789
FXUS65 KGJT 141127
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
527 AM MDT Tue May 14 2024

.KEY MESSAGES...

- Shower and thunderstorm activity is expected again today and
  will likely linger into the early morning hours of Wednesday.
  Gusty outflow winds in excess of 45 mph will be a threat with
  with storms this afternoon and evening.

- Another round of storms occurs tomorrow as the troughing
  phases across the eastern Great Basin and Rockies.
  Temperatures look to drop to near or slightly below normal.

- Drier and much warmer conditions are forecast to end out the
  week and persist into the weekend.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 259 AM MDT Tue May 14 2024

Water vapor imagery early this morning is showing a compact
wave moving across western WY providing the ascent needed for
nocturnal convection over our northern CWA. Dew points across
the North indicate a slightly more favorable profile for
getting measurable rainfall down to the valley surface.
Satellite and radar imagery also show a plethora of outflow
boundaries/weak gravity waves drifting southward which is
helping to pop additional isolated storms south of I-70 into
east-central Utah...but most of this shower activity has been
unmeasurable. Models of course struggling a bit with this
scenario and will likely be updating near term grids through the
next several hours to keep up with reality. Planning on a
downturn through the mid morning hours as weak subsidence behind
the Wyoming wave briefly caps the atmosphere until we again hit
the free convective temperature by mid day. This convection
will be aided by the next wave in line moving into western Idaho
attm which will track across our northern border by mid
afternoon through the evening. Additional ascent will be focused
across the central CWA by a strengthening jet streak as energy
curves through the base of the parent trough to the North along
with moistening mid level flow and orographics. The main threat
from storms today will be the gusty outflow winds another warm
day leading to a robust EML. These outflows are likely to keep
the convection going well into the early morning hours such as
the current situation...but where and when is a very low
confidence forecast. By tomorrow another wave dropping down the
backside of the trough departing into the Plains will phase with
the southern stream low moving into the Desert SW. The forcing
isn`t off the charts but conditional instability and terrain
circulations will again lead to showers and storms popping by
late morning and expanding through the afternoon. Temperatures
the next few afternoons will be hampered just a bit by the
clouds and better storm coverage. They should be the coolest of
the forecast running a bit above normal today then near normal
tomorrow. Clouds and outflows likely to keep another mild night
in place tonight.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 259 AM MDT Tue May 14 2024

Wednesday afternoon`s shower and thunderstorm activity is expected
to linger through the night as another lobe of energy tracks through
the base of the trough overhead, dragging a weak boundary along with
it. Activity is expected to linger longest along the Divide and
across southwest Colorado, but will taper off after midnight as the
entire system shifts to the east. At the same time, the cutoff low
pressure that has been lingering over southern California will
finally be absorbed into the base of the trough and will track
eastward through the day Thursday. The best lift associated with
this feature will track across the Desert Southwest, far enough
south of the CWA to limit it`s influence. Only the San Juans are
forecast to see any precipitation out of this event, with low-end
PoPs in the forecast currently. The remainder of the area sees drier
air and higher pressure build in on Thursday, with clearing skies
and temperatures jumping around 5 degrees compared to the day
before. This trend of drier and warmer weather will stick with us
into the weekend, as high pressure remains in control. By Saturday,
temperatures will be running around 10 degrees above normal, with
the desert valleys seeing upper 80s to low 90s, the higher elevation
valleys looking at 70s to low 80s, and the mountain towns seeing
upper 50s to mid 60s. Overnight lows will also remain mild through
the period.

By Saturday, flow aloft will shift to southwesterly over eastern
Utah and western Colorado as the ridge axis shifts east in response
to a Pacific trough tracking across the Northwest. In addition, yet
another cutoff low is forecast to be off the Southern California
coast. This setup will allow that southwesterly flow to tap into
some deeper subtropical moisture and begin advecting it into the
region. This uptick in moisture on Saturday will bring the return of
mountain showers and thunderstorms, although, with little upper
level support, these showers will likely remain over the higher
terrain and adjacent high valleys. For Sunday into the coming week,
model guidance isn`t in the best agreement. The question is, how
will the cutoff low be handled? Will it be quickly reabsorbed into
the trough? Or will it linger and keep troughing overhead of the
Western CONUS into the coming week? Only time will iron these
questions out. As it stands, it does look like a more troughy
pattern will return for the coming week, with slightly cooler and
more unsettled conditions expected.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 527 AM MDT Tue May 14 2024

VFR conditions should prevail over the next 24 hours even with
passing showers and thunderstorms at times. ILS conditions could
temporarily set up but it the gusty outflow winds that will be
the main concern through the evening. Conditions will be
favorable for gusts exceeding 45 mph in some of the outflows
coming from storms but the probability of this occurring at a
TAF site is less than 30 percent. Therefor VC has been been used
in the forecast until confidence increases.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...15
LONG TERM...BGB
AVIATION...GJT