Issue Date: 7/19/2016
Issue Time: 9:40 AM
A MODERATE FLOOD THREAT IS ISSUED FOR PORTIONS OF THE SOUTHWEST SLOPE, SAN JUAN MOUNTAINS, AND CENTRAL MOUNTAINS.
A LOW FLOOD THREAT IS FORECAST FOR SURROUNDING AREAS, INCLUDING PORTIONS OF THE NORTHERN MOUNTAINS, GRAND VALLEY, NORTHWEST SLOPE, FRONT RANGE, URBAN CORRIDOR, AND NORTHEAST PLAINS.
Current water vapor analysis shows a strong, upper-level high centered over the south-central US and an upper-level low spinning just off the coast of the Pacific Northwest. These two features have created a pathway for monsoonal moisture to flow into Colorado, pushing IPW values above 1 inch at all four of the normal reporting stations (Grand Junction, Boulder, Pueblo, and Schriever AFB, shown below). This amount of moisture will create an environment in which heavy rain is possible, thus the issuance of the flood threats today.
There are still a few showers/thunderstorms ongoing across western Colorado this morning, owing to a weak disturbance passing through in the mid-level flow. As the day wears on, showers/thunderstorms will increase in coverage over the High Country and Western Slope, generally moving to the northeast with the mean flow. Localized heavy rainfall, gusty winds, and lightning will be the main threats with any of this activity.
Further to the east, scattered showers/storms will move off the mountains and across adjacent lower elevations of eastern Colorado during the afternoon and evening. This activity will first appear just after lunchtime, and continue until 8-9 PM, diminishing fairly quickly and ending by 10 PM. Localized heavy rainfall, gusty winds, and lightning will be the main threats.
Much of the Southeast Plains and Raton Ridge will remain dry, as well as southeastern extents of the Northeast Plains. For those areas, the mid- and upper-levels will not be supportive of developing thunderstorms, and the mean flow will take thunderstorms that develop over the mountains to the north and west of the area.
For more information, including rain rates and timing, please see the zone-specific forecast discussions below.
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.
Zone-Specific Forecasts
Urban Corridor, Northeast Plains, and Palmer Ridge:
Scattered showers/thunderstorms will move off of the mountains and overhead during the afternoon and evening hours. Locations along and near the higher terrain will hold the best chance at seeing this activity. Southeastern portions of the Northeast Plains and far eastern portions of the Palmer Ridge will likely stay dry today, with the mean flow pushing storms across areas to the north and west. Maximum rain rates will be 0.8-1.2 inches/hour.
Timing: 1 PM – 10 PM
Southeast Plains and Raton Ridge:
Western extents of these regions will see a couple isolated showers/thunderstorms this afternoon/evening as they move off of the mountains. To the east, the area will stay dry and mostly sunny, with highs reaching into the 90s and near 100 F. Brief moderate-to-heavy rain, gusty winds, and lightning will attend thunderstorms. Maximum rain rates will be 0.4-0.8 inches/hour.
Timing: 1 PM – 11 PM
Front Range, Southeast Mountains, Northwest Slope, Northern Mountains, and San Luis Valley:
Scattered showers/thunderstorms are expected this afternoon/evening, diminishing between 9 PM and Midnight. Locally heavy rainfall, gusty winds, and lightning will be the main threats. Maximum rain rates are as follows:
Front Range: 1.2-1.8 inches/hour
Southeast Mountains: 0.4-0.6 inches/hour
Northwest Slope: 0.4-0.7 inches/hour
Northern Mountains: 1.0-1.5 inches/hour
San Luis Valley: 0.4-0.8 inches/hour
Timing: 11 AM – Midnight
Central Mountains, Grand Valley, San Juan Mountains, and Southwest Slope:
Scattered showers/thunderstorms are expected this afternoon/evening, with a few showers/storms continuing through the overnight hours and into tomorrow morning. Locally heavy rainfall, gusty winds, and lightning will be the main threats. Multiple rounds of locally heavy rainfall are a concern, and the reason for the issuance of the moderate flood threat. Flash flooding, mud/debris flows, urban ponding, etc. are threats from heavy rainfall. The maximum rain rate is 1.2-1.8 inches/hour.
Timing: 11 AM – 6 AM
