Issue Date: Monday, September 4, 2017
Issue Time: 09:40AM MDT

— Flooding is NOT expected today

A few high clouds are present this morning over the Front Range and Central Mountains. Smoke from the wildfires in Idaho and Montana continue to limit visibility over the northern portion of the state and eastern plains as seen in the visible satellite image below. Visibility will be reduced to 2 to 4 mile range in the heaviest smoke over the eastern plains. The high pressure continues to sit west of the state, but a cold front is expected to drop south over the eastern plains late this afternoon and push through the rest of the plains overnight. As the front moves south, this may give some relief to northeast portion of the state from the hazy skies and warm temperatures. West of the Continental Divide, the ridging pattern will continue to encourage high temperatures and entrain smoke into the northern portion of the state.

There is a chance for a few stronger storms to form along the cold front later this afternoon and evening as well as with upslope flow in climatologically favored regions. The best chance for showers and thunderstorms is along the Palmer Ridge, Southeast Mountains and San Juan Mountains. Storm coverage will increase over the high terrains when compared to the last couple of days. With Precipitable Water (PW) values in the 0.6 – 0.7 inch range, storms are expected to be short-lived and have limited rainfall totals. Gusty winds may accompany the stronger storms that form, especially along the cold front. The passage of the cold front later this evening and overnight will reduce low temperatures and bring relief from the high temperatures tomorrow.

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 Mountains, Raton Ridge, Southeast Plains, San Juan Mountains, Palmer Ridge:

Sunny this morning becoming partly cloudy this afternoon with increased coverage of storms over the higher terrains. Showers and thunderstorms are expected to initiate later this afternoon and evening and stronger storms will likely produce gusty winds. Max 1-hr rain rates up to 0.6 inches (east) and 0.4 inches (west). Flooding is not expected today.

Primetime: 12PM to 8PM

Front Range, Urban Corridor, Northeast Plains:

Sunny this morning with smoke. Reduction in smoke expected this afternoon with the passage of a cold front. Shower coverage is expected to increase over the Front Range, but limited rainfall will reach the surface. Storm totals are expected to be under 0.1 inches. Flooding is not expected today.

Primetime: 1PM to 8PM

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

Sunny this morning becoming partly cloudy this afternoon over the higher terrains. Temperatures are expected to reach the mid-90s in the lower elevations. Isolated showers may occur over the southern high terrains, but storm totals are expected to be under 0.1 inches. The north portions of these regions will have some reduction in visibility due to the fires in Idaho and Montana.

Primetime: 1PM to 8PM

Issue Date: Sunday, September 3, 2017
Issue Time: 7:20AM MDT

— Flooding is NOT expected today

A persistence forecast is expected for Colorado for today. As shown in the water vapor image, below, the upper-level ridge continues to be positioned just west of Colorado. Air is being forced to subside to its east, causing very warm temperatures at the surface. Mostly sunny skies will once again quickly boost temperatures this morning, with afternoon highs topping out another 2-5 F warmer than Saturday’s already warm temperatures. Thus, highs up to 15F above normal will be possible. Fortunately, humidity values will drop enough during the afternoon to limit the heat index. Some marginal moisture will continue to remain across southern Colorado, where isolated showers and weak thunderstorms are once again expected. Rainfall rates are expected to top out at or below Saturday’s light intensity. Thus, flooding is not expected today.

As was observed on Saturday, hazy conditions are again expected in northeast Colorado as smoke particles from the WA/ID/MT wildfires gets advected into Colorado. This may actually shave off a few degrees of heat for areas that are under the densest smoke.

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 Mountains, Raton Ridge, Southeast Plains, San Juan Mountains:

Sunny this morning, then turning partly cloudy and hot with isolated showers and weak thunderstorms in the afternoon and early evening. Storm coverage is expected to be lower than on Saturday. Max 1-hour rain rates up to 0.35 inches. Gusty winds could accompany the strongest cells. Flooding is not expected today.

Primetime: 12PM to 8PM

Front Range, Urban Corridor, Palmer Ridge, Northeast Plains:

Sunny early, then turning partly cloudy and very warm. An isolated shower or weak thunderstorm cannot be ruled out in the higher terrain south of I-70, however, little if any rainfall will reach the surface. Flooding is not expected today.

Primetime: 1PM to 7PM

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

Sunny early then partly cloudy and hot with temperatures reaching 100+ F in the lower elevations. An isolated shower or storm cannot be ruled out across southern areas. Max 1-hour rain rates up to 0.2 inches and gusty winds will be possible with the strongest cells. Flooding is not expected today.

Primetime: 1PM to 8PM

Issue Date: Saturday, September 2, 2017
Issue Time: 9:30AM MDT

— Flooding is NOT expected today

A disturbance swiftly moved southeastward across Colorado yesterday, paving the way for the recovery of the western North American upper-level ridge (see water vapor image below). And what a recovery it will be! The ridge is expected to strengthen throughout the day, sending temperatures to as much as 15F above normal statewide. Precipitable Water has dropped by 20-30% in the past 24 hours and is now in the 0.5 – 0.75 inch range. Some further drying of the atmospheric column is expected today. Enough moisture will persist for isolated to widely scattered shower and weak thunderstorm activity in the climatologically favored Southeast Mountains and San Juans. However, rain rates are expected to remain well below flood threat levels.

With the mostly sunny and hot weather, please remember to stay hydrated if you are planning on spending significant time outdoors.

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 Mountains, Raton Ridge, Southeast Plains, San Juan Mountains:

Sunny this morning, then turning partly cloudy and very warm with isolated to scattered showers and thunderstorms in the afternoon and early evening. Max 1-hour rain rates up to 0.4 inches. Gusty winds could accompany the strongest cells. Flooding is not expected today.

Primetime: 12PM to 8PM

Front Range, Urban Corridor, Palmer Ridge, Northeast Plains:

Sunny early, then turning partly cloudy and very warm. An isolated shower or weak thunderstorm cannot be ruled out especially in the higher terrain south of I-70. Max 1-hour rain rates up to 0.25 inches. Flooding is not expected today.

Primetime: 1PM to 7PM

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

Sunny early then partly cloudy and hot with temperatures reaching the upper 90s F in the lower elevations. An isolated shower or storm cannot be ruled out especially in southern areas. Max 1-hour rain rates up to 0.2 inches and gusty winds will be possible with the strongest cells. Flooding is not expected today.

Primetime: 1PM to 8PM

Issue Date: Friday, September 1, 2017
Issue Time: 10:15AM MDT

— LOW flood threat for Junkins, Beulah Hill and Hayden Pass fire scars
— LOW flood threat for Raton Ridge

Unsettled weather will continue on this first day of September, though mainly limited to southeast Colorado. As shown in the water vapor image, below, a strong disturbance is noted across northwest Colorado. Mid-level upward motion to its east is causing extensive mid and high clouds over central and eastern parts of the state. Isolated showers are already showing up on the Pueblo NWS radar. As the disturbance slowly moves east-southeast, expect enough sunshine to cause an increase in shower and storm activity mainly across the southern High Country. Moisture has increased sharply over the past 24 hours with Precipitable Water at 0.94 inches at Denver and 0.76 inches at Grand Junction this morning. Notable drying will occur in the wake of the disturbance, but moisture will continue to stay elevated in the southeast and south-central parts of the state. At the surface, a weak low-pressure was noted in east-central Colorado. This is expected to intensify modestly with the lee side trough development this afternoon. This will act to focus the strongest storms on its southeast side.

Putting it all together now, we expect scattered/numerous showers and storms in the southern High Country including the Southeast Mountains and adjacent foothills. Rainfall rates will be below flood threat levels for most locations. However, the fire scars in the Southeast Mountains will continue to be under a Low flood threat for mud flows and flash flooding due to the high probability of moderate rainfall rates. Additionally, a Low flood threat has been posted for the Raton Ridge where the best instability and upslope flow could cause an isolated storm or two capable of producing heavy rainfall and flash flooding or small stream flooding.

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 Mountains, Raton Ridge, Southeast Plains:

Partly cloudy this morning numerous showers and thunderstorms developing by early afternoon. Highest coverage will be over the higher terrain as well as the adjacent foothills. Max 1-hour rain rates up to 1.1 inch closer to the foothills and 1.4 inches across the eastern plains. A Low flood threat has been issued for the Junkins, Beulah Hill and Hayden Pass scars for mud flows and flash flooding. A Low flood threat has also been posted for the Raton Ridge for isolated flash flooding and small stream flooding.

Primetime: 1PM to 9PM

Front Range, Urban Corridor, Palmer Ridge, Northeast Plains:

Partly cloudy this morning isolated to scattered showers and thunderstorms possible this afternoon. Highest coverage will be over the higher terrain east of the Continental Divide as well as the Cheyenne and Palmer Ridges. Farther east, coverage will be isolated. Max 1-hour rain rates up to 0.7 inches. Flooding is not expected today.