A long wave trough moved over Arizona with several short waves that produced snow and lower elevation rain. The snow level started above 7000 feet and then dropped through the event.
Every event with a place to put it; 3 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 FGZ wrote it up.
A long wave trough moved over Arizona with several short waves that produced snow and lower elevation rain. The snow level started above 7000 feet and then dropped through the event.
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 Flagstaff, AZ wrote its last area forecast discussion before the first event at Dec 23, 9:37 AM MST, 3 hours 23 minutes earlier.
Area Forecast Discussion National Weather Service Flagstaff AZ 937 AM MST Thu Dec 23 2021 .SYNOPSIS...Expect cooler temperatures and gusty winds on rain and snow showers increase across northern Arizona. Widespread rain and snow showers are expected by Thursday night, continuing into Christmas morning. Colder temperatures and rain and snow showers will continue into next week. && .UPDATE...The only real concern as of the morning update is the snow level for the coming storm. Successive model runs have turned colder bringing a 7000 foot snow level into play from about Happy Jack north and west. The models are just about 50/50 on the snow outcome. The general vertical temperature profile indicates rain but when the wet bulb effect and diabatic cooling from falling snow are considered a lower snow level is indicated. A Winter Weather Advisory is not out of the question for elevations above 7000 feet for portions of northwest Arizona. Travelers should be prepared for winter driving conditions and stay tuned for updates. The remainder of the forecast is on track. && .PREV DISCUSSION /428 AM MST/...Light showers have begun to spread across northern Arizona overnight. Little to no precipitation has been reaching the ground with dewpoints still in the 20s across much of the area. Expect moisture to increase through the day today as a longwave trough approaches the area bringing with it a subtropical moisture tap. Today into Saturday...Expect showers to spread across the area through the day Thursday starting along the high terrain before becoming more widespread area wide by late Thursday night continuing into midday Saturday. Amounts of liquid precipitation remain around 1 to 3 inches for rain and melted snow over the high terrain with 0.50 to 1.00 inches for the lower elevations. Snow levels will initially be high on Thursday around 8,000 to 9,000 ft. The conundrum in the forecast this morning is when the snow levels will drop overnight Thursday into Friday and by how much. The National Blend of Models runs overnight have lowered snow levels much faster as far south as Flagstaff and portions of the Mogollon Rim. Should this be the case, we may see a little more accumulation Thursday through Saturday for areas around 6500-7500 ft, especially along the Mogollon Rim. For now, have taken a conservative approach to blend snow levels and temperatures in with previous forecast. The trend has been a bit colder over the last few model runs but uncertainty remains high. Confidence remains high that areas above 7500-8000 ft will see heavier snow accumulations. A Winter Storm Warning has been issued for the Kaibab Plateau for areas above 7500 ft this morning for Thursday afternoon through midday Saturday. A Winter Weather Advisory has been issued for the Chuska Mountains for areas above 7500 ft including Buffalo Pass from late Thursday through late Friday night. Expect hazardous travel in these areas including slick roads and areas of blowing snow creating periods of low visibility. Winds will increase with gusts to 40+ mph. Stay tuned to the forecast as things are still developing. Showers look to lighten by late Saturday but continue off and on with snow levels dropping to around 6000 ft in the northwest and around 6500-7000 ft in the east. Sunday through Wednesday...A longwave trough remains in place across the southwest through early next week. Unsettled weather will continue with intermittent light showers across the upslope regions of northern Arizona. Additional snowfall is expected Saturday through Wednesday with the potential for an impactful winter storm by Wednesday through the end of next week. Stay tuned to the forecast as the next event continues to unfold. && .AVIATION...For the 18Z package...MVFR conditions develop after 03Z, with widespread rain/snow showers developing from west to east. Local areas of IFR conditions will be possible after 12Z within areas of heavier precipitation. Winds remain southwest 10-20 kts, with gusts 20-30 kts in the high terrain. Gains and losses of 35-45 kts will be possible in areas of LLWS between 06Z-12Z along and near a KGCN-KFLG-KJTC line. Aviation discussion not updated for TAF amendments. && .FIRE WEATHER...Cooler temperatures and breezy southwest winds are expected today, with increasing winds overnight and Friday. Widespread wetting rain and high elevation snow develops from west to east overnight, lasting into much of the day Friday, with showers lingering thereafter. Saturday through Monday...Precipitation chances gradually decrease over the weekend before increasing once again on Monday. Greater chances for accumulating snow exists through the weekend with cold temperatures expected. Breezy southwest winds are also expected to remain into the start of next week. && .FGZ WATCHES/WARNINGS/ADVISORIES...Winter Storm Warning until 11 AM MST Saturday FOR AZZ004. Winter Weather Advisory from 11 PM this evening to 11 PM MST Saturday FOR AZZ011. && PUBLIC...McCollum/ET AVIATION...Humphreys/JM FIRE WEATHER...Humphreys/JM For Northern Arizona weather information visit weather.gov/flagstaff
The national radar mosaic for the moment the first event began.
5 heavy rain, 3 heavy snow. Local standard time, as filed.
Heavy rain fell across Coconino County before turning to snow across the higher elevations. Amounts ranged from around an inch at the Grand Canyon to over 2.50 inches at Munds Park and Mormon Lake.
Heavy rain fell across Yavapai County with reports of one to three inches of rain.
Heavy rain fell across the upslope areas of southern Navajo County. Amounts ranged from less than an inch to 2.36 inches.
Heavy rain fell across northern Gila County. Rainfall amounts ranged from over an inch and a half at Payson to 2.80 inches just south of Washington Park.
Ten inches of snow fell by 900 AM at 8,080 feet about 13 miles northwest of the Flagstaff Airport. Snow continued to fall through the day.
Heavy rain fell across the lower elevations of Yavapai County. Just over an inch of rain fell in Black Canyon City in 12 hours.
Nine inches of snow fell at Sunrise Ski Park by 100 PM with snow ongoing.
Rain fell overnight (0.78) before turning to snow around 500 AM in Forest Lakes. Ten inches of snow then fell by 700 PM.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Arizona in 2021Every state in 2021This day in weather historyWarnings in Arizona, December 2021
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: 994654, 994651, 994652, 994653, 994645, 994626, 994644, 994643.