FTB 07-16-2017: Downtick in Thunderstorm Activity Expected

Issue Date: 7/16/2017
Issue Time: 8:05 AM

A LOW FLOOD THREAT IS FORECAST FOR PORTIONS OF THE NORTHEAST PLAINS, SOUTHEAST PLAINS, RATON RIDGE, PALMER RIDGE, URBAN CORRIDOR, FRONT RANGE, SOUTHEAST MOUNTAINS, CENTRAL MOUNTAINS, AND SAN JUAN MOUNTAINS.

The flood threat will continue today, but the good news is the threat is lower with a downtick in the number of showers/thunderstorms expected. This morning’s visible satellite image paints the picture that shows clearer skies overall to start the day, with the most activity occurring across eastern Colorado nearest the slow-moving mid-level disturbance. As the disturbance slowly continues eastward, drier air will filter in from the north, helping to limit (not completely eliminate, though) showers/thunderstorms across the Northern Mountains, northern Front Range/Urban Corridor, and Northeast Plains. Further to the south, moisture will hang on, leaving the opportunity for heavy rainfall in the forecast.

Across the western slope, isolated showers/thunderstorms will fire up over the higher terrain due to orographic effects and daytime heating, but with much less intensity and coverage than previous days. The threat of heavy rainfall still exists across the San Juan Mountains, due to the availability of better moisture from the south, so the low flood threat is extended to cover this region. For more specific details, 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.

Flood Threat Legend

Zone-Specific Forecasts

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

Isolated-to-scattered showers/thunderstorms expected, with the best coverage across the Southeast Plains and Raton Ridge. Drier air filtering in from the north will help limit coverage to “isolated” across the Northeast Plains, Palmer Ridge, and Urban Corridor. At any rate, moisture and storm motions will still be favorable for periods of heavy rain, so the low flood threat is warranted. Maximum rain rates are as follows:

Urban Corridor and Palmer Ridge: 1.0-1.5 inches/hour
Northeast Plains: 1.0-2.0 inches/hour
Southeast Plains: 1.5-2.5 inches/hour
Raton Ridge: 1.0-1.8 inches/hour

Timing: 2 PM – 11 PM

Front Range, Southeast Mountains, Central Mountains, San Luis Valley, and San Juan Mountains:

Isolated-to-scattered showers and thunderstorms expected, with the best coverage south of I-70. Periods of locally heavy rainfall are possible, and may exceed flash flood thresholds for areas covered by the low flood threat. Burn scars, poorly drained areas, and locations that have received heavy rain over the past several days are the main concerns. Maximum rain rates are as follows:

Front Range: 0.8-1.4 inches/hour
Southeast Mountains: 1.0-1.5 inches/hour
Central Mountains and San Juan Mountains: 0.8-1.2 inches/hour
San Luis Valley: 1.0-1.4 inches/hour

Timing: Noon – 11 PM

Northern Mountains, Northwest Slope, Grand Valley, and Southwest Slope:

A few isolated/widely scattered showers/thunderstorms are expected across these regions, but it will otherwise be mostly sunny and hot, especially for lower elevations. The Southwest Slope will experience the best coverage of showers/storms due to its proximity to better moisture. Maximum rain rates are as follows:

Northern Mountains, Grand Valley, and Southwest Slope: 0.4-0.8 inches/hour
Northwest Slope: 0.3-0.7 inches/hour

Timing: Noon – 11 PM