Reference Late-Winter 2021_High Knob Massif as well as Mid-Winter 2021_High Knob Massif for a recap of recent conditions, and a 2020-2021 precipitation update.

Update At 9:30 PM on 1 March 2021

Caution For High Water Levels Continues Into Tuesday For Creeks And Mainstem Rivers

Main stem rivers in Dickenson and Buchanan counties crested below flood stage, but many tributaries creeks reached near to or exceeded flood stage, as did creeks draining the High Knob Massif into Wise, Scott, and Lee counties of the Upper Tennessee Basin.

Orographically enhanced rainfall totals in upper elevations of the High Knob Massif pushed the Clinch River into minor flood downstream of its tributaries (*).

*Orographically enhanced rains via upslope flow and the seeder-feeder mechanism are often not well detected by Doppler radar given much of this enhancement occurs in supersaturated air beneath and just above the summit levels which Doppler beams overshoot (therefore, totals are locally well above regional totals observed within adjacent lowlands).

This can led to river stage predictions which are below what is actually observed, as in this event where initial hydrologic forecasts were for the Clinch River to remain below Action Stage.

Update At 5:30 AM_Monday_1 March 2021

Numerous roadways have become impassible across Wise, Dickenson, and Buchanan counties due to flooding.

Storm rainfall totals of 3.00″ to 5.00″+ have become widespread. All streams are running high or flooding.

Widespread ponding of water in low-lying areas will otherwise generate hazardous travel conditions through this morning. If you do not need to travel, please remain at home.

Flood Potential Increasing

Heavy To Excessive Rainfall Will Continue High Water Levels And Increase The Flash Flood And Flood Risk From Sunday Into Monday Morning

Widespread 1.50″ to 2.50″ of rain have been observed across the mountain area, with strong rises on streams and ponding of water in low-lying, flood prone locations as of early Saturday afternoon (27 February).

*A total of 2.83″ of rain had been observed on Eagle Knob of the High Knob Massif as of 6:30 PM Saturday (27 February), with local totals also near 3.00″ along portions of Pine Mountain that drain into northern Wise and Dickenson counties (Letcher-Pike counties in SE Kentucky).

Embedded convective rains (downpours) are a major concern along with backbuilding and training of heavy rain repeatedly along the same corridors.

An additional wave of rain into Sunday morning will be followed by the heaviest wave expected to develop Sunday night into Monday morning on an already super-saturated to flooded landscape.

Life-threatening Flash Flooding Can Quickly Develop Under Saturated Conditions. Please Remain Alert.

Additional model rainfall totals into Monday morning all show notable mesoscale banding, but are variable in its positioning. Locations within bands will tend to have the highest flood risk over ground already saturated.

Previous Discussion

The first of multiple waves of rain will begin impacting the mountain region Friday, with a heavy to excessive rainfall potential this weekend into early next week.

A strengthening 850 MB low-level jet will be the initial forcing for heavy rainfall this weekend, with orographic enhancement expected from headwaters of the Upper Tennessee, Cumberland, Kentucky, and Big Sandy river basins toward the west-southwest.

Axes of heaviest rainfall are variable in modeling, but climatology of past similar events favors the greatest rain totals to be along and west to southwest of the western Appalachians.

A WSW-SW upper-level flow is climatologically favored for heaviest rainfall amounts to occur (as documented in the past) along and west of the western side of the Appalachians.

Those living and driving along streams, rivers, and within low-lying, typically flood prone locations will need to remain alert for water level rises.

Previous Discussion

From a hydrology perspective, snow cover and high mountain snowpack has now retreated north of the southern Appalachians.

Although some snow or frozen could fall with the first wave in this upcoming pattern by later Friday at high elevations, run-off from snow is not expected to be a factor in the flood potential ahead.

Despite what GRACE may indicate, soil moisture is high across the area and a limited amount of rainfall will be needed to reach saturation, such that additional rainfall contributes to run-off.

Stay tuned for updates.