Locally strong wind gusts occurred in the Front Range mountains and foothills. Peak wind reports included 99 mph near Berthoud Pass and 83 mph near Glen Haven.
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The episode as NWS BOU wrote it up.
Locally strong wind gusts occurred in the Front Range mountains and foothills. Peak wind reports included 99 mph near Berthoud Pass and 83 mph near Glen Haven.
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 Dec 30, 9:00 AM MST, 3 hours 54 minutes earlier.
Area Forecast Discussion National Weather Service Denver/Boulder CO 900 AM MST Sat Dec 30 2017 .UPDATE... Issued at 859 AM MST Sat Dec 30 2017 Forecast updates from here through the rest of the day will focus around the arctic airmass and exactly how far it retreats to the east. At this time, the prospects for significant warming away from the foothills and Palmer Divide appears limited by persistent but weak easterly flow. There are pressure falls to our north which could aid the lee trough a bit, but stratus is holding surface heating down, and mixing is limited to elevations above 6000-6500 feet at this time. We will erode some of the stratus at least, so hopes for some warming exist in the Denver area but mainly western suburbs, and even then not sure about amount of warming. For now, have trimmed several degrees off the highs especially right near the foothills. Above 6000 feet across much of the foothills and Palmer Divide, many locations will reach the 50s and lower 60s. Mountains above 8500 feet will see 30s and 40s. Another arctic surge across the plains looks on track with more flurries across the plains and I-25 Corridor. && .SHORT TERM...(Today and tonight) Issued at 332 AM MST Sat Dec 30 2017 Mild Pacific air will stream over the Colorado in the west- northwest flow aloft. However, an arctic airmass backed into northeast Colorado last evening and overnight. Looking at observations in the foothills, appears the airmass goes up to about 7000 MSL in the northern foothills and is a little lower in the southern foothills and along the Palmer Divide. The cold airmass has produced low clouds and areas of flurries over northeast Colorado. This is expected to continue into the morning hours. Little to no snow accumulation is expected. The cold airmass is expected to retreat and erode along the edges today. There will be a very sharp temperature gradient where the Pacific airmass meets up with the arctic air. The lower foothills will approach 60 degrees today. Under the arctic airmass it will be much colder with readings in the teens and 20s. Over the far northeast corner of the state, single digit highs will be possible. Windy conditions will prevail in the mountains and foothills with gusts up to 60 mph. The arctic airmass surges southwest again tonight leading to more low clouds and flurries for northeast Colorado. Lows will fall into the single digits and teens. Mild conditions will continue above the arctic airmass in the foothills and mountains. Lift from the right entrance region of the jet combined with enough Pacific moisture may produce light snow over the northern mountains. Snowfall will be light and is expected to be less than 4 inches. .LONG TERM...(Sunday through Friday) Issued at 332 AM MST Sat Dec 30 2017 Medium range models indicate little change in the high amplitude ridge-trough upper air flow pattern over the CONUS during the extended period, except for a gradual eastward shift in the west coast upper ridge. The 500 mb ridge axis starts out over California on Sunday and moves over Utah/Arizona by Friday. For the period Sunday through Wednesday, a powerful northwest flow aloft will remain over Colorado. Sunday morning, weak lift produced by the tail end of an 80kt mid-level jet speed max and light northeast upslope flow may produce pockets of snow flurries/very light snowfall from the Front Range mtns eastward. Due to the lack of moisture with this feature, any snow amounts will be minimal and confined to the highest elevations. Even there, don't expect to see more than an inch of snow at best by afternoon. Most if not all of this precip should exit the CWA with the jet by early to mid afternoon. Otherwise, low clouds blanketing the plains will be slow to erode, making for a very cold day, especially acrs the northeast corner where max temps should remain in the single digits. Highs closer to the foothills are expected to reach the low to mid 20s, with even warmer highs in the 30s for the high country. The combination of a 5-8 mph sfc wind and temps in the single digits will produce very cold wind chills on the northeast plains late Sunday night/early Monday morning, especially out near the northeast corner of the state where we could see wind chills of -20 to -25 deg f for a few hours around sunrise. New Year's Day and Tuesday, temperatures warm slightly on Monday, then make a big jump back to near seasonal norms on Tuesday with the Arctic air being flushed out by a warmer south-southwest low-level gradient flow. Models show a buckle in the swift nwly flow aloft passing over nern Colorado Monday night/early Tuesday morning. It possesses some meager lift and just enough moisture to generate a mid-level deck of cloud resulting in milder overnight temps. Another reason for the warmer temps on Tuesday. Other than a few flurries in the high country, system looks dry. Wednesday also looks dry and not as windy in the high country. Temps also a deg or two warmer with strong subsidence aloft. Thursday into Friday, mid-level moisture wrapping around the top of the upper ridge inching closer to Colorado is fcst by most models to spread over the high country late on Thursday and out over the plains by Friday morning. Could see winds increase as well in the high country along with a good chance of snow. Plains may see a few snow showers around as well. Temperatures should continue to inch up esply east of the mtns both days with a downslope gradient flow in place. && .AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon) Issued at 859 AM MST Sat Dec 30 2017 Low clouds, light fog, and flurries will likely persist at KDEN and KBJC through 19Z-20Z before slowly breaking up this afternoon. KAPA on the edge of stratus deck now already. Timing of stratus breakout program suggests about 20Z at KDEN barring any easterly wind enhancement due to increased baroclinic zone/differential heating across the Palmer Divide. The arctic airmass will return to the area tonight with low clouds, flurries, and possible light fog returning to most areas by 06z. Once the low clouds return Saturday night, they are expected to prevail through Sunday. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && UPDATE...Barjenbruch SHORT TERM...Meier LONG TERM...Baker AVIATION...Barjenbruch
Hazardous Weather Outlook National Weather Service Denver/Boulder CO 1111 AM MST Sat Dec 30 2017 COZ030>051-311815- 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- 1111 AM MST Sat Dec 30 2017 This hazardous weather outlook is for northeast and north central Colorado. .DAY ONE...This Afternoon and Tonight Warm, windy, and dry conditions will prevail in the foothills today where gusts to 60 mph will be possible. Fire danger may be elevated on south facing slopes. Meanwhile, an arctic airmass will bring cold temperatures across the eastern plains. Denver will be caught in between with colder temperatures on the northern side of metro area and warmer temperatures on the south side. For tonight, areas of light snow and flurries will return to the plains with another surge of arctic air. Low temperatures will drop into the single digits over most of the plains. A couple inches of snow can also be expected over the mountains as a weak upper level disturbance passes by. .DAYS TWO THROUGH SEVEN...Sunday through Friday Very cold temperatures will persist through New Year's Day with light snowfall possible in the mountains and a slight chance of flurries on the plains Sunday morning. Only minor snow accumulation is expected at the highest elevations. Strong and gusty winds will also continue on the mountain ridges and east slopes of the Front Range through Monday night where blowing snow can be expected in open areas. On the plains, the combination of air temperatures near zero and a 5 to 10 mph wind will produce very cold wind chills early Monday morning, possibly as low as 25 below zero for a few hours near the northeast border of the state. Temperatures will then warm for the remainder of the week. There is a slight chance of light snow for the high country Friday with Pacific moisture moving in from Utah. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today or tonight.
The national radar mosaic for the moment the first event began.
2 high wind. 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, December 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: 730806, 730807.