Bands of heavy snowfall developed over the mountains, foothills and adjacent plains of Boulder and Larimer counties. Multiple accidents occurred during the morning commute as the roadways became icy and slick.
Every event with a place to put it; 6 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.
Bands of heavy snowfall developed over the mountains, foothills and adjacent plains of Boulder and Larimer counties. Multiple accidents occurred during the morning commute as the roadways became icy and slick. Storm totals included: 11.2 inches near Allenspark, 11 inches in Poudre Park and near Estes Park, 10.9 inches, 4 miles east-northeast of Nederland; 10 inches near Crescent Village, 6.5 inches, 5 miles south-southwest of Morrison; 6.2 inches, 12 miles northwest of Golden; with 5.6 inches at Genesee. Along the I-25 corridor, storm totals ranged from 1 to 5 inches, heaviest from around Boulder north to Fort Collins.
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 Apr 3, 4:47 PM MST, 1 hour 13 minutes earlier.
Area Forecast Discussion National Weather Service Denver/Boulder CO 547 PM MDT Mon Apr 3 2023 .SHORT TERM...(This evening through Tuesday) Issued at 259 PM MDT Mon Apr 3 2023 A complex forecast over the next 36 hours or so as another storm system impacts our forecast area. A strong upper trough should progress from the northern Great Basin eastward towards the Black Hills by Tuesday afternoon. With both the 500mb and 700mb lows tracking along the CO/WY border, this isn't a particularly favorable storm track for moisture across the plains, though the mountains should benefit from another round of moderate to heavy snow. Regional radar and satellite data suggest snow is slowly developing across the high country this afternoon, and should continue to increase this evening into the overnight hours. A briefly heavier period of snowfall... with rates of 1-2" per hour, still looks likely tonight as strong 700-500mb frontogenesis and increasing QG ascent should aid in efficient snowfall growth. This mainly should impact the Park Range and Medicine Bow Range/RMNP, though some of the I-70 corridor could pick up a quick inch or two as well. As the upper low ejects into the plains, the flow aloft should shift to the west, and orographic snow showers should continue through the day Tuesday. Haven't made any changes to the highlights at this time. Meanwhile, a strong surface low is expected to develop along the eastern plains tonight/early tomorrow morning, with cold air filtering into the urban corridor behind it. There is considerable uncertainty in where this cyclogenesis occurs... with nearly a 250 mile spread between the HRRR (near Sterling) and some global models (somewhere between Pueblo and Springfield) by 12z Tuesday. These model differences have led to a low confidence forecast for most of the plains on Tuesday. Most of the American models have trended towards a drier solution for the morning, with a better push of moisture arriving later in the day. Some ECM/RGEM/GEM runs contradict this and have the main shot of cold air and light snow coming during the morning hours. With little consistency at this point, our current forecast lies somewhere in the middle. With a strong jet/frontogenesis nearby, it's always possible that a few spots (mainly Larimer county) benefit more than our deterministic forecast, and the evening shift will have to watch that potential. .LONG TERM...(Tuesday night through Monday) Issued at 259 PM MDT Mon Apr 3 2023 Tuesday night, the main upper level low will have moved to the north and east of the region. A front will have pushed through the region with northerly winds and cooler air behind it. Weak synoptic ascent lingers over the region during the evening with sufficient moisture. This will support the remaining showers to move across the high country. The cooler airmass behind the front should keep showers as snow. Northerly flow may provide some component of upslope to enhance showers slightly in the southern foothills and Palmer Divide. Overall, little accumulation is anticipated with 1/2 to 2 inches for the favored areas mentioned and no accumulation to a trace elsewhere for the lower elevations. Dry subsident air works in early Weds keeping the plains dry and decreases coverage of showers in the mountains through Weds AM. A weak shortwave embedded in the northerly flow aloft behind the previous system moves across the region Wednesday. Although weaker than the main upper low of the trough, this system brings a period of weak large scale ascent. Cross sections show limited moisture, but it will be enough for showers in the mountains. Model soundings show fairly steep lapse rates in the afternoon thanks to the Spring daytime heating. This will also help initiate scattered showers in the mountains and foothills. There is a chance (20-30%) showers to move onto the adjacent plains and Palmer Divide afternoon/early evening. Overall, accumulations, if any... are expected to be minor. Snow showers decrease overnight into Thursday. Ensemble guidance supports general weak ridging aloft moving into the region Thursday through the weekend. This will start a warming and drying trend with temperatures approaching 70s territory across the lower elevations by Saturday. && .AVIATION...(For the 00Z TAFS through 00Z Tuesday evening) Issued at 547 PM MDT Mon Apr 3 2023 A cyclone lifted northeast across the Denver area, passing just east of KDEN. Northwest winds to prevail behind it and then slowly back west to southwest this evening. For Tuesday, challenging part of the forecast is where the surface low will form. Models show anywhere from far northeast Colorado to southeast Colorado. Favor the southern trend, which means a sooner arrival of north winds/cold front and lower clouds for Tuesday morning. Expect the cold front to push through 11-12Z with lower clouds and hour or behind it or so. Ceilings of 2000 to 4000 feet are expected for most of Tuesday. Lower ceilings and visibility will accompany the snow showers. Better chance for this will be at KBJC and KAPA. && .FIRE WEATHER... Issued at 259 PM MDT Mon Apr 3 2023 Fire danger should decrease on Tuesday with much cooler and wetter conditions across the region. The exception to this may be Lincoln county south of I-70, which may stay just south of the cold front through the mid-afternoon. Some hi-res guidance supports a narrow window of Red Flag conditions and our current forecast grids support this as well. However, there still isn't enough confidence in how quickly/how far south the front will progress tomorrow morning, and thus we've held off on any mention of highlights. A warming a drying trend begins Thursday, extending into next weekend. For the most part, winds remain light. It will become quite dry with relative humidity values dropping into the 8-14 percent range for Lincoln County, South Park, Palmer Divide and Denver Metro. Friday through the weekend, winds over the Palmer Divide, South Park, and Lincoln County may be just below critical values, so elevated conditions can be expected in those areas. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until midnight MDT Tuesday night for COZ031. Winter Weather Advisory until midnight MDT Tuesday night for COZ033. Red Flag Warning until 8 PM MDT this evening for COZ214-216-241- 246-247. && SHORT TERM...Hiris LONG TERM...Mensch AVIATION...Meier FIRE WEATHER...Hiris/Mensch
Hazardous Weather Outlook National Weather Service Denver/Boulder CO 1103 AM MDT Mon Apr 3 2023 COZ030>051-041715- 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- 1103 AM MDT Mon Apr 3 2023 ...Critical Fire Weather Conditions Today... This hazardous weather outlook is for northeast and north central Colorado. .DAY ONE...Today and Tonight Critical fire weather conditions are expected this afternoon across the Denver metro, adjacent plains, South Park and southern Front Range foothills. Wind gusts up to 55 mph can be expected along with minimum humidities as low as 10 percent. Snow showers will increase across the northern mountains by later this afternoon, with the heaviest snow expected tonight. Expect winter driving conditions with icy and snowpacked roadways. A cold front will push southward over the plains later tonight with gusty northerly winds up to 35 mph. Snow showers will develop behind the cold front towards dawn on Tuesday. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday Periods of snow and slick travel conditions will continue in the mountains Tuesday and Tuesday evening, while the plains will see snow showers. A few of these showers may be briefly heavy Tuesday morning and then again Tuesday afternoon into early evening. Wednesday will feature continued much below normal temperatures, along with scattered but lighter snow showers. A prolonged warming trend with dry weather will start Thursday and continue through next weekend. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed. Any reports of strong winds and snow reports in the mountains will be appreciated.
The national radar mosaic for the moment the first event began.
4 winter weather, 2 winter storm. Local standard time, as filed.
Storm totals ranged from 8 to 11 inches.
Storm totals ranged from 6 to 11 inches.
Storm totals ranged from 3 to 5 inches.
Storm totals ranged from 3 to 5 inches.
Storm totals ranged from 3 to 6 inches.
Storm totals ranged from 1 to 3 inches.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2023Every state in 2023This day in weather historyWarnings in Colorado, April 2023
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: 1079893, 1079894, 1079895, 1079896, 1079897, 1079898.