A snow storm which began on February 25th brought periods of heavy snow to Southwestern Idaho. The heaviest snow fell at elevations above 4000 feet where amounts reached 12 to 18 inches in less than 24 hours.
Every event with a place to put it; 4 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.
A snow storm which began on February 25th brought periods of heavy snow to Southwestern Idaho. The heaviest snow fell at elevations above 4000 feet where amounts reached 12 to 18 inches in less than 24 hours. When the snow ended early in the morning on February 26th, McCall, Donnelly, and Cascade, Idaho measured 10 to 12 inches of new snow. The higher mountain areas including the ski resorts measured around 18 inches of new snow. The heavy mountain snow significantly increased avalanche danger during this time which prompted the closure of Idaho 21 until the danger passed.
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 Feb 25, 3:57 AM MST, 3 hours 3 minutes earlier.
Area Forecast Discussion
National Weather Service Boise ID
357 AM MST Sun Feb 25 2018
.SHORT TERM...Today through Monday...A vigorous upper level trough
is moving south along the British Columbia coast this morning with
moisture streaming into the Pacific Northwest. Temperatures this
morning are colder than anticipated, thus have lowered high
temperatures for today slightly. Snow will develop across the
west central Idaho mountains and Baker County OR this morning and
become widespread across much of the region by this evening, with
the exception of precipitation shadowing directly east of the
Owyhee Mountains of SW Idaho and Steens Mountain in SE Oregon.
Westerly flow aloft will favor heavy snow across the West Central
Mountains and Boise Mountains ahead of the cold front. The cold
front will move through the region late Sunday night and into
Monday morning. Snow will taper off quickly behind the cold front
from NW to SE on Monday, with isolated snow showers continuing
across the central ID mountains and south along the NV ID/OR
border through Monday evening. Breezy northwest winds are expected
on Monday afternoon behind the cold front.
.LONG TERM...Monday night through Saturday...Snow showers end Monday
night as the trough axis swings through and the main upper low moves
far to the southwest. Northwest flow Tuesday will back to westerly
on Wed in advance of another system, and mountain snow showers are
possible through this time. This large strong system will spread
snow to all areas Wed night through Friday, with several periods of
snowfall for lower elevations and nearly continuous snow for the
mountains. Mountains could easily end up with over a foot of new
snow with this storm. A cold front will move through Friday,
continuing the chance for precipitation. Snow showers remain
possible through next weekend as we reside under a broad upper level
trough. Temperatures will remain well below normal through the
extended period.
&&
.AVIATION...VFR initially. Mountains deteriorating into IFR with
snow after 12Z. Lower elevations VFR/MVFR after 15Z in snow showers.
A cold front will move through tonight, bringing additional snow.
Surface winds: southeast to southwest 10-20 kts except 15-25 kts
over the higher terrain, transitioning to northwest after 26/00Z.
Winds aloft at 10k ft MSL: northwest 25-35 kts becoming west 30-40
kts after 21z.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Winter Storm Warning until 5 AM MST Monday IDZ011-013-033.
Winter Weather Advisory from 2 PM this afternoon to 5 AM MST
Monday IDZ014>016-028>030.
OR...Winter Weather Advisory from 2 PM MST /1 PM PST/ this afternoon
to 5 AM MST /4 AM PST/ Monday ORZ061-063.
Winter Weather Advisory until 10 PM PST this evening ORZ062.
&&
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SHORT TERM...KA
LONG TERM....SP
AVIATION.....SPThe national radar mosaic for the moment the first event began.
4 heavy snow. Local standard time, as filed.
Trained spotters reported 11.5 inches of snow 3 miles NE of Donnelly and 12.0 inches 9 miles SSE of McCall, Idaho.
Brundage Ski Resort reported 18 inches of storm total snow accumulation.
Storm total snow accumulation of 18.5 inches was observed in Featherville, Idaho ending around 6 am on February 26th.
Storm total snow accumulation of 13.0 inches was measured by the Idaho Transportation Department avalanche forecasters at Banner Summit along Idaho Highway 21.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Idaho in 2018Every state in 2018This day in weather historyWarnings in Idaho, February 2018
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: 742400, 742404, 742391, 742393.