852
FXUS65 KBOI 152145
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
245 PM MST Mon Dec 15 2025

.SHORT TERM...Tonight through Wednesday night...At 2 PM MST a
weak cold front was in western ID with a band of light rain
extending north-south along the OR/ID border. The front was
moving steadily east with slightly more pcpn than models
predicted but should total less than .15 inch even in the
wettest locations. The front will stir up the stagnant air
but not enough to end the Air Stagnation Advisory which will
continue until 5 AM Tuesday. Clouds and light winds will
moderate low temps tonight, and increasing southeast winds
will boost max temps to near record highs Tuesday. Tuesday
night will be windy and very mild ahead of a very strong
Pacific cold front due in the pre-dawn hours Wednesday in OR,
and early Wednesday morning in western ID. South/southeast
winds will shift abruptly to west/northwest as the front passes
and increase to 30 to 40 mph with possible gusts as high as 60
mph in southern zones. A High Wind Watch has been issued in
those zones (listed below) for Wednesday morning in OR and
through 2 PM MST Wednesday afternoon in western ID. Strongest
winds are expected in the western Magic Valley and Camas
Prairie. Pcpn will be heavier with the strong cold front with
greatest amounts (near 1.00 inch) in eastern Valley County and
northern Elmore County in ID late Tuesday night through late
Wednesday night. Heaviest pcpn will fall as the cold front
passes and may result in rock slides in steep terrain. Travelers
would be wise to avoid the Banks-Lowman road in ID and be wary
on ID state highway 21 northeast of Idaho City. The rest of ID
north of the Snake Basin should have .25 to .50 inch liquid
equivalent, while southern areas including the Snake Basin
receive .10 to .25 inch, with similar amounts in eastern OR. The
snow level will lower rapidly to valley floors later Wednesday
in northern zones and to near 5000 feet in southern zones.
Snowfall 3 to 6 inches is expected in the higher ID mountains
late Wednesday through Wednesday evening. Wednesday night
should be calming, drying, and significantly cooling.

.LONG TERM...Thursday through Monday...Precipitation chances
continue through the extended, with a hefty push during Thursday,
Friday, and early Saturday. This comes as another atmospheric river
event impacts the Pacific NW from an elongated disturbance, courtesy
of the Gulf of Alaska low. A strong, westerly mid-level jet will
accompany this disturbance. As a result, this system will pull
in a long fetch of considerable subtropical moisture, spreading
moderate/heavy precipitation into the area. Snow levels will
oscillate quite a bit during this period, associated with the
tight temperature gradient, making snowfall accumulations a
significant forecast challenge during this period. Overall,
snow levels are expected to be lowest across the north,
gradually rising from south to north throughout the day
Thursday. Snow levels will then gradually lower from north
to south as a cold front moves in late Friday/early Saturday.
Overall, mountains could see 1 to 2 inches of liquid equivalent
throughout this period, along with snowfall totals 1 to 2 feet
at the ridgetops (depending heavily on the snow level). The
period of rainfall over saturated, steep terrain will also
introduce rockslide concerns.

In addition to precipitation, strong surface winds are expected
to develop across much of the area, particularly Friday, ahead
of/along the cold front. Gusts will be strongest across southeast
Oregon, the ID/NV border, and the mountains of southwest Idaho.
Meanwhile, temperatures are forecast to stay above normal
Thursday and Friday, with the coldest air expected across
west-central/central Idaho and eastern Oregon.

Once the aforementioned system exits, there will be a brief
respite from precipitation late Saturday into Sunday morning.
This will occur before yet another push of precipitation comes
ahead of a upper-level long wave trough slowly moving inland
Sunday and Monday. Models currently disagree on how much of the
polar air to the north will penetrate E Oregon and SW Idaho,
resulting in poor forecast confidence on temperatures and snow
levels this far out. Regardless, ample moisture will yield a
new round of notable precipitation amounts for the area, with
upslope flow favoring the mountains of west-central/central
Idaho once again.

&&

.AVIATION...Periods of MVFR in precipitation/low ceilings.
Scattered showers will move from NW to SE today, decreasing by
Tuesday AM. Snow levels 7-9 kft MSL falling to 6-8 kft MSL by
Tuesday AM. Mountains obscured. Periods of LLWS in E Oregon Monday
into Tuesday. Surface winds: light/variable, then SW-SE 5-15 kt
this PM. Gusts of 20-25 kt in SE Oregon and near NV/ID border.
Winds aloft at 10kft MSL: W 25-45 kt.

KBOI...VFR. A 15-30% chance of light rain this afternoon and
evening. Surface winds: SE 4-9 kt

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Air Stagnation Advisory until 5 AM MST Tuesday
     IDZ011>014-016-028-033.
     High Wind Watch from late Tuesday night through Wednesday
     afternoon IDZ012-014>016-028>030.
OR...Air Stagnation Advisory until 5 AM MST /4 AM PST/ Tuesday
     ORZ061>064.
     High Wind Watch from late Tuesday night through Wednesday
     afternoon ORZ064.
     High Wind Watch from late Tuesday night through Wednesday
     morning ORZ061>063.

&&

$$

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SHORT TERM...LC
LONG TERM....CH
AVIATION.....CH