Issue Date: Wednesday, July 20^th, 2022
Issue Time: 10:45AM MDT

— A MODERATE flood threat has been posted for parts of the Palmer Ridge, Southeast Mountains and Raton Ridge
— A LOW flood threat has been posted for parts of the Southeast Plains, Central Mountains, San Juan Mountains and San Luis Valley
— Fire-Burn Forecast Summary: 3 burn areas under MODERATE threat; 3 burn areas under LOW threat; click HERE for more info

An active weather pattern remains in store today for most of central and southern Colorado as plenty of monsoonal moisture remains overhead. This morning’s PW at Grand Junction measured 0.94 inches, down slightly from yesterday but still well above seasonal normal. The Denver sounding was again unfortunately unavailable, but estimates suggest values in the 0.9 – 1.0 inch range. PW in the 1.0 – 1.3 inch range is estimated across southeast Colorado. Near the surface, dewpoint temperatures continue to measure well above 50F for most elevations below 8,000 feet over central and southern Colorado. Some boundary layer drying has occurred over northern areas, and rain chances will be much lower there.

As shown in the water vapor image, above, clockwise flow around the monsoonal upper-level ridge places Colorado in WNW steering flow as of this morning. One disturbance, associated with yesterday’s storms is currently leaving the southeast part of the state, producing subsidence in its wake. This will delay convection over the Southeast Plains until the later afternoon hours. Another disturbance is noted along the UT/CO border. This, along with our usual diurnal upslope circulation, will act as the main forcing of afternoon and evening storms over our higher terrain, spilling into the foothills and plains thereafter. CAPE instability up to 1,100 J/kg will be available this afternoon, which given the boundary layer moisture will be plenty for sustaining heavy rainfall. Steering flow will be in the 20+ mph range north of I-70 but in the 15-20mph range over southern areas, promoting the potential for heavy rain accumulation. Steering flow will also veer to be more NW or even NNW throughout the day, which will allow for a better chance for storms to interact and anchor to the higher terrain. Because of this, a MODERATE flood threat is warranted for climatologically favored parts of the state including the Palmer Ridge extending south through the I-25 corridor to New Mexico. Antecedent wet soils will also help promote more efficient runoff rates. In surrounding areas, a LOW flood threat has been posted.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

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

Mostly sunny early then partly to mostly cloudy with scattered to numerous showers and storms developing by early afternoon. Max 30-min rain rates up to 1.2 inches (above 6,000 feet) and 1.6 inches (eastern areas below 6,000 feet) with max 1-hour rain rates up to 1.8 inches (above 6,000 feet) and 2.5 inches (eastern areas below 6,000 feet.

A MODERATE flood threat has been posted for the foothills and higher terrain over the Palmer Ridge and Southeast Mountains where antecedent wet soils will further enhance rainfall runoff. A LOW flood threat has been posted for surrounding areas. Isolated flash flooding, debris slides and mud flows will be possible over the higher terrain. Over the Moderate threat area, high flows will be possible on small creeks and streams, as well as normally dry arroyos. Further east, the main threat will be isolated flash flooding as well as road flooding.

Severe weather will be possible with the strongest cells over the Southeast Plains today, with the main threats being damaging wind and possibly large hail.

Primetime: 12PM through midnight

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

Mostly sunny early then partly cloudy with isolated to widely scattered showers and storms possible this afternoon and evening. Max 30-min rain rates up to 0.5 inches possible. Aside from some nuisance ponding, flooding is NOT expected today.

Primetime: 12PM through 8PM

Issue Date: Tuesday, July 19th, 2022
Issue Time: 8:45AM MDT

— A LOW flood threat has been issued for the Central Mountains, Raton Ridge and portions of the Northwest Slope, Northern Mountains, Central Mountains, Front Range, Southeast Mountains, San Juan Mountains, Urban Corridor, Palmer Ridge and Southeast Plains
— Fire-Burn Forecast Summary:  4 burn areas under LOW threat; click HERE for more info

Today is expected to look similar to yesterday on the rainfall front with a few minor changes to the details. The passing Low to our north has pushed the center of the High south of the Four Corners region, which should keep steering flows mostly westerly with a bit more of a northerly component over eastern Colorado today. Storm motion over the northern and central portion of the state will still be rather quick with a mid-level speed just north of the border, but training storms look to be more likely, which could help increase local accumulations. This minor movement of the High should help to keep afternoon high temperatures slightly less than yesterday, although it’s still going to be quite hot with the 5920mb contour overhead.

As far as moisture, PW at Grand Junction was measured at 1.02 inches with a dew point of 52°F, so both are slightly higher than this time yesterday. Generally, PW values look to have increased over northern Colorado as well as over the far eastern plains. There’s still no sounding data at Denver, but dew points along the I-25 Corridor are a few degrees less than yesterday with PW likely in the 0.7-0.8 inch range. That means there is plenty of residual and incoming moisture rotating around the High and into the state for scattered storms to occur.

As upslope flow begins by late morning, storms should have no problem kicking off over the high terrains by early afternoon with plenty of moisture and sunshine. Outside of the Flat Tops and Grand Mesa regions over western Colorado, storms coverage should be mostly confined to the central and southern mountains today with some spillover anticipated into the adjacent eastern plains. Slightly slower steering flows south and training storms over central Colorado will cause a LOW flood threat to be issued. Some mid-level drying was noted in the Grand Junction sounding, so the stronger thunderstorms that do develop may be more likely to produce hail and strong outflow winds today. The flood threat over the adjacent plains should be limited to the elevated ridges with most storm activity winding down a couple hours after sundown.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

Central Mountains, Northern Mountains, Front Range, Southeast Mountains, Palmer Ridge, San Juan Mountains, Northwest Slope, Raton Ridge & Urban Corridor:

In the wake of the passing Low, minimal storm activity is anticipated over the Northern Mountains and northern Front Range this afternoon. A couple rounds of storms today along with slower steering flows (south) will increase the flood threat for the central and southern high terrains. Max 30-minute rain rates up to 1.1 inches and isolated storm totals up to 1.6 inches will be possible. Over the adjacent elevated ridges, max 1-hour rain rates up to 1.25 inches will be possible with the majority of the rainfall falling in 30-40 minutes. Stronger thunderstorms that develop today will be more likely to produce hail and damaging outflow winds, especially over the adjacent plains. A LOW flood threat has been issued with field ponding, road flooding and isolated mud flow/debris slides (steeper terrains) possible. Lighter showers may linger over the mountains tonight.

Primetime: 12:30PM to 11PM

Grand Valley, Southwest Slope, Southeast Plains, Northeast Plains & San Luis Valley:

Best chance for isolated rainfall today will be near the Grand Mesa and far eastern plains (central/south). However, there is a chance for some rainfall in the SLV with SE steering flows pushing storms off the San Juan Mountains into the valley. Max 30-mintue rain rates up to 0.5 inches (west) and 0.25 inches (SLV) will be possible with max 1-hour rain rates up to 1.25 inches forecast east. Strong outflow winds will be possible with any storms that develop as well as hail (most likely east). Flooding is NOT expected today.

Primetime: 12:30PM to 9PM (west/central); 3PM to 1AM (east)

Issue Date: Monday, July 18th, 2022
Issue Time: 9:30AM MDT

— Flooding is NOT expected today
— Fire-Burn Forecast Summary: 5 burn areas under LOW threat; click HERE for more info

Afternoon high temperatures will be on the rise today, so expect a VERY hot day across the state thanks to the strong ridge overhead. A Heat Advisory has been issued for northeast Colorado (elevations below 6K feet) with the hottest temperatures expected over the eastern plains. Looking at the water vapor imagery, there is quite the dry air mass to our east, but a bit of moisture (blue shades) rotating around the High into Colorado. As a trough passes to our north, the High will be slightly pushed south, but plenty of moisture and mid-level energy should remain over the state along with WSW and westerly flow aloft. PW at Grand Junction was measured at 0.99 inches, so a decent increase from this time yesterday. This should allow scattered storms to develop over the western high terrains and mountains today as the typical diurnal flow pattern sets up with daytime heating. More isolated storms are expected over the adjacent eastern plains with PW at Denver estimated around 0.75 inches with values increasing to around 0.90 inches over the plains. For areas east today, the main threat today will be strong outflow winds that develop under the stronger storm cores.

Surface moisture, especially over western Colorado and the mountains, looks sizeable enough that some quick downpours will be possible with some mid-level lift also over the area. However, moderate steering flows associated with the passing trough should keep the threat from any given storm to around 20-40 minutes. Some isolated areas of training storms may help boost local accumulations, but rain rates should remain under flood threat criteria. Therefore, flooding is NOT expected today.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

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

High temperatures today across the lower elevations will reach into the mid to upper-90°Fs with the century mark possible over the Grand Valley and far southwest corner of the state. Upper 70°Fs and 80°Fs are forecast for the mountain valleys. Best chance for storms today will be over the elevated mesas/plateaus and mountains with the best storm coverage over these central and northern forecast zones. Isolated, max 30-minute rain rates up to 0.85 inches will be possible. Where training storms set up (most likely around/near the Continental Divide, Flat Tops and Grand Mesa), isolated storm totals up to 1.4 inches will be possible over 2-3 hour period. With rain rates forecast to remain below flood threat criteria, flooding is NOT expected. Additional threats from the stronger thunderstorms that develop will be brief wind gusts around 55 mph and dangerous lighting.

Primetime: 12PM to 10PM 

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

High temperatures are forecast to reach 80°Fs for the mountain valleys, upper 90°Fs to 100°F for the I-25 Corridor/elevated ridges and between 100°F and 105°F over the eastern plains. A Heat Advisory has been issued for elevations below 6K feet over northeast Colorado. As far as rainfall, thunderstorms and showers should be more widely scattered over these higher terrains with the best storm coverage anticipated over the southern Front Range, Southeast Mountains and elevated ridges. Max 30-minute rain rates up to 0.75 inches (west) and 0.85 inches (east) with isolated totals up to 0.9 inches will be possible. A couple stronger thunderstorm may develop over the border counties, but only if storms can make it there before instability drops off with the setting sun. The main threat from the stronger storms would be strong outflow winds with max 1-hour rain rates up to 1.25 inches possible. Flooding is NOT expected.

Primetime: 12:30PM to 11PM

Issue Date: Sunday, June 17^th, 2022
Issue Time: 8:50AM MDT

— A LOW flood threat has been posted for parts of the San Juan Mountains

As easily seen in the water vapor image, below, significant drying has taken place across Colorado after a disturbance moved eastward out of the state over the past 24-hours. PW has dropped dramatically at Grand Junction from 1.22 inches yesterday to 0.79 inches this morning. As also seen in the water vapor image, a sliver of higher moisture remains right along the New Mexico border with PW likely in the 0.8 – 0.9 inch range. Closer to the surface, moisture is also maximized along the New Mexico border with dewpoints at 50F or higher at elevations as high as 8,000 feet. Steering flow remains weak and under the influence of the monsoonal upper-level ridge, which is now centered just east of the Four Corners. Steering of storms will be slightly southward to the east of the San Luis Valley but slightly northward over the San Juans, where the highest storm chances will be today. With not a cloud in the sky this morning, instability will quickly reach 1,000 J/kg CAPE or slightly higher over the southern higher terrain. With the sufficient moisture and slow steering flow, a LOW flood threat is warranted for the eastern portion of the San Juan Mountains where isolated heavy rainfall is expected with the strongest storms.

With lower moisture and weak subsidence elsewhere, the rest of Colorado will remain mainly dry today. Without the clouds to block out the summer sun, expect very hot temperatures with reading above 100F expected below 5,500 feet statewide. At least moisture will be lower today, making the heat a bit more bearable.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

San Juan Mountains, Southwest Slope, Southeast Mountains & Raton Ridge:

Sunny early then partly cloudy with widely scattered showers and storms developing by early afternoon. Max 30-min rain rates up to 0.8 inches with max 1-hour rain rates up to 1.2 inches are possible mainly for elevations above 8,000 feet right along the New Mexico border. A LOW flood threat has been posted for parts of the region for isolated flash flooding, debris slides and mud flows. In the lower elevations, gusty winds up to 40mph could accompany the stronger storms.

Primetime: 1PM to 9PM

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

Mostly sunny and very hot today with temperatures of 5-10F above normal, with readings above 100F likely across lower elevations. An isolated shower or storm cannot be ruled out along the Continental Divide over elevations above 9,000 feet. Max 30-min rainfall up to 0.3 inches is possible along with gusty winds, but flooding is NOT expected today.

Primetime: 1PM to 7PM