FTB 09-21-2017: Increasing Winds as the Trough Strengthens

Issue Date: Thursday, September 21, 2017
Issue Time: 10:25 AM MDT

— Flooding is NOT expected today

The strong trough to our west continues to push south and begins to move a little east today. The elongated and positively tilted trough is forecasted to become an upper level, closed Low pressure system by this afternoon. Maximum wind speeds in the jet streak are forecasted to be 120+ knots. Aloft this means more southwesterly flow over the state. As seen in the water vapor imagery below, this flow will continue to advect drier air into Colorado and promote downsloping winds, which will further dry out the atmosphere as it is adiabatically warmed.

With a tight surface gradient and upper level winds mixing down to the surface, winds today are also expected to increase. The winds are expected to increase the most over the higher terrains and southern/eastern plains. A Red Flag Warning has been issued for the eastern plains as well as the southwest corner of Colorado due to low relative humidity and wind gusts this afternoon reaching 20-30 mph. Over the mountains, the fast moving upper level winds will mix down once again, so gusts in the 60-70 mph over the high elevation passes are likely. High winds over the mountains may continue through the night.

With the extremely dry atmosphere, zero to trace amounts of precipitation are expected over the state today. There is some increase in precipitable water late tonight over the southwest corner of the state. This is the same time shortwave activity increases as the trough moves east. The enhanced lift is expected to initiate some late night/morning showers over the San Juan Mountains. Flooding is not expected today or overnight.

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.

Zone-Specific Forecasts:

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

Sunny again today with winds increasing this afternoon over the eastern and southern plains. Once again, high-mountain passes are expected to have gusts around 60 mph as the fast moving, upper level winds mix down. The dry atmosphere will limit coverage in cloud cover and no rain is expected today. A Red Flag Warning has been issued over the plains until this evening due to critical fire weather. Flooding is not expected today.

Primetime: 5PM to 10PM

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

Sunny this morning with winds increasing this afternoon. Higher elevation passes could see wind gusts in the 60-70 mph range. A Red Flag warning has been issued for the southwest corner of the state through this evening. Overnight, precipitable water will increase over the southwest corner of the state at the same time shortwave activity increases from the trough. A few late night/early morning showers are likely over the San Juan Mountains. Storm totals up to 0.5 inches could occur by late morning. Flooding is not expected today or tonight.

Primetime: 12AM to 11AM