FTB 06-22-2019: Cool and Wet, High Elevation Snow

Issue Date: 6/22/2019
Issue Time: 8:20 AM

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

Portions of the Front Range, Southeast Mountains, Urban Corridor, Northeast Plains, Southeast Plains, and Raton Ridge regions.

Saguache Creek, the headwaters of the and along the Rio Grande in Mineral and west Rio Grande Counties, and for the San Antonio and Conejos Rivers in south central Colorado.

NOTE: Elevated snow melt runoff continues across the High Country, with various flood advisories issued across the Northern Mountains, Northwest slope, Central Mountains, Southwest Slope, and Grand Valley. Please visit the website of your local National Weather Service Office for more details.

No one told Mother Nature that it is the second day of summer, and the image below depicts a weather pattern more reminiscent of late-September/October than late-June. An upper-level low is currently centered over southern Saskatchewan, with the trough axis extending southwest towards the California Baja. Associated with this system is plenty of upper-level support for showers and embedded thunderstorms, which has kept rainfall (and high elevation snow) ongoing this morning across the Front Range, Central Mountains, Urban Corridor, Palmer Ridge, and Northeast Plains. The unsettled weather will expand in coverage and intensity this afternoon and evening as temperatures warm a bit and increase instability. Ample shear will also be in place thanks to strong southwest flow aloft, so there will be a few embedded strong-to-severe thunderstorms. The greatest severe threat will be east of the mountains, where the combination of shear/instability will be best. These stronger storms will also hold the potential for heavy rainfall, thus the issuance of the low flood threat.

Over the High Country and Western Slope, widespread showers and thunderstorms are expected, with the main impacts being light-to-moderate precipitation, gusty winds, and small hail. A couple stronger thunderstorms cannot be ruled out, which may produce hail up to 1 inch in diameter and strong winds up to 65 mph. Accumulating snow is expected above 9,000-10,000 feet in the Grand Valley, Northwest Slope, Northern Mountains, Central Mountains, and Front Range regions, with higher peaks picking up 6-10 inches of snowfall through tomorrow morning.

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

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

Scattered-to-widespread showers and thunderstorms expected today/tonight, with lingering showers into the morning hours tomorrow. A few of the storms will be strong/severe, with the potential to produce hail up to 2 inches in diameter, strong winds up to 75 mph, and a brief tornado or two. Rain rates will generally be below flash flood thresholds, but stronger storms could produce the following maximum rain rates:

Front Range and Southeast Mountains: 0.5-1.0 inches/hour
Urban Corridor: 1.0-1.5 inches/hour
Palmer Ridge, Northeast Plains, and Southeast Plains: 2.0-2.5 inches/hour
Raton Ridge: 1.5-2.0 inches/hour

Storm motions will be at a decent clip towards the east, so only a low flood threat is warranted. The Junkins, Beulah Hill, Spring Creek, and Hayden Pass burn scars may need a watchful eye.

Timing: 10 AM – Midnight for the Front Range and Southeast Mountains (a few lingering showers into tomorrow morning), 1 PM – 1 AM for the Urban Corridor, Raton Ridge, and Palmer Ridge, 2 PM – 2 AM for the Northeast Plains and Southeast Plains (a few thunderstorms lingering until sunrise tomorrow)

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

Scattered-to-widespread showers and thunderstorms expected throughout today and tonight. The bulk of the activity will end by 9-10 PM, but a few isolated showers/thunderstorms will continue into the morning hours tomorrow, mainly north of I-70. Snow accumulation is expected above 9,000-10,000 feet. Most rain rates will be less than 0.2 inches/hour, but a stronger thunderstorm may produce rainfall at 0.2-0.4 inches/hour.

FTB 06-21-2019: Heavy Rain and Severe Weather Forecast over the Palmer Ridge

Issue Date: Friday, June 21st, 2019
Issue Time: 9:45AM MDT

–A LOW flood threat is issued for Palmer Ridge and portions of the Urban Corridor, Northeast Plains and Southeast Plains.

–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 and Conejos Rivers in south central Colorado.

It’s officially the first day of summer, but expecting some colder, more spring like temperatures to move into the state with the next system. Marked in the visible satellite imagery below is the cold front in blue. Over western Colorado, it is more stationary at this point in time. This feature is expected to begin its push south early this evening and overnight, so it will be a cool, cloudy and potentially wet start to Saturday morning over eastern Colorado. Less cloud cover and just cooler temperatures are forecast for the western slope tomorrow morning. The jet axis has moved into the northwest corner of the state with a southwest to northeast orientation. Thus, expecting quick, southwest flow over the state again today, especially to the west. The last impressive feature on the surface maps this morning (not shown) is the really strong dew point gradient over southeastern Colorado. Dew points are in the mid to upper 50°Fs over the far Southeast Plains, but back to the west at Trinidad, the dew point drops to 24°F. Southwest winds aloft will advect the drier air mass over New Mexico into the Southeast Plains this afternoon, so expect the dew points to begin to drop by noon. This should really keep the severe weather and rainfall threat limited to along and north of the Palmer Ridge this afternoon over eastern Colorado.

Ongoing showers over the northwest corner associated with the jet are expected to continue throughout the day and follow the jets movement. Therefore, expecting more storm activity early this evening further south over the Grand Valley, Southwest Slope and Central Mountains. As the axis of the trough moves eastward overnight, showers will diminish west to east with the axis shift. Colder temperatures behind the front will bring snow to higher elevations (above 9,000 feet). Continuous precipitation with this feature will promote some high 24-hour totals over the Northern Mountains and northern Front Range. However, rainfall should be gradual enough that flooding will be avoided.

Back to the east, a shortwave will arrive around peak heating this afternoon helping form numerous and widespread thunderstorm activity over the eastern Front Range, Urban Corridor and Northeast Plains. The best parameters for a large severe thunderstorm of two will be along the Palmer Ridge. Golf ball sized hail, wind gusts greater than 60 mph and a couple tornadoes will be possible with these severe thunderstorms. Heaviest rainfall is expected to fall along the west to east oriented front due to westerly steering winds in the area around 10 mph. A Low flood threat has been issued for this area with the main threats being street and small stream flooding along with lowland flooding.

The riverine Low flood threat continues 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 through Monday. Minor flooding continues to be reported by local emergency management over these areas. Elevated flows continue over the upper Arkansas River, but flooding is not anticipated unless there are some large releases from Pueblo Dam. Keep up to date with the release by following the NWS office in Pueblo. With cooler temperatures forecast going into this weekend, flow are forecast to begin to decrease. This should start to push gages below Action stage early next week.

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

Ongoing rainfall will continue today with the jet overhead and a stationary front in the area. Storms will increase to the south during the early evening hours as the jet begins to sag south. Max 2 to 3-hr rain totals up to 0.7 inches are possible over the Northern Mountains and Front Range with 0.5 inches elsewhere. 1-hour rain rates around 0.25 inches should keep the flooding issues at bay, but there may be increased runoff near the Lake Christine burn area. Isolated 24-hour totals up to 1.5 inches may be possible over the north central mountains with 4 to 10 inches of snow above 10K feet by Sunday morning along and near the Continental Divide.

Primetime: Ongoing to 9AM

Urban Corridor, Northeast Plains, Palmer Ridge:

Heaviest rainfall is expected to occur along the front today, which will rest across the Palmer Ridge. However, with the shortwave moving through, thunderstorm activity will be widespread across these regions. Max 1-hr rain rates up to 1.25 inches will be possible over the western portion of the threat with rates increasing to 1.5 inches over the eastern portion of the threat. Road and small stream flooding along with flooding of low laying areas will be possible. A severe storm or two over the Palmer Ridge will be capable of producing golf ball sized hail, severe wind gusts and a tornado or two. Further north and along the Urban Corridor, max 1-hr rain rates could reach 0.5 inches.

Primetime: 2PM to 10PM

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

Drier air will preside over these regions with southwest flow pulling in a dry air mass from Arizona and New Mexico. Dew points are forecast to be 20°F and lower. This will keep these regions mostly cloud free with a slight increase in cloud cover this afternoon over the San Juan Mountains. Temperatures over the eastern plains will be in the 90°Fs with 80°Fs in the mountain valleys. The cold front will move through overnight, so expect overnight temperatures to reach 50°F over the plains and 40°Fs in the valleys.

FTB 06-20-2019: Storms Forecast to Return to Northern Colorado as the Jet Sags South into Nevada

Issue Date: Thursday, June 20th, 2019
Issue Time: 9:20AM 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 and Conejos Rivers in south central Colorado.

Taking a look at the water vapor imagery below, a relatively dry air mass remains over Colorado as indicated by the shades of yellow. The next system, currently over the Pacific Northwest, will begin to drop south today with the back of the jet sagging into Nevada. This will turn flow aloft from westerly to more southwesterly by this afternoon. As this transition occurs, winds will advect the drier air mass over AZ and NM into the southern half of Colorado, which should limit rainfall chances over this area. A couple light showers may form over the high terrains, but only trace amounts are forecast. Over northwest Colorado, a cold front will move through early this afternoon and help kick off thunderstorm activity. Expect trailing storms over the Northwest Slope and Northern Mountains this afternoon. Overnight rainfall is also anticipated over this area with favorable dynamics remaining over the region, so decent accumulations will be likely by tomorrow morning.

To the east, upslope flow will set off storms over the Front Range around 1PM. Additional convergence along the Palmer Ridge, due to a surface trough, will initiate some weak thunderstorms over this area as well. Expect the high-based storms to move west and then northwest with the flow aloft. Limited low-level moisture and fast steering winds will likely only produce moderate rainfall totals, so flooding is not anticipated. Over the Southeast Mountains, downsloping winds on the southwest side of the surface trough will keep rainfall limited to along and near the Continental Divide.

The Low flood threat continues 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. Minor flooding continues to be reported by local emergency management over these areas. Elevated flows continue over the upper Arkansas River, but flows are forecast to decrease east of Pueblo Dam. No AHPS gages are not forecast to rise above Action stage today.

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, Palmer Ridge, Urban Corridor, Northeast Plains, Northern Mountains, Northwest Slope, Grand Valley, Central Mountains:

Thunderstorms are forecast to be high-based this afternoon, which should limit the rainfall reaching the surface. Gusty winds may be possible along with small hail and dangerous cloud to ground lightning under the stronger storms. Highest rainfall accumulations for the day are anticipated over the northwest corner due to trailing storms and over the far Northeast Plains where better moisture remains intact. Storms over eastern Colorado should end by midnight. Flooding is not forecast, and max 1-hr rain rates are as follows:

Northwest Slope/Northern Mountains: 0.3 inches with 24-hour totals up to 0.8 inches over the Northern Mountains
Central Mountains/Front Range/Palmer Ridge: 0.1 inches
Northeast Plains: 0.5 inches

Primetime: 12PM to 9AM

San Juan Mountains, Southwest Slope, San Luis Valley, Southeast Plains, Southeast Mountains, Raton Ridge:

Best chance for rainfall today will be over San Juan Mountains and Southeast Mountains near the Divide. With dew points dropping off to below 30°F, more cloud cover is anticipated than rainfall. However, a couple storms may produce a sprinkle or two. Skies will begin to clear overnight as the southwest winds pull in a very dry air mass from Arizona and New Mexico. High temperatures similar to yesterday will continue to melt the snowpack, so rivers will remain elevated again this afternoon. Flows are anticipated to drop off over the Arkansas, so the flood threat has been removed. Please follow your local NWS office for the latest on the riverine flooding threat over your area.

Primetime: 1PM to 7PM

FTB 06-19-2019: Northwesterly Flow Ushers in Dry Air and Diminishes the Heavy Rainfall Threat

Issue Date: Wednesday, June 19th, 2019
Issue Time: 9:15AM MDT

–A LOW flood threat is issued for the Arkansas River downstream of Pueblo Dam to La Junta, Saguache Creek, the Rio Grande in Mineral and west Rio Grande Counties and for the San Antonio and Conejos Rivers in south central Colorado.

Today, Colorado sits between two systems, which will give us a break from widespread, heavy rainfall. Overnight into this morning, flow aloft has been turning from westerly to northwesterly, which is expected to continue as the trough exits to the east. This has pulled in a drier air mass over the state (yellow below) and will continue to push the higher moisture to the east throughout the day. PW values at DIA were measured at 0.65 inches, which is a decrease of 0.25 inches from yesterday morning. Enough residual moisture will remain present for some afternoon storms over the mountains and eastern plains, but storms are expected to be more scattered in nature. The bulk of the storm activity today is forecast over the northern Urban Corridor and Northeast Plains thanks to a passing shortwave, an upper level jet moving into northern Colorado and initiation of storms along the Cheyenne Ridge and northern Front Range. With storm motion to the southeast at ~25 mph and dew points in the upper 40°Fs, heavy rainfall is not forecast. Lower dew points over the mountains should limit storm activity to the near and along the Continental Divide with a couple weak showers possible over the Southeast Mountains and adjacent plains. Brief gusty winds will be likely with storms today due to the high bases and inverted-V soundings. With the right exit region of the jet moving into northern Colorado by early this evening (sinking motion), storms should come to an end a couple hours after sundown. As anticipated, flooding is not forecast due to rainfall.

Flows continue to remain high over the same portions of river as the previous few days. Elevated flows continue for another day along the downstream of Pueblo Dam due to snowmelt, dam releases and rainfall, so the Arkansas from Pueblo to La Junta is under a Low flood threat for possible minor lowland flooding. The Low threat has also been re-issued for central Saguache County, the headwaters of the Rio Grande and Conejos County in south central Colorado. Minor flooding reports continue to be relayed to the NWS offices from emergency management. Gages are not forecast to rise above Action stage today.

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

High temperatures will also increase with a ridge sliding in from the north overhead. Expect temperatures to increase 7-10°F from yesterday afternoon. With storm motion from the northwest, storms that form over the mountains will likely move into the adjacent plains. Max 1-hr rain rates up to 0.2 inches (south) and 0.1 inches (north) are possible with these storms. Over the eastern plains, higher moisture will increase the efficiency of the rain rates. Max 1-hr totals of 0.4 inches are possible, which means there is no flood threat from rainfall today.

Primetime: 1PM to 9:30PM

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

Best chance for rainfall today will be over the northwest facing slopes of the high terrain. With a much drier air mass in place over western Colorado, expect rainfall totals to drop off drastically from the last two days. Isolated max 1-hr rain rates up to 0.1 inches are possible though most storms will only produce cloud cover and maybe some brief gusty winds. High temperatures will be slightly higher than yesterday, so be sure to get out and enjoy the beautiful weather. The Flood Warning for central Saguache County continues as well as for the headwaters of the Rio Grande and San Antonio/Conejos Rivers. Due to recent reports of minor flooding by emergency management, these areas have been given a Low flood threat. Please follow your local NWS office for the latest on riverine flooding threat over your area.

Primetime: 3PM to 8PM