FTB 06-26-2019: Weak Afternoon Thunderstorms Anticipated Over the Eastern Plains

Issue Date: Wednesday, June 26th, 2019
Issue Time: 10:05AM MDT

–Flooding is NOT expected today

Flow aloft over the state has turned to the southwest as the trough off the Pacific coast begins to deepen. Currently there is some cloud cover over the mountains and southwest corner of the state associated with some mid-level energy moving through the area. With shallow moisture in place again today, expecting these clouds to burn off after a couple hours of heating. Marked in green below is the dew point gradient. As noted the last couple of days, a very dry air mass remains over western Colorado. With a tightening pressure gradient aloft, surface winds will likely pick up to the 15-20 knot range along the western border today. This will increase fire danger, although critical fire weather is not anticipated until tomorrow. Some light showers may be possible over the southern San Juan Mountains this afternoon as the shortwave (marked in orange below) helps kick off some high-based, weak thunderstorms. The shortwave and diurnal flow will also help initiate some showers and weak thunderstorms over the eastern mountains with the main activity centered over the southern Front Range and Palmer Ridge. As storms move off the mountains into the adjacent plains, only light rainfall is anticipated. Threats also include brief gusty winds, similar to yesterday.

A lee trough is expected to setup over the Northeast Plains and will tighten the dew point gradient (dry line). This will produce some convergence for storm initiation over the eastern plains this afternoon in a north/south oriented line east of Highway 71. Better moisture will be located over Nebraska and Kansas, so the main threat for storms today will again be gusty winds, severe hail and moderate rainfall. Storm activity will move east of the border by early this evening. Therefore, flooding is not expected.

Another day with no riverine flooding expected as well. While a couple gages remain at Action stage, streamflow levels are predicted to decrease statewide. Thus, since no flooding was reported yesterday, there is no riverine flood threat issued today. For the most up to date information on the riverine flooding threat, follow your local NWS Weather Forecast Office.

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

High temperatures will continue to creep up a couple of degrees today with the 5880mb ridge pushing north thanks to warm air advection. Highs over the Southeast Plains will reach just under the 100°F mark. Feeling more like summer! For storms today, max 1-hour rain rates up to 0.15 inches (west) and 0.6 inches (east) will be possible under the stronger storms. Thus, brief gusty winds will also be possible again with Inverted-V soundings. Over the eastern plains, storms will be capable of producing stronger gusts (up to 50 mph), hail up to 1.5 inches and dangerous lightning. These threats should end by the early evening as activity moves east of the state. Flooding is not anticipated.

Primetime: 1PM to 9PM

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

Low dew points and increasing surface winds will escalate fire danger this afternoon. Critical fire weather is not anticipated until tomorrow, but be sure to use caution with any open flame. Surface winds in the 15-20 knot range are anticipated to mix to the surface with gusts between 30 and 35 knots possible by later this afternoon. Winds will then decrease overnight. High temperatures today will be similar to yesterday with an increase in afternoon cloud cover as the shortwave passes overhead. Very light showers may be possible over the southern San Juan Mountains, but the weak storms will likely only produce gusty winds and a drop or two of rain.

Primetime: 2PM to 7PM

FTB 06-25-2019: High-Based Storms for Central Colorado & Rising High Temperatures Statewide

Issue Date: Tuesday, June 25th, 2019
Issue Time: 9:05AM MDT

–Flooding is NOT expected today

The main weather story today will be warmer temperatures with highs expected to be 5-10°F greater than yesterday. Currently, flow aloft is westerly (west) and northwesterly (east). As the ridge begins to build northward over Wyoming today, flow will gradually turn from the southwest statewide. The southwesterly and westerly surface flow this morning is expected to entrain a dry air mass over southern Colorado. This will push the dry line (dashed green in the water vapor imagery below) eastward throughout the day and help mix out the shallow low-level moisture present over eastern Colorado. This should inhibit most of the storm activity over the southern high terrains as dew points to the east of this line are in the 30°Fs.

Approaching from the west is a weak shortwave, which is marked with the orange “X” in the image below. The arrival of this wave during peak heating, should help kick off some weak thunderstorms and high-based showers over the central mountains and Palmer Ridge areas. PW values at DIA this morning were measured at 0.52 inches. Storm activity is forecast to spread into the adjacent, eastern plains by mid-afternoon. However, storms today will produce little, if any, rainfall accumulations due to the aridness of the atmosphere and quick storm motion. The main threat with storms today will be gusty outflow winds (up to 55mph) and lightning. A little better moisture will be able to hang on over the northeast corner of the state, so if storms that form over the Cheyenne Ridge track into the area, expect some light accumulation. Flooding is not forecast today.

The riverine flood threat has ceased for the moment with river levels forecast to drop statewide or remain below Action stage. The one exception is along the Arkansas River at La Junta. High water from Avondale will continue to traverse east and may cause the AHPS gage to briefly reach Minor flooding stage. This is not expected to last long, so no flood threat has been issued. For the most up to date information on the riverine flooding threat, follow your local NWS Weather Forecast Office.

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, Southeast Mountains, Raton Ridge, Urban Corridor, Northeast Plains, Palmer Ridge, Southeast Plains, Central Mountains:

High temperatures today over the eastern plains could reach the mid 90°Fs with 80°Fs along the Urban Corridor. Most mountainous regions should reach the upper 60°Fs to low 70°Fs. Storms today will be capable of producing 1-hour totals up to 0.1 inches (east) and 0.35 inches (northwest corner). However, the majority of storms will produce only trace amounts with strong outflow winds. Light overnight showers may be possible over the Southeast Plains, but flooding is not anticipated. Lastly, expect a crest at the La Junta gage along the lower Arkansas River, which may briefly push the gage into Minor flooding.

Primetime: 1PM to 11PM

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

Another day with very low dew points. Thankfully surface winds should be rather light, so not anticipating any critical fire weather. Cloud cover is anticipated this afternoon over the high terrains as the shortwave pushes east, but rainfall accumulation above 0.05 inches is not forecast. At this time, there is no riverine flooding anticipated although the Rio Grande gage at Alamosa and North Platte River gage at Northgate are in Action stage.

Primetime: 1PM to 9PM

FTB 06-24-2019: High Temperatures Rebound with Isolated Storms Forecast for this Afternoon

Issue Date: Monday, June 24th, 2019
Issue Time: 9:00AM MDT

–A LOW flood threat is issued for Saguache Creek, the headwaters of the and along the Rio Grande in Mineral and west Rio Grande Counties and for the San Antonio, Conejos Rivers in south central Colorado, Arkansas River downstream of Pueblo Dam to Nepesta and rivers/streams in central Jackson County.

The main axis of the trough has passed to the east, which will place the state under northwesterly/westerly flow aloft today as the ridge slides in from the west and begins to build over the state the next couple of days. Rising pressure with only minimal residual moisture remaining under the ridge (PW was measured at 0.43 inches at Denver) will keep the rainfall today limited to high-based showers and weak thunderstorms favoring the Northern Mountains, eastern San Juan Mountains and southern Front Range/Palmer Ridge intersect for development this afternoon. A couple additional weak storms may be possible over the far Northeast Plains late this afternoon, but should not become severe. Storms are anticipated to dissipate as they move off the mountains with the northwest steering flow. All storm activity is forecast to come to an end a couple hours after sundown as instability declines. As anticipated, flooding from rainfall is not forecast.

The riverine Low flood threat continues for various stretches of river across the state and are marked in the flood threat map below. Saguache Creek, the headwaters of the and along the Rio Grande in Mineral and west Rio Grande Counties and the San Antonio/Conejos Rivers in south central Colorado have a Flood Warning issued through this afternoon. Minor flooding has also been reported, with some rural roads being washed out, in central Jackson County due to snowmelt and heavy rainfall the last couple of days. This Flood Warning continues through 1PM this afternoon with river levels expected to decrease over the next day or two. Lastly, a Low flood threat has been issued for the Arkansas downstream of Pueblo Dam to Nepesta. The AHPS gage in Avondale is in the Minor flooding stage and is expected to remain elevated (at the current level) through today. For the most current updates and the latest information, follow your local NWS WFO (Weather Forecast Office).

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.

Flood Threat Legend

 

Zone-Specific Forecasts:

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

Much warmer temperatures today with the eastern plains reaching the 80°Fs. Most mountainous regions should reach the 60°Fs, so much warmer temperatures overall.  Isolated max 1-hour rain rates up to 0.2 inches will be possible, but the majority of storms will produce under 0.15 inches or only trace amounts. Flooding is not anticipated except over the lower Arkansas from Pueblo Dam to Nepesta.

Primetime: 1PM to 10PM

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

Very low dew points over these regions and building high pressure, should keep the afternoon storm activity limited. Some high-based showers and a weak thunderstorm or two may be possible over the Northern and eastern San Juan Mountains. Max 1-hour rain rates up to 0.3 inches are possible though most storms will produce under 0.15 inches and plentiful virga. See the riverine section above for the latest on flooding, and also visit your local NWS office for the most recent updates.

Primetime: 2PM to 10PM

FTB 06-23-2019: Upper-Level Low Departing Today

Issue Date: 6/23/2019
Issue Time: 8:15 AM

A LOW FLOOD THREAT IS FORECAST TODAY FOR THE FOLLOWING AREAS:

Saguache Creek, the headwaters of the and along the Rio Grande in Mineral and west Rio Grande Counties, the San Antonio and Conejos Rivers in south central Colorado, and the North Platte River near Northgate.

NOTE: Elevated snow melt runoff continues across the High Country, with various flood advisories issued. Please visit the website of your local National Weather Service Office for more details.

The upper-level low that has brought unsettled weather to Colorado the past couple of days is finally departing the region and will be centered over South Dakota/Nebraska by tonight. Before it leaves, though, it will bring another day of below average temperatures and isolated-to-scattered showers/thunderstorms. With cooler temperatures in place, storms will not have the same “oomph” they have had the past few days, with the vast majority of them being garden-variety. Near the CO/KS border, an isolated severe storm or two cannot be ruled out, with the potential to produce half-dollar-sized hail and gusty winds up to 65 mph.

The best coverage of storms today will be north of Highway 50, due to proximity to the low-pressure center aloft and good mid-level moisture. South of Highway 50, drier air and less support aloft will keep a fairly tight lid on things with only a few isolated showers over the mountains and a couple isolated showers/storms east of the mountains. Storm motions will be quick enough, and rain rates low enough, to avoid the issuance of any rainfall-induced flood threats. The only flood threats on the map today are due to ongoing snowmelt.

For more details on timing and rain rates, please see the zone-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.

Flood Threat Legend

Zone-Specific Forecasts

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

Isolated showers are ongoing north of I-70 this morning. By lunchtime, additional isolated-to-scattered showers/thunderstorms will develop, mainly north of Highway 50, and continue into the late-afternoon hours. Shower/storm activity will diminish by 6 PM, with all activity ending by 9 PM or so. One or two storms near the CO/KS border may become strong/severe, with the potential to produce half-dollar-sized hail, strong winds up to 65 mph, and heavy rain at 1.0-1.5 inches/hour. Otherwise, all of the activity is expected to be garden-variety, producing moderate rainfall and gusty winds with rain rates of 0.3-0.6 inches/hour.

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

Isolated-to-scattered rain and snow showers are expected, with snowfall above 9,000 feet and rain below. Showers will be brief, moving quickly towards the southeast, with rain rates less than 0.25 inches/hour. Activity will end from west to east this evening, with all activity ending by 8-9 PM.

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

A couple isolated showers, mainly over the higher terrain, are expected. Otherwise, the rest of the area will remain dry under mostly sunny skies. Rain rates from any showers will be less than 0.2 inches/hour.

Timing: 2 PM – 7 PM