway 145 from
Placerville to Telluride will be especially monitored for
runoff problems. The model trend of pushing the SubTrop High
back to the West is on track and this will bring us into deeper
northerly flow and advect in a drier airmass for tomorrow.
Moisture lingers over the southern CWA but there should be a
noticeable downturn in coverage across the North. There is a
late arriving wave and speed max dropping out of Wyoming into NW
Colorado late in the day which could fire some high based storms
in the evening but lighting and wind will be more of concern
here than wind. This area of ascent should cross through the
central mountains through sunrise and keep a threat of isolated
showers in place or more likely an area of ACCAS. Nothing new to
report on temperatures as they continue to run above normal by
several degrees in most areas.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 209 PM MDT Fri Jul 19 2024

The ridge axis will extend north along the spine of the Rockies and
into southern Canada on Sunday, while troughing continues to
dominate the eastern CONUS. Theoretically this would bring a bit of
a down day to the Western Slope but, thanks to continued elevated
moisture and a weak embedded wave digging into the far southeast
portion of the forecast area, scattered showers and thunderstorms
will continue on Sunday. Far northeast Utah and northwest Colorado
look to stay largely dry but elsewhere, especially as you head
towards the mountains along the Divide, will be fair game. Drier air
finally begins to infiltrate more of the area on Monday as the ridge
is pushed farther east thanks to a trough of low pressure dropping
south from the Gulf of Alaska. Forecast PWATs are quite optimistic
at the moment, projecting values that are 60 to 80 percent of normal
by Monday afternoon. Regardless, this better push of dry air will
help the valleys clear out with isolated to scattered convection
remaining possible over the mountains, especially south of I-70. The
ridge continues to slowly push east and begins to weaken Tuesday and
Wednesday and even into Thursday as the upstream trough pushes into
western Canada. PWATs across our forecast area will perhaps continue
to drop slightly under this regime but, either way, daily showers
and storms will be possible over the higher terrain. But, as the
lower tier of the atmosphere dries out, gusty outflow winds will be
more likely than those moderate to heavy rain events.

Temperatures will be stagnant Sunday and Monday before highs begin
to warm from Tuesday onwards. By midweek highs are expected to be 4
to 8 degrees above normal area-wide with some of the lower valleys
potentially climbing into the low triple digits once again. Lows
each night through the period will be on the mild side for mid to
late July.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 509 PM MDT Fri Jul 19 2024

Scattered showers and storms continue this evening, dissipating
after sunset tonight. Gusty outflow winds and lightning are the
main threats. If an airfield gets a direct hit from one of the
showers MVFR conditions have at least a moderate (50%) chance of
occurrence. Otherwise VFR conditions will be in place. Another
round of isolated to scattered storms tomorrow afternoon,
especially in the southern mountains.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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