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000
FXUS65 KGJT 270006
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
606 PM MDT Mon Oct 26 2020

.UPDATE...
Issued at 601 PM MDT Mon Oct 26 2020

Light orographic/over-running snow showers will be possible
through the evening. There is not enough threat of significant
snowfall to justify winter headlines so have let expire or
cancelled them. The screaming message is cold. Our high at GJT is
27 so far...the coldest day before that was 44 in 1970. Montrose
had a high of 18 42 below normal. Nuff said. Well except there
will be plenty of cold records broke in the morning with possibly
the coldest October readings ever.

UPDATE Issued at 1254 PM MDT Mon Oct 26 2020

Several forecast zones including the Grand Mesa, Vail Pass, the
Uncompahgre Plateau, and Cortez-area have been allowed to expire
early today. Snow has diminished in intensity and no accumulating
snow is expected for the remainder of the afternoon in these
zones.

UPDATE Issued at 600 AM MDT Mon Oct 26 2020

The heavy snow threat has ended for valleys along and north of
I-70 therefore several warnings have been allowed to expire. Light
snow showers or flurries may linger today in the very cold
airmass. Continue to use caution if travelling today as roads
remain icy to snowpacked.

&&

.SHORT TERM...(Tonight through Tuesday night)
Issued at 100 PM MDT Mon Oct 26 2020

The current winter storm continues to wind down over the western
slope today. Low pressure will dive south of the Four Corners and
cut off this afternoon and evening. As primary jet support for
snow moves east of the divide in the southern San Juans,
lingering light to moderate snow will diminish in intensity. This
has already begun along portions of the 160 corridor including
Cortez and Durango, partially explaining the slightly lower snow
totals in this area. Even the higher terrain of the central and
western San Juans has not seen quite as high of snow totals as
originally forecast, given the quick translation of the jet and
lifting mechanisms to the east of the Continental Divide today.
Regardless, much of the rest of northwest/west-central Colorado
and eastern Utah met or exceeded storm expectations with this
event - a notable victory for short-term mesoscale modeling and
the collaborative forecast process.

Low temperatures overnight will remain the primary forecast
challenge in the short-term. The expectation is for lingering
low/mid level clouds to clear shortly after sunset in all
locations except the San Juans and points southward. Fresh
snowpack, extremely cold temperatures aloft, and very dry air will
result in ideal radiational cooling conditions. Forecast lows are
already near the bottom of available guidance, and have been
further adjusted downward in some of the typically colder high-
elevation valleys. Several all-time October monthly record lows
are on the table tonight, including the 6-degree October record in
Grand Junction.

The cutoff low pressure system to the south of the Four Corners
will continue to slowly spin on Tuesday. Scattered cloud cover and
some isolated snow shower activity will continue in the southern
slopes of the southern San Juan mountains, however no
accumulations are expected. Elsewhere, mostly sunny and
unseasonably cold weather will continue. Overnight lows on Tuesday
night will once again run near or below record values, however
will be around 10 degrees or so warmer than on Monday night.
Forecast confidence remains high through the short-term period.

.LONG TERM...(Tuesday night through Sunday)
Issued at 100 PM MDT Mon Oct 26 2020

Due to frigid air mass, strong inversions are in place. Though, an
overall gradual warming pattern will slowly erode this stable layer
throughout the week. Last weekend`s trough and associated closed low
will swing into southeastern CO Wednesday and continue propagating
over the southern plains. Moisture wrapped around the northwest
periphery of the low may produce light mountain showers along the
southwest San Juans. However, most of the precipitation will fall
across the southern Front Range into southwest CO plains. Beyond
Wednesday...a ridge of high pressure crosses the CWA with another
trough dipping into the Great Basin on Friday. Unfortunately, any
moisture tied to this wave looks to stay well to our north. Instead,
we`ll see some WAA with flow shifting to the SW and maybe some
passing mid to high level clouds. Ridging builds back in over the
Western CONUS by this weekend, maintaining dry and quiet weather
over eastern Utah and western Colorado into next week.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 602 PM MDT Mon Oct 26 2020

A few lingering snow showers will impact TEX and DRO through the
next few hours with MVFR/IFR flight conditions lingering as a
result. Otherwise clearing skies most area and light winds will
lead to a cold VFR night. Clouds and some snow showers will be
possible on Tuesday as this storm system tracks to our south.
Possibly some impacts at KDRO and KTEX but confidence not very
high attm.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...
CO...None.
UT...None.
&&

$$

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