Observed Weather Conditions

Frosty cold conditions greeting many mountain valleys across the central-southern Appalachians into morning hours of Wednesday, May 15, with a few specific minimum temperatures including:
Big Cherry Valley: 29 degrees
Burkes Garden: 30 degrees
Frost 3 NE, WV: 30 degrees
Jefferson, NC: 31 degrees
Beckley, WV: 32 degrees
Boone, NC: 32 degrees
Hacker Valley, WV: 32 degrees
Shady Valley, TN: 32 degrees
Transou, NC: 33 degrees
Lewisburg, WV: 33 degrees
Bayard, WV: 34 degrees
Radford: 34 degrees
Bluefield, WV: 34 degrees
Buckeye, WV: 35 degrees
Clintwood 1 W: 36 degrees
Galax: 36 degrees
Sandyville, WV: 36 degrees
White Sulpur Springs, WV: 36 degrees

Since frost typically forms at ground level when official air temperatures, at 5-6 feet above ground level, reach 36 degrees, I have listed sites with min temperatures at or below the 36 degree threshold.

Locations not in Virginia have the state identifier included.

Thursday morning, May 16, also featured scattered frost in coldest mountain valleys with temperatures dropping into the middle 30s.

Looking Forward_Warm Pattern

Above average temperatures are now looking like they will dominate the remaining days of May 2019, with more ensembles of the 51-member European Model cluster coming into agreement.

A southwesterly flow aloft is now being predicted to intensify into next week (see 6-10 day period below for the May 22-26 period).

Although a general below average precipitation regime is forecast, locally heavy showers and downpours in thunderstorms will occasionally be possible with day to day chances being dictated by not only upper air waves but surface outflow boundaries and instability. A main focus of strong-severe thunderstorms will tend to move around the periphery of sinking air aloft, with clusters of storms rotating around the outer edges of heat to the west and north of the Mountain Empire…eventually this will change, so stay tuned for later updates.

Weather Headlines

A beautiful array of orographic clouds capping the High Knob Massif, which contributed to heavy weekend rains, lingered into Monday morning as seen from our weather research webcam at UVA-Wise.

Unseasonably cool conditions will continue with widespread 30s at elevations above 3000-3500 feet, amid abundant clouds on upsloping NW winds, into Tuesday morning. The coldest air temperatures in mountain valleys are expected Wednesday morning when mostly clear skies and light winds will support low-mid 30s (30 to 35 degrees) in colder valleys at middle-upper elevations.

Two different atmospheric settings will generate these cold temperatures, with cold air advection (transport) + adiabatic upslope cooling working to generate 30s at upper elevations into Tuesday morning as cloud bases lower (the freezing level will drop to around 4800-5000 feet such that highest peaks on the windward facing side of highest mountains could form a little rime) versus more classic cold air drainage + radiational cooling under clear skies, light winds, and low dewpoint air that will support cold mountain valley conditions into Wednesday morning (allowing Appalachian frost pocket locations, which are capable of dropping into the 30s or even below freezing during any month of the year, to realize their potential). High mountain ridges will tend to be coldest into Tuesday AM versus high mountain valleys on Wednesday AM.

Monday felt like winter in the high country of the High Knob Massif as low-mid 40s combined with low clouds and gusty NW winds to generate wind chills as cold as 30 to 35 degrees into the afternoon hours of May 13. Ditto for the summit level of Black Mountain.

For those keeping track, this is not surprisingly part of a repetitive Spring 2019 pattern that will feature another surge of warmth, with showers and thunderstorms by late this week into early next week, that is again followed by another cool surge toward the middle of next week. That is the current trend, and given this repetitive pattern it has better than even odds of verification, although, sooner or later this cycle will be broken and conditions which can be called summer will finally set up shop with less radical temperature fluctuations in the mean.

The latest rain event boosted 2019 totals to between 32.00″ and 33.00″ in the City of Norton, at the northern base of the High Knob Massif, and to between 35.00″ and 40.00″ within wetter locations at upper elevations in the massif (15.00 to 18.00″+ during Meteorological Spring).

Alert For High Water Levels

*A general 2.00″ to 4.00″ of rain has fallen along a line extending from Natural Tunnel State Park in Scott County to the City of Norton in Wise County and Council in southern Buchanan County, with 3.50″ to 4.00″ maximum totals in the High Knob Massif, as of early afternoon Sunday (May 12), along a Big Cherry Lake to Guest River Gorge corridor.

Roaring water and dangerously high levels are occurring on creeks draining the high terrain. Extreme caution is advised through the remainder of Sunday into early Monday. Strong rises are also occurring on the Clinch River, but it is expected to remain below flood stage.

The good news, following a weekend spent amid clouds above 3000 feet, is that the bulk of heavy rains have now passed. While another shower or local thunderstorm can not be ruled out, the focus now is on much drier air expected to overspread the mountains by Monday into Tuesday with seasonally cool conditions.

Pattern Changes Ahead

*Increasing showers and downpours in thunderstorms will begin to impact the mountain region in coming days, with the Friday-Sunday period of May 10-12 featuring an approaching frontal boundary that slows down across the Appalachians. Hit-miss activity Thursday will become more widespread in nature Friday afternoon into Saturday-Sunday as a upper wave interacts with the surface boundary.

A southwesterly upper air flow (above) ahead of a upper air trough will support occasional waves of showers & thunderstorms through this weekend. Air will turn cooler Saturday as the surface boundary temporarily passes south of the Cumberland Mountains and the low level flow turns northerly, with upslope flow and lowering clouds. A wave of low pressure will then enhance showers-thunderstorms on Mother’s Day (Sunday, May 12).

Heavy to locally excessive rainfall amounts will be possible through this weekend in advance of a much cooler, drier air mass currently expected to overspread the Appalachians by early next week. Those living along streams and in typically flood prone, poor drainage locations will need to monitor the possibility for rapid water level rises through this weekend.

Widespread 1.50″ to 3.50″ rainfall amounts from the Clinch River Valley of Scott County northward across the High Knob Massif into Dickenson County during May 2-5, combined with long-term antecedent wetness, sets the stage for potential high water concerns given additional heavy to locally excessive rainfall amounts upcoming through this weekend.

*Much cooler and drier air is currently expected to overspread the area during Monday into Tuesday of May 13-14, although cooler air will be noted Saturday on upsloping northerly air flow behind initial passage of a surface cold frontal boundary, which stalls, then lifts back northward across the region during Sunday.

A trough (above) in the upper air will replace upper air ridging aloft and be accompanied by much cooler, drier air (below) by May 13-14.

*The potential for air to become cold enough to support frost and near to below freezing temperatures, especially within typically colder mountain valleys away from major rivers and lakes, is being monitored for early next week.

This is not surprising, with minimum temperatures dropping into the 30s to low 40s within colder mountain valleys into morning hours of May 7 and into the 40s during May 8.

For more information reference: Spring 2019_High Knob Massif Area

Mountain Area Forecast ( May 9-11 )

Overnight Into Thursday Morning

Partly to mostly clear. Seasonally mild. Winds SE-S at 5-15 mph, with higher gusts, on mountain ridges and plateaus below 2700 feet. Winds S-SSW at 10-20 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures varying from low-middle 50s in cooler mountain valleys to 60s on exposed middle elevation ridges and plateaus.

Thursday Afternoon

Partly cloudy with a chance of hit-miss showers and thunderstorms. Winds S-SW at 5-15 mph with higher gusts on mountain ridges & plateaus. Temps varying from upper 60s to lower 70s at upper elevations to the upper 70s to lower 80s (locally warmer within downslope locations of northern Wise-Dickenson and Buchanan counties).

Thursday Night Into Friday Morning

Chance of local evening showers & thunderstorms, then mostly cloudy and mild. Winds S to SSW 5-10 mph, with higher gusts, along mountain ridges & plateaus below 2700 feet. Winds SSW to WSW at 10-25 mph, with higher gusts, mountain ridges above 2700 feet. Temperatures in the upper 50s to middle 60s. Local areas of fog (especially where rain fell).

Friday Afternoon

A chance of showers and thunderstorms. Local downpours. Any storm could be strong to locally severe. Winds SW 5-10 mph, higher gusts possible around thunderstorms. Temperatures varying from mid 60s to around 70 at upper elevations to the mid 70s to lower 80s (warmest lower elevations).

Friday Night Into Saturday Morning

Showers & thunderstorms becoming likely. Local downpours possible. Winds becoming northerly at generally less than 10 mph. Cloud bases dropping across upper elevations and into middle elevations between 2500-3000 feet in locations along and north of the High Knob Massif-Tennessee Valley Divide. Temperatures varying from low 50s to low 60s.

Saturday Morning Through The Afternoon

Showers and a chance for thunderstorms. Local downpours possible. Winds becoming light and variable in direction with elevation. Areas of fog, widespread at upper elevations. Temperatures in the 50s to mid-upper 60s (warmer south into the Great Valley and Tri-Cities).

Intervals of showers and downpours in thunderstorms are expected during the weekend. Locally heavy rainfall amounts will be possible, especially in advance of an upper air trough axis by late in the weekend.

ALERT For High Water Levels And Local Flooding Through The Overnight Into Saturday Morning

Up to 3.00″+ of rainfall has caused creeks draining the High Knob Massif and adjoining areas to exceed or approach flood stage.  Extreme caution is advised through tonight into Saturday morning.

Big Stony Creek crested half a foot above flood stage at 8:15 PM, with additional downpours likely to cause even higher levels before colder air fully takes hold of the mountains.

Merely the latest in a series of spikes to near and above flood stage, with some 35.00″ to 40.00″ of precipitation since the beginning of December ( > 30.00″ this year ).

The highest water levels since late February flooding are being observed.  More downpours, due to current conditions, will continue to pose a flooding risk into the overnight and early hours of Saturday.

The large landslide near Cracker Neck should be monitored for any possible additional slippage.

The wetness of 2018 was anomalous across a wide region of the eastern USA, with locations along and east of the Blue Ridge and across the Bluegrass and foothills west of the Appalachians having surpluses most above average ( up to 220%+ ).

Andrew Greear, superintendent of the City of Norton Water Plant, reported 76.69″ of total precipitation in 2018 ( noting a rain gauge spill occurred in Feb ).

That was 119% above the 64.41″ average of the past 10-years and 128% above the 59.91″ average of the past 25-years for Norton.

*Norton is the wettest town or city in Virginia over a period of a decade or more, with consistent wetness observed amid the lifting zone of the High Knob Massif.

The 68.74″ in Clintwood, by contrast, marked only the second time since record keeping began in 1964 to go above 60.00″ and shattered the old record of 60.98″ established during 2011.

**Clintwood is downslope of the High Knob Massif and the Tennessee Valley Divide on mean annual flow trajectories. 

Virginia Precipitation Totals During 2018

City of Norton
76.69″

Galax
73.24″

Stuart
70.82″

Clintwood
68.74″

Danville
67.43″

Lynchburg
65.70″

Wise
63.90″

Richmond
63.73″

Charlottesville
62.59″

Roanoke
62.45″

Lebanon
61.86″

Saltville 1 N
59.81″

Grundy
59.69″

Burkes Garden
57.88″

Wytheville 1 S
56.94″

Norfolk
56.68″

Blacksburg
52.03″

Wallops Island
47.39″

Precipitation totals of 80.00-90.00″+ were common during 2018 in the High Knob Massif-Black Mountain area of far southwestern Virginia and along the Blue Ridge of Virginia.

Effective precipitation was much higher when adding in fog drip and rime deposition upon trees, with around 250 days being engulfed in clouds at upper elevations during 2018.

Snowfall totals around 112.0″ were observed during 2018 in the High Knob Massif.  This included a White Christmas ( the 20th out of the past 30 ).

2018 precipitation reached extreme values across the state of North Carolina, with totals exceeding 100″ on the coast and along portions of the Blue Ridge.

A persistent E-SE flow during many events generated a large contrast across the southern Appalachians.  A total of 139.94″ in Mount Mitchell State Park was in contrast to 111.43″ on Mount LeConte, Tn., and nearly 9.95″ more than the 129.99″ at Lake Toxaway 2 SW in southwestern North Carolina.

Lake Toxaway generally reports more than Mount Mitchell and has the second highest annual average in the eastern USA, next to the highly monitored Mount Washington, NH Observatory site in the White Mountains.

 

ALERT For A Continuation Of Hazardous Road Conditions – Especially Secondary Routes Into Tuesday

Secondary roads remain snow covered and locally impassible, with more time being needed for VDOT work to be completed on these roadways.

ALERT For ALL Roads Tonight-Tuesday Morning With Refreezing And Black Ice

A sharp temperature drop tonight into Tuesday morning will create icy patches with refreezing. 

Air temperatures are expected to plunge into single digits and 10s, except locally colder in high mountain valleys at upper elevations where dry advection will be occurring to enhance cold air drainage over deep snow cover.

To see larger images, and a short time-lapse of the storm, reference the High Knob Landform and scroll down to the Major Winter Storm section.

Majestic orographic snow clouds capped the high country for both many miles and hours Monday morning, laying across heads of the Big Cherry Lake to High Knob Lake corridor ( as seen above ).  This was adding even more moisture to trees.

Storm snowfall totals ended up as expected within the lifting zones of the High Knob Massif where a general 1 to 2 feet of snow accumulated.

Totals varied from around a foot in Wise to 19″ at High Chaparral ( 3300 feet elevation ) to 2 feet or more in the main crest zone of the massif.

This included the Scott County side where air was rising up toward the High Knob Massif, with a foot or more of snow reported from Natural Tunnel State Park and Duffield to Castlewood & Abingdon downstream of the massif. 

One of the most dramatic short-distance contrasts observed anywhere with this storm occurred as air flowed across the High Knob Massif and through an orographic standing wave to subside and warm amid lee-ward ( downslope ) locales from Powell Valley to Big Stone Gap and Pennington Gap.

Air flow trajectories in the 900 to 600 mb layer were streaming across Scott County and through the wave standing along the High Knob Massif.

Snowfall was enhanced on the rising air side and diminished along and downstream of the subsidence, or sinking, air side of the massif.

This event, and many past storm events, revealed a transition zone of mixed precipitation that became orographically anchored along the lee-ward side where warmer air was being forced to sink as colder air ( on the rising side ) was being lifted upward over the high country ( a Thermally Indirect Circulation ).

This is more than just a mountain-valley phenomenon as this and many past events demonstrate, with significantly less snow depth & total precipitation at high elevations in adjacent Black Mountain.

*More than 2.00″ of water equivalent in the High Knob Massif during this event was 1.00″ or more above what was reported on Black Mountain.