Issue Date: Wednesday, September 14th, 2022
Issue Time: 10:40AM MDT

— A LOW flood threat has been issued for the Southwest Slope, Grand Valley and Northwest Slope
— Fire-Burn Forecast Summary: 3 burn areas under MODERATE threat, 5 burn areas under LOW threat; click HERE for more info

With subtropical moisture and mid-level lift overhead from the remnants of Kay, it’s a cloudy start to the day (see visible satellite imagery below) with widely scattered, light showers already occurring over portions of western Colorado, the mountains, and far eastern plains. The moisture is well reflected in morning PW values, which were measured at 0.98 inches and 0.58 inches at Grand Junction and Platteville, respectively. To put that in perspective, that’s about 175% greater than the daily mean for Grand Junction! PW is expected to continue to rise over eastern Colorado throughout the day, so over the last 24 to 48-hours, there has been a rapid increase in the available moisture over the state with this system. This means that as daytime heating continues, the ongoing showers are expected to expand in coverage and intensity producing numerous storms over the state by early this afternoon.

As far as the flood threat, over the mountains, fast southwest steering flows and cooler temperatures (minimal instability) should limit the chance for longer-duration heavy precipitation over the area. For eastern Colorado and the Front Range, a drier boundary layer combined with the quick SSW steering flows should limit the flooding potential from storms that develop. Both areas may see some brief moderate downpours, but flooding is NOT expected. There is one area of concern for isolated flooding issues today, which is over the high terrains along the western border. Training storms, moderate instability with breaks in the cloud cover and a higher quantity of surface moisture may cause a handful of storms that develop to produce higher rainfall rates with the decent warm layer depth. A LOW flood threat has been issued for isolated heavy rainfall potential.

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

Isolated max 1-hour rain rates up to 1.25 inches and storm totals up to 1.9 inches may be possible where training storms develop in areas that receive breaks in cloud cover. This could cause isolated debris slides and mud flows over steeper terrain along with some road flooding and ponding in low-lying areas. A LOW flood threat has been issued. More stratiform and brief moderate rainfall is forecast for the mountain zones with storm totals just over an inch possible by tomorrow morning. Similar to yesterday, the flood threat should end by the evening hours, and widely scattered light precipitation will likely linger over the northern high terrain into tomorrow morning.

Primetime: 11:30AM to Ongoing

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

With the increase in moisture, there will be an uptick in the chance for precipitation today. Best chance for accumulation will be over the mountain zones and adjacent ridges. Max 30-minute rain rates up to 0.5 inches (west) and 0.75 inches (east) will be possible. As storms move off the high terrain, limited surface moisture is likely to cause storms to produce some gusty outflow winds. Flooding is NOT expected, and light showers will be likely over the Front Range tomorrow morning.

Primetime: 12PM to 8PM

Issue Date: Tuesday, September 13th, 2022
Issue Time: 9:15AM MDT

— A LOW flood threat has been issued for the San Juan Mountains, Grand Valley and portions of the Northwest Slope, Southwest Slope and Central Mountains
— Fire-Burn Forecast Summary: 3 burn areas under LOW threat; click HERE for more info

As we’ve been tracking in the FTO a major pattern change has begun as an incoming trough helps to push the remnants of Hurricane Kay over western Colorado today. The water vapor imagery below shows the nice subtropical moisture plume in blue, and widespread lift is accompanying the disturbance. As this feature moves northeast throughout the day and into tomorrow, there will be an increase in PW and mid and upper-level dynamics over the area. Today, these features are expected to cause widespread rainfall over western Colorado. The current cloud cover over the area is forecast to expand in coverage with showers already beginning over the southwest corner of the state.

PW at Grand Junction has risen quite a bit over the last 24-hours and was measured at 0.75 inches this morning. However, a dry surface layer was noted in the sounding. As the multi-hour rainfall event begins, the dew point depression should begin to lessen, which means rainfall rates should become more efficient with higher accumulations possible over the lower elevation valleys. While fairly quick southeast to northwest storm motion should somewhat limit the threat from any individual storm, training storms are expected to increase the flood threat over portions of the high terrain. This is especially true for south and southwest facing slopes. Due to the longer duration threat from rainfall today, a LOW flood threat has been issued.

Meanwhile, it should remain dry for most of eastern Colorado with PW at Platteville measured at a measly 0.27 inches. A couple isolated showers may develop along and near the Continental Divide, over the Southeast Mountains and adjacent Raton Ridge area, but accumulations are expected to remain light.

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

Max 30-minute rain rates up to 0.9 inches and 3-hour rain rates up to 1.9 inches will be possible for these zones today. Best chances for the higher accumulations will be over the south and southwest facing slopes of the high terrain where training storms are most likely to develop. Due to the isolated nature of the heavier rainfall totals, only a LOW flood threat has been issued. Flood threats today include mud flows and debris slides over steeper terrain along with ponding in low-lying areas. Rises on local streams and creeks may also be possible closer to the heavy rainfall cores. Most rainfall should come to an end by later this evening, but lighter rainfall is likely to linger over the high terrain into tomorrow morning.

Primetime: 10AM to Ongoing

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

Not much rainfall action today. Best chance for isolated storms will be over the Southeast Mountains with storms also possible over the Front Range along and near the Continental Divide late today into tonight. Isolated afternoon storms could also develop over the Raton Ridge area with moisture from the south sneaking northwards. If storms can develop north of the southern border, totals should remain under 0.25 inches. With only light storm totals forecast, flooding is NOT expected. Otherwise, another dry day is forecast with temperatures remaining above average.

Issue Date: Monday, September 12th, 2022
Issue Time: 8:40AM MDT

— Flooding is NOT expected today

It’s going to be a rinse and repeat pattern today with most of Colorado under the influence of dry northwesterly flow, apart from the southwest corner. Subtropical moisture continues to linger under the ridge over the San Juan Mountains and surrounding area, which will allow for another day of storm development over the high terrain. PW values have likely dropped a little since yesterday, and should continue to do so throughout the day, causing storms to be more isolated in nature. Still, looking at better moisture amounts when compared Grand Junction and Platteville where morning PW values were measured at 0.35 inches and 0.19 inches, respectively. While some training storms may help boost local accumulations, the smaller storm cores are only expected to produce brief downpours, which should limit their flood potential. So, flooding is NOT expected. With High pressure over the state today, surface winds should remain light, which will help to reduce fire weather across the rest of the state as temperatures warm quite substantially.

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 & Southwest Slope:

Isolated storms are forecast for the area favoring the high terrains west for development. Max 30-minute rain rates up to 0.6 inches and isolated storm totals up to 0.85 inches will be possible if a couple of storms track over the same area. Outside of localized runoff under the storm cores, flooding is NOT expected. A couple stronger storms may produce some hail and lightning. Afternoon temperatures will be on the rise with upper 80s °F and low 90s °F returning to the valleys.

Primetime: 1:30PM to 8PM

Southeast Mountains, Front Range, Northern Mountains, Central Mountains, San Luis Valley, Raton Ridge, Urban Corridor, Palmer Ridge, Northwest Slope, Grand Valley, Northeast Plains & Southeast Plains:

Mostly sunny skies are forecast today with temperatures expected to increase another 10°F or so from yesterday. Too dry for any rainfall, so flooding is NOT expected.

 

Issue Date: Sunday, September 11^th, 2022
Issue Time: 8:35 AM MDT

— Flooding is NOT expected today

Saturday’s active dynamics have long departed Colorado, leaving in their wake drying northwesterly flow (see water vapor image, below). PW at Grand Junction was all the way down to 0.16 inches, with Platteville also dropping substantially to 0.25 inches from yesterday morning’s 0.76 inches! Higher moisture does exist along the New Mexico, with a sliver of southwesterly monsoonal flow hanging on. There, PW is perhaps up to 0.7 inches, though it will likely drop a bit this afternoon.

With the drying conditions, we expect a beautiful fall day today with much warmer temperatures (especially for eastern Colorado). Along the New Mexico border, isolated to perhaps widely scattered storms are expected later this afternoon. However, only brief moderate intensity rainfall is expected. Thus, 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:

San Juan Mountains, Southwest Slope, San Luis Valley & Southeast Mountains:

Partly cloudy this morning, then isolated to widely scattered storms possibly later this afternoon. Highest coverage will be over the higher terrain, above 9,000 feet. Max 30-min rain rates up to 0.5 inches possible, along with small hail and gusty winds. However, flooding is NOT expected today.

Primetime: 3PM to 8PM

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

Early morning valley fog should dissipate by noon, leaving plenty of sunshine. Expect warmer temperatures close to seasonal normal today. With no chance of precipitation, flooding is NOT expected today.

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

Mostly sunny and warmer with temperatures topping out a few degrees above seasonal normal. With no precipitation in the forecast, flooding is NOT expected today.