FTB 09-02-2015: Weak Monsoon Disturbance Brings a Low Flood Threat

Issue Date: 09/02/2015
Issue Time: 9:02 AM

A LOW FLOOD THREAT IS ISSUED FOR PORTIONS OF THE SAN JUAN MOUNTAINS, GRAND VALLEY, AND SOUTHWEST SLOPE REGIONS.

Subtropical moisture continues to stream in from the southwest, leaving precipitable water values just above average statewide. The IPW graph below shows the tale of the continuing moisture, although no locations are above 1 inch at this time. That will change this afternoon/evening as a weak disturbance moves into southwestern Colorado, likely pushing the Grand Junction reading near, or just above, 1 inch. This increase in moisture and support provided by the weak disturbance combine to warrant a low flood threat across the San Juan Mountains, Grand Valley, and Southwest Slope regions. Overall, scattered showers and thunderstorms are expected across the higher terrain today, mainly along and west of the Continental Divide, with more isolated-to-scattered coverage along the Front Range and Southeast Mountains.

IPW_09022015

Lower valleys in the high country will likely see scattered showers/thunderstorms move overhead thanks to west-southwesterly steering winds. For areas adjacent to the mountains, i.e., the Urban Corridor, and western portions of the Southeast Plains/Raton Ridge/Palmer Ridge, a couple isolated showers/weak thunderstorms will move overhead, but not much is expected. Some light rain and gusty outflow winds will be about all they can muster. Further east, the atmosphere will stay capped today with high temperatures climbing into the upper 80s to mid-90s.

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

Front Range, Southeast Mountains, Northwest Slope, Northern Mountains, Central Mountains, Grand Valley, San Luis Valley, San Juan Mountains, and Southwest Slope:

Scattered showers/thunderstorms along and west of the Continental Divide, with more isolated coverage to the east. The most coverage will occur along mountain ridges, with a few storms moving overhead of adjacent valleys. Rain rates will break down like this:

Front Range, Southeast Mountains, Northwest Slope, Northern Mountains, Central Mountains, and San Luis Valley: 0.2-0.5 inches/hour
Grand Valley: 0.4-0.6 inches/hour
Southwest Slope and San Juan Mountains: 0.8-1.2 inches/hour

Timing: Noon – 10 PM, with showers/thunderstorms lingering into the early morning hours over the San Juan Mountains, Grand Valley, and Southwest Slope.

Urban Corridor, Northeast Plains, Southeast Plains, Palmer Ridge, and Raton Ridge:

A couple isolated showers/weak thunderstorms will move overhead of areas adjacent to the mountains, but further east no activity is expected. High temperatures will climb above average once again, ranging from the upper-80s to mid-90s. Rain rates from any activity will be less than 0.3 inches/hour.

Timing: 1 PM – 9 PM