Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 182302
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
502 PM MDT Mon Mar 18 2024

.KEY MESSAGES...

- Isolated to widely scattered showers are possible around the
  central and southern mountains today and tomorrow mainly in
  the afternoon with minimal accumulations expected.

- A warming trend begins this week through Saturday with high
  temperatures above normal across the region.

- Enjoy the warm dry weather while it lasts as another storm
  system looks to bring more precipitation and cooler
  temperatures Sunday into early next week.

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 234 PM MDT Mon Mar 18 2024

The vertically stacked closed low pressure system is still
southwest of the Four Corners, although a bit further south than
yesterday. This can be seen on satellite imagery as convection
blossoms over Arizona and rotates counter clockwise around the
low which looks to be near the SoCal and SW Arizona border. We
are still under the influence of the Rex Block as high pressure
continues to build over the northern Great Basin into the PacNW
and Intermountain West, so that low isn`t moving much until
that block breaks down, which looks to happen tomorrow. Hence,
mostly sunny skies are present today with less cloud cover as
well, leading to a milder day. We are seeing some cumulus
popping over the southern mountains but nothing on radar yet.
The CAMs are indicating potential for a few pop up showers this
afternoon, and with modest lapse rates just a bit above 7 C/km,
cannot completely rule out the possibility. Not expecting much
from these though as much of the CWA will see a mostly dry and
pleasant day. Highs will top out a little warmer than yesterday
but still near or slightly above normal.

By Tuesday, the aforementioned closed low over the Desert
Southwest will finally break free of the Rex Block as a robust
120kt jet streak drops into the Dakotas from the deep trough
over eastern Canada and the Great Lakes region. This will be
enough forcing to help lift the closed low out from southwest
Arizona through northwest New Mexico as an open wave, nudging
the high pressure ridge back to the west. We will see enough
lift from this wave to get some showers and convection
developing Tuesday afternoon into the evening over the southern
and central Colorado mountains. Precipitation looks to stay in
the higher elevations for the most part but forcing is pretty
weak by this point, so only a couple inches of snow is
expected, mainly favoring the San Juans with 1 to 4 inches
possible. Lower southern valleys may see some rain but not much
accumulation expected as coverage also remains isolated. Lapse
rates will be steeper with 8 C/km or so and some decent CAPE in
the 200 to 400 J/kg range, so thunderstorms are possible as
well. The best QG forcing remains with the low across New Mexico
and with the higher sun angle and milder temperatures, impacts
among the passes appears limited as most roads should remain
wet. Showers dissipate Tuesday night with loss of daytime
heating and the system already moving east of the area. High
temperatures will be continuing the warmup on Tuesday as highs
reach 4 to 8 degrees above normal across the northern and
central areas with near to slightly below normal down south.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 234 PM MDT Mon Mar 18 2024

Wednesday will see the Four Corners region finally saying
goodbye to that stubborn cutoff low that`s been influencing our
weather for nearly a week. The ridge over the Great Basin will
nudge the weakening low, now an open wave, east into the
southern Plains where it will eventually be reabsorbed fully
into the westerly flow. Meanwhile, high pressure builds in
across eastern Utah and western Colorado, bringing clear skies
and kick off a warming trend, with highs Wednesday around 5
degrees above normal. Daytime heating will act on lingering
moisture over the central and southern mountains to fire off
isolated to widely scattered pop-up rain and snow showers
during the afternoon. Snow accumulations, if any, will be under
an inch and confined to the highest elevations.

Ridging remains in control through the remainder of the week,
but becomes suppressed a bit as multiple waves track by to the
north, leading to quasi-zonal flow aloft over eastern Utah and
western Colorado. That won`t prevent continued warming through
the end of the week, with highs by Friday running 5-10 degrees
above normal. Some of the lower desert valleys will even flirt
with 70 degrees each afternoon. With moisture lingering across
the area and just enough energy from the passing waves in the
westerly flow, expect light afternoon mountain showers Thursday
and Friday, again with minimal if any snow accumulations. A
stronger Pacific low moves into the West Coast on Saturday,
with flow ahead of it turning strongly southwesterly over the
Desert Southwest. This will bring increasing clouds through
Saturday afternoon as additional moisture is advected into the
region, as well as one last boost to temperatures thanks to the
warm air advection. Highs on Saturday could climb as high as 15
degrees above normal in spots.

Models still aren`t in great agreement over the details of this
next storm, which is expected at this lead time, but they are
all in good agreement that by Sunday morning shower activity
will be widespread over eastern Utah and western Colorado,
along with some indication of cold frontal passage during the
day. Snow levels will likely be on the higher side with this
system, thanks the very warm antecedent conditions and the much
stronger Spring sunshine of late March. This will keep impacts
from accumulating snowfall above 7000-8000 feet, with elevations
below that point seeing predominantly rain. Temperatures will
also take a dive for Sunday and Monday, thanks to the increased
clouds, showers, and cold air advection behind the front. Highs
on Sunday will be near normal, which will be 10-15 degrees below
the high temperatures the day before, and Monday is looking to
top out a good 5-10 degrees below normal. Cooler and unsettled
conditions look to remain in the forecast through at least mid
next week. And so we remain on the March weather rollercoaster.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 502 PM MDT Mon Mar 18 2024

VFR conditions will prevail through the period. Mid / high
clouds will pass overhead but CIGS will stay above breakpoints.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MDA
LONG TERM...BGB
AVIATION...TGJT


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