FTB 07-29-2016: Another Round of Thunderstorms Expected

Issue Date: 7/29/2016
Issue Time: 10:08 AM

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

Northwest flow aloft will continue across Colorado today, as shown by the black line/arrows in the water vapor image below. Embedded within the northwest flow is a mid-level disturbance (yellow line), which will serve as a trigger for another afternoon and evening of isolated-to-widely scattered thunderstorms along and east of the Front Range/Southeast Mountains. The support provided by the disturbance is fairly weak, so the number of storms will be less than yesterday.

Low-level moisture is good to the east of the mountains, where widespread dewpoints in the 50s and low 60s can be found. This amount of moisture combined with sufficient daytime heating will keep a low flood threat in the forecast. A few strong/severe storms are likely, especially along the Front Range and Urban Corridor where terrain influences will enhance the local storm environment. The main threats from these storms will be large hail, gusty winds, and locally heavy rainfall. Rain rates will be mentioned in the zone-specific discussions.

WV_20160729

West of the Front Range/Southeast Mountains, drier air will result in very few isolated showers/thunderstorms, if any at all. The water vapor image above shows the drier air overtop Colorado, especially as compared to the moist plumes (brighter white colors) over Arizona, New Mexico, and Utah. Low-level moisture is of utmost importance to storms in this type of environment, and there just isn’t much to be found west of the Front Range/Southeast Mountains. Overall, the locations with the best chance to see an isolated, high-based shower/storm or two are the higher terrain of the Central Mountains, Southwest Slope, and San Juan Mountains. The main impact will be gusty outflow winds, lightning, and virga, with very little rainfall reaching the surface.

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.
20160729_LFT

Flood Threat Legend

Zone-Specific Forecasts

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

Isolated showers/thunderstorms are expected this afternoon and evening, with a couple continuing over the Northeast Plains and Southeast Plains until around midnight or so. Due to cooling provided by yesterday’s thunderstorms, activity will likely be delayed until the mid-afternoon, waiting on the disturbance and ample daytime heating able to break through the mid-level cap.

The first storms of the day will go up over the Front Range/Southeast Mountains, generally moving to the east-southeast across the lower elevations with the mean flow. A couple of the storms will be strong/severe, producing large hail, gusty winds, lightning, and locally heavy rainfall. Maximum rain rates are as follows:

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

Timing: Noon – 11 PM for the mountains, 2 PM – Midnight for the Urban Corridor, 3 PM – 3 AM for the Palmer Ridge, Northeast Plains, and Southeast Plains, and 1 PM – 10 PM for the Raton Ridge

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

Mostly sunny and hot will be the main weather story today, minus a couple isolated, high-based showers/thunderstorms over the higher terrain. Very little rainfall, if any, will reach the surface, so gusty outflow winds and lightning will be the main threats.

Timing: Noon – 10 PM