715
FXUS65 KGJT 282126
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
326 PM MDT Sun Apr 28 2024

.KEY MESSAGES...

- Showers diminish this evening as the atmosphere stabilizes in
  the wake of today`s disturbance.

- Above normal temperatures return during the first half of the
  week.

- A fast moving system in northwest flow will bring another
  round of showers and localized thunderstorms to the eastern
  Uinta Mountains and northwest Colorado Monday night through
  Tuesday morning.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 326 PM MDT Sun Apr 28 2024

Expect showers to diminish this evening in the wake of the weak
short wave passing over the forecast area now, along with
cooling surface temperatures helping stabilize the atmosphere.
Skies clear from west to east during the night, though clouds
are likely to hang on over the northern and central Colorado
mountains through sunrise Monday.

Flow becomes zonal on Monday as a trough sweeps from the West
Coast to the Great Basin during the day. An increased pressure
gradient across the north should lead to breezy afternoon winds.
Warm air advection combined with morning sunshine will lead to
warmer temperatures Monday afternoon with readings expected
climb to near 5 degrees above seasonal norms for most locations.
A modest push of moisture ahead of the trough combined the
destabilizing effect of surface warming may lead to isolated
showers/thunderstorms over the eastern Uinta Mountains as well
as the Elkhead, Park and Flat Top Mountains during the
afternoon.

Shower chances ramp up Monday evening and become likely across
the northwest Colorado plateau and the northern Colorado
mountains overnight. This fast moving system is expected to
deliver up to 6 inches of new snow across portions of the Park
Range, mainly above 9,000 feet. More scattered activity is
expected along the I-70 corridor east of the Debeque Canyon and
portions of the Grand Mesa and central Colorado mountains. Areas
to the south will see little chance for precipitation from this
quick hitting storm. Despite pushing a cold front to near the
I-70 corridor, overnight lows are expected to show little change
as gradient driven winds keep the lower levels mixed.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 326 PM MDT Sun Apr 28 2024

Flow becomes zonal on Monday as this weekend`s storm moves to
the Upper Midwest, forced east by a mid-level short wave trough
ejected from a closed low off the coast of British Columbia.
The regional airmass will be largely drier in the westerlies
promising quiet weather Monday morning while temperatures climb
several degrees above normal during the day. However, model
consensus indicated the potential for convective showers over
the northern mountains in the afternoon as modest moisture
moving ahead of the previously mentioned short wave filters in
throughout the day.

The short wave trough moves eastward Monday night driving a cold
front across the northern half of the forecast area. Meanwhile,
moisture and lift along and north of the front is expected to
bring another round of precipitation to the northern mountains
and northwest Colorado plateau with a chance for showers over
the central Colorado mountains and the eastern Uinta Mountains.
A bit of a lull in activity is expected Tuesday as flow again
becomes zonal in the wake of the disturbance, though scattered
instability showers are possible, mainly over the Elkhead, Park
and Flat Top Mountains. Despite the passage of the cold front,
temperatures are expected to be near, or only a few degrees
cooler than on Monday across northeast Utah and northwest
Colorado and a few degrees warmer along the I-70 corridor and
south.

On Wednesday, models were in good agreement showing a positive
tilt trough moving over the Intermountain West and Great Basin
causing flow aloft to shift to the southwest. As this plays out,
moisture ahead of the trough overruns the stalled front over
the northern portion of the forecast area resulting in a good
chance for showers, especially for the northern and central
mountains of Colorado. Meanwhile, a tightening of the pressure
gradient ahead of the approaching disturbance will bring breezy
conditions to the northern zones Wednesday afternoon and
evening. Cloud cover and showers should bring a few additional
degrees of cooling to the north while areas to the south can
expect little change in temperature and little chance for
precipitation.

The forecast is less clear for the remainder of the week as the
ECMWF slows the eastward progress of the mid-level trough as
compared to the Canadian and GFS solutions which were more
progressive. The latter two models suggested little chance for
additional showers Thursday and Friday while the ECMWF depicted
active weather Thursday and Thursday night and lingering Friday
with the north again favored. Model blends indicated chance
precipitation for the Continental Divide, and particularly for
the northern Colorado mountains Thursday and Friday and this
seemed to be the appropriate forecast for now. Given trough
passage sometime at the end of the week it stands to reason
Thursday, and to a lesser extent Friday, will be cooler.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1145 AM MDT Sun Apr 28 2024

Just as this morning`s low clouds and fog started clearing out,
daytime heating and a weak wave moving overhead have allowed
clouds to start filling back in. Ceilings will hover between
VFR/MVFR across most mountain terminals this afternoon with ILS
breakpoints being reached at times as well. Scattered showers
and a few storms will be around but will start to diminish after
the sun sets. Any shower or storm can produce erratic and gusty
winds. More widespread VFR returns late this evening with skies
becoming partly cloudy overnight. Quiet weather then prevails
through the day on Monday with light, terrain driven winds.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

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