Issue Date: 5/12/2016
Issue Time: 9:20 AM

NO FLOOD THREAT IS FORECAST.

A picture is worth a thousand words, and that holds true with this morning’s visible satellite image (shown below). High pressure at the surface and a building ridge aloft will be in charge of Colorado’s weather today/tonight, allowing for sun-drenched skies and warmth to take over. Over the highest terrain, virga will be present during the afternoon/early evening as the daytime heat works on the surface/residual moisture, but no precipitation is expected to reach the surface. This “activity” will bring about some gusty winds, and that’s about it.

Otherwise, a few fair weather cumulus clouds will be noted across the lower elevations of eastern Colorado, mainly along and near the higher terrain. For tonight, the only weather highlight will be gusty winds (25-35 mph) across the Front Range and Front Range foothills.

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

Sunny skies and temperatures warming back to average will be the weather story today. Some high-based, fair weather cumulus clouds will drift overhead today, mainly for locations along and near the higher terrain. High temperatures will be in the 60s and 70s.

Overnight, skies will be mostly clear with temperatures dipping to seasonal lows.

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

Mostly sunny and warmer, with high temperatures warming right up to average for this time of year. High-based clouds and virga will develop overtop of the highest terrain this afternoon/early evening, but no precipitation is expected to reach the surface; brief gusty winds will be the main result.

Overnight, the main weather highlight will be gusty winds (25-35 mph) developing over the Front Range/foothills. Otherwise, skies will be mostly clear.

Issue Date: 5/11/2016
Issue Time: 9:42 AM

A LOW FLOOD THREAT CONTINUES FOR THE CACHE LA POUDRE RIVER FOR LOW-LYING AREAS.

An upper-level trough will slowly move eastward across the Northern Rockies/Great Plains today, with a disturbance rounding the base of the trough and across Colorado this afternoon/evening. This disturbance will help kick off another round of showers/thunderstorms today, albeit in less numbers than previous days. Coverage will be isolated overall, with more scattered coverage expected across the Palmer Ridge, Southeast Plains, and Raton Ridge regions. The IPW chart more or less bears this out, showing better moisture in place at the Pueblo station (pink like), with moisture taking a dip from yesterday at the Grand Junction, Shriever AFB, and Boulder stations.

No flood threat is warranted from thunderstorm activity today, as instability values will be low and moisture has been lessened from previous days. However, there is potential for a stronger storm or two across the Palmer Ridge, Raton Ridge, and Southeast Plains; shear and instability will be best here. At any rate, the threat from the strongest storms will be lightning, gusty winds, small hail, and brief moderate-to-heavy rainfall. Precipitation will come to an end tonight across most regions as ridging/drier air works into the state, with only a few lingering showers remaining over the Southeast Plains/Raton Ridge into early tomorrow morning.

For a breakdown on what to expect in each region, see the region-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, Southeast Plains, Palmer Ridge, Raton Ridge, and Northeast Plains:

Scattered showers and thunderstorms expected this afternoon and evening, mainly along and south of I-70. An isolated shower/weak thunderstorm or two will occur north of there. The main threats from any stronger thunderstorm will be small hail, lightning, gusty winds, and brief moderate-to-heavy rainfall. Rain rates will generally be light in the 0.2-0.4 inches/hour range. Maximum rain rates from thunderstorms will be 0.4-0.7 inches/hour, mainly across the Palmer Ridge, Southeast Plains, and Raton Ridge.

Activity will diminish during the late evening/overnight hours from north-to-south and west-to-east. Only a couple showers will linger into the early morning hours across the Southeast Plains/Raton Ridge.

Primetime: 11 AM – 11 PM

Front Range, Northwest Slope, Northern Mountains, Grand Valley, Central Mountains, and Southwest Slope:

Isolated showers and weak thunderstorms are expected over the higher terrain this afternoon and early evening. Subsidence and drying will move in during the nighttime hours bringing an end to activity. Rain rates will be low (0.1-0.25 inches/hour).

Timing: 11 AM – 8 PM

San Juan Mountains, Southeast Mountains and San Luis Valley:

Isolated-to-widely scattered showers/weak thunderstorms are expected, mainly over the higher terrain. The San Luis Valley will largely miss out on any precipitation. Activity will mostly come to an end during the late evening/overnight hours. Rain rates will be low, ranging from 0.15-0.3 inches/hour.

Timing: 11 AM – 10 PM, with a few lingering showers into the early morning hours.

Issue Date: 5/10/2016
Issue Time: 9:58 AM

A LOW FLOOD THREAT IS FORECAST FOR PORTIONS OF THE NORTHEAST PLAINS, SOUTHEAST PLAINS, AND PALMER RIDGE. A LOW FLOOD THREAT CONTINUES FOR THE CACHE LA POUDRE RIVER FOR LOW-LYING AREAS.

On top of this morning’s water vapor image, I have labeled the approximate locations of a couple key features to this period’s forecast. The Low labeled “300 mb” is the upper-level low center, “jet streak” is the location of the upper-level jet streak, and the low labeled as “Sfc” is the surface low center. The cool front is currently draped across Colorado, back into northern AZ, and will not move southward much through the day today, with the boundary finally pushing out of the state around midnight tonight.

Overall, as the jet streak sinks to the south in response to the upper-level low drifting southward, the best large-scale lift will reside along (and south of) a corridor from the Southwest Slope to the southern half of the Northeast Plains. This area of “best” lift will sit overtop the cool front boundary and upslope flow regions, providing a focus for the most shower/thunderstorm activity. A few strong thunderstorms are possible across the Palmer Ridge, southern portions of the Northeast Plains, and northern portions of the Southeast Plains. These locations are outlined by the low flood threat area.

Over the mountains this afternoon/evening, showers and weak thunderstorms will mainly be focused along the frontal boundary and over the higher terrain south of I-70. One or two showers/weak thunderstorms could develop over the higher terrain of the Northern Mountains as daytime heating warms the mountains, but not much is expected due to unfavorable upper-level conditions.

Overnight, activity will end from north to south as the front exits and upper-level subsidence takes over. However, a few will linger into the morning hours across the southern half of Colorado until the subsidence arrives.

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

Isolated-to-scattered showers/thunderstorms, mainly south of I-76 and north of Highway 50. A couple storms will become strong-to-marginally severe across the Palmer Ridge, northern portions of the Southeast Plains, and southern portions of the Northeast Plains. Rain rates will generally be light (0.1-0.3 inches/hour) except for under strong thunderstorms, where maximum rain rates will push 1.6-2.0 inches/hour. Dry air underneath the thunderstorms will limit that somewhat, and storm motions will help mitigate the flood threat, as well. Thus, only a low flood threat is warranted.

Timing: 11 AM – 8 PM, with a few lingering into the overnight/early morning hours

Front Range, Grand Valley, Northwest Slope, and Northern Mountains:

Isolated showers and weak thunderstorms possible north of I-70, with more widely scattered coverage to the south. The Northwest Slope will be the driest region during this period, overall. Rain rates will generally be light at 0.1-0.2 inches/hour, with thunderstorms over the Front Range producing the best rain rates at 0.2-0.4 inches/hour.

Timing: 11 AM – 10 PM

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

The higher terrain along the frontal zone will be favored for scattered showers and thunderstorms throughout the period, with isolated showers/weak thunderstorms elsewhere. Rain rates will generally be light, with maximum rain rates of 0.15-0.3 inches/hour. Activity will largely diminish overnight, but a few isolated showers will linger until around midnight near the southern CO border.

Timing: 11 AM – 10 PM

Issue Date: 5/9/2016
Issue Time: 9:52 AM

NO FLOOD THREAT IS FORECAST.

An upper-level trough will shift eastward across Colorado today, bringing another day of unsettled weather to the state. Precipitable water values are near average for the lower elevations east of the mountains, but are still elevated across the High Country. The IPW chart shows just that: The Grand Junction station is by itself at the top of the chart (green line), reporting IPW values in the 90th percentile for the date.

The availability of better moisture, plus orographic support, will result in areas along and west of the Continental Divide receiving the bulk of shower/thunderstorm activity through this period. Snow levels will be around 10,000-11,000 feet during the day, falling to 8,000-9,000 feet overnight. Instability values will be less than previous days, leading to slightly lower rain rates. More details will be given in the zone-specific forecast discussions section. Overnight, expect showers (and a weak thunderstorm or two) to continue as another disturbance shifts across Colorado.

East of the mountains and across the lower elevations, showers/thunderstorms will be isolated in coverage, owing to the presence of less moisture/instability/upper-level support than the last few days. The main impacts from any activity in these regions will be lightning, gusty winds, with small hail attending the strongest thunderstorms. Rain rates will remain light, and no flood threat is warranted. Overnight, clouds will increase across northeast Colorado as another disturbance moves across the region.

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

Isolated showers and thunderstorms expected this afternoon and evening, diminishing after sunset as daytime heating ceases. The main impacts from any activity will be light rain, lightning, and gusty winds. Small hail will be possible under the stronger thunderstorms, relatively speaking. Maximum rain rates will vary, with 0.25-0.5 inches/hour for western locations, and 0.6-0.8 inches/hour for locations along/near the eastern border.

High temperatures will be right around average for this time of year. Clouds will increase from north to south overnight as the next disturbance moves into the region.

Timing: Noon – 8 PM

Front Range, Southeast Mountains and San Luis Valley:

Isolated-to-scattered showers and weak thunderstorms expected over the higher terrain, with a couple moving overhead of the San Luis Valley. Rain rates will generally be low, with maximum rates from thunderstorms of 0.15-0.35 inches/hour. Activity will diminish after sunset, with a couple of isolated showers lingering over the higher terrain through the overnight hours.

Timing: 11 AM – 9 PM

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

Scattered showers and thunderstorms are expected today and tonight, with a few lingering into the overnight and morning hours tomorrow. Rain rates will be low, maximizing at 0.3-0.6 inches/hour. Extended periods of rainfall will allow for some locations to pick up more than 0.6 inches of rain by tomorrow morning, mainly across the higher elevations of the Central Mountains and San Juan Mountains regions.

Timing: Activity will increase from now through sunset, and then diminish a bit for the overnight hours. Rain chances exist throughout the entire period, especially across the higher terrain.