ALERT For Dense Fog Formation & Freezing Fog-Drizzle At Middle To Upper Elevations Along And North of the High Knob Massif And Tennessee Valley Divide Into Monday Morning

A shift to northerly upslope flow behind the passage of a cold front will drop cloud bases and temperatures into the predawn-morning hours of Monday.  Light freezing rain or drizzle, and freezing fog, will be possible at middle to upper elevations along and north of the High Knob Massif.

3:00 PM Monday Update – A nearly isothermal atmosphere has developed with temperatures +/- 2.0 degrees of 32 F degrees from Clintwood ( 1560 feet ) all the way up to the summit level of the High Knob Massif ( 4223 feet ).

Lonesome Pine Airport ( LNP ) has been having  sensor problems, such that the following temperatures ( near the Airport on Pole Bridge Road ) are the most accurate:

Some places in Scott and Lee counties have been experiencing persistent cloud breaks, but that is due to downsloping off the high country of the High Knob Massif on NE air flow.

Moisture beneath a low-level temperature inversion will threaten to keep conditions cold and damp Monday, with best odds of this happening in locations along and north of the High Knob Massif-Tennessee Valley Divide where low-level northerly air flow will be rising and cooling.

ALERT Continues For High Water Levels Across The Area With Flooding On Main Stem Rivers Into Monday

Although water levels along headwater creeks are dropping, the danger has not yet passed with ROARING water gushing on creeks draining the High Knob Massif-Tennessee Valley Divide.  A recap of some rainfall totals reveals why ( noting IFLOWS tend to read low ):

Storm Rainfall Totals
February 10-11 Flood

Georges Fork: 3.80″
( John Mullins )

Clintwood 1 W: 3.90″

Fort Blackmore IFLOWS: 4.16″

Big Stony Creek IFLOWS: 4.22″
( SE Base of High Knob Massif )

Herald IFLOWS: 4.31″
( Sandy Ridge )

Pole Bridge Road: 4.54″
( Layton Gardner – Wise )

Stone Creek IFLOWS: 4.78″
( Lee County )

Ben Hur IFLOWS: 5.24″
( Lee County )

Little Mountain IFLOWS: 5.24″
( Route 237 )

Black Mountain Mesonet: 5.35″
( Near Harlan-Wise Line )

*Big Cherry Dam IFLOWS: 5.40″

Robinson Knob IFLOWS: 6.65″
( High Chaparral-Robinson Knob Communities )

Reference Late Winter In The High Knob Massif for more.

*Prior to this big storm event I measured 8.08″ at Big Cherry Dam during January 1-February 9, some 14% more than the IFLOWS and both totals are too low due to wind induced under-catches caused by air blowing across the Dam.  I hope to add an Alter Shield to the NWS hand-measured gauge at some point this year to help reduce some of these losses due to wind ( the Black Mountain Mesonet site has an alter-shielded rain gauge ).

Flooding was especially bad in the Ramsey-Tacoma-Coeburn valley corridor as MAX reported storm rainfall fell over the headwaters of the Clear Creek and Burns Creek watersheds of the Guest River basin & the Little Stony Creek watershed of the Clinch River basin ( Guest River is also a tributary of the Clinch River but first cuts through Guest River Gorge of the High Knob Massif prior to joining the main river ).

Other areas with significant flooding were along and down-stream of the South Fork of Powell & Big Stony Creek basins in the Cracker Neck-East Stone Gap to Big Stone Gap section of Wise County and the Ka-Fort Blackmore section of Scott County ( translating to general main-stem river flooding along both the Clinch and Powell ).

During our UVA-Wise undergraduate field research trip on February 9 ( reference notes below ) rather extensive snow cover was documented from Bowman Mountain ( head of Clear Creek basin ) across High Knob Lake basin into the basin of Big Cherry Lake.  Snow core data found 1.00″ to 2.00″ locked in the snow, meaning that roughly 1.50″ of water was added to totals reported from Robinson Knob southwest to Big Cherry Dam ( creating effective storm totals of 7.00″ to 8.00″ from these headwater locations ).

Very few places on Earth could handle 7.00″ to 8.00″ of water input without causing flooding, and it is actually amazing ( incredible ) that flooding was not more severe.  The only explanation being that max rainfall and snow melt run-off occurred from basins that are heavily forested with trees ( and in the case of Big Cherry Lake basin, have valleys filled with water absorbing Sphagnum moss species ).

*Sphagnum can soak up to 25+ times it weight in water and over acres of land that = a great amount of water storage.  Reference Sphagnum Moss from the Encyclopedia of Life.

And I will state with absolute certainty, if these head- water locations had not been heavily forested, intact watersheds that flooding would have not only been MUCH more severe but likely deadly.

This is simply a critical point that can not be denied and should be considered by all in light of a pending 7,464 acre project planned to impact the Clear Creek-Burns Creek basins with notable logging & burning.

Mountain Area Forecast ( Feb 12-13 )

Overnight Into Monday Morning

Lowering cloud bases.  Turning colder.  Showers changing to freezing rain & drizzle.  Dense fog and freezing fog at mid to upper elevations along and north of the High Knob Massif.  Winds shifting  NNW to NNE at 5-15 mph with higher gusts.  Temperatures dropping into the middle 20s to low-mid 30s, coldest at upper elevations.  Wind chills falling into the 20s, with 10s at upper elevations.

Monday Morning Through The Afternoon

Low clouds & chilly.  Damp.  Winds N-NE at 5-15 mph, with higher gusts.  Temperatures nearly steady in the 20s to low-mid 30s.  Wind chills in the 20s to around 30 degrees, except colder at high elevations.

Monday Night Into Tuesday Morning

Partly-mostly cloudy.  Areas of fog.  Chance of light rain or freezing rain showers.  Winds shifting to E-SE at 5-10 mph, with higher gusts, along mountain ridges and exposed plateaus.  Temperature falling slowly in mountain valleys to near steady-rising along mountain ridges and exposed plateaus in the 20s to low-mid 30s.  Rime formation again within upper elevations ( above 3300 feet ).

Tuesday Afternoon

Mostly cloudy.  Chilly.  Small chance of a rain shower.  Winds SSE-SW at 5-15 mph with some higher gusts.  Temperatures in the 30s to lower 40s.

 

Previous Flood Statements & Updates:

Mountain Area Flood Watch

12 Midnight Update – Sunday ( February 11 )

A general 3.00″ to 5.00″+ of rain has now fallen across the mountain area, from Wise-Scott-Lee counties into Dickenson County ( I measured 3.25″ as of 2345 hours on February 10 ) and the situation is getting worse in many places as rain and run-off continues.

*I have had water from the creek that goes by my home beneath the house at least 3 times during past years, and I fully understand the pain, misery, fear or whatever you may feel in these situations as the stream gradients here in the mountains add greatly to the danger of flowing flood waters.  So please DO NOT take chances, as a single slip of the foot could be deadly, let alone even thinking about trying to drive through any flood waters.

We have had some trees and limbs fall, in addition to mud-rock slides to add complications to increasing flooding.  If you are in a safe place now, please stay there.  If you live along a creek, like I do, it will be a LONG night.  Water levels have to be closely watched but please do not take unnecessary chances.

Know that current river levels forecasts are likely going to have to be adjusted UPWARD, as the full magnitude of this event becomes more apparent.

Note that while the main-stem Powell River in Big Stone Gap was last reported at around 10 feet, my records show that flooding typically begins on the South Fork of Powell in East Stone Gap and portions of Powell Valley when the level goes above 6.0 feet ( to indicate how serious this current setting is becoming ).  Another indicator is that the spill-way at Big Cherry Dam is now reporting around 1.5 feet of overflow, which is huge given the width of the overflow, and its increasing!

*The South Fork of Powell is a subterranean stream; however, yesterday the below ground conduits were already full and the river running completely above ground.  Always a bad signal in advance of a heavy precipitation event. 

I like ( hate, but you know what I mean ) the HRRR Model prediction of future rainfall in the next 15-hours better than the NAM and new GFS which have been ( along with the ECMWF ) under-estimating rainfall rates ( the former GFS runs doing better on basin average amounts by the conclusion of this event…not up to this point in time! ).

Air temps are the warmest of this event at elevations above 4,000 feet, indicating a more buoyant and totally saturated column that will be productive in generating more rain, with a focus overnight into Sunday morning toward the major mountain barriers ( High Knob Massif-Tennessee Valley Divide ) on gusty and upsloping SW winds.

While this may help Dickenson, northern Wise, and Buchanan counties by offering at least the chance for more downslope forced lulls or weakening of radar echoes, it is not good news for much of Wise County, northern-central Scott and Lee counties.

It is obvious, but should be noted that since the Tennessee Valley Divide forms the southern border of Dickenson County and the top of the Russell Fork Basin watershed ( Sandy Ridge to Hazel and Big A mountains ) that is not good news for main-stem rivers.  Highest rainfall totals so far in Dickenson have fallen along the top of the basin, meaning all that run-off has to drain downstream on the Pound, Cranes Nest, McClure, and Russell Fork…with a notable convergence in the Haysi area where the McClure and main-stem of the Russell Fork meet ( outflow from John Flannagan Dam then enters the Russell Fork downstream toward Bartlick ).

*If you still doubt SW flow is important, I reference the great April 1977 Flood Event ( the benchmark ) which was dominated by SW flow.  While all locations in the echo training corridor had excessive rainfall amounts, greatest totals were within upslope locales.

Lifted indecies drop below zero, meaning that I will have to introduce the possibility that thunder ( convection ) may be a factor Sunday until a cold front passes and introduces a notable drop in temperatures Sunday Night-Monday AM.

We must all hope and pray that convection, thunder, does not develop Sunday as that could exacerbate the situation where ever such activity forms ( even across downslope locations ).

 

5:00 PM Update – Saturday ( February 10 )

I have now had 2.00″ of rain in Clintwood and the IFLOWS are running behind actual totals.  That should be noted due to the heavy, fine, fasting falling nature of this type of rain.

Many creeks in the area are now near or beginning to go above flood stage ( the creek beside my house, only a tertiary stream, is approaching its flood stage ).

The highest automated rain gauge total is now 2.62″ from the Robinson Knob community of the High Knob Massif; however, at least 3.00″ has likely fallen ( * ).

*Otis & Nancy Ward measured for years by hand near this IFLOWS in Robinson Knob and consistently measured 10-20%+ more.

The bottom line, while totals are important it is going to become moot as the area goes into flood with still a long corridor of moderate-heavy rain upstream.

10:00 AM Update – Saturday ( February 10 )

As of 10 AM Saturday a general 1.00″ to 1.50″ of rain has fallen along the High Knob Massif in the past 12 hours, above model forecast’s for this time period.

*Specific Automated Totals Include:

Big Stony Creek: 1.62″
Robinson Knob: 1.43″
Little Mountain: 1.04″
Fort Blackmore: 1.04″
Big Cherry Dam: 0.92″
Dungannon: 0.88″

*Automated IFLOWS totals tend to be somewhat less than hand-measured amounts, especially when downpours occur as recently observed along the Wise-Scott border area.

Heaviest rainfall is currently expected to develop by later Saturday afternoon into Saturday Night-Sunday Morning, with a long feed of moisture streaming northeast from the Gulf of Mexico.  Snow continues to retain water at highest elevations, with the main release likely to occur by late Saturday into early Sunday.  Significant spikes will be possible on Big Stony Creek & South Fork of the Powell.

Hydrologic Outlook – A Heavy To Excessive Rainfall Pattern Will Be Developing From This Weekend Into Next Week With Multiple Waves Of Rain Creating A Setting Favorable For High Water And Flooding

The above is a generalized broad-brush of the upcoming rainfall pattern from the Weather Prediction Center, without factoring in complex terrain features and orographics beyond a larger-scale.

While specific models may vary on exact rain amounts from run to run, there is scary agreement in the focus of heavy to excessive rainfall being concentrated along western slopes of the southern Appalachians, as depicted by NOAA with a composite view above during the next week.  This does not factor in local orographics or the snow melt water that will also be added during the next couple of days.

Local Setting – Mesoscale Discussion – February 9

From my perspective all EMS officials need to plan for the worst case scenario and hope for the best, with moderate to strong orographic forcing being forecast by terrain models during the next 48-hours ( the initial rounds of this event ).

To simplify, a strong and moist low-level air flow will be streaming into the Cumbeland Mountains on wind speeds currently forecast to be SW at 30-40 knots at elevations above 3000 feet.  This will enhance lift of air into the High Knob Massif-Tennessee Valley Divide corridor ( which includes Black Mountain ) to impact headwaters of the Clinch, Powell, Russell Fork and Cumberland rivers within this area.

People living along creeks draining to these rivers, in addition to those along these main-stem rivers, will need to remain alert for strong water level rises this weekend.  Please stay tuned to local officials and the NOAA Weather Radio ( and favorite media sources ) for possible warnings that may be needed by later Saturday into Sunday.

Snowpack Update – Snow Core Data

A substantial amount of concentrated snow remains across the High Knob Lake and Big Cherry Lake basins in the high country of the High Knob Massif as of February 9 ( PM ).

This despite more than 1.50″ of rainfall during February 7-8 ( approximately 3.00″ of precipitation at Big Cherry Dam so far in February, with 8.08″ so far this year ).

A clean snow core found 0.40″ of water content per 1″ of snow depth, with a general 3″ to 5″ of snow depth remaining across the High Knob Lake basin into a significant portion of the sprawling Big Cherry Lake basin ( ice-packed to slushy snow remained on the road at elevations above 3000 feet downstream of Big Cherry Dam toward the Big Stone Gap Water Plant ).

Previous snow melt pushed Big Stony Creek to 0.7 feet above flood stage in wake of a general 1.50-1.75″ of rain, with added snow melt resulting in the stream response observed by the gauge ( above ). 

While the bulk of deepest and most widespread snow melted away, what remains is concentrated and will add locally to run-off into both the Clinch River and Powell River.

My recorded amount of 16.5″ of snow on Eagle Knob during the January 29-February 5 period looks on target, if not too low given what a larger survey by our UVA-Wise research students found Friday afternoon ( with 6″ to 12″ drifts still measured in numerous places from the High Knob Peak to Big Cherry Dam ).

Rainfall From Different Forecast Models

The 7 PM Friday run of the European Model is forecasting 2.50″ to 4.50″ of rain along the Cumberland Mountains during the next 48-Hours ( ending 7 PM Sunday ).