FTB 05-24-2020: A Day of Active Weather Statewide As Welcome Precipitation Arrives

Issue Date: Sunday, May 24th, 2020
Issue Time: 9:45AM MDT

— A LOW flood threat has been issued for parts of the Northeast Plains and Palmer Ridge

A cold front moved south across Colorado late on Saturday, leaving a shield of low and mid-level clouds across central and eastern parts of the state this morning. Light rain and higher-elevation snow showers were seen on radar and in surface observations mainly north of I-70 this morning. Just to our west, a large trough was noted on water vapor imagery (see below). This will support widespread shower and thunderstorm activity for most everyone except the southwest part of Colorado this afternoon and evening. Although the atmosphere’s dynamics are supportive of precipitation today, the combination of limited heating and marginal moisture will fortunately put a cap on rainfall rates for most areas. High temperatures will be anywhere from 5-15F below normal. Precipitable water (PW) values across the state this morning ranged from 0.50-0.70 in. east of the Continental Divide to well below 0.50 inches over western areas.

Over the higher terrain, rain and snow showers will pick up in intensity this afternoon, but will stay well below flood threat levels. Farther east, showers will turn into thunderstorms as more instability is encountered. The “sweet spot” today looks to be just southeast of Denver metro and over the Palmer Ridge. Latest trends in high-resolution model output are slowing the initiation of storm activity by several hours. This will allow instability to get higher than previously expected, with CAPE in the 600-1,000 J/kg range possible. Furthermore, low-level winds are expected to attain a more easterly component in response to the incoming trough, with a deep layer of upslope flow possible for a 2-3 hour period this afternoon. Despite relatively low PW, dynamics will make up for this and support isolated heavy rainfall during the afternoon hours. A Low flood threat has been posted for parts of the region. Several rounds of heavy rainfall are possible before storms organize into a rapidly moving cluster, limiting rainfall rates later into the evening.

In the Southeast Plains, there will be more sunshine and slightly higher moisture today, with CAPE values up to 1,200 J/kg and PW in the 0.70-0.80 range for this afternoon. Scattered storms are expected this afternoon that will have the potential to produce large hail, up to 1.5 inches in diameter, and gusty downdraft winds up to 55 mph. Brief heavy rainfall is possible with these storms, but flooding is not expected. Later into the evening hours, light to moderate rainfall is expected as the trough progresses eastward over the area.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

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

Mostly cloudy this morning with showers increasing in coverage and intensity and gradually turning into thunderstorms this afternoon. Max 1-hour rainfall up to 1.1 inches possible over a localized area southeast of Denver metro. Max 3-hour rainfall up to 1.7 inches possible. A Low flood threat has been posted for parts of the region for a brief period of time this afternoon. Hail up to 1 inch and gusty winds are possible with the strongest storms. Primetime for the flood threat is 2-5 PM.
Rainfall will persist into the evening hours, but will be below flood threat thresholds.

Southeast Plains:

Partly cloudy this morning, then scattered showers and thunderstorms likely this afternoon. The strongest storms could produce hail up to 1.75 inches and gusty winds. Max 1-hour rainfall up to 0.9 inches for western areas and 1.4 inches for eastern areas. However, flooding is not expected due to relatively fast storm motion. Storms will transition into showers during the evening and early overnight hours.

Northern Mountains, Northwest Slope, San Juan Mountains, Central Mountains:

Rain and snow showers picking up in intensity and coverage during the afternoon hours. Max 1-hour rainfall up to 0.5 inches possible. Snow level will range from 8,500 – 10,000 feet. Flooding is not expected today, but travelers should be cautious of slick roads in the higher elevations. Overall, up to 2 inches of welcome precipitation is possible today.

Grand Valley, Southwest Slope, San Luis Valley:

Mostly sunny then partly cloud with isolated to scattered showers this afternoon. Gusty winds are again possible today, leading to a Red Flag Warning for the San Luis Valley. Fortunately, cool temperatures will mitigate the fire threat. Flooding is not expected today.