Friday, December 13, 2019

Early Winter 2019_High Knob Massif


11 December 2019
Rime And Snow Covered
South Fork Gorge of High Knob Massif
Photograph by Wayne Browning - © All Rights Reserved

History Of Christmases Past (1963-2018)

Morning sunlight illuminated majestic rime and snow coated mountain ridges that stair-step their way downward from Big Cherry Lake basin through rugged, South Fork of Powell River Gorge on December 11.  It was simply gorgeous!


11 December 2019
Rime And Snow Covered
South Fork Gorge of High Knob Massif
Photograph by Wayne Browning - © All Rights Reserved

17 December 2019
Whitewater Gushes In High Knob Massif
Upper Falls of Little Stony Creek Gorge
Photograph by Wayne Browning - © All Rights Reserved

Monthly Total Precipitation
Big Cherry Lake Dam
(Elevation 3139 feet)

January
6.14"

February
12.50"

March
5.93"

April
6.64"

May
6.75"

June
10.68"

July
10.77"

August
4.15"

September
0.63"

October
5.01"
( 5.89" to Midnight 31st )

November
5.20"
( 7.04" to Midnight 30th )

December 1-17
7.85"

Summer 2019
(Jun 1-Aug 31)
25.60"

2019 Total: 82.25" (M)
 (January 1 to December 17 Period)

Total Past 12-Months: 86.73" (M)

(M): Some missing moisture in undercatch and frozen precipitation, with partial corrections applied for the 24.4 meter (80 feet) tall dam structure where rain gauges are located.

17 December 2019
Whitewater Gushes In High Knob Massif
Photograph by Wayne Browning - © All Rights Reserved

Precipitation during 2019 has been abundant with the notable exception of late summer and early autumn when the climax of short-term dryness featured the driest September on record. 

Flood Stage = 6.5 Feet
Stream Levels from January 1 to June 21
*Downward spikes to Zero = Data Loss And Are Not Real

The stream hydrograph for Big Stony Creek exemplifies this 2019 trend, with five different events during the January-June period which reached or exceeded flood stage (above), while only one event was observed between June 21 and December 13 (below). 

Flood Stage = 6.5 Feet
Stream Levels from June 21 to December 13
*Downward spikes to Zero = Data Loss And Are Not Real

17 December 2019
Majestic Whitewater On Little Stony Creek
Photograph by Wayne Browning - © All Rights Reserved

The decline and subsequent refilling of Big Cherry Lake reveals the transition back into wetness, with 9.4 vertical feet of water level rise across the lake being observed between 22 November and 12 December.

Total of 9.4 vertical feet of rise since 22 November

17 December 2019
Clinch River Watershed
Majestic Whitewater In High Knob Massif
Photograph by Wayne Browning - © All Rights Reserved

So, approximately how much water is this
from late November into mid-December?

1 acre foot of water = 325,850 gallons

150 acre feet = 48,877,650 gallons
(Big Cherry contains around 150 acres when including 
additional water being held upstream in wetlands)

9.4 vertical feet of rise x 150 acre feet
= 459,449,910 gallons of water

At 9.4 vertical feet of rise some water 
begins overflowing the lake's spillway


Big Cherry Lake Basin Upstream Of The Dam

1" of rainfall per acre = 27,154 gallons

1" of rain over 3557 acres = 96,586,778 gallons

This suggests 459,449,910 gallons of water
 = 4.76" of rainfall across 3557 acres

The lake holds more than 633,000,000 gallons 
at full pool.

In reality, perhaps 1 Billion gallons of water fell
on Big Cherry Lake basin given that large amounts
do not run off and total precipitation (which includes
snow, and secondary forms of rime deposition and 
drop from trees and fog drip from trees) input into 
the forested watershed of Big Cherry tends to 
exceed output (runoff and evapotranspiration).

17 December 2019
Clinch River Basin of High Knob Massif
Turbulent Whitewater In Little Stony Gorge
Photograph by Wayne Browning - © All Rights Reserved

What about snow?

1" of snow at 10:1 density per acre = 2,715 gallons of water, so when just 1" of snow covers the area above Big Cherry Dam there is 9,657,255 gallons (more than 9.6 million gallons).  This is true only if there is not rime or other moisture sources.

Snow is not a trivial aspect of this high country basin where rime deposition on trees adds greatly to the water content of snow once it drops from forest trees (often increasing the snow density to ratios lower than 10:1, such as 8:1 or 4:1 where just 4-8" of snow may hold 1" or more of water content when factoring in added water contributed by rime and/or fog drip from trees).

11 December 2019
Lower-Middle Elevations  
Majestic Scene Along Maple Gap Road
Photograph by Wayne Browning - © All Rights Reserved

Snow was limited near the base of the massif at the lower end of Powell Valley, but scenes were still beautiful in morning sunlight (above).

A bank of clouds to the northwest, along the flank of Little Stone Mountain (below) of the High Knob Massif, created a dramatic contrast as air sank downward with clearing into Powell Valley.

11 December 2019
NW Flank of High Knob Massif
Cloud Bank Along Little Stone Mountain
Photograph by Wayne Browning - © All Rights Reserved

11 December 2019
Rugged Slopes Above Head of Powell Valley
Photograph by Wayne Browning - © All Rights Reserved

11 December 2019
Powell Valley Overlook
Photograph by Wayne Browning - © All Rights Reserved

11 December 2019
U.S. 23 Near Powell Valley Overlook
Rugged Little Stone Mountain Gap
Photograph by Wayne Browning - © All Rights Reserved

11 December 2019
Robinette Branch In Legion Park
Photograph by Wayne Browning - © All Rights Reserved

11 December 2019
Majestic Morning Light In Legion Park
Photograph by Wayne Browning - © All Rights Reserved

11 December 2019
Mixed-Mesophytic Cold Air Drainage
Photograph by Wayne Browning - © All Rights Reserved

11 December 2019
Morning Light On Freshly Fallen Snow
Photograph by Wayne Browning - © All Rights Reserved

11 December 2019
Canadian Hemlocks (Tsuga canadensis)
Photograph by Wayne Browning - © All Rights Reserved

11 December 2019
Mixed-Mesophytic Forest
Photograph by Wayne Browning - © All Rights Reserved

The beautiful way snow transforms the mountain landscape can be seen from satellites in space, with some incredible images being captured in wake of recent events.

4 December 2019
MODIS Copernicus Landsat Image

An amazing inverted V-shaped cloud, holding stationary along the rims of Powell Valley of the High Knob Massif, was captured in wake of an early December snow event.

At the time of this image (above), just enough breaks in the clouds occurred to see a portion of the massif between its northern and southern bases.  
A few other interesting features are labeled.

11 December 2019
MODIS Copernicus Landsat Image

A sharp northwestern edge, or cut-off (beginning), can be observed on this event which occurred on 
10 December 2019.

11 December 2019
MODIS Copernicus Landsat Image

Once air flow crosses the entire Appalachian range it is common for no more snow to fall, or at least accumulate, downstream of the mountain range.  Local, interior snow shadows also exist along and downstream of the larger mountain barriers.

11 December 2019
MODIS Copernicus Landsat Image

When flowing air possesses a westerly to northerly component then residents living downstream of the High Knob Massif and Tennessee Valley Divide typically have much less snow, or no sticking snow, which often begins prior to reaching the southern and southeastern base of the massif (above).

11 December 2019
MODIS Copernicus Landsat Image

Snow allows both the topography and 
geology of the landscape to be seen.

11 December 2019
MODIS Copernicus Landsat Image

The great Cumberland Overthrust Block, bounded by superficial faults on all sides, is one of the most prominent structures in the Appalachians with its 3125 square mile extent.

Christmas Bird Count 2019

15 December 2019
Rime And Light Snow
Eagle Knob of High Knob Massif

For the second consecutive year clouds engulfed upper elevations, above 3300-3500 feet, during much of the Christmas Bird Count of 2019.

A mix of sleet and snow gave way to a period 
of moderate to heavy snow as air temperatures dropped below freezing into early afternoon 
on 14 December.

Riming continued through sunrise on 15 December
before cloud bases finally lifted off the peaks.

14 December 2019
Clouds Engulfing Upper Elevations
Little Stony Creek Gorge Below Clouds
Approaching Sunset At Bear Rock Overlook
Photograph by Wayne Browning - © All Rights Reserved

Conditions were damp, chilly and cloudy, 
but not as bad below the cloud bases.

14 December 2019
Rugged Gorge of Little Stony Creek
Whitewater ROARING Through The Gorge
Photograph by Wayne Browning - © All Rights Reserved

The ROAR of whitewater could be heard, and locally seen, from Bear Rock as water tumbled downward through Little Stony Creek Gorge 
of the High Knob Massif.

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