Spanish Fork, Utah 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

435
FXUS65 KSLC 161025
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
325 AM MST Tue Dec 16 2025

.KEY MESSAGES...

- A landfalling atmospheric river will bring a long duration
  period of valley rain and mountain snow from Wednesday on into
  the upcoming weekend.

- Strong, gusty winds are expected Wednesday particularly across Uinta
  County, WY and high northern terrain. A High Wind Watch has
  been issued for Uinta County, WY Wednesday for potential gusts
  in excess of 60 mph.

&&

.SHORT TERM (Through 12Z/5AM Friday)...The first indications of a
pattern shift are underway tonight as GOES-W mid level water
vapor loop and corresponding nighttime microphysics RGB show
evidence of increased moisture/cloud cover shifting in with a
landfalling atmospheric river. While a low end shower chance is
noted near the ID border through the day, elsewhere Tuesday
largely does not appear to have sensible weather too different
from prior days. Temperatures will remain mild, with highs around
10F to 20F above seasonal normal for mid December.

Strong Pacific jet will increase its influence further inland
Tuesday night through Wednesday. Aside from precipitation,
strengthened winds are noted especially during the day Wednesday,
especially for the northern portions (and higher elevations) of
the forecast region. These winds will start to increase after
sunrise, become maximized late morning through the afternoon ahead
of a frontal boundary, and then decrease in the evening following
its passage. High resolution guidance in particular highlights
potential for gusts in excess of 60 mph for SW WY, and a High Wind
Watch has been issued accordingly. Some higher elevation ridgetop
locations may also see periods of gusts in excess of 80 mph.
Elsewhere across northern UT it also appears conditions could get
pretty gusty ahead of this front as well. High resolution
guidance shows widespread gusts in the 30 to 45 mph range
developing, with some localized areas of 50+ mph noted especially
downsloping off of terrain features. Did not quite have the
confidence/certainty to issue a Wind Advisory with this package
yet.

The first wave of stronger precipitation will come courtesy of an
embedded mid level impulse and jet max through Wednesday, likely
maximized along the aforementioned baroclinic zone. Overall,
forecast thinking has not changed significantly. It still appears
snow levels will start above 8500 ft, and that the bulk of
precipitation will fall on the warm side of the front. Moisture
will start to scour out quickly as post frontal cold air advection
increases, and while snow levels will likely drop below 5000 ft
into Wednesday night, precipitation potential will quickly be
waning. Wouldn`t at all be surprised to see some flakes mix in
before it wraps up, but low elevation measurable snow doesn`t
appear to likely still (maybe ~5-15% chance of more than 0.1",
with best odds on benches or in the Cache). Accumulating snow will
more likely be in the mountains, with northern mountain water
amounts around 0.30" to 0.80", with locally up to around 1.00" or
so. The mild nature of the system and high snow levels will
generally result in dense snow though, with snow:liquid ratios
around 6:1 to 8:1 or so before the colder air arrives. Best
chances of 2"+ are noted in the upper Cottonwoods and Bear River
Range, with decent odds 4-6"+ in portions of the high Uintas.

While a relative lull is expected into Thursday morning, the
pattern will quickly support a return to unsettled conditions. The
remnant baroclinic zone will start to lift back out with a quick
return to lower level warm air advection along with moisture. Snow
levels will quickly rebound upward as precipitation chances
increase through the day, back up to around 7500-8500 ft by
Thursday night. Best moisture looks to be confined nearer the ID
border where snow levels may remain a bit lower, so this period
may see a bit more in the way of snow accumulation for the Bear
River Range... but elsewhere in the high northern terrain it looks
more like T-2" or so at best.

.LONG TERM (After 12Z/5AM Friday)...Another atmospheric river event
will track into the PacNW Thursday. Through much of Friday,
southwest Wyoming and Utah will be between the exiting and
incoming storm systems. Upslope orographics and weak forcing will
allow for northern mountain snow showers above 7000 feet much of
Friday. Also between systems, similar to Wednesday ahead of that
atmospheric river, winds will be enhanced. South the southwest
winds will be maximized on northern mountain ridgelines and
throughout southwest Wyoming.

There is good agreement with models and ensembles that the jet
associated with abundant moisture advection will slide southward
through Friday, with increasing moisture advection and better
forcing pushing into southwest Wyoming and northern Utah Friday
into Saturday. Snow levels will start around 7000 feet near the
Idaho border and 8000 feet for the Cottonwoods. Snow levels will
increase and decrease some, but stay consistent through the event,
as the main forcing will be the zonal jet. This will transport
abundant moisture, bringing moderate to heavy mountain snow. Snow
ratios will be low through the event, ranging from 5-10:1 for the
northern mountains, with the greatest ratios for the Bear River
Range. Water content will generally range from 0.5-1.0" for the
western Uinta Mountains and Cottonwoods, with 0.75-1.5" for the
Bear River Range. There will be a big range of snowfall totals,
with totals likely exceeding 1 foot for ridgelines near the Idaho
border. There will be a decreasing trend from north to south.

Moisture advection will diminish later Saturday as the forcing
and moisture lift out of the region, but valley rain and mountain
snow showers will continue for southwest Wyoming and northern
Utah. Temperatures from Friday into next week will be warmer than
normal, with valley highs in the 50s for most locations.

For the end of the weekend into next week, there is good
agreement on another atmospheric river event into the western U.S.
Models generally have the track of this storm system more
southward from the previous. There would be enhanced southwest
flow ahead of it, with the better moisture surge north and west of
Utah. The track would lead to more downslope orographics to the
west from the Sierra Nevada Mountains, so a significant mountain
snow event is not anticipated through the start of the week.

&&

.AVIATION...KSLC...There is a 10-20% chance for fog that would build
in from the north from 12-15Z that would be capable of MVFR or
lower conditions. Scattered clouds in VFR range will transition to
broken clouds around 20Z. Light southeast winds will last through
20Z when winds transition to light northwest.

REST OF UTAH AND SOUTHWEST WYOMING...Valley inversion conditions
will allow fog or low clouds in MVFR range or lower, particularly
for KLGU. Clouds will build from the northwest through the day,
with scattered clouds transitioning to broken throughout southwest
Wyoming and northern Utah from 15-21Z. Winds will be relatively
light throughout Utah, with southwest gusts around 20 knots for
southwest Wyoming.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...None.
WY...High Wind Watch from late tonight through Wednesday evening for
     WYZ021.

&&

$$

SHORT TERM...Warthen
LONG TERM...Wilson
AVIATION...Wilson

For more information from NOAA`s National Weather Service visit...
http://weather.gov/saltlakecity