Issue Date: Friday, May 19th, 2017
Issue Time: 8:45AM MDT

— Flooding is NOT expected today

The impressive late season snowstorm that affected our entire state on Thursday will weaken and continue to trek eastward today. The water vapor image below shows that it is positioned across eastern Colorado as of this morning; by this evening, it will move into western Kansas. Most of eastern Colorado will continue to be under its influence today with numerous showers and perhaps a weak thunderstorm likely. However, with little to no instability and weaker dynamics, precipitation intensities will be lower than yesterday. Nonetheless, a few places along the Kansas and Nebraska borders may pick up over 1 inch of rainfall but distributed over many hours. Thus, we do not expect a flash flooding threat today.

Yesterday’s large precipitation totals have caused many creeks, streams and even larger rivers such as the South Platte and Arkansas to swell. Fortunately, this morning’s analysis indicates that all river crests over the next 24-48 hours are expected to stay below the Minor flood stage level. Thus, we do not expect substantial riverine flooding though low lying and poorly drained areas in the Front Range may continue to have standing water for the next day or two.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below (hover over threat areas for more details). For Zone-Specific forecasts, scroll below the map.

Zone-Specific Forecasts:

Northeast Plains, Southeast Plains, Palmer Ridge:

Overcast skies with numerous showers and perhaps a weak thunderstorm continuing throughout the day. Max 1-hour rainfall up to 0.8 inches (especially far east areas). Max 24-hour rainfall up to 1.3 inches. The strongest storms in the far southeast part of the state could produce hail up to 0.75 inches. The South Platte and Arkansas rivers will remain elevated from yesterday’s precipitation and today’s additional activity. However, all river crests are expected to remain below Minor flood stage. Flash flooding is also not expected today.

Primetime: 11AM to 9PM

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

Mostly cloudy early then a few breaks in the clouds by late afternoon, with continued much below normal temperatures. Max 1-hour rainfall up to 0.4 inches possible with max 24-hour rainfall up to 0.7 inches. Flooding is not expected today.

Primetime: 11AM to 5PM

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

Mostly cloudy early then gradual clearing the afternoon, with warmer temperatures compared to yesterday. Isolated to scattered showers (higher elevation snow; snow level 8,000 feet rising to 10,000 feet by late afternoon) are possible especially in the morning through early afternoon. Max 1-hour rainfall up to 0.25 inches. Flooding is not expected today.

Primetime: 11AM to 3PM

Issue Date: Thursday, May 18th, 2017
Issue Time: 9:00AM MDT

— Flooding is NOT expected today

A strong low-pressure system, as easily seen on water vapor imagery (below), is quickly traversing across Colorado from west to east today. The combination of strong dynamics, an easterly moisture feed, and orographic lifting is causing widespread precipitation this morning. Yes, impressively, some of the precipitation is falling as snow even in the lower elevations. Fortunately, due to the cold nature of this system, atmospheric instability will remain near zero except for the far southeastern portion of the state. Thus, only light to moderate precipitation intensity is expected today. Flooding is not expected though poorly drained areas may see some nuisance ponding due to the long duration of the event. Even in the southeast, any storm that manages to form will move quickly to the east/northeast, limiting the rainfall in any given location.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below (hover over threat areas for more details). For Zone-Specific forecasts, scroll below the map.

Issue Date: 5/17/2017
Issue Time: 9:45 AM

A LOW FLOOD THREAT IS FORECAST FOR PORTIONS OF THE FRONT RANGE, URBAN CORRIDOR AND NORTHEAST PLAINS. The Purgatoire River continues to run at bank-full levels, to minor flood stage, in Bent County.

A shortwave ridge between yesterday’s upper-level low and the upcoming upper-level low will provide a break in the active weather today east of the Continental Divide, but only for a brief while. Showers and thunderstorms will be on the increase for the Front Range, Urban Corridor, Northeast Plains, Palmer Ridge, and northern portions of the Southern Plains during the early afternoon. Later during the afternoon/evening hours as instability and lapse rates becomes more favorable, a few scattered thunderstorms will join the showers. These thunderstorms will continue into the overnight hours, and are the reason behind the issuance of the low flood threat. Cold air will continue to filter into the region overnight, which will drop snow levels to 7,000 feet in the mountains and foothills.

Further to the south over the Southeast Plains, Southeast Mountains, and Raton Ridge, it will be late in the evening, perhaps midnight or later, before any showers pop up. Any thunderstorms that develop in these regions will be less intense, and do not warrant any flood threat considerations. Snow levels in the mountains will be around 7-8,000 feet.

West of the Divide, showers have already began to increase due to the newest influx of moisture and atmospheric support. A few isolated thunderstorms will develop this afternoon/evening as daytime heating results in a bit of instability, but flooding rain is not expected. Snow levels during the day will be around 8-9,000 feet, dropping to around 6000 feet overnight tonight. For more information regarding timing and rain rates, please see the zone-specific forecasts below.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below (hover over threat areas for more details). For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

Front Range:

Scattered-to-widespread showers and an isolated thunderstorm or two are expected today/tonight, beginning just after lunchtime and continuing into the overnight hours. Snow levels will be around 9000 feet during the day, falling to around 7,000 feet overnight. Maximum rain rates from thunderstorms will be 0.8-1.2 inches/hour.

Timing: 1 PM – Midnight, with a few lingering showers into the morning hours tomorrow.

Urban Corridor, Palmer Ridge, and Northeast Plains:

Scattered showers and thunderstorms are expected to develop early this afternoon, continuing into the overnight hours. Maximum rain rates will be as follows:

Urban Corridor and Palmer Ridge: 0.8-1.2 inches/hour
Northeast Plains: 1.5-2.0 inches/hour

Timing: 1 PM – 1 AM, with a few lingering showers/thunderstorms into the morning hours tomorrow

Southeast Plains and Raton Ridge:

The upper-level ridge will hold off showers in these regions through the early afternoon, before giving way to a few showers for the rest of the period across the Southeast Plains. The Raton Ridge will remain largely dry into the morning tomorrow. Maximum rain rates will be 0.4-0.8 inches/hour for the Southeast Plains and 0.1-0.3 inches/hour for the Raton Ridge.

Timing: 4 PM – Midnight, with a few lingering showers into the early morning hours

Southeast Mountains:

The region will remain dry into the evening hours tonight, with activity perhaps holding off until midnight or later. Showers that develop will be scattered in nature, producing mainly light rain/snow. Maximum rain rates: 0.4-0.6 inches/hour

Timing: Midnight – End of Period

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

Scattered to widespread showers and a couple isolated thunderstorms are expected throughout the period. Snow levels will be around 7-8000 feet during the afternoon/evening, before falling to around 6000 feet overnight tonight. Maximum rain rates are as follows: 0.3-0.6 inches/hour

Timing: Ongoing – End of Period

Issue Date: 5/16/2017
Issue Time: 9:25 AM

A LOW FLOOD THREAT IS FORECAST TODAY FOR PORTIONS OF THE NORTHEAST PLAINS AND SOUTHEAST PLAINS. The Purgatoire River continues to run at bank-full levels, to minor flood stage, in Bent County.

An upper-level trough will rotate across the region today, resulting in an unsettled day/night. The potential for heavy rainfall will be stunted by limited moisture across the high country and western slope; this morning’s precipitable water values were in the 25th percentile for the date. Those values will climb somewhat with the approach/passage of the upper-trough, but not to an extent to warrant a flood threat. For the adjacent lower elevations of the Urban Corridor, Palmer Ridge, Raton Ridge, and western portions of the plains regions, a bit better moisture will be present. Storms that form in these areas will have access to enough moisture to produce brief periods of moderate-to-heavy rainfall, but not enough to warrant a flood threat.

The deepest moisture (and best instability) will reside across the far eastern plains, which is where a low flood threat has been issued for today/tonight. Additionally, near/within the low flood threat, storms will be on the strong-to-severe side, with damaging winds and large hail as the main threats. An isolated tornado or two cannot be ruled out, especially across far northeastern Colorado where a surface boundary will reside. For more information regarding rain rates and timing, please see the zone-specific forecast discussions below.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below (hover over threat areas for more details). For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

Urban Corridor, Palmer Ridge, Northeast Plains, Southeast Plains, and Raton Ridge:

Sunny skies this morning will give way to mostly cloudy skies and scattered showers/thunderstorms this afternoon/tonight. Areas nearest the mountains will see storms produce more in the way of gusty outflow winds than rainfall due to drier air in the low- and mid-levels. Further to the east, deeper moisture is present, with dewpoints in the 40s and low 50s. These areas will hold the threat for heavy rainfall, and thus the introduction of the low flood threat. Maximum rain rates are as follows:

Urban Corridor and Palmer Ridge: 0.4-0.8 inches/hour
Northeast Plains and Southeast Plains (Kiowa/Cheyenne Counties): 1.0-1.75 inches/hour
Southeast Plains (remainder): 0.4-0.8 inches/hour
Raton Ridge: 0.1-0.3 inches/hour

Timing: 1 PM – 1 AM, with lingering showers into the morning hours

Front Range and Southeast Mountains:

Increasing clouds are expected through the day as the upper-level trough rotates through. Isolated-to-scattered showers/thunderstorms are expected to develop this afternoon across these regions, with the best coverage/duration over the Front Range. Maximum rain rates are as follows:

Front Range: 0.2-0.5 inches/hour
Southeast Mountains: 0.2-0.4 inches/hour

Timing: 1 PM – 11 PM, with a few lingering showers into the early morning hours, mainly over the Front Range

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

High clouds have already begun streaming into the area, with more on the way. Scattered showers/thunderstorms are expected this afternoon and evening, with the most coverage expected over the higher terrain. Snow will fall on the mountain peaks, resulting in 1-3 inches of accumulation. Moisture is limited, so heavy rainfall is not a threat today. Maximum rain rates will be 0.2-0.4 inches/hour.

Timing: 11 AM – 9 PM, with a couple lingering showers until midnight.