FTB 05-26-2015: Showers and Thunderstorms are Still in the Mix

Issue Date: 5/26/2015
Issue Time: 10:02 AM

A LOW FLOOD THREAT HAS BEEN ISSUED FOR PORTIONS OF THE FRONT RANGE, URBAN CORRIDOR, PALMER RIDGE, SOUTHEAST PLAINS, AND SOUTHEAST MOUNTAINS. A LOW FLOOD THREAT CONTINUES FOR PORTIONS OF THE CACHE LA POUDRE/SOUTH PLATTE RIVER, AND PORTIONS OF THE ARKANSAS RIVER.

As the upper-level trough slides to the east of Colorado today, weak mid-/upper-level ridging will move in to take its place. This weak ridging will add a bit of subsidence to the mix, bringing a downtick in showers and thunderstorms for this period. However, this is not to say that showers and thunderstorms won’t occur (they will), there will just be slightly fewer than previous days. Providing the fuel for today’s activity will be residual moisture (slightly greater than yesterday, see IPW chart below), marginal instability, and orographic influences, as well as a weak disturbance that will move west-to-east across Colorado. This weak disturbance is currently located over central Utah and, as it moves eastward, will be the focal point for kicking off today’s activity.

IPW_05262015

The greatest coverage of showers and thunderstorms will be over the higher terrain where orographic influences provide the best forcing on a day marked by a relative lack of upper-level support. Further east, the lower elevations will rely on storms moving off of the higher terrain and marginal instability to develop/maintain showers and thunderstorms. A stronger thunderstorm or two will be possible along the Front Range, Urban Corridor, Palmer Ridge, and western portions of the Northeast/Southeast Plains, with hail, lightning, and brief heavy rain being the main threats. A low flood threat will accompany this due to saturated soils lowering the maximum rain rate needed to produce any flash flooding/mudslide/rock slide issues.

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.

Flood Threat Legend

Zone-Specific Forecasts

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

Warmer and drier overall as compared to yesterday, but isolated-to-scattered showers and thunderstorms will make an appearance again this afternoon and evening. A stronger thunderstorm or two is likely, and will produce hail, gusty winds, lightning, and brief heavy rain. Storm motions aren’t particularly quick; couple this with areas that have saturated soils from previous days of rain, and we have reason to include a low flood threat area. Maximum rain rates from the stronger thunderstorms will be in the 1.0-1.5 inches/hour range.

Timing: 11 AM – 10 PM, with a few showers/thunderstorms lingering until 2-3 AM near the CO/KS border.

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

Scattered showers and thunderstorms expected again today, mainly over the higher terrain. Even so, storm motions will allow for storms to drift over lower elevations with time. Rain rates will mainly be in the 0.2-0.4 inch/hour range, but a few thunderstorms will produce maximum rain rates in the 0.4-0.7 inch/hour range.

Timing: 11 AM – 9 PM, with a few showers lingering after midnight and into the early morning hours on Wednesday.