Issue Date: Thursday, July 18th, 2019
Issue Time: 9:10AM MDT

–Flooding is NOT expected today

Upper level flow is fully zonal across the continental United States, with the jet stream spanning from Washington to Maine. The upper level high pressure system now sits over Arizona, creating westerly and northwesterly flow over Colorado (Orange Arrow Below). Little to no upper level moisture is expected to enter the state today. PW continues to decrease from yesterday, with 0.3 inches over the Central Mountains and 0.46 inches measured over Denver this morning. At the surface there is currently a high pressure system sitting over the San Juan Mountains (“H” below). Downsloping flow off of the mountains throughout the day (yellow streamlines below) will decrease surface moisture considerably, reducing dewpoints into the 20°Fs over the eastern plains and teens to single digits over the high country and western slope. A Red Flag Warning is in effect for Moffat County and areas of the Front Range, Northern Mountains and Central Mountains between 6000 and 9000 ft. Winds between 10 and 20 mph, with gusts up to 35 mph are forecast over the region.

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.

Zone-Specific Forecasts:

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

No precipitation is forecast for today. High temperatures may reach into the 100°Fs once again over the eastern plains. Wind gusts up to 40 mph are expected over the highest elevations of the Front Range. Afternoon cloud cover may provide some shade this afternoon but it’s going to remain hot and dry over most areas.

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

Another hot and dry day is expected again today, with no chances for afternoon precipitation. High temperatures are expected to be similar to yesterday, with highs in the 100°Fs over the Grand Valley. Relative humidity is expected to drop below 30% throughout the day. Flooding is not forecast for today.

Issue Date: Wednesday, July 17, 2019
Issue Time: 9:40AM MDT

–Flooding is NOT expected today

It’s going to be a scorcher out there today, with high temperatures expected in the triple digits over the eastern plains and Grand Valley. The high pressure ridge that was south of Colorado yesterday has moved back to the west, creating zonal flow over the forecast area (yellow line below). This feature will pull in dry air from the west and produce fast winds over the state. The Red Flag Warning continues today and has expanded in spatial area over the western slope for elevations below 7000 ft. The shortwave that passed over Wyoming yesterday has created a broad region of low pressure over the eastern plains. The low will disrupt normal diurnal upslope flow over the mountains by producing downsloping winds off of the Continental Divide, thus limiting chances for thunderstorms over the high country today. A dryline (orange line below) is forecast to form over the eastern plains this morning and into the afternoon, which will provide the primary forcing mechanism for thunderstorms.

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.

Zone-Specific Forecasts:

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

Afternoon thunderstorms are forecast to form over the Palmer Ridge and Southeast Mountains and move quickly to the east.  Upper level steering flows are expected to be 30 to 35 mph due rapid zonal flow and a jet streak to our north.  Max 1-hr rainfall rates of 0.75 inches and 0.3 inches are forecast over the eastern plains and Southeast Mountains respectively.  The primary threat today will be wind gusts up to 45 mph within the storm vicinity.  Wind gusts up to 50 mph are forecast over the Front Range due to the jet streak to our north. High temps will reach into the low 100°Fs over the eastern plains.

Primetime: 1PM to 8PM

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

It’s going to be a mostly dry day today over the forecast region with a slight chance for afternoon thunderstorms over the Central Mountains.  Max 1-hour rainfall rates of 0.25 inches may occur over the upper elevations.  Wind gusts up to 30 mph are forecast over the Northern Mountains and Northwest Slope.  Expect high temperatures to reach into the low 100°Fs over the Grand Valley, decreasing into the 80°Fs and upper 70°Fs over the higher elevations of the forecast region.

Primetime: 12PM to 5PM

Issue date: Tuesday, July 16, 2019
Issue time: 10:20AM MDT

–Flooding is NOT expected today

Things are going to continue to dry out today as dry air continues to make its way in from the west-southwest. The dry air, shown in yellow in the water vapor imagery below, and gusty winds over northwest Colorado has prompted the issuance of a Red Flag Warning over the Northwest Slope and Grand Valley. The high pressure ridge that is currently centered over the Colorado/New Mexico border is expected to move slightly to the east throughout the day. Clockwise flow around the high will bring in moderate levels of moisture to the southern mountain ranges and is expected to produce thunderstorms this afternoon and tonight. At the surface there is a high pressure system currently sitting over the high country, providing mostly clear skies over the state and allowing for things to heat up rapidly once again today. A shortwave and surface low is expected to form over southeast Wyoming this afternoon, creating a dry line (orange line below) that will sweep over the eastern plains and produce thunderstorms off of the Cheyenne and Palmer Ridge.

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.

Zone-Specific Forecasts:

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

There are still moderate levels of surface moisture present this morning from recent rainfall, with dewpoints measuring in the 40°Fs. However, incoming dry air from the west will limit rainfall accumulations over the northern areas of the forecast region today. Moderate mid-level moisture is expected to come in over the southern areas of the forecast area extending up to the Central Mountains. Max 1-hour rainfall rates of 0.6 inches is forecast over the San Juan and Central Mountains. This does not include recent burn areas. Due to gradual drying out of the surface, thunderstorms are expected to be confined to the higher elevations. Max 1-hour rainfall rates decrease down to 0.1 inches for the other areas within the forecast region. Storms are expected to be primarily between noon and 4PM, with a storms over the Southeast Mountains ending by nightfall.

Primetime: 12PM to 9PM

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

The dryline associated with the shortwave over Wyoming will aid upslope flow this afternoon to produce thunderstorms over the northern regions of the forecast area. Afternoon development over the southern Urban Corridor and Palmer Ridge is expected. Max 1-hour rainfall rates of 0.7 inches is forecast over the Northeast Plains, Palmer Ridge, and northern area of the Southeast Plains. Thunderstorms are also expected over the Raton Ridge, but the bulk of the precipitation is forecast to remain in New Mexico. Maximum rain rates of 0.6 inches are forecast over the Raton Ridge and southern edge of the Southeast Plains. Maximum 1-hour rainfall rates up to 0.5 inches is forecast over the high country. High temperatures over the eastern plains are forecast to be in the upper 90°Fs and low 100°Fs over the eastern plains. Storms over the high country are forecast to end by 6PM, with storms over the eastern plains forecast to end by 11PM.

Primetime: 1PM to 11PM

Issue Date: Monday, July 15th, 2019
Issue Time: 9:10AM MDT

–A LOW flood threat is issued for the Front Range, Urban Corridor, Northeast Plains, Palmer Ridge and portions of the Southeast Mountains and Southeast Plains. This threat includes the Junkins, Hayden Pass and Spring Creek burn areas.

Taking a look at the visible satellite imagery below, the subtropical high has moved a little west and will sit over the Arizona and New Mexico border today. Counter clockwise rotation around the high will produce southwesterly and westerly flow over western Colorado with more northwesterly flow over eastern Colorado in the upper levels. This will pull in a bit of a drier air mass over southwestern Colorado and reduce coverage of heavy rainfall producing storms this afternoon. PW at Denver’s sounding this morning was still elevated at 0.83 inches. Currently, there is a little lift from a shortwave trough causing some early morning cloud cover and isolated areas of rain over the Northwest Slope (marked in orange). As this feature travels to the east throughout the day, it will help spark more numerous showers over the Front Range and Palmer Ridge in tandem with upslope flow this afternoon.

This shortwave will also support storms as the move off the mountains into the adjacent plains. So thunderstorm chances return to the far eastern plains this evening through about midnight. Higher moisture from southeasterly and easterly surface winds over eastern Colorado will allow for some more efficient rainfall rates as well more coverage of thunderstorms just east of the Urban Corridor. Even with steering winds slightly faster than yesterday, totals will likely still cause some minor flooding issues today. A Low flood threat has been issued with the main threats being gusty winds, street and urban flooding and flooding of low lying areas. See the zone-specific forecasts below for more details.

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.

 

Zone-Specific Forecasts:

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

With a more or less a persistent forecast, storms this afternoon and evening will have the potential to produce heavy rainfall once again. Max 1-hour rain rates up to 0.9 inches (mountains/Urban Corridor) and 1.75 inches (eastern plains) are possible. The burn areas over the Southeast Mountains (Junkins, Hayden and Spring Creek) are also included in the Low threat due to rainfall from the last couple of days and the potential for storms today to produce rain rates known to cause flooding issues. Use caution if a storm tracks over those areas as mud flows, debris slides and flash flooding of streams will be possible. Threats over the adjacent plains include street flooding and flooding of low lying/poorly drained areas. Small hail and brief gusty winds (west) and severe hail and stronger gusts (east) are possible with thunderstorms today and tonight. The threat will diminish to the west by 10PM and by 1AM over the eastern plains.

Primetime: 1:30PM to 1AM

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

Expect storms to pick up in coverage this afternoon with enough residual moisture in place for another round of afternoon and evening thunderstorms. Heavy rainfall producing storms will be a little more isolated when compared to yesterday. The highest totals are anticipated over the eastern Central Mountains and San Juan Mountains by morning. Max 1-hour rain rates up to 0.5 inches will be possible with isolated totals up to 0.80 inches by morning. Over the Northern Mountains, 1-hour rain rates will be closer to 0.3 inches. Flooding is not anticipated at this time.

Primetime: 1PM to 8PM