Dense fog formed in some of the southern valleys within western Colorado as low level moisture remained trapped behind a departing winter storm.
Every event with a place to put it; 2 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 GJT wrote it up.
Dense fog formed in some of the southern valleys within western Colorado as low level moisture remained trapped behind a departing winter storm.
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 Grand Junction, CO wrote its last area forecast discussion before the first event at Dec 12, 4:04 PM MST, 2 hours 56 minutes earlier.
Area Forecast Discussion National Weather Service Grand Junction CO 404 PM MST Mon Dec 12 2016 .SHORT TERM...(Tonight through Tuesday night) Issued at 252 PM MST Mon Dec 12 2016 A couple of weather systems over the US in the short term will not create any particularly interesting weather over the Four Corners region the next couple of days other than shifting the 135 kt upper level jet on the KGJT sounding this morning north over the next 24 hours. The stronger of these systems - a closed low over Nunavut - will establish general troughiness over the eastern 2/3rds of the US over the next 24 hours. The second, a closed low slowly moving south along the coast of British Columbia will open up a tap of moisture from the Pacific Ocean into the Great Basin and Central Rockies. Surprised to see how much further north forecast models are bringing the energy from this closed low off of BC in today's 12z runs starting Tuesday night. .LONG TERM...(Wednesday through Monday) Issued at 252 PM MST Mon Dec 12 2016 Plenty of moisture will be available on Wednesday for overcast cloud cover and showers to develop over the Colorado mountains but really not seeing any good forcing to hang my hat on. Expecting most snowfall will occur on Wednesday across the northcentral CO mountains again in westerly to northwesterly flow...so the Rabbit Ears to Vail Pass to Aspen corridor. Amounts are looking like they will be generally in the 4 to 8 inch range above 8000 ft from the Park Range south to the Elk Range with lesser amounts in the high valleys like Aspen, Steamboat Springs, and Vail. This snowfall should move out by Thursday morning as a much bigger storm brews off of the coast of the Pacific NW. Temps will be 5 to 10 degrees above normal in many places midweek with this enhanced cloud cover. Utah and Colorado will begin to see changes with the large incoming closed low beginning late Thursday. For the first part of this winter weather system (Thurs night-Fri afternoon), the region will be in a prominent WAA pattern in southwesterly flow. The cold front associated with this is progged to occur Friday evening through early Saturday and bring snow level all the way down to low valley levels. Models are hitting the probability of precipitation (POP) hard across the region, but I brought down POPs on Thursday on NE facing slopes that don't tend to do well in this pattern without significant forcing. This may be one of those rare events where it happens, but really thinking those NE facing slopes won't start accumulating precip until the prefrontal period on Friday. If this weather system stays on track, it could be a big snow maker for eastern Utah and western Colorado in the high country. Snow levels and ratios will change a lot throughout this system which will make for some exciting and challenging forecasting over the next few days. Cooler than normal temperatures will persist for at least a few days after this cold front passes through Friday night. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 401 PM MST Mon Dec 12 2016 VFR conditions will prevail at all TAF sites through the next 24 hours. Mid and high level clouds will continue to stream over the area for occasional BKN to OVC ceilings. Some light, orographic snow showers no west through north facing slopes will persist over most Colorado mountains locally obscuring the mountain tops. && .GJT WATCHES/WARNINGS/ADVISORIES... CO...None. UT...None. && SHORT TERM...JAM LONG TERM...JAM AVIATION...CC
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
The national radar mosaic for the moment the first event began.
2 dense fog. Local standard time, as filed.
Dense fog occurred between Durango and Ignacio where visibilities dropped to a quarter mile or less.
Dense fog developed in the San Juan River Basin where visibilities dropped to a quarter mile or less in some areas. Additionally, multiple vehicle crashes and roll-overs occurred on Highway 151 between Lake Capote and Ignacio due to freezing fog. Highway 151 was closed from the Chimney Rock area to County Road 334 due to icy road conditions.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2016Every state in 2016This day in weather historyWarnings in Colorado, December 2016
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: 679519, 679520.