757
FXUS65 KBOI 031427 CCA
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
727 AM MST Wed Dec 3 2025

...CORRECTED TO REMOVE EXTRA WORDING...

.SHORT TERM...Today through Friday night...The next 24 hours
will see dry and stable conditions over the region as an upper
ridge builds in aloft. With this will come the ebb and flow of
fog and low stratus. For now Satellite and forecast trends
would support the focus of fog/stratus to develop across
portions of the Snake Plain (Boise eastward) and higher terrain
to the south and west. Don`t expect any widespread dense fog and
there is still enough northwest flow aloft to support erosion
of the fog/stratus this afternoon.

Clouds increase tonight and light precipitation will develop
from northwest to southeast on Thursday as deep moisture rides
over the Pacific ridge. Snow levels will start off between
2-3kft MSL, so light snow is possible down to valley floors.
Given the afternoon timing and light intensity, accumulations
will be less than an inch across the region through the
afternoon. The precipitation intensity will pickup across the
mtns Thursday night into Friday as mid-level winds (~10kft MSL)
increase to 30-50 kt. Snow levels will also rise through the
period, more so across SE Oregon where they reach 5-6kft MSL
Friday morning, and 6-8kft by Friday evening. Snow levels are
slower to rise across the w-central Idaho mtns, staying between
4-5kft through Friday, rising to between 5-6kft Friday night.
While this has bumped up deterministic snow amounts for some
higher mtn valley sites like McCall it will only take small
change in the rain/snow elevation to swing snow totals through
the forecast period. This is evident in the NBM snowfall
probability forecasts which carry an 80% chance of 2+ inches at
McCall through Saturday morning, but only 30% chance of 2+
inches at Cascade. Push that threshold up to 4" and the
probabilities drop to 40% and <5% respectively. Sites above
6kft, where it stays all snow, can expect to see 5-10" from
Thursday night through Saturday morning. Liquid (equivalent)
totals will hold under a quarter inch at lower elevations with
widespread 0.4-0.8" amounts in the mountains and locally up to
1" across higher peaks.

.LONG TERM...Saturday through Wednesday...An active pattern will
continue over the extended as the jet stream rides over an upper
level ridge and into the Pacific Northwest. Confidence is high that
this overall pattern will persist through the period. Pacific
moisture and shortwave disturbances will bring periodic rain and
mountain snow to the area. However, confidence in timing and amounts
is lower. This is due to our area being situated on the southern
edge of the storm track. Small changes in the amplitude of the ridge
will have large impacts in our area, with a stronger ridge pushing
systems to our north, and a weaker ridge allowing for widespread and
heavier precipitation amounts to move into our area under strong
westerly flow.

Currently, the highest chance of precipitation is on Saturday (60-
90%), then trends lower (30-70%) on Sunday with the highest chances
in the northern mountains. Snow levels will remain high at around
5000-7000 feet, lowest in the north, resulting in most areas seeing
rain with snow limited to higher peaks. Precipitation amounts over
the weekend should be light to moderate. Temperatures will average
around 10 degrees above normal, and winds will be breezy. Ensembles
are in agreement about the ridge keeping our area mostly dry on
Monday. Uncertainty increases on Tuesday and Wednesday as an
atmospheric river moves into the Pacific Northwest. At least some
moisture is favored to make it into our area (especially across the
north), but how much will be determined by the strength of the
ridge. Mild temperatures will continue, reaching 10-15 degrees above
normal for early to mid December.

&&

.AVIATION... Areas of IFR/LIFR fog/low stratus this morning, mainly
in the Magic Valley and along the Nevada border. Conditions
improving this afternoon. Otherwise, VFR conditions today. Surface
winds: W-NW 5-10 kt. Winds aloft at 10kft MSL: N 10-20 kt.

KBOI...Mainly VFR. A 20% chance of IFR/LIFR fog/low stratus this
morning as winds become light, with a higher chance along the
foothills. Surface winds: light and variable this morning, becoming
NW around 5 kt this afternoon.


&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...None.
OR...None.

&&

$$

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SHORT TERM...DG
LONG TERM....ST
AVIATION.....ST