Issue Date: 5/11/2017
Issue Time: 10:05 AM

A MODERATE FLOOD THREAT IS FORECAST TODAY FOR PORTIONS OF THE SOUTHEAST PLAINS DUE TO RECENT RAINFALL.

The upper-level low that has brought about an extended wet period to Colorado will finally exit to the east today. The corresponding surface low (denoted in the visible satellite image below) is already centered over western OK, with wrap-around precipitation remaining only over southeastern Colorado. The extensive cloud shield associated with this low will exit as the morning turns to afternoon, leaving behind mostly sunny skies for much of the state by this evening. The showers currently ongoing across southeastern Colorado are light, and are not expected to produce any additional flooding issues. Ongoing flooding issues across portions of the Southeast Plains will continue through the period, and are outlined on the flood threat map below.

A few showers, and a weak thunderstorm or two, are expected across the High Country today, focused mainly south of I-70, as daytime heating plays on residual moisture. Generally speaking, this activity will be sporadic and garden-variety, with light rain and gusty winds the main threats. For more information on 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

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

Clouds and precipitation will clear from the area with time, eventually resulting in partly cloudy-to-mostly sunny skies and dry conditions by later this afternoon/evening. The skies will clear from north to south, so the Raton Ridge and Southeast Plains will hold onto the cloud cover the longest. The light showers ongoing across the Southeast Plains will exit the state by around lunchtime (or soon after). Near the mountains, a sprinkle or two may be felt this afternoon as showers pop up over the higher terrain.

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

A few sporadic showers/weak thunderstorms are expected to develop this afternoon/evening across the higher terrain as daytime heating plays on residual moisture. No significant precipitation is expected, and no flood threat is warranted. Maximum rain rates will be 0.05-0.15 inches/hour.

Timing: 1 PM – 9 PM

Issue Date: May 10th, 2017
Issue Time: 9:45AM MDT

—MODERATE flood threat for Southeast Plains, Southeast Mountains
—LOW flood threat for Northeast Plains, Palmer Ridge, Raton Ridge, San Juan Mountains and San Luis Valley

The strong upper-level low pressure system that has been slowly trekking across the southwest US will accelerate its northeast movement and move across the far southern part of our state today (see water vapor image below). Strong upper-level divergence to the northeast of the low-pressure will put nearly the entire state in a region favorable for upward motion and precipitation. In addition, the 8AM surface analysis revealed a cool front draped in a northeast-southwest fashion across northeast Colorado. Although the temperature and moisture gradients with the cool front were not particularly impressive as of this morning, this will change as sunshine boosts the warm sector temperatures later this afternoon.

The cool front is also clearly marked by a low-level cloud deck that will strongly limit heating north of its boundary. This will result in little to no instability and low rainfall rates north of the cool front. Along and south of the cool front, the combination of upper-level dynamics, plenty of early sunshine and a moist air axis being advected into southeast Colorado from the east, will result in several rounds of showers and thunderstorms. Very heavy rainfall will be possible with these storms and a low/moderate flood threat has been posted for parts of the region.

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, scroll below the map.

Issue Date: 5/9/2017
Issue Time: 9:40 AM

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

A LOW FLOOD THREAT IS FORECAST TODAY FOR SURROUNDING AREAS, INCLUDING PORTIONS OF THE NORTHERN MOUNTAINS, AND CENTRAL MOUNTAINS.

A LOW FLOOD THREAT IS ALSO FORECAST FOR PORTIONS OF THE NORTHWEST SLOPE, GRAND VALLEY, SOUTHWEST SLOPE, AND SAN JUAN MOUNTAINS.

The upper-level low will continue to linger to the southwest of Colorado, becoming centered over southeastern AZ by tonight. This will allow the anomalous influx of moisture into Colorado to continue, resulting in a second-consecutive day of a moderate flood threat. According to this morning’s soundings from Denver and Grand Junction, precipitable water is in the 90th and 75th percentiles, respectively, for the date. This moisture, combined with large-scale support and sufficient instability/wind shear, will result in scattered showers and thunderstorms, where a few will be strong-to-severe.

Much of the state is expected to get in on the action today, with the strongest storms expected east of the Continental Divide. Severe thunderstorms will be capable of heavy rain, strong winds, hail up to 1.5 inches in diameter, and a couple tornadoes. West of the Continental Divide, the main focus will be on periods of lingering moderate rainfall that may result in minor flooding issues. For more details, please see the region-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, Urban Corridor, Palmer Ridge, Northeast Plains, Southeast Plains, and Raton Ridge:

Scattered showers and thunderstorms are expected today. A few of the thunderstorms will become severe. Threats from severe storms will be heavy rain, strong winds, hail up to 1.5 inches in diameter, and a couple tornadoes. Maximum rain rates are as follows:

Front Range and Southeast Mountains: 0.8-1.2 inches/hour
Urban Corridor, Palmer Ridge, and Raton Ridge: 1.0-1.4 inches/hour
Northeast Plains and Southeast Plains: 1.5-2.0 inches/hour

Timing: Ongoing – Midnight, with lingering showers/thunderstorms into the morning hours tomorrow.

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

Scattered showers and thunderstorms are expected today. With the amount of anomalous moisture in the environment, efficient rainfall production from showers and thunderstorms is expected. A few thunderstorms will bring periods of heavy rain to the tune of 1.0-1.2 inches/hour, thus the low flood threat.

Timing: Ongoing – Midnight, with lingering showers/a few thunderstorms into the morning hours tomorrow.

Issue Date: 5/8/2017
Issue Time: 9:40 AM

A MODERATE FLOOD THREAT IS FORECAST TODAY FOR PORTIONS OF THE URBAN CORRIDOR, FRONT RANGE, PALMER RIDGE, AND NORTHEAST PLAINS.

A LOW FLOOD THREAT IS FORECAST TODAY FOR SURROUNDING AREAS, INCLUDING PORTIONS OF THE NORTHERN MOUNTAINS, CENTRAL MOUNTAINS, SOUTHEAST MOUNTAINS, RATON RIDGE, AND SOUTHEAST PLAINS.

The upper-low, which we have discussed for a few days now, is currently spinning over southern CA/California Baja. Over the central US, the upper-level ridge is still in place, which, in concert with the upper-low, is forcing relatively moist, southerly flow over Colorado. At the surface, a cold front is pushing southward across eastern Colorado, and will stall along/near the Palmer Divide this afternoon. Sufficient instability and wind shear will also be in place across eastern Colorado. Altogether, an environment that will support a few strong/severe thunderstorms, amongst more numerous showers and garden-variety thunderstorms, is expected. The best coverage will occur along/east of the Continental Divide and out over the Plains, where moisture, low-level forcing, and upper-level support will all be most favorable.

Coverage will be a bit more widely scattered across western Colorado, with the higher terrain of the Central Mountains, San Juan Mountains, and Northern Mountains being favored. Storms on the western side of the Continental Divide will have enough instability and wind shear to result in a couple stronger thunderstorms, resulting in pea-sized hail and brief periods of heavy rain. For more information on 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

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

Scattered showers/thunderstorms are expected, and a few will be strong/severe. The main concern for today’s flood threat exists across burn scars and in urban areas where drainage is poor and there are vast impervious surfaces. Maximum rain rates are as follows:

Front Range and Southeast Mountains: 1.0-1.4 inches/hour
Urban Corridor, Palmer Ridge, and Raton Ridge: 1.0-1.75 inches/hour
Northeast Plains and Southeast Plains: 2.0-2.5 inches/hour

Timing: 1 PM – Midnight, with a few showers/thunderstorms lingering over the plains until 4 AM.

Northern Mountains, San Juan Mountains, Central Mountains, and San Luis Valley:

Scattered showers/thunderstorms are expected this afternoon and evening, with the best coverage over the higher terrain. Most storms will be fairly run-of-the-mill, producing gusty winds, lightning, and brief periods of moderate rainfall. Maximum rain rates are as follows:

Northern Mountains and Central Mountains: 0.6-1.1 inches/hour
San Juan Mountains and San Luis Valley: 0.4-0.8 inches/hour

Timing: 1 PM – 10 PM, with a few lingering showers into the early morning hours tomorrow

Northwest Slope, Southwest Slope, and Grand Valley:

Isolated-to-widely scattered showers and a couple thunderstorms are expected today. The best coverage will occur along/near the higher terrain. Most showers/storms will be garden-variety, producing gusty winds, lightning, and brief periods of moderate rainfall. Maximum rain rates are as follows:

Northwest Slope and Grand Valley: 0.4-0.7 inches/hour
Southwest Slope: 0.3-0.6 inches/hour

Timing: 1 PM – 10 PM, with a few lingering showers into the early morning hours tomorrow