Issue Date: Thursday, July 28^th, 2022
Issue Time: 11AM MDT

— A HIGH flood threat has been posted for parts of the Southeast Plains, Southeast Mountains, Raton Ridge and San Juan Mountains
— A MODERATE flood threat has been posted for parts of the Front Range, Urban Corridor, Palmer Ridge, Central Mountains and Southwest Slope
— A LOW flood threat has been posted for parts of the Northeast Plains and Grand Valley
— The flood threat extends into the overnight hours
— A PM update is possible today
— Fire-Burn Forecast Summary: 4 burn areas under HIGH flood threat; 5 burn areas under MODERATE threat; 2 burn areas under LOW threat; click HERE for more info

As expected in the previous Outlooks, a very busy pattern for heavy rainfall has developed across Colorado. Although the subtle details change daily, the common ingredient has been ample moisture of monsoon origin. This morning, PW at Grand Junction measured 1.07 inches, and was well distributed through the atmospheric column. Across the Continental Divide, PW was measured at 1.15 inches at the Platteville research station northeast of Denver. Higher PW, up to 1.4 inches exists in far eastern Colorado. As shown in the water vapor image, below, high PW is also being imported into southern Colorado with values as high as 1.2 inches expected by later this afternoon.

The primary concern regarding today’s heavy rainfall potential is the widespread thick cloud deck across a large portion of the state. This will certainly limit the instability. However, with this much moisture in place, instability becomes less important if the entire atmospheric column becomes saturated and there is low-level convergence taking place (as is the case today). Dynamics-wise, an interesting confluent flow pattern is observed across Colorado with deep SSW flow over southern areas and NW/NNW flow across northern areas. In brief, the higher flood threat today will occur along and to the south of where these two streamlines meet. This will occur over southern Colorado, and several rounds of showers and storms are expected today. With relatively slow steering flow (slower flows towards the south), very heavy point rainfall is expected. In addition, prolonged rainfall will cause concern in the 3-6 hour duration, where over 3.0 inches is expected over parts of the San Juan Mountains and over 5 inches is possible along the KS border. In all, a HIGH flood threat is warranted beginning this afternoon and lasting into the overnight hours across southern areas. Further north, coverage over heavy rainfall will be more isolated, so a MODERATE/LOW threat is in place.

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, San Juan Mountains, Southwest Slope, Raton Ridge, Palmer Ridge, Central Mountains, Southwest Slope & Southeast Mountains:

Mostly cloudy early then numerous to widespread storms developing early this afternoon and lasting well into the overnight hours across far southern areas. Max 1-hour rainfall up to 3.4 inches over eastern areas and 2.5 inches over western areas. Max 6-hour rainfall up to 6 inches (far eastern areas) and up to 3.8 inches over western areas. A HIGH flood threat has been posted for parts of the region for the risk of flash flooding, debris slides and mud flows. There will also be a high threat of small stream and creek flooding, especially over steeper terrain.

Note that the flood threat will extend well into the overnight hours especially over the San Juan Mountains and Southeast Plains.

Primetime: Noon through 6AM

Front Range, Urban Corridor & Northeast Plains:

Mostly cloudy with scattered to numerous showers and storms developing this afternoon. Max 1-hour rainfall up to 2.8 inches. A MODERATE flood threat has been posted for the higher terrain, with a LOW flood threat over the eastern plains. Isolated flash flooding, debris slides and mud flows will be possible over steeper terrain.

Primetime: Noon through 10PM

Northwest Slope, Northern Mountains & Grand Valley:

Partly cloudy early then widely scattered to scattered showers and storms developing by early afternoon. Max 30-min rainfall up to 1.0 inch possible (especially over the southern higher terrain). A LOW flood threat has been posted for parts of the region for isolated flash flooding, debris slides and mud flows.

Primetime: Noon through 8PM

Issue Date: Wednesday, July 27^th, 2022
Issue Time: 11AM MDT

— A MODERATE flood threat has been posted for the Northeast Plains, Southeast Mountains and San Juan Mountains
— A LOW flood threat has been posted for parts of the Front Range, Urban Corridor, Palmer Ridge, Raton Ridge, Southeast Plains, Central Mountains and Southwest Slope
— The flood threat extends into the overnight hours over northeast Colorado
— A PM update is possible today
— Fire-Burn Forecast Summary: 1 burn area under HIGH threat; 2 burn areas under MODERATE threat; 4 burn areas under LOW threat; click HERE for more info

Heavy rainfall will be back in the picture today for many parts of Colorado, though the details are once again tricky to pin down. As shown in the water vapor image, below, the monsoonal upper-level ridge has now moved west over the past 24 hours and is located along the AZ/NM border. With northwest flow across northern Colorado, some subtle drying is trying to work its way over northern and northwestern parts of the state. But this will be limited as upslope flow turns moisture advection back to positive later this afternoon. A very large gradient in moisture was noted this morning with PW at the Platteville research site coming in at a paltry 0.62 inches, while Dodge City, KS measured over 1.5 inches. We expect PW to increase into the 0.9 – 1.4 inch range across eastern Colorado today. Over southern areas, moisture was in the 0.8 – 1.1 inch range with little to no change expected through the day.

A large-scale monsoonal disturbance was noted over the Four Corners. Although the main feature is well southwest of Colorado, a ripple in the flow carries all the way back into southern Colorado. This feature, along with plenty of moisture and instability in the 1,000 – 1,400 J/kg range will support scattered to numerous storms over the southern high terrain this afternoon and evening. A MODERATE flood threat is warranted over the climatologically preferred higher terrain for heavy rainfall primarily over the 30-60 minute duration though some areas could experience up to 3 hours of heavy rainfall.

Further northeast, another remnant disturbance was over western Nebraska, which is causing subsidence in its wake. This feature is actually associated with a poorly defined stationary front that will likely oscillate north/south throughout the day. It is possible that a moist outflow boundary from evening storms could ignite some late evening/overnight convection over the Front Range and Urban Corridor. A LOW flood threat is currently warranted given the uncertainty, but an afternoon update is possible to address this evolving threat.

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, Grand Valley, San Juan Mountains, Southwest Slope, San Luis Valley, Southeast Mountains, Raton Ridge, Southeast Plains & Northwest Slope:

Mostly sunny with some residual clouds left over the southwest, then turning mostly cloudy with scattered to numerous showers and storms developing by early afternoon. Highest coverage will be over the southern higher terrain. A MODERATE flood threat has been posted for parts of the San Juan and Southeast Mountains for max 30-min rain rates up to 1.0 inch and max 1-hour rain rates up to 1.7 inches. Isolated flash flooding, debris slides and mud flows will all be possible over steeper terrain. A LOW flood threat has been for other southern areas for mainly the threat of isolated flash flooding.

Primetime: Noon through 10PM

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

Turning mostly sunny and hot today with widely scattered to scattered showers and storms expected mainly in the late evening and lasting into the overnight hours. A few isolated storms are possible over El Paso County earlier in the afternoon. Max 1-hour rainfall up to 3.0 inches will be possible over far eastern areas, warranting a MODERATE flood threat. Further west, along the Urban Corridor and Front Range, the threat is more conditional, but should storms develop, max 1-hour rainfall up to 2.8 inches is possible. An afternoon update is possible to address this evolving threat.

Primetime: 1PM to 3AM

Issue Date: Tuesday, July 26th, 2022
Issue Time: 10:50AM MDT

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

The zoomed-out water vapor imagery below shows a very nice monsoon pattern with clockwise rotation around the High and counterclockwise rotation around the Low pulling a well-defined moisture plume northward from the Pacific Ocean and Gulf of California. A passing trough to the north is still helping to pull in a slightly drier air mass across Colorado’s northern border with northwesterly flow aloft. Today’s setup looks very similar to yesterday’s setup with a few changes to the details. For one, a surface Low is forecast to develop near the CO/NE/KS border, which will help to return the chance for showers and thunderstorms to Northeast Plains and Front Range. Another change will be ongoing cloud cover and downsloping winds over the Southeast Mountains/Southeast Plains, which should somewhat limit the chance for rainfall this afternoon and evening for the area. Over western Colorado, storms should again be confined to the southern high terrains with a more stable air mass north, but there will likely be a slight downtick in storm coverage with the heavy rainfall threat shifting towards the western border and southern San Juan Mountains.

Even with these changes to the synoptic setup, the threat for heavy rainfall remains with monsoon moisture over the state. PW at Grand Junction is just over an inch with slightly higher values likely across the southern border. Longer duration rainfall is again forecast over southwest Colorado where soils are likely saturated from the last couple days of widespread rain. This is especially true over the southern San Juan Mountains, and with isolated convection possible on top of the longer duration rainfall, a LOW flood threat has been issued. The best opportunity for widely scattered, quick downpours today should be closer to the western border where more breaks in cloud cover are likely, which could help some instability to build for stronger convection. So, a LOW flood threat has also been issued for this area.

Over eastern Colorado, dew points are still in the mid-50°Fs to 60°Fs, and with southerly winds forecast over the far eastern plains, this moisture should remain in place. Extra convergence on the south side of the surface Low with the Palmer Ridge could produce a couple stronger thunderstorms over the plains with additional activity possible over the Northeast Plains as storms move off the Cheyenne Ridge and northern Front Range under northwest steering flows. With the cap keeping storm activity isolated, only 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:

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

Areas over northwest Colorado should remain dry again today, but an isolated weak shower cannot be ruled out over the higher terrains of the Northwest Slope and Grand Valley. Over the Central and northern Southeast Mountains, isolated, weaker storms are forecast with max 30-minute rain rates up to 0.5 inches possible. Closer to the Raton Ridge/Southeast Mountain intersect, max 1-hour rain rates up to 1 inch will be possible.

Longer duration rainfall is forecast for the San Juan Mountains, but the western and southern portions may see some convection along with the high terrains over the Southwest Slope. Max 1-hour rain rates up to 1.25 inches (west) and 1 inch (south) and isolated totals up to 2.25 inches (west) and 1.75 inches (south) will cause a LOW flood threat to be issued. Isolated mud flows and debris slides over steeper terrains as well as road and field ponding will be possible under the stronger storm cores today. The flood threat should end by later this evening, but some light rainfall may linger overnight.

Primetime: 11:30AM to 3AM

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

It should remain mostly dry over the Southeast Plains with some rainfall anticipated across the southern border. Max 1-hour rain rates up to 1 inch will be possible. Isolated storms are forecast for the Front Range with max 1-hour rain rates up to 0.75 inches possible. Over the adjacent plains, there’s a fairly strong cap overhead plus limited upslope flow, but a couple isolated storms may occur. Max 1-hour rain rates up to 2.75 inches would be possible in the high moisture environment, but only if storms can break through the cap. For this reason, a LOW flood threat has been issued. Flash flood threats would include localized road and low-lying area flooding as well as heavy field ponding under the stronger storms that develop. A severe storm could produce damaging outflow winds and hail. The flood threat should end by midnight, but some overnight, lighter rainfall may be possible.

Primetime: 2PM to 5AM

Issue Date: Monday, July 25th, 2022
Issue Time: 10AM MDT

— A MODERATE flood threat has been issued for portions of the San Juan Mountains, Southwest Slope, Palmer Ridge, Southeast Mountains, Front Range & Urban Corridor
— A LOW flood threat has been issued for the Central Mountains, Raton Ridge and Southeast Plains.
— Fire-Burn Forecast Summary:  2 burn areas under MODERATE threat; click HERE for more info

The disturbance from yesterday has now moved east of the state into Kansas and Nebraska as shown by the orange “X” in the visible satellite imagery below. As the disturbance to our north moves southeastward throughout the day, moderate westerly flow aloft is forecast for the northern half of the state. This will help to continue pulling in a drier air mass, which is show by the lack of cloud cover over southern Wyoming and northern Utah. As a response, there should be a decrease in rainfall activity over this portion of the state.

Monsoon moisture remains unaffected across the southern portion of the state with cloud cover and rainfall already occurring over southwest Colorado. Dew points over southeastern Colorado are in the mid 50°Fs to mid-60°Fs, and PW at Grand Junction is around the maximum moving average measured at 1.24 inches. With PW likely over an inch across the southern half of the state and slower steering flows forecast, the stage will be set for another day of heavy rainfall activity. As this moisture pairs with upslope flow, and perhaps some weak mid-level lift, scattered to numerous storms should develop over the high terrains with some spillover anticipated into the adjacent eastern plains. A MODERATE/LOW flood threat has been issued with an increased likelihood for runoff under the stronger storm cores that track over areas with saturated soils. Additional threats include isolated mud flows and debris slides over steeper terrains, rises in local streams/creeks and road/low-lying area flooding.

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:

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

Scattered to numerous storms are forecast to develop over the high terrains by early afternoon with a couple stronger thunderstorms possible east, which may produce some small hail and strong outflow winds. With longer duration rainfall anticipated over the San Juan Mountains, increased runoff is anticipated as there are likely some saturation soils over the area. Max 3-hour rain rates up to 2.75 inches will be possible, so a MODERATE/LOW flood threat has been issued.

Over the eastern mountains, elevated ridges, and to a lesser extent the far eastern plains, more convective storms are forecast today, which may produce some isolated hail and strong outflow winds in addition to heavy rainfall. Max 1-hour rain rates up to 2 inches and isolated storm totals just under 3 inches will be possible, so a MODERATE/LOW flood threat has been issued.

Flood threats today include road and low-lying area flooding, field ponding, rises in local streams and creeks as well as isolated mud flows and debris slides over steeper terrains. Heavy rainfall activity should come to an end a couple hours after sunset, but some lighter rainfall will likely linger into the overnight and morning hours.

Primetime: 11:30AM to 1AM

Northwest Slope, Grand Valley, Northeast Plains, San Luis Valley & Northern Mountains:

A pleasant day is forecast with afternoon high temperatures near or slightly below normal. Rainfall activity should be limited with a more stable air mass overhead, but a couple isolated weak showers may be possible. This will be most likely to occur over the high terrains over western Colorado or over the far Northeast Plains, but only if a storm or two can break through the cap. Totals should remain under 0.2 inches (west) and 1 inch (east), so flooding is NOT expected.

Primetime: 2PM to 8PM