FTB 05-26-2017: Moderate Flood Threat Today, Accompanied By Severe Weather

Issue Date: Friday, May 26th, 2017
Issue Time: 10:30AM MDT

— MODERATE flood threat for Urban Corridor, Palmer Ridge and Northeast Plains
— LOW flood threat for Southeast Plains

As shown in the water vapor image, below, a strong disturbance was located over the northern Great Basin this morning. As the moves east-southeast today, it will aid the in the formation of a surface low in the lee side of the Colorado Rockies. Impressive pressure drops up to 8-12 millibars are expected by late afternoon. This surface circulation will advect higher moisture values into eastern Colorado and generate instability exceeding 1,000 J/kg. With upper-level forcing from the incoming disturbance and a jet streak located to the north, expect at least one round of showers and thunderstorms to develop east of the Continental Divide. Closer to the mountains, limited instability will keep rainfall rates below flood threat levels. Farther east, heavier rainfall will be possible and a Moderate flood threat has been posted for parts of east-central Colorado. A Low flood threat is posted for areas bordering the Moderate threat area for more isolated heavy rainfall chances. Isolated flash flooding is the main impact today, with field/road flooding likely under the strongest storms.

In addition to heavy rainfall, large hail (up to 1.5 inches in the Low threat region, but up to 2.5 inches towards the KS border) will be possible along with strong winds up to 75mph and a threat of an isolated tornado.

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.

Flood Threat Legend

Zone-Specific Forecasts:

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

Mostly clear this morning then increasing clouds with scattered showers and thunderstorms developing by early afternoon. Early activity will start in the higher elevations, then transition eastward into the plains. Max 1-hour rainfall up to 1.6 inches except up to 2.4 inches in farthest east areas. Max 3-hr rainfall up to 2.9 inches. Hail up to 2.5 inches and gusty winds up to 75 mph will be possible with the strongest storms, along with the threat of an isolated tornado. Isolated flash flooding will be possible under the strongest storms. Field and road flooding will be likely with the heaviest downpours.

Primetime: 1PM to 9PM (across far east), with isolated showers continuing overnight

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

Partly to mostly cloudy skies with scattered showers and perhaps a weak storm this afternoon. Weak thunderstorms are possible in the afternoon. Max 1-hour rainfall up to 0.4 inches. Small hail (less than 0.5 inches) will be possible. Snow level 11,000 feet early, lowering to 9,500 feet later in the day. Flooding is not expected today.

Primetime: 11AM to 8PM, with isolated showers continuing overnight

Raton Ridge, Southeast Mountains

Mostly sunny early, then increasing clouds with an isolated shower or weak thunderstorm possible in the early afternoon. Max 1-hour rain rates up to 0.4 inches. Small hail will be possible with the strongest storms. Gusty winds up to 50mph will accompany the strongest storms. Flooding is not expected today.

Primetime: 2PM to 7PM