Widespread freezing drizzle contributed to numerous road closures and accidents across the Denver area and over the northeast plains of Colorado. Several crashes were reported on Interstate 25, and several cities and counties went on accident alert.
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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 BOU wrote it up.
Widespread freezing drizzle contributed to numerous road closures and accidents across the Denver area and over the northeast plains of Colorado. Several crashes were reported on Interstate 25, and several cities and counties went on accident alert. Up to 32 delays at Denver International Airport. Numerous school delay openings and some school and business closures were reported over northeast Colorado.
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 Denver/Boulder, CO wrote its last area forecast discussion before the first event at Feb 1, 4:36 AM MST, 1 hour 24 minutes earlier.
Area Forecast Discussion National Weather Service Denver/Boulder CO 436 AM MST Wed Feb 1 2017 .SHORT TERM...(Today and tonight) Issued at 435 AM MST Wed Feb 1 2017 First surge of cooler air has pushed across the plains with low clouds spreading over Denver and brushing up against the higher terrain of the Palmer Divide. The winds have been slower to turn southeast than expected, and it looks like this trend will continue. Mesoscale models are developing a Denver cyclone type circulation this morning as the plains winds go southeast, but there is better agreement now that this will stay east or southeast of Denver, leaving the city in the cooler air. The steady flow of cool moist air will continue, though the southerly winds over the area between Castle Rock and Limon will likely keep the low clouds out with warmer temperatures there. Adjustments with this forecast package will be to shift the temperature gradient across Denver southward, with the warmest air staying south of the city. This also means low clouds should be slower to erode, though some dissipation on the edge is still expected to allow for some sunshine in Denver and near the foothills this afternoon. Models are now showing a secondary surge of colder air to come in sooner, aided by diurnal upslope enhanced by the temperature and cloud gradient around Denver this afternoon. There is not a well- defined boundary, but there is a subtle secondary pressure surge associated with the jet streak now across the northern plains, and this should get enhanced or merge with the diurnal tendencies over northeast Colorado this afternoon. This should bring the low clouds surging westward again in the late afternoon or early evening, and the low levels will likely be saturated in the incoming air. This means that we still look to be on track for a freezing drizzle event overnight. There may be some snow over the northeast corner from another passing jet streak, but this will more likely stay further north. Elsewhere the forcing will just be the upslope of a saturated cold air mass that will be 2-4 thousand feet deep. This could well lead to a steady light freezing drizzle that goes on much of the night leading to enough accumulation for slick roads. Not expecting more than about a tenth of an inch of liquid, but that should be enough to cause problems. One exception might be enhanced precipitation rates in the lower foothills from the upslope. The drizzle and fog may begin to lessen around Denver before morning as the low level flow goes southeast and starts to dry out the surface a bit. It is more likely to persist in the northeast corner where the moisture will be deeper. I will defer on the details of an advisory to the day shift which may be able to pin down the threat better, but we will highlight that there will be some impact in our products. .LONG TERM...(Thursday through Tuesday) Issued at 435 AM MST Wed Feb 1 2017 Any freezing drizzle that occurs Thursday morning should end by late morning as mixing and low level dry air is advected in. Latest model soundings have the near surface layer drying out by 9 AM, with drying coming first to Denver metro area and spreading northeast. Light snow across the far NE corner of the state should also come to an end by noon Thursday as the flow turns more southeasterly, advecting drier air into the area. Cloud cover will inhibit warming across the Plains. The northeast corner will remain in the 20s with persistent cloud cover and proximity to the deepest cold air. Generally highs will reach the mid to upper 30s across the urban corridor. Thursday night into Friday morning will be windy above 7500 feet MSL with strong westerly flow at and above 700 mb. Could see gusts over 50 mph across the high passes in the mountains. A quick shot of light snow is likely to develop along the west slopes with the strong flow and moisture transport from the west-northwest. Amounts should be light (1-4") with the highest amounts for the Park and Medicine Bow ranges, as well as Rocky Mountain National Park. Across the Plains, surface winds will be strongly influenced by a building surface high pressure area across Nebraska, resulting in south and southeast flow across the plains. A mid- level ridge builds across the state throughout the day on Friday keeping all areas dry and initiating a warming trend, including for the mountains. A lack of downslope will keep temperatures in check across the Plains, close to seasonal norms. The mountains should warm into the mid and upper 30s. On Saturday, a quick moving and weak storm system will impact the mountains. The Central and Northern mountains should see snow much of Saturday but amounts should be on the light side, not anticipating a need for any highlights. Across the Plains the storm system kicks in downslope winds and mid to upper 50s high temperatures return to all of the Plains with breezy and very dry conditions. It looks windy again in and near the in and near the Foothills Saturday morning with a chance of a mountain wave developing. Saturday night into Monday morning a ridge builds across the state as another, much stronger Pacific storm approaches the Pacific Northwest. The atmosphere looks pretty dry state-wide with WSW flow in place. On Monday and Tuesday the GFS and ECMWF are in fair agreement on the evolution of the Pacific Northwest storm. A WNW 150 kt jet comes on shore Monday morning near the CA/OR border. By Monday night the entrance region of the jet impacts Colorado. This is where the models begin to differ. The ECMWF has a much stronger jet and puts NE Colorado into the left exit region on Tuesday, while the GFS is slower and doesn't bring the jet into Colorado until late Tuesday night. The jet max and strong 500 mb flow will advect rich Pacific moisture into the mountains and turn on the snow machine late Monday and continue through Tuesday and perhaps beyond. It's far too early to provide much more detail but there is potential for a significant snow event in the mountains late Monday through Tuesday. Both models hint at some precipitation across the Plains associated with a cold frontal passage and fairly strong synoptic scale ascent but confidence is low at this point. && .AVIATION...(For the 12Z TAFS through 12Z Thursday morning) Issued at 435 AM MST Wed Feb 1 2017 IFR ceilings will persist over Denver much of the morning. The clouds are expected to lift and erode away from the mountains in the 16z-18z time frame, though there will likely still be low clouds on the plains. There is a chance that the clouds will persist with MVFR ceilings into the afternoon. The clouds are expected to move back into the Denver area between 23z and 03z this evening with IFR conditions redeveloping. A period of freezing drizzle is likely overnight, and periods of LIFR ceilings/visibilities are possible. Minor ice accumulations are possible overnight, but less than a tenth of an inch. Conditions will improve with the threat of freezing drizzle ending between 10z and 15z Thursday. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && SHORT TERM...Gimmestad LONG TERM...Schlatter AVIATION...Gimmestad
HAZARDOUS WEATHER OUTLOOK NATIONAL WEATHER SERVICE DENVER/BOULDER CO 1239 PM MST TUE JAN 31 2017 COZ030>051-011945- JACKSON COUNTY BELOW 9000 FEET- WEST JACKSON AND WEST GRAND COUNTIES ABOVE 9000 FEET- GRAND AND SUMMIT COUNTIES BELOW 9000 FEET- SOUTH AND EAST JACKSON/LARIMER/NORTH AND NORTHEAST GRAND/ NORTHWEST BOULDER COUNTIES ABOVE 9000 FEET- SOUTH AND SOUTHEAST GRAND/WEST CENTRAL AND SOUTHWEST BOULDER/ GILPIN/CLEAR CREEK/SUMMIT/NORTH AND WEST PARK COUNTIES ABOVE 9000 FEET-LARIMER AND BOULDER COUNTIES BETWEEN 6000 AND 9000 FEET- JEFFERSON AND WEST DOUGLAS COUNTIES ABOVE 6000 FEET/GILPIN/CLEAR CREEK/NORTHEAST PARK COUNTIES BELOW 9000 FEET- CENTRAL AND SOUTHEAST PARK COUNTY- LARIMER COUNTY BELOW 6000 FEET/NORTHWEST WELD COUNTY- BOULDER AND JEFFERSON COUNTIES BELOW 6000 FEET/WEST BROOMFIELD COUNTY- NORTH DOUGLAS COUNTY BELOW 6000 FEET/DENVER/WEST ADAMS AND ARAPAHOE COUNTIES/EAST BROOMFIELD COUNTY- ELBERT/CENTRAL AND EAST DOUGLAS COUNTIES ABOVE 6000 FEET- NORTHEAST WELD COUNTY-CENTRAL AND SOUTH WELD COUNTY-MORGAN COUNTY- CENTRAL AND EAST ADAMS AND ARAPAHOE COUNTIES- NORTH AND NORTHEAST ELBERT COUNTY BELOW 6000 FEET/NORTH LINCOLN COUNTY- SOUTHEAST ELBERT COUNTY BELOW 6000 FEET/SOUTH LINCOLN COUNTY- LOGAN COUNTY-WASHINGTON COUNTY-SEDGWICK COUNTY-PHILLIPS COUNTY- 1239 PM MST TUE JAN 31 2017 THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHEAST AND NORTH CENTRAL COLORADO. .DAY ONE...TODAY AND TONIGHT GUSTY WESTERLY WINDS WILL CONTINUE AT HIGHER MOUNTAIN ELEVATIONS THROUGH THIS EVENING. GUSTS IN THE 30 TO 40 MPH RANGE WILL BE COMMON...WITH HIGHER GUSTS IN THE 50 TO 60 MPH RANGE UP AROUND TIMBERLINE. ELSEWHERE EXPECT ABOVE AVERAGE TEMPERATURES TODAY WITH MOSTLY LIGHT BREEZES. TONIGHT A COLD FRONT WILL SLIP SOUTHWEST ACROSS THE NORTHEAST PLAINS OF COLORADO TONIGHT AND REACHING THE FRONT RANGE FOOTHILLS BEFORE MORNING. ONCE THE FRONT PASSES...EXPECT LOW CLOUDS AND PATCHY FOG TO FORM ON THE PLAINS AFTER MIDNIGHT...AND A SLIGHT CHANCE OF FREEZING DRIZZLE OR VERY LIGHT SNOW ACROSS THE CORNER OF THE STATE. .DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY FOG AND FREEZING DRIZZLE WILL BE POSSIBLE WEDNESDAY MORNING BEHIND A COLD FRONT. THE BEST CHANCE FOR FOG AND FREEZING DRIZZLE WILL BE EAST OF A LINE FROM FORT MORGAN TO LIMON. THERE WILL BE A SLIGHT CHANCE THE FOG AND FREEZING DRIZZLE ADVANCE FARTHER WESTWARD. FOG AND FREEZING DRIZZLE IS EXPECTED WEDNESDAY EVENING THROUGH THURSDAY MORNING ALONG THE FRONT RANGE AND ACROSS NORTHEAST COLORADO. ROADWAYS AND ELEVATED SURFACES ARE EXPECTED TO BECOME COATED IN A LAYER OF ICE. ANTICIPATE VERY SLICK AND ICY CONDITIONS LATE WEDNESDAY EVENING THROUGH THURSDAY MORNING. FOR THE MOUNTAINS...PERIODS OF LIGHT SNOW ARE EXPECTED THROUGH THE WEEKEND. THE FIRST SYSTEM IS EXPECTED THURSDAY NIGHT, WITH NEXT ONE HITTING FRIDAY NIGHT AND SATURDAY. A STRONGER SYSTEM MAY AFFECT THE MOUNTAINS EARLY NEXT WEEK. .SPOTTER INFORMATION STATEMENT... SPOTTER ACTIVATION WILL NOT BE NEEDED TODAY OR TONIGHT. BAKER/MEIER
The national radar mosaic for the moment the first event began.
7 winter weather. Local standard time, as filed.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2017Every state in 2017This day in weather historyWarnings in Colorado, February 2017
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: 681059, 681060, 681061, 681062, 681063, 681064, 681065.