FXUS65 KBOI 102131
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
231 PM MST Mon Feb 10 2025

.SHORT TERM...Tonight through Wednesday night...Very cold weather
tonight through Thursday morning, dangerously cold in the Camas
Prairie where an Extreme Cold Warning is in effect. All other
zones in southeast Oregon and southwest Idaho will be under a
Cold Weather Advisory. An arctic front in western Canada,
supported by an upper level trough, will move southward into
our CWA tonight accompanied by a few light snow showers or
flurries in the mountains. Skies will clear from the north
overnight and then true arctic air will come in. This will be
an impactful event. Latest models move a 1050 mb surface high
southward from the Yukon Tuesday, and into eastern WA and OR
and western ID later Tuesday through Wednesday. It is rare to
see this happen so late in the season west of the Continental
Divide, but it will under strong northerly flow aloft from the
north pole. The coldest period should be early Wednesday morning
when zero to 15 below zero temps will be widespread in eastern
OR, zero to 10 above in the Treasure and Magic Valleys, 5 below
to 20 below in the Idaho mountains, and as low as 30 below in
the Camas Prairie. Thursday morning will be almost as cold as
Wednesday on the Idaho side, but beginning to moderate in Oregon
as winds aloft change to moist and warmer westerly and clouds
increase from the Pacific. During the arctic event skies will be
mostly clear, but patchy dense fog will form in the valleys of
eastern Oregon during the late night and early morning hours.

.LONG TERM...Thursday through Monday...The potential for impactful
snowfall across the forecast area remains on track for Thursday,
marking a return to an active weather pattern. The overall track
of this Pacific storm system remains consistent, though the
latest guidance now suggests the shortwave will move through
earlier, between noon Thursday and midnight Friday. While
precipitation forecasts have slightly increased, expected
snowfall amounts remain largely unchanged. Most of the Snake
River Plain has a 40% to 90% chance of accumulating at least
2 inches of snow, with the highest probabilities in the Lower
Treasure Valley. Mountain snowfall is expected to be relatively
light, with 3 to 6 inches forecast, as orographic effects will
be minimal due to the system’s rapid progression. This is
reflected in the lower probabilities (10%-40%) for snowfall
greater than 4 inches across the region. Additional snowfall
is likely (at least a 50% chance) on Friday as the upper-level
trough moves through. While amounts will generally be lower,
valleys could receive an additional 0.5 inches, with 2 inches
possible in the mountains. Confidence has increased in the
likelihood of snowfall impacting both the Thursday evening and
Friday morning commutes.

A brief break in precipitation is expected on Saturday before a
weaker and warmer system arrives Sunday into Monday. This system
will bring milder Pacific air ahead of an advancing cold front,
though with significantly less precipitation than its predecessor.
Precipitation is forecast to begin as a mix of rain and snow below
4,000 feet before transitioning to rain by Sunday afternoon.
Temperatures will gradually moderate, reaching 5-10 degrees below
normal by the weekend.

&&

.AVIATION...Mostly VFR. Widespread mountain obscuration across
parts of southeast Oregon the West Central Mountains through
this evening. Fog/Stratus redeveloping after sunset in sheltered
valleys. KBNO, KBKE and KMYL have the best chance (60% chance)
for Fog tonight. Surface winds: variable up to 10 kt. Winds
aloft at 10kft MSL: W-NW 10-20 kt.

KBOI...VFR. Mostly clear. Stratus/fog possible Tuesday morning,
with a 30% chance of occurrence. Surface Winds: Northwest 5-10
kt.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Cold Weather Advisory until 10 AM MST Thursday
     IDZ011>016-029-030-033.
     Extreme Cold Warning until 10 AM MST Thursday IDZ028.
OR...Cold Weather Advisory until 10 AM MST /9 AM PST/ Thursday
     ORZ061>064.

&&

$$

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SHORT TERM...LC
LONG TERM....JDS
AVIATION.....JDS