An energetic vorticity maximum moved through the deep trough situated over the Pacific Northwest producing convective, heavy snow showers across the Treasure Valley of Idaho.
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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.
An energetic vorticity maximum moved through the deep trough situated over the Pacific Northwest producing convective, heavy snow showers across the Treasure Valley of Idaho.
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 1, 2:40 PM MST, 4 hours 20 minutes earlier.
Area Forecast Discussion National Weather Service Boise ID 240 PM MST Sat Dec 1 2018 .SHORT TERM...Tonight through Monday...A significant vort max is moving east through southeast Oregon this afternoon, enhancing showers as far east as western Owyhee County and the Treasure Valley. Latest mesoscale models indicate enough instability for some vigorous snow showers, some of which will be able to bring snow down the ground at elevations as low as around 2600 feet. All previous advisories have been taken down, and a new one for the Southern Twin Falls zone has been issued. This advisory runs from 5 pm MST through 11 am Sunday MST. The most consistent snow showers are expected in that area. Elsewhere, the mountains in our CWA in both Oregon and Idaho will see continued snow showers overnight and into Sunday. Amounts will range up to 4 inches in Baker County and up to 6 inches in the West-Central and Boise mountains in Idaho. Temperatures will cool each day through Monday, with highs a couple of degrees below normal Sunday, and around 5 degrees below normal Monday. By Monday morning, we should see enough clearing to allow fog to form in most of the usual places, including the Snake River Valley and many of the mountains-valleys, including the Long Valley. Snow showers will taper down significantly Sunday night and Monday, with only isolated to scattered activity remaining in the Idaho mountains. .LONG TERM...Monday night through Saturday...An upper level trough persists over the region, then moves eastward Tuesday as a low pressure system approaches. Though both the GFS and ECMWF have pulled this system south over the past few model runs, SE Oregon will see a slight chance of light snow showers on Wednesday. A ridge builds behind the outgoing system and lingers to the west into the weekend as conditions remain dry. Temperatures will stay 7-10 degrees below normal through the period. && .AVIATION...Mostly VFR with areas of local MVFR/IFR. Scattered snow showers across the region through Sunday afternoon. Mountain obscuration. Surface winds: variable 10 kts or less. Winds aloft near 10k feet MSL west 10-20 kts. Sunday outlook...Patchy morning valley fog. Scattered snow showers mainly over the higher terrain. Otherwise VFR. && .BOI WATCHES/WARNINGS/ADVISORIES... ID...Winter Weather Advisory until 11 AM MST Sunday IDZ030. OR...None. && www.weather.gov/Boise www.facebook.com/NWSBoise www.twitter.com/NWSBoise SHORT TERM...SP LONG TERM....AL AVIATION.....AL
The national radar mosaic for the moment the first event began.
1 heavy snow. Local standard time, as filed.
Four to ten inches of new snow fell mainly from Boise to Mountain Home. Reports ranged from four inches at the National Weather Service to seven inches in Southeast Boise and ten inches in Mountain Home.
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, December 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: 793902.