FTB 08-24-2017: Enhanced Mid-Level Energy Expected to Bring Widespread Showers

Issue Date: Thursday, August 24, 2017
Issue Time: 10:25AM MDT

LOW flood threat for Northeast Plains, Palmer Ridge, Southeast Plains, Raton Ridge

Lots of high cloud cover this morning over Colorado from convection over New Mexico and over the SW corner of the state. This will help keep high temperatures today a few degrees below normal for August. The cloud cover and ongoing showers are associated with numerous, weak shortwaves in the westerly flow. The mid-level low pressure system that has sat over southern California the last couple of days will break down and eject weak shortwaves over the state throughout the day. The first round of showers associated with these shortwaves started early this morning and a second wave is expected this afternoon. Westerly flow before the shortwave and northwesterly flow after the passage of the shortwave will continue to mix out moisture at the surface over the majority of the state. The weak upper-level ridge will move north of Colorado today and continue to be pushed east through tomorrow morning as the next weather system moves into the Pacific Northwest. Precipitable Water (PW) values at Grand Junction and Denver this morning are 0.76 and 0.64 inches. A surface Low is expected to set up again over the eastern plains, which will pull in moisture rich air on its eastern side. West of this feature, the atmosphere will remain drier. PW values are expected to increase up to 1 inch over the far eastern plains and reach 1.1 inches over the Southeast Plains.

Current showers over the western slope are expected to end mid-morning. The next set of showers will begin just after noon over the higher terrains. This afternoon, more mid-level energy will move through the state with the westerly flow and help enhance convection. The best instability will be along the Palmer Ridge and over the far eastern plains. Expect storms to move off the higher terrains later this afternoon into the adjacent plains with a SE/S storm motion. Storms to the west are expected to produce gusty winds rather than heavy, local precipitation. The outflow boundaries from these storms could help produce addition storms over the adjacent plains in the more moisture rich environment. There also seems to be a convergence boundary that sets up over the Northeast Plains this afternoon, which could produce heavy precipitation. Overall, coverage over the plains, western valleys and mountains will be more numerous than the last couple of days. Storms are expected to end over the mountains a couple hours after sundown and around midnight over the plains. There is a Low flood threat today.

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 this morning with the high clouds decreasing throughout the day. Coverage over the mountains is expected to be numerous, but lower moisture will produce gusty winds rather than heavy rainfall. Over the NE Plains, a convergence boundary sets up this afternoon. With higher moisture and slower storm motion, 1-hr rain rates up to 1.7 inches are possible. West, 1-hr rain rates up to 0.7 inches are possible. Threats include small stream and road flooding as well as field ponding over the plains. Gusty winds and hail up to 0.5 inches are possible with stronger thunderstorms. Storms over the plains are expected to continue until midnight with storms over the mountains ending around 10PM. A Low flood threat has been issued.

Primetime: 1PM to 12AM

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

Cloudy with ongoing showers this morning. Shower coverage will be more numerous this afternoon as a shortwave makes it way over the state. With lower moisture, storms will produce gusty winds rather than heavy, local rainfall. 1-hour rain rates up to 0.5 inches (north) and 0.7 inches (south). Flooding is not expected today.

Primetime: 11AM to 10PM