045
FXUS65 KBOI 081622
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
922 AM MST Wed Jan 8 2025

.DISCUSSION...The Pacific trough along the coast yesterday
weakened moving through the upper ridge but still produced a
few snow showers in our northern zones this morning. Forecast
was updated around 7 AM MST but radar showed the snow showers
decreasing or ending as of 9 AM. The next north Pacific trough
is forecast to arrive late Friday and Friday night with more
extensive snow showers, again mainly over northern and central
zones. That system also looks strong enough to mix out the
inversion and end the air stagnation. Current forecast has
this. No updates.

&&

.AVIATION...Mostly VFR.  Periods of high clouds today. Fog
developing overnight in parts of Treasure Valley, with a 30%
chance of visibility below 2 SM at KBOI, KONO, and KEUL after
09/10Z. Surface winds: variable less than 8 kt. Winds aloft at
10kft MSL: NW 20-35 kt.

KBOI...Mostly VFR, with MVFR in fog possible (60% chance)
overnight. Low confidence (30% chance) for MVFR/IFR fog/stratus
after 09/09Z. Surface winds SE around 5 kt today, becoming
variable overnight.

&&

.AIR STAGNATION...Current Air Stagnation Advisory will continue
in the valleys through Friday morning due to light winds and
mixing heights below 2000 ft AGL. A frontal system from the
Gulf of Alaska should scour the inversion and end the stagnation
late Friday.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Friday night...A weak upper level
system will pass by to our northeast and then east as it
progresses down the east side of a large upper level ridge
centered off the coast. Little to no precipitation is expected
in our area. The ridge will build back over the area tonight
through Thu night, then a moderate upper level trough will move
through late Friday. Precipitation will spread northwest to
southeast Friday afternoon into Friday night, with snow levels
low enough for snow at all but the lowest elevations in southern
Harney and Malheur counties, and perhaps along the Snake River.
Snow amounts are expected to be light, with totals through 5 am
Saturday ranging from a few tenths of a inch in lower
elevations, with 1 to 4 inches in the mountains. Temps will
reflect the inversion through Friday.

LONG TERM...Saturday through Wednesday...The cold front from
the system Friday night will be enough to scour out the
inversion, but another one is likely to form later in the long
term. Light snowfall Saturday will be confined to the northern
mountains Saturday as the system departs. A weak system is
depicted in virtually all ensemble runs Sunday, and low PoPs
(15-30%) exist over most of the area. Any snow that ends up
occurring will be light. Snow levels will be low enough for
snow at all elevations. Upper level ridging will return Monday
and likely last through at least Wednesday, bringing a new
inversion.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Air Stagnation Advisory until 11 AM MST Friday
     IDZ011>015-028-029-033.
OR...Air Stagnation Advisory until 11 AM MST /10 AM PST/ Friday
     ORZ061>064.

&&

$$

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DISCUSSION...LC
AVIATION.....JR
AIR STAGNATION...LC
SHORT TERM...SP
LONG TERM....SP