Issue Date: Saturday, July, 6th, 2019
Issue Time: 9:40AM MDT

–A MODERATE flood threat is issued for the Spring Creek burn area
–A LOW flood threat is issued for the Northeast Plains, Southeast Plains, Raton Ridge and portions of the Southeast Mountains and Palmer Ridge. This threat includes the Junkins burn area.

A little bit of cloud cover to start the day over the southern portion of the state and over the eastern plains. Taking a look at the water vapor imagery below, there is quite a bit of moisture over these areas with dew points in the 50°Fs to the east. A weak ridging pattern will be over the state today with a couple shortwaves passing through the flow, which should help produce more widespread coverage of storms and allow storms to survive as they move east off the higher terrains. One shortwave is marked in WY/UT with the orange “X” (from the trough to our west) with other shortwaves forecast to rotate around the high over Mexico/TX into the southern tier of the state (dotted orange line). The synoptic pattern is oriented in a way that it will foster a moisture surge from the south, originating from the Pacific and Gulf of Mexico. This should return moisture to the San Juan and southern Central Mountains for some afternoon thunderstorms. PW at Denver this morning was measured at 0.86 inches with a strong moisture gradient (increasing) towards Dodge City, KS where the sounding measured PW at 1.16 inches. Flow aloft will turn more westerly today, so expecting storms that form over the mountains to spill into the adjacent eastern plains later this afternoon and evening. Without favorable upper level dynamics in place, storms will begin to weaken a couple of hours after sundown and as the shortwaves move out of the state.

Best coverage of storms today, in the mountains, will be over the Southern Front Range, southern Central Mountains (closer to the Continental Divide), Southeast Mountains/Raton Ridge and San Juan Mountains. Not quite enough moisture for a flood threat to be issued over the 416 burn area, but 2-3 hour totals in the area could reach up 0.5 inches. A Moderate threat has been issued for the Spring Creek burn area with a Low threat for the Junkins burn area. The main threats are flash flooding and debris slides if a storm tracks over the hydrophobic soils. With a high moisture content over the eastern plains, steering winds over the area at 10-15 mph and saturated soils over Cheyenne and Kiowa Counties, a Low flood threat has been issued. The threat includes the Northeast Plains as storms may move into the area from the Cheyenne Ridge. Threats today include flash flooding of creeks and small rivers, arroyo flooding and street/low lying flooding.

Riverine:

The are currently no NWS Flood Warnings this morning (as of 9:30 AM), although there are plenty of elevated rivers and streams in the high country and across the San Luis Valley. So Minor flooding over lowland areas will be possible for the remainder of this weekend. Please use caution near swift moving water. There is also the possibility of more dam releases, so swollen rivers and creeks downstream of dams are possible and should be monitored closely during recreational activities. Please tune into your local NWS for the latest on Flood Advisories and Warnings, but here are a list of the current Flood Advisories: Frying Pan River below Ruedi Reservoir, Roaring Fork River near Aspen, Blue River below Dillon Reservoir. Additionally, we have had reports of high flows within the SLV along the Conejos and Rio Grande River with Platoro and Terrace Reservoirs looking very full as well. Along the Arkansas River gages at Canon City, Pueblo Dam, Avondale and La Junta are at Action stage. Unless there is a release from Pueblo Dam, these should remain below Minor flood stage today. However, should the heavy rainfall threat be realized over the Raton Ridge, the Purgatoire River will likely increase flows over the Arkansas at the La Junta gage later tonight into tomorrow. With increased chances of rainfall today over the mountains, be prepared for additional rises in elevated rivers and creeks. Again, NWS will update Flood Warnings and Advisories throughout the day, so be sure to follow those closely.

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

Increasing storminess for this afternoon with weak thunderstorms forecast for the mountains and adjacent plains. As storms move into the far eastern plains and Raton Ridge area, increased moisture and slow steering winds will produce heavy rainfall, large hail (up to 1.75 inches) and gusty outflow winds. Max 1-hour rain rates up to 0.75 inches will be possible over the mountains and Urban Corridor due to slightly faster steering winds. Hail may also be possible with some gusty winds, similar to the last couple of days. Max 1-hour rain rates increase to 1.25 inches over the Raton Ridge and Southeast Plains. Over the Northeast Plains, if storms track in from the Cheyenne Ridge, 1-hour rain rates up to 1.75 inches will be possible. A Low flood threat has been issued with a Moderate threat for the Spring Creek burn area. 1-hour rain rates up to 0.75 inches could cause flash flooding, mud flows and debris slides if a storm tracks over these burn areas. A second set of storms form over the Southeast Mountains tonight during the early evening (passing shortwave), but storms will likely dissipate as they move into the adjacent plains.

Primetime: 12PM to 2AM

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

A surge of moisture from the south will bring back thunderstorms and showers to the San Juan and south central Mountains for today with most activity this afternoon and early evening. A couple showers may persist near the Continental Divide through 10PM. Not a ton of moisture in place, but with the additional lift from shortwaves, storms will be more scattered than isolated. Max 1-hour rain rates up to 0.4 inches will be possible with most storms producing between 0.10 and 0.25 inches. Gusty winds will be also be likely along with small hail. There may even be some light showers over the SLV with the lighter rain totals mentioned above. Elsewhere clear and warm conditions will continue. Flooding is not forecast, though trailing storms over the 416 burn area should be monitored closely.

Primetime: 11AM to 10PM

Issue Date: Friday, July, 5th, 2019
Issue Time: 10:45 AM MDT

–A MODERATE flood threat has been issued for the Palmer Ridge and portions of the Front Range, Urban Corridor and Southeast Plains
–A LOW flood threat has been issued for the Southeast Mountains, Raton Ridge, Northeast Plains and the Arkansas River at Avondale

Upper level moisture is returning to the western half of the state after a few days of dry, hot air coming in from the southwest.  The high pressure ridge to our east has begun to break down as a series of shortwaves moved across the central and high plains yesterday. A weak shortwave trough is expected to move over the area today (yellow line below), which will provide upper level forcing for severe thunderstorms over the eastern plains this afternoon and into tonight.  Weak upper level moisture will return from the Pacific (blue in WV imagery below), but dry surface conditions west of the Continental Divide will keep chances of precipitation very low over this area.  Surface moisture over the northeast corner of the state is high this morning, as indicated by fog and cloud cover.  This is due to yesterday’s storms and the passage of a cold front overnight.  There is still a strong surface moisture gradient present from Denver eastward with PW values over an inch on the eastern plains.  Moisture will stick around and increase slightly throughout the day.

The low pressure system that brought us our weather yesterday remains over the southeast corner of the state this morning, bringing in deep, moist air from the south and east.  Dewpoints were measured in the 50°Fs and 60°F east of the foothills this morning.  There is a tight temperature and moisture gradient over the Palmer Ridge (orange line) as cloud cover, fog, and advection of cooler temperatures from the north have prevented temperatures from climbing rapidly.  Surface heating and warm air advection is expected to mix out the cloud layer by early afternoon, which will allow temperatures and instability to increase.  Severe thunderstorms are expected to form this afternoon over the Urban Corridor and Palmer Ridge and move eastward over the eastern plains early this evening. Storms are also possible over the northern border that will form and move off the Cheyenne Ridge. Storms over the far CO/KS border may persist overnight with support from the passing shortwave and LLJ. This will drop some heavy 2-3 hour rainfall totals, which could cause some flooding issues. Storm motion is forecast to be 10 to 15 mph to the east and back building/trailing storms will allow for some decent  2 to 3 hour accumulations.  Therefore there is a Moderate threat issued for the southern Urban Corridor, Palmer Ridge and portions of the Southeast Plains. A Low threat is issued for the majority of eastern Colorado. The Low threat is extended back to the Southeast Mountains to include the recent burn areas (Junkins, Hayden Pass and Spring Creek). Threats for today include heavy rainfall, large hail up to 2 inches diameter, strong wind gusts and a possible tornado.

Riverine:

The NWS Flood Warning continues for Avondale as dam releases at the Pueblo Reservoir are keeping the Arkansas River running at Minor flooding stage.  Minor, low-land flooding is forecast along the river, so the Low flood threat includes this area.  The La Junta gage on the Arkansas will also peak into Action stage this afternoon. Rivers and streams in the high country are running high, but are forecast to continue to decrease today.  However, dam releases are likely to continue, which may cause swollen rivers and minor flooding in downstream areas. Light showers are possible over the Continental Divide today, but are not forecast to increase river flows. Please tune into your local NWS for the latest on Flood Advisories and Warnings, but here are a list of the current Flood Advisories (as of 6:30AM): Los Pinos River below Vallecito Dam, Blue River below Dillon, Gore Creek and the Eagle River near Gypsum, Roaring Fork River and Fry Pan River.

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, Southeast Plains, Palmer Ridge, Urban Corridor:

High levels of surface moisture, moderate diurnal heating and slow steering winds are forecast to produce heavy rainfall over the area. A passing shortwave and low level jet is forecast over the area tonight, which will enhance the chances of heavy precipitation.  Surface convergence along the dryline and Palmer Ridge will provide the forcing for afternoon and evening severe thunderstorms over eastern CO.  These storms will be capable of producing isolated max 2-3 hour rainfall totals up 2.25 inches. Hail up to 2 inch diameter is possible.  A Moderate flood threat is issued over the Palmer Ridge, southern Urban Corridor and western area of the Southeast Plains.  Additional storms capable of producing max 1-hour rainfall rates of 1.25 inches are possible over the Northeast Plains. A Low flood threat is issued over the forecast area.

Primetime: 3PM to 5AM

Front Range, Southeast Mountains, Raton Ridge:

There is a slight chance for precipitation over the Continental Divide and foothills today.  Upslope flow of moist, warm air from the eastern plains will provide a chance for weak thunderstorms mid-afternoon.  Maximum 1-hour rainfall rates of 0.25 inches are possible.  A Low flood threat is issued, which includes the Junkins, Hayden Pass and Spring Creek burn scans.

Primetime: 2PM to 11PM

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

Moderate mid-level moisture will return to the area today as the flow gains more of a westerly component.  Drier air at the surface and weak upper level forcing will keep the chances of precipitation very low today.  Fire danger has decreased from yesterday due to the increase in midlevel moisture and cooler temperatures.  Afternoon cloud cover is forecast over the area this afternoon as upslope flow takes over and combines with upper level moisture.  High temperatures over the high country are once again expected to be in the 70°Fs and 80°Fs, with highs in the 90°Fs over the Grand Valley.

Issue Date: Thursday, July, 4th, 2019
Issue Time: 8:55AM MDT

–A LOW flood threat is issued for the Arkansas River at Avondale

Still quite the dry air mass over the majority of the state as shown by the yellows and orange below. There is some dense fog and a couple light showers over the northeast corner of the state to start the day. A surface low is pulling in some very high dew points into the area behind a weak front, but this should begin to mix out and burn off the fog after a couple hours of heating. The upper trough driving our weather pattern the last couple of days is currently over Nevada, and it will continue to move eastward throughout the day. This will tighten the pressure gradient over the western border and produce gusty southwest surface winds again today. Paired with a very dry air mass, a Red Flag Warning has be issued from noon today to 8PM tonight for the Northwest Slope and Grand Valley. Please use extra caution with any open flames.

As far as rainfall chances, there’s not quite enough moisture over western Colorado today for storms. An isolated weak shower or two may be possible along or near the Continental Divide further south, but other than increased cloud cover over the San Juan Mountains this afternoon, it’s going to be another hot, dry day. To the east, the surface low over the Southeast Plains will continue to pull in low level moisture over the northeast quadrant of the state on its north and east side. There is a very strong moisture gradient from Denver to North Platte, so not surprised about the dense fog reports. However, dry air above the surface will likely mix out a lot of this surface moisture, limiting the chances for afternoon storms.  Downsloping winds over the Southeast Mountains and Raton Ridge should help setup a dryline to the east. Right now this moisture gradient looks to set up over the KS/CO border, so that should keep the rainfall and severe weather threat east of the Southeast Plains. Storm motion to the northeast today will be fairly quick, and with high bases once again on the storms, flooding is not forecast.

Riverine:

The NWS Flood Warning continues for Avondale as dam releases at Pueblo have the Arkansas River running high. Minor flooding is forecast for low lying areas along the river, so a Low flood threat has been issued. While there are still some high flows throughout the state (Eagle, Rio Grande, Los Pinos and Crystal River to name a few), flows from snowmelt are anticipated to decrease today and into this weekend over most areas. However, dam releases are likely, so this may cause swollen rivers and minor flooding on rivers downstream of the releases. Increased chances for rainfall this weekend may also cause some minor flooding issues if storms track over elevated rivers and creeks. Please tune into your local NWS for the latest on Flood Advisories and Warnings, but here are a list of the current Flood Advisories (as of 9AM): Blue River below Dillon, Colorado River at RMNP and downstream of Grand Lake, Roaring Fork River, Fry Pan River, Crystal River near Redstone, Gore Creek and the Eagle River near Gypsum.

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, Front Range, Urban Corridor:

Best chance for measurable rainfall today will be over the Northeast Plains over the counties bordering Nebraska. As weaker storms move off the higher terrains (mountains and Palmer Ridge) this afternoon, they will encounter better moisture over this area as well as a front that will continue to drop south overnight. This will help create more widespread storm activity later tonight with the main threats being moderate rainfall and gusty outflow winds, but some large hail may be possible, too. Max 1-hour rain rates up to 0.85 inches are forecast. Storms back to the west will look a lot like yesterday, so plentiful virga with some light showers mixed in. Max 1-hr rain rates up to 0.25 inches may be possible with most storms producing 0.10 to 0.15 inches in their cores. Should be a great night for fireworks along the Front Range!

Primetime: 3PM to 3AM

Southeast Mountains, Raton Ridge, Southeast Plains, San Luis Valley:

It’s going to be a hot one with the century mark likely being hit over the Southeast Plains. Dry air should keep the rainfall threat at bay with only a few high clouds expected this evening. Surface winds will increase over the San Luis Valley this afternoon, but critical fire weather is not anticipated at this time. With the front passing through overnight, some morning cloud cover will be likely to start Friday morning.

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

The Red Flag Warning is in place over the Northwest Slope and Grand Valley from noon today until this evening when the upper and lower atmosphere uncouple. Winds today will be in the 15-25 mph range from the southwest with gusts up to 35 mph possible. Please use extra caution with open flames and anything that could cause a spark. High temperatures today will be in the 90°Fs over the lower elevations with 80°Fs for the mountain valleys.

Issue Date: Wednesday, July 3, 2019
Issue Time: 10:50 AM MDT

– A LOW flood threat is issued for the Eagle River near Gypsum and the Arkansas River near Avondale

The weather pattern today is very similar to yesterday, but drying of the atmosphere is expected reduce storm coverage this afternoon.  Upper level flow remains out of the west/southwest, with a trough to the west and ridge to the southeast.  The difference from yesterday is that today the flow is advecting only marginal moisture in the midlevels and hot, dry air in the low levels (yellow in the water vapor imagery below). This has reduced the PW values statewide with the sounding at Denver this morning dropping to 0.65 inches. A shortwave and surface low are expected to form in south-central Wyoming this afternoon (marked with “L”), which will cause a statewide southerly and southwesterly wind shift at the surface.  The surface winds will pull in warm and dry air from the south and southwest, which will help increase temperatures by a few degrees from yesterday’s values. Clear skies and downslope flow off of the mountains this morning will heat up and dry out the surrounding plains and low laying areas, which will reduce storm coverage this afternoon.  While surface moisture on the eastern plains this morning is high, this is not expected to last as mixing of this surface moisture to the east will form a dryline (orange line) by early afternoon.  With only minimal residual moisture left over the state, chances for precipitation are lower across the state.  Diurnal flow will initiate some weak thunderstorms and showers along the Continental Divide and eastern foothills, which are anticipated to move over the adjacent plains by 2PM.  With storms today producing gusty winds, outflow boundaries may provide some extra convergence for additional high based storms over the eastern plains.  The main threat from rainfall today will be gusty winds up to 45 mph small hail and moderate rain rates over the eastern plains.  Flooding is not forecast from rainfall.

Riverine:

The riverine flood threat continues today as flows remain elevated across the high country and San Luis Valley from melting, rainfall and dam releases. The Flood Warning continues for Eagle River near Gypsum, which is bankfull at the moment. There was also another dam release at Pueblo Dam, so flows at Avondale will remain elevated throughout the day. The La Junta gage is also forecast to stay at Action stage. A Low flood threat has been issued for La Junta with Minor lowland flooding as the main threat. There are also several Flood Advisories in place with some minor flood reports to accompany them: Frying Pan below Ruedi Reservoir, Roaring Fork near Aspen, Gore Creek at Vail, Eagle River at Red Cliff, Crystal River near Redstone, Los Pinos River in eastern La Plata County, Blue River below Dillon, Colorado River in RMNP and downstream of Grand Lake. The Conejos River in Conejos County is also experiencing very high water with flooding reported in various locations within the area. AHPS gages are also showing the Rio Grande running high, so there is likely some minor flooding in low lying areas for this river as well. On top of that, high country reservoirs are running full, so be prepared for releases from dams throughout the next couple of days, which could cause Minor flooding issues and swollen rivers downstream of the dams. Please tune into your NWS office for the latest on Warnings and Advisories as these will be updated throughout the day. You can also follow some of the flooding here: AHPS gages. While river flows are forecast to decrease into the holiday weekend, fast moving water and bankfull conditions will continue to make banks unstable. Please use extra caution around the high, fast moving water this weekend.

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, Northern Mountains, Urban Corridor, Southeast Mountains, San Juan Mountains, San Luis Valley, Raton Ridge:

Diurnal upslope flow will provide chances for afternoon thunderstorms and showers this afternoon though coverage of storms will decrease. A shortwave passing through Wyoming will provide additional lift to the northern areas of the Front Range and Urban Corridor, so storms will be more numerous over this area. Limited moisture and warm temperatures throughout the area will keep storms high based, with virga and gusty winds (up to 40mph) as the main threat. Max 1-hour rainfall rates up to 0.25 inches are forecast. No flood threat has been forecast in the area today, but high elevation rivers remain near bankfull throughout the area, which will make banks unstable.

Primetime: 12PM to 8PM

Northeast Plains, Palmer Ridge, Southeast Plains:

There is a chance of precipitation this afternoon as storms move off the Palmer Ridge and Front Range Mountains into the adjacent plains. a dryline sets up over the eastern plains, so once storms move to the east of this feature, expect rain rates to increase.. Temperatures will increase rapidly throughout the morning and into the afternoon, with highs jumping back into the 90°Fs over the area. Max 1-hour rain rates of 0.75 inches are forecast for the Northeast Plains and Palmer Ridge. Storms off of the Raton Ridge may drift over the Southeast Plains, but max 1-hour rain rates of only 0.4 inches are forecast along the southern border with most activity dissipating as they move off the higher terrain. The main storm threat again will be wind gusts up to 45 mph and moderate rainfall rates. Due to dam releases and extra runoff from the last couple days of rain, a Low flood threat is issued for lowland areas along the Arkansas River near Avondale.

Primetime: 1PM to 11PM

Southwest Slope, Grand Valley, Northwest Slope, Central Mountains:

Dry, warm air brought in from the southwest will keep chances for precipitation very low today. A weak storm may form along the Continental Divide in the Central and Northern Mountains, but totals should remain under 0.1 inches. Dew points will decrease into the 20°Fs and 30°Fs by midday with temperatures forecast to be in the upper 80F°s over the western slope, 90°Fs in Grand Valley. Temperatures in the high country will get into the 70°Fs and low 80°Fs. Increased surface winds are forecast for the Northwest Slope from the approaching trough, so a Red Flag Warning is in place through 8PM tonight and then again tomorrow. Surface winds are forecast to be in the 20-25 mph range with gusts up to 35 mph. Please use caution with open flames when camping this weekend and any activity that could cause a spark. Lastly, for riverine flooding, snowmelt will continue today. With many streams and rivers running near or above bankfull, Minor lowland flooding is possible. A Low flood threat is issued for the Eagle River near Gypsum in Eagle County, which is under a NWS Flood Warning.