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