Issue Date: Friday, August 5^th, 2022
Issue Time: 10:30AM MDT

— A MODERATE flood threat has been posted for parts of the Central Mountains and Northern Mountains
— A LOW flood threat has been posted for parts of the Front Range, Palmer Ridge, Southeast Mountains, San Juan Mountains, Grand Valley and Northwest Slope
— Fire-Burn Forecast Summary: 6 burn areas under MODERATE threat; 4 areas under LOW threat; click HERE for more info

Another active day of heavy rainfall is expected today, as monsoonal moisture has begun to spread north and east across Colorado. As shown the visible satellite image, below, the monsoonal upper-level ridge has shifted southeast of our state. This puts western Colorado in steady, southerly flow, transporting moisture laden air into our higher terrain. PW at Grand Junction jumped ~20% to 1.14 inches, continuing a stretch of well above normal readings. Further east, PW at the Platteville research site came in at 0.94 inches, also notably higher than yesterday. PW is expected to stay steady or increase over central and western Colorado today. With morning sunshine to boost temperatures and create widespread instability, we expect another round of scattered to numerous higher terrain storms. Activity will generally spread north of where it has been over the past 24-48 hours.

Dynamics-wise, a pronounced disturbance was noted along the NM border this morning (see visible satellite image). This is showing up as a bubble of cooler mid-level air, along with an associate surface circulation, albeit a weak one. This will trek slowly north today, acting as the main focal point for afternoon and evening activity. Meanwhile, very warm mid-level temperatures are again present over eastern Colorado. This will continue to favor subsidence, little to no storm activity and very hot surface temperatures. Daily temperature records could be broken for elevations below 5,500 feet over eastern Colorado, depending on the extent of any afternoon cloud cover.

So, to summarize, we expect scattered to numerous afternoon and evening storms, with the best coverage over the central and northern higher terrain today. With plenty of moisture, adequate instability and slow steering flow, another MODERATE flood threat is warranted today. This is further reinforced by the past few days of activity producing numerous reports of flash flooding, debris slides and mud flows. In short, wet soils are definitely beginning to play a part in enhancing the flood threat. Further east, storms will once again have a hard time forming. However, isolated to perhaps widely scattered activity is possible over the Northeast and Southeast Plains, especially closer to the foothills.

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:

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

Becoming partly to mostly cloudy with scattered to numerous showers and storms developing by mid-afternoon. Highest coverage will be over the northern and central higher terrain, above 7,500 feet. Max 30-min rain rates up to 1.4 inches and max 1-hour rain rates up to 2.0 inches will be possible, warranting a MODERATE flood threat for the central and northern higher terrain and a LOW flood threat for surrounding regions. For lower elevations, rainfall will be more spotty and lighter, along with a chance of gusty winds with the stronger storms.

Primetime: 1PM through 11PM

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

Mostly sunny and very hot today with near record heat possible for the lower elevations. Isolated to widely scattered storms are possible today, expecially near the foothills. Max 30-min rain rates up to 0.8 inches (west) and 1.2 inches (east) could cause nuisance ponding of roads and low-lying areas. However, flooding is NOT expected today.

Primetime: 2PM through 11PM

Issue Date: Thursday, August 4^th, 2022
Issue Time: 11AM MDT

— A MODERATE flood threat has been posted for parts of the Palmer Ridge, Urban Corridor, Southeast Mountains, Raton Ridge and San Juan Mountains
— A LOW flood threat has been posted for parts of the Front Range, Southeast Plains, Central Mountains and Southwest Slope
— Fire-Burn Forecast Summary: 1 burn area under HIGH threat; 1 burn area under MODERATE threat; 3 burn areas under LOW threat; click HERE for more info

Moisture continues to be in abundance over Colorado this morning, as the infamous monsoonal upper-level ridge hangs over our state (see water vapor image below). PW at Grand Junction measured 0.95 inches, down notably since yesterday’s 1.1 inches, but still well above normal. PW at the Platteville research site was 0.75 inches, also down from yesterday’s 0.86. However, a strong moisture gradient was present across southern and eastern Colorado today with PW as high as 1.3 inches along our eastern border and right around 1 inch along our southern border.

Nearly clear skies were observed over most of the state this morning, which will allow for a quick warm-up in temperatures and instability by late morning. A weak surface low pressure was noted over north-central New Mexico. This will likely help focus storm activity over our southern higher terrain today, which will be the prime area for heavy rainfall potential. With pockets of instability exceeding 1,000 J/kg CAPE by early afternoon, slow moving storms will carry the potential for 30-60 minutes of very heavy rainfall. A MODERATE flood threat has been re-issued for the climatologically favored Southeast Mountains, Raton Ridge and San Juan Mountains today for isolated flash flooding, debris slides and mud flows. Numerous mud flows have been reported over the past few days over the steeper terrain, implying that antecedent wet soils have been taking a toll.

Further north and east, the upper-level ridge is expected to strengthen slightly this afternoon, which will warm mid-level temperatures over northeast Colorado. This subsidence will promote very hot temperatures and be a major obstacle to storm formation. Nonetheless, a steady southerly flow should develop a strong Palmer Ridge meso-low (a.k.a. Denver Convergence Vorticity Zone). This convergence zone will likely fire off at least a few storms from the peak of the Palmer Ridge, possibly stretching northeast all the way to the Nebraska border. Although the threat will be more conditional with mixing out of the boundary layer favoring large dewpoint depressions, any storm that forms will have 2,000+ J/kg of CAPE instability to work with. Thus, a LOW flood threat is warranted for parts of the region, with a narrow MODERATE threat for the climatologically preferred Colorado Springs area.

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, Urban Corridor, Palmer Ridge, Southeast Mountains & Raton Ridge:

Sunny early then mostly cloudy with scattered to numerous showers and storms developing by early afternoon. Max 30-minute rain rates up to 1.6 inches with max 1-hour rainfall up to 2.6 inches warrants a MODERATE flood threat for the climatologically preferred higher terrain. Isolated flash flooding will be possible, along with the elevated chance of mud flows and debris slides given the antecedent wet soils. A LOW flood threat has been posted for adjoining areas.

Primetime: 12PM to 11PM

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

Mostly sunny early then partly to mostly cloudy with widely scattered (north) to numerous (south) showers and storms expected this afternoon and evening. Max 30-min/60-min rain rates up to 1.0/1.5 inches, respectively, warrant a MODERATE flood threat for southern areas for isolated flash flooding, and more importantly, debris slides and mud flows given wet soils.

Further north, storms will be more spotty with the ability for a quick 0.6 inches in 30 minutes, but flooding is NOT expected north of I-70 (outside burn areas).

Primetime: 12PM through 10PM

Front Range & Northeast Plains:

Mostly sunny early then very hot with isolated to widely scattered storms possible this afternoon. Max 30-minute rain rates up to 0.8 inches possible, but flooding is NOT expected today. Gusty winds could accompany the strongest cells.

Primetime:

2PM through 8PM

Issue Date: Wednesday, August 3rd, 2022
Issue Time: 10:20AM MDT

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

Yesterday’s shortwave is now over Nebraska (orange “X”) and behind the trough, northerly surface flow is helping to create some pockets of cooler temperatures over northern Colorado and the I-25 Corridor this morning. Today, over northern Colorado, subsidence behind the trough and building High pressure should help suppress rainfall activity with only isolated storms forecast across the Front Range. Moisture remains quite elevated across the state with dew points over the lower elevations, both east and west, in the 50°Fs. PW at Grand Junction was measured at 1.1 inches and over Platteville, measured at 0.86 inches. With upslope flow developing by early this afternoon, there shouldn’t be a reason for this moisture to mix out. In addition to high moisture, slower steering flows are forecast, which will return the flood threat.

One area of concern for flooding is once again the San Juan Mountains where several days of rainfall have caused soils to become saturated. With another round of afternoon and evening thunderstorms forecast for the area, isolated mud flows, debris slides and road flooding will be possible, so a LOW flood threat has been issued. Over eastern Colorado, if a storm or two is able to overcome subsidence along the Front Range (most likely south), heavy rainfall would be possible, so a LOW flood threat has been issued. Further south, better upslope flow and less subsidence will allow for scattered to numerous thunderstorms to develop by early afternoon over the mountains. For the most part, the storms should stick to the high terrain, but rainfall activity could occur over the immediate adjacent plains with slightly more westerly steering flow and outflow boundaries from the mountain storms possibly initiating additional convection. Due to the high moisture content of the atmosphere and slow steering flows, a MODERATE flood threat has been issued. In addition to heavy rainfall, stronger thunderstorms are likely to produce strong wind gusts and lightning along with small 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:

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

Storms should mostly stay over the high terrain today, but some spillover is possible onto the ridges and adjacent plains further south. Max 30-minute rain rates up to 1.5 inches and 1 to 2-hour totals up to 2.5 inches will be possible. A MODERATE flood threat has been issued. Less certainty about isolated storms over the Front Range, but if one or two develop, max 30-minute rain rates up to 0.9 inches and 1-hour totals up to 1.25 inches would be possible. For this area a LOW flood threat has been issued. Threats today include mud flows and debris slides over steeper terrains, road flooding, field ponding and rises in local streams and creeks. Light showers may linger overnight, but most rainfall activity should come to an end by midnight.

Primetime: 1PM to 12AM

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

It should stay mostly dry north today with some isolated rainfall activity possible over the high terrain of the Grand Valley and Northwest Slope. Isolated storm totals up to 0.85 inches will be possible, but most storms will produce wind and totals under 0.5 inches. Further south, the saturated soils are likely to take another hit from the scattered storms that develop with residual monsoon moisture. Max 30-minute rain rates up to 1.1 inches and storm totals up to 1.5 inches will be possible. This could cause isolated mud flows and debris slides along with road flooding and rises in local streams and rivers. A LOW flood threat has been issued. The flood threat should end just after sunset, but some lighter showers may linger into tomorrow morning.

Primetime: 12PM to Ongoing

Issue Date: Tuesday, August 2nd, 2022
Issue Time: 10:55 AM MDT

— A LOW flood threat has been issued for the Northern Mountains, Northwest Slope, Central Mountains, Grand Valley, and San Juan Mountains
— Fire-Burn Forecast Summary: 4 burn areas under MODERATE threat, 4 burn areas under LOW threat; click HERE for more info 

The high-pressure system from yesterday has shifted further to the southwest as compared to yesterday, and it is currently centered over the New Mexico and Arizona borders, as shown in the visible satellite image below. This morning, the persistent northwest flow upper air pattern continues, but as the day continues expected a slight increase in overall westerly steering flow as the shortwave over Utah, marked by the “X” in the below image, moves eastward. Both surface and column moisture have increased a fair amount over western Colorado since yesterday with Grand Junction measuring a PW value of 1.22 inches this morning, which is just shy of the maximum moving average. Over eastern Colorado, the Platteville profiler measured PW of 0.86 inches, which is an increase from yesterday. Dew points are quite elevated indicating plenty of surface moisture with 50s°F for most of Colorado and low to mid-40s°F for the higher elevations.

While these numbers show an overall increase in moisture depth statewide, the deepening High pressure along with a midlevel dry air intrusion is expected to mix out some of the boundary layer moisture this afternoon, which should cause dew point values to fall to the mid-40s to low 50s°F for most of Colorado. Still, in the presence of ample surface heating instability is forecast to reach between 500-1000 J/kg of CAPE across much of eastern Colorado, and upward to 1200-1500 across southwest Colorado.

By this afternoon, scattered (north) to widely scattered (south) storm development is expected across portions of western and northern Colorado. Given the higher instability forecast and sufficient column moisture, convective storms are likely. Given the forecast faster steering speeds up to 20mph and deepening high pressure helping to promote subsidence and suppress storms, heavy rainfall should be brief, thus limiting the heavy rainfall to over 30-minute periods. A few rounds of storms are likely, and the stronger storm cores may produce heavy rain rates to exceed flash flood thresholds particularly where storms can anchor to the higher terrains. A LOW flood threat has been issued for portions of 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:

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

Aside from a few high clouds, skies are mostly clear across the western half of the state, which will allow plenty of instability to develop before the shortwave and upslope flow kick off storms. By early this afternoon, isolated to widely scattered storms are expected to develop over primarily the northern and central high terrains. Where any storms can anchor to the mountains, 30-minute rain rates up to 0.75 inches and 1 hour rain rates up to 1.25 inches are possible. A LOW flood threat has been issued for portions of the Northern Mountains, Northwest Slope, Central Mountains, Grand Valley, and San Juan Mountains. In addition to quick downpours, thunderstorms may produce some stronger outflow winds and small hail.

Primetime: Noon to Midnight

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

Skies are mostly clear this morning with hot temperatures expected to quickly rise this afternoon into the low to mid-90s°F and possibly even low triple digits over the eastern plains. This afternoon, a few isolated storms may drift across the mountains and adjacent foothills with increasing westerly steering flow. A few briefly stronger storms possible over the Northeast Plains and Palmer Ridge where max 30-minute rain rates up to 0.75 inches and 1-hour rain rates up to 1.25 inches will be possible. These storms are expected to be elevated due to the high dewpoint depressions, so they should pose more of a strong wind and lightning threat. NO flooding is expected today.