FTB 08-15-2018: Showers and Thunderstorms for Southern Colorado

Issue Date: Wednesday, August 15th, 2018
Issue Time: 09:10AM MDT

— Flooding is NOT expected today

Partly cloudy skies over the western higher terrains with some weak showers over the southwest corner of the state associated with the disturbance over southeast Utah. Mostly clear everywhere else with some lighter cloud cover over the eastern high terrains as the trough passes to the north. As the upper-level trough continues to move to the ESE throughout the day, drier air will be pulled into northern Colorado. This should nix the chances for precipitation over the northern third of the state this afternoon and evening. The northerly surface winds from this boundary will meet more southerly surface winds over the Palmer Ridge and Southeast Plains, which will help enhance thunderstorm activity over the adjacent plains as storms move off the higher terrains.

As the slightly positively tilted trough passes to the northeast of Colorado, a jet streak will move into the Northeast Plains. This will help increase thunderstorm activity over the Southeast Plains and this afternoon and evening by enhancing lift. The faster steering winds associated with this feature will also keep heavy rainfall to minimum. However, severe hail (up to 1.5 inches) and damaging winds are possible with these stronger thunderstorms as shear and instability look to support a couple severe thunderstorms over the Southeast Plains. As far as initiation today over eastern Colorado, storms will favor the Southern Front Range/Palmer Ridge intersect and Southeast Mountains. A passing shortwave, currently over southern Utah, is expected to increase storm coverage. Again, quicker storm motion and drier low-levels (when compared to yesterday) should keep the flood threat marginal at best. Confidence rain rates will reach 0.5 inches/hour over the recent Southeast Mountain burn scars is low, so there is no flood threat. Over the eastern plains, rain rates should remain under flood threat criteria and dry soils and crops will gladly soak up the moisture and decrease runoff. However, some light field ponding in low-lying areas may be possible under the stronger storm cores.

Over western Colorado, enhanced lift from the shortwave over Utah has already sparked a few weak showers over the southwest corner of the state. Expecting coverage to increase by early afternoon over the Southwest Slope, Grand Valley, Central Mountains and San Juan Mountains. Swift westerly flow aloft and dew points in the 40Fs should limit rainfall totals as the subtropical moisture remains to the south and west. Storms today will be capable of producing strong winds once again with the inverted-V soundings. Flooding is not expected.

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:

Southeast Plains, Raton Ridge, Southeast Mountains, Front Range, Palmer Ridge:

Showers and thunderstorms return to the southern high terrains this afternoon. Decreased moisture and swift steering winds should keep the flood threat to a minimum. A couple severe storms are possible over the Southeast Plains with large hail and damaging winds being the main threats. Max 1-hour rain rates up to 0.5 inches (mountains), 0.75 (adjacent plains) and 1.25 inches (east plains) are possible. Flooding is not expected today.

Primetime: 2PM – 11:30PM

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

Light showers currently over the southwest corner of the state. The shower and thunderstorm activity should increase through the early afternoon with the San Juans receiving the bulk of the activity this afternoon and evening. Threats today include gusty winds and small hail.  Max 1-hour rain rates up to 0.15 inches (north) and 0.5 inches (south) are possible. 24-hour totals up to 0.75 inches are possible over the San Juan Mountains. Flooding is not expected though storms that track over the 416/Burro burn scars should be monitored closely.

Primetime: 11AM – 10PM

Northeast Plains, Northern Mountains, Northwest Slope, Urban Corridor:

Dry air marked in the water vapor imagery above should nix the chances for rainfall this afternoon as northerly surface winds pull the arid air into the state. There is an outside chance for some isolated storms to clip the far northeast corner of the state, but the more likely scenario is those storms will remain in Nebraska. Highs today around 90F over the lower elevations with 60-70Fs in the mountains. Smoke will likely decrease visibility a bit, similar to the last couple of days.