305
FXUS65 KGJT 161118
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
418 AM MST Thu Jan 16 2025

.KEY MESSAGES...

- Slightly milder conditions will occur today as high pressure
  builds over the area. The exception will continue to be the
  high snow covered valleys where cold air remains trapped and
  cold temperatures will persist.

- Changes arrive by the weekend as an arctic front dives
  through area Friday evening into Saturday and spreads snow and
  cold back into the forecast.

- 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 will end up well below normal. Overnight lows have a high
  probability of dropping well below zero in many mountain and
  high valley/basin areas.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 148 AM MST Thu Jan 16 2025

A cut off low to our southwest situated off the SoCal coastline
will nudge a shortwave ridge of high pressure over the region
today, but also act to flatten the broad Pacific ridge that was
previously in place. We will see a little bit of WAA with this
shortwave ridge and return to southwest flow, although it will
be short-lived as an arctic airmass looms to our north and
starts its trek southward by Friday. The cut off low will pass
to our south tonight, relatively unnoticed aside from a few
clouds with the flow shifting to northwest Friday ahead of the
deep trough making its way southward across much of the CONUS.
We are on the western fringe of this trough with the arctic
front positioned across the north by late Friday.

So today`s highs look to be a shade higher than yesterday,
maybe by about 5 degrees or less. This is pretty weak WAA but
with plenty of sunshine due to drier air, it could feel a little
milder during the afternoon. The exception to this continues to
be the cold pools and snow covered high valleys, particularly
Gunnison and Steamboat Springs where deep inversions remain
unfazed by any sort of WAA aloft. Stuck with persistence in
these cold deeply inverted basins and tried to blend with the
5th percentile of guidance today and Friday, which may not be
cold enough...so nudged it down a bit further than that. Either
way, these inversions in Gunnison and to a lesser extent
Steamboat Springs do not appear to break anytime soon. The
arctic plunge expected this weekend into next week will only
bring colder air and help reinforce these strong inversions, so
tried to reflect this through the 7 day forecast for both highs
and lows.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 148 AM MST Thu Jan 16 2025

The next trough will be on our doorstep at the start of the
long term period and while some accumulating snow is expected,
the bitterly cold temperatures is what we`re focusing on. Late
Friday night into Saturday, an arctic front will drop down from
the north and as it does so, bring some light snow to the
northern and central mountains and Flat Tops. As of now, amounts
are ranging from about 2 to 5 inches with some higher amounts
for the highest peaks of the Park Range. The central mountains
will see anywhere from 1 to 3 inches. Nothing too exciting. What
is exciting is the much colder air that will be behind the
arctic front. H7 temperatures early Friday evening will reach
around -3C down south and -9C for the northern valleys. H7
temperatures the same time Saturday evening will drop to -11C
south and -20C up north. Highs for the northern valleys
Saturday will only reach the low to mid teens which is about 20
degrees below seasonal highs. Temps will also drop for the
central and southern valleys, just not as much as the coldest
air will remain over the northern valleys and the Front Range.
Overnight lows will be in the low teens/single digits for many
areas though the northern valleys near Craig, heading into
Steamboat Springs and the Gunnison area will likely see the
coldest temps...possibly dropping to -20F if not colder.

Pieces of energy will continue to move through the mean flow
Sunday and again on Monday bringing some light snowshowers to
the areas mentioned above. A second reinforcing shot of cold air
is progged to move through Monday bringing another round of
cold air to the region. Suffice to say, this stretch of cold air
(Saturday through Tuesday) will bring the coldest temps we`ve
seen so far this season. This also doesn`t factor in any wind
chills and with temperatures like these, any wind will make
temperatures feel even colder. With that in mind, Cold Weather
Advisories and Warnings may be needed for some locations. Please
keep any eye on the latest forecasts as we get closer to this
event.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 418 AM MST Thu Jan 16 2025

VFR conditions will prevail over the next 24 hours under clear
skies with light, terrain driven winds. Although strong drainage
winds will occur at KHDN up to 20kts through around 16Z.

&&

.GJT WATCHES/WARNINGS/ADVISORIES...

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

&&

$$

SHORT TERM...MDA
LONG TERM...TGR
AVIATION...TGJT