FTB 05-26-2017: Moderate Flood Threat Today, Accompanied By Severe Weather

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.

Flood Threat Legend

Zone-Specific Forecasts:

Northeast Plains, Front Range, Urban Corridor, Palmer Ridge, Southeast Plains:

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 1.6 inches except up to 2.4 inches in farthest east areas. Max 3-hr rainfall up to 2.9 inches. Hail up to 2.5 inches and gusty winds up to 75 mph will be possible with the strongest storms, along with the threat of an isolated tornado. Isolated flash flooding will be possible under the strongest storms. Field and road flooding will be likely with the heaviest downpours.

Primetime: 1PM to 9PM (across far east), with isolated showers continuing overnight

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

Partly to mostly cloudy skies with scattered showers and perhaps a weak storm this afternoon. Weak thunderstorms are possible in the afternoon. Max 1-hour rainfall up to 0.4 inches. Small hail (less than 0.5 inches) will be possible. Snow level 11,000 feet early, lowering to 9,500 feet later in the day. Flooding is not expected today.

Primetime: 11AM to 8PM, with isolated showers continuing overnight

Raton Ridge, Southeast Mountains

Mostly sunny early, then increasing clouds with an isolated shower or 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

FTB 05-25-2017: Severe Weather Is The Headline, Along With Low Flood Threat

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.

Flood Threat Legend

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

FTB 05-24-2017: Sunny And Warm, Though Only For A Day

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.

FTB 05-23-2017: Isolated Afternoon Showers Out East; Otherwise Pleasant

Issue Date: Tuesday, May 23rd, 2017
Issue Time: 8:30AM MDT

— Flooding is NOT expected today

This morning’s visible satellite imagery shows a mostly clear start for nearly all of Colorado. The exception is a few bands of low/mid-level clouds across the Northeast Plains. This is actually associated with yet another disturbance that is rotating around the central United States trough that was described yesterday. Fortunately, today’s disturbance is significantly weaker than the past few days, and in fact will be weakening further throughout the day. In addition, the atmosphere is drier today with precipitable water values less than 0.5 inches statewide. While the aforementioned disturbance will graze mainly eastern Colorado with some light showers, partly to mostly sunny skies are expected for everyone else. Thus, no flood threat today.

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:

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

Mostly sunny this morning, then increasing clouds with isolated to scattered showers possible, mainly across eastern areas. Max 1-hour rain rates up to 0.2 inches. Flood is not expected today.

Primetime: 1PM to 6PM

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

Mostly sunny with warmer temperatures. An isolated rain/snow shower is possible in the Northern Mountains this afternoon, though less than 0.05 inches of precipitation is expected. Flooding is not expected today.

Primetime: 1PM to 5PM