FTB 06-15-2021: Intense June Heat Mixed with Smoke

Issue Date: Tuesday, June 15th, 2021
Issue Time: 8:55AM MDT

— Flooding is NOT expected today

It’s going to be a scorcher this afternoon under the anomalously strong June ridge. The High has moved into the four corners region and is helping to advect smoke into the state. The smoke this morning is pretty thick across the western border, which can be seen by the gray/brown hue below. It remains incredible dry over the majority of the state (clear skies below), and PW at Denver has dropped to 0.56 inches. The lack of moisture will help to keep precipitation chances and totals very low today. Water vapor imagery indicates some mild moisture trapped under the ridge across the southern border. So, as the diurnal flow develops, a couple high based storms are possible across the southern mountains. Perhaps even an isolated, high-based storm or two over the Palmer/Raton Ridges near the mountains. More wind than rainfall is forecast from storms that do develop today, so flooding is NOT expected.

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 Mountains, Front Range, Palmer Ridge & Raton Ridge:

Best chance for measurable rainfall this afternoon will be over the Southeast Mountains and Raton Ridge. A high-based storm or two may also pop over the southern Front Range and Palmer Ridge. Storms should track more south today with the location of the High. Brief, max 1-hour rain rates up to 0.40 inches will be possible across the ridges, while max rain rates will drop to 0.15 inches per hour over the mountains. Outflow winds will be the main threat from the storms that do develop, so flooding is NOT forecast.

Primetime: 2PM to 10PM

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

The excessive heat warning continues through Friday. Highs will reach 100F+ again for the Grand Valley and portions of the Southwest and Northwest Slope. Plenty of daily temperature records will be broken this afternoon, so be sure to take breaks from the heat and carry water with you. Afternoon cumulus will likely pop over the San Juan Mountains and may produce some very light rainfall/sprinkles (east). Smoke will continue to cause hazy conditions and poor air quality. This feels more like an August forecast than mid-June forecast. Flooding is NOT forecast.

Urban Corridor, San Luis Valley, Northeast Plains & Southeast Plains:

It’s going to be hot this afternoon, so be sure to take lots of breaks if you’re outside. Afternoon high temperatures will be in the upper 90Fs and likely reach 100F across a few areas. That means many daily temperature records have the potential to be broken. Rainfall is not forecast.

FTB 06-14-2021: The Anticipated Extreme Heat Wave Begins

Issue Date: Monday, June 14th, 2021
Issue Time: 10:00AM MDT

— Flooding is NOT expected today

Today marks the first day of a very hot temperature streak. While temperatures already reached 100F across the lower elevations of western Colorado yesterday, the building 594mb ridge today will raise afternoon high temperatures statewide. The wake of last night storms over the Nebraska panhandle are currently located eastern Nebraska (orange “X”). There’s some residual low level moisture from the feature near Colorado’s eastern border. Elsewhere, the dry air mass continues to dominate as shown by Grand Junctions morning sounding where PW was measured at 0.26 inches. That will translate to another dry day for the majority of Colorado (areas of orange below).

Looking back to the eastern adjacent plains where there is some residual moisture under the ridge, PW at Denver remains about the same as yesterday (0.70 inches). Similar to yesterday, this moisture gradient increases quite a bit as you move towards the eastern border. However, it looks like the dry westerly flow aloft will have a better chance of mixing out the surface moisture throughout the day when compared to yesterday, especially along the I-25 corridor. Outside of a couple weak showers over the elevated ridges, rainfall is not forecast for the immediate adjacent plains. There’s no identifiable shortwave moving through the flow, so that should help to keep the eastern plains capped as the storms and outflow boundaries move into the area late this afternoon and evening. There’s also a chance for a couple late night storms to cross over the northern border from Nebraska, but with lower instability, flooding is not expected.

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:

Temperatures will reach into the upper 90Fs and may reach 100F over portions of these regions this afternoon. A cap will likely inhibit any convection over the area as storms and outflow boundaries move into the area this afternoon and evening. Low confidence storms will break the cap, but if they do, max 1-hour rain rates up to 1.75 inches will be possible along with severe thunderstorms (hail and damaging outflow winds). Again, chances of this occurring are low enough that no flood threat will be issued. Late night storms may cross the northern border, and if they can survive, rain rates up to 1.5 inches per hour will be possible along with damaging outflow winds and some hail. Flooding is NOT forecast.

Primetime (if storms break the cap): 5:30PM to 2AM

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

Temperatures this afternoon will reach into the upper 90Fs across the Urban Corridor with upper-80Fs/low 90Fs forecast for the mountain valleys. Rising heights and decreasing surface moisture throughout the day mean storm develop chances will be low. A couple isolated storms could form over the elevated ridges where the surface flow has a bit more of an easterly component to it. Isolated max 1-hour rain rates up to 0.40 inches will be possible with wind as the main threat. Flooding is NOT forecast.

Primetime: 3PM to 8PM

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

An excessive heat warning has been issued again for dangerously hot conditions across the lower elevations out west. Highs will reach past 100F again for the Grand Valley. The century mark will also not be out of reach for the lower elevations of the Southwest and Northwest Slopes. San Luis Valley will reach into the 90Fs. Rainfall is not forecast.

FTB 06-13-2021: Overnight Flood Threat Issued for the Northeast Plains

Issue Date: Sunday, June 13th, 2021
Issue Time: 9:50AM MDT

— A LOW flood threat has been issued for portions of the Urban Corridor, Northeast Plains and northern Southeast Plains. This flood threat is an overnight threat.

A decent plume of moisture has worked its way under the ridge thanks to clockwise rotation around a surface High located in Missouri/Iowa. This plume is outlined in the green below, and the high surface moisture is helping to produce fog and cloud cover over the northeast corner of Colorado this morning. Out over the west border, it’s quite the opposite story. It remains incredibly dry (no rainfall forecast), and excessive heat becomes an issue this afternoon with highs forecast to reach over 100F for the Grand Valley.

Over eastern Colorado, PW at Denver has nearly doubled from yesterday morning to 0.68 inches. Equally important is that as you move towards the eastern border and closer to the plume, PW increases to an inch or above. So, it is very humid this morning with dew points at or above 60F. South/southeast flow at the surface around the aforementioned High and from the diurnal flow pattern should help to keep the moisture somewhat intact throughout the day despite the dry westerly/southwesterly flow aloft continuing.

A couple storms are expected to fire over the eastern elevated ridges this afternoon, which will drift southeast towards the High to our south. Then, a separate set of storms is expected to develop to our north late this afternoon and evening along a convergence boundary (cool front). These PM storms to our north are likely to spread in coverage and intensity as they move south/southeast into the higher moisture and the left exit region of the low level jet (increased lift). As the cluster of storms cross over the border tonight, widespread convection in a high moisture environment could cause flooding issues, if instability can hold on. Thus, a Low flood threat has been issued overnight. In addition to heavy rainfall, the more severe storms could produce large hail and damaging outflow winds tonight.

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 & Urban Corridor:

Heavy rainfall may be possible this evening and overnight for these regions. Back to the west over the northern Urban Corridor, the first set of storms that develop over the Cheyenne Ridge are expected to drift across the border by early this evening. With elevated moisture in the area, instability still present, slow steering flow and southeast/east flow increasing, training storms may produce storm totals just over 1 inch.

Later tonight, a second set of storms are expected to cross the northern border further east. While some of the morning model runs have been backing off the convection (rapidly decreasing instability overnight), if instability can hang on, numerous outflow boundaries will likely trigger additional convection over the Northeast Plains. With elevated surface dew points present, heavy rainfall becomes a concern alongside large hail and damaging outflow winds under the more severe storms. Isolated storm totals up to 2.75 inches will be possible, so a Low flood threat has been issued. Flood threats would include road flooding, field ponding and local stream flash flooding. Should the flood threat drastically drop off in probability later this afternoon, a PM update will be issued.

Primetime: 8PM to 4AM

Southeast Mountains, Front Range, Palmer Ridge & Raton Ridge:

It’s a bit too dry for storm develop over the mountains this afternoon, though some cumulus fields may still be possible. Better chance for storm development exists today over the elevated ridges, especially the Palmer Ridge where surface moisture remains higher. Max 1-hour rain rates up to 1 inch may be possible if the moisture does not mix out. Stronger storms will also be capable of producing small hail and strong outflow winds. Flooding is NOT expected today.

Primetime: 1PM to 8PM

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

An excessive heat warning has been issued for the Grand Valley where afternoon highs are forecast to exceed 100F. Equally hot temperatures are possible for the lower elevations of the Southwest and Northwest Slopes. Hazy and smokey conditions will continue from fires near the area. It’s going to be too dry for any rainfall with PW near a record low value at 0.19 inches.

FTB 06-12-2021: Rising Temperatures & Isolated Storms South

Issue Date: Saturday, June 12th, 2021
Issue Time: 8:45AM MDT

— Flooding is NOT expected today

The building High pressure (south) means that temperatures will be on the rise today. With the increasing heights and the same dry air mass as yesterday in place, the majority of the state will be rain-free again this afternoon and evening. Best chance for an isolated storm or two will be over the Raton Ridge and far southeast corner of the state. Higher surface dew points exist behind yesterday’s front in the area outlined in green below. A surface High over Nebraska and South Dakota will help reinforce southwesterly flow across this region, which should pull some of this surface moisture back across the border. The initial threat from the stronger storms that develop will be hail and brief heavy rainfall, but the dry mid-levels will likely change this threat to wind fairly quickly. The dry air aloft will also help to limit rainfall rates in the small storm cores. Thus, there is no flood threat issued.

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:

A couple isolated storms may develop over the Raton Ridge this afternoon. As they drift east/southeast around the High, they will likely strengthen as they move into an area of higher dew points. Dry mid-levels will likely limit rainfall rates despite some higher dew points in the area. Max 1-hour rain rates up to 0.75 inches may be possible. The main threat from the storms will be hail and strong outflow winds. Flooding is NOT forecast.

Primetime: 2:30PM to 11PM

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

Dry day ahead and warming up this afternoon. Highs are forecast to reach into the upper 80Fs and low 90Fs over the I-25 Corridor and eastern plains. With increasing heights and low moisture availability (PW at 0.38 inches in Denver), rainfall is not forecast. Outside of scattered cumulus this afternoon over the mountains and ridges, expect clear conditions.

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

Temperatures will be on the upswing this afternoon with scattered cumulus clouds forecast to develop over the mountains (south). Highs could reach the mid 90Fs over the lower elevations with mid to upper 80Fs for the mountain valleys. Smoke will likely continue to limit visibility and affect air quality, although the near surface smoke looks to mix out by early afternoon. Rainfall is not forecast today.