945
FXUS65 KGJT 132332
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
532 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 MONDAY/...
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 /00Z TAFS THROUGH 00Z WEDNESDAY/...
Issued at 532 PM MDT Mon May 13 2024

Ongoing shower and thunderstorm activity this evening will
continue across portions of eastern Utah and western Colorado
for a few more hours before diminishing after sunset. However,
another batch of showers is likely to move across the northern
tier overnight before exiting around or just after sunrise
Tuesday morning. By Tuesday afternoon, another round of
scattered showers and thunderstorms will develop across the
higher elevations before drifting into some of the adjacent
valleys below. Convection will be in play for most terminals
Tuesday afternoon, with gusty outflow winds the main threat.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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