Issue Date: 5/17/2020
Issue Time: 7:45 AM

— Flooding is NOT expected today

A quick glance at the image below will be enough to find the major controlling factor of today’s forecast: the ridge of high pressure that is building over the mountain west. The axis of that ridge will shift slightly eastward today, centering itself over Colorado, and bringing warmer and drier conditions to the state. Over much of the High Country, the dry and warm conditions will be attended by gusty winds, leading to elevated fire danger. Red Flag Warnings have been issued, so please check with your local National Weather Service office for more information.

There remains a chance for a couple isolated thunderstorms over the Southeast Mountains and southern Front Range, eventually rumbling eastward over the adjacent Southeast Plains, southern Urban Corridor, Raton Ridge, and Palmer Ridge. Moisture is on the marginal side, so gusty winds and brief periods of light-to-moderate rainfall will be the main impacts. One or two may become strong-to-severe, producing hail up to 1 inch in diameter and strong winds.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. 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

Front Range, Southeast Mountains, Urban Corridor, Palmer Ridge, Northeast Plains, Southeast Plains, and Raton Ridge:

Mainly dry and warmer, with only a few isolated thunderstorms expected over the Southeast Mountains and southern Front Range, eventually rumbling eastward over adjacent areas. Any storm activity will begin between 1 and 3 PM, maximizing in coverage around 6-8 PM, and then diminishing quickly after that. A few light remnant showers will dissipate over the Southeast Plains early tomorrow morning. Rain rates will generally be less than 0.2 inches/hour, but stronger thunderstorms over the Southeast Plains may produce rainfall up to 0.5 inches/hour.

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

Warmer and drier, with gusty winds and elevated fire danger being the main concern. This will likely be the warmest day of the year so far for many locations. Red Flag Warnings have been issued for much of the area, so please check with your local National Weather Service office for more information.

Issue Date: 5/16/2020
Issue Time: 8:10 AM

— LOW Flood Threat is Forecast Today for the Spring Creek Fire Burn Scar

A disturbance aloft (red line in image below) will swing across Colorado today, with ridge of high pressure building in quickly behind it. At the surface, an exiting cool front will leave a bit of moisture in its wake across eastern Colorado, providing the fuel for showers/thunderstorms this afternoon and tonight along/east of the Continental Divide. The best coverage will occur south of I-70 and east of the Front Range and Southeast Mountains, with more isolated coverage to the north. West of the Continental Divide, the high-pressure ridge will usher in drier and warmer conditions, resulting in a pleasant afternoon for most.

Spring Creek Fire Burn: Scattered thunderstorms will rumble near the burn scar, with dewpoints in the 30s. This is enough moisture to produce rain rates in the 0.15-0.35 inches/hour range. There is a chance for outflow from nearby thunderstorms to push dewpoints higher, into the 40s, by this evening. This additional moisture would be enough to produce rain rates of 0.5 inches/hour, and thus the issuance of the low flood threat.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. 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

Front Range, Southeast Mountains, Urban Corridor, Palmer Ridge, Northeast Plains, Southeast Plains, and Raton Ridge:

Along and South of I-70: Scattered showers and thunderstorms expected, first developing over the higher terrain and Palmer Ridge, then spreading east-southeastward over the plains. A couple storms will push marginally severe limits, with hail up to 1 inch in diameter and strong winds up to 70 mph. Rain rates will generally be in 0.2-0.4 inches/hour range, with max rain rates of 0.5-0.75 inches/hour over the Southeast Plains. Timing: 1 PM – 11 PM, with one or two lingering storms over the Southeast Plains into the early morning hours.

North of I-70: Showers/thunderstorms will be more isolated than areas to the south, with the best chance for storms near the foothills and out over the Northeast Plains. Rain rates will generally be in the 0.1-0.3 inches/hour range, with max rates over the Northeast Plains around 0.6 inches/hour. Timing: Noon – 9 PM

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

Drier and warmer as the upper ridge of high pressure builds over the area. Most areas will see plenty of sunshine and high temperatures near, or just above, average for the date. A couple isolated showers/weak thunderstorms will rumble over the San Juan Mountains and adjacent San Luis Valley where better moisture will hang on and the disturbance aloft will be last to leave. Rain rates will be less than 0.2 inches/hour.

Timing: 1 PM – 10 PM

Issue Date: Friday, May 15th, 2020
Issue Time: 9:05AM MDT

— A LOW flood threat has been issued for the Northeast Plains, Palmer Ridge and Southeast Plains

An overnight cold front has helped hold moisture in place over the state. PW was again measured this morning at 0.60 inches and 0.48 inches for Denver and Grand Junction, respectively. The atmosphere will be better suited to produce some stronger storms this afternoon over eastern Colorado due to a boost in instability and area of convergence (red circle below). Storms will also be supported by upper level flow and a stronger shortwave moving through the west and southwest flow. All these features will combine to help produce some severe thunderstorms over the far northeast corner of the state. The main threats will be large hail and strong winds as the storms form an MCS along that line of convergence by early this evening.

Expecting storms to fire first over the northwest quadrant of the state just after noon. Best chance for accumulations will again be over the higher elevations of the Northwest Slope, Northern Mountains and Central Mountains along the Divide. To the east, development will favor the Front Range with more scattered storms over the Southeast Mountains and Raton Ridge early this afternoon. Although moisture will still not be too impressive, trailing and back-building storms will cause an increase in accumulation over some locations in an hour or two. Additionally, higher moisture east of the green line below is expected to increase storm totals. Thus, a Low flood threat has been issued with the flood threats being isolated arroyo and small stream flash flooding, field ponding and low-land flooding. A couple light showers may linger over the Southeast Plains overnight, but they should start to break up tomorrow morning. Other rainfall activity across the state should end by midnight.

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:

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

Storms the west will have less available moisture, so totals will be a bit less than out east. Max 1-hour rain rates up to 0.75 inches will be possible in the foothills and along the Urban Corridor with totals increasing to 1.20 inches along the Palmer Ridge. Out east near the border, max 1-hour rain rates up to 1.75 inches will be possible. Thus, a Low flood threat has been issued. Severe storms this afternoon could produce some strong gusts (greater than 50 mph) and large hail (up to 1.5 inches in diameter), but these threats should be only over the northeast corner of the state. Lingering overnight storms on the Southeast Plains could produce some high, isolated totals (around 2 inches) by morning.

Primetime: 12PM to 5AM

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

Should see an uptick in coverage of storms this afternoon and evening as the stronger shortwave moves through. Best chance for accumulation will be in the Northern Mountains and near/along the Roan Plateau and Flat Top region. Isolated totals just under 0.50 inches will be possible by morning in the Northern Mountains. Small hail is also possible for the strongest storms that form further north. Gusty winds will also be likely under most storms that do form, including the more scattered storms over the Grand Valley and western Central Mountains.

Primetime: 12PM to 10PM

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

These areas will stay dry this afternoon with highs in the mid to upper 70Fs. Surface winds will again be under critical fire weather criteria, so there is no Red Flag Warning. Lows overnight are forecast to drop into the 40Fs for the lower elevations and between 35-40F for the mountain valleys.

Issue Date: Thursday, May 14th, 2020
Issue Time: 8:30AM MDT

— Flooding is NOT expected today

Moisture has begun to return to the state behind a cold front that moved through overnight as evidenced by late night storms over the northern Urban Corridor. PW was measured at 0.60 inches and 0.48 inches for Denver and Grand Junction, respectively. That’s quite the increase from this time yesterday. With low-level moisture available and weak shortwaves moving through the WSW flow, afternoon and overnight storms will return to the forecast. There isn’t quite as much moisture over western Colorado, so the high-based storms will be restricted to the northern border and favor the Northern Mountains for accumulation.

East of the Continental Divide, upslope flow will start to develop storms over the Front Range and northern Southeast Mountains around noon. Expecting these storms to move into the adjacent plains with ESE storm motion. Best coverage should be over the Northeast Plains and Palmer Ridge, and as storms make it into better moisture over the plains, convection will likely increase in area. This could mean a couple rounds of storms over one location, which would help increase accumulations. With dew points still in the upper 40Fs, and relatively fast storm motion, flooding is not forecast. The central, eastern border counties may see some overnight thunderstorms and rainfall, but it should clear out by morning.

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:

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

While the southern Southeast Mountains and Raton Ridge will stay dry, all other regions should see some rainfall and thunderstorms this afternoon. A severe storm or two may be possible for the plains with the main threats being gusty outflow winds and hail around 1 inch in diameter. All storms will be high-based so outflow may produce brief gusts. Max 1-hour rain rates up to 0.50 inches (west) and 1 inch (east) will be possible. Reminder that the central, eastern border counties will likely see some overnight thunderstorms, but it should clear out by morning as the system moves into Kansas. Isolated storm totals by morning could reach up to 1.50 inches. There is no flood threat forecast.

Primetime: 12PM to 5AM

Northwest Slope & Northern Mountains:

A little better moisture in this area before the front stalled out moving south. Storms once again are expected be high-based and produce strong wind gusts in lieu of rainfall. The best chance for accumulation will be over the Northern Mountains where isolated totals up 0.20 inches will be possible by morning. A weak cold front moves through again overnight, which may cause another round of evening storms. Flooding is not forecast.

Primetime: 12PM to 11PM

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

These areas will remain dry today with afternoon temperatures in the low to upper 70Fs in the valleys and mid 50Fs to 60F over the mountains. Due to the jet pulling north into Wyoming, surface winds will decrease. This will eliminate Red Flag Warning conditions for the next couple of days.