071817 Forecast

Mountain Area Forecast ( July 18-20 )

Overnight Into Tuesday Morning

Partly-mostly clear.  Areas of valley fog.  Light winds.  Temperatures varying from mid-upper 50s to lower 60s within cooler valleys to the middle-upper 60s.

Tuesday Afternoon

Partly to mostly cloudy skies.  A chance of hit-miss showers and thunderstorms.  Light winds.  Temps varying from the 70s in upper elevations to the mid-upper 80s.

Tuesday Night Into Wednesday Morning

Chance of a hit-miss evening shower or thunderstorm.  Hazy and humid with areas of valley fog.  Light SSW to W winds generally less than 10 mph on mid-upper elevation mountain ridges.  Temps in the 60s to near 70 degrees.

Wednesday Afternoon

Partly-mostly cloudy skies.  Hazy-humid.  A chance of hit-miss showers and thunderstorms.  WNW-NW winds 5-10 mph, with higher gusts ( especially on mountain ridges ).  Temperatures varying from 70s in upper elevations to the mid-upper 80s.

Wednesday Night Into Thursday Morning

Warm & humid.  A chance of hit-miss showers & thunder-storms.  NW-NNW winds 5-15 mph, with higher gusts, on middle-upper elevation mountain ridges-plateaus.  Temps in the 60s to lower 70s.

Thursday Afternoon

Partly-mostly cloudy skies.  Hazy & humid.  A chance of hit-miss showers & thunderstorms.  Winds NW-NNW 5-10 mph.  Temperatures varying from 70s in upper elevations to the mid-upper 80s ( warmer, as per each day, at low elevations south of the High Knob Massif and in the eastern Kentucky foothills and lower sections of the Russell Fork-Levisa Fork river valleys around Haysi and Grundy ).


Weather Discussion ( Dog Days )

The somewhat lower humidity of recent days is being replaced by a more humid air mass, with a dominant and deep NW-N flow regime aloft developing around a large heat dome centered over the central USA.

High-Elevation Meadow In High Knob Massif – Elevation 3900 feet – July 15, 2017
The afternoon MAX reached 70 to 74 degrees at highest elevations in the High Knob Massif on Saturday, July 15, as relatively pleasant weekend conditions were observed in the high country ( nocturnal low temps dropped to 50-55 degrees within high valleys ).
To the south, by contrast, weekend conditions remained hot in the Great Valley with upper 80s to lower 90s reported from Knoxville into the Tri-Cities.
Turk’s-cap Lilies ( Lilium superbum ) Bloom In High Knob High-Country – July 15, 2017

Rainfall has been hit or miss during the past week, with a notable dry trend since the start of Meteorological Summer  ( on June 1 ) across much of the Cumberland Mountains, at least relative to what is average for this time of year.

National Weather Service Rainfall Analysis – Past 7 Days
Note heavy, locally excessive, rains to the north across Indiana and Ohio as thunderstorm clusters moved around the periphery of heat last week.  Rain was locally heavy across Dickenson-Buchanan counties & adjoining locales in eastern Kentucky and southern West Virginia as a front passed during the July 13-14 period.
Although 1.25″ of rain fell in Clintwood during July 14, only 5.26″ have been measured since June 1 ( 2.14″ below the 1981-2010 avg. ), which is also about the same as observed at Big Cherry Lake Dam.  A total of 7.68″ have been measured at Nora 4 SSE on Long Ridge of Sandy Ridge, in between these two sites, to illustrate the hit-miss nature of Summer 2017 convection.
USA Water Vapor Image At 1:15 AM on July 18, 2017
A upper low over central Virginia-North Carolina will be pushed eastward as the heat dome initially expands, with deep NW-N flow aloft that may carry debris cloudiness from thunderstorm clusters forming on the periphery of blazing heat over the Upper Midwest.

A hit-miss pattern of convective activity is expected to continue as heat builds through the remainder of this work week.  Changes will be possible by this weekend into next week, especially, as troughing develops aloft and monsoon moisture continues to flow around the big heat dome.

European 51-Member Ensemble MEAN 500 MB Height Anomalies: Day 1-5

An increasing potential for showers-thunderstorms will occur over time with a retrogression of the heat dome core, especially by later this weekend into next week ( this is the current ensemble trend ).  Stay tuned for updates.

European 51-Member Ensemble MEAN 500 MB Height Anomalies: Days 6-10