Issue Date: 5/11/2015
Issue Time: 10:10 AM

A MODERATE FLOOD THREAT HAS BEEN ISSUED FOR THE CACHE LA POUDRE/SOUTH PLATTE RIVER FROM GREELEY THROUGH STERLING, AND FOR THE ARKANSAS RIVER FROM PUEBLO THROUGH LA JUNTA.

After the last 10 days of rain, it feels good to say that today will be cool and dry with mostly sunny skies as high pressure builds over the region. Aside from continued flooding along the South Platte River and Arkansas River outlined above, swollen streams will recede and standing water will dry up as the sun and westerly winds do their part. The water vapor image below really tells the whole story today; Colorado is positioned in a region of drier air and subsidence between the upstream ridge and downstream trough. This means that on the large-scale, conditions are very favorable for sunny skies. At the surface, high pressure continues to build across the state, with very little moisture left behind as dewpoints are in the 20s and 30s. The only exception to all of the sunshine and dry conditions will be a few light showers possible across the highest terrain, owing to the mountains natural ability to force weak vertical motion today. All precipitation totals should be less than 0.1 inch. Otherwise, mostly sunny skies are in store for Colorado.

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, and Southeast Plains:

Mostly sunny and cool, with highs ranging from the mid-50s to low 60s across the Plains, to the low-to-mid 50s across the Palmer Ridge and Urban Corridor.

Front Range, Northern Mountains, Central Mountains, Northwest Slope, San Juan Mountains, and Southwest Slope:

Partly sunny, with a few showers this afternoon and evening over the highest terrain. Expect any showers to produce less than 0.1 inch of rainfall. High temperatures will range from the 30s over the highest terrain to the upper 40s for the valleys.

Southeast Mountains and Raton Ridge:

Mostly sunny, with one or two showers this afternoon and evening over the mountains. Rainfall totals will be less than 0.1 inch. High temperatures will be in the upper 50s/low 60s for the lowest elevations, and in the upper 30s/low 40s for the mountains.

Grand Valley and San Luis Valley:

Mostly sunny, with high temperatures warming into the 60s. Slightly higher elevations will see highs in the upper 40s and low 50s.

Issue Date: May 10th, 2015
Issue Time: 10:15AM

— MODERATE flood threat for South Platte River from Greeley through Sterling
— MODERATE flood threat for Arkansas River from Pueblo through La Junta

The departing of yesterday’s impressive late spring snowstorm has left partly to mostly cloudy skies across most of Colorado. Snow showers are still ongoing across mainly the higher terrain. Today will finally bring necessary, but intermittent sunshine along with some drying especially for lower elevations. The water vapor imagery below shows the departing storm currently positioned over western Nebraska and South Dakota. As it moves farther away from Colorado, all precipitation should slowly come to an end this afternoon and evening. Sunshine will try to break through the clouds but may have a difficult time with so much low-level moisture remaining in the saturated ground. Temperatures will be unseasonably cold for this time of year with mountain locations staying in the 20s, while lower elevations warm to the 30s and 40s. The only exception is the southeast corner of the state where temperatures may climb to 60F.

Although there is no significant precipitation in the forecast today, Moderate flood threats have been posted for the Arkansas River from Pueblo through La Junta, and for the South Platte River from Greeley through Sterling. At this time, it appears that the additional snowmelt will add more runoff for the next 12-24 hours and most rivers should see their crest by midday tomorrow.

Please see below for area-specific flood threat and forecasts (click on “About the FTB” link above to view Colorado region names).

 

Zone-Specific Forecasts

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

Scattered snow showers will slowly diminish over the late morning and afternoon hours. Sunshine will try to break through the clouds this afternoon. No significant precipitation is forecasted today, but a Moderate flood threat is in place for the South Platte River from Greeley through Sterling. Parts of this stretch of the South Platte are already in “Action” and Minor Flooding stages. The river is likely to rise a bit more throughout the day before cresting tomorrow. Please keep an eye on National Weather Service warnings for specific flood information.

Central Mountains, San Juan Mountains, Southeast Mountains and Northern Mountains:

Scattered snow showers will persist into the early afternoon hours. Additional snow accumulations of up to 10 inches may occur in isolated locations. No flood threat is expected today and cold temperatures prevent runoff. However, flooding concerns may arise as warm temperatures return in the coming days.

Southwest Slope, Northwest Slope, Grand Valley and San Luis Valley:

Partly cloudy and cool with isolated snow showers possible through early afternoon. No flooding is expected today. However, snowmelt induced flooding concerns may begin to develop as temperatures warm in the coming days.

Issue Date: May 9th, 2015
Issue Time: 10:10AM

— HIGH flood threat for parts of Palmer Ridge
— MODERATE flood threat for Urban Corridor, Palmer Ridge, most of Northeast Plains and parts of Southeast Plains
— LOW flood threat for Raton Ridge, parts of Southeast Plains and Northeast Plains

The Mother’s Day weekend storm of 2015 is aimed directly at Colorado. What that means for today’s weather is a little bit of everything: heavy snowfall, high and persistent rainfall intensities and severe weather in the Southeast Plains where temperatures could soar into the upper 60s by late afternoon. The water vapor image below captures the main features of the state of the atmosphere. A partially cut-off low continues to march east-northeastward and is now located over the Four Corners region. An impressive disturbance is currently noted in eastern Colorado and clearly seen on the water vapor. This disturbance is accompanied by good low-level moisture convergence and is currently producing rain rates up to 1 inch per hour in Northeast Colorado. Across and west of the Continental Divide, the atmosphere has substantially cooled as the low-pressure draws near. The San Juan mountains are already seeing heavy snow, with isolated thunderstorms reported.

Regarding today’s forecast, rain and snow showers and thunderstorms will continue across most the state. Hourly rain rates will average around 0.5 inches, except in isolated heavy cells where 1.0 inch per hour rates are possible. Total 24-hour rainfall amounts of 1-2 inches will be widespread across Eastern Colorado, with isolated amounts up to 4 inches possible. In the San Juans, Central and Northern mountains, heavy snow will cause travel problems over the higher passes, where snowfall rates up to 1.5 to 2 inches an hour are likely.

Meanwhile, clouds are breaking along the New Mexico border, which will allow the May sun to quickly heat the atmosphere into the 60s and possibly 70F. As the upper-atmosphere cools, the combination of instability, high moisture content, good directional and speed shear may produce an outbreak of severe weather in the Southeast Plains. Large hail up to 2 inches, very strong winds up to 80 mph and tornadoes are all possible in the strongest of storms. The storms will race to the north around 50 mph, which will help to limit hourly rain rates to about 1.7 inches per hour. This may cause isolated flash flooding. The Prime Time for the severe weather is between 1PM and 8PM this evening.

We encourage everyone to pay attention to National Weather Service watches and warnings for heavy snowfall, flooding and severe weather updates throughout this active weather day.

Please see below for area-specific flood threat and forecasts (click on “About the FTB” link above to view Colorado region names).

Zone-Specific Forecasts

Urban Corridor, Front Range, Northeast Plains:

Showers and thunderstorms continuing throughout the day and into the late evening. An isolated strong storm is possible with some small hail. Rainfall rates of 0.5 inches per hour will be common, though stronger storms may produce rates up to 1 inch per hour. A Moderate flood threat has been posted for parts of the area due to saturated soils and high stream levels.

Prime time: 11AM through 10PM

Palmer Ridge, Southeast Plains, Raton Ridge and Southeast Mountains:

Scattered showers and storms this morning, redeveloping and strengthening in the afternoon, lasting into the late evening hours. Strong to severe storms will be likley from the afternoon through the late evening hours. Isolated rainfall rates up to 1.7 inches per hour are possible, accompanied by localized flash flooding. Large hail up to 2 inches, strong winds up to 80 mph and tornadoes are all possible with stronger storms. A High Flood threat is in place from Colorado Springs through Pueblo. Moderate and Low flood threats are also in place due to saturated soils.

Prime time: 1PM through 10PM

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

Scattered showers and isolated thunderstorms through the morning slowly transitioning to snow showers above 9,000 feet. Small hail is possible in the stronger thunderstorms. Snow levels will drop throughout the day to about 6,000-7,000 feet by this evening. Rainfall rates up to 0.6 inches will be possible before the rain turns to snow. No flooding is expected due to the transition to snow, thus slowing and limiting the runoff.

Issue Date: May 8th, 2015
Issue Time: 10:55AM

— Moderate flood threat for parts of Palmer Ridge
— Low flood threat for Front Range, Urban Corridor, Palmer Ridge, Southeast Mountains and parts of Northeast Plains and Southeast Plains

An already active weather pattern is about to get even more active across Colorado. The water-vapor image below shows the key players in the atmosphere today. A cut-off upper-level low pressure system is centered over Southern California this morning. It accounted for much needed rainfall over California and is now progressing east-northeastward towards Colorado. Within its flow, two additional disturbances are noted this morning, as shown by the dotted black lines. The first disturbance, already halfway across Colorado, is accounting for showers and isolated thunderstorms stretching from the Northwest Slope southeast through the Palmer Ridge regions. This disturbance is confirmed by visible satellite imagery showing a boundary between cloudy skies to its northeast and sunny to partly cloudy skies to the southwest. A second disturbance over Utah and Nevada will progress eastward and reignite shower and thunderstorm activity across Colorado later this afternoon.

As has been the case all week, precipitable water (PW) values continue to run high east of the Continental Divide, with this morning’s numbers coming in between 0.7 and 0.8 inches. As the low-pressure system approaches from the east it is likely that higher PW values will be transported into Colorado from the southeast. PWs of 0.9 inches will be possible across the Southeast Plains region, which will help maintain a heavy rain threat. Another factor to consider in today’s flood threat is the high amounts of antecedent rainfall that have occurred over the past 7 days. Soils are either saturated or close to it across most of the Palmer Ridge and Urban Corridor and even the Grand Valley regions where weekly rainfall amounts of 2 to as high as 6 inches have occurred. Furthermore, several rivers, notably the South Platte and Fountain Creek continue to slowly rise and are approaching or already in “Action” levels (note that the “Action” level is the precursor to a “Minor flooding” level).

Taking all the factors together, today’s forecast is for the ongoing shower and storm activity to continue with more redevelopment in the afternoon. A Low flood threat is once again in place along the entire length of the I-25 corridor. Afternoon thunderstorm activity in the Southeast Plains may contain strong to severe thunderstorms capable of producing winds up to 60 mph, hail up to 2 inches in diameter and heavy rainfall up to 1.7 inches per hour. A Moderate flood threat has been posted over the Palmer Ridge for Fountain Creek due to elevated streamflow and more rainfall on the way.

As the main flood threat begins to subside later this evening, rain will change to snow overnight with snow levels slowly dropping to about 7,000 feet by Saturday. For the second year in a row, we will likely see a significant Mother’s Day snowstorm over the higher terrain.

Please see below for area-specific forecasts (click on “About the FTB” link above to view Colorado region names).

Urban Corridor, Front Range, Northeast Plains:

Showers and isolated thunderstorms continuing into the afternoon and early evening. An isolated strong storm is possible with some small hail. Rainfall rates will generally stay lighter than 0.5 inches per hour. A Low flood threat has been posted for parts of the area due to saturated soils. The South Platte River needs to be watched from Denver through Fort Morgan as it is approaching “Action” levels in many gages with more rainfall on the way.

Prime time: Noon through 8PM

Palmer Ridge, Southeast Plains, Raton Ridge and Southeast Mountains:

Showers and storms ending later this morning, but redeveloping in the afternoon and lasting into the late evening hours. Strong to severe storms will be possible from the afternoon through the late evening hours. Isolated rainfall rates up to 1.7 inches per hour are possible, accompanied by localized flash flooding. A Flood Advisory is already in place west of Colorado Springs this morning, prompting a Moderate flood threat from Colorado Springs down to the Arkansas River. A Low flood threat is in place elsewhere.

Prime time: 1PM through 10PM

Central Mountains, San Juan Mountains, San Luis Valley and Southwest Slope:

Partly cloudy skies this morning with showers and perhaps a weak thunderstorm developing in the early afternoon. Rainfall rates will stay below 0.4 inches per hour. No flood threat is expected. Later this evening, rain will transition into snow with snow levels dropping into the higher valleys overnight.

Northwest Slope, Grand Valley, and Northern Mountains:

Ongoing showers this morning with more redevelopment in the afternoon. An isolated thunderstorm cannot be ruled out. Rain rates will stay below 0.3 inches and hour. Despite the rainfall over the past few days, no flood threat is expected due to the light rainfall intensity today. Rainfall will increase in coverage overnight as a disturbance approaches from the west. Rain will turn into snow in the higher elevations, with snow levels dropping overnight.