484
FXUS65 KGJT 011150
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
550 AM MDT Wed May 1 2024

.KEY MESSAGES...

- A cold front will cool temperatures 5-10 degrees across much
  of the region today and Thursday.

- Valley rains and mountain snow are expected through the day
  today. 1-2 inches of snow is expected above 9000 feet, with
  some higher peaks getting more.

- Scattered showers and thunderstorms will be capable of
  producing small hail, lightning and gusty winds today.

- Warm and dry conditions materialize for the weekend before
  unsettled conditions return early next week.

&&

.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 343 AM MDT Wed May 1 2024

A shallow trough crossing the Great Basin this morning is pushing a
frontal boundary roughly oriented from Las Vegas to Cheyenne, WY
across the west. The narrow band of forcing associated with this
front will impact the region starting this morning around daybreak.
A few scattered showers out ahead of the front were seen on radar
overnight, but extensive dry air at the surface kept much, if any,
from reaching the ground. A richer moisture plume along the front
caught up in the jet max will help with saturating the lower layers
this morning and producing some measurable rain across northeast
Utah and northwest Colorado, as well as some mountain snow. A few of
these showers will likely produce thunderstorms along the front.
Gusty southwest winds will pick up ahead of the front today,
especially under the jet max as it drags across the CWA. Cloud cover
and precipitation will spell out a more dramatic shift in
temperatures this afternoon north of the Colorado River. The shallow
nature of the trough will also mean less cold air spilling in
southward. In fact most of our southwest Colorado and southeast Utah
locales will see afternoon highs similar to Wednesday`s, while up
north 5-10 degree swings in high temperature are expected today. The
front pushes through much of the CWA by this afternoon and a few
showers hang around the western shoulders of the Divide just past
midnight. Clearing skies will drive overnight lows down into the
30`s for our desert valleys and into the teens and 20`s for the
mountain towns Thursday morning. The broad, shallow trough to our
north keeps a frontal boundary draped across the WY/CO state line
Thursday. This will be enough to keep some cloud cover in place
Thursday afternoon. Winds will return more west to southwest too, so
post frontal lapse rates aren`t expected to generate the usual
instability we get here on the West Slope. Still, a few showers are
expected to materialize across northern Colorado and Utah thanks to
persistent vorticity maxima rippling through. Thursday afternoon
highs will trend down 5-10 degrees too and winds will remain gusty
thanks to stronger winds aloft mixing down during the afternoon. A
few showers are expected to continue into Friday morning as the
trough takes its time sliding eastward.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 343 AM MDT Wed May 1 2024

On Friday the next shortwave trough clips northern portions of the
forecast area. It will bring moisture and provide the lift needed
for another round of showers and storms. For now the more scattered
coverage looks to be along and north of I-70, while south of that is
more isolated. The precip amounts are highest in the Park Range with
decreasing values into the valleys. Snow levels should be around 8
kft, with little any accumulation on roads during the day. A tight
pressure associated with the trough will result in gusty winds
across a good portion of the area. That system quickly exits to the
east late Friday causing conditions to dry out. Attention then turns
to a deep low pressure making landfall in the Pacific Northwest this
weekend. As that system moves inland it will force a ridge to build
over the Intermountain West. This triggers some warm advection for
us so expect highs to increase 5-10 degrees from Friday to Saturday.
Models are notorious for struggling with these type of systems, and
there is still disagreement among the deterministic models, so
confidence is low to medium. When that low pressure makes it to our
area it will bring showers, wind and mountain snow. Right now that
appears to be Sunday and Monday. If the low moves further south
along the coast it will delay the arrival.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
Issued at 544 AM MDT Wed May 1 2024

A cold front will work its way through the region today and
tonight. Valley rain showers and mountain snow is expected, as
well as a few thunderstorms along the front. Terminals can
expect to see intermittent IFR conditions within shower
activity. Gusty outflow winds and small hail will also be a
concern around some of the stronger showers. Surface winds will
be strong ahead of the front and begin to subside towards
midnight tonight when the frontal boundary begins to clear the
region. Most places will return to VFR conditions later this
evening, while some clouds and isolated showers will hang up on
the Divide into the early morning hours of Thursday.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...LTB
LONG TERM...KJS
AVIATION...TGJT