Much of the Front Range Foothills, South Park, urban corridor and northeast plains were classified to be in severe to extreme drought (D2/D3) through the month of November. 07 inch and tied for the 2nd least snowiest November, with just a trace, also the 3rd warmest.
Every event with a place to put it; 16 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.
Much of the Front Range Foothills, South Park, urban corridor and northeast plains were classified to be in severe to extreme drought (D2/D3) through the month of November. For the month of November, Denver was the 10th driest on record with 0.07 inch and tied for the 2nd least snowiest November, with just a trace, also the 3rd warmest.
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 Oct 31, 8:34 PM MST, 3 hours 26 minutes earlier.
Area Forecast Discussion National Weather Service Denver/Boulder CO 934 PM MDT Sun Oct 31 2021 .UPDATE... Issued at 934 PM MDT Sun Oct 31 2021 Models continue to struggle with the finer details of the forcing aloft as little disturbances in weak flow produce clumps of showers that move over a pretty stagnant low level situation. The models had been showing the main shower band to be along and north of Interstate 80 in Wyoming and Nebraska, possibly sagging into the northeast corner of Colorado toward morning. Some runs also had a batch of showers further south moving right along the northern Colorado border between 00z and 12z. It looks like that feature is actually the current batch of showers, as there's not much sign of anything upstream. The broader scenario with the sustained weak deformation and low level convergence focused mainly north of the border still looks good. Resulting adjustments are: -- Higher PoPs from about I-70 north to the border, but mainly for light amounts through the early morning hours. -- Cooler temperatures tomorrow as the cloud cover should remain thick with gradual cold advection at the surface. --Adjustments to where we have a slight chance of freezing drizzle/rain. This will mainly be in the upslope areas after the forcing aloft is past, mainly near the northern border and especially north and northwest of Fort Collins with the east to southeast upslope winds. Between the light amounts and fairly warm ground, we're not expecting much impact with this, but it bears watching. We might also be a little bit too cold with the lows tonight since the cold advection is slight. In that case, there might not be much risk of freezing drizzle from Fort Collins southward because it will stay too warm. The Front Range cities are quite likely too warm for much impact from that anyway. && .SHORT TERM...(This evening through Monday) Issued at 250 PM MDT Sun Oct 31 2021 Radar is showing a few showers pushing eastward across the northern third of CWA at this time. The Stratus deck is cover all the plains and most of the foothills. The circulation center of the Denver cyclone is just north-northeast of DIA right now. Models keep the upper trough and associated surface high pressure to our north and northeast overnight an Monday. Upslope flow in the lower levels is expected to persist overnight and Monday. Moderate westerly flow aloft over the CWA tonight will become strong and west-northwesterly on Monday. There is a jet maximum over the northeastern corner of the CWA Monday afternoon. The QG Omega fields keep weak upward vertical velocity in place tonight and Monday. Cross sections indicate some potential instability, at least over the northern half of the CWA overnight into Monday. Moisture-wise, there is plenty progged on the cross sections, especially in the mid and upper levels. The low level moisture is fair over most of the CWA, but deeper over the northern border. I will put the highest pops in over the northern border in association with the jet max tonight and Monday. Will get some pops into the 40-60% range in the mountains on Monday with decent orographics and some moisture. Amounts do not look to hit highlight criteria. .LONG TERM...(Monday night through Sunday) Issued at 159 PM MDT Sun Oct 31 2021 ...UNSETTLED AND COOLER WEATHER CONTINUES THROUGH WEDNESDAY... Starting Monday night, the mountains and adjacent plains through Denver and the I-70 Corridor will be sitting in the right rear entrance region of an upper level jet streaking into northern Kansas. There may also be a weak surge of low level easterlies as high pressure continues to build across the Central Plains, coupled with a persistent but weak area of frontogenesis. As a result, we may very well see some banded precipitation stretch from the mountains eastward across the plains and I-25 Corridor. There is also some potential instability (PI) as seen in the cross sections of equivalent potential temperature. While all these parameters are favorable, the main uncertainty with regard to potential snowfall will be the amount of available moisture. Models are still showing rather limited amounts, which would hold back total precipitation amounts and keep them on the light side. For now, we've opted for the lighter precipitation amounts, but something still to watch over the next 24+ hours as a couple heavier bands could still develop. Another uncertainty will be p-type, as we will lean toward the colder NAM guidance considering current temp and cloud trends. This could bring some light snow accumulations to portions of the plains and I-25 Corridor, especially if we get some convective banded showers going. Mountain areas will see more widespread light snow with weak to moderate orographics and the marginal but sufficient moisture Monday night. We'll then see periods of snow continue in the high country through Tuesday and Tuesday night as another weather disturbance moves into the region. A Winter Weather Advisory may be needed for this period in the mountains due to the combination of deeper moisture, lift, and orographics. This next disturbance will also bring light precipitation to the plains as weak Q-G lift occurs. Most of this should fall in the form of rain in the lower elevations, however, as the airmass gradually modifies with lack of further cold advection. Looking ahead to later Wednesday into Thursday, models remain in agreement that a building upper level ridge will bring warmer and drier weather to Colorado. Then, the next disturbance may arrive toward Friday with a chance of showers and slightly cooler temperatures. Some ridging is expected next weekend, although we're not sure how fast Friday's trough axis will move off to the east, potentially slowing our warmup for the weekend. && .AVIATION...(For the 06Z TAFS through 06Z Monday night) Issued at 934 PM MDT Sun Oct 31 2021 MVFR conditions are expected in the Denver area through Monday. Showers and lower conditions will likely remain north of the city. Some light drizzle or brief rain or snow showers are possible. There's uncertainty about wind direction at KDEN/KAPA through Monday morning, but speeds will be under 8 knots. There should be a tendency toward light northeast winds during the day. && .BOU WATCHES/WARNINGS/ADVISORIES... None. && UPDATE...Gimmestad SHORT TERM...RJK LONG TERM....Barjenbruch AVIATION...Gimmestad
Hazardous Weather Outlook National Weather Service Denver/Boulder CO 1122 AM MDT Sun Oct 31 2021 COZ030>051-011730- 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- 1122 AM MDT Sun Oct 31 2021 This hazardous weather outlook is for northeast and north central Colorado. .DAY ONE...This Afternoon and Tonight Scattered light rain and snow showers should be developing late today into this evening. Heavier precipitation, mainly in the form of snow, will be likely be over the northern border area tonight. There may be a couple inches of snow accumulation by dawn Monday morning. This narrow band of slightly heavier snow may cause some travel impacts later tonight into Monday morning, mainly near the Wyoming and Nebraska borders. .DAYS TWO THROUGH SEVEN...Monday through Saturday Cool and unsettled weather will continue through Wednesday with light rain and snow showers. The majority of the accumulating snow will occur in the mountains, with a few inches of snow expected along with slick travel conditions especially over the higher mountain passes. The plains may also see some snowflakes mixed in, and a few spots could see light snow accumulations Monday night. Drier and somewhat warmer weather is expected Thursday into next weakened, although a few showers can be expected in the area Friday. .SPOTTER INFORMATION STATEMENT... Spotter activation will not be needed today or tonight.
The national radar mosaic for the moment the first event began.
16 drought. Local standard time, as filed.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
Severe to extreme drought classification (D2/D3) through the month of November.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Colorado in 2021Every state in 2021This day in weather historyWarnings in Colorado, November 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: 994164, 994165, 994166, 994167, 994168, 994169, 994170, 994171, 994172, 994173, 994174, 994175, 994176, 994177, 994178, 994179.