FTB 07-31-2017: Drying Causes Downtick in Heavy Rainfall

Issue Date: Monday, July 31th, 2017
Issue Time: 09:40AM MDT

— LOW flood threat for portions of Central Mountains, Front Range, Urban Corridor, Southeast Mountains, Raton Ridge

An elongated High pressure system is oriented from northern California to northern Texas today that will turn the mid-levels to a more northerly flow. This northerly flow will help pull in the drier air located over WY and NE that will lower Precipitable Water (PW) values across the northern portion of the state. PW over 1 inch is still forecasted for the areas east and south of the dotted green line. The soundings over Colorado this morning are both about 0.85 inches and have drying in the mid-levels. The high dew points over the eastern plains are expected to decrease some throughout the day, and gusty winds are expected with storms that form. There is a Low threat for flooding today, and the threat will be much more isolated than the prior couple days.

As storms begin to initiate over the higher terrain with the diurnal heating pattern just after noon, they are expected to favor the Central, San Juan and Southeast Mountains. PW over the SW corner of the state should be high enough to see 3-hour totals up to 1.5 inches over the San Juan Mountains. Over the eastern mountains, 1-hour rain rates up to 1 inch are possible. Over the immediate adjacent plains along the Palmer Ridge, 1-hour rain rates up to 1.1 inches and 3-hour totals up to 2 inches are possible. Heavy rainfall over the last couple days along the southern Front Range and Southeast Mountains has saturated soils. With 3-hour totals up to 1.25 inches, a Low threat has been posted and burn scars should be monitored closely. Threats include gusty winds, small stream flooding and debris slides. Storm motion will be more southerly today, so there will not be widespread rain over the eastern plains like the previous two days. Showers should come to an end soon after sunset this evening.

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, Central Mountains, Southeast Mountains, Raton Ridge, Southeast Plains:

Sunny today with isolated showers over the mountains this afternoon. 1-hour rain rates up to 1 inch are possible with 1.1 inches over the Palmer Ridge area just adjacent to the mountains. 3-hour rates up to 1.25 inches over saturated soils warrant a Low flood threat. Threats include gusty winds, debris slides, small stream flooding. The threat should diminish by midnight.

Primetime: 1PM to 10PM

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

Sunny today with storms confined to the Southwest Slope and San Juan Mountains. 3-hour rainfall amounts up to 1.5 inches are possible.

Primetime: 1PM to 10PM