Emmett Weather

649
FXUS65 KBOI 102135
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
235 PM MST Tue Dec 10 2024

.SHORT TERM...Tonight through Thursday night...The low clouds
are stubborn to erode in the Treasure Valley this afternoon,
but there has been some clearing on the edges - especially
where the clouds are shallow, including near Mountain Home. The
upper ridge will continue to support the low clouds through
Wednesday. There is a 30 to 50 percent chance of dense fog
redeveloping in the Treasure Valley this evening, and thus
another Dense Fog Advisory may be warranted. However, confidence
is too low to issue one at this time but will be monitored for
trends. Flurries remain possible as well, which could accumulate
on roads and cause localized slick conditions tonight.

The main concern through the period is the progression and
possible snowfall associated with an upper trough on Thursday.
The bulk of the models have trended further south with the
`splitting` system taking the bulk of it into Nevada. Most of
the guidance is projecting little to no snowfall for the valleys
and only light accumulations in the mountains (mainly near the
Nevada border). However, even a light dusting of snowfall (less
than a half inch) could result in a slick morning commute with
morning temperatures in the 20s. A couple models support greater
than a half inch of snowfall in the Treasure Valley, but the
chance of that occurring is less than 20 percent. A Winter
Weather Advisory may be warranted, but confidence is too low at
this time.

.LONG TERM...Friday through Tuesday...A weak ridge will rebuild
into the region on Friday with the potential for light mountain
snow showers through the day. Otherwise, the region will be
mostly dry and cloudy with near normal temperatures.

A low off the PacNW coast will then advect moisture into the
region, with upper level southwest flow bringing breezy winds
and snow showers to southeast Oregon early Saturday morning.
Rain will move into the Treasure Valley by mid morning, with a
low chance of a brief rain-snow mix early. Widespread
disagreement exists in ensemble solutions on the precipitation
totals for this system. However, snow levels look to be around
3000-4000 feet on Saturday morning, rising to 4000-5000 feet by
the afternoon. Therefore, rain will be the main precipitation
type for the Treasure Valley, with higher snowfall totals over
the Central ID Mountains since southwest flow will shadow much
of the Snake River valley.

There is further disagreement in deterministic solutions on the
pattern at the beginning of next week, with differing timing
and intensity of another shortwave trough on Monday-Tuesday.
Cluster solutions seem to agree on a deep ridge building back in
by mid-week, with a potential return to air stagnation over
lower elevation valleys and an inversion. Forecast uncertainty
remains high Sunday-Tuesday, with a slight chance of showers
with cooler temperatures in the forecast through the end of the
long term period.

&&

.AVIATION...Areas of low stratus lingering in the Snake River
Valley creating LIFR/VLIFR conditions through the night. Low
clouds in the upper Snake Plain seem likely to stay north of
KJER, but may move into the vicinity at times. Dense fog and low
stratus will redevelop and expand into the Treasure Valley
through Wednesday morning. Mountains obscured in low clouds.
Surface winds: variable and light with W-NW 10-15 kt in the
Magic Valley this afternoon. Winds aloft at 10kft MSL: W-NW
10-20 kt.

KBOI...LIFR/VLIFR in low stratus this afternoon, with some
brief periods of improvement before dense fog redevelops tonight
by 11/02Z. Surface winds are light and variable.

&&

.AIR STAGNATION...The inversion is expected to weaken somewhat
on Thursday due to increased winds in some elevated areas, but
will likely remain in places in the lower valleys - including
the Treasure Valley. The Air Stagnation Advisory remains in
effect through early Thursday afternoon, but may need to be
extended in some areas into Friday. There is a greater chance
for the removal of the inversion this weekend as a moist upper
trough moves through the region.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Air Stagnation Advisory until 2 PM MST Thursday
     IDZ011>014-028-029-033.
OR...Air Stagnation Advisory until 2 PM MST /1 PM PST/ Thursday
     ORZ061>064.

&&

$$

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SHORT TERM...BW
LONG TERM....SA
AVIATION.....SA
AIR STAGNATION...BW