FTB 06-27-2016: Low Flood Threat Returns

Issue Date: 6/27/2016
Issue Time: 9:05 AM


Current water vapor analysis shows the building ridge across the southwestern US with general trough-ing over the central US. Northwesterly flow aloft is in place over Colorado, while a shortwave trough pivots across the north-central US. In the wake of this shortwave trough, a cool front will push through eastern Colorado later this morning/early this afternoon, reinforcing easterly upslope flow and low-level moisture along the Front Range and eastward across the plains.

Steep lapse rates above the increase in moisture will support strong instability this afternoon across the Northeast Plains. Combined with sufficient wind shear, discrete supercell thunderstorms will be the preferred storm type, at least during the first few hours of storm activity. These storms will be capable of very large hail (up to 2.5 inches in diameter), periods of heavy rain, and isolated tornadoes. As the evening wears on, interactions between storms will lead to clusters, transitioning the main threat to damaging winds and hail up to 1.5 inches in diameter.


Back across the Front Range/Urban Corridor/Palmer Ridge/Southeast Plains/Raton Ridge, moisture will be a bit less, leading to more moderate instability. Storms will be a bit less vigorous, with the main threats being hail (up to 1.5 inches in diameter), strong winds, and periods of moderate-to-heavy rainfall. Storm coverage will be more isolated-to-widely scattered in these regions, with the best relative coverage over the Palmer Ridge, and Southeast Plains as storms move into the region from the Northeast Plains.

West of the Continental Divide, a lack of moisture will keep the area mostly sunny and mainly dry, with a few isolated storms over the higher terrain. Any storm activity will be high-based, leading to more gusty winds and lightning than rain. For more details regarding timing and rain rates, please see the zone-specific 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

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

Isolated-to-widely scattered thunderstorms are expected to break up the otherwise partly sunny skies today. A couple strong/severe storms are a good bet across the Northeast Plains where the environment will support very large hail, damaging winds, and isolated tornadoes. Periods of heavy rain will also accompany these storms. For the other regions, thunderstorms will be more isolated and a bit less vigorous, but will still hold the potential for strong winds, hail, and periods of moderate-to-heavy rainfall. Maximum rain rates are as follows:

Northeast Plains: 2.0-3.0 inches/hour
Front Range: 1.0-1.5 inches/hour
Urban Corridor, Palmer Ridge, and Southeast Plains: 1.2-1.8 inches/hour
Southeast Mountains and Raton Ridge: 0.6-1.0 inches/hour

Timing: Noon – 9 PM for mountain regions, 1 PM – Midnight for others (with a few storms continuing over the Southeast Plains into the morning hours)

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

Isolated, gusty thunderstorms possible over the higher terrain of the Northern Mountains, Central Mountains, San Juan Mountains, and Southwest Slope. All other locations will remain dry and hot. Skies will be mostly sunny across most locations, with partly sunny skies near the higher terrain seeing the isolated storm activity. Maximum rain rates will be 0.4-0.6 inches/hour.

Timing: Noon – 9 PM, with a couple lingering isolated storms over the San Juan Mountains into the early AM hours