Issue Date: Monday, May 31st, 2021
Issue Time: 9:30AM MDT

— Flooding is NOT expected today

Unsettled and cool weather will continue for most this Memorial Day. Currently, there is ample cloud cover over eastern Colorado and the mountains along with fog, rain showers and snow at the highest elevations. It’s sunny over the western half of Colorado, especially north where dry northwesterly flow has started to decrease the available moisture in the mid and upper levels of the atmosphere. This split flow pattern, the intrusion of dry air and general subsidence behind yesterday’s trough is forecast to continue throughout the day over the northern portion of the state. This will drop off the chances for rainfall north of I-70, although some weak showers maybe possible over the mountains (near the Continental Divide) with residual moisture.

Further south, the trough to the southwest, will continue to help re-enforce the moisture across south, central Colorado seen above (blue/white shades). As the upslope flow kicks in this afternoon with mid-level energy moving through across the state, widespread storms are forecast to develop across the Central, Southeast East, San Juan and southern Front Range Mountains (snow above ~11K feet). With cooler temperatures east, more stratiform rainfall with embedded, moderate convection is likely. Some spill over into the adjacent, eastern plains and ridges is possible late this afternoon/evening with the southeast moving storms. Over the western high terrains (south), rainfall totals should slightly increase from yesterday due to a slight increase in PW (0.56 inches at Grand Junction) and more moist boundary layer. Stronger storms that develop this afternoon will likely produce lightning, wind gusts and moderate rainfall with slow steering flow. With the southeast movement of storms, the San Luis Valley should also record measurable rainfall for the second day in a row. Rain rates are gradual enough today, thanks to limited instability, that 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:

Southeast Plains, Raton Ridge, Palmer Ridge, & Southeast Mountains:

Gradual rainfall due to cooler temperatures should accompany the numerous storms that develop over the mountains this afternoon. Max 1-hour rain rates up to 0.60 inches over the mountains with isolated 24-hour totals up to 1 inch are possible. Rain should start to cross over to snow again at the higher elevations by this evening ending the flood threat for the higher elevation burn areas. Southeast movement of storms will spill rainfall into the adjacent plains and ridges late this afternoon. Max 1-hour rain rates up to 0.25 inches will be possible. Flooding is NOT forecast today.

A Flash Flood Watch has been re-issued by NWS Pueblo for the burn areas over the Southeast Mountains. Head on over to the FBF for our burn area forecast for today.

Primetime: 1PM to 10PM

Central Mountains, San Juan Mountains, Southwest Slope & San Luis Valley:

Numerous storms will develop over the high terrains this afternoon with decent moisture, mid-level lift and upslope flow. I’m sure everyone is looking forward to the widespread, measurable rainfall for the mountains. A couple stronger storms may be possible south (initially) with the main threats being outflow winds, lightning and small hail. Moderate rainfall with 1-hour rain rates up to 0.60 inches will be possible. Isolated totals over the eastern San Juan Mountains could reach around 0.75 inches by late this evening. As storms move southeast with the steering flow, showers will likely spill into the San Luis Valley. Totals up to 0.75 inches will be possible by morning around the southern tier of the valley. Flooding is NOT forecast.

Primetime: 11AM to 10PM

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

Dry air and subsidence will limit the chances for rainfall this afternoon over these regions. A couple showers will likely still develop over the mountains with the residual moisture, but 1 hour rain rates should remain around 0.15 inches. Cloudy conditions will persist over the Urban Corridor this morning along with weak showers as well with temperatures remaining below average this afternoon. Over the northwest corner of the state, sunny skies with temperatures slightly above normal are forecast.

Issue Date: Sunday, May 30th, 2021
Issue Time: 10:35AM MDT

— A MODERATE flood threat has been issued for portions of the Palmer Ridge, Southeast Mountains, western Southeast Plains and Raton Ridge

— A LOW flood threat has been issued for portions of the Northeast Plains, southern Urban Corridor and eastern Southeast Plains

A few showers over the Northern Mountains and Front Range to start the day with some thunder over the eastern plains. Today, the atmosphere will remain very moist over eastern Colorado, which is shown by the nearly saturated atmosphere in this morning’s sounding. PW was measured at 0.83 inches, which is well above normal for this time of year. One limiting factor for heavy rainfall over eastern Colorado will be lack of instability due to cooler temperatures and ongoing cloud cover (see visible satellite imagery below). This should somewhat help to temper the rain rates within the storms that develop on the north side of the front (southern Palmer Ridge). On the flip side, slow westward moving storms, a second round of widespread rainfall this afternoon/evening associated with the incoming trough (orange line below) and nearly continuous upslope flow will help increase rainfall accumulation for this area. This is especially true over the eastern plains where even higher moisture resides, so a Low flood threat has been issued for this area.

Stronger storms are forecast to develop along and south of the frontal boundary where better instability will be able to build. The highest rain rates should be over these regions and a couple severe storms are possible over the Raton Ridge, Southeast Plains and southern Palmer Ridge. Paired with slow storm motion, a Moderate flood threat has been issued. Threats include road, low-lying area and local stream flooding.

It’s a bit drier back to the west, especially over the southwest corner. PW at Grand Junction was measured at 0.48 inches, and a dry surface layer with a large dew point depression means storms that develop this afternoon will be less efficient at rainfall accumulation. Best chance for rainfall will be over the Central and Northern Mountains and over the lower elevations along and north of I-70.

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.

A NWS Flood Warning is ongoing for the Purgatoire River at Las Animas through Sunday evening. As of 8AM the river was at 9.83 feet, which is in the Minor flood stage. Flood threats include minor agriculture flooding of low-lying areas near the river. Update: As of 10:30AM this morning, the river was at 13.81 feet, which is now in the Moderate flood stage. Flood threats continue to remain the same but are slightly elevated.

Zone-Specific Forecasts:

Southeast Plains, Raton Ridge & Palmer Ridge:

There’s a chance for a couple severe storms over these regions this afternoon (south) if some instability is able to build before the storms move slowly off the mountains. Severe storms that develop south, may produce 1.50 inch hail and brief windy conditions. As the storms move into a higher moisture environment at the lower elevations, max 1-hour rain rates up to 2 inches will be possible with widespread rainfall forecast. Thus, a Moderate flood threat has been issued for road, low-lying area and local stream flooding.

Primetime: 1PM to Midnight

Front Range, Urban Corridor, Northeast Plains & Southeast Mountains:

Limited instability further north should limit rainfall rates, although after this morning’s rainfall and another round this afternoon could push accumulations over the Front Range close to 1.25 inches by morning. Over the Southeast Mountains, general rainfall totals should be closer to 0.75 inches with light showers linger into the night. With slightly higher moisture over the eastern plains and nearly stationary storms, totals are expected to be larger over the 24-hour period. With isolated 24-hour totals up to 3.25 inches possible over plains, the Low flood threat has been extended out east. Flooding of roads, ditches, fields and low-lying areas is possible.

A Flash Flood Watch has been issued by NWS Pueblo for the burn areas over the Southeast Mountains. Please check our FBF for burn areas today as there has been elevated threats issued for some burn areas within these regions.

Primetime: Ongoing to 2AM 

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

Best chance for a couple thunderstorms and accumulating showers will be over the Central and Northern Mountains. Some scattered storms forecast for the elevated plateaus late this afternoon and evening along and north of I-70. Max 1-hour rain rates up to 0.25 inches will be possible with isolated storm totals up to 0.50 inches possible on southwest facing slopes. Flooding is NOT forecast.

Primetime: 2PM to 11PM

Issue Date: Saturday, May 29th, 2021
Issue Time: 10:00AM MDT

— A MODERATE flood threat has been issued for parts of the Northeast Plains and Southeast Plains
— A LOW flood threat has been issued for parts of the Urban Corridor and Palmer Ridge
— The threat will persist later that normal, into the late evening and overnight hours (especially further east)
— A MODERATE flood threat has been issued for the Calwood and Cameron Peak burn scars (see Fire Burn Forecast page for more info)

As expected, a complex weather pattern is beginning to take shape over Colorado, in response to two forcing features as shown in the visible image below. The first feature is a trough in the northern jet stream, currently entering western Wyoming. This will provide synoptic-scale lift mainly east of the Continental Divide beginning later this afternoon. To the south, a cut-off disturbance entering the southwest US coast will mainly affect Colorado beginning tomorrow, but will help anchor a developing surface low pressure over the CO/NM border today. PW this morning at Denver and Grand Junction was 0.48 and 0.41 inches, respectively. While this is certainly far from impressive, the developing surface low pressure will support a notable feed of low-level moisture from the southern Great Plains into eastern Colorado later today. PW is expected to jump to the 0.7-1.1 inch range east of the Continental Divide, which will be supportive of heavy rainfall.

The visible satellite image also shows that parts of eastern Colorado are currently seeing a thick low-cloud deck along with patchy dense fog. The rate at which this dissipates will be essential to determining where the strongest instability will develop. Currently it appears that the far northeast portion of the state will stay within this cool stable air for most of the day, limiting chances for heavy rainfall.

In summary, we expect late morning and afternoon shower and thunderstorms to form off the higher terrain and quickly grow in coverage and rain intensity. A Low flood threat has been posted for parts of the Urban Corridor and Palmer ridge for the risk of isolated flash flooding. Nuisance street and field flooding will also accompany this threat. Severe weather, notably large hail but also isolated tornadoes will also be possible, especially with the afternoon activity. Further east, a couple of areas of Moderate threat have been posted in anticipation of the late afternoon and evening surge of moisture into the area. Also note that the threat will persist later than normal today, well into the evening and overnight hours.

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:

Scattered showers and thunderstorms later this morning becoming more widespread through the afternoon, evening and overnight hours. Max 1-hour rain rates up to 2.3 inches, with max 3-hour rainfall up to 3.7 inches warrant a Low/Moderate flood threat for the risk of isolated flash flooding. Street and field flooding will also be likely with the heaviest rainfall. The threat will continue well into the overnight hours.

Primetime: 1PM through 4AM

Palmer Ridge, Raton Ridge, Urban Corridor, Front Range:

Scattered showers and thunderstorms later this morning becoming more widespread through the afternoon, evening and early overnight hours. Max 1-hour rain rates up to 1.1 inches, with max 3-hour rainfall up to 2.0 inches warrant a Low flood threat for the risk of isolated flash flooding, debris slides and mud flows. Street and field flooding will also be likely with the heaviest rainfall. The threat will continue well into the overnight hours.

Primetime: 1PM through 12AM

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

Partly cloudy and cooler with isolated to scattered showers and a weak thunderstorm possible especially for northern areas. Flooding is NOT expected today.

Primetime: 12PM through 6PM

Issue Date: Friday, May 28th, 2021
Issue Time: 8:00AM MDT

— Flooding is NOT expected today

With a transient ridge overhead, central and western Colorado awoke to mostly sunny skies. Farther east, with a moist boundary layer, efficient radiational cooling led to a few pockets of fog and low clouds in the Arkansas and South Platte river valleys (see visible satellite image below). With the strong May sunshine and subsidence overhead, this will quickly dissipate leading to a seasonable warm, mostly sunny day for almost everyone. Denver PW this morning was at 0.38 inches, while Grand Junction was at 0.31 inches, both below seasonal normal. However, with Colorado’s impressive topographic-driven summer circulation, there will still be enough moisture present to produce isolated to widely scattered showers and thunderstorms today mainly over the Palmer and Raton ridges. Maximum rainfall intensity will stay below flood threat thresholds. However, a stronger storm capable of marginally large hail could occur right along the New Mexico border east of I-25. 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:

Palmer Ridge, Raton Ridge, Northeast Plains, Southeast Plains

Isolated to widely scattered showers and thunderstorms this afternoon, otherwise partly cloudy and warmer. Max 1-hour rainfall up to 0.4 inches over the Palmer Ridge and 0.8 inches over the Raton Ridge right along the NM border. Hail up to 1 inch is also possible along the NM border. Flooding is NOT expected today.

Primetime: 2PM through 9PM

Front Range, Urban Corridor, Southeast Mountains:

Becoming partly cloudy and warmer with an isolated shower or weak storm possible this afternoon. Max 1-hour rainfall up to 0.2 inches. Flooding is NOT expected today.

Primetime: 1PM through 7PM

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

Mostly sunny and warmer temperatures today with highs in the mid 80s F in the lower elevations and in the 50s F for the highest terrain. Flooding is NOT expected today.