Issue Date: Monday, September 16th, 2019
Issue Time: 9:15AM MDT

— A LOW flood threat has been issued for the 416/Burro burn area

Taking a look at the water vapor imagery below, there will be a couple systems over our area through the next 48-hours. The first system, from yesterday, is now starting to exit eastward. Some mid-level energy is still helping to produce moderate rainfall over the southwest corner of the state and fog over the Central and San Juan Mountains. This feature will continue to lift to the northeast throughout the day and help spark some weak, scattered afternoon showers and thunderstorms over the Front Range and adjacent plains. With PW at 0.57 inches this morning (Denver), not much accumulation is anticipated with highest totals anticipated near the Continental Divide. Overnight cloud cover associated this system also helped keep warmer low temperatures in place, so not a huge diurnal temperature swing. Expecting this to occur again tonight (west), though not quite as pronounced, with mostly cloudy skies expected for eastern Colorado tomorrow as the trough moves through the state.

Dry air will fill in behind the first system, so there may be some clearing for a bit over western Colorado. However, another round of storms are expected to move over the western border from New Mexico and Arizona (associated with mid-level energy from the approaching trough) this afternoon. With a little drier air in place (decreasing PW), storms should be high-based, which will limit their heavy rainfall potential and may produce some brief, gusty winds. As mentioned, the next shortwave will start to move through overnight, so showers will be possible over the western high terrains again early tomorrow morning. While some isolated 24-hour totals up to 1.25 inch will be possible over the southeastern San Juan Mountains again (counting rainfall occurring this morning), rainfall rates are forecast be gradual enough that major flooding issues should be avoided. The 416 burn area received around 0.3 inches yesterday (RAWS/CWOP stations), and with possible storms totals today up to 0.75 inches near the scar, a Low threat has been issued for extra caution.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

 

Zone-Specific Forecasts:

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

Max 1-hour rain rates up to 0.5 inches (San Juan Mountains) and 0.3 inches (Southwest Slope) will be possible today. Isolated totals up to 1.25 inches over the southeastern San Juans (southwest facing slopes) will be possible, but rainfall should be gradual enough as to not cause flooding issues. A Low flood threat has been issued for the 416 burn area due to rainfall helping saturate soils yesterday. With 2-3 hour totals up to 0.75 inches possible near the recent scar, mud flows and debris slides chances increase this afternoon. Along the western border, 1-hour rain rates up to 0.25 inches will be possible with northern high terrains receiving up to 0.15 inches in 1-hour. The San Luis Valley is forecast to receive some rainfall as well with totals up to 0.25 inches possible on the fringes. Expect another round of showers over the western high terrains to start tomorrow morning.

Primetime: Ongoing to 12AM

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

Rainfall chances increase over the southern Front Range and Southeast Mountains this afternoon with weak mid-level energy combining with diurnal flow. Storms will be high-based, so best chance for accumulations will be along the Divide over the west facing slopes. Totals up to 0.15 inches will be possible over this area. As storms move to the northeast, moisture is confined to the mid-levels, so this should produce more cloud cover than wetting rains. Although isolated storm totals just over 0.25 inches will be possible over the eastern plains/Raton Ridge.

Primetime: 1PM to 8:30PM

 

Issue Date: 9/15/2019
Issue Time: 6:50 AM

A MODERATE FLOOD THREAT HAS BEEN ISSUED FOR PORTIONS OF THE SAN JUAN MOUNTAINS, SOUTHWEST SLOPE, AND SOUTHEAST MOUNTAINS.
A LOW FLOOD THREAT HAS BEEN ISSUED FOR PORTIONS OF THE REGIONS ABOVE, AS WELL AS PORTIONS OF THE SAN LUIS VALLEY AND CENTRAL MOUNTAINS.

A subtropical disturbance, currently situated over AZ/NM will shift north/northeastward throughout the forecast period, bringing enhanced moisture and broad-scale lift to Colorado later today and tonight. The greatest impacts will be felt over the High Country and south of I-70, where the best moisture and support for thunderstorms will coincide. Precipitable water values will increase to 0.8-1.0 inches today/tonight over portions of the Southwest Slope, San Juan Mountains, and Southeast Mountains, and this amount of available moisture is the driver behind today’s moderate flood threat area. North of I-70, a few isolated storms will rumble, resulting in gusty winds and brief periods of rainfall.

East of the mountains, the increase in mid-level moisture will result mainly in more cloud cover than the previous few days. A couple stray showers/thunderstorms will move off of the higher terrain late this afternoon and during the evening hours, mainly south of I-70, producing gusty winds and brief periods of light-to-moderate rainfall. Otherwise, it will be mostly sunny and warm again today. For more details on rain rates and timing, please see our zone-specific forecasts below.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, jump below the map.

 

Zone-Specific Forecasts

Urban Corridor, Northeast Plains, Southeast Plains, Palmer Ridge, and Raton Ridge:

Mostly sunny, warm, and dry for most, with only a few stray showers/thunderstorms possible for areas along/near the higher terrain and mainly south of I-70. Storm motions will be fairly quick to the north, mitigating the flash flood risk from heavy rainfall. With that said, street/field ponding is possible under the strongest storms. Maximum rain rates will be 0.6-1.0 inches/hour, with most likely rain rates below 0.5 inches/hour.

Timing: 3 PM – 11 PM

Front Range, Northern Mountains, and Northwest Slope:

A few more clouds than the last few days is expected as moisture streams into Colorado from the southwest. These regions will be furthest removed from broad-scale lift induced by the subtropical disturbance, so only a couple isolated showers/thunderstorms are expected late in the afternoon and into the nighttime hours. Rain rates will be below 0.3 inches/hour.

Timing: 4 PM – 11 PM

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

Scattered showers/thunderstorms will begin to move into the Southwest Slope and San Juan Mountains around lunchtime today, developing north/east with time. Peak thunderstorm activity will occur between 2 PM and 9 PM but expect scattered showers with a few embedded thunderstorms to continue into tomorrow morning. Most rain rates will be 0.2-0.4 inches/hour, but thunderstorms could produce rain rates up to 0.8-1.2 inches/hour. Storm motions will mitigate the flash flood risk somewhat, but a moderate flood threat is warranted, and burn scars deserve a close eye.

Timing: Noon – 10 AM tomorrow

Grand Valley and Central Mountains:

Mostly sunny to start, with clouds increasing just after lunchtime as moisture spreads in from the south. Most activity will be garden-variety, producing gusty winds and periods of light rainfall (less than 0.25 inches/hour), but a stronger storm will be possible over southern portions of the Central Mountains (up to 0.4-0.75 inches/hour), hence its inclusion in the low flood threat. A few isolated showers will continue into the early morning hours tomorrow, mainly over the higher terrain of the Central Mountains.

Timing: 2 PM – 6 AM

Issue Date: 9/14/2018
Issue Time: 7:00 AM

NO FLOOD THREAT IS FORECAST TODAY.

Temperatures will trend upward for another day across Colorado as dry air maintains its grip on the region, and the abundant sunshine will push afternoon highs a few degrees above normal for this time of year. A few afternoon clouds will bubble over/near the higher terrain, but they will not result in anything more than a few pockets of shade. The only area to watch today for any potential isolated thunderstorms will be along the CO/NM border over the Raton Ridge and far Southeast Plains, where a weak surface boundary will be in place this afternoon and evening. The odds of storms forming within the state boundary are low – about 15% – but if they do, the main impacts will be brief periods of light-to-moderate rainfall, gusty winds, and occasional cloud-to-ground lightning. Expect any activity to begin after 1-2 PM, and end between 8-9 PM.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

Urban Corridor, Northeast Plains, Southeast Plains, Palmer Ridge, and Raton Ridge:

Sunny skies and warm temperatures are on tap across the region today as dry air continues its hold on Colorado. A weak surface boundary over the far Southeast Plains and Raton Ridge will try to produce one or two garden-variety thunderstorms near the CO/NM border this afternoon/evening, but the chances are low – about 15%. If a storm or two does form, brief periods of light-to-moderate rainfall (less than 0.25 inches/hour), gusty winds, and lightning will be the main impacts.

Timing: 2 PM – 9 PM

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

Abundant sunshine and temperatures a couple degrees warmer than yesterday is the weather story for today. A few afternoon clouds will develop, but they will result in nothing more than a few pockets of shade.

Issue Date: Friday, September 13th, 2019
Issue Time: 8:50AM MDT

— Flooding is NOT expected today

Another mostly dry day for Colorado as westerly flow advects a dry air mass in from the west. This dry air mass can witnessed by the lack of cloud cover over Utah and most of Colorado in the visible satellite imagery below. There are some morning clouds associated with a disturbance over the Northeast and Southeast Plains. These should burn off and move east throughout the morning. High temperatures increase 3-5°F today with some stronger southerly surface winds forecast over the eastern plains. Other than some fair weather cumulus over the Front Range and Urban Corridor, it should be a clear day with PW measured at 0.35 inches and 0.51 inches at Grand Junction and Denver, respectively. A couple weak showers and maybe a clap or two of thunder will be possible over the Southeast Plains (southeast corner) as a disturbance moves in from New Mexico overnight. Flooding is not forecast.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

Zone-Specific Forecasts:

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

Temperatures should be on the rise today, but will cool off overnight. Approaching that time of year where the diurnal cycle really starts to amplify (difference between high and low temperature). Maybe a few clouds are possible over the northern high terrains, but clear conditions are forecast across all other zones. Should be a beautiful day, so try to kick off that weekend a little early!

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

Other than some fair weather cumulus and some light, overnight rainfall over the Southeast Plains, it should be a clear afternoon and evening. Expect high temperatures to increase a couple degrees, and this trend will continue through this weekend. Storm totals up to 0.25 inches will be possible over the Southeast Plains tonight and wouldn’t be surprised if there was a clap of thunder or two. This rainfall is associated with a disturbance moving in from New Mexico. Flooding is not forecast.

Primetime: 5PM to Midnight