Orem, Utah 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

057
FXUS65 KSLC 240958
AFDSLC

Area Forecast Discussion
National Weather Service Salt Lake City UT
258 AM MST Sun Nov 24 2024

.SYNOPSIS...A cold front will continue to move across the region
today. High pressure will bring a temporary drying trend tonight
into the day Monday, before a moisture-rich storm system makes
its way across the area late Monday through Wednesday.

&&

.SHORT TERM (Through 12Z/5AM Tuesday)...A low level baroclinic
zone continues to slowly push southeast across northern and west
central Utah early this morning. An upstream shortwave trough
spreading into the western Great Basin is inducing frontogenesis
along this boundary resulting in a broad band of precipitation. A
mesoscale circulation evident in radar imagery is riding along
this boundary, which kept the band confined to the northern
Wasatch Front and adjacent areas earlier. However in the last hour
this wave has finally lifting through the Wasatch Front allowing
the boundary to begin accelerating southward in its wake. As such,
this precipitation band will push through the central and
southern Wasatch Front as well as west central Utah through mid-
morning, eventually weakening midday as it reaches southwest Utah,
and the progressive shortwave begins to pull away from the area.

Colder air has been slow to spill into northern Utah likely owing
to this meso-low passage, with overnight RAP analysis as of 08Z
showing the -7C 700mb isotherm just now reaching a line from Logan
to Wendover. As such, although precipitation intensity may
temporarily drive snow levels to the valley floors, the evolution
is trending toward most valley floors remaining rain through the
majority of the event with any changeover to snow coming as the
precip is winding down with little if any valley accumulation
expected. This is supported by HRRR and 3-km nam bufr soundings
from points along the Wasatch Front. Benches above 4500 feet are
currently transitioning over to snow and will likely see
accumulations in the 1-3 inch range.

With precipitation largely remaining confined to the baroclinic
zone and limited post-frontal orographic enhancement, mountain
snowfall totals in the 5-10 inch range still look on track across
the northern/central mountains, with locally higher amounts where
higher intensity or longer residence time allows.

In the wake of today`s trough, shortwave ridging will quickly
build across the forecast area overnight into Monday morning. The
associated subsidence with this building ridge will result in
clearing skies, with a chance for late night/early morning
fog/stratus within sheltered areas given today`s precipitation.
Hi-res guidance is more bullish with this potential across west
central and southwest Utah, but less so across northern valleys
such as the Cache, Heber, and areas near the GSL.

This ridge will dampen in amplitude as it translates east later
Monday into Monday night, as a plume of warm air/moisture
advection quickly spreads into the southern Great Basin. This
plume is along the leading edge of the next AR making landfall
along the California coast. This moisture/lift will spread from
southwest to northeast across the forecast area late Monday
afternoon though Monday night, and serve as the beginning of a
prolonged window of precipitation extending into the long term
period (addressed below). Given the mild origins of the incoming
airmass, snow levels will rise to above 8000 feet across southern
Utah by late Monday, and rise above 6000-6500 feet across the
north Monday night, yielding a period of valley rain and mountain
snow.

.LONG TERM (After 12Z/5AM Tuesday)...A moisture-rich storm system
will impact Utah and southwest Wyoming in the days leading up to
Thanksgiving with heavy and wet mountain snow and substantial valley
rain. Those with travel plans over mountain passes should be
prepared for potential travel difficulties.

The extended period opens with broad west to southwest flow across
the Great Basin ahead of a closed low swinging inland from Oregon.
Remnants of an inland-penetrating atmospheric river will have
reached southern Utah by early Tuesday as the moisture tap wraps
around the southern end of the Sierra Nevada and overspreads the
entire forecast area. The GEFS and EPS ensembles feature a 90%
chance of moisture transport reaching the AR definition threshold
(250 kg/ms), something that usually only happens a few times/winter
in that area. As is typical with atmospheric rivers, snow levels
will remain on the high side, though it is worth noting that some
colder air will linger farther north, and will need to be watched in
case an overrunning situation develops for a few northern mountain
valleys such as the Ogden Valley (low chance at this time). Mean
snow levels are currently forecast to range from 9kft+ over the
southern Utah mountains to around 6kft near the Idaho border.
Terrain favored in SW to WSW flow regimes will do quite well during
this period due to high moisture availability.

The earlier-mentioned low in Oregon will swing southeastward,
reaching Utah roughly late Tuesday into Wednesday and pushing a cold
front through the area. Recent ensembles have come into better
agreement on the timing and track of the low up to Tuesday night.
The main uncertainty at this point is in how quickly the low sweeps
through our area Wednesday and consequently how soon precipitation
ends as colder air moves in. The deterministic GFS gives an example
of what could happen with a slower track, allowing for a greater
chance of valley snow with precipitation lingering through the day
Wednesday under northwest flow. The deterministic ECMWF on the other
hand shows what could happen with a quicker track, with drier air
and subtle ridging overhead by mid-day Wendesday effectively ending
the precipitation for most of the state. Either way, behind the
frontal passage, 700MB temperatures range from are likely to drop to
around -8C to -12C supporting snow to valley floors, again with the
colder temperatures over northern Utah and southwest Wyoming. Light
valley snow is thus possible Wednesday if the slower solutions
verify. Thanksgiving itself will be dry but below normal.

Liquid-equivalent totals for the event are currently ranging 0.5-1"
in most valleys in the NBM 25th-75th percentiles, with 1-2.5" in the
mountains. As mentioned above, any terrain favored in southwesterly
to westerly flow (such as the Provo Canyon vicinity) is likely to
verify on the high end of that forecast range. It`s also worth
noting that the ECMWF Extreme Forecast Index (EFI) is currently
strongly highlighting the central mountains for abnormally high 24-
hour QPF and snow in particular, while the majority of
central/northern Utah and southwest Wyoming are showing anomalously
high QPF as well. Wet heavy snow in the mountains could have other
implications besides travel impacts too.

Finally, the pattern Thanksgiving onward turns drier as a ridge
builds over the West Coast. This time of year, this means there is a
chance for valley inversions to develop given lower sun angle this
time of year. That said, the northern branch of the jet stream is
forecasted to remain just to our north and east, suggesting that
weak shortwave troughs embedded in the resultant northwest flow
could still impact our area and provide potential mixing. Current
ensemble cluster analysis shows that roughly a third of the solution
space features a ridge axis far enough west for our area to brush
our area with a few shortwaves, while the remaining 2/3rds are less
optimistic and bring stronger ridging over our area.

&&

.AVIATION...KSLC...A cold front will bring a likely transition from
rain to snow overnight between 9 and 11Z, along with ceilings
lowering to MVFR and approaching IFR conditions through mid morning.
Snow and rain showers will then taper off through late morning, with
conditions improving to mostly VFR but with continued sub-7kft
ceilings. Fully VFR conditions with clearing skies can then be
expected by the afternoon. Winds will be remain northwesterly
through much of the period and mostly below 10kts, before turning
southeasterly in the early evening.

.REST OF UTAH AND SOUTHWEST WYOMING...Gusty winds from the southeast
to southwest will continue for central and southern Utah today ahead
of a cold front moving northwest to southeast. Areas near or behind
the front will see widespread precipitation with MVFR to IFR
conditions due to lowered ceilings/visibilities. Lowest conditions
can be expected with a transition to snow to most valley floors by
daybreak, with potential LIFR conditions. Precipitation will become
less intense as the front moves southeastward, with only a 50/50
chance of snow reaching KCDC late today. Ahead of the front over
southern and eastern Utah today, VFR conditions will prevail.

&&

.SLC WATCHES/WARNINGS/ADVISORIES...
UT...Winter Weather Advisory until 5 PM MST this afternoon for
     UTZ110>113-117.

WY...Winter Weather Advisory until 11 AM MST this morning for WYZ021.

&&

$$

Seaman/Van Cleave

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