FTB 06-21-2019: Heavy Rain and Severe Weather Forecast over the Palmer Ridge

Issue Date: Friday, June 21st, 2019
Issue Time: 9:45AM MDT

–A LOW flood threat is issued for Palmer Ridge and portions of the Urban Corridor, Northeast Plains and Southeast Plains.

–A LOW flood threat is issued for Saguache Creek, the headwaters of the and along the Rio Grande in Mineral and west Rio Grande Counties and for the San Antonio and Conejos Rivers in south central Colorado.

It’s officially the first day of summer, but expecting some colder, more spring like temperatures to move into the state with the next system. Marked in the visible satellite imagery below is the cold front in blue. Over western Colorado, it is more stationary at this point in time. This feature is expected to begin its push south early this evening and overnight, so it will be a cool, cloudy and potentially wet start to Saturday morning over eastern Colorado. Less cloud cover and just cooler temperatures are forecast for the western slope tomorrow morning. The jet axis has moved into the northwest corner of the state with a southwest to northeast orientation. Thus, expecting quick, southwest flow over the state again today, especially to the west. The last impressive feature on the surface maps this morning (not shown) is the really strong dew point gradient over southeastern Colorado. Dew points are in the mid to upper 50°Fs over the far Southeast Plains, but back to the west at Trinidad, the dew point drops to 24°F. Southwest winds aloft will advect the drier air mass over New Mexico into the Southeast Plains this afternoon, so expect the dew points to begin to drop by noon. This should really keep the severe weather and rainfall threat limited to along and north of the Palmer Ridge this afternoon over eastern Colorado.

Ongoing showers over the northwest corner associated with the jet are expected to continue throughout the day and follow the jets movement. Therefore, expecting more storm activity early this evening further south over the Grand Valley, Southwest Slope and Central Mountains. As the axis of the trough moves eastward overnight, showers will diminish west to east with the axis shift. Colder temperatures behind the front will bring snow to higher elevations (above 9,000 feet). Continuous precipitation with this feature will promote some high 24-hour totals over the Northern Mountains and northern Front Range. However, rainfall should be gradual enough that flooding will be avoided.

Back to the east, a shortwave will arrive around peak heating this afternoon helping form numerous and widespread thunderstorm activity over the eastern Front Range, Urban Corridor and Northeast Plains. The best parameters for a large severe thunderstorm of two will be along the Palmer Ridge. Golf ball sized hail, wind gusts greater than 60 mph and a couple tornadoes will be possible with these severe thunderstorms. Heaviest rainfall is expected to fall along the west to east oriented front due to westerly steering winds in the area around 10 mph. A Low flood threat has been issued for this area with the main threats being street and small stream flooding along with lowland flooding.

The riverine Low flood threat continues for Saguache Creek, the headwaters of the and along the Rio Grande in Mineral and west Rio Grande Counties and for the San Antonio/Conejos Rivers in south central Colorado through Monday. Minor flooding continues to be reported by local emergency management over these areas. Elevated flows continue over the upper Arkansas River, but flooding is not anticipated unless there are some large releases from Pueblo Dam. Keep up to date with the release by following the NWS office in Pueblo. With cooler temperatures forecast going into this weekend, flow are forecast to begin to decrease. This should start to push gages below Action stage early next week.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

Flood Threat Legend

 

Zone-Specific Forecasts:

Front Range, Northern Mountains, Central Mountains, Northwest Slope, Grand Valley, Southwest Slope:

Ongoing rainfall will continue today with the jet overhead and a stationary front in the area. Storms will increase to the south during the early evening hours as the jet begins to sag south. Max 2 to 3-hr rain totals up to 0.7 inches are possible over the Northern Mountains and Front Range with 0.5 inches elsewhere. 1-hour rain rates around 0.25 inches should keep the flooding issues at bay, but there may be increased runoff near the Lake Christine burn area. Isolated 24-hour totals up to 1.5 inches may be possible over the north central mountains with 4 to 10 inches of snow above 10K feet by Sunday morning along and near the Continental Divide.

Primetime: Ongoing to 9AM

Urban Corridor, Northeast Plains, Palmer Ridge:

Heaviest rainfall is expected to occur along the front today, which will rest across the Palmer Ridge. However, with the shortwave moving through, thunderstorm activity will be widespread across these regions. Max 1-hr rain rates up to 1.25 inches will be possible over the western portion of the threat with rates increasing to 1.5 inches over the eastern portion of the threat. Road and small stream flooding along with flooding of low laying areas will be possible. A severe storm or two over the Palmer Ridge will be capable of producing golf ball sized hail, severe wind gusts and a tornado or two. Further north and along the Urban Corridor, max 1-hr rain rates could reach 0.5 inches.

Primetime: 2PM to 10PM

San Juan Mountains, San Luis Valley, Southeast Plains, Southeast Mountains, Raton Ridge:

Drier air will preside over these regions with southwest flow pulling in a dry air mass from Arizona and New Mexico. Dew points are forecast to be 20°F and lower. This will keep these regions mostly cloud free with a slight increase in cloud cover this afternoon over the San Juan Mountains. Temperatures over the eastern plains will be in the 90°Fs with 80°Fs in the mountain valleys. The cold front will move through overnight, so expect overnight temperatures to reach 50°F over the plains and 40°Fs in the valleys.