Issue Date: Saturday, May 27th, 2017
Issue Time: 9:55AM MDT

— LOW flood threat for Southeast Plains

The main disturbance, responsible for the last two days’ worth of severe weather, will be traversing across Colorado today as seen in the water vapor image below. Upward motion will be favored to the east of the trough axis (tan dashed line) and some support will also be available from a weak jet streak moving out of Colorado this afternoon. Thus, scattered to numerous showers are likely to develop this afternoon, especially east of the Continental Divide. A lee-side surface low pressure trough will once again form today, this time along the NM/CO border. This will act to direct moisture northwest into the Southeast Plains and Raton Ridge area. Storm motions in that region will be on the slower side, in the 25-30 mph range, which is conducive for locally heavy rain. The main factor acting against the chances of heavy rainfall will be limited instability, except for the southeast portion of our state. There, up to 1,000 J/kg of CAPE will be briefly available for convective development, with surface dew point temperatures in the low 50s feeding thunderstorm inflows. All in all, expect isolated to scattered thunderstorms in southeast Colorado today with at least isolated heavy rainfall being a good probability. Thus, a Low flood threat is warranted for that area.

In addition to the precipitation, hail up to 1.5 inches, gusty winds up to 55mph and a weak tornado could accompany the stronger cells.

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: Friday, May 26th, 2017
Issue Time: 10:30AM MDT

— MODERATE flood threat for Urban Corridor, Palmer Ridge and Northeast Plains
— LOW flood threat for Southeast Plains

As shown in the water vapor image, below, a strong disturbance was located over the northern Great Basin this morning. As the moves east-southeast today, it will aid the in the formation of a surface low in the lee side of the Colorado Rockies. Impressive pressure drops up to 8-12 millibars are expected by late afternoon. This surface circulation will advect higher moisture values into eastern Colorado and generate instability exceeding 1,000 J/kg. With upper-level forcing from the incoming disturbance and a jet streak located to the north, expect at least one round of showers and thunderstorms to develop east of the Continental Divide. Closer to the mountains, limited instability will keep rainfall rates below flood threat levels. Farther east, heavier rainfall will be possible and a Moderate flood threat has been posted for parts of east-central Colorado. A Low flood threat is posted for areas bordering the Moderate threat area for more isolated heavy rainfall chances. Isolated flash flooding is the main impact today, with field/road flooding likely under the strongest storms.

In addition to heavy rainfall, large hail (up to 1.5 inches in the Low threat region, but up to 2.5 inches towards the KS border) will be possible along with strong winds up to 75mph and a threat of an isolated tornado.

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: Thursday, May 25th, 2017
Issue Time: 10:00AM MDT

— LOW flood threat for portions of Northeast Plains

A strong disturbance moved into western North America over the past few days, and will influence our weather beginning today. The water vapor image, below, shows that the main circulation is located in southern Saskatchewan today. Draped to the southwest is a trough axis that extends into the Great Basin. As this disturbance approaches Colorado, it will cause large-scale lift and generate plenty of showers and thunderstorms. West of the Continental Divide, limited instability will keep rain rates below flood-prone intensity. East of the Continental Divide, a pocket of higher moisture exists in northeast CO today. Acting against this is a plume of very dry air being advected from the southwest by a strong subtropical jet. This will limit the heavy rainfall threat to areas along the Nebraska border. Also acting against the flood threat will be very swift storm motions, above 40mph. Nonetheless, a Low flood threat has been issued for parts of the Northeast Plains for isolated flash flooding.

Perhaps the bigger story today will be the potential for severe weather – most notably gusty winds up to 75mph and large hail, up to 1.5 inches. These hazards will occur with the strongest storms. However, overall, expect windy conditions across northern Colorado today as high jet stream speeds get mixed downward into the boundary layer courtesy of solar heating.

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, Front Range, Urban Corridor:

Mostly clear this morning then increasing clouds with scattered showers and thunderstorms developing by early afternoon. Early activity will start in the higher elevations, then transition eastward into the plains. Max 1-hour rainfall up to 0.7 inches, except up to 1.6 inches in the Northeast Plains. Hail up to 1.5 inches and gusty winds up to 75 mph will be possible with the strongest storms. Isolated flash flooding will be possible. Field and road flooding will be likely with the heaviest downpours.

Primetime: 2PM to 9PM (across far east)

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

Partly to mostly cloudy skies with scattered showers increasing in coverage. Weak thunderstorms are possible in the afternoon. Max 1-hour rainfall up to 0.4 inches with max 24-hour rainfall up to 0.6 inches. Small hail (less than 0.5 inches) will be possible. Snow level 11,000 feet. Gusty winds up to 60mph are expected in the higher elevations today, especially along mountain passes. Flooding is not expected today.

Primetime: 11AM to 8PM

Southeast Plains, Palmer Ridge, Raton Ridge, Southeast Mountains

Mostly sunny early, then increasing clouds with a few showers and a weak thunderstorm possible in the early afternoon. Max 1-hour rain rates up to 0.4 inches. Small hail will be possible with the strongest storms. Gusty winds up to 50mph will accompany the strongest storms. Flooding is not expected today.

Primetime: 2PM to 7PM

Issue Date: Wednesday, May 24th, 2017
Issue Time: 10:08AM MDT

— Flooding is NOT expected today
— Elevated fire danger across the Southwest Slope

It is a “severe clear” morning across Colorado and surrounding states on this Wednesday. Precipitable water values have dropped to 0.4 inches or lower statewide as a transient ridge builds into the region, if only for a day. Subsidence will allow for much warmer temperatures today than the past few days. Even so, only slightly above normal temperatures are expected, a testament to just how chilly the weather has been over the past week or so.

Moving our eyes farther northwest (see water vapor image below), we see across southwest Canada and the US Pacific Northwest the disturbance that will affect our weather starting on Thursday. The first wave of dynamics from this storm will move into northwest Colorado later this evening and into the overnight hours. With little moisture to work with, only light rain and snow showers are expected. Things will change markedly tomorrow as moisture returns in abundance. Stay tuned to tomorrow’s Flood Threat Bulletin for details.

For today, flooding is not expected statewide.

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:

Northwest Slope, Northern Mountains:

Sunny and much warmer today with temperatures slightly above seasonal normal. Gusty winds will develop this afternoon as the boundary layer grows and taps into strong winds aloft. Isolated rain and snow showers are expected starting later this evening and into the overnight hours. Max 1-hour precipitation rates up to 0.1 inches. Flooding is not expected today.

Primetime: 10PM through 6AM

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

Mostly sunny and much warmer today with temperatures peaking just above seasonal normal. Gusty winds will be likely across higher elevation locations this afternoon as the boundary layer grows. A Red Flag Warning has been posted for far southwest Colorado as low afternoon moisture levels will combine with gusty winds to elevate the fire threat. Stay tuned to local media for the latest fire information.

Flooding is not expected today.