Issue Date: 7/16/2015
Issue Time: 10:15AM

— Flooding is NOT expected today

After the passage of a weak disturbance yesterday, substantial drying is noted this morning over Colorado. Precipitable water (PWs) has decreased from a range of 1 – 1.2 inches yesterday to 0.55 – 0.8 today. As shown in the water vapor image, below, the drying over Colorado is part of a larger scale tongue of dry air that extends all the way into the eastern Pacific Ocean. Interestingly, this drying contrasts sharply with a moist axis being supplied by the impressive Hurricane Dolores. However, the moisture is expected to remain south of Colorado today. Please check out our Flood Threat Outlook, updated at 3PM this afternoon, to see how Dolores may impact Colorado’s weather in the coming days.

For today, we expect sunny skies this morning to lead to isolated to scattered thunderstorms over the higher terrain by early afternoon. Another batch of storms will be possible later this afternoon in the Front Range and Urban Corridor as a disturbance moves closer from the northwest (see water vapor imagery). However, a dry atmosphere will limit rain rates to about 0.6 inches per hour. Thus, flooding is not expected today. As in the past few days, the strongest thunderstorms will be capable of producing gusty winds, up to 60 mph.

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.

Zone-Specific Forecasts

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

Mostly sunny early, then turning partly cloudy. Isolated to widely scattered thunderstorms will form over the higher terrain and last from early afternoon to around sunset. Max 1-hr rain rates up to 0.5 inches will be possible, along with gusty winds up to 55 mph. No flooding is expected today.

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

Mostly sunny early with isolated to scattered thunderstorms forming by early afternoon. Highest coverage will be over the higher terrain, as well as the Front Range/Urban Corridor near the Wyoming border. Maximum 1-hr rain rates up to 0.6 inches will be possible, along with gusty winds up to 60mph. No flooding is expected today.

Issue Date: 7/15/2015
Issue Time: 10:10 AM

A MODERATE FLOOD THREAT IS FORECAST FOR PORTIONS OF THE SOUTHEAST PLAINS AND RATON RIDGE.

A LOW FLOOD THREAT IS FORECAST FOR PORTIONS OF THE FRONT RANGE, URBAN CORRIDOR, NORTHEAST PLAINS, SOUTHEAST PLAINS, PALMER RIDGE, RATON RIDGE, SOUTHEAST MOUNTAINS, SAN JUAN MOUNTAINS, SOUTHWEST SLOPE, GRAND VALLEY, CENTRAL MOUNTAINS, NORTHERN MOUNTAINS, AND NORTHWEST SLOPE.

The same overall pattern that has governed the Continental US weather over the past week or so continues today, as the upper-level ridge remains anchored over the south-central US and an upper-trough sits along the west coast. This will continue the stream of subtropical moisture across Colorado, albeit moisture will be slightly less than yesterday. Embedded in the flow are a couple of weak disturbances that will work across the state, but they will not have the same “punch” as yesterday. This is due to the fact that their time of passage will not coincide quite as well with peak daytime heating, thus a downtick in thunderstorm numbers today.

The best coverage of storms will occur across the High Country where orographic effects once again play a role in storm development, and across the far eastern plains where a surface trough and greater surface moisture will be present. Isolated thunderstorms will be possible elsewhere. Much like yesterday, all strong storms, regardless of location, will hold the potential to produce brief moderate-to-heavy rain. With that said, storm motions will be quicker than yesterday, helping to limit the flood threat. Burn scars, urban areas, unstable soils, and locations that received heavy rainfall yesterday will be the primary concerns for flooding threats today.

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.

Zone-Specific Forecasts

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

Isolated-to-scattered thunderstorms expected this afternoon and evening, with stronger storms holding the potential to produce brief heavy rain. Maximum rain rates will be 0.8-1.4 inches/30-45 minutes.

Near the CO/KS border, higher surface dewpoints and organization along a surface trough will allow for greater max rainfall rates from strong-to-severe thunderstorms of 2.0-2.5 inches/hour. The main threat from any severe thunderstorms will be heavy rain, lightning, and strong winds. Some small hail will likely be present, as well.

Timing: 1 PM – 11 PM

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

Scattered showers and thunderstorms are expected today and tonight, although coverage will be slightly less than yesterday. With moisture down a bit from yesterday, and storm motions expected to be quicker, the flood threat has been reduced, but not eliminated. Unstable soils from previous days’ rainfall is still a concern, as well as burn scars and urban areas. Rain rates will generally be in the 0.4-0.8 inches/hour range, but stronger storms could produce rainfall at 0.8-1.2 inches/hour.

Timing: 11 AM – 10 PM, with one or two isolated showers continuing into the early morning hours.

Issue Date: 7/14/2015
Issue Time: 10:17 AM

A MODERATE FLOOD THREAT HAS BEEN ISSUED FOR PORTIONS OF THE PALMER RIDGE, NORTHEAST PLAINS, AND SOUTHEAST PLAINS.

A LOW FLOOD THREAT HAS BEEN ISSUED FOR PORTIONS OF THE NORTHERN MOUNTAINS, NORTHWEST SLOPE, GRAND VALLEY, CENTRAL MOUNTAINS, SAN JUAN MOUNTAINS, SOUTHEAST MOUNTAINS, RATON RIDGE, FRONT RANGE, URBAN CORRIDOR, PALMER RIDGE, NORTHEAST PLAINS, AND SOUTHEAST PLAINS.

Subtropical moisture will continue to stream into Colorado along the western periphery of the upper-level ridge centered over the south-central US. The ridge has slid a bit further east today, which will allow fairly deep moisture to overspread the state. This, combined with a few weak disturbances embedded in the flow aloft, will allow for more coverage of thunderstorms today, each holding the potential to produce bouts with heavy rain. Weak mid-level flow will result in slower storm motions and increases the potential for excessive rainfall in any one location. Thus, the widespread low flood threat area as any stronger storm, no matter the location, will have the potential to produce heavy rainfall. Urban areas, burn scars, and locations with unstable soil (i.e., Chafee County), will be of primary concern today.

Additional primary concerns exist across the eastern third of Colorado, where scattered strong-to-severe storms are expected to develop this afternoon and evening. The main threats from these storms will be strong winds and large hail, as well as heavy rain. Rain rates will be sufficiently high to cause urban and rural flooding/ponding, and small streams that react quickly will need to be monitored should heavy rain move over their basins. Later in the evening, storms from the west will congeal into one or two thunderstorm clusters, producing heavy rain and strong winds as they move eastward over portions of the Palmer Ridge, Northeast Plains, and Southeast Plains, reaching Kansas during the early overnight hours.

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.

Zone-Specific Forecasts

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

Scattered thunderstorms are expected today and tonight, with stronger storms capable of producing heavy rainfall. Maximum rain rates vary across the regions, so let’s break it down…

Urban Corridor and Raton Ridge: 0.8-1.4 inches/hour
Palmer Ridge, Northeast Plains, and Southeast Plains: 2.0-3.0 inches/hour

Timing: 11 AM – Midnight

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

Scattered showers and thunderstorms expected to begin by 11 AM, continuing through the afternoon and evening, with a few lingering overnight and into tomorrow morning. With the amount of moisture available across all regions, heavy rainfall will be possible from a stronger storm in any of the regions. Thus, the widespread low flood threat area. Maximum rain rates will be 0.8-1.2 inches/hour. Thunderstorms will favor the higher terrain, as orographic effects will play a role in storm development and storm motions will not move them quickly over lower elevations. Unstable soils and burn scars will be of primary concern for flash flooding/mud flow/debris slide issues.

Timing: 11 AM – 10 PM will be primetime, but a few thunderstorms (and heavy rain threat) will linger into tomorrow morning.

Issue Date: 7/13/2015
Issue Time: 10:05 AM

LOW FLOOD THREAST IS FORECAST FOR PORTIONS OF THE FOLLOWING REGIONS: SOUTHWEST SLOPE, SAN JUAN MOUNTAINS, GRAND VALLEY, CENTRAL MOUNTAINS, NORTHERN MOUNTAINS, NORTHWEST SLOPE, FRONT RANGE, AND URBAN CORRIDOR.

The upper-level high pressure ridge will remain in charge of the flow aloft across Colorado today, with southwest flow continuing the stream of subtropical moisture into the state. Absent from the upper-level environment is a trigger mechanism, so expect today to feature scattered showers and thunderstorms over the High Country and, with the mean flow directed from the west-southwest, a few isolated storms will move over adjacent low elevations of Eastern Colorado, as well. Precipitable water values are above average across western Colorado, so heavy rain and flash flooding will be possible underneath stronger thunderstorms, especially for areas of SW Colorado that received heavy rain yesterday.

For the lower elevations of eastern Colorado, it will be a fairly typical July day with isolated thunderstorms moving off the mountains and over portions of the Palmer Ridge, Urban Corridor, Northeast Plains and Southeast Plains. Further east over the Southeast Plains, near the CO/KS border, a strong-to-severe thunderstorm or two will likely develop this afternoon and evening, with the main threats being lightning, hail, brief heavy rain, and strong winds.

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.

Zone-Specific Forecasts

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

Isolated thunderstorms expected this afternoon and evening, with the best coverage near the mountains. A couple strong-to-severe storms will be possible across eastern portions of the Southeast Plains, mainly near the CO/KS border, where steep mid-level lapse rates and low-level moisture will be best. Rain rates will generally be 0.25-0.65 inches/hour, but stronger thunderstorms could produce rain at 0.6-1.2 inches/hour.

Primetime: 2 PM – 10 PM

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

Scattered showers and thunderstorms are expected through today and into the nighttime hours as ample moisture continues to stream in from the southwest. Orographic forcing and daytime heating will be the main players in triggering the activity, so expect thunderstorms to initially develop over the higher ridges and move to the east-northeast with time. Rain rates will typically be 0.3-0.6 inches/hour, but stronger thunderstorms will potentially produce rainfall at 0.8-1.4 inches/hour. Some dry air below cloud base will help limit the flooding threat, as will storm motions. Areas that received heavy rainfall yesterday will be of main concern with regards to flash flooding issues today.

Timing: 11 AM – 10 PM, but a few showers and thunderstorms will persist into tomorrow morning as the moist, southwest flow continues.