793
FXUS65 KBOI 160954
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
254 AM MST Thu Jan 16 2025

.SHORT TERM...Today through Saturday night...An inversion will
persist in the lower valleys through this evening as high
pressure remains in place. As a result, temperatures across the
region should stay similar to those on Wednesday. Consequently,
the Air Stagnation Advisory will remain active until early
Friday.

The inversion is expected to weaken significantly on Friday
with the arrival of a cold front moving from north to south.
This front will bring colder Arctic air and stronger surface
winds. Due to the fronts colder and drier origin, precipitation
will be minimal, with the best chance for any snow occurring in
eastern Valley County and the higher elevations of southern
Twin Falls County. However, precipitation chances remain low,
around 20%, with snowfall totals likely under one inch.

Following the front, cold air will settle into the region,
accompanied by northwesterly flow that will persist into next
week. This will result in the coldest temperatures of the winter
so far, particularly in areas with existing snow cover. High
temperatures in the western Snake River Plain on Saturday will
rise just a few degrees above freezing, while Sunday morning
lows will range from the mid-teens to the low 20s. Areas with
significant snow cover, such as the Camas Prairie and Long
Valley, can expect lows ranging from just above zero to as cold
as 10 degrees below zero. Record low temperatures are not
expected as the coldest air looks to remain well east of the
area.

.LONG TERM...Sunday through Thursday...A prolonged period of
below-normal temperatures is expected as northwesterly flow
brings an air mass from the Canadian Arctic. While the coldest
air will remain east of the Rocky Mountains, some cold air is
expected to filter into the mountain valleys. Although
northwesterly flow aloft typically limits cold air infiltration
from the east, there are signs that enough will pass through the
mountains to bring the coldest temperatures of the season to
the region.

Morning lows will drop into the teens for the warmer areas,
such as non-snow-covered valleys, with daytime highs climbing
just above freezing. In contrast, colder mountain valley
locations, like the Camas Prairie, can expect temperatures well
below zero, ranging from -15F to -5F.

These cold conditions will persist until the next shortwave
system moves through late Tuesday into Wednesday. This system
appears strong enough to displace the cold air mass with
increased surface winds. However, like the Friday system, it
originates from a colder, drier region and will bring little
moisture. Temperatures will return closer to seasonal averages
after its passage.

&&

.AVIATION...Mostly VFR under clear skies. Local IFR in mtn-
valley fog especially for KMYL. Surface winds: SE 5-10 kt.
Winds aloft at 10kft MSL: Variable 5-10 kt becoming S and then W
10-25 kt by 12Z/16.

KBOI...VFR. Light SE wind today.

Weekend Outlook...Mostly VFR with clear skies. A few snow showers
Saturday morning across the Central Idaho Mountains. Otherwise,
clear skies. Light north- northwesterly winds.

&&

.AIR STAGNATION...An Air Stagnation Advisory remains in effect
for valleys in SE Oregon and SW Idaho through Friday morning.
Mixing heights 2000 ft AGL or lower, along with light boundary
layer winds, will maintain stagnant conditions. A cold front
along with cold air advection aloft will improve mixing on
Friday afternoon.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Air Stagnation Advisory until 11 AM MST Friday
     IDZ011>016-028>030-033.
OR...Air Stagnation Advisory until 11 AM MST /10 AM PST/ Friday
     ORZ061>064.

&&

$$

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SHORT TERM...JDS
LONG TERM....JDS
AVIATION.....JDS
AIR STAGNATION...SP/JDS