414
FXUS65 KBOI 231717
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
1017 AM MST Sun Feb 23 2025

.DISCUSSION...Rain and high elevation snow will continue
through the day. There will some breaks in the precipitation,
mostly across SE Oregon and lower elevations of SW Idaho, while
mtns see a steady rain/snow. Snow levels have risen around 6kft
across SE Oregon and western portions of the Boise mtns and
West Central ID mtns this morning, to include ridgelines
defining the Long Valley. Cold air is still holding on further
east where it`s snowing in the Camas Prairie (~5kft MSL). All
areas will see snow levels rise through the day reaching
6500-8500 feet MSL by this evening.

Those with interests near rivers, streams and creeks should
monitor conditions and river flow forecasts from the NWRFC as
the hydrologic response to the rain/runoff and snow melt will
likely peak over the next 24-48 hours.

&&

.AVIATION...Widespread MVFR/IFR in rain showers today, with
precipitation decreasing by Mon/15Z for most of the region. Snow
levels will be high, around 6500-7500 feet MSL. Mountains
obscured. Areas of low level wind shear, mainly over KBNO.
Surface winds: becoming SW-SE 10-25 kt with gusts to 35 kt near
the NV border and over ridgetops. Winds aloft at 10kft MSL:
SW-35-50 kt.

KBOI...Mainly VFR. Rain showers bringing periods of MVFR
visibilities, ending by Mon/10Z. Mountains obscured. Surface
winds: SE 8-12 kt with afternoon gusts to 20 kt.

&&

.HYDROLOGY...Moderate to heavy rain along with low elevation
snowmelt will cause significant rises on rivers, creeks, and
streams in SE Oregon, and portions of SW Idaho (particularly in
the Weiser Basin) beginning today through Monday. Soils are
likely frozen in some of the lower elevations as well which will
enhance runoff. Snow and ice may lead to clogged culverts and
ditches causing ponding of water in poor drainage areas.
Additionally, ice jams could develop on any rivers or streams
with existing ice cover. Rivers in SE Oregon and the Weiser
River will continue to run high through next week, potentially
reaching bankfull.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Tuesday night...Current satellite
imagery shows a notable plume of subtropical moisture making its way
into the Pacific Northwest this morning. This pattern has increased
precipitable water values to the 99th percentile (high end) for this
time of year. Showers have already increased across much of
southeast Oregon and portions of southwest Idaho associated with the
first in a series of trough passages. Current snow levels are
approximately 4500-6500 feet MSL, but will continue to rise to
around 6000-8000 feet by mid-day today. This will support rain
as the primary precipitation type across most of the forecast
area, with moderate to heavy snow amounts limited to high
elevations. There is a slight chance (20%) of freezing rain for
portions of the western Magic Valley this morning, as
temperatures will be slow to rise above freezing. Despite the
increase in precipitation coverage today, temperatures are
anticipated to climb to near-normal values by this afternoon.
Showers will become widely scattered this evening and overnight,
mainly focused over the mountains of southwest Idaho. By Monday
morning, snowfall totals will peak between 8-16 inches above
7000 feet MSL, with relatively minor amounts between 5000 and
7000 feet. Rainfall totals could reach 0.20 to 0.50 inches for
most valley locations, and up to 1 to 2 inches of liquid
equivalent for the favored upslope terrain of southwest Idaho
such as the Weiser River Basin, Boise Mountains, and the
mountains of west-central Idaho. The probability of exceeding 2
inches of liquid equivalent is much lower, at less than 20%
chance for these locations. Due to the ample rain on existing
snowpack, in combination with low elevation snow melt, minor
flood impacts are possible with rising river and stream levels.

Thereafter, an upper level ridge will begin to amplify across
the Northern Rockies Monday as moderate to strong southwest
flow moves over the forecast area. The continued moisture will
support warm frontal precipitation to develop across the
northern zones during the day, while the southern areas should
see a temporary break in precipitation. The drier conditions,
combined with breezy to windy southerly flow at the surface,
will support another day of mild temperatures and high snow
levels for most areas. Current models project a cold front to
arrive Monday night into Tuesday, introducing a 30-60% chance of
showers across northeast OR and west-central ID. Winds will
remain breezy on Tuesday as they transition to west and
northwest with the cold front. As a result, Tuesday
temperatures will be lowered by several degrees from Monday with
colder northwesterly flow developing aloft. Snow levels will
lower to around 3000-4000 feet, allowing for additional light
snow accumulations over the mountains. Shower chances will
decrease by Tuesday night as drier high pressure shifts inland.

LONG TERM...Tuesday Through Saturday...Good agreement that the
region will be dominated by upper-level ridging Tuesday Night
through Saturday. Nearly 100% of ensemble guidance along with
deterministic runs support this pattern, making for increased
confidence. Upper level heights are forecast to approach 565 to
570dm making a strong case for above normal temperatures. NBM
guidance is indicating temperatures 5 to 10 degrees above normal
area-wide. By the end of the week there is a 15-20% chance of
temperatures above 60 degrees across eastern Oregon, and a 40-60%
chance in the lower valleys of southwest Idaho. The next
precipitation maker is slated for late Saturday.

AVIATION...VFR, becoming widespread MVFR/IFR/LIFR with shower
activity after 06-09Z/Sunday as a storm system moves into the
region. Snow levels will rise to 6000-8000 feet by mid day.
Mountains obscured. Surface winds: SW-SE 10-25 kt. Winds aloft
at 10kft MSL: WNW 25-40 kt.

KBOI...VFR, increasing chance of MVFR/IFR conditions (30-50%) in
showers after 09Z/Sunday. Conditions lingering through at least
20Z. Surface winds: SE around 10 kt.

&&

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

&&

$$

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DISCUSSION...DG
AVIATION.....SA
HYDROLOGY....TL
SHORT TERM...SH
LONG TERM....TL