FTB 07-08-2019: Heavy Rainfall Forecast for the Northeast Plains

Issue Date: Monday, July, 8th, 2019
Issue Time: 9:10AM MDT

–A LOW flood threat is issued for the Northeast Plains and portions of the Raton Ridge and Southeast Plains

The water vapor imagery below is very active out in front of the upper trough, which is forecast to begin  to move east throughout the day. This will increase southwest and then westerly flow over the state this afternoon into the overnight hours. Over the southwest corner of the state, dry air will begin to be advected into the area, which should keep storm activity more isolated over western Colorado this afternoon. This will limit the higher accumulations to along and near the Continental Divide. Over eastern Colorado, southeasterly winds at the surface will hold moisture in place over the eastern plains. A low over the Southeast Plains will cause downsloping winds at the surface over the Southeast Mountains, so this should mix out moisture over the immediate adjacent plains. ENE movement of the storms at 15-20 knots paired with limited moisture over the mountains and immediate adjacent plains should limit the flood threat over these regions. As far as coverage, with strong lift out in front of the trough, storms this afternoon are expected to be more widespread than the last couple of days.

With dew points in the 60°Fs over the Northeast Plains, slower steering winds and trailing storms possible, heavy rainfall is forecast beginning later this afternoon and last through this evening. Building instability over the area, as clouds begin to break up, will likely cause storms to intensify as they move into the area. Some severe storms are forecast thanks to weak shear from southeasterly surface winds. The main threats from the storms will be brief, strong winds, hail up to 1.75 inches, field ponding and flooding of low lying roadways. A Low flood threat has been issued.

Riverine:

As of 9AM this morning there are no NWS Flood Warnings. However there are Flood Advisories for the Blue River below Dillion and for the Roaring Fork River near Aspen from recent dam releases and decreasing water diversions. Minor lowland flooding can be expected over these areas through at least the middle of the week. Warm temperatures in the forecast will also add some more runoff from snowmelt. As far as AHPS gages in Action Stage, the Rio Grande continues to remain elevated, although flows are forecast to decrease the next couple of days across the SLV. The Avondale and La Junta gages along the Arkansas River are also at Action stage, so Minor lowland flooding will be possible. There have been some rises along the South Platte River thanks to recent rainfall over the Northeast Plains, but flooding is not anticipated along the river. Please follow your local NWS office as they will update flood products 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.

Flood Threat Legend

 

Zone-Specific Forecasts:

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

Storms this afternoon will favor the Front Range, Palmer Ridge and Raton Ridge for initiation from upslope flow. Drier air and swift steering winds over the Southeast Mountains should keep burn areas safe from flooding issues this afternoon. Over the mountains and adjacent plains, max 1-hour rain rates up to 0.45 inches will be possible. Moving east to the Northeast Plains and eastern Palmer Ridge, max 1-hour rain rates up to 1.75 inches will be possible due to higher moisture, slower steering winds and trailing storms. Isolated storm totals up to 2 inches may be possible. Storms that form over the Raton Ridge and move into the southeast corner counties could produce 1-hour rain rates up to 1 inch. A Low flood threat has been issued with the flood threats being localized flash flooding, field ponding and flooding over low lying roads.

Primetime: 1:30PM to 10PM

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

Southwesterly flow is forecast to increase today and turn more westerly into tonight. Surface winds will increase this afternoon as well (southwest) with the approaching trough tightening the pressure gradient. This will begin to pull a drier air mass into the state and decrease PW values. There will be enough residual moisture today for another round of storms over the mountains, but with more isolated coverage. Highest accumulations will be along and near the Divide. Max 1-hr rain rates up to 0.2 inches will be possible over this area. Storms will likely produce gusty outflow winds, so brief gusts in the in the 40 to 50 mph will be likely again today.

Primetime: 1PM to 8:30PM