398
FXUS65 KBOI 150409
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
909 PM MST Thu Nov 14 2024

.DISCUSSION...Showers continue to spread across s-central
Oregon, including Harney County, this evening. The showers are
associated with an upper trough near the coast. A closed low
will develop along the base of the trough and track eastward
across northern Nevada on Friday, then turn to the northeast
into southeast Idaho Friday evening. The track of the low will
determine the highest precip totals, which at this time still
appears to be areas near the Nevada border. Snow levels
4000-4500 feet MSL lower to around 3500 feet Friday morning.
Snowfall totals of up to 2 inches with locally 4 inches are
expected along the southern areas near the Nevada border, mainly
in the higher elevations. Northwest winds increase on Friday
and become windy in some areas by the afternoon, including the
Treasure Valley. No updates.

&&

.AVIATION...Mainly VFR. Rain and snow (accompanied by MVFR and
local IFR conditions) expanding into SE Oregon and SW Idaho
tonight through Friday morning. Snow levels 4000-5000 ft MSL
lowering to 3000-4000 ft MSL. Mountain obscuration. Surface
winds: variable less than 10 kt becoming NW 5-15 kt overnight.
Winds aloft at 10kft MSL: S 5-15 kt shifting to E-NE overnight.

KBOI...VFR with increasing clouds. Surface winds: variable less
than 10 kt.

WEEKEND OUTLOOK...Saturday: Lingering low clouds/patchy
mountain valley fog in the morning, then VFR. Surface winds W-NW
5-15 kt, afternoon gusts to 15-25 kt. Sunday: Rain/snow moving
in from NW, becoming widespread by Sun night. MVFR to LIFR in
precip. Surface winds SW-SE 5-15 kt, afternoon gusts 20-25 kt.
Mountain obscuration. Snow levels near valley floors rising to
3500-5500 ft MSL on Sunday.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Saturday night...An upper-level
trough off the Pacific Northwest coast will shift inland
tonight, reaching southeast Oregon by Friday morning and
southwest Idaho by Friday afternoon. This afternoon, convective
showers have developed across much of the area, and this
activity is expected to persist into the evening. Stronger
showers could bring brief episodes of hail or graupel, with
light rain likely below elevations of 5,000 feet. Overnight,
rain will turn to snow, though any accumulations will be light
(around 0.1" to 0.2").

As the trough moves eastward, it will form a closed low over
northeast Nevada and south-central Idaho by Friday afternoon and
evening. A band of moderate precipitation is forecast to
develop on the backside of the system, focusing along the
Idaho/Nevada border. While some models have shifted this band
slightly west and north into the Treasure Valley and Western
Magic Valley, these remain outliers among ensemble forecasts.
Current guidance indicates an 80% chance of 24 inches of
snowfall along the Idaho/Nevada border on Friday, which could
impact travel on higher-elevation portions of US-93 and State
Highway 51. There is also a 60% chance of snow in the Western
Magic Valley Friday afternoon, though surface temperatures above
freezing may prevent snow from sticking.

Cooler, drier conditions are expected Saturday as the region
enters a lull between systems.

LONG TERM...Sunday through Thursday...A deeper trough will
begin to move into the Pacific Northwest on Sunday, with an
initial warm front bringing stratiform precipitation with valley
rain and mountain snow on Sunday afternoon. The trough will
then deepen over the region, bringing cooler air and a chance of
snow in the morning across the lower elevation valleys. Snow
levels will initially be around 3500-4500 feet, but will briefly
lower to around valley floors on Sunday night into Monday
morning. About 30% of ensemble members forecast less than an
inch of snow accumulation in Boise on Monday morning, with about
a tenth of an inch of rain in the valleys by Tuesday. Higher
accumulations are anticipated in the mountains, with McCall, ID
seeing around 4-6 inches and Banner Summit seeing 6- 8 inches by
Tuesday morning.

A deep ridge of high pressure will then begin to build into the
Western US late Tuesday, with widespread model agreement in a shift
to dry conditions with the potential for another air stagnation
event by the end of the week. Below normal temperatures are expected
below the strong inversion in the valleys, however temperatures will
be 5-10 degrees normal in higher terrain above the inversion
layer.

&&

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

&&

$$

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DISCUSSION...BW
AVIATION.....BW
SHORT TERM...JDS
LONG TERM....SA