Grand Junction, Colorado 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

085
FXUS65 KGJT 180440
AFDGJT

Area Forecast Discussion
National Weather Service Grand Junction CO
940 PM MST Fri Jan 17 2025

.KEY MESSAGES...

- A pattern change is upon us as an Arctic front traverses the
  area this evening into Saturday bringing snow and 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.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 155 PM MST Fri Jan 17 2025

Enjoy the last "warmth" that we will see for the next several
days. All eyes are on a trough currently over Wyoming that is
expected to keep tracking southward tonight and early tomorrow.
The trough is brining snow as well as an arctic airmass to the
region with 700mb temperatures tanking to -20C. This will be one
of the coldest air masses we have seen so far this winter. The
Arctic front reaches the CO/WY state line late this afternoon
and quickly passes into New Mexico late tomorrow morning. The
instability ahead of the front is not impressive, but there is a
slight potential for snow squalls along and near the highway 40
corridor this evening. With an even lower chance closer to
I-70. With winds shifting to the north behind the front northern
facing slopes will be favored through this event. The bulk of
the snowfall is expected tonight with perhaps a lull late in the
morning before picking up again in the afternoon. The northern
mountains could get 4-12", while elsewhere 2-8" seems
reasonable. Tomorrow the lapse rates are fairly steep so any
moisture in the atmosphere will result in snow showers. Models
are even showing a modest amount of instability, which could
enhance the snowfall rates in spots. Also, the high-res models
are showing the potential for small-scale banding enhanced by
the terrain. Therefore snow amounts could vary over short
distances depending on if these bands can develop and where they
set up. Snow ratios for this event will no doubt be very high
+20:1 making for an efficient snowfall.

The Arctic air mass takes over the region tonight, but
widespread clouds look to prevent the temperatures from
bottoming out. Although the wind will be breezy due to the
front, so wind chills range from 5F to as low as -25F waking up
tomorrow. Winds gusts tonight and tomorrow could reach 50 mph in
spots. This could lead to blowing snow as well as near white
conditions. The San Juan river valley is typically windy in
these post frontal regimes so expect 30-50 mph gusts in the
afternoon. Highs tomorrow will be well below normal, and the
snow showers should dissipate around sunset. Attention then
turns to Sunday morning. Guidance is showing the potential for a
very cold night for some locations. Clouds will be the deciding
factor. Unfortunately, we will be dealing with left over
moisture from the arctic frontal system and moisture spreading
in from the west thanks to the next system. It appears that some
will experience clear skies, perhaps all night, while some may
have clouds build in closer to sunrise. High snow covered
valleys are looking at lows of
-15F to -30F. Some places could see record values if the
 conditions line up.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 155 PM MST Fri Jan 17 2025

The Arctic airmass remains in place on Sunday through Tuesday
with some of the coldest conditions anticipated during this
stretch. High temperatures are forecast to be 10 to 20+ degrees
below normal on Sunday across western Colorado and 5 to 20
degrees below normal in eastern Utah. A subtle shortwave moves
through Sunday night. This feature could produce enough cloud
cover to insulate much of the forecast area helping moderate low
temperatures overnight. Sunday night lows will still be much
cooler than normal, and if cloud cover does not remain in the
forecast, temperatures will be even cooler. Light, fluffy snow
is also on tap with this weak wave and will favor the mountains.


Once this system passes, cold air advection continues to pull
Arctic air into the region with high temperatures upwards of 25
degrees below normal on Monday. Dangerously cold wind chills
follow suite Monday night into early Tuesday morning in what is
likely to be the coldest period of this cold spell. Wind chills
in western Colorado will almost surely be below zero with
mountain and high valley zones having the potential to see -20
to -40 wind chills with locally cooler values possible (we`re
looking at you Gunnison).

The trough begins to break down late Tuesday into Wednesday
leading to reprieve from the bitter cold. Below normal
temperatures remain in the forecast for the rest of the week but
will moderate away from hazardous levels. Model agreement is
not great beyond Wednesday, but there are signs that upper-level
ridging could return by next weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z 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 Saturday for COZ004-010-
     013.
     Winter Weather Advisory until 5 PM MST Saturday for COZ018.
     Wind Advisory from 9 AM to 5 PM MST Saturday for COZ021-022.
UT...None.

&&

$$

SHORT TERM...KJS
LONG TERM...KAA
AVIATION...TGJT