Issue Date: Monday, June 28th, 2021
Issue Time: 9:40AM MDT

— A LOW flood threat has been posted for parts of the Front Range, Palmer Ridge, Central Mountains, San Juan Mountains and Southeast Mountains

A persistence-type weather pattern continues over Colorado for today. The trough of low pressure has moved only slightly eastward over the past 24 hours, and near-surface and column moisture remains virtually unchanged. This morning’s PW at Denver dropped slightly from 0.72 to 0.69 inches, while Grand Junction stayed unchanged at 0.64 inches. The main difference in today’s weather setup is the presence of more widespread cloud cover over southeast Colorado due to a cut-off low over New Mexico. This will tend to suppress heavy rainfall over the southern portion of the Southeast Mountains today. However, aside from that, the persistence pattern warrants the continuation of a Low flood threat over the higher terrain of southern and central Colorado. A moist atmospheric column, instability up to 700J/kg and sufficient southerly wind shear will support 30-60 minute bursts of heavy rainfall up to 1.0 inch per hour. This is capable of causing isolated flash flooding, debris flows and mud slides over steeper terrain. East of the Continental Divide, away from the higher terrain, a slight decrease in rainfall activity is expected due to weak subsidence to the west of the low pressure trough.

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 Mountains, Front Range, San Juan Mountains, Central Mountains & San Luis Valley:

Becoming mostly cloudy with scattered to numerous showers and thunderstorms increasing in coverage this afternoon. Max 30-minute rainfall up to 0.7 inch, with max 1-hour rainfall up to 1.0 inch. A Low flood threat has been posted over the region for isolated flash flooding, debris slides and mud flows mainly over steeper terrain.

Primetime: 11:30AM through 9PM

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

Mostly sunny early then turning mostly cloudy with scattered showers and thunderstorms, mainly limited to the higher terrain and adjacent foothills. Max 30-minute rainfall up to 0.5 inches and max 1-hour rainfall up to 0.8 inches. Flooding is NOT expected today, but nuisance urban street ponding is possible under stronger storm cores.

Primetime: 12PM through 8PM

Northern Mountains, Grand Valley, Northwest Slope & Southwest Slope:

Mostly sunny early then isolated to scattered showers and weak thunderstorms possible this afternoon. Max 30-minute rainfall up to 0.4 inches possible. Flooding is NOT expected today.

Primetime: 12PM through 7PM

Issue Date: Sunday, June 27th, 2021
Issue Time: 10AM MDT

— A LOW flood threat has been issued for the Southeast Mountains and portions of the Front Range, Central Mountains and San Juan Mountains

Not much change in the overall pattern today as Colorado continues to reside on the east side of a strong High pressure system over the Pacific Northwest. The trough overhead will build the northeast throughout today, which will produce northerly steering flow for storms over western Colorado and the mountains and then northwest/westerly flow over the eastern foothills/adjacent plains. Elevated moisture also remains over the area, although there is a slight decrease from yesterday. More so west of the Continental Divide. PW was measured at 0.72 inches in Denver and 0.64 inches over western Colorado. There is a second pocket of moisture across the southern border, which is producing some rainfall over the Raton Ridge this morning. In addition to the diurnal flow pattern sparking scattered afternoon storms over the mountains, a well-defined shortwave (orange “X”) will move through the northerly flow from Wyoming this afternoon. The incoming lift and moisture boost should help to produce more numerous storms over the mountains with training storms helping to increase local accumulations as seen over the last couple of days.

That brings us to the flood threat for today. It has rained a lot over the mountains the last couple of days. Yesterday, the northern Southeast Mountains and Wet Mountains received between 1 and 1.50 inches of rainfall with totals around 0.75 inches across the southern Front Range. On Friday, the southern Front Range saw the 1 to 1.50 inch rainfall totals. Some stronger storms are also possible this afternoon over the southern San Juan Mountains, which have received between 0.75 and 1.00 inches over the last 48-hours. So, with another round of rainfall expected over these same regions this afternoon, the threat for mud flows, debris slides and excessive runoff increases within the steeper terrains. Thus, a Low flood threat has been issued.

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 Mountains, Front Range, San Juan Mountains, Central Mountains & San Luis Valley:

Over the Southeast Mountains and Front Range, max 1-hour rain rates up to 0.60 inches will be possible with general storm totals between 0.60 and 0.90 inches. Over the Central Mountains and San Juan Mountains near the Continental Divide, max 1-hour rain rates up to 0.60 inches are forecast with storm totals just under an inch (south) possible. The interior/exterior San Luis Valley will likely see totals up to 0.45 inches/0.60 inches.

Another round of rainfall paired with antecedent precipitation over the last 48-hours mean saturated and loosened soils over these steeper terrain regions. Thus, the forecast rainfall this afternoon will increase the threat for mud flows, debris slides and excessive runoff in local streams/creeks. So, a Low flood threat has been issued. Rain turns to snow by this evening for the highest elevations, which should decrease the flood threat after about 8PM.

Primetime: 11:30AM to Midnight

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

Similar to yesterday, the more westerly component to the steering flow will push storms off the mountains and ridges by early afternoon. Additional storms will likely move into the Northeast Plains from the north later in the day. While some thunderstorms may develop with hail and brief outflow winds, severe storms are not expected at this time. Max 1-hour rain rates up to 0.75 inches will be possible over the ridges with storm totals around 1 inch. The far eastern plains will likely see storm totals around 0.75 inches. Some storms over the Southeast Plains & Palmer Ridge may linger through tomorrow morning. Flooding is NOT expected.

Primetime: 2PM to Ongoing

Northern Mountains, Grand Valley, Northwest Slope & Southwest Slope:

With the decrease in moisture over the area and northerly component to the steering flow, no rainfall is forecast this afternoon over the lower elevations. Some afternoon showers will likely develop over the Northern Mountains near the Divide, but totals should remain under 0.40 inches. Light rainfall is also possible over the Northwest Slope this evening from storms moving across the northern border. Flooding NOT forecast today.

Primetime: 3PM to 9PM

Issue Date: Saturday, June 26th, 2021
Issue Time: 9:45AM MDT

— Flooding is NOT expected today

Cloudy start to the morning with mid-level energy and moisture over the state. The visible satellite imagery below also shows some ongoing showers from last night that are making their way south across the western Southeast Plains and Southeast Mountains. Today, the positively tilted trough is forecast to sit overhead as a vorticity maximum (orange “X”) digs SSE, which will produce northerly and NNW flow aloft over most of the state. Those ongoing showers will likely dissipate over the adjacent plains throughout the morning but increase over the Southeast Mountains with a little daytime heating. Not much instability will be able to build due to the cold cover and cooler temperatures, so more stratiform rain with a little embedded convection is forecast. This is expected to produce a nice soaking for the area with the continued elevated moisture.

As upslope flow and mid-level lift organize with a little daytime heating, additional scattered storms are expected to pop over the mountains around noon or shortly after. The northerly steering flow should help keep storms over the mountains and elevated ridges through mid-afternoon. Then, a more westerly component to the steering flow is expected push the rainfall into the immediate, adjacent eastern plains. While moderate rainfall accumulations are forecast along and near the Continental Divide (north) and Southeast Mountains/southern Front Range (south) rainfall should be gradual enough that only nuisance flooding issues such as runoff and light ponding are forecast. Storms will start to diminish after the sunset from north to south, but some lingering showers are possible over the Southeast Mountains and San Luis Valley through tomorrow morning. Flooding is NOT forecast.

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 Mountains, Palmer Ridge, San Luis Valley & Raton Ridge:

Storms will start to pick up over the Southeast Mountains and additional storms will form over the elevated ridges (west) by noon. Over the ridges (especially north) a little convection may occur with max 1-hour rain rates up to 0.50 inches possible. Continuous rainfall over the Southeast Mountains could produce a couple storm totals around 1.50 inches near the Wet Mountains with many areas receiving an inch of rainfall. Overnight showers will likely linger over the mountains. Rainfall should be gradual enough that flooding is NOT expected outside of some nuisance ponding and runoff. The San Luis Valley should also get some measurable rainfall today, and the interior valley could receive around 0.40 inches by morning.

Primetime: Continuous

Front Range, Central Mountains, Northern Mountains & San Juan Mountains:

Scattered storms are forecast to form over the mountains by early afternoon and move south. Training and stationary storms are expected to produce higher accumulations long and near the Continental Divide (east). Rainfall should be gradual enough that flooding issues will be avoided outside of some nuisance ponding and runoff. Max storm totals up to 1.50 inch (Front Range), 0.60 inches (Central/Northern) and 0.60 inches (San Juans) will be possible. Flooding is NOT forecast.

Primetime: 11AM to 11PM

Urban Corridor, Northeast Plains & Southeast Plains:  

Showers currently occurring over the Southeast Plains will gradually end throughout the morning. Storm activity that begins over the mountains and ridges is forecast spill into the adjacent plains this afternoon. Max 1-hour rain rates up to 0.50 inches will be possible over the Urban Corridor. Some of this rainfall will likely move into the western Southeast Plains later today, but without much instability being able to build, severe storms are unlikely. Max 1-hour rain rates up to 0.60 inches will be possible. No rainfall is forecast for the Northeast Plains, and flooding is NOT expected.

Primetime: 3PM to 10PM

Grand Valley, Northwest Slope & Southwest Slope:

It should stay dry today with the more northerly steering flow over western Colorado keeping storms over the mountains. A couple storms could move off the San Juan Mountains into the eastern Southwest Slope and produce some light accumulations. Highs will be in the 80Fs for the valley locations, so it will be a beautiful day ahead. Flooding is NOT forecast.

Issue Date: Friday, June 25th, 2021
Issue Time: 10:40AM MDT

— A MODERATE flood threat has been issued for portions of the Front Range and Urban Corridor
— A LOW flood threat has been issued for the Northwest Slope, Grand Valley, Northern Mountains, Central Mountains, Southeast Mountains, Palmer Ridge, Northeast Plains and Southeast Plains

The moisture plume from the last couple days is still over the state, which can be seen by the blue and white shades in the water vapor imagery below and high dew points across the state (not shown). Dew points over northwest Colorado are around 50F (!), and Grand Junction’s morning sounding is still showing elevated moisture throughout the atmosphere with PW around 0.90 inches. It’s the same story over eastern Colorado with dew points in the mid to upper 50Fs and PW around 0.85 inches (Denver). As the state transitions into a weak trough pattern today, mid-level lift will increase over the area. This paired with the higher moisture will aid in the development of numerous storms over the mountains and elevated ridges by noon. Storms are expected to spill into the adjacent eastern plains by mid-afternoon and as they encounter higher instability (east), storms are expected to intensify. So, expect some severe thunderstorm over the far eastern plains that could produce strong outflow winds and large hail along with heavy rainfall. Early this evening, a weak cool front boundary will drop across the northern border, which will help to produce additional storms over the Urban Corridor, Palmer Ridge and eastern plains that are forecast to last into the overnight hours. So this is an overnight threat.

Training storms and additional storms sparked by outflow boundaries today are expected to produce high 30-minute rain rates and 2-3 hour accumulations, so a Low flood threat has been issued. Threats over the steeper terrains include mud flows, debris slides and road flooding. Although less convective storms are forecast overnight along the southern Front Range and Urban Corridor, persistent rainfall in the moisture-rich environment today and tonight are expected to produce local heavy rainfall with isolated 24-hour totals up to 2.75 inches by morning. Thus, a Moderate flood threat has been issued.

Please check the Fire Burn Forecast Page as there are several elevated threats issued for the burn areas today.

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: 

Front Range & Urban Corridor:

Storms today are expected to fire over the high terrains by noon and move into the Urban Corridor by mid-afternoon. Initially, the convective storms will be possible of producing 1-hour rain rates up to 1.25 inches with two hour totals just over 2 inches. Behind a cool front tonight, persistent upslope flow will produce another round of showers in the Moderate threat area. Isolated storm totals accumulations up to 2.75 inches will be possible by morning. Flood threats include road flooding and mud flows/debris slides over steeper terrains.

Primetime: 3PM to ongoing

Grand Valley, Northwest Slope, Central Mountains & Northern Mountains:

Scattered storms are forecast to develop over the elevated mountains and ridges by late this morning as a shortwave energy moves overhead. Max 1-hour rain rates up to 0.75 inches will be possible, and 2-hour totals from training storms could produce isolated totals up to 1.50 inches. Flood threats include mud flows, debris slides and road flooding over steeper terrains. Linger rainfall is likely over the mountains and Northwest Slope overnight. A Low flood threat has been issued.

Primetime: 11AM to Midnight

Palmer Ridge, Northeast Plains & Southeast Plains:

Ongoing rainfall over the northeast corner will continue and may intensify a bit this morning. Some severe thunderstorms are possible this afternoon further east where there is some better instability as storms move in from the west. The main threats from those storms will be heavy rainfall, large hail and strong outflow winds. Max 1-hour rain rates up to 1.75 inches (north) and 1.25 inches (south) will be possible. Training storms (north) may produce 2 to 3 hour totals up to 2.50 inches, which could cause local flooding of streams, road and field ponding. A Low flood threat has been issued. Late night storms/showers are possible over the Palmer Ridge, but rain rates should remain under 0.60 inches.

Primetime: 3:30PM to Midnight

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

Scattered afternoon storms are expected over these regions with more coverage east than west. Max 1-hour rain rates up to 0.40 inches are possible over the mountains with storm totals just over 0.50 inches possible (west). Over the Raton Ridge, max 1-hour rain rates up to 0.60 inches are possible. A second round of overnight showers are possible in the Southeast and San Juan Mountains, and flooding is NOT forecast.

Primetime: 1PM to 1AM