Issue Date: 5/27/2019
Issue Time: 9:20 AM

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

An upper-level low that has slowly progressed across the Western US over the last several days will finally begin its march into the state in earnest today, becoming centered over Colorado by 6 AM tomorrow morning. Ahead of this upper-level low, strong southwest flow aloft will contribute ample wind shear to the environment today; coupled with good instability, the development of scattered strong-to-severe storms is expected over northeast Colorado this afternoon and evening. Along with large hail, strong winds, and an isolated tornado or two, these storms will be capable of producing periods of heavy rainfall as they move towards the northeast; thus, the issuance of the low flood threat for portions of the Urban Corridor, Palmer Ridge, Front Range, and Northeast Plains.

To the south, an arced dry line will set up roughly along a line from Monument – Eads – Campo; south and west of this dryline, and east of the mountains, moisture will be scoured out, and mostly sunny skies and breezy southwest winds will be the main weather story today. Over the High Country, the low will provide broad support for scattered showers/thunderstorms of the garden variety this afternoon/evening, with snow falling in the highest elevations. As the evening wears on, snow levels will drop to around 9000 feet. Jackpot totals of 6-12 inches, and perhaps up to 18 inches, will be possible for the highest elevations of the Front Range, Northern Mountains, and Central Mountain through tomorrow evening. For more details on timing 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. For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

Urban Corridor, Northeast Plains, Southeast Plains, Palmer Ridge, and Raton Ridge:

Scattered thunderstorms are expected north and east of the arced dryline from Monument – Eads – Campo this afternoon and evening, with a few being strong/severe, mainly north of I-70. To the south and west of this dryline, dry conditions and gusty southwest winds will be the weather story. Maximum rain rates will be 0.75-1.5 inches/hour over the Urban Corridor and Palmer Ridge, 1.5-2.25 inches/hour over the Northeast Plains, and 0.5-0.75 inches/hour over the Southeast Plains. The Raton Ridge is expected to remain dry.

Timing: Noon – 10 PM, with lingering showers/storms over the Urban Corridor and Northeast Plains into the early morning hours

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

Scattered showers and thunderstorms are expected today, with most of the activity being garden-variety, producing periods of light-to-moderate precipitation (snow above 9000-10000 feet) and gusty winds. The Front Range, thanks to moisture transport from the east, will have the potential for a brief period of heavy rainfall, thus the inclusion in the low flood threat. Due to the approach of the upper level low, scattered activity will continue into the overnight hours across the High Country, mainly over the higher terrain. Maximum rain rates are as follows:

Front Range: 1.0-1.25 inches/hour
Southeast Mountains: 0.05-0.15 inches/hour
Central Mountains, San Juan Mountains, Southwest Slope, Grand Valley, Northwest Slope, and Northern Mountains: 0.25-0.5 inches/hour
San Luis Valley: < 0.1 inches/hour

Timing: 11 AM – 11 AM

Issue Date: 5/26/2019
Issue Time: 9:20 AM

A LOW FLOOD THREAT IS FORECAST TODAY.

An active weather day is expected for eastern Colorado, and this can be evidenced by the return of low-level moisture. Highlighted on the surface map below is the area of 50°+F dewpoints, with a few 60°+F dewpoints sneaking into the far Southeast Plains. This moisture will be the fuel behind today’s threat of strong/severe storms for areas east of the mountains and will be sufficient enough for the introduction of a flood threat. Meanwhile, over the High Country, residual moisture that remains in place will be enough for high-based showers/thunderstorms this afternoon/evening. There are three trigger mechanisms today that will set off the thunderstorms: 1) daytime heating, 2) a disturbance aloft, and 3) a sharpening dryline over southeast Colorado. The combination of the three will provide enough forcing for scattered showers and thunderstorms across the state, with all regions getting involved, albeit some more than others.

Over the High Country, moisture is too shallow for any concerns over heavy rainfall; instead, the scattered activity today will be garden-variety and high-based, producing gusty winds, light rainfall, and occasional lightning. East of the mountains, however, moisture is sufficient for the production of strong/severe thunderstorms, as well as periods of heavy rainfall. Storm motions will be quick enough to the east/northeast to limit the flood threat, but not quick enough to avoid a low flood threat.

For more details on timing 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. For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

Urban Corridor, Northeast Plains, Southeast Plains, Palmer Ridge, and Raton Ridge:

Scattered strong/severe thunderstorms are expected today/tonight, kicking off around 1 PM, and continuing into the nighttime hours. Instability, fueled by daytime heating and good moisture, will promote rapid thunderstorm development and coupled with adequate wind shear, storms will hold the potential for all severe hazards (i.e., large hail (up to 2.5 inches in diameter), strong winds (up to 70 mph), and a couple tornadoes). The bulk of thunderstorm activity is expected over the Northeast Plains and Southeast Plains, with more widely scattered storms over the Urban Corridor and Palmer Ridge. The Raton Ridge region will be behind the dry line, so isolated development there is expected to be high-based, producing mainly gusty winds and periods of light rainfall. Maximum rain rates are as follows:

Northeast Plains and Southeast Plains: 1.5-2.5 inches/hour
Urban Corridor and Palmer Ridge: 1.0-1.5 inches/hour
Raton Ridge: 0.2-0.4 inches/hour

Timing: 1 PM – 9 PM for the Raton Ridge, 1 PM – 10 PM for the Palmer Ridge, 1 PM – 11 PM for the Southeast Plains, 1 PM – Midnight for the Urban Corridor and Northeast Plains, where a Denver convergence zone will try to keep some storms going into the night.

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

Scattered showers/storms are expected this afternoon and evening across the area, with the bulk of storm activity over the higher terrain of the Southwest Slope, San Juan Mountains, Central Mountains, Northern Mountains, Southeast Mountains, and Front Range. Most of the activity will be high-based, moving quickly to the northeast, producing gusty winds and periods of light rainfall. The best chance at wetting rainfall will be over the Front Range, where good surface moisture has backed into the mountains from the eastern plains. The maximum rain rates are as follows:

Front Range: 0.2-0.4 inches/hour
Northern Mountains and Central Mountains: 0.15-0.30 inches/hour
Southeast Mountains, San Juan Mountains, Southwest Slope, Grand Valley, and Northwest Slope: 0.1-0.2 inches/hour
San Luis Valley:

Timing: Noon – 10 PM

Issue Date: 5/25/2019
Issue Time: 8:50 AM

NO FLOOD THREAT IS FORECAST TODAY.

A pleasant start to the holiday weekend is expected today, as much of the state will experience abundant sunshine and temperatures a few degrees warmer than yesterday. Already this morning, you’ve probably noticed that ball of fire in the sky that has been too scarce recently. Just look at the visible satellite image below – very few clouds can be found anywhere in Colorado. Dry, southwest flow aloft, coupled with dry air in the lower levels, will make sure that remains the case for much of the state throughout the day. However, there will be two areas of exceptions to the dry rule today east of the Continental Divide.

The first area of exception will be over the far southeast plains, where dewpoints in the 50s will spread in during the afternoon hours in response to a surface low pressure circulation developing over the Raton Ridge region. This will strengthen a dry line over far southeast Colorado, which will become the forcing mechanism for a couple isolated strong-to-severe thunderstorms near the CO/KS/OK border. These storms will be capable of producing large hail (up to 2 inches in diameter), strong winds up to 70 mph, and an isolated tornado or two.

The second area of exception will be over the Front Range, Urban Corridor, Palmer Ridge, and Northeast Plains regions. During the afternoon and evening, isolated, terrain-induced, high-based showers and thunderstorms will be possible as daytime heat works on available residual moisture. Gusty winds and virga will be about all this activity can muster, with perhaps a brief period of light rain from the most persistent shower/storm. As this activity moves over the Northeast Plains this evening, access to better surface moisture will allow for periods of moderate rainfall underneath an isolated storm.

For more details on timing 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. For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

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

Sunny and dry for most, with isolated afternoon/evening storms within the two areas of exception listed above. Maximum rainfall rates will be as follows: 0.75-1.2 inches/hour over the far Southeast Plains associated with the strong-to-severe storms, 0.05-0.15 inches/hour over the Front Range, 0.2-0.4 inches/hour over the Urban Corridor and Palmer Ridge, and 0.5-1.0 inches/hour over the Northeast Plains.

Timing: 1 PM – 8 PM over the Southeast Plains, 1 PM – 7 PM for the Front Range, 2 PM – 8 PM for the Urban Corridor and Palmer Ridge, 3 PM – Midnight for the Northeast Plains

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

Plenty of sunshine and dry conditions will be the name of the weather game today, with high temperatures around normal for this time of year. Cumulus clouds will bubble over the higher terrain during the afternoon and evening hours as sunshine plays on residual moisture, but little-to-no precipitation is expected. The best chance at even a sprinkle will be over the higher terrain of the Central Mountains, Southeast Mountains, and Northern Mountains regions.

Timing: 1 PM – 7 PM

Issue Date: Friday, May 24th, 2019
Issue Time: 8:40AM MDT

–Flooding is NOT expected today

Another cold night across the state with lows reaching the low 30°Fs across the Urban Corridor and dipping below 30°F over the Southwest Slope. Today, the system that brought widespread rainfall, cloud cover and snow to the higher elevations is well to the north of the state. Behind the system, a much drier air mass has worked its way into the state with the SSW flow aloft. Outside of a few scattered showers over the Northwest Slope and Northern Mountains this afternoon, the state is forecast to stay dry. Temperatures will also begin to rebound with highs reaching the low 80°Fs over the eastern plains, and mid-60°Fs over the western valleys. Over the mountains, temperatures are expected to reach the mid-40°Fs to 50°F in the valleys. Temperatures are still a bit below normal for this time of year, but at this point, we’ll take it.

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:

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

Lingering moisture and some mid-level energy from the developing trough over the west coast will help spark some scattered showers and weak thunderstorms over the Northwest Slope and Northern Mountains this afternoon. Activity should be limited in spatial coverage with max 1-hr rain rates up to 0.25 inches are possible. Some brief gusty winds are possible with the high-based storms. Temperatures also rebound with highs 10-15°F warmer than yesterday. As anticipated, flooding is not forecast.

Primetime: 1PM to 9PM

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

Should be a dry day across these regions with some broken cloud cover this afternoon. Some light rainfall may be possible over Jackson County near the Divide, but on trace amounts of accumulation are forecast. High temperatures are forecast in the 70°Fs over the adjacent plains/Urban Corridor and 80°Fs for the Southeast Plains. Flooding is not forecast.