020316 Forecast

My Forecast For Today ( February 3 )

ALERT For High Stream Levels Along Steep Creeks Draining The High Knob Massif And For Strong Rises On Mainstem Rivers.  Caution Is Advised.

ALERT For Strong SSE-SSW Winds Overnight Into Wednesday Morning In Advance And Right Along A Squall Line Of Potentially Strong-Severe Storms

Strong winds are expected across the entire area but with enhancements along high mountain ridges and in typical mountain wave breaking zones ( e.g., Powell Valley of Wise  County & Clinch River Valley of Russell-Tazewell counties in southwest Virginia & along Pine-Black Mountain in SE KY ).

ALERT For Heavy Rain Potential & Strong Rises On Creeks In The Midnight-Noon Period of Wednesday

The threat for strong rises on creeks will be greatest in those draining the High Knob Massif where snow melt has steep creeks running swift, and in any locations that might have downpours in thunderstorms during the Midnight to Noon period of today.

Overnight Into Mid-Morning

Increasing clouds with showers & thunderstorms becoming likely during the midnight-sunrise period.  Strong to locally severe storms possible.  Windy.  SSE winds 15-35 mph, with higher gusts, below 2700 feet.  SSE-S winds 25-40 mph, with gusts of 50-60+ mph, along upper elevation ridges ( locally severe winds to 60+ mph also possible in mountain wave zones ).  Unseasonably warm & humid.  Temperatures varying from upper 40s to the upper 50s.

The main threat from showers & thunderstorms, other than heavy rainfall, will be the potential for downward transfer of powerful winds aloft to the surface.  The main squall line is expected around sunrise along the Virginia-Kentucky border, reaching western Lee County first ( probably before sunrise ).  Some development will be likely in advance of this main squall line during the overnight.

This Afternoon

Rain & showers ending.  Partly sunny.  Winds SSW-WSW at 10-20 mph, with higher gusts.  Temps widespread in the 40s to upper 50s-lower 60s ( tending to drop late ).

Tonight Into Mid-Morning Wednesday

Becoming cloudy and colder.  Cloud bases obscuring upper elevations with freezing fog ( riming ) above 3000 to 3500 feet overnight into morning.  Chance of flurries or snow showers overnight into the morning.  SW winds shifting WNW to NW at 5-10 mph, with higher gusts across upper elevation mountain ridges.  Temperatures varying from upper 10s to lower 20s along upper elevation ridges to the upper 20s to lower 30s by sunrise to mid-morning ( milder leeward of mountains toward the Tri-Cities ).  Wind chill factors in the 10s & 20s into morning ( single digits at the highest elevations of the High Knob Massif ).


Weather Discussion ( February 2-3 )

Afternoon Update

My afternoon update is to add an ALERT for high water on steep creeks draining the High Knob Massif which are near flood stage.  Be very careful along these roaring creeks.

Big Stony Creek Stream Gage At 4:15 PM
Big Stony Creek Stream Gage At 4:15 PM

Big Stony Creek was only 0.6 feet below flood stage as of 12:15 PM.  A new stream level update at 4:15 PM showed a slight drop in the level to 5.5 feet ( 12″ below flood stage ).

Superintendent Andrew Greear, of the City of Norton Water Plant, reported at 4:00 PM that the ROAR of water there had also began to decrease a little.  It was, indeed, a very close shave and a Flood Watch should have officially been issued before this event given recent snow melt + it’s intensity.

Little Stony Creek, as well as many other steep creeks, are ROARING and at very high levels along both sides of the Wise-Scott border into northern Lee County.  Flooding of some low-lying and poor drainage places has occurred.

Clinch River Stream Gage At 4:15 PM
Clinch River Stream Gage At 4:15 PM
The Clinch River at Speers Ferry was a little less than 5 feet below flood stage at 4:15 PM, and is forecast to rise into Thursday.
Clinch River Forecast To Rise
Clinch River Forecast To Rise Into Thursday At The Speers Ferry Point
Rainfall totals topped 2.00″ in the High Knob Massif into today, with 2.24″ reported by the Automated Gauge on Big Stony Creek.  More than 2.00″ also looks to have fallen at Big Cherry Lake Dam.
High Knob Massif Webcam
High Knob Massif Webcam – University Of Virginia’s College At Wise

With relatively rapid afternoon clearing of low clouds temps have risen and I have updated the MAXS, with beginning of cold air transport delayed until tonight.

Nora 4 SSE on Long Ridge of Sandy Ridge
Nora 4 SSE on Long Ridge of Sandy Ridge – Elevation 2650 feet


My Overnight Discussion

A beautiful but increasingly windy Tuesday was observed across the mountain area, with additional wind speed rises tonight along mid-upper elevation mountain ridges and in local mountain wave zones.

High Knob Massif Webcam
High Knob Massif Webcam – University Of Virginia’s College At Wise
Observe that a portion of a Circumhorizontal Arc is visible above as sunlight is refracted by ice crystals in high altitude cirrostratus clouds.  Lower clouds are taking on wave forms amid strong winds.
High Knob Massif Webcam
High Knob Massif Webcam – University Of Virginia’s College At Wise

A nice sunset followed amid unseasonably warm air.  PM MAXS varied from low-mid 50s in the High Knob Massif to upper 60s in downslope locations from Pound to Clintwood and Haysi-Grundy ( 67 degrees officially at Clintwood 1 W ).

Black Mountain MesoNET
Black Mountain MesoNET – Elevation 4031 feet

The focus tonight is on ROARING winds, with 30-50+ mph speeds being common across mountain ridges above 2700 feet in elevation.

Flatwoods Mountain MesoNET
Flatwoods Mountain MesoNET – Elevation 2774 Feet

Local mountain wave gusts have also topped 50 mph in portions of the Clinch River Valley, and no doubt also amid portions of Powell Valley in Wise County.

Southwest Virginia Community College
Southwest Virginia Community College
Wind speeds in Wise have been running just below 30 mph at Lonesome Pine Airport ( perhaps higher in other spots there ).
Lonesome Pine Airport
Lonesome Pine Airport

A large shield of rain, with embedded thunderstorms, will be overspreading the mountain area during the overnight.

Eastern USA Regional Doppler Composite
Eastern USA Regional Doppler Composite At 12:18 AM – February 3

The Jackson Dual-Pol Doppler can be viewed for current images.  Note by clicking on “Toggle Map Size” that this image can be viewed at full screen size ( a zoom tool is on the right side and menu options can be removed ).

JKL Dual-Pol Doppler
JKL Dual-Pol Doppler At 12:32 AM – February 3, 2016
This Doppler automatically refreshes itself to the current image if left running in a separate window-tab, with various zoom options.
Quasi-Linear Convective System With Rear Inflow Jet
Quasi-Linear Convective System With Rear Inflow Jet Notches

The main severe threat for the Kentucky foothills into the mountains can be seen on Doppler imagery, with numerous notable echo notches along a wavy squall line which is indicative of rear inflow jets of strong winds aloft.  Transfer of these to the surface is the biggest concern for potential wind damage.

The AMS definition of a Rear Inflow Jet can be read, with transfer of strong winds to the surface in downdrafts which are enhanced by entrainment of drier, mid-level air into the system being the main idea ( this drier mid-level air aids evaporative cooling and enhances negative buoyancy or sinking of air in water loaded downdrafts in this setting ).

HRRR Model Future Doppler Forecast
HRRR Model Future Doppler Forecast At 7 AM Today

It is this enhanced, wavy squall line that models time to reach the Virginia-Kentucky border by around 7:00 AM, earlier for extreme western Lee County.

European Model 850 MB Wind Field Analysis At 7 PM
European Model 850 MB Wind Field Analysis At 7 PM Tuesday
Wind speeds analyzed up to around 80 mph at the 850 MB level is reason for concern as this squall line moves east into morning.

Heavy rainfall and strong rises on creeks, as well as ponding of water, will be the other main concern for the predawn to mid-day period.

Stay tuned to NOAA Weather Radio for possible warnings.

Have a safe Wednesday.