Mountain Area Forecast ( Jan 22-25 )

An ALERT Continues For Strong-Gusty SSE-SW Winds During Monday Night Into Tuesday Morning As Temps Begin To Turn Colder.  The Coldest Air Is Expected To Arrive Tuesday Night Into Wednesday.

A general SSE-S wind flow and mild conditions will continue through Monday evening, with highest elevations and favored mountain wave zones having the strongest wind speeds.  Local gusts over 50 mph will be possible.

A wind shift to SW overnight is expected to begin to focus the strongest winds into the Wise & Sandy Ridge plateaus and upper elevations of the High Knob Massif during the predawn to mid-morning period Tuesday, with general strong-gusty conditions across the area in a widespread nature along and behind the passage of a cold front.  Air temperatures Tuesday will display falling trends during mid-late afternoon, following any small rises or steady nature through early Tuesday PM.

Cold air will surge into the mountains Tuesday night into Wednesday with enough low-level moisture to generate some snow showers, flurries, and a chance for local squalls.

Monday Night Into Tuesday Morning

Mostly cloudy and mild through the evening with a chance of rain showers.  Rain showers becoming likely overnight.  A chance of thunder.  Turning chilly by morning.  Windy.  SSE to S winds shifting SW at 10-20 mph, with higher gusts below 2700 feet.  Winds SSE to SW at 15-25 mph, with higher gusts, on mountain ridges above 2700 feet.  Temperatures dropping into the low 30s to low 40s by morning ( coldest at highest elevations ).  Wind chills dropping into the 20s to low 30s, except 10s at the highest elevations, by morning.

Tuesday Morning Through The Afternoon

Predawn to mid-morning clearing giving way to cloudy skies.  Turning colder.  Gusty.  A chance of flurries by late.  SW to W winds 10-20 mph with higher gusts.  Temps near steady to falling into the 20s at upper elevations and into the 30s at lower-middle elevations along and north to west of the High Knob Massif-Tennessee Valley Divide.  A little milder in downslope locations of the Clinch, Powell, and Holston river valleys.  Wind chills in the 10s and 20s, coldest at highest elevations.

Snowfall Forecast – General dusting up to 1″ between Tuesday Night & Midnight Wednesday ( locally more possible at upper elevations of the High Knob Massif )

Tuesday Night Into Wednesday Morning

Snow showers & flurries developing late into overnight.  Light snow accumulations.  Cold.  W-WNW winds 5-15 mph, with higher gusts.  Temps varying from the middle-upper 10s to the middle-upper 20s ( coldest at upper elevations ).  Low cloud bases with rime formation becoming possible at highest elevations.  Wind chill factors dropping into the 10s to low 20s, except single digits to around 0 degrees in gusts on highest mountain ridges.

Wednesday Morning Through The Afternoon

Partly-mostly cloudy. A chance of snow showers, flurries.  Light accumulations possible.  Cold & blustery.  WNW winds 5 to 15 mph with higher gusts.  Temperatures varying from upper 10s to lower 20s at upper elevations to upper 20s to lower 30s at low-mid elevations along and north to west of the High Knob Massif-Tennessee Valley Divide.  Wind chills in 10s to low 20s, except colder on highest peaks.

Wednesday Night Into Thursday Morning

Partly-mostly cloudy.  A chance of flurries.  A heavier local snow shower possible during the evening.  WNW winds 5-15 mph, with higher gusts.  Temperatures widespread in the 20s and 10s ( coldest at upper elevations ).  Wind chills in the 10s and single digits ( below zero in gusts on highest peaks above 3500 feet ).

The potential for a significant storm system featuring a rain to snow transition is being monitored for the late weekend-early week period of January 28-29.  Stay tuned for updates.

Reference January 1985 Arctic Blast for a review of a great cold wave that froze the mountain landscape 33 years ago this week.

 

Weather Discussion ( Up-Down Pattern )

January 23 Update

This update is to include light snow accumulations with activity developing late Tuesday night into Wednesday, amid limited moisture, and to slightly adjust temps.

A little blush of color on clouds that increased during Tuesday afternoon to cap off a very windy period.

As expected, the strongest winds developed in the Wise area as low-level winds shifted SW overnight into Tuesday with gusts topping 40 mph.  A peak gust of 52 mph was recorded by the Black Mountain Mesonet, with no doubt higher gusts in open meadows from the High Knob peak to Camp Rock.

*The Camp Rock Meadow ( a quarter to one-half mile long ) is often very windy on air flows possessing both southern components and northerly components ( elevation around 3900 feet ).

Temperatures reached a mid-morning MIN then climbed amid sunshine to a early afternoon MAX before slowly beginning a decline during mid-late afternoon.

*The MAX temp for the day occurring just after Midnight.

Although moisture is limited with incoming continental Polar air, given Great Lake moisture injection is missing the southern Appalachians toward the north, a couple of upper air waves in the flow field will combine with WNW upslope to generate snow showers and flurries.  A heavier burst of snow, on at least a localized basis, can not be ruled out.

Most of the activity is expected overnight into Wednesday morning with the initial cold air advection and developing WNW upslope, then again late Wednesday with a stronger upper air wave and 850 MB thermal MIN.

*I expected the heaviest snow to fall in the area of Canaan Mountain and Canaan Valley in the northern mountains of West Virginia, with totals of more than 6″ being possible there into Thursday AM.

 

Previous Discussion

A up-down temperature regime is expected to rule the remainder of January 2018, with increasing signs that another prolonged wintry lock-down will develop during February across the eastern USA.  Could the worst of this 2017-18 winter season be upcoming?

Frequent mountain waves were observed through Monday as strong winds blew across the High Knob Massif ( below ).

Although most mid-upper elevations locations were in the 50s during Monday, temperatures varied from upper 40s at the summit level of the High Knob Massif to middle 60s in downslope locations like Clintwood ( 64 degree PM MAX ).

Strong low pressure over the center of the nation began to impact the mountains Monday, with gusty winds and a mild flow of southerly air ( it is difficult to get a truly warm feel to the air at the top of the high country in January, with 40s and wind gusts over 30 mph, but compared to last week it was a ”balmy” day with modified maritime tropical air mass advection ongoing in advance of a cold front ).

Showers, with embedded thunder, are developing in the warm sector of the current cyclonic storm where warm conveyor belt air is being lifted ahead of the system’s cold front and its descending dry conveyor belt air which is sinking downward from the mid-upper troposphere to generate a dry slot that is visible on satellite imagery.

Thunderstorms developing in the warm sector west of the mountains are forming in a Theta-E ridge, or low-level axis of available potential energy, which is forecast to fade as activity propagates east into the mountains, thus I have only a chance of thunder as the front approaches.

Observe the large swirl of the current cyclone dominates this view of North America, with a pronounced comma-head of low clouds in its cold conveyor belt that have risen beneath the warm conveyor belt into middle portions of the troposphere and wrapped cyclonically around the center of low pressure.

A pronounced dry slot and warm conveyor belt ( with a Pacific-Gulf of Mexico moisture tap carrying deeper moisture south and east of the Appalachians ) are also clearly visible.

Due to the large, cyclonic circulation around this system air will be turning cold on SW winds as it begins to pull a mass of air featuring continental Polar properties into the area during the predawn-morning hours of Tuesday.

Note that while this is different from the continental Arctic air mass of last week, a rather dramatic change will still occur with falling temperatures & wind chills Tuesday into Wednesday.

Enough low-level moisture will be present to generate snow showers, flurries, and the chance for some local squalls as cold air increases Tuesday Night-Wednesday.

With the best low-level moisture currently expected to flow into the central-northern highlands of West Virginia, that is where the greatest snowfall amounts will likely occur.

A WNW flow field will favor heaviest amounts along and west of the Cumberland-Allegheny Front, as well as within a narrow zone from Mount Rogers southwest along highest elevations of the Tennessee-North Carolina border.  Lifting will be aided by passage of a couple upper air waves, such that amounts of 1-2″ will be at least locally possible in the southern Appalachians ( stay tuned for updates ).

Increased wave forcing into the stratosphere, with warmth building above Siberia expected to move across the Pole to above Alaska and western Canada, will aid the rebuilding of tropospheric ridging upstream of the eastern USA during the next 1-2 weeks.

Looking down the rocky road, it appears that much more significant cold air will return to the eastern USA with a variety of factors beginning to come into alignment.

A changing SOI ( Southern Oscillation Index ) with an eastward propagating Madden-Julian Oscillation wave is forecast to enter cold phases for the eastern USA.

It is looking like some very interesting weather times are upcoming as this 2017-18 winter season is not even close to being finished ( with respect to cold and snow ).