Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 240551
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1151 PM MDT Sat Mar 23 2024

.KEY MESSAGES...

- Isolated high-based showers and storms are expected through
  this afternoon ahead of the next system.

- Showers become more widespread this evening and Sunday as a
  strong cold front brings temperatures and snow levels down.

- Moderate mountain snow is expected through Monday morning with
  travel impacts over the passes increasing during the overnight
  hours. Rain will fall in the lower valleys with only light
  snow likely in the higher valleys.

- Unsettled weather continues through the coming week with
  additional disturbances bringing scattered showers.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 340 PM MDT Sat Mar 23 2024

Isolated shower activity has blossomed on radar in the last few
hours though much of this appears to be virga. This morning`s
12Z sounding saw an increase of almost two-tenths of an inch
from 12 hours prior with an uptick in midlevel moisture. All
the same, the low levels remain dry with DCAPE sitting just
below 600 J/kg. This has led to some breezy conditions at the
surface, in addition to any gusts associated with virga showers.
Southwest winds have remained in the 25 to 35 mph range for most
areas, though there have been some stronger gusts around 45 mph.
Available moisture will continue to climb through the short term
period with PWATs reaching almost 180 percent of normal for much
of the higher terrain. Additionally, the cold front associated
with the approaching upper level trough will begin to dig into
the northern portions of the forecast area late tonight before
pushing southeast Sunday afternoon. Broad scale ascent becomes
maximized during this period as a vort max lifts across the Four
Corners area. In response, widespread valley rain and mountain
snow showers are expected with snow levels dropping to 5500 to
6500 ft in the front`s wake. The western Colorado mountains as
well as the La Sal ranges will receive the greatest precip rates
into Sunday afternoon with the San Juan Mountains particularly
favored tonight under strong upslope flow as the vort max passes
overhead.

Trough passage occurs Sunday morning and afternoon, allowing the
unsettled weather to persist into the overnight hours. Lapse
rates will steepen with the trough which will lead to more
convective showers across the Western Slope. As a result,
showers and storms will become more scattered in nature but
higher elevations along the Divide will still see showers much
of the day. By Sunday evening, flow aloft will shift to the
northwest, advecting drier air into the region. The western
zones will see a notable drop in shower coverage with activity
persisting over the southern and central Colorado mountains into
Sunday night.

As far as amounts go, there wasn`t much change in the forecast
compared to previous runs. 6 to 12 inches is expected for almost
all of the mountain ranges with favored slopes receiving locally
higher totals in excess of 14 inches. Additionally, CAM guidance
continues to highlight the potential for heavier bands of snow
which could also lead to higher totals. Even so, opted to keep
the ongoing highlights as is given the reduced period of impact
Sunday afternoon under the high March sun angle. Regardless, be
sure to check the latest forecast and road conditions before
heading out! The higher valleys will likely see a brief period
of snow along and behind the cold front, but accumulations on
grassy surfaces will be light, no more than 1 to 3 inches.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 340 PM MDT Sat Mar 23 2024

The high amplitude pattern of the high latitudes will have
dropped to mid latitudes Sunday night. A high pressure ridge
over the EPac transitions to low pressure extending from Hudson
Bay to the Baja then another ridge along the eastern seaboard.
Upstream energy will continue to back-fill into this Western
Trough and keep a cool and unsettled forecast in place well
through the mid-week period. Most of the mid to upper support
will be shifting to our south by Monday morning brining a
downturn to the widespread precipitation. This will leave mainly
cold advection orographic snow in place over favored ranges
such as the Uintas and San Juans. Things will begin to bubble
again by the afternoon as the next embedded wave drops through
the northerly flow and allows the trough to be re-carved back to
the West. This late Monday impulse will be followed by
channelized vorticity stretched along the backside of the trough
moving across the area through early Wednesday. A nearly
uninterrupted period of light mountain snow and valley showers
will arise as a result...with a slight boost to rates due to
afternoon instability showers. Taken as a 3 day total...snow
amounts are not overly impressive and day by day even less so.
Impacts should mainly occur during the overnight hours as snow
is able to accumulate on the roadways. Be Wednesday afternoon
heights will be rising with the transitory ridge moving across
the Rockies on Thursday. This will again be followed by
tightening SW flow Friday into Saturday as the next strong
system digs onto the Pacific shoreline. Ensemble clusters are
favoring this system remaining along the coast through this
forecast period before shifting inland on Sunday. Temperatures
below normal to start out the week push to near to above normal
from Thursday onward.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1151 PM MDT Sat Mar 23 2024

Scattered showers and isolated thunderstorms will continue to
move through the area from southwest to northeast for VCSH at
most TAF sites and brief periods of reduced CIGS and VSBY in
showers. Showers become more widespread after 12Z Sunday morning
and into the afternoon as the cold front moves through with
gusty winds prevalent overnight and ahead of the cold front.
Expect VFR for most sites until after 12Z where MVFR may be more
common in showers with periods of IFR more likely over the high
terrain where snow is expected. Precipitation lingers into
Sunday evening across the western Colorado divide.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Winter Weather Advisory until midnight MDT Sunday night for
     COZ003.
     Winter Weather Advisory until 6 AM MDT Monday for COZ004-009-
     010-012-013-018-019.
     Winter Weather Advisory until midnight MDT Sunday night for
     COZ017.
UT...Winter Weather Advisory until midnight MDT Sunday night for
     UTZ028.

&&

$$

SHORT TERM...MMS
LONG TERM...15
AVIATION...MDA


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