FTB 07-29-2015: Fairly Stable Atmosphere Will Limit the Effect of Monsoonal Moisture

Issue Date: 7/29/2015
Issue Time: 10:38 AM


Today is certainly a day where the water vapor imagery is useful in the sense that it shows the locations where monsoonal moisture is present. With the mid-/upper-level high pressure system still anchored across the south-central US, southwesterly flow aloft is dragging monsoonal moisture across southern and eastern portions of Colorado. Observations show that precipitable water values are above average at Shriever AFB (~0.9 inches) and Pueblo (~1.2 inches).


This monsoonal moisture plume (denoted by the green arrow) will continue to work across southern and eastern portions of the state today, with fair amounts of moisture available along the Continental Divide and Central/Southwestern Mountains areas. The moisture, along with weak instability generated by daytime heating, will create isolated-to-scattered showers and weak thunderstorms across the Front Range, Central Mountains, and San Juan Mountains. Instability will be a bit better to the south and east, allowing for better coverage/intensity of storms across the Southeast Mountains, Raton Ridge, and portions of the Southeast Plains (both near the mountains and along the CO/NM border).

Dry air (noted on the water vapor image) will keep the Northern Mountains, Northwest Slope, Grand Valley, and Southwest Slope mostly sunny through the day. The Northeast Plains, Palmer Ridge, and areas of the Southeast Plains not mentioned above will remain dry today, as well; the atmosphere will remain stable and unsupportive of thunderstorm development. Far western portions of the Palmer Ridge and Northeast Plains could see an isolated shower/weak thunderstorm move overhead from the mountains before quickly dissipating in the stable air.

Much like yesterday, the Southeast Plains near the CO/NM border and Raton Ridge will hold the potential for thunderstorms to continue overnight, as more widespread storms are expected to develop over New Mexico and move to the northeast. For this reason, the low flood threat will continue overnight and into tomorrow.

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

Urban Corridor, Northeast Plains, and Palmer Ridge:

Mostly sunny and warm will be the main story today for the Northeast Plains and Palmer Ridge as the atmosphere remains stable overhead. The Urban Corridor, and western portions of the Northeast Plains and Palmer Ridge will likely see a couple isolated showers/thunderstorms move off the mountains overhead this afternoon and evening, before dissipating in the stable air.

Rain rates will be rather modest at 0.4-0.8 inches/hour.

Timing: 2 PM – 8 PM

Grand Valley, Northern Mountains, Northwest Slope, and Southwest Slope:

Mostly sunny for the Grand Valley, Northern Mountains, and Northwest Slope regions, becoming partly sunny across the Southwest Slope where slightly better mid-level moisture resides. No precipitation is expected, except for a weak shower or two across the higher terrain of the Southwest Slope. Rain rates will be 0.2-0.4 inches/hour.

Timing: 11 AM – 9 PM

Front Range, Southeast Plains, Southeast Mountains, and Raton Ridge:

These zones will see the most thunderstorm coverage today, as well as the best rainfall intensities. Moisture values are higher to the south and east, and the rain rates below will reflect this.

Front Range: 0.5-0.8 inches/hour
Southeast Plains and Raton Ridge: 1.2-2.2 inches/hour
Southeast Mountains: 0.8-1.2 inches/hour

Timing: Noon – 10 PM for the Front Range, 11 AM – 5 AM for the Raton Ridge, 11 AM – 11 PM for the Southeast Mountains, and 1 PM – 6 AM for the Southeast Plains

Central Mountains, San Luis Valley, and San Juan Mountains:

Isolated-to-scattered showers/weak thunderstorms expected, with coverage increasing from north to south. Generally light rain will fall early, but as moisture increases during the afternoon and evening hours, rain rates will increase a bit.

Max rain rates will be 0.5-0.8 inches/hour.

Timing: 11 AM – 9 PM