Mid-December's synoptic regime was dominated by a potent atmospheric river that caused widespread flooding on the west coast and persistent precipitation in the intermountain west. Forcing was largely provided by a stationary front along the river, with shortwaves in the mid-level flow allowing it to change from warm to cold front every few days as it kept active weather in the area.
Every event with a place to put it; 9 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS BOI wrote it up.
Mid-December's synoptic regime was dominated by a potent atmospheric river that caused widespread flooding on the west coast and persistent precipitation in the intermountain west. Forcing was largely provided by a stationary front along the river, with shortwaves in the mid-level flow allowing it to change from warm to cold front every few days as it kept active weather in the area. However, a deep mid-level trough would strengthen on the West Coast, and as it made landfall December 17th and 18th it pushed a surface low of 980 Mean Sea Level Pressure with winds at 700 millibars of near 100 knots. The strong cold front associated with the surface low, strong winds in the low-levels from the Pressure Gradient Force of the low and the atmospheric river, and the persistent moisture supply from the atmospheric river was the perfect environment for severe wind outbreak across southeast Oregon and southwest Idaho.
Unlike typical stratiform winter passages, this event featured embedded convective showers and thunderstorms. This convective element enhanced the transport of high-momentum air to the surface. It was noted that the atmospheric remained fully coupled throughout the event, a very rare occurrence in mid-December. The frontal passage brought winds of near 60 miles per hour across the area, while the morning squall along the front saw winds up to 80 miles per hour, with one ridgeline observation of over 100 miles per hour.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Boise, ID wrote its last area forecast discussion before the first event at Dec 17, 3:35 AM MST, 3 hours 11 minutes earlier.
Area Forecast Discussion
National Weather Service Boise ID
335 AM MST Wed Dec 17 2025
.SHORT TERM...Today through Friday night...Potent weather system
now moving onshore in the Pacific NW this morning, with
precipitation focused over the mountains. Snow levels remain
around 8000-9000' this morning. Upper level winds are unusually
strong as 700mb (~10000ft MSL) winds reach 100 kt over the
Owyhee Mountains this morning around 5am MST. A potent cold
front moves through midday with heavy showers and a slight
chance of thunderstorms along the front. Wind gusts of 50 to 60
mph possible along the cold front as it moves through. The
timing is not as favorable as central and eastern ID to realize
the fullest potential of the winds. The strongest winds will
occur during the afternoon, as the front tracks east, where a
high wind warning remains in effect for the Camas Prairie, Magic
Valley and southwest ID highlands. Precipitation quickly ends
behind the front and the winds slowly subside by Wednesday
evening. After a brief lull, the next warm front moves inland on
Thursday morning. This will bring snow to much of the area in
the morning, before changing to rain below 8000' MSL by Thursday
afternoon. Snow levels will remain lower around the Wallowas,
Hells Canyon, and around McCall until the late evening before
rising to around 6000-7000' MSL as cooler air will hold on
longer than the rest of the area. Snow amounts of 6 to 10 inches
possible on Thursday above 6500' MSL before snow levels rise.
Generally 2 to 4 inches in the mountain valleys of the west
central and Boise Mountains. The Snake Basin including the
Treasure Valley may see snow, but no accumulations expected.
Models have trended slower with the system, so lower valleys may
just see rain now if the precipitation comes later in the
morning Thursday. The warm front lifts northward by Thursday
evening, with dry conditions in the valleys, with continued
precipitation in the west central ID mountains. On Friday, winds
aloft become strong again, with precipitation becoming focused
over the mountains, with generally dry conditions in the Snake
Basin. A cold front oriented from west to east over northern OR
and central ID will slowly move south over the day on Friday.
Snow levels will be around 7000-8000' on Friday south of Boise
to Burns OR and around 5500' MSL near Baker and McCall. Snow
levels fall to the valley floors near Baker and McCall by Friday
night as the front moves south. Significant snow accumulations
will be confined to the highest peaks above 7500' MSL until the
cold front moves south. This pattern also favors dense snow
(low snow-to-liquid ratios) with the subtropical moisture, so an
inch of liquid equivalent will be around 5-8 inches of snow.
.LONG TERM...Saturday through Wednesday...A cold front will move
south Saturday morning, driving the majority of the
precipitation out of the area for the rest of the day. Max temps
are forecast to be 5-10 degrees cooler on Saturday compared to
Friday. The cold front will begin to retreat toward the north
once again by late Saturday as the next subtropical moisture
plume and milder airmass approaches Saturday night into early
Sunday morning. Snow levels will begin around 3kft MSL to the
north and 6kft to the south at the onset of the precipitation,
but will rise to 5kft for the north and 7kft for the south as
upper flow transitions to more southwesterly. Models have
discrepancies with the path of the moisture plume and
precipitation amounts, but overall precip chances will be 60-80%
for Sunday. Conditions may warm further Monday as an upper
level trough elongates over the West Coast and amplifies and
upper ridge over the Rockies, keeping E Oregon and SW Idaho in
southwest flow. Model discrepancies increase further on Monday,
with some members decreasing precipitation chances throughout
the day and nudge the colder airmass farther south into the
area. Tuesday will be a similar scenario to Monday, with
southwesterly flow aloft and differing precip/temp solutions
amongst the ensemble members. Overall, probability of
precipitation for the rest of Monday into Tuesday is 20-50%
across the area with southeast OR and the higher terrain of SW
Idaho being favored. As expected with the uncertainty, snow
levels will oscillate during this window which will provide the
opportunity for light snow down into mountain valleys. The upper
level trough and associated cold front should finally move
across the forecast area sometime Wednesday and break up this
stalled pattern regime.
&&
.AVIATION...Areas of rain, with snow above 7-9kft MSL ahead of
cold front. Generally VFR/MVFR in precip. Mountains obscured.
LLWS threat through morning. Strong, windy cold front moving NW
to SE Wed/12Z-20Z. Convective showers with lightning potential
will accompany front. Snow levels dropping from NW to SE as
precip ending. Surface winds: SW-SE 10-30 kt with gusts 30-55
kt, locally higher on mtn tops. Winds shifting to W-NW behind
the cold front. Gradually decreasing this afternoon. Winds aloft
at 10kft: W-SW 60-90 kt, decreasing to W-NW 35-55 kt this
afternoon behind front.
KBOI...VFR. Periods of rain. Low-level wind shear threat through
morning ahead of cold front. Showers becoming convective with
front late morning, with 10% chance of Treasure Valley
lightning. Precip chances end around Wed/17Z. Surface winds: SE
15-20 kt overnight with gusts around 30 kt. Then W-NW 15-30 kt
with 35-45 kt gusts between Wed/15Z-17Z with front, gradually
decreasing thereafter.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory until 5 PM MST this afternoon IDZ011-013-014-029.
Winter Storm Watch from late tonight through Thursday evening
IDZ011-013-028.
Wind Advisory until 11 AM MST this morning IDZ012-033.
High Wind Warning from 8 AM this morning to 5 PM MST this
afternoon IDZ015-016-028-030.
OR...Wind Advisory until 11 AM MST /10 AM PST/ this morning
ORZ061>064.
&&
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SHORT TERM...KA
LONG TERM....SH
AVIATION.....SHThe Pendleton radar (KPDT), 177 km away, was scanning. The volume nearest the first event began at 13:46 UTC.
14 thunderstorm wind, 9 high wind. Local standard time, as filed.
A wind gust measured instantaneously at 76 mph at Snake River RAWS occurred as a line of thunderstorms moved west to east.
The McCall ASOS measured a wind gust that peaked at 66 miles per hour as a line of thunderstorms moved through the area.
At approximately 7 AM, two children who were waiting for the bus near 3400 N and 3100 E just to the southeast of Twin Falls were critically injured as a strong thunderstorm wind gust uprooted and toppled trees. 65 mph gust is estimated based on pictures of the trees downed.
Winds estimated to be 65 miles per hour based on nearby observations caused damage to a non-profit camp in McCall. A large pine tree estimated to be 150 years old topped onto a camp building constructed in the 1970s. Trees also fell onto camp equipment which will need to be replaced. Costs estimated at 150-200 thousand dollars.
A member of the public posted a picture of a 6 inch diameter branch broken, as well as a large 1.5 foot diameter section of the tree snapped. Winds estimated to have been 60 miles per hour based on state and type of tree, at least severe given the size of the large branch that snapped off.
Multiple reports of trees down across the Western Magic Valley as pre-frontal, squall line, and post-frontal severe winds moved through. A roof was ripped off in Bliss. Two pine trees fell down on a house in Hazelton. Downed trees blocked roads in Jerome and Twin falls scattered debris.
Placeholder.
Our COOP observer in Yellowpine observed over 100 trees down on the road from Landmark, Idaho to Yellowpine. This is a remote wilderness road used mainly by rangers, locals, and recreators, and likely took some time to clean up. Based on number and type of trees winds estimated to be 70 miles per hour.
The Mountain Home Air Force Base ASOS measured a thunderstorm wind gust of 60 mph at 8:07 AM MST as a line of showers with embedded thunderstorms passed.
The general city of McCall area suffered multiple road closures due to power lines down after a line of thunderstorms move through. Warren Wagon, Lake St near Pueblo Lindo, and Hwy 55 between Little Ski Hill and Pueblo Lindo were all blocked and closed due to power lines down. The Streets and Parks department became overwhelmed with wind blown tree debris and trees downed.
The Idaho Transportation Department's Jerome Butte automated weather station observed a 62 mph wind gust coincident with the passage of a line of showers and embedded thunderstorms. Tree debris was strewn in the area.
A wind gust of 63 mph was measure at the KJER ASOS as a line of showers and embedded thunderstorms moved through.
The Idaho Transportation Department's Valley Interchange weather station south of Hazelton reported a 66 mph gust as a line of showers and embedded thunderstorms move through.
Media and Idaho Department of Transportation reporting one semi flipped on route 93 near Filer, Idaho. The flip occurred on a north-south bound section of the highway, and crosswinds from the west-northwest hit the side of the semi, flipping it and injuring the driver.
The Magic Valley Regional Airport's ASOS reported a 68 mph wind gust as a line of showers and embedded thunderstorms move through.
A member of the public posted a picture showing a tree toppled and snapped at the base that blocked a section of Grimes Creek Rd north of Centerville. The tree fell onto and damaged powerlines.
A member of the public posted multiple pictures of damage in the town of Hollister. Construction debris strewn across streets, brick walls toppled, trees uprooted, and damage to cars and property. Based on size of debris wind was likely 65 miles per hour.
Southern Owyhee County RAWS sites measure instantaneous gusts of 58-67 miles per hour. While likely a slight overestimate given the instantaneous calculation of gusts, observations in surrounding zones are consistent with severe winds gusts throughout the southwest highlands.
Mesonet and RAWS observations in Southern Twin Falls County ranged from wind gust peaks of 59 to 67 miles per hour. This is consistent with damage reported in the area. Gusts peaked during thunderstorms, but remained severe due to ongoing high winds.
Automated weather observations across the Western Magic Valley observed winds gusts of 60 to 69 miles per hour during the high wind event. Severe winds lasted for a few hours at multiple sites around the zone, with every observation site in the zone at least above 45 miles per hour. This is consistent with damage reports in the area.
Automated weather observations near the town of Fairfield, Idaho observed peak wind gusts of 61 miles per hour for a time span of at least an hour. Sparse reports in the area support debris being strewn across farms.
Automated weather observations in the Upper Treasure Valley from Boise to Mountain Home observed severe wind gusts above 58 miles per hour for multiple hours. This covers the I-84 transportation corridor and portions of the Snake River Canyon with extensive agriculture activity.
Snowmobile trail maintenance crews covered the Pilot Peak area shortly after the new year, the first time checking on the trail since before this event. Maintenance crews reported an astonishing number of trees down along the trails, and were quickly overwhelmed by the volume of cleanup required. There were hundreds of trees down on trails with already low snow, so many trails had to be closed. The crew reported that they would be unable to cut them all this year, and multiple feet of snow would be required to fully bury the trees.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2025Every state in 2025This day in weather historyWarnings in Idaho, December 2025
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1299224, 1299222, 1299244, 1301561, 1301510, 1299334, 1299340, 1301513, 1299276, 1299310, 1299316, 1299321, 1299325, 1301559, 1299328, 1301517, 1301520, 1301582, 1301568, 1301585, 1301587, 1301590, 1301597.