Garden City, Idaho 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

877
FXUS65 KBOI 132150
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
250 PM MST Tue Jan 13 2026

.SHORT TERM...Tonight through Thursday night...The upper level
ridge will remain the dominant feature over the region through
the short term period. This pattern will maintain dry and stable
conditions across southeast Oregon and southwest Idaho. As the
ridge strengthens, valley inversions will deepen, trapping cold
air and pollutants near the surface while temperatures aloft
remain unseasonably warm. High resolution models indicate a
higher probability of dense fog redeveloping in the Lower
Treasure Valley late tonight. Due to this signal and the
strengthening inversion, a Dense Fog Advisory has been issued
for the Lower Treasure Valley from late tonight through
Wednesday morning. Confidence in dense fog at Boise Wednesday
morning is lower, with around a 30% chance of occurrence. Patchy
fog is also expected in the Upper Treasure Valley, Western
Magic Valley, and sheltered mountain valleys. Stratus and fog
will be difficult to dissipate, especially in the Lower Treasure
and Long Valleys on Wednesday. Expect fog to return across much
of the Snake River Plain and sheltered valleys across southeast
Oregon and southwest Idaho Wednesday night into Thursday.
Temperatures will remain inverted, with valleys seeing highs
near or slightly below normal and mountain locations seeing
highs 5 to 10 degrees above normal. The NBM, along with most
guidance, has struggled to resolve the cold air trapped within
the inversion in sheltered valleys. Consequently, areas trapped
in stratus and fog will see very little diurnal temperature
range.

LONG TERM...Friday through Tuesday...Clusters and ensembles
continue to point at a high amplitude ridge over the Western U.S.,
with little relief in sight. Air stagnation and fog will continue to
be headlines through the extended. Areas of higher elevation will
continue to see higher temperatures than lower mountain valleys due
to entrenched cold pools in lower elevations.

Relief from the stagnant conditions looks to come late next Tuesday
into Wednesday with an upper level trough bringing chances of
precipitation and increased mixing. Ensemble members of the
ECMWF/GFS show varying degrees of precipitation and timing of the
next system, but there is generally good agreement in the breakdown
of the ridge by the end of next week.

&&

.AVIATION...VFR. MVFR-IFR conditions from patchy fog/low stratus,
mainly in sheltered mountain-valleys and lower basins, returns
overnight Tuesday into Wednesday morning. Confidence has been
increasing for this to occur in the lower Treasure Valley, portions
of the Upper Treasure Valley, and the Long Valley. Mountain
obscuration in fog/low stratus. Surface winds: variable under 10 kt.
Winds aloft at 10kft MSL: NW 10-25 kt.

KBOI...VFR through Tuesday afternoon. Confidence in fog/low stratus
is increasing starting 01z/Wed through 18z/Wed. Chances of MVFR-LIFR
conditions stay around 50%. Surface winds: light and variable.


&&

.AIR STAGNATION...The strong ridge aloft combined with light
surface winds will continue to suppress vertical mixing across
the region. Mixing heights are expected to remain very low,
generally below 1000 feet AGL in the valleys, with light
transport winds. These conditions will lead to a buildup of
pollutants near the surface. The Air Stagnation Advisory remains
in effect for all valley zones in southeast Oregon and southwest
Idaho through the week. No significant pattern change is
expected to scour out the inversions until at least the weekend.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Air Stagnation Advisory until 5 AM MST Monday
     IDZ011>014-016-028-033.
     Dense Fog Advisory from 11 PM this evening to noon MST
     Wednesday IDZ012.
OR...Air Stagnation Advisory until 5 AM MST /4 AM PST/ Monday
     ORZ061>064.
     Dense Fog Advisory from 11 PM MST /10 PM PST/ this evening to
     noon MST /11 AM PST/ Wednesday ORZ064.

&&

$$

www.weather.gov/Boise

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SHORT TERM...JDS
LONG TERM....CH
AVIATION.....CH
AIR STAGNATION...JDS