Issue Date: 6/5/2016
Issue Time: 9:31 AM

A LOW FLOOD THREAT IS FORECAST FOR PORTIONS OF THE RATON RIDGE, SOUTHEAST MOUNTAINS, URBAN CORRIDOR, SOUTHEAST PLAINS, FRONT RANGE, CENTRAL MOUNTAINS, AND PALMER RIDGE.

The upper-level ridge that has been in control of the forecast will remain over the area, albeit a slightly dampened version due to an upper-level low spinning over northern CA/southern OR. Underneath the ridge resides a weak wave (disturbance), which will rotate across Colorado within the northwest flow aloft. This wave (highlighted in the water vapor image below) will kick off an increase in showers and thunderstorms this afternoon/evening. Scattered storms will occur across the Southeast Mountains, San Juan Mountains, and Raton Ridge, and a few will move over the adjacent lower elevations/plains due to more westerly flow aloft. Periods of moderate-to-heavy rainfall will occur under the stronger storms, especially over the Southeast Mountains and Raton Ridge, as well as the adjacent Southeast Plains. A couple of storms may reach severe thresholds for hail and gusty winds.

Isolated-to-widely scattered showers/thunderstorms are expected over the Northern Mountains, Central Mountains, Southwest Slope, Front Range, Urban Corridor, Palmer Ridge, and Northeast Plains regions. Brief heavy rainfall will occur underneath the stronger storms in the areas highlighted by the low flood threat.

Otherwise, the weather story will be the heat again today, especially across western Colorado where high temperatures will be 10-15 degrees above average. A few locations in the Colorado River valley near the CO/WY border will push into the middle 90s. For eastern Colorado, temperatures will be warm, but not to the same extent as western Colorado. High temperatures will be in the 70s and 80s, with the warmest spots in the Arkansas River valley.

For more information regarding timing and rain rates of today’s thunderstorms, please see the zone-specific discussions below.

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

Northeast Plains, Urban Corridor, and Palmer Ridge:

Isolated-to-widely scattered showers/thunderstorms, with the coverage decreasing from the west to east. The far Northeast Plains will remain dry and underneath mostly sunny skies. Brief periods of moderate-to-heavy rainfall will occur under the stronger storms, mainly over the Palmer Ridge and southern portions of the Urban Corridor. Maximum rain rates vary:

Northeast Plains: 0.8-1.2 inches/hour
Urban Corridor: 1.0-1.5 inches/hour
Palmer Ridge: 1.0-1.6 inches/hour

Timing: 1 PM – 10 PM

Central Mountains, Northern Mountains, and Front Range:

Isolated-to-widely scattered showers/thunderstorms expected. Storms over the Northern Mountains will remain high-based, producing more gusty winds and lightning than rain. For the Front Range and Central Mountains, storms will produce a bit more rain, and southern extents have been included in the low food threat area. Maximum rain rates will be:

Northern Mountains: 0.15-0.25 inches/hour
Central Mountains: 0.7-1.1 inches/hour
Front Range: 0.6-1.0 inches/hour

Timing: 1 PM – 9 PM

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

Scattered showers and thunderstorms expected, and a few will become strong-to-severe. The best chance at heavy rain will be across the Southeast Mountains, Raton Ridge, and western portions of the Southeast Plains. These areas have been included in the low flood threat. Maximum rain rates will be:

Raton Ridge, Southeast Plains, and Southeast Mountains: 1.8-2.2 inches/hour
San Juan Mountains: 0.6-0.8 inches/hour
San Luis Valley: 1.0-1.8 inches/hour

Timing: 1 PM – Midnight

Northwest Slope, Grand Valley and Southwest Slope:

Mostly sunny and hot will be the main weather story today, with only a couple high-based showers/weak thunderstorms possible over the higher terrain. Any storm activity will produce more gusty winds and lightning than rain. Any storm activity will diminish after peak heating, coming to an end during the late evening.

Issue Date: Saturday, June 4th, 2016
Issue Time: 9:00AM MDT

— There is No flood threat today.

The water vapor image, below, continues to show the western U.S. ridge firmly in place. Colorado is displaced far enough east to be largely under its influence of very hot temperatures. The western part of the state will continue to be very warm, while the eastern part is just warm. Today’s Precipitable Water (PW) have risen a touch compared to yesterday morning, partly from wet soils and partly from weak moisture advection from the east. However, with the ridge in place and strong subsidence, rainfall will be hard to find. Isolated scattered showers or weak thunderstorms will likely pop up in the Southeast Mountains and San Juans during peak heating. But rainfall amounts will be well below critical levels.

Snowmelt continues in earnest today with up to 2.5 inches of snow water equivalent loss expected over the “luckiest” of locations. As such, high elevation streams continue to rise with some getting close to action levels; however, flooding is not expected today. A reassessment will be required for tomorrow (Sunday) and especially next week.

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, scroll below the map.

Issue Date: Friday, June 3rd, 2016
Issue Time: 9:00AM MDT

— There is No flood threat today.

Today’s Precipitable Water (PW) chart, below, says it all. PW values have dropped to below 0.6 inches across all stations and this morning’s levels are now near or below their seasonal averages. For reference, the Boulder station’s average (blue line below) for today is 0.57 inches. Temperatures will be near seasonal averages again today, and may be held down a few degrees by a mid-level cloud deck streaming in from the northwest. A building ridge to the west will provide subsidence statewide and rainfall is not expected today.

Area streams continue to move upward and snowmelt increases. However, this morning analysis shows that all streams all below minor flood stage and are expected to stay that way through the weekend. However, hikers and water-goers should be aware that there is a daily cycle to many high elevation streams and snowmelt is in progress. An example is shown below for the Dolores River. There are two things to note. First, in this case, there is about a 1 foot difference in river levels between the peaks and troughs. This may be even higher when temperatures are particularly warm. Second, in this case the peaks occurs well into the evening, due to the delayed effect of the runoff. This gage is quite representative of other locations.

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, scroll below the map.

Zone-Specific Forecasts:

Front Range, Urban Corridor, Northeast Plains, Palmer Ridge, Southeast Plains, Southeast Mountains, Raton Ridge, San Juan Mountains, San Luis Valley:

Partly sunny and warm with some mid-level clouds continuing to stream in from the northwest. Rainfall is not expected, neither is flooding.

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

Mostly sunny and very warm today. Rainfall is not expected, neither is flooding.

Issue Date: Thursday, June 2nd, 2016
Issue Time: 9:40AM MDT

— There is no flood threat today.

As seen in the water vapor image, below, the cut-off low skirting along the US-Mexico border is finally southeast of Colorado. Following in its wake is the first strong ridge seen during the young summer season. The ridge will continue to build north-northeast promoting strong height rises over the state, implying strong subsidence above the boundary layer. A few isolated thunderstorms are still possible given marginal moisture east of the Continental Divide. However, flooding is not expected. Much warmer temperatures, closer to seasonal normals, will be seen across the state.

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, scroll below the map.