FTB 08-30-2017: Storm Coverage To Increase, But Still No Flood Threat

Issue Date: Wednesday, August 30, 2017
Issue Time: 9:48AM MDT

— Flooding is NOT expected today

As shown in the water vapor image, below, a few changes are noted in this morning’s atmospheric analysis over western North America. First, the strong upper-level ridge that has been around for the last 48-72 hours is slowly weakening and will continue to weaken throughout the day. Meanwhile, a modest shortwave disturbance is entering the California coast. Weak lift and moisture convergence is enhancing mid-level moisture over the northern Great Basin. Some of this moisture will make it into Colorado by later this afternoon. Precipitable water has increased to 0.64 inches (from 0.5 inches 24 hours ago) at Grand Junction and 0.65 inches at Denver. However, most of this moisture is in the mid-levels and despite plenty of morning sunshine, instability will once again be limited today.

Wrapping everything together, we expect an increase in shower and weak thunderstorm coverage today, especially over the higher terrain as the increase in mid-level moisture will help storms stay intact. However, with subsidence still being prevalent and only weak instability, expect a continuation of light to moderate rainfall rates. Thus, flooding is once again not expected today.

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.

Zone-Specific Forecasts:

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

Mostly sunny this morning, then partly cloudy with scattered showers and weak thunderstorms possible. Highest coverage will be over the higher terrain east of the Continental Divide as well as the Cheyenne, Palmer and Raton ridges. Max 1-hour rain rates up to 0.8 inches closer to the foothills and 1.2 inches across the eastern plains. Gusty winds could accompany the strongest storms. Flooding is not expected today.

Primetime: 1PM to 9PM

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

Sunny early, then partly to mostly cloudy with scattered showers and thunderstorms likely this afternoon. Highest coverage will be over the San Juans, Central Mountains and Northern Mountains. Max 1-hour rainfall up to 0.6 inches is possible, with max 24-hour rainfall up to 1 inch especially over higher elevation locations. Gusty winds will accompany the strongest cells. Flooding is not expected today.

Primetime: 12PM to 9PM