Issue Date: 7/2/2017
Issue Time: 8:00 AM

NO FLOOD THREAT IS FORECAST.

Today’s forecast features an uptick in showers/thunderstorms as a mid-level disturbance pushes across the region during the afternoon and evening hours. The increase in shower/thunderstorm coverage does not come with an increase in the flood threat, however, due to high temperature-dewpoint spreads in the low-levels and at the surface. I have annotated the current position of the 40°F dewpoint line on the surface observation map below. This line will shift east through the morning and into the afternoon hours as dry air aloft mixes down to the surface, pushing the best surface moisture over the far eastern plains. Even so, where the surface moisture hangs on, the high temperature will be in the low-to-mid 90’s, resulting in an “Inverted-V” atmospheric profile. The “Inverted-V” is indicative of efficient evaporation of falling precipitation, which will limit the rain rates at the surface.

West of the 40°F dewpoint line, and over the mountains especially, shower/thunderstorm activity will produce mainly light rain and gusty winds due to the same aforementioned “Inverted-V” atmospheric profile. The main threat will be the potential for dangerous cloud-to-ground lightning with thunderstorms, so remember that “if thunder roars, go indoors.”

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

Front Range, Southeast Mountains, and Urban Corridor:

Scattered showers/thunderstorms are expected to develop over the mountains around 11 AM, spreading eastward with time, and impacting the Urban Corridor by 1 PM. Most activity will wind down by 10 PM, but a few lingering showers/thunderstorms will hang around into the early morning hours. Maximum rain rates will be 0.3-0.6 inches/hour for the mountains, and 0.4-0.8 inches/hour for the Urban Corridor.

Palmer Ridge, Northeast Plains, and Southeast Plains:

Scattered showers/thunderstorms are expected to develop around 2 PM, continuing through the evening hours, and exiting the state to the east by 1 AM. A few storms near the CO/KS and CO/NE border will become strong-to-severe, with the main threats being damaging straight-line winds and large hail. Brief periods of heavy rain will also attend the strongest storms near the border, but will remain under flash flood threat thresholds. Maximum rain rates are as follows:

Western half of the Palmer Ridge: 0.4-0.8 inches/hour
Eastern half of the Palmer Ridge: 0.8-1.2 inches/hour
Northeast Plains and Southeast Plains: 1.25-1.75 inches/hour

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

Scattered showers/thunderstorms are expected to develop later this morning (between 10 AM and Noon), continuing through the afternoon and evening hours, diminishing after sunset, and coming to an end around midnight. Light rain and gusty winds will be the main impact from this activity, but dangerous cloud-to-ground lightning will be the main threat from thunderstorms. Maximum rain rates are expected to remain low at 0.25-0.5 inches/hour.

Issue Date: 7/1/2017
Issue Time: 9:00 AM

NO FLOOD THREAT IS FORECAST.

The general forecast for this period across Colorado can be summed up like this: warm and dry, with plenty of sunshine. We can thank a warm, subsident airmass that is building overhead in advance of an upper-level trough along the West Coast for this pleasant outlook. However, as is the case much of the time for Colorado, there is an exception to the rule.

For southern Colorado, mainly for the San Juan Mountains, San Luis Valley, Southeast Mountains, Raton Ridge, and Southeast Plains regions, a few isolated thunderstorms will rumble during the afternoon and evening hours as daytime heating and orographic effects overcome the cap. This activity may occur as far north as the southern reaches of the Front Range/Urban Corridor/Palmer Ridge/Northeast Plains. Flooding is not expected, as moisture is fairly shallow and the environmental support is marginal for any organized, strong activity. The strongest thunderstorms will occur across the Southeast Mountains, Raton Ridge, and Southeast Plains, with the main threat being severe winds and hail.

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

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

Mostly sunny, warm, and dry for most as the subsident airmass keeps much of the area capped off. A few isolated thunderstorms will rumble during the afternoon and evening hours, as daytime heating and orographic effects pair up to overcome the cap. Generally speaking, most storms will produce gusty winds and lightning, with periods of light-to-moderate rainfall. A couple stronger storms will become marginally severe, mainly over the Southeast Mountains, Raton Ridge, and Southeast Plains, producing damaging wind gusts, lightning, and brief periods of heavy rainfall. No flooding is expected, but street/field ponding will be possible in poorly drained areas underneath heavy rainfall. The maximum rain rates are as follows:

Front Range, Urban Corridor, Raton Ridge, and Northeast Plains: 0.4-0.8 inches/hour
Southeast Mountains: 0.5-1.0 inches/hour
Raton Ridge: 0.6-1.0 inches/hour
Southeast Plains: 0.8-1.2 inches/hour

Timing: 2 PM – 10 PM

San Juan Mountains, and San Luis Valley:

Mostly sunny and dry for the majority of the area, with a couple isolated thunderstorms expected to rumble during the afternoon/evening hours. The main threats will be gusty winds (up to 45 mph) and lightning, with small hail and brief periods of light-to-moderate rainfall. The maximum rain rates will be 0.4-0.7 inches/hour for the San Juan Mountains and 0.5-1.0 inches/hour for the San Luis Valley.

Timing: 1 PM – 9 PM

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

Mostly sunny, warm, and dry is the name of the weather game today for these regions. There is a very low chance (~10%) that a shower/weak thunderstorm may develop over the higher terrain of the Central Mountains and Southwest Slope during the afternoon, producing nothing more than a few sprinkles and some gusty winds.

Issue Date: Friday, June 30, 2017
Issue Time: 11:00AM MDT

— Low Threat for Southeast Plains and Raton Ridge

An upper level trough moved into CO from the north last night helping decrease temperatures across the state and increase moisture east of the Continental Divide. Over the western slope, temperatures will be about 5F cooler than climatology. Winds will also decrease lowering the fire threat for today.

East of the Continental Divide, overnight scattered showers accompanied the upper level trough over the Northeast Plains, leaving a moist, stable layer near the surface this morning. For example, the current temperature and dew point readings over Akron are 55F/52F. The ongoing scattered showers and cooler temperatures will limit the amount of instability for severe storms over the Front Range, Urban Corridor, Palmer Ridge and Northeast Plains. As pockets of clouds burn off midday, it will be possible for some instability to form. Therefore, scattered showers over the over higher terrain and the Palmer Divide are forecasted in this cloud-free environment. Rain rates up to 1” will be possible for the isolated thunderstorms that form.

Further south, adequate low-level moisture combined with upslope winds continue to support cloudy conditions this morning. However, warmer morning temperatures and strong June sun will cause this moisture to mix out earlier in the day. The clearer skies will allow for a band of instability this afternoon along the Southeast Mountains and Raton Ridge. High moisture paired with backing winds will create a favorable environment for strong to severe storms. The slow motion movement of the storms (15 kts) will cause rain rates up to 2 inches per hour. The severe storms that form could have hail up to 2 inches in diameter and 60 mph gusts. Storms are expected to diminish by midnight.

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 :

Southeast Plains and Raton Ridge:

 Partly cloudy this morning with sunny skies this afternoon. Daytime heating, low-level moisture and backing winds will provide an environment favorable for strong, slow-moving severe thunderstorms this afternoon. Rain rates up to 2 inches are possible as well as hail as large as 2 inches in diameter and 60 mph gusts. A Low flood threat has been posted for isolated flash flooding, debris slides and mud flows.

Primetime: 2PM to 1AM

Front Range, Urban Corridor, Palmer Ridge, Northern Mountains, Northeast Plains, Southeast Mountains, Central Mountains, San Luis Valley:

 Partly cloudy and cool for today with some light showers this morning. A few storms could develop where clouds dissipate early over the high country and Palmer Ridge. Max 1-hour rainfall up to 1 inch. Storms will begin to dissipate within a few hours of sunset.

Primetime: 3PM to 12AM 

Northwest Slope, Grand Valley, Southwest Slope and San Juan Mountains:

Sunny today with cooler temperatures. Decreasing winds will limit the fire danger for today. Temperatures will be 5F cooler than climatology.

Issue Date: Thursday, June 29th, 2017
Issue Time: 10:40AM MDT

— Flooding is NOT expected today
— Elevated fire danger continues for western Colorado

A bit of change is in the air this morning, as hinted by the water vapor image below. The upper-level trough that entered the US Pacific Northwest 48 hours ago is situated over the Continental Divide this morning. It is bringing with it seasonably strong dynamics that will provide large-scale upward motion across Colorado throughout this afternoon and evening. The limiting factor regarding the heavy rainfall threat, however, is once again the lack of low level moisture. Although dew point temperatures this morning are as high as the mid-50s F in eastern Colorado, this is an illusion as this moisture is quite shallow. With another deep boundary layer expected today (courtesy of the June sun + clear skies), expect most of the meaningful moisture to “mix out” leaving a few clouds and isolated showers and a weak thunderstorm for most.

The one exception will be in the Southeast Plains, where a stationary frontal boundary combined with another fresh cool front arriving this afternoon will act as a weak focal point for storm activity. Much like the past two afternoons, severe weather (gusty winds and hail) will likely be the main impact. Isolated short-term heavy rainfall, while likely, is not anticipated to exceed flood threat intensity. Thus, no flood threat is expected today.

Out west, the elevated fire danger continues today, and will be further exacerbated by dry lightning that could accompany any weak storms that manage to form.

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:

Northeast Plains, Southeast Plains:

Partly cloudy with scattered thunderstorms likely after noon, lasting into the late evening for far eastern areas. Max 30 minute rainfall up to 1.1 inch and max 1-hour rainfall up to 1.5 inches will be just under flood threat intensity; thus no threat is issued. However, severe weather will be likely, including hail up to 1.75 inches and gusty winds up to 75 mph.

Primetime: 2PM to Midnight (near Kansas border)

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

Sunny early then partly cloudy with isolated to scattered showers and weak thunderstorms possible during the afternoon. Max 30-minute rainfall 0.6 inches. Flooding is not expected today.

Primetime: 1PM to 8PM

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

Mostly sunny and cooler today. An isolated shower or weak thunderstorm cannot be ruled out over higher terrain. Max 1-hour rainfall up to 0.2 inches. Gusty winds and dry lightning will be more of a threat than rainfall. An elevated fire danger continues to exist today, with a Red Flag warning in effect for most of the area. Please stay tuned to local National Weather Service offices for updates.

Primetime: 11AM to 7PM