122716 Forecast

Mountain Area Forecast ( Dec 26-28 )

Dense Fog Will Continue To Impact Portions Of The Area Into Monday Morning.  Fog Will Be Most Dense And Widespread In Valleys At Lower Elevations As Well As Along Upper Elevation Mountain Ridges.

Strong & Gusty S-SW Winds Will Impact The Mountain Area Monday Into Tuesday Morning ( Gusts of 30-40+ MPH ).  Mid-Upper Elevations Will Generally Have The Strongest Winds Outside Of Local Mountain Waves That May Reach Valley Floors In Favored Zones. 

A Squall Line Of Rain, With Embedded Thunderstorms, Will Be Possible By Tuesday Morning With Downpours Of Heavy Rainfall.

Overnight Into Monday Morning

Areas of dense fog ( especially in valleys at lower elevations and on upper elevation mountain ridges ).  SSE-SSW winds at 5-15 mph, with higher gusts, along mountain ridges and plateaus below 2700 feet.  S to SSW winds 15-25 mph, with higher gusts, along mountain ridges above 2700 feet.  Mild with temperatures in the 40s to low-mid 50s ( upper 30s to lower 40s in coolest mountain valleys ).

Monday Afternoon

Partly cloudy.  Unseasonably mild.  Windy.  SSE-SSW winds 10-20 mph, with higher gusts, below 2700 feet.  SSW to SW winds 15 to 25 mph, with higher gusts, on mountain ridges above 2700 feet.  Temperatures varying from low-mid 50s in upper elevations to the low-mid 60s.

Monday Night Into Tuesday Morning

Showers with a chance for thunderstorms.  Locally heavy rainfall.  Windy.  SSW-SW winds 15-25 mph, with higher gusts on mountain ridges-plateaus below 2700 feet.  SW to WSW winds 20-30 mph, with higher gusts, along mountain ridges above 2700 feet.  Unseasonably mild.  Temperatures widespread in the 50s to near 60 degrees.

Tuesday Afternoon

Skies becoming partly to mostly sunny.  Turning cooler.  Winds shifting W at 5-15 mph with higher gusts.  Temps dropping into the 40s by late, except into 30s at highest elevations.  Wind chills dropping into the 20s and 30s by late afternoon ( coldest at highest elevations ).

Tuesday Night Into Wednesday Morning

Mostly clear.  Seasonally cold.  Winds WNW-NW at 5-10 mph along mid-upper elevation mountain ridges.  Temperatures varying from 10s in colder mountain valleys to the 20s to lower 30s ( mildest on exposed mountain ridges ).

Much colder air will arrive Thursday into Friday with a chance for snow showers and flurries.  Some accumulations will be possible.  Stay tuned for updates on this wintry weather.


Weather Discussion ( Changeable )

Late Monday Evening Update

Strong and gusty SSW-SW winds are blowing across the area tonight in advance of an approaching cold front and line of showers with embedded thunderstorms.

Black Mountain Mesonet
Frequent wind gusts around 40 mph are being recorded along high mountain ridges, with 25 to 35 mph gusts common across middle elevation ridges & plateaus.  Locally strong wind gusts will occur in some valleys northeast of the high terrain.  Dense fog, with cap clouds, continues to obscure high mountain ridges along & to the southwest of the High Knob Massif and Tennessee Valley Divide.
Flatwoods Mountain Mesonet

Current inflow and wind streamlines are near the long-term mean climatology; although, models like the GFS do not recognize this and are forecasting little rainfall.

GFS Model 850 MB Wind Field and MSLP Forecast At 1:00 AM Tuesday

High resolution models that have better resolution are picking up on a downpour potential that will occur as the boundary nears during the predawn-morning period.

HRRR Model Future Rainfall Forecast – Next 15 Hours

Very dry air advects ( is transported ) into the area later Tuesday, with clearing skies that sets the stage for frosty cold conditions into Wednesday morning when I expect a large vertical temperature spread between 10s in colder valleys and 20s to lower 30s ( mildest on exposed ridges ).

*High valleys in the High Knob Massif will fall to around 10 degrees if boundary layer winds can decouple, with strong drainage of cold air into the basins.

Previous Discussion

The History Of Christmases Past will be adding in 2016 with headlines for wet & foggy conditions, as abundant low-level moisture ruled the mountain landscape during the holiday.

High Knob Massif Webcam – University Of Virginia’s College At Wise
Another significant rain event accompanied the foggy conditions with a widespread 1.00″ to 1.50″ being observed in counties along the Virginia-Kentucky border in the Cumberland Mountains.
High Knob Massif Webcam – University Of Virginia’s College At Wise
December 2016 precipitation totals of 5.00″ to 10.00″ have been observed, with yet more coming to close out the month and year.
Big Stony Creek of High Knob Massif
*Max precipitation totals occurring in the High Knob Massif where steep creeks have been gushing and mountain lakes overflowing with run-off.
High Knob Massif Webcam – University Of Virginia’s College At Wise

While valleys have areas of dense fog, with light to calm winds, higher mountain ridges are engulfed in low clouds amid strong & gusty S-SSW winds.  Locations in between will experience the best visibility into early Monday.

Black Mountain Mesonet

Strong upsloping SSW-WSW winds will work to lower cloud bases again into Monday Night and Tuesday Morning as rain showers and a line of rain, with possible embedded thunder, develops across the mountain area.

USA Water Vapor Image At 2:15 AM Monday – December 26, 2016
The lower atmosphere is very moist and the air mass will be unseasonably mild for this time of year as the next wind driven front arrives by the predawn-morning hours of Tuesday.

A very photogenic storm system is sprawling across the USA at the current time, with a developing line of rain and thunderstorms.  The downpour potential with this should not be under-estimated as it arrives overnight into Tuesday morning, especially within favored SW upslope flow zones of the High Knob Landform and TN Valley Divide corridor.

GFS Ensembles North Atlantic Oscillation Forecast

A changing pattern is upcoming by late this week into the first week of January 2017 as blocking develops at higher latitudes in the vicinity of Greenland and Alaska, forcing negative dips in both the North Atlantic & Eastern Pacific oscillations = colder conditions with increased chances for wintry precipitation ( around or after the Jan 4-6 period ).

GFS Ensembles Eastern Pacific Oscillation Forecast

Stay tuned for updates on this changing pattern.