Rain and mountain snow showers moved across eastern Colorado during the afternoon and evening of May 4th. Widespread snow then formed over the mountains and northern foothills during the early morning hours of May 5th and continued for most of the day.
Every event with a place to put it; 8 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.
Rain and mountain snow showers moved across eastern Colorado during the afternoon and evening of May 4th. Widespread snow then formed over the mountains and northern foothills during the early morning hours of May 5th and continued for most of the day. Across the lower elevations (below 6000 feet), precipitation type was mainly rain through the morning of the 5th and slowly began to turn over to snow during the afternoon. Snow then continued through the night of the 5th and early morning hours of the 6th. The heaviest snow occurred across the foothills and mountains of Boulder and Larimer Counties where 18 to 36 inches of snow fell. Areas west of I-25 to the base of the foothills received 4 to 12 inches, heaviest near the foothills. Main impact was broken tree branches on deciduous trees, some of which fell on powerlines leading to sparse power outages. Power outages topped 50,000 overnight the 5th and early morning the 6th. Denver International Airport (DIA) had over 700 flight delays and 40 cancellations for May 5th and May 6th. Numerous schools were closed on May 6th.
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 May 4, 10:25 PM MST, 1 hour 35 minutes earlier. Its key messages:
Area Forecast Discussion National Weather Service Denver/Boulder CO 1125 PM MDT Mon May 4 2026 .KEY MESSAGES... - Scattered showers and thunderstorms this afternoon, gradually transitioning to steadier rain and snow tonight into Tuesday morning. - A significant snow storm will impact the mountains and foothills late tonight through Wednesday, most pronounced north of I-70 where the snowfall could be damaging and travel conditions exceptionally difficult at times. - Several inches of heavy/wet snow are expected late Tuesday into Wednesday for much of the I-25 corridor, especially on colder surfaces. Damage to tree limbs will be possible, as well as locally slick conditions for the Wednesday morning commute. - Return to a warmer pattern likely again by the latter half of the week. && .DISCUSSION /Through Monday/... Issued at 223 PM MDT Mon May 4 2026 Today's weather has progressed about as expected. A weak cold front has been the focal point for most of the showers and isolated thunderstorms so far today. This front continues to slowly sink southward, though the mid-level front is still rather poorly defined at this point in time. A gradual increase in fgen is expected later this evening/tonight, which will serve as the focal point for an east-west oriented band of rain/snow showers and perhaps an embedded thunderstorm or two during the overnight hours. As snow levels fall from >10kft this afternoon to ~7500ft by Tuesday morning, snow should begin to accumulate across the northern Front Range mountains and foothills. A complex winter (spring?) storm remains on track to produce significant snowfall across the forecast area Tuesday into Wednesday. As was the case yesterday, the overnight shift provided an excellent summary of the synoptic pattern through Wednesday evening. A majority of the discussion below will focus on a brief "state of the models" along with some forecast/impact uncertainties as we draw closer to the start of the event. All things considered, model guidance has remained relatively consistent over the past few forecast cycles. While yesterday's 12z suite had some rather aggressive QPF from a few deterministic models, ensemble mean QPF yesterday was around 1-2.25" across our forecast area... and that remains the case today. The main trend of note today has been to slow down the northern stream shortwave a touch, though this still eventually leads to a phase with part of the southern stream cutoff low. The main effect from this trend has been to hold on to snow a bit longer Wednesday morning or early Wednesday afternoon, which of course leads to more questions about impacts (more on that soon). The additional short term guidance available today also adds a bit more noise that could subsequently be interpreted as a general trend up/down in precip/snow. Still, even the short term models appear to be slowly converging towards the QPF range of the global deterministic/ensemble solutions. One thing not discussed in much detail so far is that a significant portion of the event is driven by mid-level convergence/frontogenesis before adding in some QG ascent (via positive vorticity advection) and a slow strengthening of upslope flow below 700mb. Banded precipitation events are notoriously difficult to forecast, where the exact location of a persist band of heavier precipitation typically sets up... but not exactly the way that higher resolution guidance may suggest. There will almost certainly be some sharp gradients in QPF/snow early on in the event that are not captured particularly well our deterministic, gridded forecast. I have far lower confidence in the forecast south of the Denver metro (southern Foothills, South Park, Palmer Divide) compared to places like the Highway 34 corridor for that reason. Finally, while forecast confidence in QPF is rather high, that does not lead to a high confidence forecast in impacts. First, the translation from QPF to snow is not very straightforward. Higher resolution guidance varies wildly with surface temperatures below 6500ft during the rain to snow transition Tuesday afternoon/evening. Is that a reflection of diabatic effects from falling precipitation (i.e., melting and/or refreezing), or a symptom of imperfect radiation/boundary layer schemes within the model itself? I would suspect it's probably a bit of both. The rain to snow transition remains pretty similar to our previous forecast and is perhaps a little conservative. We don't expect much accumulating snow before midnight for any of our lower elevation forecast zones. However, even after the snowfall begins... we still have several questions left to answer. How long will it take for snow to accumulate on surfaces? Trees? Roadways? This will likely be well correlated to snowfall rates... which are of course uncertain too. We have fairly high confidence in a couple of inches of snow accumulating overnight across the Denver metro, but questions don't end there. As noted earlier, the slower storm system leads to higher QPF amounts from roughly 12-21z Wednesday. Will additional snow manage to accumulate on the existing snowpack from the overnight hours? Even if snow simply compacts on itself, do trees/power lines feel the added weight of the snow, even if accumulations on grass and your patio furniture remain constant? Is it cold enough for snow to affect the morning commute? The answer to these questions may again be dependent on snowfall rates which will likely take another few cycles of higher resolution model cycles to get a better grasp on. That leads us to what most people are here to read about, the storm total snowfall forecast. Our forecast is once again nudged up a little, though that generally leads to about 3-7 inches of snow in the forecast. Generally 1-2 feet of snow looks on track for the Front Range foothills above 7500ft and north of I-70. Guidance still hints at a few pockets of closer to 2-3 feet, though this may be overdone with significant compaction likely through the duration of the event. While our forecast is actually a little lower than NBM/WPC guidance, it is a closer match to model positive snow depth change and the HRRR's variable density snowfall output.Given the considerable uncertainty in impacts across the I-25 corridor, we've left the Winter Storm Watch as is for now. The biggest change was to upgrade the southern Front Range mountains/foothills into a Winter Storm Warning with a slightly later start time (12 PM Tuesday). Snow is expected to wrap up quickly on Wednesday afternoon or evening as the upper trough axis slides off to the east and any upslope flow quickly diminishes. However, we'll have one night of "wintry" temperatures. Guidance over the last 24 hours has become far more bullish, tanking temperatures early Wednesday night into the upper teens to mid 20s across a large chunk of the I-25 corridor and plains. While we have had several nights near or just below freezing, the well below freezing temperatures was enough to justify a Freeze Watch for the lower elevations. By Thursday afternoon, guidance is in good agreement that the colder air will quickly retreat off to the north and east, as a ridge begins to build west of our forecast area. Temperatures should rebound into the upper 50s to 60s across the plains, though this may be somewhat dependent on how much snow is left to melt across the I-25 corridor and adjacent plains. The gradual warming trend is expected to continue into the weekend, with a few shortwaves rippling through the northwesterly flow aloft. With enough moisture lingering in the region, that should be enough for daily chances of showers and a few storms. We'll have to work out the timing for the better chances of precipitation here... but given the complexity of the short term forecast, NBM appeared to be good enough for now. && .AVIATION /06Z TAFS through 06Z Wednesday/... Issued at 1120 PM MDT Mon May 4 2026 A relative lull in -SHRA activity and by associated CIGS in the 030-060 range is expected over the next several hours for Denver area terminals, with most of the precipitation anticipated to stay to the north until closer to 10Z. Approaching sunrise, potential for development of -SHRA and -SHSN will return along with lower bases in the 012-020 range. Expect a steady decline in CIGS throughout the day Tue, along with gradually more consistent snowfall and lowering vis restrictions. Potential for 1/2SM in heavier SN increases notably after ~05-07Z tonight. For winds, currently quite light and variable but should transition to a more stable E/NE direction in the coming hours. Little chance in direction through the TAF period, through KBJC will likely stay more N vs NW as it remains on the NW side of DCVZ. Periods of stronger winds gusting up to 20 kts will be possible, particularly this morning. && .BOU WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory from 8 PM Tuesday to 3 PM MDT Wednesday for COZ030-032-037-043-045-046. Winter Weather Advisory from noon Tuesday to noon MDT Wednesday for COZ031. Winter Storm Warning until 3 PM MDT Wednesday for COZ033-035. Winter Storm Warning from noon Tuesday to 3 PM MDT Wednesday for COZ034-036. Winter Storm Watch from Tuesday evening through Wednesday afternoon for COZ038>041. Freeze Watch from Wednesday evening through Thursday morning for COZ038>051. && DISCUSSION...Hiris AVIATION...BRQ
The national radar mosaic for the moment the first event began.
8 winter storm. Local standard time, as filed.
An estimated 18 to 34 inches of snow fell based on estimates from SNOTEL sites.
Trained spotter reports and cocorahs reports show estimated 18 to 34 inches of snow fell. The heavier reports were in the Estes Park area with 17 to 31 inches reported. Photos showed snow covered roads and weighed down trees.
Reports indicated 6 to 15 inches of snow fell across the area.
Based on spotter and snotel reports, 7 to 16 inches fell across the area with the heavier snow falling east of the Continental Divide.
CoCoRahs and trained spotters reported 4 to 8 inches of snow. The heavy wet snow led to many broken tree branches and limbs, a few of which fell onto vehicles and homes. Broken branches also fell onto powerlines, leading to some power outages.
CoCoRahs and trained spotters reported 4 to 12 inches of snow. The heavy wet snow led to many broken tree branches and limbs, a few of which fell onto vehicles and homes. Broken branches also fell onto powerlines, leading to some power outages.
CoCoRahs and trained spotters reported 4 to 12 inches of snow. The heavy wet snow led to many broken tree branches and limbs, a few of which fell onto vehicles and homes. Broken branches also fell onto powerlines, leading to some power outages.
CoCoRahs and trained spotters reported 4 to 8 inches of snow. The heavy wet snow led to many broken tree branches and limbs, a few of which fell onto vehicles and homes. Broken branches also fell onto powerlines, leading to some power outages.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2026Every state in 2026This day in weather historyWarnings in Colorado, May 2026
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: 1323482, 1323485, 1323487, 1323486, 1323495, 1323492, 1323493, 1323494.