The Storm Prediction Center Has Issued A Marginal Risk Of Severe Thunderstorm Development Saturday
Friday Morning Through Friday Afternoon
Predawn rain showers and rain developing ( especially along and southeast of the High Knob Massif & Tennessee Valley Divide. Dense fog at highest elevations. Then partly cloudy with a chance of showers and thunderstorms this afternoon. Local downpours. SSW-SW winds 5 to 15 mph, with higher gusts. Temperatures varying from 60s to low 70s in upper elevations to the upper 70s to lower 80s.
Friday Night Into Saturday Morning
Chance of hit-miss showers or thunderstorms. Partly to mostly cloudy. Areas of fog. SSW-WSW winds 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges and plateaus. Mild with temperature widespread in the 60s ( upper 50s to lower 60s in cooler locations ).
A chance of showers & downpours in thunderstorms. Some storms could be locally strong-severe. SW winds 5-15 mph, with higher gusts. Temperatures varying from upper 60s to lower 70s at highest elevations to the upper 70s to low 80s. Areas of dense fog ( orographic clouds ) at upper elevations.
Saturday Night Into Sunday Morning
A chance of showers & thunderstorms. Winds shifting to WNW-NW at 5-10 mph, with higher gusts. Areas of fog, especially at high elevations. Temperatures dropping into the upper 50s to middle 60s ( coolest highest elevations ).
Intervals of showers & downpours in thunderstorms are expected through most of next week in advance of a stronger cold front that could again introduce much cooler air by the second week of July. Many dry hours are expected between active weather. Stay tuned for later updates on this future weather pattern.
Weather Discussion ( Back To Summer )
A return of humid air means that a return of more typical summer conditions, with intervals of showers & thunder-storms, will be a common feature of the forecast through the Independence Holiday period and next week.
Coldest mountain valleys along the Appalachians fell into the 30s, prior to this return of summer, with widespread 40s in other valleys across the Mountain Empire.
Coldest Mountain Valley Reports ( Morning Of June 28, 2017 )
Canaan Valley West Virginia 37 degrees
Burkes Garden Virginia 37 degrees
*Big Cherry Wetland Valley 38 degrees
A June 1-29 mean low temperature of 47.6 degrees was recorded in colder portions of the Big Cherry Wetland Valley ( 49.9 degrees in Burkes Garden during this same period ).
Following a very WET April-May, the month of June will end with near to below average rainfall. Many local locations are currently in the 3.00″ to 5.00″ rainfall bracket ( as of AM on June 30 ).
June featured a host of nice, chilly nights amid high valleys with 16 out of the 29 days of June featuring a 24-hour MIN which dropped below 50 degrees in the Big Cherry Lake Wetland Valley of the High Knob Massif.
Strong to possibly severe thunderstorm development will be possible Saturday, with formation west of the mountains tending to move eastward. Be sure to stay tuned to NOAA Weather Radio and your favorite media sources for any possible watches or warnings that may be issued.
Increasing overnight clouds. Small chance of a shower or sprinkle. Light NW-N winds increasing to 5-10 mph, with higher gusts, along mid-upper elevation mountain ridges. Temperatures in the upper 40s to upper 50s.
Tuesday Morning Through The Afternoon
Partly to mostly sunny. Small chance of a hit-miss shower or thunderstorm. Increasingly blue skies. NW winds 5-10 mph. Temperatures varying from low 60s to the lower 70s.
Tuesday Night Into Wednesday Morning
Clear. Large vertical temperature spread between colder mountain valleys and exposed ridges. Light winds. Temps varying from low-mid 40s valleys to low-mid 50s on ridges, except 30s in coldest valleys of upper elevations. Areas of locally dense river valley fog.
Mostly sunny. Mild. SSW-SW winds 5-10 mph, with higher gusts. Temperatures varying from 60s in upper elevations to the mid-upper 70s to around 80 degrees.
Wednesday Night Into Thursday Morning
Becoming partly to mostly cloudy. Becoming windy across higher mountain ridges. SSW-SW winds 5 to 15 mph, with higher gusts, on mountain ridges-plateaus below 2700 feet. SW winds 10 to 20 mph, with higher gusts, along mountain ridges above 2700-3000 feet. Temperatures from the upper 40s to middle 50s in cooler valleys during the evening to the upper 50s to mid 60s along gusty mountain ridges ( temps tending to rise overnight in many mountain valleys ).
A chance of hit-miss showers & thunderstorms. SSW-SW winds 5-15 mph, with higher gusts. Temperatures varying from low-mid 70s in upper elevations to the low-middle 80s.
A hit-miss pattern of showers and downpours in thunderstorms is expected to return for the close of June and opening of July, with increased humidity levels more typical of summer-time. A front stalling near the Mountain Empire will have to be monitored by this weekend into early next week.
Weather Discussion ( Chilly Valleys )
A welcomed and refreshing break from summer-time humidity levels is being enjoyed this week. Morning temperatures dipped to 48 degrees ( 47.6 ) in Clintwood Monday, with 40-45 degrees in colder mountain valleys.
Colder places in upper elevations will make a run at the 30s into Wednesday morning, when conditions for radiational cooling and cold air drainage ( with nocturnal inversions ) will rule mountain valleys in three-dimensional space and time. In other words, multiple inversions amid the vertical will develop from lower, into middle and upper elevations.
If any doubt this be true, merely check the recorded history in Burkes Garden where the past 121 years have illustrated that every single June night has experienced low temps in the 30s ( or lower ) at some point in time ( a MIN as cold as 26 degrees was recorded on June 1 in 1930, with 28 degrees as late as June 26 during 1935 ).
*The undergraduate field research project at the University Of Virginia’s College At Wise is illustrating that nocturnal minimums tend to run even colder than Burkes Garden within high valleys of the High Knob Massif ( at upper elevations above 3000 feet ).
The Cumberland Mountains were lucky, pure and simple, to have escaped flooding rains and wind damage ( minor tree damage occurred locally ) that occurred last week.
*An impressive 8.42″ rainfall total was recorded at the Morehead Airport in Rowan County, Ky., during last week ( June 18-24) with torrential rains prior to and during the remnants of Cindy.
The pattern continues cooler than average for this time of year during the next few days, with below average 500 MB heights centered on the Upper Midwest and Great Lakes.
The pattern gives way to one more typical of summer by this weekend into next week, and the Independence Holiday period, with rising 500 MB heights and temperatures.
Weak troughing in the upper air across the eastern USA indicates that the pattern will not get out of hand with heating during this period. Temperatures near to a little above average are currently being forecast by the MEAN ensemble guidance during the first week of July 2017.
A pattern typical of summer in the mountains is expected, with hit-miss showers & downpours in thunderstorms. The potential for more organized activity along any boundaries which stall will have to be respected amid an array of what is likely to be many dry hours in between active weather.
A Heavy Rainfall Potential ALERT Is Now In Effect For Friday Into Saturday For The Cumberland Mountains.
The Potential For Rock-Mud Slides & Flash Flooding Will Exist With This System In Locations Along And West Of The Appalachians.
A high water content air mass associated with remnants of tropical storm Cindy will be moving across the mountains during Friday into Friday Night-early hours of Saturday.
Observe wavy nature of clouds ( above ) over the High Knob Massif and the distinct band of clouds capping upper portions of the mass that helps to increase the volume of rain reaching the ground as drops fall from seeder clouds aloft ( radar beams overshoot these low-level orographic clouds and under-estimate the amount of rainfall reaching the surface over this complex terrain ).
Increasingly strong & gusty SW winds + the seeder-feeder precipitation process ( orographic cap clouds ) will enhance lift and rainfall production, with torrential rains likely at times as this system moves across complex terrain of the Cumberland Mountain Overthrust Block.
A very moist air mass + strong low-level S-SW flow will develop rain over the mountains during Friday, with a concentrated band of system rain expected by Friday Night into early hours of Saturday.
Forecast models, and Doppler radars, tend to under-estimate the amount of rain that falls in this type of setting ( with rainfall during Thursday being under-estimate over the Cumberland Mountains well in advance of this system and its deep moisture ).
*Doppler beams overshoot orographic clouds and also tend to under-estimate the fine droplet-rapid fall rate nature of tropical rains moving across complex terrain.
Residents living and driving through low-lying areas and along mountain streams need to remain alert for the potential of rapid water-level rises and changing conditions Friday into Friday Night-early Saturday.
The Storm Prediction Center Has Issued A Marginal To Slight Risk For Severe Thunderstorm Development On Friday Into Early Hours Of Saturday ( June 23-24 ).
Stay tuned to NOAA Weather Radio and your favorite media sources for possible warnings that may be needed during this event.
An ALERT For The Potential Of Gully Washing Rains In Showers And Thunderstorms Is Now In Effect For The Mountain Region & Cumberland Mountains
A muggy, high water content air mass will generate showers and downpours in drenching thunderstorms during the June 13-17 period ( in hit or miss fashion ).
Folks living and driving through flood prone, low-lying locations should be aware of an enhanced risk for heavy rainfall and significant run-off through coming days. Understand that a watch or warning may not be issued until an event develops over a localized area.
The potential exists for more widespread, organized activity later this week. Stay tuned to NOAA Weather Radio and your favorite media sources for updates.
A significant increase in moisture is expected by late Sunday into Monday, with showers and downpours in thunderstorms. Locally heavy rainfall amounts will be possible before much drier air returns by June 6.
Overnight Into Saturday Morning
Clear. Seasonally chilly. Large vertical temperature spread between colder mountain valleys and milder ridges. Light winds. Temperatures varying from 39 to 43 degrees in the coldest mountain valleys to the mid-upper 50s along milder mountain ridges. Areas of dense river valley fog.
Sunny. Beautiful blue skies. Light northerly winds. Temps varying from low-mid 70s in upper elevations to the lower to mid 80s.
Saturday Night Into Sunday Morning
Clear. Large vertical temperature spread developing between colder mountain valleys & milder ridges and plateaus. Light southerly winds along mid-upper elevation mountain ridges. Temperatures varying from 40s in the colder mountain valleys to the low-mid 60s on exposed mountain ridges. Areas of dense river valley fog.
Increasing clouds. More humid. A chance of showers and thunderstorms. Local downpours. SW winds 5 to 10 mph. Temps varying from low-mid 70s in upper elevations to the low-mid 80s.
Sunday Night Into Monday
Warm & humid. Showers & downpours in thunderstorms. Locally heavy rain amounts. SW-W winds 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges. Areas of fog, especially at upper elevations.
A period with showers and downpours in thunderstorms will be followed by another spell of below average temperatures ( chilly nights in mountain valleys ) next week ( as Florida turns wet ).
Weather Discussion ( Cool Nights )
A chilly night is underway in the mountains, with light winds and clear skies generating large vertical temperature spreads between colder valleys and exposed ridges.
Gorgeous blue skies observed Saturday afternoon indicated that low dewpoint air had advected into the mountain area. This sets the stage for coldest valleys to drop into the upper 30s to low 40s in contrast with 50s along exposed ridges and plateaus.
A very low precipitable water atmosphere ( above ) will be in place through Saturday into Sunday morning to allow for large diurnal temperature changes between night and day. Note the tropical moisture across the Gulf of Mexico and Florida.
A large diurnal ( day-to-night ) temperature spread will also be observed into Sunday, with rapid warming by day giving way to another significant temperature drop in mountain valleys during Saturday night into Sunday morning.
A significant increase in moisture is expected by late Sunday into Monday, with development of showers and downpours in thunderstorms ahead of a upper air trough and surface cold front. Much drier air is expected to then return by Tuesday ( below ).
This will mark the beginning of an unseasonably cool period, with more chilly nights in the mountains.
As I alluded to before, rising air in association with a plume of tropical moisture and deep convection across Florida and the Gulf Coast will contribute to this next cool period ( some may call it Elderberry Winter ) via synoptic-scale sinking of air ( subsidence ) over the southern-central Appalachians.