FTB 07-13-2019: Persistent Thunderstorms over the High Country, Flood Threats Issued over Recent Burn Areas

Issue Date: Saturday, July 13, 2019
Issue Time: 10:15AM MDT

–A MODERATE flood threat is issued for the 416 burn area
–A LOW flood threat is issued for the Spring Creek burn area

The upper level ridge overhead is beginning to slowly break down as a trough pushes its way in off the west coast. Moisture on the backside of the high centered over Colorado has made its way into western Colorado and Utah this morning and will continue to move its way over the forecast area throughout the day. A shortwave over Utah (marked “X” below) will travel over central Colorado later today, providing lift for afternoon thunderstorms over the high country and Northeast Plains. The moisture is farther to the west than originally forecast, however there is still a Moderate to Low chance of flooding over recent burn scars that saw rainfall yesterday.

Max 1-hour rain rates are forecast to be 0.3 inches over the burn areas, but high frequency of storms over the area will allow for max 3-hour rain rates of 1 inch. Antecedent moisture from storms over the area yesterday increases the chances for flooding over the burn areas. Hot temperatures are expected again statewide with sunny skies this morning and warm air being advected in over the eastern plains from New Mexico throughout the day. Surface moisture present this morning over the eastern plains is expected to mix out throughout the day, creating a dry line (orange line below) over the far eastern edge of the area. Dry air will limit severe storm potential over the plains today. Thunderstorms are likely over the high country, Palmer Ridge, and Northeast Plains.

Riverine: As of 9:30 this morning all river gages have retreated below Action stage.  Flows may begin to increase over the weekend as rain returns.  Rivers will likely remain high and fast over much of the state so please exercise caution near river banks.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

Flood Threat Legend

Zone-Specific Forecasts:

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

A shortwave is forecast to move over the Central Mountains early this afternoon from Utah. Moderate to high levels of moisture and upslope flow will combine to produce thunderstorms this afternoon and into tomorrow morning. A Moderate threat is issued for the 416 Burn area, with max 3-hour rainfall rate of 1 inch and max 24-hour rainfall rate of 1.5 inches. Max 1-hour rainfall rates are not expected to be greater than 0.3 inches, however persistent storms over the area throughout the day and into tomorrow morning will create chances for flooding. A Low flood threat is issued for the Spring Creek burn area, with max 3-hour rain rates of 1 inch and max 24-hour rain rates of 1.25 inches. Other areas within the forecast area are likely to receive thunderstorms this afternoon and into tomorrow morning, with max 1-hour rain rates of 0.6 inches. Flooding is not forecast for areas outside of the burn scars.

Primetime: 1PM to 4AM

Urban Corridor, Northeast Plains, Raton Ridge, Palmer Ridge, Southeast Plains, San Luis Valley:

Surface moisture is expected to mix out over the area throughout the day as temperatures increase into the upper 90°Fs. Storms may move off of the Front Range this afternoon, but dry air underneath the storm base is likely to limit rainfall at the surface. Storm motion is forecast to be between 15 and 20 mph, but limited moisture will limit potential for heavy rainfall under the slow moving storms. Upslope flow along the Palmer Ridge will provide chances for afternoon thunderstorms over the area that will move over the Northeast Plains. Max 1-hour rainfall rate of 0.4 inches is forecast over the area.

Primetime: 3PM to 11PM