Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 211957
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
157 PM MDT Thu Mar 21 2024

.KEY MESSAGES...

- A weak disturbance this afternoon, and a second one tomorrow
  evening, will bring light mountain showers to the northern
  tier of the area. Rain below 8000 feet, snow above 8000 feet,
  and a few rumbles of thunder expected, with minimal
  accumulations.

- High temperatures of 5-10 degrees above normal linger through
  Saturday, with mostly to partly sunny skies.

- A more impactful storm system is expected to bring widespread
  precipitation, including mountain snow, along with cooler
  temperatures from Saturday night through Sunday night.

- Cooler and unsettled conditions continue into next week.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 153 PM MDT Thu Mar 21 2024

Abundant sunshine and a few diurnally driven mountain clouds are the
story for the day so far. Temperatures have already climbed at or
above the climatological normals and we still have a few hours to go
before we reach the expected highs. As we`ve seen the last few days,
highs this afternoon will be 5-10 degrees above normal. A shortwave
trough is approaching the area from the northwest, bringing some
increased cloud cover and shower activity to the eastern Uinta
mountains this afternoon. Activity will spread south and east
through the afternoon and evening, bringing showers and maybe a few
rumbles of thunder to the northern and central Colorado mountains.
Thanks to some dynamic lift with this shortwave, shower activity
will be able to linger past sunset and loss of heating. However,
with the shortwave progged to track east of the Divide between
midnight and daybreak, showers will taper after midnight. Outside of
the mountains, eastern Utah and western Colorado are in for another
clear and quiet night, with a few passing high clouds. Lows will
bottom out near to a few degrees above normal. A shortwave ridge
builds in tomorrow, bringing yet another day of abundant sunshine
and high temperatures 5-10 degrees above normal. The ridge axis
passes overhead late tomorrow afternoon, with flow aloft shifting to
southwesterly out ahead of our next Pacific trough. This
southwesterly flow will advect deeper remnant AR moisture up into
the Great Basin and eastern Utah and western Colorado, leading to
steadily increasing cloud cover Friday night into Saturday morning.
This cloud cover will act a bit like a blanket, keeping low
temperatures substantially warmer than we`ve seen over the last
several days, a solid 10 degrees above normal for late March. Some
mountain showers will also be possible late Friday into Saturday
morning thanks to yet another shortwave trough moving through the
flow. With the showers this evening and tomorrow night, snow will be
confined above 8000 feet, with lower elevations seeing either rain
or, where substantial dry air remains at the surface, virga showers
and some gusty winds. Snow accumulations will be minimal, an inch or
less each day.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 153 PM MDT Thu Mar 21 2024

Transitory ridging moves overhead then East of the CWA Friday Night
as a Springtime progressive pattern emerges for the long term
outlook. This means a few things...cooler and wetter conditions
moving with a bit of uncertainty on all things snow.
More certain however is winds since it is now officially Spring.
Heights will be crashing upstream over the West increasing the
downstream Southwest gradient over our area by Saturday.
Afternoon gusts in the 30 to 40 mph range across the lower
elevations of SE.Utah and W.Colorado are probable (>60%) looking at
the cluster data. Gusts over 45 mph where we get into some kind of
wind headline is not quite as certain at this point and could be
hampered by cloudiness. Things take a drastic turn late Saturday
into Sunday and really into the mid-week period as troughiness takes
over bringing cooler and unsettled conditions back into the picture.
SubTrop moisture will be on a good path to the Rockies as it is
transported in the SW flow aloft...across the SoCal/Baja region. The
PWAT anomaly and IVT numbers (residual AR) suggest a modest amount
of moisture moving across the Intermountain West but M-Climate
precipitation amounts are nothing to get too excited about just yet.
For now it does not look like this will be a repeat of the last
storm cycle with 3-4 inch SWE increases...but we will get a boost to
the overall snowpack in the mountains and some wetting rainfall
across the lower elevations. The bulk of this comes Sunday with the
fropa and the dynamics arriving with the main trough. This first
event will taper some by early Monday but in reality embedded waves
and colder air aloft is likely to keep some places in the Colorado
High Country snowing well into Wednesday. A pair of more distinct
embedded waves move through Monday and Tuesday afternoons which
should give the convective and orographic components a boost under a
general NW flow regime. Early estimates suggest a few tenths of
precipitation in the valleys ramping up to 1 to 2 inches over the
high country near or above 10kft from Saturday afternoon onward.
Exact impacts are fuzzy but obviously worst case scenarios remain
during the overnight hours when the snow and roadways are less
likely to play nice together...with improvement through the daylight
hours as the higher sun angle works its magic. Temperatures Saturday
start out 5 to 10 above normal and by Sunday drop to 10+ below
normal for daytime highs. Though a slow warming trend is suggested
through next week we should still stay several degrees below normal
most areas.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1126 AM MDT Thu Mar 21 2024

VFR conditions under mainly clear skies and light winds will
give way to some increasing mid level cloudiness and afternoon
breezes as the next fast moving system works through. Isolated
to scattered showers will spread across northern and central
portions of Utah and Colorado through the late afternoon hours.
Gusty winds below virga or near showers will be more of a threat
than precipitation and less than VFR conditions are not
anticipated. A few sites may temporarily see ILS cigs as this
works through but clearing by early Friday is forecast. About
the only small concern will be upvalley flow into KASE through
the afternoon and early evening.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...BGB
LONG TERM...15
AVIATION...TGJT


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