Wind Advisory 3, NWS Boise, ID

Area Forecast Discussion
National Weather Service Boise ID
937 PM MST Wed Feb 5 2025

.DISCUSSION...Light snow showers will continue overnight, mainly
over the mountains. A trough off the CA coast will move inland
late Thursday, with snow developing across eastern OR during the
late afternoon and southwest Idaho around midnight on Friday
morning. The system is trending farther north and west with the
past few runs which would focus the heaviest precipitation
across central and eastern OR, with light amounts in southwest
Idaho. The center of the trough is forecast to move across
eastern OR toward McCall by midday Friday, which would keep
precipitation shadowing and strong southwest flow aloft over the
Idaho zones until the system passes. This set up does not favor
much snow in the Treasure or Magic Valley, with generally less
than an inch. To the northwest of the center of the system,
precipitation will be heavier across eastern OR. After the
center of the trough passes northeast, wrap around moisture will
cause snow showers to form over the central ID mountains and
possibly Boise. Windy conditions expected on Friday afternoon
with west- northwest winds 25-35 mph with gusts up to 45 mph
possible. No updates to the forecast.

&&

.AVIATION...Mainly VFR. Isolated snow showers creating MVFR/IFR for
northeast OR and w-central ID. Precipitation becoming widespread
late Thurs, with snow levels at/near valley floors. Mountain
obscuration. Surface winds: SE-SW 5-15 kt. Winds aloft at 10kft MSL:
SW-W 20-30 kt.

KBOI...VFR. A 10% chance of light snow or flurries at terminal
overnight. Surface winds: E-SE 5-15 kt.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Friday night...The primary focus
remains on the approaching Pacific storm system, set to bring
snow from Thursday evening into Friday. This system has the
potential to impact the Friday morning commute, particularly
north of a Burns-Ontario-Stanley line.

This afternoon, mostly clear skies persist between systems.
However, a weak shortwave currently moving inland across
Washington and Oregon will continue eastward, bringing a 30%
chance of light snow showers, mainly affecting Baker County and
the West Central Mountains of Idaho. A slight chance (15%) of
snow showers exists for the Lower Treasure Valley between 5 PM
and midnight, though no accumulations are expected.

The next storm system is forecast to arrive Thursday evening
into Friday. Recent guidance maintains the trend of a warm front
lifting northward early Friday, concentrating most
precipitation north of the front by mid-morning. This setup
favors light to moderate snowfall potential along and north of a
Burns-Ontario-Stanley line. However, the latest guidance favors
a further northward shift of the warm front, reducing expected
snowfall amounts from the Upper Treasure Valley through the
Western Magic Valley, Owyhee Mountains, and southern Highlands.
The combination of a quicker warm frontal passage, lower QPF
totals, and a strong low-level jet (50-75 kt) supporting warmer
surface temperatures has decreased snowfall probabilities for
the above-mentioned areas. Probabilistic guidance from both the
NBM and HREF now suggests only a 30% chance of snowfall
exceeding 1 inch in these areas.

Given this downward trend in snowfall expectations over the
past two model cycles, no winter weather headlines have been
issued at this time. Currently, we have 1 to 2 inches along
US-20 from Burns to Ontario, the I-84 corridor from Ontario to
Baker City, and US-95 from Ontario to Council and 4 to 6 inches
in mountain valleys, with up to 10 inches at higher elevations.
Up to half an inch in the Upper Treasure Valley, though
accumulation on road surfaces may be limited due to above-
freezing temperatures. Following the cold frontal passage,
strong winds could develop across south-central Idaho on Friday,
with a 30% chance of reaching wind advisory criteria.

Snow will taper off Friday evening as the cold front moves
through, with colder temperatures possible depending on
lingering snow cover and the establishment of northerly flow
across the region.

LONG TERM...Saturday through Wednesday...An upper level
trough will reside over the region Saturday through early next week
with shortwave troughs embedded in the flow. This will keep a cold
northwest flow over the area resulting in well below normal
temperatures. Northern mountain areas will have about a 20-30%
chance of snow each day in this pattern with dry conditions
prevailing elsewhere. By the middle of next week the models are less
consistent with some showing the upper level pattern shifting to a
more active westerly flow off the Pacific. Lots of uncertainty that
far out. The forecast will reflect a slight upward trend in
temperatures by the middle of next week with increased chances of
precipitation/snow as below normal temperatures continue.

&&

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

&&

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DISCUSSION...KA
AVIATION.....SH
SHORT TERM...JDS
LONG TERM....TL