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334
FXUS65 KGJT 190924
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
324 AM MDT Sun May 19 2024

.KEY MESSAGES...

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- Isolated to scattered showers are storms are expected today
  north of I-70. Gusty outflow winds and small hail will be the
  primary concerns from storms.

- Dry, warm and breezy weather will continue down south today
  with high`s trending well above normal this afternoon. Even
  stronger winds are expected on Monday.

- A larger system moves through early next week resulting in
  cooler and wetter conditions. Drier weather looks to return by
  midweek before another system approaches late in the week.
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&&

.SHORT TERM /THROUGH MONDAY/...
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Issued at 324 AM MDT Sun May 19 2024

The NAMNest has been the clear winner tonight with nailing down
the coverage of nocturnal showers, focused across northeast Utah
and northwest Colorado with some light returns over the San Juan
Mountains. Showers have persisted in response to yesterday`s
shortwave trough continuing to lift north through the forecast
area, though this feature is still anticipated to stall later
today. This will be in response to the deepening of an upper
level trough across the western CONUS today. Originating from
central Alberta, the trough`s axis will extend as far south as
southern California, resulting in a tightening southwesterly
gradient aloft throughout the Desert Southwest. So, until this
low begins to shift east, our forecast area will be under the
influence of breezy and mild southwest flow as that stubborn
boundary straddles the Wyoming border.

Taking a look at today`s precipitation trends, this morning`s
ongoing isolated to scattered showers up north will gradually
fizzle out over the next few hours, though a stray shower will
linger near the Uintas into mid morning. We may see a clear
radar for a couple of hours before activity redevelops over the
higher terrain by noon. Conditions remain juicy across the
northern two-thirds of the forecast area with PWATs staying
around 150 percent of normal. This, paired with daytime heating
and weak lift from the boundary itself, will see showers and
storms increase in coverage throughout the afternoon. The 00Z
sounding yesterday evening had a prominent inverted-V profile,
which means that gusty outflow winds in excess of 45 mph will
once again be possible with storms. Additionally, small hail
will likely come into play due to better instability on the
magnitude of 300 to 500 J/kg this afternoon. As far as what we
can expect down south today, CAM guidance is in good agreement
regarding the presence of a sharp gradient of showers / no
showers that essentially lines up with the I-70 corridor. This
means another dry and warm day under mildly breezy conditions
with southwest gusts of 20 to 30 mph.

Late tonight and into Monday the upper level trough will
continue to strengthen, even absorbing a weak wave near Baja as
it does. Southwest flow will increase in earnest across eastern
Utah and western Colorado as the subtropical jet is deflected
directly overhead by midday Monday. These stronger winds will
mix down the profile with 700 mb winds expected to reach at
least 35 kts in the Four Corners region. At the moment this
translates to surface gusts that are subadvisory, though some
gusts in excess of 45 mph are likely in the higher terrain.
Still something to monitor over the coming shifts. Regardless,
it will be dry and windy down south with humidities dropping
into the single digits to low teens. However, fuels have not
been declared critical so no fire weather highlights have been
issued. Fire weather concerns decrease the farther north you go
as, similar to today, a stalled boundary will fuel another round
of showers and storms with persistent cloud cover. Wetting
rains are anticipated after a couple of days of convection with
some very wet snow even falling at the highest peaks of the
Eastern Uintas. Even so, gusty outflow winds and small hail will
once again be possible with storms.
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&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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Issued at 324 AM MDT Sun May 19 2024

Monday evening a generous cold front works its way into the northern
portion of the CWA following a rather warm and windy day. Models are
painting a widespread batch of showers developing along the front
Monday night and Tuesday morning. Showers will likely continue into
Tuesday afternoon, as the upper level trough is slow to drag through
the region and a series of vort lobes pulse through the base of the
trough. Cold air, cloud cover, and showers will see afternoon highs
Tuesday some 15 degrees cooler than previous days. Models begin to
quiet down Wednesday, as broad cyclonic flow retreats northward. Our
northern counties will likely remain under some influence of a weak
frontal boundary trying to hang up along our WY border on Wednesday
morning. Generous southwesterly flow should push enough warm air
back in Wednesday afternoon to drive temperatures back within 5
degrees of climatology and send the frontal boundary northward. By
Thursday afternoon, another weak frontal boundary sags southward
along the persistent Canadian low pressure and brings another round
of clouds and perhaps a scattered shower or two. Models begin to
pinch off another trough to our west Friday and Saturday. This has
become a familiar solution over recent weeks with a jet digging down
the PACNW coast and trying to deepen a Vancouver low into a more
formidable storm. Beforehand though, the pinched trough kicks across
the Great Basin and brings showers back to the forecast Friday and
Saturday. This will likely be another focused boundary draped across
the CWA, with precipitation and cloud cover focused over a tighter
area than model resolution at this time will accurately convey. For
now it looks like we can expect cooler and wet conditions to begin
the week, with a brief spell of quiet weather leading into another
active pattern late week. Temperatures ebb and flow this week, but
trend around climatology most of the week after Tuesday`s cool
down.
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&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1139 PM MDT Sat May 18 2024

A few scattered showers will linger over northwest CO and
northeast UT tonight along a stalled frontal boundary. Most of
this activity will break up by daybreak. However, the frontal
boundary will remain in place and help with showers and
thunderstorms north of I-70 Sunday afternoon as things warm up.
Winds aloft remain strong and are expected to mix down to the
surface with gusty southwest winds around the region. Terminals
will see winds gusting around 25-35 mph, with a few stronger
bursts from thunderstorm outflows. Small hail remains a concern
as well Sunday afternoon. Showers and winds will quiet down
towards the end of this TAF period Sunday night.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MMS
LONG TERM...LTB
AVIATION...TGJT