A storm system tracked from the Four Corners region eastward across Colorado. Consequently, period of moderate to heavy snow developed in and near the foothills of Jefferson and Douglas counties.
Every event with a place to put it; 5 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 BOU wrote it up.
A storm system tracked from the Four Corners region eastward across Colorado. Consequently, period of moderate to heavy snow developed in and near the foothills of Jefferson and Douglas counties. In the foothills, storm totals included: 17 inches, 4 miles south-southeast of Pinecliffe; 15 inches, 3 miles west of Conifer; 14 inches, 4 miles west-southwest of Eldorado Springs; 13.5 inches, 13 miles northwest of Golden; 12 inches in Genesee; 11.5 inches at Breckenridge; 11 inches at Roach and Deadman Hill SNOTELs; 10.5 inches, 3 miles northwest of Idledale; with 9 inches, 3 miles west-southwest of Golden, Lake Irene SNOTEL and Silverthorne. Across Denver and its western and southern suburbs and the Palmer Divide, storm totals included: 8.5 inches near Rocky Flats and 5 miles west-northwest of Arvada; 8 inches in Wheat Ridge; 7.5 inches in Federal Heights and 4 miles northwest of Elizabeth; 7 inches at Manila Village and near Greenwood Village; 6.5 inches in Westminster; 6 inches at Castle Pines, 3 miles south-southwest of Denver and Northglenn; and 5.7 inches at Denver International Airport. Elsewhere, storm totals ranged from 3 to 5 inches.
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 Jan 20, 3:16 PM MST, 2 hours 44 minutes earlier.
Area Forecast Discussion National Weather Service Denver/Boulder CO 316 PM MST Sat Jan 20 2018 .SHORT TERM...(This afternoon through Sunday) Issued at 1158 AM MST Sat Jan 20 2018 Upcoming weather system is currently digging into the Great Basin with rain and snow showers spreading across western Colorado and into Wyoming as upward QG vertical motion increases over the state. Snow will be increasing across the mountains through tonight, with upward QG values topping near -40 mb/hr by early Sunday morning. This is when the mountains will see their heaviest snowfall rates, between 1 and 2 inches per hour. The moisture will be spreading east, however low level moisture will push into the plains this evening first. Viewing forecast soundings over the plains show this moisture warmer than required for ice nucleation, therefore will continue to have a mention of freezing drizzle over the plains. This is most likely to occur between 9pm and 3am, before additional cooling from the north and deeper moisture moving east of the mountains will help change the precip over to snow. The exception will be over the far eastern plains where it may take longer for a switch over due to the delay in cooling and deeper moisture. This initial freezing drizzle layer will produce slick conditions before the expected snowfall tomorrow. Upslope winds will deepen early tomorrow morning into the late morning hours along with the increase of upward QG vertical motion for the eastern slopes of the Front Range mountains and foothills as well as the urban corridor to see snowfall rates increase. After noon, the upper low including the 700 mb low will push east into Kansas, therefore turning mountain top wind more northwesterly to begin decreasing snow from northwest to southeast. At the same time the pressure gradient will be increasing and winds across the area will increase, with gusts in the 35 to 50 mph, highest across the Palmer Divide and east. This may produce near Blizzard conditions, but not sure how long they will last. Will keep the mention of reduced visibilities in the Winter Storm Warning. Will add an Snow and Blowing Snow Advisory for zone 47, southern Lincoln County. Only expecting 2-4 inches down there, however strong winds will create hazardous conditions and low visibility in blowing snow. For total snow amounts, increase the forecast just slightly for the mountains with the strong upward QG and some models coming in slightly higher in amounts. Also decreased amounts ever so slightly over the plains due to a slight slowing and weakening of the storm in all models. Still, the strong upward QG should wring out a lot of moisture. .LONG TERM...(Sunday night through Friday) Issued at 1158 AM MST Sat Jan 20 2018 The upper low will be lifting northeast into Kansas Sunday night with a diminishment of snowfall from west to east across the northeast plains. There will still be strong northwest winds over the plains with gusts in the 40-50 mph range through the evening so will be holding on to the warnings through 8 pm there. Have increased winds over the plains for Sunday evening. For Monday and Tuesday, expect a moderate northwest flow aloft regime to set in over Colorado in the wake of this weekends storm system. There appears to be enough moisture and weak ripple in the flow to keep scattered snow showers going in the mountains but amounts will be on the light side. Given the mid level flow, still expect a fair amount of winds over the mountains and east slopes, mainly in the 30-50kt range. For Wednesday and early Thursday, high pressure ridge aloft will build over Colorado, before shifting east of state late Thursday. Expect a warming with readings back into the 40s and lower 50s by Wednesday and Thursday. Some of this warming will still depend on how much snow cover is still lingering. The next storm system is poised to translate across Colorado Thursday night through early Saturday time frame as an open wave with the brunt of the energy from Colorado and northward. Long range models are similar with the general overall solution but there are still some differences in amplitude and timing amongst them. Will keep forecast as is with chance pops and cooler temperatures, but won't fiddle much with details this far out. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 1158 AM MST Sat Jan 20 2018 Northeast winds continue at all airports with cooler air moving in and increasing low level moisture. Low clouds with ceilings of 1000 to 3000 feet are expected to form around 03Z. Clouds will continue to lower through this evening. Eventually, freezing drizzle is expected to form around 04-06Z with ceilings falling below 1000 feet. Freezing drizzle will change to snow between 09Z and 12Z. Snow will then persist through most of Sunday. The heaviest snow is expected to occur Sunday morning and into the early afternoon. Total snowfall for the upcoming storm through Sunday evening for the Denver airports is expected to be in the 5 to 8 inch range. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning from midnight tonight to 8 PM MST Sunday for COZ046-048>051. Winter Storm Warning from 6 PM this evening to noon MST Sunday for COZ031-033>036. Winter Weather Advisory from 6 PM this evening to noon MST Sunday for COZ030-032. Winter Storm Warning from midnight tonight to 5 PM MST Sunday for COZ039>042-044-045. Winter Storm Warning from midnight tonight to 2 PM MST Sunday for COZ038-043. Winter Weather Advisory from 8 AM Sunday to 5 PM MST Sunday afternoon for COZ047. && SHORT TERM...Kriederman LONG TERM...Entrekin AVIATION...Kriederman
Hazardous Weather Outlook...DELAYED National Weather Service Denver/Boulder CO 1102 AM MST Sat Jan 20 2018 COZ030>051-211815- 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- 1102 AM MST Sat Jan 20 2018 ...WINTER STORM WARNING FOR MUCH OF NORTH CENTRAL AND NORTHEAST COLORADO TONIGHT AND SUNDAY... This hazardous weather outlook is for northeast and north central Colorado. .DAY ONE...Today and Tonight A Pacific storm system will bring snow the mountains of north central Colorado this evening and continuing overnight. Snowfall rates over the mountains will increase to 1 to 2 inches per hour after midnight, producing snowpacked and icy roads. Meanwhile, freezing drizzle is expected to develop this evening over parts of northeast Colorado, including the urban corridor before changing to snow late tonight or early Sunday morning. This will make roads already slippery before the brunt of the snow comes later Sunday. Adjust your travel plans if possible, or make sure your vehicle has emergency supplies. .DAYS TWO THROUGH SEVEN...Sunday through Friday Snow will spread across the plains early Sunday. The heaviest snow will shift from the mountains and Denver and the other Front Range cities in the morning, onto the plains in the afternoon. There will still be areas of freezing drizzle on the far plains early Sunday morning before turning to all snow towards noon. The winds will also increase during the morning, with wind gusts of 30 to 40 mph common in most areas by afternoon, and gusts up to 50 mph possible over the eastern plains. These winds will create blowing and drifting snow. Blizzard conditions are possible Sunday afternoon on the eastern plains and road closures are possible. Storm total snowfalls in the higher mountains will generally be 6 to 12 inches, with localized amounts up to 18 inches. Elsewhere accumulations will range from 4 to 10 inches, with the lighter amounts expected in the mountain parks and around Fort Collins and the heavier amounts likely south and east of Denver. Weather conditions will improve Sunday evening as the storm system moves east of the area, though winds may continue to produce drifting snow on the plains through the night. The next chance of significant snowfall will be next Friday. .SPOTTER INFORMATION STATEMENT... Reports of snowfall or icing will be appreciated.
The national radar mosaic for the moment the first event began.
5 winter storm. Local standard time, as filed.
Storm totals ranged from 8 to 17 inches.
Storm totals ranged from 6 to 11.5 inches.
Storm totals ranged from 5 to 8.5 inches.
Storm totals ranged from 4 to 8 inches.
Storm totals ranged from 4 to 7.5 inches.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2018Every state in 2018This day in weather historyWarnings in Colorado, January 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: 735576, 735578, 735577, 735928, 735951.