Issue Date: Sunday, May 1^st, 2022
Issue Time: 9:40AM MDT

— Flooding is NOT expected today

In true Colorado fashion, Mother Nature decided to kick off the 2022 Flood Threat Bulletin season with some fireworks. As shown in the water vapor image below, a small but potent upper-level disturbance is currently positioned over the Great Basin. It will rapidly move eastward into Colorado today, inducing widespread precipitation, with the best coverage being over the northern half of the state.

The main limiting factor to heavy rainfall potential will be moisture. Morning Precipitable Water (PW) at Denver and Grand Junction measured a meager 0.28 and 0.29 inches, respectively. As the disturbance approaches Colorado, it will stage an impressive return of moisture via strong southerly flow. The best chance for isolated heavy rainfall will be over southeast Colorado, where by late afternoon PW will exceed 0.50 inches and perhaps approach 0.75 inches. However, the more notable threat will be severe weather in the form of large hail and tornadoes. Short-term heavy rainfall will be possible with these storms, but with rapid northeast steering flow of 35mph or greater, flooding is NOT expected.

Moving on to some great news, steady rainfall and higher elevation snow will increase in coverage during the late evening and overnight hours over most of Colorado’s higher terrain as well as northeast Colorado. Scattered elevated thunderstorms (yes, including thundersnow!) will also be possible especially over the Northeast Plains. By tomorrow morning widespread rainfall exceeding 1 inch is likely over the Northeast Plains, which will be most welcome for the region’s farmers after the dry, windy and dusty April over that part of the state.

Lastly, a Red Flag Warning is in place over parts of southern Colorado where warm temperatures, winds and low humidity will combine to elevate the threat of wildfire initiation and spread.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

Southeast Plains:

Becoming partly cloudy, warm and windy with isolated to scattered thunderstorms developing mainly over far eastern areas along the OK and KS border. Max 1-hour rainfall up to 1.4 inches is possible. However, flooding is NOT expected today.

Severe storms will also be possible with large hail and tornadoes being the main threats, along with damaging straight-line winds.

Primetime: 4PM through 8PM, then light/moderate rainfall during the overnight hours

Northeast Plains, Front Range, Urban Corridor, Palmer Ridge:

Becoming partly to mostly cloudy with seasonably warm temperatures. Rainfall and high elevation snow will develop during the late evening and overnight hours. Max 1-hour rain rainfall up to 0.8 inches mainly over far eastern areas towards the KS border. Max 24-hour rainfall up to 1.9 inches is expected along and north of the South Platte River. The snow level will drop to 7,500 feet by tomorrow morning. Flooding is NOT expected today.

Primetime: 8PM through the overnight hours.

Northern Mountains, Central Mountains, San Juan Mountains, Grand Valley, Northwest Slope:

Partly to mostly cloudy with seasonably cool temperatures. Rain and snow will develop during the overnight hours, mainly over the higher elevations. Max 1-hour rainfall up to 0.4 inches is possible early in the event. Widespread precipitation amounts of 0.25 – 0.5 inches are expected by tomorrow morning. Flooding is NOT expected today.

Primetime: 7PM through the overnight hours

Southwest Slope, San Luis Valley, Southeast Mountains, Raton Ridge:

Mostly sunny, warm and windy with a Red Flag Warning in effect for most of the area. Isolated to scattered rain and high-elevation snow showers are expected during the overnight hours, but coverage will be limited. Flooding is NOT expected today.

Primetime: 10PM through the overnight hours

It’s almost time to welcome back the Flood Threat Bulletin (FTB) Program! Beginning this Sunday (May 1st), subscribers will start to receive the FTB to their inbox each morning (more info below to sign up). In addition to the FTB, the Flood Threat Outlook (FTO) will return on Monday and Thursday afternoons, which will look at the potential flood threat over the next 15-days across the state. Next, the Fire Burn Forecast (FBF) for the 2022 season will highlight the daily flood threat over 11 high-risk burn areas across Colorado’s mountain terrain. The FBF table will also track rainfall totals and flood reports generated by the public. Reminder, you can report any flooding that you encounter using the “Report a Flood” tab at the top of this page or by CLICKING HERE. We’re very appreciative of any first-hand reports! We use these reports in our daily State Precipitation Map (SPM) where we track flooding events and rainfall that has occurred across the state. Reports generated by the “Report a Flood” tab will also be featured in our daily SPM posts. Finally, the SPM will be published slightly later this year (no later than 12PM), but this will allow us to include delayed reports of heavy rainfall, flooding, debris slides and mud flows.

New this year:

• Daily Fire Burn Forecast to now include 11 burn areas. The FBF will track flood reports and provide daily forecasts for 5 additional burn areas this season, which in addition to last year’s 6 locations, means 11 total burns area for this product. The burn areas included in the 2022 season are Calwood, Cameron Peak, Decker, East Troublesome, Grizzly Creek, Middle Fork, Morgan Creek, Pine Gulch, Spring Creek, Sylvan and Williams Fork. Head on over to the About the FTB tab if you’d like to see where they located are on an interactive map. The purpose of the FBF is to provide an early outlook for flood threat awareness, but all real-time Flash Flood Warnings will continue to be issued by your local National Weather Service office.
• Monthly streamflow tracking for select high-volume sites across the state. Locations that will be tracked can be seen in the image below. Any interesting trends with the data will be tracked in the FTO when the data becomes available in the first week or two of each month. We will also add a dropdown tab under the “Flood Threat Outlook” tab so you can access the streamflow tables at your convenience.

• The FTB headline will include a summary of FBF threats on elevated flood threat days. There will also be a hyperlink within the FTB headline summary that will allow you to click and be redirected to the dedicated FBF portion of the website for more information. This will allow users who have email subscription to see all headlines in their email.
• FTB threat GIS geojson file used in the maps will be available for download. If you would like to show this data for your application, please fill out the “Contact” portion under the “Subscribe” tab for more information.
• Technical training for the FTB products is tentatively scheduled for mid-June. We’ll use our social media accounts to announce the exact date for the training soon. To follow us on social media (Twitter and Facebook), you can search the handle @COFloodUpdates or click the respective social media image on the bottom bar of this website. Not a subscriber to our daily FTB emails, but are interested? Head to “Subscribe” tab at the top of this page or CLICK HERE.

Looking forward to serving you for Colorado’s upcoming rainy season!

Issue Date: Thursday, September 30th, 2021
Issue Time: 10:20AM MDT

This is the last scheduled Flood Threat Bulletin post for the 2021 season. The next FTB season begins on May 1, 2022. It has been a pleasure to serve you!

— Flooding is NOT expected today

Unsettled weather continues with cooler temperatures and plenty of cloud cover forecast over Colorado for the last day of September. The upper-level pattern is expected to split today, and another Low will become cut off from the main flow (Utah). This should help to hold slightly higher PW values in place over the western portion of the state (0.68 inches at Grand Junction this morning). Mid-level lift will rotate around the cutoff Low (orange “X”) as it traverses southward throughout the day. This vorticity maximum and remaining moisture is expected to spark a few rounds of showers over western Colorado with better coverage of precipitation south of I-70. Not confident that a lot of instability will be able to build, which should assist in moderating the rainfall rates. Nonetheless, some embedded convection may be possible and 2 to 3 hour accumulations will likely bring a good soaking to the area. As far as the flood threat for the area, rainfall over the southwest corner has been spotty with accumulations on the lower end the last couple of days. That means that soils in the region likely aren’t saturated yet, and they should be able to absorb a large portion of the rainfall today. The one exception is over the southern/eastern San Juan Mountains where a second round of precipitation tonight, driven by the jet, may help to boost 24-hour accumulations. Rain turning to snow tonight should help to limit the rainfall threat over the area as the snow line falls just below 10K feet. Outside of some nuisance ponding both during the overnight hours and this afternoon, flooding is NOT expected today.

Over the rest of the state, outside of isolated showers over the eastern mountains, it should remain dry. Forecasting below average temperatures today and for the cloud cover to hang around. Drier air is expected move into the plains this afternoon, which should allow some blue skies to break through for a few hours. This will help to increase afternoon high temperatures a couple of degrees over the region. Glad to see that the FTB will be ending on a fall-like note with another round of precipitation for western Colorado.

Today’s Flood Threat Map:

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

San Juan Mountains, Central Mountains & Northern Mountains:

A couple rounds of showers are anticipated today with the snow line sitting above 10K feet during the day and dropping to around 9.5K overnight. More widespread showers are anticipated over the San Juan & Central Mountains with more isolated PoPs forecast over the Northern Mountains. Max 1-hour rain rates up to 0.70 inches (south) and 0.45 inches (north) will be possible if some embedded convection can develop. Small hail could also accompany those stronger storms. Over the southern/eastern San Juan Mountains, 24-hour accumulations up to 1.60 inches may be possible with the overnight precipitation forecast. Outside of some possible nuisance road and field ponding, flooding is NOT expected today.
Primetime: 1PM to Ongoing

Grand Valley, San Luis Valley, Northwest Slope & Southwest Slope:

Best chance for rainfall in the valleys will be over the SLV and Southwest Slope. Spottier shower coverage is expected over the Grand Valley and only light showers/cloud cover are anticipated over the lower elevations of the Northwest Slope. Max 1-hour rain rates up to 0.50 inches (south) and 0.25 inches (central) will be possible. Storm totals by morning could reach up to 0.40 inches for the SLV, 0.90 inches for the Southwest Slope and 0.40 inches for the Grand Valley. Flooding is NOT expected today, although there could be increased runoff in the Grand Valley if storms track over an area with saturated soils.
Primetime: 1:30PM to Ongoing

Southeast Mountains, Front Range, Urban Corridor, Northeast Plains, Southeast Plains, Raton Ridge & Palmer Ridge:

Much cooler today without much rainfall forecast as drier air moves over most of the lower elevations. Weak upslope flow and some residual moisture may cause some isolated showers to develop over the eastern mountains this afternoon. The southern Southeast Mountains/Raton Ridge intersect may see some weak precipitation overnight as well. Totals over the next 24-hour period up to 0.60 inches (south) and 0.25 inches (north) may be possible. Cloud cover will likely remain present all day over the Urban Corridor and elevated ridges, but there could be some clearing over the eastern plains for a bit this afternoon. Flooding is NOT expected.
Primetime: 1PM to 3AM

Issue Date: Wednesday, September 29th, 2021
Issue Time: 10:30AM MDT

— A LOW flood threat has been posted for parts of the Urban Corridor, Front Range and Palmer Divide

When it comes to analyzing the heavy rainfall threat in Colorado, there are two factors that have significant predictive strength: moisture and dynamics. Very often, only one is present (today, it is dynamics), but in sufficient strength, one can overcome the other’s absence. Such is the case today. As shown in the visible satellite image below, a strong shortwave trough has begun to move into Colorado from the west. In response, a surface low pressure will be developing along the NM/CO border today, responsible for very breezy conditions over the lower elevations of eastern Colorado today. Precipitable Water (PW) at Grand Junction has increased to 0.89 inches this morning, while Denver is steady at 0.67 inches. However, PW is expected to slightly increase today, especially over eastern Colorado. Additionally, the moisture profile has changed to a moister boundary layer over the past 24 hours. This increases chances for moderate to heavy rainfall, especially east of the Continental Divide. The aforementioned surface low pressure will maintain a strong upslope flow east of I-25 over northeast Colorado. With plenty of morning breaks in the cloud cover, there should be enough sunshine to boost instability into the 800-1,000 J/kg range this afternoon. With the stronger dynamics, organization of storms will be likely today, which could lead to prolonged heavy rainfall at a given location. In all, there will be a ~3-5 hour window this afternoon and early evening where heavy rainfall could occur over the Palmer Ridge and surrounding area. A LOW flood threat has been posted for this area.

To the west of the Continental Divide, we expect more light to moderate intensity showers and weaker thunderstorms. Outside of fire burn areas, we do not expect flooding for western Colorado today. The rain/snow line will progress from the 10-11k feet level to 7.5-8.8k feet as colder temperatures aloft move into the state.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

Northeast Plains, Southeast Plains, Urban Corridor, Palmer Ridge and Raton Ridge:

Increasing clouds with scattered to numerous showers and thunderstorms developing early this afternoon and persisting into the late evening. Over the Palmer Ridge, max 30-minute rainfall up to 0.8 inches with max 1-hour rainfall up to 1.2 inches possible, and a LOW flood threat has been posted. For other regions, max 1-hour rainfall up to 0.8 inches possible. Hail up to 0.75 inches will be possible with the strongest cells this afternoon

Primetime: 2PM through 10PM

Northwest Slope, Northern Mountains, Front Range, Central Mountains, Grand Valley, Southwest Slope, San Juan Mountains, San Luis Valley and Southeast Mountains:

Mostly cloudy with scattered to numerous showers and weaker storms ongoing throughout the day, then diminishing during the late evening. Max 1-hour rainfall up to 0.8 inches (Front Range) and 0.6 inches (elsewhere). With multiple rounds of precipitation, up to 2.0 inch of total rainfall will be possible especially over the Front Range. Notable accumulating snow will be likely above 10,000 feet, so keep an eye on NWS products and CDOT road conditions.

Primetime: now through 9PM