An ALERT For Local Downpours Of Heavy Rainfall Continues Through Friday Afternoon
A high water content air mass will continue over the mountain area into Friday afternoon. Showers & downpours with heavy to locally excessive rainfall will remain possible before much drier air overspreads the Cumberland Mountains by Friday night into Saturday morning. A beautiful weekend is expected.
Overnight Into Friday Morning
Hazy & humid. Areas of dense fog ( widespread at highest elevations within orographic clouds ). Chance of showers & thunderstorms, especially toward morning. Downpours possible. SW-W winds 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges. Temperatures widespread in the 60s to lower 70s.
Friday Morning Into Friday Afternoon
Humid. Showers & thunderstorms likely. Local downpours. Low clouds with dense fog at highest elevations. Becoming partly cloudy and less humid by late afternoon into early evening. Winds shifting W-WNW at 5-10 mph, with higher gusts. Temperatures varying from upper 60s to lower 70s at highest elevations to the middle 70s to around 80 degrees. Warmer south into the Great Valley and Tri-Cities.
Friday Night Into Saturday Morning
Clearing and less humid ( especially in higher elevations ). Areas of dense valley fog. WNW-NW winds 5-10 mph and diminishing along all but highest ridges. Temperatures varying from lower 50s to the lower 60s ( coolest in high mountain valleys above 3000 feet ).
Saturday Afternoon
Partly sunny. Light SSW-WSW winds generally less than 10 mph. Temperatures varying from upper 60s to lower 70s at highest elevations to the upper 70s to lower 80s ( warmer south into the Great Valley and Tri-Cities ).
Saturday Night Into Sunday Morning
Mostly clear. Areas of dense valley fog. Light winds. Large vertical temperature spread developing between the cooler valleys and milder ridges. Temperatures varying from the upper 40s to lower 50s in coolest valleys to mid-upper 60s.
A more significant air mass change is being monitored for the final days of August, starting later next week, with potential for much less humid air and chilly nights. Stay tuned for updates.
Weather Discussion ( Jungle-like )
The mountain landscape during August 2017 has turned into a tropical, jungle-like state with very wet conditions featuring a daily array of downpours.
Month To Date National Weather Service and Estimated Rainfall Totals
*Automated Rain Gauge Totals ( August 1-17, 2017 )
Big Stony Creek: 8.27″
Dungannon: 7.98″
*Eagle Knob: 7.90″
*Robinson Knob: 7.21″
*Little Mountain: 7.10″
*Big Cherry Lake Dam: 7.04″
*Actual totals are greater, especially for rain gauge sites above 3000 feet in the High Knob Massif.
Month To Date National Weather Service and Estimated Rainfall Totals
Although coverage of heaviest rainfall amounts is greater than the above graphics indicate across southern Wise and northern Scott County, Va., they illustrate the general trend observed so far during August 2017.
NAM 12 KM Model Precipitable Water Forecast At 11:00 AM Friday – August 18
The current ( 11:45 PM Thursday ) presence of orographic clouds capping highest elevations within the High Knob Massif and Black Mountain, in advance of the approaching moisture plume ahead of a cold front, indicates that the potential for significant rainfall amounts must continue to be respected until drier air actually arrives later Friday afternoon-evening
Early morning to early afternoon is currently the period most favored for heavier rainfall with orographic enhancement.
Big Stony Creek of High Knob Massif – August 7 to August 18, 2017
Although dropping, stream levels remain high and swift on steep creeks draining the high country of the High Knob Massif. Please continue to use caution around these gushing whitewater creeks.
While humid, very moist air will continue to be felt into early Friday afternoon, a notable decrease in atmospheric moisture will occur by Friday evening into Saturday.
NAM 12 KM Model Precipitable Water Forecast At 8:00 PM Friday – August 18
The potential for a more significant air mass change, with an early autumn flavor, is being monitored for the final week of August ( the 5-10 day range at this point in time ).
European 51-Member Ensemble Mean 850 MB Temp Forecast: Days 6-10
