Issue Date: Tuesday, August 9th, 2022
Issue Time: 10:30 AM MDT

— Flooding is NOT expected today

The high-pressure ridge continues to strengthen this morning with the center of the High now located over the Colorado and Utah border, as marked in the visible satellite image below. The ridge is expected to limit the monsoonal moisture return and suppress storm development this afternoon; thus, drier conditions are expected overall. This morning, Grand Junction measured a PW of 0.61 inches and Platteville measured a PW of 0.83 inches, both of which indicate an overall decrease of moisture compared to yesterday. Still, residual surface moisture remains elevated across eastern Colorado as dew points are noted above 50°F. Western Colorado is largely dry at the surface with dew points measured only in the 30s and 40s°F primarily, except for far southwest Colorado where a few dew points in the low 50s°F are noted.

Significant mixing out of surface moisture is forecast this afternoon, particularly across northern and central Colorado. Southern Colorado may be able to cling onto some moisture, especially as upslope flow increases this afternoon to help with moisture return. Additionally, the early morning stratus deck over eastern Colorado has eroded which should allow ample surface heating and moderate instability to build this afternoon. Currently, surface-based instability is forecast to reach values of 500-800 J/kg of CAPE across south-central and southwest Colorado, with values of 1000-1500 J/kg of CAPE possible across far eastern Colorado this afternoon. This should allow isolated to widely scattered storm development over the southern high terrain and Southeastern Plains by this afternoon.

A weak convergence boundary is located over southeast Colorado which should help trigger isolated to a few widely scattered storms over the Southeast Plains. Faster steering speeds up to 25mph are forecast for eastern Colorado, which should limit the flood threat east, although a few briefly heavy downpours and strong winds are possible with stronger storms that develop over the higher elevation ridges or in association with the convergence boundary. Over southwest Colorado, slower steering speeds may allow a few storms to produce heavy downpours over a 30-minute period, but the shorter duration and smaller rainfall cores should limit the flood threat. Flooding is NOT expected 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: 

Southwest Slope, San Juan Mountains, San Luis Valley, Grand Valley, Central Mountains, Northern Mountains, & Northwest Slope:

Some patchy fog was noted in San Luis Valley earlier this morning, but it has cleared out with a little day time heating. This afternoon, a few isolated to widely scattered storms over the high terrain may produce 30-minute rain rates up to 0.8 inches and localized totals just shy of 1 inch over the San Juan Mountains and the eastern Southwest Slope. Although briefly heavy downpours may lead to brief runoff and light ponding, flooding is NOT expected today.

Primetime: 1PM to 11PM

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

By early afternoon, isolated to widely scattered storm development is expected initially over the southern Front Range and Southeast Mountains and western Palmer Ridge. These storms may produce 30-minute rain rates up to 0.5 inches. Given northeast steering flows, these storms should remain over the high terrain. Isolated storms may also develop over the southern eastern plains along a weak convergence line, and if they break the cap max 1-hour rain rates up to 1 inch would be possible. Briefly heavy downpours and gusty winds are forecast; however, flooding is NOT expected today.

Primetime: 2PM to 9PM

Issue Date: Monday, August 8th, 2022
Issue Time: 10:10AM MDT

— A LOW flood threat has been issued for the Southeast Mountains, Raton Ridge and portions of the Front Range, Southwest Slope, San Juan Mountains and Southeast Plains
— Fire-Burn Forecast Summary: 1 burn area under MODERATE threat, 1 burn area under LOW threat; click HERE for more info

This morning there are some ongoing showers and cloud cover over southeast Colorado with clear conditions elsewhere. The clear skies are partially due to the drier air mass that is being advected into the state from the northwest (dotted green line marking the transition between the two air masses). As the High moves slightly northwards today, the dry air will continue to rotate clockwise around the High, and it should start to mix out some of the surface moisture over eastern Colorado. PW at Grand Junction has dropped slightly to 0.78 inches, and over North Platte, it has dropped quite a bit to 0.72 inches. Between the decreasing moisture and building High, afternoon and evening thunderstorm activity should be remain isolated to nonexistent over the northern and central high terrain. Some mid-level energy moving through the northwest flow may help to spark an isolated storm or two over the Cheyenne Ridge and Northeast Plains, but with decreasing moisture, flooding is not expected as the storms move southward.

Higher surface moisture will likely be able to hold on across southern Colorado, and where there are clear conditions this morning or breaks in cloud cover after the ongoing morning rainfall, some stronger storms may develop. While moisture should decrease some over the southern Front Range, increased convergence will likely produce another round of late afternoon and early evening storms in this climatologically active region. Isolated heavy rainfall may be possible over these areas with the slow steering flows, enhanced convergence, and dew points remaining in the upper 50°Fs to low 60°Fs, so a LOW flood threat has been issued. There is also an increased flood threat if storms today track over saturated soils, both over eastern and 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:

Southeast Mountains, Front Range, San Juan Mountains, Southwest Slope, Raton Ridge, Urban Corridor, Palmer Ridge, Northeast Plains & Southeast Plains:

Isolated heavy rainfall will be possible over these southern zones later this afternoon and evening. Max 30-minute rain rates up to 1.4 inches/1.25 inches (east/west) and 1-hour rain rates up to 2 inches (east) will be possible. A LOW flood threat has been issued for isolated mud flows/debris slides over steeper terrains, road flooding and field ponding. Over the northern Front Range, an isolated storm or two may produce totals up to 0.3 inches, and over the eastern plains, a stronger storm could produce 1-hour rain rates up to 1.5 inches along with very strong outflow winds and hail.

Primetime: 1PM to 11PM

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

These zones should stay mostly dry today with isolated storms most likely to develop over the Central Mountains near the Continental Divide. Storm totals should remain under 0.25 inches. A couple storms may make it into the interior of the SLV with isolated totals up to 0.5 inches possible near the edges. Flooding is NOT expected. Afternoon high temperatures should reach into the 90°Fs for the lower elevations and 70°F/80°Fs for the mountain valleys.

Primetime: 2PM to 10PM

Issue Date: Sunday, August 7th, 2022
Issue Time: 10:40AM MDT

— The flood threat will persist into the overnight hours
— A HIGH flood threat has been issued for the Urban Corridor, Palmer Ridge, Southeast Mountains and Southeast Plains
— A MODERATE flood threat has been issued for the San Juan Mountains, Raton Ridge, Front Range and Northeast Plains
— A LOW flood threat has been issued for the Central Mountains
— Fire-Burn Forecast Summary: 1 burn area under HIGH IMPACT threat, 2 burn areas under HIGH threat, 1 burn area under MODERATE threat; click HERE for more info

There will be quite the pattern shift today as a trough passing to the north will flatten out the ridge. The ridge begins to rebuild itself back to the west by this evening, which should give storms more southerly (south) and easterly (north) movement this afternoon and evening. As the trough continues to move east throughout the day, it is expected to continue to push a weak cool front southward across the state. This boundary, as is typical during the summer, will likely stall somewhere over the Palmer Ridge, and may help to produce a couple severe thunderstorms over the plains later today. Post-frontal upslope flow is anticipated over the eastern mountains, and with the jet closer to the upper-level Low, slow steering flows for the numerous to widespread storms that develop will likely cause very heavy rainfall to be generated in their cores.

It is still quite moist over eastern Colorado with PW at Platteville measured at 1.02 inches this morning, and dew points in the upper 50°Fs to low 60°Fs. At North Platte, PW was measured at 1.73 inches, so there’s a strong, increasing moisture gradient over the eastern plains. Upslope flow across the plains is expected to hold this high moisture intact. With a well-defined warm layer depth, rainfall efficiency is expected to produce some high rain rates, and a couple round of storms could potentially increase totals, if they track over the same area. This will be mostly likely to occur over the mountains and immediate adjacent plains. Over the eastern plains, enhanced convergence over the elevated ridges and along the boundary may allow storms to anchor to an area and drop some very high totals over a 2 to 3 hour period. Due to the widespread nature of the heavy rainfall and efficient rain rates forecast, a HIGH flood threat has been issued. There will also be an increased risk for rapid rises in local streams/creeks, gulches and arroyos where the storms remain stationary and over impervious areas.

Drier air remains over northwest Colorado with PW at Grand Junction measured at 0.83 inches, which will keep rainfall chances low for the area again today. With the main moisture axis over the San Juan Mountains and mid-level lift moving through the flow, heavy rainfall is anticipated for the area. Saturated soils will increase the risk for mud flows, debris slides and excessive runoff. For this reason, a MODERATE 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 Plains, Southeast Mountains & Raton Ridge:

As storms move off the mountains this afternoon, they should encounter high moisture, which should allow for upscale growth. In addition to slow steering flows, storms are likely to develop along a boundary, which could cause heavy rainfall over the course of a few hours. Thus, this is an overnight threat with lighter showers likely lingering through tomorrow morning. Max 1-hour rain rates up to 3 inches and isolated storm totals up to 5 inches will be possible, so a HIGH flood threat has been issued. A couple stronger thunderstorms may develop which would be capable of producing large hail and wind, and wind should become the dominate threat by later this evening. Flood threats today include road flooding, heavy field ponding, flooding of low-lying areas, arroyos and rises in local streams and rivers. Do not attempt to drive through high water and be sure to stay tuned to your local NWS office for the latest on warnings that are issued.

Primetime: 1:30PM to Ongoing

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

Widespread heavy rainfall is anticipated with the storms that develop this afternoon. Initially over the mountains, storms should be more scattered, and as the move east into deeper moisture, upscale growth is expected. Some areas may receive rainfall from a couple storms, which would help to boost local storm totals. Max 30-min rain rates up to 2.2 inches and 1-hour rain rates up to 2.75 inches will be possible under the strongest storms that develop. Over impervious areas, this could cause excessive runoff, road flooding and rises in local streams, creeks and dry gulches. Over steeper terrain, mud flows and debris slides will also be possible. A HIGH flood threat has been issued. In addition to heavy rainfall, small hail and outflow winds could occur under the stronger thunderstorms that develop. Use caution near underpasses this afternoon/evening and do not attempt to drive through high water.

Primetime: 12:30PM to 11PM

San Juan Mountains, Central Mountains, Southwest Slope, San Luis Valley, Northwest Slope, Northern Mountains & Grand Valley:

Similar to yesterday, little to no precipitation is forecast over the central/northern portions of these zones with drier air remaining over the area. Further south, moisture and mid-level lift will allow scattered storms to develop over the high terrain favoring the San Juan Mountains for accumulation. Max 1 to 2 hour totals up to 1.75 inches and 30-minute rain rates up to 1.2 inches will be possible. With saturated soils over the area, there will be an increased risk for rises in local streams/creeks, road flooding, mud flows and debris slides. A MODERATE flood threat has been issued. Light showers may linger over the mountains tonight, but the flood threat should end a couple hours after sunset.

Primetime: 12:30PM to 4AM

Issue Date: Saturday, August 6th, 2022
Issue Time: 10:35AM MDT

— A MODERATE flood threat has been issued for the Palmer Ridge and portions of the Northeast and Southeast Plains
— A LOW flood threat has been issued for the Raton Ridge and portions of the San Juan Mountains, Front Range and Southeast Mountains
— Fire-Burn Forecast Summary: 1 burn area under MODERATE threat, 3 burn areas under LOW threat; click HERE for more info

Drawn in this morning’s visible satellite imagery is the elongated High to our east and an incoming trough from the west (orange dashed). Also marked in the image are the 60°F dew points, and PW values across the eastern plains are estimated as high as 1.4 inches. PW at Platteville was measured at 1.25 inches, which is quite high and about a quarter of an inch jump from yesterday. Back over western Colorado, PW at Grand Junction was measured at 0.85 inches with values increasing to an inch across the southern border. A quick way to sum up the moisture content – the monsoon moisture plume remains overhead. While the majority of the lift will remain west and north of the state today with the trough, there was a small shortwave noted in New Mexico (orange “X”), which is expected to move northwards. As it encounters daytime heating and the monsoon moisture, it should help to produce scattered storms this afternoon and evening favoring the eastern and southern high terrains for development. With southwest steering flows around the High, spillover of thunderstorms into the adjacent eastern plains is anticipated.

There will be a couple of areas to watch for the flood threat today. Over the mountains, portions of the Front Range, Southeast Mountains and San Juan Mountains may see isolated, heavy rainfall from a couple thunderstorms that develop. If storms (south) track over areas that have saturated soils, there is an increased likelihood for a mud flow, debris slide or excessive runoff. A LOW flood threat has been issued. Over the adjacent plains, enhanced convergence is forecast over the Palmer Ridge, an area with high atmospheric moisture content. So, upscale growth of storms are anticipated in this area with outflow boundaries likely initiating additional storm develop. A MODERATE flood threat has been issued with a LOW threat issued for the Raton Ridge. Stronger storms over these areas may generate road flooding, field ponding and flooding of low-lying areas. In addition to heavy rainfall, a couple storms over eastern Colorado may produce strong wind gusts and hail.

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: 

Palmer Ridge, Northeast Plains & Southeast Plains:

Heavy rainfall is anticipated with thunderstorms that move into portions of these zones this afternoon and evening. Initially some storms may pose a small hail threat with wind becoming that dominate threat later this evening. Upscale growth of storms is anticipated and could cause more widespread heavy rainfall over the Palmer Ridge, so a MODERATE flood threat has been issued. Max 30-minute rain rates up to 2 inches and 1-hour rain rates up to 3 inches will be possible. This could cause road flooding, field ponding and flooding of low-lying areas. Rainfall may linger overnight, but the flood threat should end a few hours after sundown. Tomorrow morning expect cloudy and cool conditions behind the passage of a cold front.

Primetime: 3PM to 2AM

Southeast Mountains, Front Range, Raton Ridge & Urban Corridor:

Storms are expected to be more isolated today, especially north with some mid-level drying and heating. Over this area, max 30-minute rain rates up to 1.25 inches will be possible for the stronger storms that can develop. Further south, max 30-minute rain rates up to 1.5 inches (mountains) and 2.25 inches (adjacent plains) will be possible. Over steeper terrains mud flow and debris slides will be possible, and excessive runoff may also cause road flooding, field ponding and rises on local streams/creeks. Storms may linger overnight further south with weak mid-level lift and moisture over the area. A LOW flood threat has been issued.

Primetime: 12:30PM to 2AM

San Juan Mountains, Central Mountains, Southwest Slope, San Luis Valley, Northwest Slope, Northern Mountains & Grand Valley:

Little to no precipitation is forecast over the central/northern portions of these zones with drier air over the area moving in with a small jet streak. Further south, moisture should be able to hang on and a couple stronger storms may develop capable of producing heavy rainfall. This could be problematic if they track over saturated soils. For reference, Lily Pond SNOTEL soils are about 65% saturated. Max 30-minute rain rates up to 1.2 inches and 1-hour rain rates up to 1.4 inches will be possible. A LOW flood threat has been issued. A few storms may track into the SLV with the southwest steering flow and isolated storm totals up to 0.5 inches may be possible along with strong outflow winds.

Primetime: 2PM to Midnight