Issue Date: Monday, August 23rd, 2021
Issue Time: 8:30AM MDT

— Flooding is NOT expected today

As shown in the water vapor image, below, relatively little change was observed in this morning’s atmospheric circulation compared to yesterday morning. The upper-level ridge to the southeast of Colorado has strengthened a bit, leading to a slightly stronger southwesterly flow over most of our state. Storm motions today will be 25mph or higher, which will limit point rainfall. A sprawled out, weak disturbance was noted over central Colorado, which will likely focus today’s rainfall a bit, especially on its moister northeast side. However, boundary layer moisture, a necessity for heavy rainfall, remains largely lacking. Although Grand Junction’s morning Precipitable Water (PW) has increased to a somewhat respectable 0.84 inches, the lower-levels are relatively dry. Furthermore, a strong warm “nose” of air remains in the upper levels and will be detrimental to building storm clouds, helping to limit rainfall. Additionally, much drier air resides just west of Colorado, so we expect steady or decreasing PW throughout the day especially along the UT border.

In all, with the slightly higher mid-level moisture, expect an increase in higher terrain storm coverage today into the scattered category. Highest coverage will be over the higher terrain, above 8,000 feet, but a few isolated storms will likely make it eastward into the Northeast Plains. Storms will produce light to possibly moderate rainfall over brief period, along with gusty winds. However, 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:

Northeast Plains, Southeast Plains, Palmer Ridge, San Luis Valley, Raton Ridge and Urban Corridor:

Seasonably hot today with isolated to widely scattered showers and weak storms this afternoon, mainly closer to the foothills. Max 1-hour rainfall up to 0.4 inches is possible with the strongest cells, along with gusty winds. Flooding is NOT expected today.

Primetime: 1PM through 9PM

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

Seasonably warm today with scattered showers and weak storms mainly over the higher terrain above 8,000 feet. Max 1-hour rainfall up to 0.5 inches is possible today, especially over northern areas towards the WY border. Flooding is NOT expected today. Gusty winds will also be possible with the stronger cells.

Primetime: 12PM through 9PM

Issue Date: Sunday, August 22nd, 2021
Issue Time: 8:50AM MDT

— Flooding is NOT expected today

Colorado is sandwiched between a departing trough to our north and a building High pressure center to our southeast, which will produce a pretty benign weather pattern statewide today. Southwest and westerly flow aloft will continue to hold a drier air mass in place as indicated by PW at Denver and Grand Junction measured at 0.64 and 0.74 inches, respectively. With most of the moisture in the mid-levels, more cloud cover than wetting rainfall is forecast today with this residual moisture. There will be a couple weak disturbances that move through the flow, which could spark some isolated showers near the southern border. The best chance for wetting rainfall will be over the Southeast Plains; however, with better moisture to our east, only minor accumulations are expected. The passing trough is also expected to produce some breezy conditions at the surface over the mountains and adjacent plains. Overall, looking a beautiful day ahead with warming temperatures. As imagined, flooding is NOT forecast.

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, San Luis Valley, Raton Ridge & Southeast Plains:

Weak and isolated showers will be possible across the southern border high terrains and adjacent plains later this afternoon and evening. However, more cloud cover than wetting rainfall is forecast. Best chance for accumulation will be over the Southeast Plains and eastern Raton Ridge, but totals should remain under 0.50 inches. If showers can develop over the southern mountains, only light rainfall is forecast. High temperatures bounce back up to the 90Fs over the lower elevations with 80Fs forecast over the mountain valleys. Breezy southwest surface winds in the 10-15 mph range should be anticipated.
Primetime: 12PM to 8PM

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

It should remain mostly dry today, although there’s a low chance for a sprinkle or two over the Palmer Ridge and mountains. High temperatures out east are forecast to reach 90F with 70’s and 80’s forecast west. Beautiful day ahead, but do expect westerly winds in the 15 to 20 mph range. The higher winds speeds are anticipated over the mountains.

Issue Date: Saturday, August 21st, 2021
Issue Time: 9:20AM MDT

— Flooding is NOT expected today

A cooler and less active weather pattern is forecast again today, although there is still some rainfall in the forecast. Overnight and early morning showers over the eastern plains (blue shades) will continue to break up and lift northward with the departing shortwave this morning. In the wake of these showers, cooler and more stable conditions are forecast across the plains, which will help to limit precipitation chances across the area. As for today, expecting southwest and westerly flow aloft to increase statewide as the next closed Low system digs southeast before moving east tomorrow. This flow will cause another couple of shortwaves to move across the state, which will help to generate storms over the Northwest Slope and across the Front Range, Central and Northern Mountains. The northeastward movement of the storms will likely cause some spillover into the Urban Corridor by mid-afternoon, which may produce some brief windy conditions along with light to moderate showers.

PW this morning was measured around 0.70 inches at Grand Junction and Denver. This should be plenty of moisture for scattered storms to develop, although a notable cap around 500mb will likely reduce the coverage of storms today. Quicker storm motions and higher storm bases should limit the flood threat, and anticipate the stronger storms that develop to produce some gusty outflow winds. Rainfall should end just after the sun sets; however, a second wave of overnight, light rainfall may be possible over the Northwest Slope. Flooding is NOT forecast 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, Grand Valley, Northwest Slope, Northern Mountains, Front Range, Palmer Ridge & Urban Corridor:

Best chance for storms and accumulating rainfall today will be over these regions with much of the rainfall falling over the mountain forecast regions. Max 1-hour rain rates over the mountains up to 0.50 inches (central/south) and 0.35 inches (north) will be possible. Storms over the Northwest Slope may produce accumulations up to 0.40 inches. Higher storm bases with limited low-level moisture may allow the stronger storms that develop to produce gusty outflow winds this afternoon/evening along with normal threat of lightning. Overnight showers are possible over the Northwest Slope and Northern Mountains, but accumulations should be light with more cloud cover than rainfall forecast. Flooding is NOT expected today.
Primetime: 11AM to 9PM

San Juan Mountains, Southwest Slope, Southeast Mountains, San Luis Valley, Raton Ridge, Northeast Plains & Southeast Plains:

It should be a bit drier over these regions today, although some isolated light showers are still possible over the mountains. Storm totals should remain under 0.10 inches, so flooding is NOT expected. High temperatures will be on the cooler side as well with low to mid 80Fs for the valleys and 70Fs for the mountains.

Issue Date: Friday, August 20th, 2021
Issue Time: 9:30AM MDT

— Flooding is NOT expected today
— A PM forecast update is possible today.

As shown in the visible satellite image, below, a strong trough is currently positioned right over Colorado allowing for the influx of much drier and cooler air into our state. The air is so much cooler that higher elevation locations as low as 10,000 feet received a bit of snow overnight! To the east, a surface low pressure was observed along the KS/NE border, along with an attendant cool front that was racing southward across eastern Colorado. Precipitable Water (PW) has fallen sharply for most areas with Denver’s morning reading at 0.67 inches, and Grand Junction’s at 0.60 inches. PW will continue to fall for all areas except the Southeast Plains where it will stay steady, up to 1 inch, or even increase slightly overnight as easterly low-level winds advect some moisture from KS back into CO.

Dry conditions are expected for most of the state today, along with pleasantly cool temperatures and breezy conditions at times. It will certainly feel a bit like fall! However, an interesting and unusual situation will setup during the late evening and overnight hours over the Southeast Plains and Raton Ridge. Lee-side cyclogenesis is expected over northern New Mexico later this afternoon as another disturbance, currently over CA/AZ, races eastward. This will shift low-level winds from northerly to easterly and allow for a 3-6 hour period of moisture return into Colorado. Depending on moisture availability, there could be enough instability to fuel isolated to scattered showers and storms over the Arkansas River basin. Short-term moderate to possibly heavy rainfall could result as these storms slowly move northward. At this time, flooding is NOT expected but due to the unusual timing of the expected heavy rain (i.e. overnight), an afternoon forecast update is possible today should a flood threat arise.

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, Palmer Ridge and Raton Ridge:

Cooler and breezy today, with dry conditions expected through early evening. Isolated to scattered showers and thunderstorms are possible beginning late evening and into the overnight hours. Max 1-hour rainfall up to 0.9 inches (Palmer Ridge and Raton Ridge) and up to 1.4 inches (Southeast Plains). This is just below flood threat thresholds, so flooding is NOT expected at the moment. However, an afternoon forecast update is possible if a threat arises.

Primetime: 11PM through 3AM

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

Cooler and breezy today with mainly dry conditions. Isolated rain and high-elevation snow showers are possible mainly this morning over the Northern Mountains and Central Mountains. Accumulations will be very light. Overnight, an isolate shower or weak storm cannot be ruled out over the Northeast Plains. Max 1-hour rainfall up to 0.6 inches. Flooding is NOT expected today.

Primetime: 2AM through 5AM