FTB 05-24-2016: Severe Thunderstorms Possible Across Portions of Eastern Colorado

Issue Date: 5/24/2016
Issue Time: 9:55 AM

LOW FLOOD THREAT IS FORECAST FOR PORTIONS OF THE FRONT RANGE, URBAN CORRIDOR, AND NORTHEAST PLAINS.

Current analysis shows an upper-level trough laying overtop of the West Coast, while a surface low pressure system develops over SE Colorado/NE New Mexico/SW Kansas/Panhandles. Ejecting from the upper-level trough is a shortwave disturbance, which will move across Colorado later today. The placement of the surface low pressure center is important, as it will help to transport moisture westward into northeastern Colorado, while bringing downlope conditions and drying to much of southeastern Colorado. A Denver Cyclone will also be in play today, providing an additional focus for thunderstorm development.

All of the ingredients mentioned above will combine to create the strong-to-severe thunderstorm risk for portions of eastern Colorado. The regions with the highest relative risk of seeing the isolated-to-scattered thunderstorms will be the Front Range, Urban Corridor and Northeast Plains where the moisture/instability will be best. IPW values remain around average for this time of year (see IPW chart below), which will help mitigate the potential flood threat. However, with strong instability and dewpoints in the 40s and 50s, moderate-to-heavy rainfall will attend the strongest storms.

Further to the south across the Palmer Ridge and Southeast Plains (north of Highway 50), slightly drier air will hinder thunderstorm chances, but one or two isolated storms cannot be ruled out. Otherwise, the area will remain mostly sunny and warm, with generally breezy conditions.

IPW_20160524

For the rest of the state, today will be marked by sunshine and warmth, with high temperatures reaching to normal for this time of year. A few fair weather cumulus clouds will dot the higher terrain this afternoon, attended by a few streaks of virga over the Continental Divide. A sprinkle or two may make its way to the surface over the higher terrain of the Northern and Central Mountains regions, but that will be about all the atmosphere can muster. For more information regarding timing, impacts, and rain rates, 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

Front Range, Urban Corridor, and Northeast Plains:

Isolated-to-scattered strong thunderstorms expected. A few will become severe. The main threats will be large hail and damaging winds, along with a couple tornadoes. Moderate-to-heavy rain will attend the stronger storms, with maximum rain rates as follows:

Front Range: 0.8-1.2 inches/hour
Urban Corridor and Northeast Plains: 1.8-2.2 inches/hour

Storm motions will help mitigate the flood threat somewhat, but a low flood threat is warranted. Street and field ponding will be the main threats, especially combined with hail and locations with poor drainage.

Timing: Noon – 8 PM over the Urban Corridor and Front Range, 2 PM – Midnight over the Northeast Plains

Palmer Ridge, and Southeast Plains:

The threat for isolated thunderstorms is more conditional over these locations, with more needing to go right to get thunderstorms to develop. The better moisture and instability lies to the north of the area, but the shortwave will likely pass just near enough to kick off a thunderstorm or two (along and north of Highway 50). The main threat from any thunderstorm development will be damaging winds and hail (up to 1.25 inches in diameter). Brief moderate rainfall to the tune of 0.4-0.8 inches/hour will be possible. Otherwise, the day will be mostly sunny and breezy.

Timing: 2 PM – 7 PM

Northern Mountains, Central Mountains:

Mostly sunny with high temperatures near seasonal average will be the main weather story today. Afternoon cumulus clouds will develop over the higher terrain, producing mainly virga. A few sprinkles may make it to the surface, but very little rain is expected.

Timing: Noon – 7 PM

Northwest Slope, Grand Valley, Southeast Mountains, Southwest Slope, San Juan Mountains, Raton Ridge, and San Luis Valley:

Mostly sunny and warm, with high temperatures around normal for this time of year. Fair weather cumulus clouds will dot the higher terrain, but overall the day will be marked by abundant sunshine.