Issue Date: Sunday, August 9th, 2020
Issue Time: 10:05AM MDT

— Flooding is NOT expected today

Today’s weather setup is similar to yesterday, as Colorado is situated between a broad high pressure ridge to the southeast and a broad trough to the north (see image below). The shortwave that initiated storms along the northeastern and eastern border of Colorado yesterday is now moving up into Minnesota. Strong mid-level flow is largely confined within the trough to the north of Colorado. Weak (10-20 mph) mid-level southwesterly/westerly flow is present over Colorado today, as indicated by the 500 mb analysis overlaid on the satellite image below. Some mid-level energy and moisture are creating some clouds over southern Colorado (blue on water vapor image below). This mid-level energy will increase chances for light showers over the southern mountains today. However, dew points are quite dry over Colorado this morning, with 10Fs over northwestern Colorado and 30Fs over southern Colorado. This dry surface air will limit rain accumulation at the surface. The Grand Junction sounding this morning shows a record low PW value of 0.26 inches, which shows just how dry the airmass is over western Colorado. No flooding is expected today.

The eastern border of Colorado is the only place where some moisture is able to hang on, where dew points are in the 50Fs. Farther west over the Urban Corridor, the air is much drier, with dew points in the 30Fs and a below-normal Denver PW value of 0.43 inches. A broad area of low pressure will remain over the plains of Colorado, but small pressure gradients will generally favor weak westerly and northerly winds over the plains. This will not allow higher moisture east of Colorado to be pushed west into Colorado, so much of the low-level moisture that exists along the eastern border of Colorado this morning will be mixed out with diurnal heating today. In fact, temperatures will climb to near-record levels along the Urban Corridor and plains regions today. There still exists a low chance of thunderstorms developing along the eastern border of Colorado today, but the limited moisture will cut down on instability and potential rainfall from these storms. No flooding is expected.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. 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, Urban Corridor, Palmer Ridge, & Southeast Plains:

Partly cloudy and hot, and locations near the eastern border could see a storm or two fire where low-level moisture is able to stay in place. Storms will be fighting plenty of dry air, so max rain rates should stay under 0.5 in/hr. Flooding is not expected with these storms. Near-record high temperatures are expected for the Urban Corridor, with a high of 98F forecast for Denver and a high of 99F forecast for Fort Collins.

Primetime: 1PM to 8PM

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

Mountain clouds and showers are possible this afternoon, with the highest chances of cloud cover and showers over the San Juan Mountains. Northern regions will likely just see some clouds and smoke from the Pine Gulch Fire. Extremely dry air at the surface will limit any rainfall to high elevation locations, where up to 0.05 inches of rain could fall. No flooding is expected. A fire danger still exists for much of western Colorado due to the continued dry weather.

Primetime: 11AM to 8PM

Issue Date: Saturday, August 8th, 2020
Issue Time: 09:45AM MDT

— Flooding is NOT expected today

Today will be continued dry and warm for much of the state as dry air is being pumped in from the southwest due to a significant trough moving into the western US (see satellite image below). PW values in this morning’s soundings at Grand Junction (0.32 in) and Denver (0.42 in) are extremely low, indicating little moisture is available over Colorado. Surface dew points this morning are bone dry (20Fs & 30Fs) for western Colorado and the western half of the plains, but some 40Fs and 50Fs dew points were able to hang on for the eastern Colorado border counties.

Some clouds and showers are visible over northeast Colorado this morning (blue colors on satellite image below), which is associated with a shortwave ejecting off the mountains. This shortwave will allow storms to fire near the northeast borders of Colorado today before moving northeast into Nebraska, where storms could become severe. A low pressure system will develop over the eastern border of Colorado, which will help these storms by allowing some higher surface moisture (50Fs dew points) to remain over the northeast border counties with easterly flow. This low pressure placement will favor drier northerly and westerly winds for the rest of the plains regions, which will limit coverage of storms to only the northeastern borders of Colorado today. Due to the limited moisture and low chances of storms lingering long over Colorado with 20-30 mph mid-level flow, flooding is not expected for the northeast border areas of Colorado today.

Strong diurnal heating will allow some mountain clouds and showers to develop over the southern mountains and Raton Ridge, but limited moisture will prevent any significant rainfall today. No flooding is expected over the mountains today.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. 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, Urban Corridor, Palmer Ridge, & Southeast Plains:

Some clouds and light showers over the Northeast Plains will end this morning and make way for plenty of sunshine. Partly cloudy skies and warm weather is expected for most locations this afternoon. A slight chance exists for thunderstorms to develop along the northeastern borders of Colorado. A storm could drop up to 0.2 inches of rain over these border regions before moving out of the state. No flooding is expected.

Primetime: 2PM to 6PM

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

Afternoon clouds will develop along mountain ridges this afternoon, with the highest coverage expected over the San Juan & Southeast Mountains and Raton Ridge. Showers are not out of the question over the southern mountains and Raton Ridge, but abundant dry air should limit rain accumulations to only high elevation locations. Max rain rates up to 0.1 in/hr. No flooding is expected.

Primetime: 12PM to 6PM

Issue Date: Friday, August 7th, 2020
Issue Time: 9:05AM MDT

— Flooding is NOT expected today

The visible satellite imagery below is showing clear skies start to the day. This indicates that the dry air has moved overhead with the more westerly flow, which is confirmed by PW values measuring 0.3 (Grand Junction) and 0.44 inches (Denver). Perhaps a little moisture will work across the southern border of the Southeast Plains for some high-based, weak showers, but the more likely scenario is just cloud cover this afternoon. With mostly clear skies across the state and a building ridge, high temperatures should increase a few degrees today. The passing trough to our north will continue to tighten the surface gradient over northwest Colorado, so the Red Flag Warning has been re-issued from 11AM to 8PM this evening.

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, Southwest Slope, Northwest Slope, & Grand Valley:

Fire danger returns to northwest Colorado due the passing trough to our north. Southwest surface winds are forecast in the 10 to 20 mph range with gusts up to 30 mph possible. Relative humidity values will likely drop into the single digits, and dry fuels will be problematic for the ongoing fires. A Red Flag Warning has been issued from 11AM to 8PM this evening, so use caution with any activity that could cause a spark. Hazy conditions are forecast again this afternoon due to the fire activity in the region. Highs will reach the upper 80Fs to mid-90Fs over the lower elevations with 70Fs for the mountain valleys.

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

It’s going to be a beautiful summer day with highs climbing into the mid to upper 90Fs across the I-25 corridor. Mountain towns will likely see highs in the mid to upper 70Fs. There will likely be some more haze again from the fires in the regions. Temperatures could reach the 100F over portions of the Northeast and Southeast Plains with highs in the SLV reaching the upper 80Fs. Perhaps a few clouds will form over the mountains and Palmer/Raton Ridges with residual moisture, but they won’t do much more than provide some relief from the heat. Best chance for “rainfall” will be over the Raton Ridge, but only sprinkles are forecast.

Issue Date: Thursday, August 6th, 2020
Issue Time: 10:00AM MDT

— A LOW flood threat has been issued for portions of the Northeast Plains, Palmer Ridge, and Southeast Plains

Colorado is still sitting under the ridge today, but the axis has shifted slightly east. Leftover moisture and energy are lingering at mid-levels, as seen by the blue colors in the water vapor image this morning and showers over the Palmer Ridge (see below). Low-level moisture is still present east over the plains, with dew points in the 50Fs and 60Fs along the eastern border (green line). However, this morning’s sounding at Denver shows decreasing PW values compared to yesterday (0.82 inches), so thinking coverage of rainfall will be a bit less as this is forecast to continue to decrease. Residual low-level moisture will allow for another round of storms to track over the plains, but less severe weather is forecast due to lower wind shear values. Also, a lee, surface low is expected to develop over the western Southeast Plains, which will only support moist southeasterly flow for the eastern portion of the plains. This will help keep the higher dew points in place, but dry downslope winds will likely help to scour out surface moisture along the southern Front Range, Raton Ridge and Southeast Mountains. Therefore, very low chances for rainfall in these areas today. As storms move east during the afternoon, they will encounter better moisture, so some strengthening should occur. Upper-level flow is weaker today over the plains, so storms will produce slightly higher rainfall totals since they will be moving slower. Since there exists a chance for some heavy rainfall cores over the plains, a Low flood threat has been issued for the Northeast Plains, Palmer Ridge, and Southeast Plains.

Very dry air is moving its way into western Colorado with the southwest flow, which is evident on the water vapor image this morning (orange/yellow). This dry air will limit storms over the mountains and western slope today, and an incoming trough will help increase the pressure gradient. This will cause an increase in winds, and with dry fuels, fire danger will also increase. A Red Flag Warning has been issued for the western portion of the state, and you can follow your local NWS office for the latest.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. 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, Palmer Ridge, Urban Corridor, Front Range, & Raton Ridge:

Isolated to scattered thunderstorms will develop over the Front Range and elevated ridges by noon, which will increase in strength and coverage as they move east during the afternoon. Increased surface moisture, instability, and slow storm motions over the eastern half of the plains will allow some storms to drop heavy rainfall with less of a chance for severe weather. Max 2-hr rainfall of 2 inches is possible with these stronger slow-moving cells. A Low flood threat has been issued for the eastern portions of the Northeast/Southeast Plains and the Palmer Ridge. There is also a chance for some severe hail and gusty winds up to 60 mph with the stronger storms.

Storms farther west will stay more isolated in nature and will move east faster due to slightly higher upper-level flow closer to the mountains. 1-hour max rain rates up to 0.25 inches (Front Range) and 0.4 inches (Palmer Ridge) are possible with lower rain rates over the Southeast Mountains. Without upper level support, storms are not expected to linger after sundown.

Primetime: 12PM to 10PM

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

Mostly sunny, warm, and dry today. Increased fire danger is expected over the area today, which has caused a Red Flag Warning to be issued. Surface winds will be in the 15 to 25 mph range from the southwest. Chances for rainfall are nearly zero with the drier air in place, so clear conditions are forecast. Some isolated weak showers are possible along the mountain ridges farther east, but rain rates should stay below 0.1 in/hr due to abundant dry air.

Primetime: 12PM to 6PM