FTB 08-20-2017: Increases in Moisture Causes Uptick in Rainfall Coverage

Issue Date: Sunday, August 20, 2017
Issue Time: 10:00AM MDT

— Flooding is NOT expected today

Starting the day again with mostly clear skies across the state. There are a few clouds over the CO/NE/WY intersect associated with the cold front just north of the state. The cold front is more of a wind shift than a temperature reducer, but it may help keep highs a couple degrees cooler over the Northeast Plains than yesterday. A surge of monsoon moisture can be seen just south of CO over NM and AZ. This monsoonal surge will start to slowly increase moisture today, and is expected to continue to do so the next few days. Precipitable Water (PW) is forecasted to rise most over the southeastern plains and southern portion of the state today. This should produce more numerous showers over the higher terrain than we’ve seen the last couple of days.

Storms will begin to initiate with upslope flow just after noon today. They will favor the Southeast and San Juan Mountains due to the slight uptick in moisture and increase in mid-level lift, but storms are also expected to fire over the southern Front Range. As the storms move off the higher terrains, they will initially favor the Raton Ridge and Palmer Ridge, but may become more widespread across the Southeast Plains. Storm motion will be W/NW around 15mph. With the highest instability also over the Southeast Plains, a few storms may produce brief, heavy local rain, small hail, and gusty winds. Guidance is still suggesting the increased moisture will not be enough for 1-hour rain rates to exceed 1.5 inches in an hour (east) or 1 inch an hour (west), so flooding is not expected. Activity is expected to end around midnight over the eastern plains.

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:

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

Most sunny this morning become partly cloudy this afternoon. An increase in thunderstorms are expected over the SE Mountains and Front Range. A few of these storms may become stronger over the adjacent plains producing brief, heavy precipitation, gusty winds and small hail. 1-hour rain rates will be up to 1.2 inches (east) and 0.75 inches (west). Flooding is not expected today.

Primetime: 12PM to 12AM

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

Plentiful sunshine to start the day then it will become partly cloudy over the higher terrain this afternoon. An increase in showers is expected over the Southwest Slope and San Juan Mountains. Thunderstorms may produce 1-hour rain rates up to 0.7 inches. Flooding is not expected today.

Primetime: 12PM to 10PM