Area Forecast Discussion
Issued by NWS Grand Junction, CO

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FXUS65 KGJT 091054
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
354 AM MST Tue Mar 9 2021

.SHORT TERM...(Today through Wednesday)
Issued at 354 AM MST Tue Mar 9 2021

Southwest flow will increase across the region today as a low
pressure system moves into the Pacific Northwest and a 140 kt jet
rounding the base of the trough through the Desert Southwest/Baja
Peninsula into the Four Corners. We`ve seen some semblance of
these stronger upper level winds as a small mountain wave formed
over the Uncompahgre Plateau overnight, allowing enough
downsloping winds to mix down in Montrose where it gusted 40 to 50
mph at times. High clouds are increasing across southeast Utah
into southwest Colorado, which put a damper on these downsloping
winds as it is now calm in Montrose at this hour. So, breezy
conditions will exist this afternoon across the region with wind
gusts just under wind advisory criteria across southeast Utah in
the 30 to 40 mph range. These southwest winds will allow for good
mixing today for another warm afternoon with temperatures about 10
to 15 degrees above normal. Enjoy the warmth for one more day as
this all changes on Wednesday as a shift towards cooler and
unsettled weather arrives.

Precipitation looks to increase across the eastern Uintas and
spread into western Colorado, mainly affecting the higher
elevations this evening into Wednesday. The best QG forcing passes
through northeast Utah into northwest Colorado, with the bullseye
more in Wyoming tonight through Wednesday afternoon before
subsidence takes hold Wednesday evening. Enough instability exists
with steep lapse rates around 8C/km with some low level
convergence across the northern mountains along the CO- WY border.
In coordination with CYS and BOU offices, decided to issue a
Winter Weather Advisory for the Elkheads and Park Range (COZ004)
from 8 pm this evening through 5 pm Wednesday, where 4 to 8 inches
of snow looks likely. Even though the southwest wind direction is
not so favorable for this area, the winds do shift towards the
west by Wednesday and winds look to gust up to 45 mph at times,
which would impact travel. Temperatures on Wednesday will be much
cooler with readings closer to normal due to increased clouds and
showers, as well as a cooler air mass settling in.

.LONG TERM...(Wednesday night through Monday)
Issued at 354 AM MST Tue Mar 9 2021

A prolonged period of unsettled weather will continue through the
coming weekend thanks to a low pressure system dropping into the
Desert Southwest and becoming closed and cut off from the main
upper level flow. Model forecasts are still in agreement on the
progression of this low through Saturday. The low is progged to
reach the CA/AZ/NV border by Friday afternoon, and the Four
Corners region by Saturday afternoon. Despite the reasonably good
agreement between models, the GFS and GEFS are still trending a
bit more progressive than the ECMWF and its ensembles at the end
of the long term period, Saturday into Sunday. This could have an
impact on how much precipitation the central and southern
mountains ultimately see from this storm.

On Thursday, the precipitation shifts south, bringing around 2 to
5 inches for the central and southern mountains. From Friday
morning through Sunday morning, the snow will be focused mainly
over the San Juan Mountains and central divide. Current forecast
guidance has around 4 to 8 inches of snow for the San Juans over
this 48 hour period, but this is where the uncertainty in the
track of the low over the weekend could really change things. The
Front Range does appear favored for higher snow accumulations as
lee side cyclogenesis takes place. It`s likely the forecast totals
for this period will change over the coming days as confidence
increases.

Summing it all up, a change to cooler and unsettled weather is
expected mid to late week into the coming weekend, with
temperatures right around average or just below. Over the course
of Thursday and Friday, the precipitation will shift south,
affecting the central and southern Colorado mountains. By the
weekend, the snow will be focused mainly on the San Juans as the
low starts to lift northeast.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1015 PM MST Mon Mar 8 2021

Strong winds aloft will result in wind shear at most terminals
overnight into early Tuesday. Expect VFR on Tuesday with some mid
and high level clouds. Gusty winds will mix to the surface by
afternoon, especially in higher elevation terminals in the
Colorado mountains.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...Winter Weather Advisory from 8 PM this evening to 5 PM MST
     Wednesday for COZ004.

UT...None.
&&

$$

SHORT TERM...MDA
LONG TERM...BGB/MDA
AVIATION...MAC



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