FTB 07-29-2017: Moisture Remains Intact for More Heavy PM Rainfall

Issue Date: Saturday, July 29th, 2017
Issue Time: 10:35AM MDT

— MODERATE/LOW flood threat for Palmer Ridge, Northeast Plains, Urban Corridor, Front Range, Southeast Plains, Southeast Mountains, Raton Ridge, Central Mountains, San Juan Mountains and Southwest Slope

Water Vapor imagery below shows some isolated embedded showers over the mountains, with cloud cover over nearly the entire state. This cloud cover will begin to break up after strong daytime heating and should not inhibit the formation of thunderstorms today over the eastern plains. Precipitable Water (PW) values at Denver this morning were 1.21 inches and 1.17 inches at Grand Junction. Values are as high as 1.4 inches are over the Southeast Plains. This moisture is expected to stick around with the southerly and southeasterly surface winds. Some of the drier air in northern New Mexico is expected to mix into the Southeast Mountains, which will cause showers to be more isolated (but not less threatening) in nature.

Over the mountains, expect continued showers over the Central Mountains as diurnal heating will lead to an upslope flow pattern. Other storms will begin to fire early this afternoon favoring the southern mountains for the stronger convection. Storm motion will be slow once again, but eventually the storms will push off the mountains later this afternoon and move to the N/NE. Over the Southeast Plains, a boundary will set up this afternoon, which will be located in an area of high instability. Shear will be weak, so most storms should not become severe. However, slow storm motion under the ridge will allow storms to heavy precipitation along the boundary. Once again, sufficient instability will allow storms to continue well after sunset. Lingering showers could persist through about 4AM.

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:

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

Partly cloudy early with showers then scattered to numerous showers and thunderstorms developing by early afternoon. Highest coverage will be where sun is able to break through the clouds. Max 1-hr rainfall up to 2.3 inches (adjacent plains) and 1.1 inches (mountains). 3-hour rainfall up to 4 inches over the plains will support a Moderate flood threat. Threats include mud flows, debris slides, field ponding and small stream and road flooding. The threat is expected to continue over night once again.

Primetime: 1PM to 4AM

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

Mostly cloudy with scattered showers over the Central Mountains. These should increase in intensity this afternoon. Heavier rainfall is expected over the San Juan Mountains with max 1-hr rainfall up to 1.1 inch. 3-6 hour rainfall amounts up to 2.2 inches are possible. A Moderate flood threat has been posted with threats including isolated mud flows and debris slides over saturated soils.

Primetime: 12:30PM to 10PM