360
FXUS65 KBOI 191639
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
939 AM MST Sun Jan 19 2025

.DISCUSSION...Cold temperatures in the low teens to low twenties
were observed across the region, with many mountain locations
reaching near 0F. Clear skies with breezy winds will continue
today, as a weak cold front moves through the eastern portion of
our region. A weak convergence zone looks to set up over the
Magic Valley, bringing light snow with minimal accumulation
later this evening. Cold temperatures will continue as the
Arctic air continues to push into the region from Canada. No
updates necessary to the forecast.

&&

.AVIATION...Generally VFR. Isolated afternoon snow showers
creating brief MVFR and mountain obscuration for central ID mtns
mainly east of KMYL. Potential for snow showers to reach
KTWF/KJER around 20/06Z. Surface winds: variable less than 10
kt, then NW-N 5-10 kt this afternoon. Winds aloft at 10kft MSL:
N-NE 20-30 kt.

KBOI...VFR. A 10% chance of brief MVFR ceilings from low clouds
this evening. Surface winds: variable, becoming NW 6-12 kt
after 19/18Z.

&&

.AIR STAGNATION...A surface inversion is expected to return on
Tuesday as high pressure builds over the region. Mixing heights
are anticipated to remain below 2,000 feet through at least
early Friday. Surface winds on Tuesday could delay the surface
inversion, with east-southeast winds around 10 mph. Lighter
winds are forecast for Wednesday and Thursday. Confidence in the
timing of the next cold front is low, but most guidance
indicates it will move through the region on Friday, likely
dissipating the inversion.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Tuesday night...A modified Arctic
air mass will persist through at least Monday under steady
northerly flow, bringing the coldest temperatures of the winter
season so far, particularly in areas with existing snow cover.
In the western Snake River Plain, daytime highs will remain
slightly above freezing, while morning lows are expected to
range from the upper teens to the low 20s. Regions with
substantial snow cover, such as the Camas Prairie and Long
Valley, may see morning lows ranging from just above zero to as
cold as 20 degrees below zero.

Sunday night, a back-door cold front will reinforce the
existing cold air mass as modified Arctic air settles in from
the north and east. While the front is expected to remain
generally dry, some high-resolution models indicate a slight
chance of light snow showers in central Idaho late Sunday night,
potentially reaching the Western Magic Valley and southern Twin
Falls County early Monday morning. A 1525% chance for light
snow remains in place across the central Idaho Mountains, with a
15% chance of flurries or light snow showers in south-central
Idaho along a wind convergence zone as colder air moves into the
Snake Plain from eastern Idaho.

By Tuesday, an upper-level ridge will shift eastward, bringing
warmer temperatures to the region, particularly across southeast
Oregon, where highs will rise into the upper 30s to low 40s.
However, much of southwest Idaho, especially the valleys, will
continue to experience below-normal temperatures as cold air
remains trapped. The arrival of the ridge will also reintroduce
surface inversions, leading to stagnant conditions across the
area.

LONG TERM...Wednesday through Sunday...A ridge will amplify along
the west coast on Wednesday and support dry, northerly flow over
southeast Oregon and southwest Idaho. As the ridge strengthens,
heights will gradually increase over the area and help to moderate
the temperatures Wed, with further warming expected Thursday. The
exception will be at lower elevations and sheltered valleys, in
which cold pools may take longer to scour out. This has created a
bit of uncertainty in the deterministic temperature forecast in the
valleys, particularly on Thursday. Thereafter, a trough is forecast
to arrive from the north Friday, with a breezy cold front attempting
to stir cold pools Friday into the weekend. The chance for snow
showers will increase Fri/Sat to 15-30 percent with the trough, with
higher elevations most favored. Chances will decrease by late
Sat/Sun as a deep layer of drier air arrives in its wake. Despite
the trough and continued northerly flow, temperatures are expected
to be within a few degrees of normal by the end of the week and
weekend.

&&

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

&&

$$

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DISCUSSION...SA
AVIATION.....SA
AIR STAGNATION...JDS
SHORT TERM...JDS
LONG TERM....SH