FTB 07-23-2019: Flood Threat Issued for Recent Burn Areas

Issue Date: Tuesday, July 23rd, 2019
Issue Time: 9:40AM MDT

— A MODERATE flood threat has been issued for the 416, Hayden Pass and Spring Creek burn areas
— A LOW flood threat has been issued for the Junkins burn area  

A very strong ridge continues to reside over the area with a 596 high (mid-levels) analyzed in the RAP Mesoanalysis this morning. Marked in the water vapor imagery below are several vorticity maximums rotating around the high. These shouldn’t influence the state today, so just expecting storms to initiative with upslope flow from daytime heating. Looking at a nearly identical setup to yesterday, so storms will start firing over the mountains between 1PM and 2PM MDT. Even more dry air will works its way into the state from Wyoming. PW values are currently at 0.83 inches over Denver and 0.89 inches over Grand Junction. These values should continue to drop a little more throughout the day, which will decrease rainfall totals this afternoon. Storms are expected to more scattered over the Front Range and Southeast Mountains with increasing coverage over the San Juan and Central Mountains along with the higher elevations of the Southeast Slope and Grand Valley.

The one area of flooding concern for today are recent burn areas. Over the southwest corner of the state, some low level moisture has drifted northward due to the strengthening ridge. Over the Southeast Mountains, dry air from the north likely won’t mix out enough moisture over the area to keep the threat at bay. Slow, S and SSE drifting storms and multiple storms tracking over the same area may pose an issue for the 416, Hayden Pass, Spring Creek and Junkins burn areas. More southern storm motion should keep the Junkins burn less at risk. However, with saturated soils from yesterday, if a storm does track over the scar, high runoff will likely cause flooding issues. Moderate and Low flood threats have been issued for these reasons. The main threats are flash flooding of local streams and creeks, mud flows and debris slides. Storms should diminish a couple of hours after sundown as instability falls off, so the flood threat will decrease after the 9 to 10PM MDT window.

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.

Flood Threat Legend

 

Zone-Specific Forecasts:

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

More scattered storms expected over the Southeast Mountains and Front Range today with increasing coverage over the San Juan Mountains. Activity may slightly drift into the adjacent plains favoring the Palmer and Raton Ridges, but aren’t expected to spread much further east with steering flows and upper level inversions capping the area. Max 1-hr rain rates up to 0.75 inches are possible over the eastern mountains with max rain rates increasing to 0.9 inches over the San Juan Mountains. Storms over adjacent plains and ridges may produce up to 0.75 inches. These rain rates will cause a Moderate flood threat to be issued for the 416, Hayden Pass and Spring Creek areas and a Low flood threat to be issued for the Junkins burn area. Saturated soils over the Southeast Mountains from yesterday will increase the likelihood for mud flows, debris slides and runoff.

Primetime: 2PM to 11PM

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

Increased storminess is anticipated over the Central Mountains and higher elevations of the Southwest Slope and Grand Valley. The main threats will be moderate rainfall, gusty winds (between 50-60 mph) and small hail. Max 1-hr rain rates up to 0.5 may be possible. Some isolated, lighter rain may be possible over the southern portion of the Northern Mountains, but totals are expected to remain under 0.1 inches. The San Luis Valley edges will likely see another round of rain again today. Totals up to 0.7 inches may be possible by morning with totals up to 0.25 possible over eastern Conejos County. All other areas should stay rain free today due to lack of low level moisture and southern component of the steering flow.

Primetime: 2PM to 8PM