Issue Date: Tuesday, July 2, 2019
Issue Time: 11:00 AM MDT

– A LOW flood threat is issued for the Front Range, Southeast Mountains, Urban Corridor, Raton Ridge, Palmer Ridge, and portions of the Central Mountains, Northeast Plains, and Southeast Plains. Included in the threat are the Spring Creek and Junkins burn areas.

– A LOW flood threat is issued for the Eagle River near Gypsum, Arkansas River between Avondale and La Junta and the Crystal River near Redstone

Rainfall returns today after two active days with a Low flood threat issued. Upper level flow has shifted to the west southwest with the breakdown of the ridge. Thus, flow will continue to be more zonal today. A shortwave and surface low pressure system over southern Wyoming will move east with the flow, and will help advect moisture north throughout the day.  Storm generation will be due to diurnal heating and upslope flow, with most storms peak intensity midafternoon over the southern Front Range.

Surface moisture remains high statewide, which will allow for some heavy rainfall once again. While there is a slight decrease in moisture, fairly slow steering winds and antecedent moisture from the last two days should increase runoff. This is especially true near the Spring Creek burn area and over the lower Arkansas River between Avondale and La Junta, which is already running high due to dam release. Thus, there is a Low flood threat issued over these areas.  Storm motion will be to the east southeast at 15-20 mph, which could allow for decent accumulation under a couple storm cores, although storm coverage will decrease from yesterday.  Dew points over the eastern plains this morning measured in the 60°Fs and mid to upper 50°Fs, with PW values up to 1.3 inches over the southeast corner (green lines below).  Morning and early afternoon cloud cover will limit temperatures from increasing above 90°Fs over the plains and help keep the area capped when it comes to strong convection.  West of the Continental Divide, dew points measure in the mid to upper 40°Fs.  With slightly lower dew points, and high pressure overhead, rainfall will be limited to weak afternoon thunderstorms.

Remnants of the low pressure system that effected the plains yesterday remains over the far eastern edge of the state, with a stationary front spanning to the east along the Palmer Ridge.  Storms are forecast to initiate along this boundary early in the afternoon.  A low pressure system over the CO/WY border is providing lift along a dry line (orange line) with precipitation currently over the Grand Valley and Central Mountains.

Flood threats today from rainfall include flooding of small streams (especially at higher elevations where they are already running high), roads and low lying areas. Over the high country, mud flows and debris slides may be possible over the Spring Creek and Junkins burn scars if storms track into the area. Elevated flows continue at high elevations along the Eagle River at Gypsum, the Crystal River near Redstone, as well as the Boulder Creek at Nederland and Orodell. Due to saturated soils, streams and creeks in the high country may rise rapidly if a storm tracks into the area. This may cause some minor flooding issues and destabilize banks, so please use extreme caution. Be sure to follow your local NWS office for the latest flood warnings and advisories as they will be updated throughout the day.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

Zone-Specific Forecasts:

Front Range, Urban Corridor, Southeast Mountains, Raton Ridge

Early afternoon thunderstorms are anticipated due to upslope flow and high moisture over the area. Max 1-hour rainfall rates of up to 1 inch will be possible over the southern Front Range, with rates approaching 0.75 inches over the Southeast Mountains. This may cause flooding issues for the Spring Creek and Junkins burn areas. Moderate rain rates from more general storms could lead to flooding due to the saturated surface. Easterly and Southeasterly winds will push storms over the adjacent plains midafternoon. A Low flood threat has been issued over the area.
Primetime: 1PM to 12AM

Northeast Plains, Palmer Ridge, Southeast Plains

High levels of surface moisture this morning combining with upslope flow will cause thunderstorms that track into the area to produce some decent accumulations. . Storms are expected to move off of the mountains over the plains midafternoon. Additionally, lift will be enhanced over the Cheyenne Ridge due to the surface low passing to the north, so some storms may drift into the Northeast Plains along the northern border. Max 1-hour rain rates of 1.5 inches may be realized over the Low threat area, but rain rates over the far eastern border should remain below flood threat criteria with the cloud cover taking a while to burn off. Flows remain high along the Arkansas River from Avondale to La Junta from releases and rainfall yesterday, which may cause flooding of low lying areas. Storms should come to an end by 2AM, thus ending the flood threat.
Primetime: 3PM to 2AM

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

While low level moisture is decreasing over the area, there should be enough antecedent moisture present for afternoon storms over the high country. Upslope flow is forecast to trigger isolated thunderstorms this afternoon favoring the San Juan Mountains and Central Mountains. Max 1-hour rain rates up to 0.4 inches may be possible over the San Juan Mountains and Central Mountains with 1-hour rain rates decreasing over the Northern Mountains to 0.25 inches. A little faster storm motion should keep the flood threat at bay over the 416 burn area, but use caution if storms track over the burn scar. High flows along the Eagle River near Gypsum and Crystal River near Redstone has prompted a Low flood threat for the area as storms that track over these areas may cause some minor flooding issues.
Primetime: 2PM to 8PM

Issue Date: Monday, July, 1st, 2019
Issue Time: 9:10AM MDT

–A MODERATE flood threat is issued for the Palmer Ridge, Northeast Plains, portions of the Urban Corridor and the Spring Creek burn area.

–A LOW flood threat is issued for Front Range, Southeast Mountains, Urban Corridor, Raton Ridge and Southeast Plains. This includes the Junkins and Hayden Pass burn areas.

Heavy rainfall returns to the forecast to kick off the first day of July with a Moderate flood threat issued. Southwest flow aloft will begin to turn more westerly throughout the day as the upper level ridge begins to break down. This is in part due to the passage of a shortwave rotating around the high over Mexico. This shortwave will help spark more widespread showers and thunderstorms this afternoon. The current pattern continues to stream in moisture at the mid and upper levels as well, so this will help increase rainfall efficiency with storms this afternoon and evening. In the low level water vapor image below, a very moist air mass is in place over eastern Colorado as shown by the dew points (green lines). Additional moisture will get pulled in over eastern Colorado today with a surface low, which is currently over the eastern plains, siphoning in higher low level moisture (increasing dew points) from the south and east. There is no sounding at Denver this morning, but models and nearby soundings indicate PW values around 1 inches will be present over the Urban Corridor by this afternoon as storms move off the high terrains. As expected, values increase to the east with PW around 1.25 inches over the eastern plains. A weak cold front will produce a wind shift over the Palmer Ridge area and east, which will likely produce convergence for a second set of storms over the eastern plains. Storms to the north of the front will have increased moisture, so higher rain rates are anticipated over this area. Storms over the far eastern plains may become severe with the main threats being heavy rainfall, strong winds and large hail. Back over western Colorado, afternoon storms are forecast for the San Juan Mountains and south Central Mountains, but there is no threat with PW values max out around 0.70 inches.

Slow steering winds under the ridge will allow storms today to produce very heavy rainfall over eastern Colorado. Storm motion is expected to be to the southeast at 10-15 mph to the west, and nearly stationary storms are forecast over the eastern plains. Outflow boundaries from activity will likely kick off additional storms in the moisture rich environment. This evening, it looks like an MCS will form over the eastern plains and last through the overnight hours, which will continue the heavy rainfall threat over this area through tomorrow (early) morning.

Universal flood threats from rainfall today are flooding of small streams, roads and low lying areas, especially over urban areas with larger impervious areas. To the east, there will be the additional threats of arroyo flooding and field ponding. To the west over the higher terrains, mud flows and debris slides may also be possible. This is especially true of any storms that track near recent burn areas over the Southeast Mountains. Elevated flows continue at high elevations streams and rivers (including the Arkansas and Colorado) from the warm temperatures last week and rainfall yesterday. It is anticipated that there will likely be another afternoon peak with higher runoff from rainfall today. This may cause some minor flooding over low lying areas, so use extra caution around these areas this afternoon. There was also a release at Pueblo Dam yesterday, so watch for minor flooding along the lower Arkansas from Avondale to La Junta. Be sure to follow your local NWS office for the latest warnings and advisories.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

 

Zone-Specific Forecasts:

Northeast Plains, Palmer Ridge, Southeast Plains:

Heavy rainfall with the additional threats of large hail (1.75 inch diameter) and strong winds are possible over these areas this afternoon and overnight. The highest rainfall totals are anticipated over the Northeast Plains and Palmer Ridge due to the surface low pulling in ample low level moisture to these areas. Max 1-hr rain rates up to 2.25 inches will be possible. An MCS will likely form in the overnight hours, which will continue the threat through early tomorrow morning. Isolated 24-hour totals just under 3 inches will be possible by morning. These rain rates are anticipated to cause flooding of roads, arroyos, rivers/streams and low lying areas. A Moderate flood threat has been issued.

Primetime: 4PM to 4AM

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

Afternoon thunderstorms are expected to kick off with the diurnal flow and shortwave by noon in the moisture rich environment. Storms are forecast to be more widespread over the southern Front Range and Southeast Mountains. Easterly steering flows should push the storms into the adjacent plains by early afternoon. Max 1-hour rain rates up to 1 inch will be possible over the Front Range with max 1-hour values closer to 0.75 inches over the Southeast Mountains. Over the Urban Corridor, max 1-hr rain rates up to 1.2 inches will be possible. A Low flood threat has been issued with a Moderate threat issued for the Spring Creek burn area. A Low threat should suffice for the Junkins and Hayden Pass burn areas. Flash flooding, mud flows and debris slides are possible over the recent burn areas.

Primetime: Noon to 9PM

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

While not quite as much moisture is over western Colorado, there is still some decent low level moisture in place over the southwest corner. This should help produce another round of storms over the San Juan Mountains and south Central Mountains. Isolated weak storms will also be possible over the Grand Valley and Southwest Slope as storms move in from the west. Max 1-hour rain rates up to 0.6 inches may be possible over the Eastern San Juan Mountains with rain rates dropping to 0.25 inches over the lower elevations. Flooding is not forecast.

Primetime: Noon to 9PM

Issue Date: 6/30/2019
Issue Time: 8:20 AM

A LOW FLOOD THREAT HAS BEEN ISSUED FOR PORTIONS OF THE SAN JUAN MOUNTAINS, SOUTHWEST SLOPE, AND CENTRAL MOUNTAINS.

The high-pressure ridge aloft that was a major factor in yesterday’s weather has not budged much at all, and it remains the major feature across the central United States. East of the Continental Divide, this will result in a near carbon copy of yesterday. Hot temperatures will be the main weather story again, with sunshine broken up in the afternoon and evening by scattered thunderstorms. Like yesterday, the main impact of these storms will be periods of light rainfall and gusty winds up to 40-50 mph.

Along and west of the Continental Divide, southwesterly flow aloft (marked by green arrows) will bring an increase in mid-level moisture to the area as remnants of Hurricane Alvin make their way across the Great Basin. This will allow for widespread showers and thunderstorms, beginning between 11 AM – Noon, increasing in coverage through the afternoon and evening hours. Due to the fairly consistent fetch of mid-level moisture from the southwest, as well as the approach of the disturbance formerly known as Alvin, expect scattered showers and weak thunderstorms to continue into tomorrow morning.

For more details on 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. For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

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

Above average warmth will be the main weather story today as the high pressure aloft continues to be the major player in the forecast. Like yesterday, scattered thunderstorms will develop over the higher terrain between 11 AM and 1 PM, moving eastward over the lower elevations between 1 PM and 3 PM. Coverage will peak during the late afternoon/early evening, and then taper off as the sun sets. Plenty of dry air below cloud bases will once again result in the main impacts being light rainfall and gusty winds up to 40-50 mph. Rain rates will generally be less than 0.2 inches/hour, with maximum rain rates east of the mountains at 0.2-0.5 inches/hour.

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

Scattered-to-widespread showers and thunderstorms are expected today as an increase is mid-level moisture overspreads the area from the southwest. Low-level moisture remains on the lower end, so the main impacts will be periods of light-to-moderate rainfall, gusty winds up to 50 mph, and a few instances of pea-sized hail. Generally speaking, rain rates will be 0.05-0.2 inches/hour, with maximum rain rates 0.2-0.5 inches/hour. The low flood threat stems from the potential for multiple periods of moderate rainfall moving over the same area.

Timing: 11 AM – Midnight, with scattered showers/thunderstorms lingering into tomorrow morning

Issue Date: 6/29/2019
Issue Time: 7:52 AM

NO FLOOD THREAT IS FORECAST TODAY.

Another hot day is in store across Colorado, although high temperatures will be trimmed a degree or two compared to yesterday thanks to increased cloud cover this afternoon. This cloud cover will be generated by scattered afternoon/evening showers and thunderstorms; the activity will get its start over the higher terrain by 11 AM – 1 PM before working east over the lower elevations by 1 PM – 3 PM. The moisture fueling this activity is situated mainly in the mid-levels of the atmosphere, so the main impacts will be light rainfall and gusty outflow winds up to 40-50 MPH. A couple stronger storms east of the mountains will produce a bit heavier rain later in the evening as outflow from previous thunderstorms increases low-level moisture a bit, but not enough to warrant any flood threat issuance. Instead, this brief heavier rainfall will likely produce some street/field ponding, and not much more.

Since the showers and thunderstorms will be driven mainly by daytime heating, expect activity to begin winding down after 8-9 PM. A few showers/weak thunderstorms will linger over the higher terrain into the morning hours tomorrow as the next bout of moisture from the southwest begins to move into the region. For more details on 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. For Zone-Specific forecasts, jump below the map.

Zone-Specific Forecasts

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

Hot temperatures will be widespread, albeit a degree or two cooler than yesterday thanks to a few more clouds this afternoon. Scattered thunderstorms will move off the mountains and over adjacent lower elevations between 1 and 3 PM. Due to fairly dry lower-levels, thunderstorms will produce more gusty outflow winds than rain, and these gusty outflow winds will help storms to develop further east over the plains with time. Most rain rates will be less than 0.2 inches/hour, with a couple stronger thunderstorms capable of rainfall up to 0.4 inches/hour. Thunderstorm wind gusts up to 55 mph will be possible.

Timing: 1 PM – 10 PM, with a few isolated thunderstorms lingering until Midnight

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

Summertime warmth will be broken up by scattered showers/thunderstorms this afternoon. Activity will get its start over the higher terrain by 11 AM – 1PM, spreading over lower elevations thereafter. Gusty outflow winds up to 40-50 mph and light rainfall will be the main impacts, along with occasional cloud-to-ground lightning. A few showers/weak thunderstorms will linger into the morning hours tomorrow as the next round of moisture begins to move in from the southwest. Rain rates will generally be less than 0.1 inches/hour, with thunderstorms producing rainfall up to 0.1-0.3 inches/hour.

Timing: 11 AM – 9 PM, a few lingering showers/weak storms into the morning hours tomorrow