473
FXUS65 KGJT 132057
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
257 PM MDT Mon May 13 2024

.KEY MESSAGES...

- Weak ridging will keep today`s showers and thunderstorms
  focused over the higher terrain. Activity will diminish after
  sunset.

- An approaching disturbance will bring a line of showers to the
  north late tonight with more widespread shower and storm
  activity Tuesday and Wednesday. Gusty outflow winds will be
  the main threat with storms.

- Temperatures will continue to warm through the week.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 257 PM MDT Mon May 13 2024

A bit of a downturn in shower and thunderstorm activity today as
expected, thanks to a brief transitory ridge of high pressure
settling overhead. Any convection has remained anchored to the
higher terrain before largely diminishing after a couple of
scans. Gusty outflow winds have not exceeded 35 mph at the
moment so, as we head into the early evening hours, any
remaining showers and storms will drop off with the loss of
daytime heating. This break will be short-lived as a shortwave
trough digging into the Northern Rockies sags south tonight,
brushing northeast Utah and northwest Colorado as a result. CAM
guidance is picking up on isolated showers across these areas
as early as midnight before a more notable band accompanying a
cold front drags through during the 2-6 AM timeframe. This line
will exit the region around sunrise as the first shortwave`s
axis slides east of the Divide. This will be just in time for
the next secondary trough to drop south from the Intermountain
West, engulfing the Western Slope by Tuesday afternoon. Moisture
increases in earnest with this second system as PWATs climb to
150 to 200 percent of normal. Daytime heating will act on this
abundance of moisture and support to fuel widespread showers and
thunderstorms throughout the day. Even with anomalously high
moisture content, initial QPF forecasts are conservative since
it will take a while for the profile to saturate. As a result,
gusty outflow winds will be the primary threat from convection,
though small hail and brief periods of moderate precipitation
cannot be ruled out. Tuesday night will see the trough`s base
shift east, allowing most shower activity to end overnight.
Plenty of clouds will persist into Wednesday morning because
we`re not out of the woods with the wave train just yet.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 257 PM MDT Mon May 13 2024

Another lobe of low pressure digs into the forecast area Wednesday,
which will support one more round of widespread, afternoon showers
and storms. Like clockwork, cumulus clouds are expected to build
across higher terrain by mid-day. Though, the trough`s axis may be a
better area of focus late in the day as the wave digs into northeast
Utah. In addition, nocturnal showers and storms may thrive through
the night along this boundary, likely favoring the Divide and the
southeast half of the CWA.

The closed low spinning over the SoCal coast will eventually become
absorbed into the belly of Wednesday`s trough and sweep across the
Desert Southwest on Thursday. Confidence remains low on how much
this southerly low will support additional rainfall across the CWA.
Current guidance, and forecast PoPs only favor additional showers
across the San Juans Thursday as the low continues its eastward
journey. Elsewhere, dry Northwest flow encompasses the CWA,
decreasing chance for measurable precipitation. Temperatures dip a
few degrees on Wednesday with the passing trough, though warming
ramps back up in its wake.

High pressure builds back across the southern Great Basin heading
into the weekend, and temperatures follow suit. Forecast highs
exceed 90 degrees in southeast Utah by Friday, which trickle north
into the weekend. Latest guidance has 90 degrees for Moab on
Saturday and upper 80`s across the Grand Valley, which equate to
roughly 5 to 10 degrees above normal for mid May. Fortunately
another low is swept ashore Sunday into Monday, which will allow the
ridge of high pressure to drift eastward, bringing some relief to
summer-like temperatures across the Western Slope.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1118 AM MDT Mon May 13 2024

Cumulus towers are already developing along mountain peaks and
ridge lines. Stirring winds aloft will drift said showers and
thunderstorms off high terrain to the south-southeast this
afternoon. KASE, KEGE, KGUC, and KTEX are the more favorable
terminals out of our batch of TAFs to see vicinity showers and
thunderstorms. More than likely impacts, for all TAF sites, will
be increased wind gusts up to 20 kts at the surface from
outflow boundaries and/or deep mixing above dry, desert valleys.
Afternoon storms and winds will taper off this evening,
resulting in VFR conditions across the board overnight.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MMS
LONG TERM...ERW
AVIATION...TGJT