Issue Date: 8/16/2016
Issue Time: 9:33 AM

NO FLOOD THREAT IS FORECAST.

Precipitable water increased steadily throughout the afternoon/evening yesterday before leveling off overnight, as shown in the graph below. Another bump from current readings is expected today, pushing IPW values to 0.8-0.9 inches at the 3 reporting locations below (Grand Junction, Boulder, and Schriever AFB). A little better moisture will exist further east over the plains, thanks to better surface moisture values with dewpoints in the 40s/low 50s. Aloft, the important feature will be a weak mid-level disturbance that is expected to rotate across the state this afternoon and evening.

Overall, there is enough moisture for the weak mid-level disturbance to work with, kicking off isolated-to-scattered showers/storms. The best coverage will occur over the High Country and Western Slope, with more isolated coverage over the lower elevations of eastern Colorado. A closer inspection of moisture, however, reveals an inverted-V atmospheric profile, with most of the moisture existing above 2.5 km aloft. As the day wears on, some of that moisture will mix closer to the surface, helping boost rain rates a bit during the late afternoon and evening hours, but not enough to warrant any flood threat issuance. For more information on timing and rain rates, please see the zone-specific discussions below.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below (hover over threat areas for more details). For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

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

Isolated showers/thunderstorms expected to move off of the higher terrain and over the lower elevations this afternoon and evening. The main threats from storms will be gusty winds up to 30-40 mph and lightning, with light-to-moderate rainfall. A brief period of locally moderate-to-heavy rainfall cannot be ruled out, especially with interacting outflow boundaries. If heavy rain occurs, minor street/field ponding will be the main impact. Maximum rain rates are as follows:

Northeast Plains, Southeast Plains, and Palmer Ridge: 0.8-1.4 inches/hour
Urban Corridor and Raton Ridge: 0.6-1.0 inches/hour

Timing: 1 PM – Midnight

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

Scattered showers/thunderstorms are expected today/tonight. The best coverage will occur across the higher terrain, with widely scattered showers/storms drifting over the lower elevations. Drier air in the low levels will temper rain rates today, leaving the main impacts to be gusty winds (up to 30-40 mph) and lightning. Most activity will produce light-to-moderate rainfall, but a stronger storm or two producing brief locally heavy rainfall is possible. Burn scars, especially the Hayden Pass fire burn scar, should be monitored closely as a precaution, but no flood threat is warranted. Maximum rain rates are as follows:

Southwest Slope, San Juan Mountains, Front Range, and Southeast Mountains : 0.6-0.8 inches/hour
Central Mountains, San Luis Valley, and Grand Valley: 0.5-0.8 inches/hour
Northern Mountains, Northwest Slope: 0.4-0.6 inches/hour

Timing: 11 AM – 10 PM, with a couple isolated showers continuing into the morning hours over the higher terrain of southwestern Colorado

Issue Date: 8/15/2016
Issue Time: 9:22 AM

NO FLOOD THREAT IS FORECAST.

Precipitable water values are expected to rebound a bit today as slightly more mid-level moisture rotates into the state from the north/northwest. Even so, low-level moisture will be lacking for the western two-thirds of Colorado, so any gain over yesterday’s moisture values will be minimal. With that said, this afternoon/evening will see a few more showers/thunderstorms develop as compared to yesterday, thanks to a weak, mid-level disturbance. The best coverage of isolated-to-widely scattered storms will be over the higher terrain, mainly over the Central Mountains, Northern Mountains, Front Range, Southeast Mountains, and San Juan Mountains, where orographic effects play a role. Over the adjacent lower elevations, a few isolated showers/thunderstorms are expected over/near the preferred terrain of the Cheyenne Ridge and Palmer Ridge. Inverted-V atmospheric profiles suggest that the main threats from any storms will be gusty winds and lightning, with only brief periods of light-to-moderate rainfall.

Further to the east over the far Northeast/Southeast Plains and far Palmer Ridge, slightly better low-level moisture can be found. Dewpoints in the 40s will help any isolated storms tap into slightly more efficient rainfall processes, resulting in moderate rainfall. Brief periods of locally heavy rain cannot be ruled out, but no flash flooding issues are expected. For more information regarding rain rates and timing, please see the zone-specific forecast discussions below.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below (hover over threat areas for more details). For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

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

Mostly sunny skies and temperatures similar to yesterday is the main weather story today. Isolated showers/thunderstorms are expected this afternoon and evening, producing gusty winds, lightning, and mainly light rainfall. A few stronger storms tapping into better surface moisture over the far eastern plains/Palmer Ridge will produce brief periods of locally heavy rain. Maximum rain rates are as follows:

Urban Corridor: 0.3-0.6 inches/hour
Palmer Ridge: 0.4-0.8 inches/hour
Northeast Plains and Southeast Plains: 0.8-1.2 inches
Raton Ridge: 0.2-0.4 inches/hour

Timing: 1 PM – 9 PM, with a few isolated showers/storms lingering until just after midnight

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

A slight uptick in high-based showers/thunderstorms is expected this afternoon/evening as compared to yesterday. Most will remain anchored to the higher terrain, but a couple with move with the steering flow over adjacent lower terrain. With surface moisture lacking, any activity will struggle to maintain itself and will be short-lived. Maximum rain rates are as follows:

Northern Mountains, Northwest Slope, Central Mountains, Southwest Slope, and Grand Valley: 0.15-0.3 inches/hour
San Juan Mountains: 0.4-0.6 inches/hour
San Luis Valley: 0.2-0.4 inches/hour
Front Range and Southeast Mountains: 0.3-0.5 inches/hour

Timing: 11 AM – 10 PM, with one or two lingering showers into the early morning hours

Issue Date: 8/14/2016
Issue Time: 9:00 AM

NO FLOOD THREAT IS FORECAST.

The disturbance, and its parent low pressure circulation, that provided forcing for yesterday’s uptick in showers/thunderstorms have continued their progression, now east of Colorado. An upper-level ridge of high pressure has filled in behind it, and will become centered over the shared borders of CA/NV/AZ/UT by this afternoon. This will bring warming aloft to Colorado, capping off much of the environment and boosting surface high temperatures this afternoon.

A few showers/thunderstorms are still expected, working off of residual moisture and benefitting from favorable terrain. Isolated-to-widely scattered showers/thunderstorms will develop initially over the higher terrain of the Central Mountains, San Juan Mountains, Southwest Slope, Front Range, and Southeast Mountains, and move to the south-southeast with time. This will bring a couple of showers/thunderstorms over the lower elevations, including the Urban Corridor, during the afternoon/evening hours. Additionally, the preferred terrain of the Cheyenne Ridge, Palme Ridge, and Raton Ridge will likely kick off a couple isolated showers/thunderstorms. Rain rates will remain below flood threat thresholds, as moisture is simply too low. Expect any thunderstorm activity to produce more wind/lightning than rain. For more information regarding timing and rain rates, please see the zone-specific forecast discussions below.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below (hover over threat areas for more details). For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

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

Mostly sunny and warmer will be the main weather story today. A few isolated-to-widely scattered showers/storms are expected over/near the higher terrain, and along the preferred terrain of the Cheyenne Ridge, Palmer Ridge, and Raton Ridge. Maximum rain rates will be 0.3-0.6 inches/hour over the higher terrain, and 0.4-0.8 inches/hour elsewhere.

Timing: 11 AM – 11 PM

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

A few isolated-to-widely scattered showers/weak storms are expected over the higher terrain, but the main weather story will be the mainly dry conditions. Moisture values are low, so storms will produce more wind/lightning than rain. Maximum rain rates will be 0.3-0.6 inches/hour.

Timing: 11 AM – 10 PM

Northern Mountains, Northwest Slope, and Grand Valley:

Mostly sunny and dry will be the name of the weather game today. A few high-based cumulus clouds will be noted over the higher terrain, but nothing more than virga will result. A Fire Warning continues for Mesa County, so be sure to check in with the National Weather Service in Grand Junction for more information.

Issue Date: 8/13/2016
Issue Time: 9:33 AM

A LOW FLOOD THREAT IS FORECAST FOR PORTIONS OF THE NORTHEAST PLAINS, URBAN CORRIDOR, PALMER RIDGE, SOUTHEAST PLAINS, RATON RIDGE, FRONT RANGE, AND SOUTHEAST MOUNTAINS.

A weak disturbance in the northwest flow aloft will be responsible for the increase in storm coverage today, mainly for areas along and east of the Continental Divide. This scenario is picked up well by this morning’s ensemble of high-resolution models, which I have decided to show below. West of the Divide, moisture is scarce, and very little activity is expected. The exception to this will be over the higher terrain of the San Juan Mountains and Southwest Slope, where a couple isolated showers/weak thunderstorms will have access to slightly better low-level moisture.

Helping the weak disturbance in the development of showers/storms over eastern Colorado will be the preferred terrain of the Front Rage/Southeast Mountains, Cheyenne Ridge, Palmer Ridge, Raton Ridge, as well as a surface convergence boundary laid across the eastern plains. Most storms will be garden variety, producing periods of moderate rainfall, gusty winds, and lightning. A few stronger storms are expected, with periods of brief heavy rainfall and small hail mixed in with the gusty winds/lightning. Outflow boundaries will locally enhance available moisture, and any storms interacting with another storm’s outflow will be the likeliest to produce heavy rainfall. For more details on timing and rain rates, please see the zone-specific discussions below.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below (hover over threat areas for more details). For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

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

Isolated-to-scattered showers/storms are expected, most producing periods of moderate rainfall, gusty winds, and lightning. A few stronger storms are possible, producing periods of locally heavy rainfall and small hail. Maximum rain rates are as follows:

Front Range and Southeast Mountains: 0.6-1.0 inches/hour
Urban Corridor: 0.8-1.1 inches/hour
Palmer Ridge: 0.8-1.2 inches/hour
Northeast Plains: 1.2-2.0 inches/hour
Southeast Plains and Raton Ridge: 1.5-2.5 inches/hour

Timing: Noon – Midnight, with a couple showers/storms lingering into the early morning hours over the Southeast Plains/Raton Ridge

San Juan Mountains and Southwest Slope:

Isolated, high-based showers/weak storms expected over the higher terrain. Most rainfall will be light, with maximum rain rates of 0.4-0.6 inches/hour. Otherwise, mostly sunny skies will prevail.

Timing: 11 AM – 8 PM

Northern Mountains, Central Mountains, Northwest Slope, Grand Valley, and San Luis Valley:

Mainly dry under mostly sunny skies, with only a couple isolated showers/weak storms expected over the higher terrain near/along the Continental Divide. Most will only produce virga/gusty winds with light showers. Maximum rain rates will be 0.2-0.4 inches/hour.

A Fire Warning is in effect for Mesa County as a wildfire was reported in the vicinity of Horse Mountain. Please stay tuned to National Weather Service – Grand Junction for more information.

Timing: 11 AM – 8 PM