Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 170545
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
1145 PM MDT Sat Mar 16 2024

.KEY MESSAGES...

- Scattered to widespread valley rain and mountain snow showers
  are expected today and tonight across southeast Utah and
  Southwest Colorado.

- Accumulating snow possible in the southern mountains today
  generally above 8 kft.

- The chances for showers will continue just about each day
  across the south until the system lifts out of the Desert
  Southwest around mid week.

- Impacts from any snow should stay confined to the overnight
  and early morning hours as well as the highest elevations.

&&

.SHORT TERM /THROUGH MONDAY/...
Issued at 248 PM MDT Sat Mar 16 2024

The stubborn closed low has taken up residence in west-central
Arizona just east of the southeast Nevada and California border
with Arizona and doesn`t appear to be leaving any time soon.
Potential vorticity lobes continue to rotate around the low from
southeast to northwest, producing scattered showers across
southwest Colorado and southeast Utah. Showers are even reaching
as far north as I-70 but seem to be remaining south of the
interstate for the most part or at least loosing their steam. A
bit of dry air has infiltrated the Four Corners region, allowing
for a bit of a break in the cloud deck before filling in again
with afternoon convection as lapse rates steepen. Upon looking
at webcams and observations across the area, the roads among the
higher elevations of the San Juans remain wet where it is
snowing and dry otherwise with some breaks of sun shining
through. Lower valleys are seeing periods of light rain at this
time, but it`s pretty sporadic given the convective nature of
the showers. Rates have lessened quite a bit so little impact
is seen during the afternoon. Most impacts seem to be relegated
to the highest elevations and the passes during the overnight
and early morning hours with lack of sun and colder
temperatures.

The low is expected to shift a bit further eastward into
eastern Arizona and also drop southward as an area of high
pressure builds in and expands across the Pacific Northwest into
the Intermountain West by Sunday. This should result in a
lessening of snowfall rates after midnight tonight with the San
Juans continuing to pick up snow through Sunday morning. Current
Winter Weather Advisories paint the picture pretty well with an
additional 3 to 6 inches across most southern mountains, with
the southwest San Juans picking up an additional 5 to 10 inches
given better forcing and favorable orographics. The timing
remains on track and even though additional snow will fall
Sunday afternoon across the San Juans given the convective
potential, roads will remain wet with limited impact and
snowfall rates lessen considerably as forcing wanes with the
best forcing shifting south of the region with the movement of
the low.

The high pressure moving in to the north of the low will shift
into the northern Great Basin, further suppressing the closed
low as a Rex Block forms, which also will prevent movement of
this low until the Rex Block breaks, allowing the low to lift
out of the Desert Southwest. Until then, scattered light showers
look to persist across the southern areas but accumulations
Sunday afternoon through Sunday night appear minimal at this
time with maybe an additional 1 to 3 inches across the San
Juans. Therefore, have no plans to extend or expand any winter
highlights at this time. Temperatures today remain around 5 to 10
degrees below normal across the south where clouds and showers
persist due to the influence of the closed low, while highs
across the north are near to a few degrees above normal.
Temperatures warm up a few degrees Sunday as the low shifts
further south with near normal temps across much of the region
and highs about 5 degrees below normal down south.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Issued at 248 PM MDT Sat Mar 16 2024

The models are in good agreement with the Rex block continuing
in place over the Intermountain West and a deep trough over the
Eastern US. A subtropical leaf of the jet moves up from the
southwest Tuesday night into Wednesday to shear out the upper-
level low to open the cutoff low and eject it to the east
Wednesday. The ensembles also support this scenario with tight
grouping/low dispersion on the member through about Wednesday.
Beyond Wednesday, a zonal flow sets up aloft as another deep low
pressure system descends from the Aleutians to off the
California Coast. This system look to impact the region sometime
next weekend. Some models predict it will set up a longwave
trough across the Western States while others hint at another
Rex block to the west with high pressure building into the
Pacific Northwest. There isn`t much confidence in either
solution, so we`ll just have to wait a few days and see how it
plays out.

With that being said, look for mountain snow and lower
elevation rain showers Monday and Tuesday mostly in the San
Juans and along the Divide into the central Colorado mountains.
Little accumulation is likely with these showers. Late in the
week with the zonal flow aloft, shortwaves will have access to
the region from the north, spawning snow showers over the Uinta
Mountains in Utah and over the northern, and possibly central
mountains of Colorado. Though these shortwaves will bring some
additional moisture with them, especially to the northern areas,
most of the moisture will be residual moisture. Hence, no
significant accumulations of snow is likely with these showers,
but this could change, so stay tuned.

The southern areas will see clouds persist the first half of
the week keeping temperatures near normal, but the mostly clear
skies to the north will allow the northern areas to warm to five
degrees above the seasonal normal temperatures. Under the zonal
flow later in the week, temperatures will warm to five to ten
degrees above normal across the region, which means high
temperatures will be warming well into the 60s for the lower
valleys of eastern Utah and west-central Colorado with highs
near 70 or low 70s for the canyon country of southeast Utah.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1145 PM MDT Sat Mar 16 2024

A band of rain showers will continue to impact KGJT and KCNY
for the next hour or two before conditions improve for the
remainder of the overnight hours. Conditions are quieter down
south, but that will gradually change as another band of
precipitation pushes northward. This will especially affect
KDRO. Elsewhere, generally quiet weather persists with VFR
conditions the rule through the TAF period. As previously
mentioned, downslope winds with gusts near 25 knots will
continue to impact KVEL before diminishing later on today.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Winter Weather Advisory until midnight MDT tonight for COZ017.
     Winter Weather Advisory until 9 AM MDT Sunday for COZ018-019.
UT...Winter Weather Advisory until midnight MDT tonight for UTZ028.

&&

$$

SHORT TERM...MDA
LONG TERM...DB
AVIATION...TGJT


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