Grand Junction, Colorado 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

064
FXUS65 KGJT 181014
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
314 AM MST Sat Jan 18 2025

.KEY MESSAGES...

- A pattern change is upon us as an Arctic front traverses the
  area this morning with gusty northerly winds and an arctic air
  mass settling in behind it today. Periods of moderate to heavy
  snow will occur over the northwest Colorado mountains as well
  as northwest San Juans in addition to very cold temperatures.

- A strong Arctic outbreak is expected to close out the weekend
  into early next week across the central CONUS. The coldest air
  should remain east of the Divide but temperatures on this side
  are forecast to be well-below normal. Overnight lows have a
  high probability of dropping well-below zero in many mountain
  and high valley/basin areas. As a result, Cold Weather
  Advisories have been issued for the Gunnison and Upper Yampa
  River Basins tonight and Sunday night with an Extreme Cold
  Watch for Monday night.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 314 AM MST Sat Jan 18 2025

The arctic front on the leading edge of a deep upper level
trough is pushing southward across the CWA with snow falling
over the northern and central mountains and even down to the
northwest San Juans at this time. The flow is still primarily
westerly but this should shift to a northerly flow behind this
arctic front as the cold air settles in. Cloud cover is helping
keep temperatures from bottoming out to drastically but expect
this to change tonight where many areas will feel the effects of
this arctic air mass. H7 temperatures will drop as low as -20C
by sunrise so anticipate snow densities to be very high SLRs
with 20:1, resulting in a very fluffy powdery snow. There may be
a bit of a reprieve in snow rates and accumulations over the
northern mountains this morning but rates should pick back up
this afternoon as instability and very steep lapse rates lend
itself to an uptick in snow production and potential for snow
bands. One particular area that looks to see an increase in
snowfall this morning though appears to be the Uncompahgre
Gorge in the northwest San Juans from Ouray to Red Mountain
Pass, which does very well in this light northerly flow. With
temperatures in the dendritic growth range, snow can potentially
pile up here this morning through the afternoon before coming
to an end late in the day as the trough moves eastward. Winter
Weather Advisories remain on track for the Park Range, Flattops,
Gore and Elk Mountains as well as the northwest San Juans
through 5 pm MST today and will make no adjustments here. In
total, 5 to 12 inches looks likely for the Park Range with 4 to
8 inches in the remaining northwest Colorado mountains under the
advisory and 5 to 10 inches in the northwest San Juans,
particularly the Gorge area.

Another weather impact today in addition to the mountain snow is
the wind as breezy northwest winds will follow the trough and
arctic front passage across southwest Colorado. The northwest
flow in these types of events is particularly strong that winds
could gust in the 35 to 50 mph range, so a Wind Advisory remains
in effect from 9 am this morning through 5 pm today for our SW
Colorado valleys, including Cortez and Durango in the Upper
Dolores and Animas River Basins.

Skies generally clear overnight tonight and the effects of this
arctic air mass will be particularly felt in the cold pool
basins. Decided to issue a Cold Weather Advisory for the
Gunnison Basin (COZ014) and Upper Yampa River Basin (COZ005)
from 10 pm this evening through 11 am Sunday morning as low
temperatures are expected to bottom out into the -25F to -30F
range under these deep strong inversions. This arctic air mass
will only reinforce these strong inversions resulting in much
colder temperatures here. Elsewhere, it will be cold, but not
cold enough to consider any Cold Weather products. Also, issued
a Cold Weather Advisory for the Gunnison Basin for Sunday night
into Monday morning. Went ahead and issued an Extreme Cold Watch
for the Gunnison and Upper Yampa River Basins for Monday night
into Tuesday morning in what projects to be our coldest night in
a long time. More details on the extreme cold potential beyond
Sunday is in the Long Term discussion below.

On Sunday, another shortwave dives through the area as we still
remain on the backside of the western fringes of this deep
arctic trough, resulting in some scattered light snow showers
particularly over the mountains along the divide. Not expecting
a lot with this wave but temperatures will be plenty cold with
H7 temps still around -20C so SLRs will be higher under this
very cold regime. The Park Range looks to receive another 2 to 4
inches of snow on Sunday while other mountain areas see 1 to 3
or less.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 314 AM MST Sat Jan 18 2025

There has been a slight uptick in the NBM probability of snow
accumulation across the northern and central Colorado mountains
Sunday night as a shortwave trough passes through the region.
This does appear to be a rather dry system, and as a result,
forecasts are calling for little more than 1-4 inches across the
Park Range and likely less everywhere else where flurries do
fall. Instead, as has been a strong focal point in prior
discussions, we`re concerned mostly with the cold temperatures
accompanying this lingering trough. Sunday should experience
somewhat warmer overnight lows than Saturday, though this isn`t
saying a whole lot considering the extent of the frigid pattern.
Temperatures in the Upper Yampa River Basin and Gunnison Valley
are on track for -15 to -25F Sunday night. With this, we have
issued a Cold Weather Advisory for the Gunnison Valley Sunday
night into Monday morning, and the Upper Yampa River Valley
could potentially dip into that criteria should temperatures
trend downwards at all. Purely northern upper-level flow then
settles across the Rockies late Monday, advecting Arctic air
into our CWA. By Tuesday morning we should expect to see
temperatures hit their lowest of this cold spell. Wind chills
are likely to be in the -20 to -40F range for upper valleys,
though some locally colder values are possible as well. An
Extreme Cold Watch has been issued for the Upper Yampa River
Basin and Gunnison Valley Monday night into Tuesday morning as a
result with overnight lows potentially as low as -35F in
Steamboat Springs and -40F in Gunnison by Tuesday morning.

Models are beginning to converge somewhat on the ensuing
pattern beginning Tuesday afternoon as the trough begins to
break down, though ridging seems to remain over the Pacific
Coast for a couple more days, keeping us in relatively weak
north to northwesterly flow. So, the mid-to-late-week warm-up in
temperatures is trending towards being more gradual. Agreement
is minimal among models by Friday, and cluster analysis is
suggesting we will not have even seen the ridge axis pass us by
this point. These details are certainly still up in the air
though, so when (and if) we do expect to see seasonally warmer
weather roll in could change drastically over the coming days.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 936 PM MST Fri Jan 17 2025

Cloud cover has increased over the higher terrain of
northeastern Utah into western Colorado. Ceilings have dropped
below ILS breakpoints at KASE, KEGE, and KRIL, although no
precipitation is occurring at those locations yet. Snow is
occurring at KHDN, who has dropped into MVFR conditions for the
last several hours, visibility reduced to 1 mile at times. This
trend will continue through the next several hours, with KASE
and KEGE also expected to see snow before 12z. Elsewhere, VFR
conditions are expected to prevail, with ceilings remaining
above breakpoints. Gusty southwest winds of 20-30 knots are
expected at KDRO tomorrow afternoon. Skies will gradually clear
through the day tomorrow, with improving conditions.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

CO...Winter Weather Advisory until 5 PM MST this afternoon for
     COZ004-010-013-018.
     Cold Weather Advisory from midnight tonight to 9 AM MST Sunday
     for COZ005.
     Extreme Cold Watch from Monday evening through Tuesday morning
     for COZ005-014.
     Cold Weather Advisory from 10 PM this evening to 11 AM MST
     Sunday for COZ014.
     Cold Weather Advisory from 10 PM Sunday to 11 AM MST Monday
     for COZ014.
     Wind Advisory from 9 AM this morning to 5 PM MST this
     afternoon for COZ021-022.
UT...None.

&&

$$

SHORT TERM...MDA
LONG TERM...BW
AVIATION...TGJT