653
FXUS65 KBOI 121631
AFDBOI

Area Forecast Discussion
National Weather Service Boise ID
931 AM MST Wed Feb 12 2025

.DISCUSSION...Arctic air firmly in place across the region this
morning with low temperature values in the single digits to
below -20 degrees in the coldest spots. The cold is is
entrenched across all of the Pacific Northwest and northern
Rockies. Satellite imagery is depicting our approaching weather
maker off the coast, and there are indications that the upper
level pattern may be directing the most moderated Pacific
airmass to our south, enhancing the chance for snow area-wide,
not just for tomorrow, but throughout the weekend. First glance
at the pattern and guidance this morning keeps us on track for a
significant storm tomorrow afternoon with snowfall and wind.
Details to follow with the afternoon forecast package today, and
no updates are planned this AM.

&&

.AVIATION...Mainly VFR. Local MVFR/IFR in low clouds and fog in
lower valleys around KBNO and KGNG dissipating by afternoon. Surface
winds: variable around 10 kt or less through today. Winds aloft at
10kft MSL: NW-N 15-25 kt, becoming SW 15-25 kt this evening.

KBOI...VFR. Light winds 5 kt or less.

&&

.PREV DISCUSSION...
SHORT TERM...Today through Friday night...One more cold day on
tap for Wednesday with mostly clear skies. Temperatures this
morning have reached -27F at Burns OR this morning, shattering
the old daily record. Temperatures have remained in the single
digits in the Treasure Valley, with -10 to -20 across the
mountain valleys. A low pressure system off the West Coast and
southern Gulf of Alaska will strengthen and move eastward onto
the Oregon Coast by Thursday morning. With the cold air in
place, a warm front will overrun the cold air in place and cause
moderate snow over the area by midday Thursday across eastern OR
and Thursday evening across southwest ID. With the
strengthening low pressure off the coast, a pressure gradient
will strengthen over the area, with southeast winds increasing
to 20-30 mph, with local gusts up to 45 mph through the I-84
corridor from the Magic Valley through Baker County, and across
the Camas Prairie Thursday afternoon and evening. A winter storm
warning has been issued for snow and blowing snow in these
areas. Heavy snow expected across Malheur and Harney Counties,
and the Owyhee and Boise Mountains with 6 to 12 inches possible.
A warm front will lift north early Friday morning, but cold air
should remain in the valleys longer than what the models are
showing, with snow levels remaining near the valley floors into
midday Friday. The trough axis swings through on Friday, with
continued snow showers. The cold front on Friday will move
through, and may actually help to mix out the cold air trapped
in the valleys. The Magic Valley and Treasure Valley may mix out
to rain on Friday but forecast confidence remains low during
this transition to warmer Pacific air.

LONG TERM...Saturday through Wednesday...An upper level ridge
will move toward us and then pass over the area Saturday and
Saturday night, giving us a brief break in precipitation.
Precipitation is forecast to move in from the west late Saturday
night and especially Sunday as a the initial shortwave trough
associated with a large trough off the coast arrives. Snow
levels will be low enough for precipitation to begin as snow for
most areas, but by Sunday afternoon a change-over to rain below
around 3500 ft AGL is expected. Precipitation remains in the
forecast Sunday night through Monday night for most areas, as
additional weak shortwaves move out of the trough and over us.
Snow levels will remain high enough for rain below around
3500-4000 ft and snow above Monday, but lowers to valley floors
Monday night as the main trough opens up and moves over the
region. The chance for snow continues in the mountains Tue
(15-40%) but is too low to mention for most lower elevations
areas. Ensembles show support for yet another wave either Wed or
Thu, so PoPs are increased Wed in the latest forecast, but
confidence in timing is low. Temps will remain below normal
through the long term period, but should be significantly warmer
than what the area has experienced the past few days.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Cold Weather Advisory until 10 AM MST Thursday
     IDZ011>016-029-030-033.
     Winter Weather Advisory from 5 AM Thursday to 11 AM MST Friday
     IDZ011-013-015.
     Winter Storm Warning from 5 AM Thursday to 11 AM MST Friday
     IDZ012-014-016-028-029-033.
     Extreme Cold Warning until 10 AM MST Thursday IDZ028.
OR...Cold Weather Advisory until 10 AM MST /9 AM PST/ Thursday
     ORZ061>064.
     Winter Storm Warning from 5 AM MST /4 AM PST/ Thursday to 11
     AM MST /10 AM PST/ Friday ORZ061>064.

&&

$$

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DISCUSSION...MC
AVIATION.....TL
SHORT TERM...KA
LONG TERM....SP