FTB 09-08-2017: Scattered Afternoon/Evening Storms, But Rain Rates Once Again Limited

Issue Date: Friday, September 8, 2017
Issue Time: 9:45AM MDT

— Flooding is NOT expected today

An upper-level disturbance, one that will likely affect Colorado’s weather on and off for the next 5-7 days, has made it to the southwest US coast. As shown in the water vapor image, below, southerly flow ahead of the disturbance is pushing monsoon-origin moisture northward into AZ/NV/UT. However, a weak ridge of high pressure is centered over western Colorado, implying that the brunt of this moisture will not make it into our state today. Instead, plenty of mid-level moisture is noted across the Western Slope this morning. Precipitable Water (PW) values were 0.59 and 0.75 inches at Denver and Grand Junction from the morning balloon launches. PW is not expected to change much, meaning that moisture levels will not be high enough for heavy rainfall today. With abundant sunshine this morning, expect scattered to numerous showers and thunderstorms across most of the High Country this afternoon and evening. Some storms are expected to make it farther east especially over the Cheyenne and Palmer ridges. However, rain rates will stay in the light to moderate intensity and flooding is not expected 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.

Zone-Specific Forecasts:

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

Sunny early, then turning partly cloudy with scattered showers and thunderstorms this afternoon and evening. Highest coverage will be over the High Country and adjacent foothills. Max 1-hour rainfall up to 0.6 inches. Later this evening, isolated to scattered storms could continue in the Northeast Plains, especially along the WY/CO border with max 1-hour rainfall up to 1.1 inches. Flooding is not expected today.

Primetime: 1PM to 11PM

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

Partly cloudy early then scattered showers and thunderstorms this afternoon. Highest coverage will be over the higher elevations and foothills. Max 1-hour rain rates up to 0.5 inches. Gusty winds could accompany the strongest cells. Flooding is not expected today.

Primetime: 1PM to 8PM