Tuesday, February 2, 2021

Late Winter 2021_High Knob Massif


02 February 2021 at 3:58 PM
Eagle Knob of High Knob Massif
Wind Blown Snow-Rime & Deep Snow  
Cody Blankenbecler Image © All Rights Reserved

A prolonged Miller B type winter storm system produced nearly all precipitation types across 
far southwestern Virginia, to include snow, 
sleet, freezing rain, and rain.

Snow-free Reference Image
Eagle Knob of High Knob Massif
Cody Blankenbecler Image © All Rights Reserved

Nearly all snow fell at upper elevations across the High Knob Massif, where storm snowfall totals were a foot or more above 3000 feet.

Miller B Winter Storm

3 to 4-Day Snowfall Totals
(30 January-02 February)

Big Stone Gap: 2.0"
(Chris Allgyer)

Elevation 1566 feet
Clintwood 1 W: 4.0"
(0.68" storm water total)

Elevation 2650 feet
Nora 4 SSE: 4.7"
(Wayne & Genevie Riner)

Elevation 2365 feet
City of Norton WP: 5.6"
(0.95" storm water total)

Elevation 3300 feet
High Chaparral: 13.0"
(Joe & Darlene Fields)

Elevation 4200 feet
High Knob-Eagle Knob: 15.0"
(6" to 24"+ depths)

02 February 2021 at 4:53 PM
Eagle Knob of High Knob Massif
Blowing Snow-Rime (16 degrees)
Cody Blankenbecler Image © All Rights Reserved


High Knob Massif
Precipitation Update

(Totals Listed By AM Measurement Format)
Monthly Total Precipitation
Big Cherry Lake Dam
(Elevation 3139 feet)

2019

January
6.14"

February
12.50"

Winter 2018-19
(1 Dec-29 Feb)
26.56"

March
5.93"

April
6.64"

May
6.75"

Spring 2019
(1 Mar-31 May)
19.32"

June
10.68"

July
10.77"

August
4.15"

Summer 2019
(1 Jun-31 Aug)
25.60"

September
0.63"

October
5.01"
( 5.89" to Midnight 31st )

November
5.20"
( 7.04" to Midnight 30th )

Autumn 2019
(1 Sep-31 Oct)
10.84"

December
8.52"

2019 Total: 82.92" (M)
 (January 1 to December 31 Period)

2020

*January
7.15"

**February
13.01"

Winter 2019-20
(1 Dec-29 Feb)
28.68"

March
9.55"
( 10.77" to Midnight 31st )

April
11.59"

May
8.73"
(6.90" on Eagle Knob of High Knob Massif)

Spring 2020
(1 Mar-31 May)
29.87"

June
7.48"

July
9.72"
(10.48" to Midnight 31st)

August
8.12"

Summer 2020
(1 Jun-31 Aug)
25.32"

September
6.21"

October 
7.06"

November 
1.96"
(Eagle Knob Snowfall: 0.5")

Autumn 2020
(1 Sep-31 Oct)
15.23"

December 
6.22"
(Eagle Knob Snowfall: 34.0")

2020 Total: 96.80" (M)
 (January 1 to December 31 Period)

2021

January
6.35"
***(Eagle Knob Snowfall: 34.0")

November 2019-October 2020: 102.34"

Autumn 2018 to Summer 2019: 91.21"

Autumn 2019 to Summer 2020: 94.44"

(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.  Corrections are based upon 86-months of direct comparisons between NWS and IFLOWS at Big Cherry Dam (including occasional snow core-water content data).

*General 7.00" to 8.00" at upper elevations (above 3000 feet) with 5.96" at the City of Norton Water Plant (official NWS rain gauge located at approximately 2342 feet elevation).

**Third consecutive February to reach double-digit precipitation totals within upper elevations of the 
High Knob Massif.

***Not a mistake, with a second consecutive month having 34.0" of snowfall (rare to have back-to-back months with the same total).


Orographic Impacts

As with most big events, very interesting orographic effects could be seen as the high mountains interacted with the overlying atmosphere.

0451 UTC on 2 February 2021
Orographic Cloud Streamers

Majestic lenticular mountain waves were observed above the High Knob Massif as a low-level cloud deck broke prior to sunset on 02 February 2021.

Images courtesy of the Computer Science-Mathematics Department at University Of Virginia's College At Wise
















Majestic Views From Space

A mixture of snow cover and clouds were 
visible following sunrise on 3 February 2021.

GOES 16-Visible Image
3 February 2021 at 9:16 AM

Observe the highly exposed High Knob Massif and 
the notable snow shadow along its lower slopes and adjoining Clinch River Valley immediately in the 
wake zone with respect to this event.

GOES 16-Visible Image
3 February 2021 at 9:16 AM

Overlay images by flipping back-and-forth.


Overlay images by flipping back-and-forth.


High-resolution images revealed a beautiful, snow-covered mountain landscape with the exception of downslope snow shadows (inside the mountains) 
which saw very little accumulation.

3 February 2021
Snow-Covered Southern Appalachians
Copernicus-Landsat Image

Around 90% of total Great Lake water remains free of ice, which will be important as arctic air plays a bigger role in eastern USA weather during the next few weeks.

3 February 2021
Great Lakes Region
Copernicus-Landsat Image


High-Country Ice Storm
4-5 February 2021

5 February 2021 at 8:01 AM
Eagle Knob of High Knob Massif
Wake Of High-Country Ice Storm
Cody Blankenbecler Image © All Rights Reserved

Depressions observed in top of the snow above are from falling rime
in wind gusts that reached 40-50+ mph.  No wind advisory was issued.

Initial snow (with large flakes) and sleet changed into freezing rain at elevations above 3000 feet across the High Knob Massif during the evening hours of 4 February 2021.

A few of the impacted roads included:
State Route 619, State Route 699, State Route 706, State Route 722, Route 237, Route 238, Route 239, Route 704, and Route 822 .

A few impacted communities (where people live):
Black Hill, Cox Place (Johnson Pasture), East Moore Knob, High Chaparral, Little Mountain, Moore Knob, Osborne Ridge, Robinson Knob.

No advisory was issued by the National Weather Service as has happened too many times during this winter season and recent seasons.

This occurred as ROARing S-SW winds generated strong upslope cooling at the surface as milder air advected above the massif aloft.  Icing extended locally down to 2500 feet elevation.

This was a significant event at highest elevations, with up to 0.83" of frozen water equivalent.

5 February 2021 at 1551 UTC
View From 22,236 Miles (35,786 km)
High Knob Massif Stands Out On GOES-16

The High Knob Massif and adjacent Wise Plateau were clearly visible on GOES-16 imagery through a break in clouds at 1551 UTC (10:51 AM local time) on 5 February 2021.

5 February 2021
Gorgeous Copernicus-Landsat Image
Clouds-Snowy Mountains-Bare Ground


Beautiful Sunset
5 February 2021

Mountain waves, gorgeous light, and 
lingering snow generated a majestic sunset.

Images courtesy of the Computer Science-Mathematics Department at University Of Virginia's College At Wise





























Miller A Winter Storm
(07 February 2021)

7 February 2021 at 7:15 AM
Deep Snow (12-18"+) On Eagle Knob
Cody Blankenbecler Image © All Rights Reserved

Heavy snow developed late Saturday night into the overnight period of Superbowl Sunday (7 February 2021), with widespread hazardous conditions developing in high snowfall rates.

The Dickenson County Sheriff's Department stated it best 
to the National Weather Service when asked about road conditions, "They are simply terrible."

Snowfall was maximized across the High Knob Massif-Tennessee Valley Divide (which includes Black Mountain and the Wise-Sandy Ridge plateaus) with widespread 7" to 10" totals. 

Snowfall Totals & Depths

Big Stone Gap: 2.0"
(Downtown Near Powell River)

Elevation 1566 feet
Clintwood 1 W: 5.8"
(5-6" of mean snow depth)

Elevation 2650 feet
Nora 4 SSE: 7.9"
(8" of mean snow depth)

Elevation 2365 feet
City of Norton WP: 7.5"
(8" of mean snow depth)

Elevation 2649 feet
Wise: 7.6"
(8" of mean snow depth)

Elevation 4200 feet
High Knob-Eagle Knob: 9.0"
(12" to 18"+ of snow depth)

Numerous scattered power outages occurred along either side of the Virginia-Kentucky stateline, with highest density snow falling across lower-middle elevations below 3000 feet.

Mean Daily Snow Depth
City of Norton Water Plant
Northern Base of High Knob Massif

This has been part of a snowy Christmas 2020 to early February period, with 73% of this time having 1" or more of mean snow depth along the northern base of the High Knob Massif in the City of Norton.

A replay of the most intense snowfall period for this fast moving (hitting) Miller A storm event.

Images courtesy of the Computer Science-Mathematics Department at University Of Virginia's College At Wise







































NW Extent of Miller A Snow

08 February 2021 at 1411 UTC
Defined NW Extent of Miller A Snow

A well defined northwestern extent of snow associated with this Miller A winter storm 
was clear on GOES-16 visible imagery.

 08 February 2021
High-Resolution Copernicus Landsat

A query of elevations revealed that it generally occurred where elevations of highest ridges in the foothills drop below 1500 feet (above sea level).


Frigid Mountain Basins
(08 February 2021)

Temperatures fell to frigid levels within upper elevation basins from the High Knob Massif to Canaan Valley into the AM of 8 February 2021. 

08 February 2021
High-Elevation Cold Air Basins

Data in Big Cherry Basin had not been collected, but it averages colder than Burkes Garden (variation between basins can be 10+ degrees colder than the other on any given night, but in this case mins were likely similar 
with all three basins having significant snow cover).

Big Cherry can also be colder than Canaan Valley, but 
in this case that would be unlikely given much more favorable cooling conditions toward the northeast.

Minimums fell to -3 degrees (F) below zero in Burkes Garden and -17 below in the northeast portion of Canaan Valley where atmospheric conditions were most favorable for extreme minimums (clear, diminishing winds, dry air).

Water Elevation 3120 feet
Big Cherry Lake of High Knob Massif
Frozen Extent Is A Cold Air Indicator

Even before significant snow falls, extent of lake freeze up can be an indicator of basin coldness, with Big Cherry Lake often developing the most extensive ice coverage the earliest across southwestern Virginia.

Water Elevation 3500 feet
High Knob Lake of High Knob Massif
Frozen Except For Near The Dam

Water Elevation 2749 feet
Bark Camp Lake of High Knob Massif
Frozen Except For Above The Dam

Water Elevation 3593 feet
Hidden Valley Lake of Brumley Mountain
Partially Frozen Along The North Side

Mid-upper elevation basins across southwestern Virginia that now contain lakes and wetlands are high conservation priorities with interesting and important micro-climates.


Ice Storm - Part One
(12-13 February 2021)

A simply nasty weather pattern began plaguing locations along and northwest-north of the High Knob Massif and Tennessee Valley Divide during 11-13 February 2021. 

This is called "Part One" since two more back-t0-back winter storms will threaten the mountain area with additional icing and other precipitation types 
in coming days.

12 February 2021
Long Ridge of Sandy Ridge
Home of Foxy The Squirrel
Wayne Riner Photograph © All Rights Reserved

Low-level cold air became dammed against the mountains, with widespread icing across much of Wise, Dickenson, and Buchanan counties within locations along and northwest of the rugged 
Cumberland Front.

Topographical Cumberland Front
(Geological Appalachian Structural Front)

Lower to middle elevation mountain ridges, below 3000 feet, generally accumulated the greatest ice.

12 February 2021
Blackberry Vine on Long Ridge
Wayne Riner Photograph © All Rights Reserved

An extraction of recorded temperatures between two sites along the same NNE air flow trajectory, between southern Wise County and northern Scott County, shows the huge difference in temperature experienced during 12 February 2021
(13 February was nearly identical).

12 February 2021
Southern Wise versus Northern Scott
Difference Across The High Knob Massif

The main factor was terrain blocking of low-level cold air by the High Knob Massif-Tennessee Valley Divide, with air temp only telling part of this story as cloud bases dropped from the upper elevations across middle elevations to as low as 1800 feet (into lower elevations) at times to allow freezing fog to combine with freezing rain-drizzle

12 February 2021
Station Sites Used In Graphical Plot

But, as Paul Harvey used to say, the rest of this story revealed that icing was limited at highest elevations in the High Knob Massif and Black Mountain where a milder SW air flow was able 
to prevail in the mean.

12 February 2021
Snapshot In Time - Kentucky Mesonet

With 99% of Kentucky resting below 2000 feet above mean sea level, how many times is the summit of Black Mountain easily the warmest 
site by day and night?

It is not uncommon for the summit of Black Mountain to be warmer at night than typically colder valleys, but it is rare for Black Mountain to be much warmer than the low-lands by day (as observed during 12-13 February 2021).

13 February 2021
Snapshot In Time - Kentucky Mesonet

While icing looked beautiful through the camera lens of my friend Wayne Riner, it was problematic and resulted in numerous power outages as well 
as broken trees and tree limbs.

12 February 2021
Long Ridge of Sandy Ridge
Icing On An Asparagus Stem
Wayne Riner Photograph © All Rights Reserved

More than 1,000 places were out of electricity on the AEP power system across Wise, Dickenson and Buchanan counties during 12-13 February near the peak of outages (any homes on the Old Dominion system, and on the Kentucky side of the stateline, are not included and shown below).

12 February 2021
Snapshot In Time
American Electric Power Outage Map
Photographer Wayne Riner always has an eye for capturing the unusual, such as this old, rusty nail encased by ice!

12 February 2021
Long Ridge of Sandy Ridge
Rusty Nail Encased By Ice
Wayne Riner Photograph © All Rights Reserved

An into-the-wind ice growth reveals the air flow direction across this high setting of Long Ridge, in the highlands of southern Dickenson County near the Tennessee Valley Divide.

12 February 2021
Beauty of Ice on Long Ridge
Wayne Riner Photograph © All Rights Reserved

Many residents submitted pictures of icing from across Buchanan, Dickenson, and Wise counties 

Courtesy of WCYB ChimeIn

To view all the pictures check 
out their Chimein gallery.

Courtesy of WCYB ChimeIn

Freezing fog continued through 14 February along and north of the High Knob Massif and Tennessee Valley Divide, with an update of the temperature graphic showing colder conditions with a bias continuing toward locations NNW-NNE of the High Knob Massif.

11-14 February 2021
Southern Wise versus Northern Scott
Difference Across The High Knob Massif

 
As of 4 PM Sunday, 14 February, trees were locally drooping  under the weight of ice added by freezing fog along portions of the Tennessee Valley Divide and lower-middle slopes in the High Knob Massif.

14 February 2021
Elevation 3300 feet
High Chaparral Rime-Snow
Darlene Fields Photograph © All Rights Reserved

While snow cover lingered in patches in southern exposures, it remained extensive on northern slopes at upper elevations.

An illustration of the persistence of low clouds on upslope flow is illustrated by snapshots in time captured during the 11-14 February 2021 period.

Images courtesy of the Computer Science-Mathematics Department at University Of Virginia's College At Wise




















































No comments:

Post a Comment