741
FXUS65 KGJT 212111
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
311 PM MDT Tue May 21 2024

.KEY MESSAGES...

- Scattered showers and thunderstorms continue through this
  evening before tapering off overnight. Low temperatures will
  be much cooler than normal.

- Warmer and drier weather returns on Wednesday with highs
  roughly 10 degrees warmer than today.

- Mainly dry weather continues through the end of the week
  before more unsettled weather returns this weekend.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 311 PM MDT Tue May 21 2024

GOES-East satellite imagery continues to show a compact
shortwave trough rotating across eastern Utah and western
Colorado this afternoon. Combined with residual moisture and
daytime heating, large scale forcing for ascent is producing
scattered showers and a few thunderstorms... mainly across the
higher terrain along the Continental Divide mountains and
portions of northeast Utah and northwest Colorado. Despite weak
instability, fairly steep lapse rates are resulting in small but
vigorous precipitation cores with moderate to briefly heavy
rainfall rates. At or above 9000 to 10000 feet, this is also
leading to snowfall rates of the same intensity across the
Continental Divide mountains. Given the time of year however,
snowfall accumulations are not affecting road surfaces, with
webcams only showing wet roads on all of our major high mountain
passes. Otherwise, the trough and last night`s cold front have
brought in a much cooler air mass, which is resulting in high
temperatures well below climatological norms.

The trough will exit the region to the east tonight, taking the
remaining showers along with it. Clearing skies and light winds
along with the unseasonably cool air mass overhead will lead to
a pretty chilly night for late May standards, with temperatures
nearing or dropping below the freezing point for many locations
in the higher elevations. Those with agricultural interests or
sensitive vegetation will want to keep an eye on temperatures
tonight into early Wednesday morning.

After a cool start, temperatures will quickly rebound on
Wednesday as flow becomes southwesterly once again. High
temperatures will still be near to slightly below normal, but
much warmer than today. Mostly sunny skies will be the rule,
though a few more clouds may bubble up across the high
elevations along the Continental Divide. Can`t completely rule
out a pop-up shower or two there either, but overall the day
will be mainly if not completely dry.

Another cold front is progged to approach northeast Utah late
Wednesday night and will be on the doorstep right around
daybreak Thursday morning. Other than that, the rest of the
night will be quiet with lows roughly 5 to 15 degrees warmer
than tonight.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 311 PM MDT Tue May 21 2024

The wave train keeps rolling on Thursday as the next mid-level
trough moves across the northern Rockies. This system will drive
a cold front across the area which, when combined with decent
mid and upper level forcing, brings a good chance for
showers/thunderstorms with northwest Colorado and the northern
Colorado mountains favored. Flow aloft becomes west-
southwesterly in the wake of this system on Friday, though
residual moisture, instability and modest jet divergence is
expected to be sufficient to generate isolated to scattered
moist convection over the Colorado mountains, mainly during the
afternoon and evening period. The next trough to impact the
region arrives Saturday resulting in more widespread shower and
thunderstorm activity along with light snow in the higher
elevations. On Sunday a closed low over the northern
Intermountain region pushes eastward just brushing northern
Colorado keeping showers going over the northern and central
mountains, northwest Colorado plateau, and the I-70 corridor
east of Grand Junction. Expect a ridge to build over the Rockies
Monday into Tuesday, though it`s likely modest residual
moisture will fuel a handful of afternoon showers/thunderstorms
along the Continental Divide each afternoon. Temperatures during
this unsettled period will be near or a little below seasonal
norms from Thursday through the weekend before a warming trend
begins Monday into Tuesday.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1220 PM MDT Tue May 21 2024

An upper level disturbance continued to move overhead early this
afternoon and was responsible for showers stretching from
southeast Utah across southwest and central Colorado. Showers
and isolated thunderstorms are likely to impact all but KGJT,
KCNY and KDRO this afternoon/early evening. TAF sites impacted
by showers can expect MVFR conditions with brief IFR conditions
possible through 02Z/Wed with ceilings below ILS breakpoints at
KRIL, KEGE and KASE at times. Conditions improve tonight as
drying occurs on the backside of the trough. Confidence that
ceilings won`t impact KHDN, KEGE and KASE through the night
isn`t high, so look for possible changes with later TAF
issuances.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MDM
LONG TERM...NL
AVIATION...TGJT