An Alert For Dense Fog Is In Effect For Elevations Above 2600 to 3000 Feet Within The Cumberland Mountains Through 10:00 AM Saturday
Cooling air on northerly upslope flow in the wake of widespread, heavy rains will allow cloud bases to remain low through morning hours of Saturday. Caution is advised for those traveling at higher elevations overnight into Saturday morning.
Previous Alerts
The Storm Prediction Center Has Issued A Marginal To Slight Risk For Severe Thunderstorm Development On Thursday Into Friday ( July 27-28 )
Locally Heavy To Excessive Rainfall Will Be Possible Thursday Into Friday Ahead Of A Strong Cold Front That Could Lead To Local High Water Problems
Overnight Into Thursday Morning
Increasing high clouds. Hazy & humid. Areas of valley fog. Winds SSW-WSW 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures varying from low-mid 60s to around 70 degrees.
Thursday Morning Through The Afternoon
Showers & downpours in thunderstorms developing in a hit-miss fashion. Some storms could be strong to locally severe. SW winds 5-10 mph, with higher gusts. Temps varying from upper 60s to lower 70s in upper elevations to the upper 70s to lower 80s ( warmer south toward the Tri-Cities ).
Thursday Night Into Friday Morning
A chance of showers & thunderstorms. Downpours possible. Winds S-SW 5-10 mph, with higher gusts. Hazy, humid with areas of fog. Warm with temperatures in the 60s to low 70s.
Friday Morning Through The Afternoon
Showers & downpours in thunderstorms becoming likely. Some storms could be strong to locally severe. Winds S-SW 5-15 mph, with higher gusts at elevations below 2700 feet. Winds SW to W 10-20 mph, with higher gusts, at elevations above 2700-3000 feet. Temperatures in the 60s to low 70s. Low cloud bases with dense fog at upper elevations.
Friday Night Into Saturday Morning
Rain showers. Turning cooler. Winds shifting NNW-NNE at 5 to 15 mph, with higher gusts. Temperatures dropping into the 50s to low-mid 60s ( coolest at highest elevations ). Low clouds with dense fog at higher elevations.
Saturday Morning Through The Afternoon
Morning showers ending with low cloud bases lifting into afternoon. Skies becoming partly to mostly cloudy. Winds NNW to NNE at 5 to 15 mph, with some higher gusts along mountain ridges. Temperatures varying from upper 50s to lower 60s at highest elevations to the upper 60s to lower 70s ( warmer south into the Great Valley ).
Low temperatures are expected to fall into the 40s to low-mid 50s into Sunday morning ( coolest within higher mountain valleys ).
The coldest mountain valleys at upper elevations, from the High Knob Massif to Burkes Garden, are expected to drop into the 40 to 45 degree range on both Sunday and Morning mornings, with an increasingly large vertical temperature spread expected by early Monday as exposed ridges fall only into the upper 50s to low 60s. If cooling conditions are perfect, coldest spots may dip just below 40 degrees as most recently observed on June 28.
Weather Discussion ( Cold Front )
A strong cold front for late summer is the main focus of this weather period, with a major air mass transition occurring during the weekend.
Looking At Mount Rogers – Mount Rogers NRA on July 20, 2017
Air temps will hold in the 50s on highest peaks from the High Knob Massif to Mount Rogers during the day Saturday ( illustrating the early autumn-like nature of this upcoming air mass change ).
NAM 12 KM Model Total Rainfall Forecast – Next 72 Hours
Some orographic forcing will develop as this cold front approaches, with potential to off-set the general trend of dryness observed during the past 30-60 days.
Although November-April is the prime orographic forcing season, with October & May often being months of transition, when large-scale storm systems develop pressure gradients that push upon the mountain terrain ( the mountains “push back” and generate torques on the atmosphere ), orographic forcing settings can and occasionally do develop during the convective season.
NWS Precipitation Anomalies And Estimated Coverage – Past 30 Days
Heavy to excessive rains to the north, with rising air from Ohio to Wisconsin, has aided summer dryness across much of Virginia, SE Kentucky, northeastern Tennessee and portions of North Carolina where air has been sinking by compensation ( couplets of rising-sinking air are common on both local and synoptic scales during the convective season, often dictating patterns of summer rain ).
This general pattern has been superimposed upon local dry-wet feedbacks, favoring large rainfall variations over short distances.
Measured Rainfall Since June 1
Clintwood 1 W: 5.94″ ( -2.83″ below 1981-2010 average )
Nora 4 SSE: 10.23″ ( Near To Above Average )
Summer 2017 rainfall has varied dramatically across Dickenson County, for example, with about twice as much falling upon Long Ridge of Sandy Ridge as in Clintwood since the beginning of June.
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 1-5
Although more summer certainly lies ahead, recent heat will be broken and a near to below average temperature pattern is currently predicted by the European ensemble MEAN during the next 5-10 days into early August.
European 51-Member Ensemble Mean 850 MB TEMP Anomalies: Days 6-10
