Unseasonably warm and dry conditions will dominate the first day of racing on October 7, which will include all of the High Knob Hellbender 10K and the first day of Cloudsplitter races ( which extends through Sunday ).
Friday Night Into Saturday Morning
Partly-mostly clear ( high clouds possible ). Becoming gusty higher elevations. SSE-SSW winds increasing to 10-20 mph, with higher gusts, into the overnight-morning. Temps from 40s in cooler mountain valleys ( sheltered from winds ) to mid-upper 50s to around 60 degrees on exposed middle-upper elevation mountain ridges and plateaus.
The race period is only now ( Oct 4 ) coming into range of high resolution forecast models; therefore, I will begin to update this through coming days with more details that will extend through the entire race periods.
Currently it is clear that a surge of unseasonably warm air will be felt through Saturday in advance of another change back into unseasonably cool conditions by middle portions of next week.
What is uncertain, and will have to be updated, is how will a developing tropical system in the Caribbean-Gulf of Mexico impact the mountains by Day 2 of the Cloudsplitter. Stay tuned for updates as new data gets incorporated into forecast models during the next couple of days.
An Autumn Cold Front And Developing Tropical System Are Being Monitored For Possible Impacts Upon The Mountain Region By Later This Weekend Into Early Next Week ( October 8-10 )
Details on this setup are yet to be worked out, with the Tuesday night run of the operational European Model trending east to keep significant rains along and east of the mountains ( from the Blue Ridge east to southeast ). This is in contrast to the U.S. GFS Model, and most hurricane models, which track the tropical system much farther west. Timing of an approaching cold front and upper air trough will help determine where the tropical system goes and how any linkage between it and the frontal zone develops.
A shot of unseasonably cool air will likely follow whatever happens with this tropical system by the middle of next week. Stay tuned for updates.
Overnight Into Wednesday Morning
Mostly clear. Light winds, except SSE-SSW at 5-10 mph, with some higher gusts, on mid-upper elevation mountain ridges. Large vertical temperature spread between colder mountain valleys and milder ridges. Temperatures varying from upper 20s to middle 30s in colder valleys to the upper 40s to lower-middle 50s on exposed ridges-plateaus. Areas of fog along major rivers.
Wednesday Afternoon
Mostly sunny. Light winds. Temperatures varying from mid-upper 60s in upper elevations to the mid-upper 70s. Warmer south into the Great Valley and river valleys.
Wednesday Night Into Thursday Morning
Mostly clear. Light winds. Large vertical temperature spread between colder mountain valleys and exposed ridges and plateaus. Temps varying from 30s in the colder valleys to the lower-middle 50s on exposed ridges-plateaus. Areas of river valley fog.
Thursday Afternoon
Mostly sunny ( some high clouds ). Light northerly winds. Temperatures varying from 60s in upper elevations to the mid-upper 70s ( warmer south into the Great Valley ).
Thursday Night Into Friday Morning
Mostly clear. Light winds. Large vertical temperature spread between colder valleys and exposed mountain ridges and plateaus. Temperatures varying from 30s to lower 40s in colder mountain valleys to the low-mid 50s on exposed ridges and plateaus.
Friday Afternoon
Partly-mostly sunny ( high clouds ). Unseasonably warm. Light southerly winds. Temperatures varying from upper 60s to lower 70s in upper elevations to the upper 70s to lower 80s ( warmer south into the Great Valley ).
Friday Night Into Saturday Morning
Partly-mostly clear ( high clouds possible ). Becoming gusty higher elevations. SSE-SSW winds increasing to 10-20 mph, with higher gusts, into the overnight-morning. Temps from 40s in cooler mountain valleys ( sheltered from winds ) to mid-upper 50s to around 60 degrees on exposed middle-upper elevation mountain ridges and plateaus.
The first full moon closest to the Autumnal Equinox is always called the Harvest Moon, for times when farmers and Native Americans used moonlight to gather in late season crops. Although not quite full yet, the moon early on October 4 was getting close in the chilly air filling mountain valleys of the Cumberland Mountains.
Harvest Moon Above The Cumberland Mountains – October 4, 2017
While it is looking to be unseasonably warm and continued dry for the High Knob Hellbender 10K race on Saturday, the second day of the Cloudsplitter 100 is more uncertain and will depend upon what happens with a developing tropical system in the Gulf of Mexico.
Changing Seasons In The High Knob High Country
Ensembles of the GFS Model have been farther west than the mean of the 51-Member European Model group. Right now the bulk of hurricane models are also farther west.
Hurricane Spaghetti Model Track Forecast – 8 PM Tuesday Run ( Oct 3 )
I think the setting will become more clear once hurricane hunter data and other data being collected gets put into the models during the next couple of days. A track like above would tend to spread heavy rain across all of the southern-central Appalachians, while a track like the current run of the Operational European Model would keep heavier rains mainly along and east of the Blue Ridge.
An ALERT For Cold Night-time Conditions In Mountain Valleys Continues, With Large Vertical Temperature Spreads Between Ridges & Valleys
While foggy river valleys and exposed mountain ridges-plateaus will remain well above freezing, a very dry air mass will continue to support both large diurnal temperature spreads and also large vertical differences between ridges and mountain valleys.
Colder valleys will continue to drop into the 30s, with local below freezing conditions expected through mid-week ( Wednesday AM of October 4 ). Reference observed minimums reported along the Appalachians on Sunday AM of October 1 in my discussion below.
Overnight Into Monday Morning
Partly to mostly clear ( high clouds ). Breezy to gusty SE winds of 10-20 mph, with higher gusts, through early to mid-overnight on mid-upper elevation mountain ridges before decreasing during the predawn. Large vertical temp spread between colder valleys and milder ridges-exposed plateaus. Temps varying from 30s in colder valleys to the mid-upper 40s to around 50 degrees on exposed ridges and plateaus ( except for a rapid temperature drop to around or below freezing in high valleys during the predawn-early morning ). Local areas of dense river valley fog along major rivers. Wind chills in the upper 30s to lower 40s in gusts along high mountain crest lines.
Monday Afternoon
Partly sunny ( high clouds ). Light SE to SSE winds. Temperatures varying from low-mid 60s in upper elevations to the low-mid 70s.
Monday Night Into Tuesday Morning
Partly-mostly clear ( high clouds ). Light winds, except SSE-SSW at 5-10 mph on mid-upper elevation mountain ridges. Large vertical temperature spread between colder valleys and milder mountain ridges. Temperatures varying from upper 20s to upper 30s in mountain valleys to the upper 40s to lower 50s along mountain ridges-exposed plateaus. Fog along major river valleys.
Tuesday Afternoon
Mostly sunny ( some high clouds possible ). Generally light winds. Temperatures varying from low-mid 60s in upper elevations to the lower-middle 70s.
Tuesday Night Into Wednesday Morning
Mostly clear. Light winds, except SSE-SSW at 5-10 mph, with some higher gusts, on mid-upper elevation mountain ridges. Large vertical temperature spread between colder mountain valleys and milder ridges. Temperatures varying from 20s to middle 30s in colder valleys to the upper 40s to lower 50s on exposed ridges-plateaus. Areas of fog along major rivers.
Weather Discussion ( WxDiversity )
Autumn has arrived in the mountains. This combined with a recent streak of dryness will enhance diversity in weather conditions, both from day-to-night and also ( as typical of this time of year in the mountains ) between ridges-valleys.
Rugged Stone-Pickem Mountain of High Knob Massif – September 30, 2017
The following temperatures are mostly NWS Cooperative sites, with a few Weatherbugs added ( note Weatherbug sensors are typically mounted much higher than the standard 4-6 feet height of official thermometers ).
Western North Carolina Jefferson: 31 degrees Boone: 35 degrees Spruce Pine 4 ENE: 39 degrees
West Virginia Bartow: 29 degrees Hacker Valley: 31 degrees Frost 3 ENE: 32 degrees White Sulphur Springs: 32 degrees Lewisburg: 33 degrees Beckley: 34 degrees
Areas of valley frost were widespread across Wise and Dickenson counties, away from river valley fog, early October 1 and no doubt were also in many other places located within the mountains. Coldest high valley sites, outside of Burkes Garden, of Canaan Valley and the Big Cherry Basin in the High Knob Massif are not even yet included in this list ( that data yet to be collected ).
Valley frost is typically observed when air temperatures at standard NWS sensor height of around 5 feet reach the middle 30s since air temperatures right at ground level are generally colder. Frost occurred in the Clintwood area, for example, with a MIN air temperature of 34.8 degrees at the 5 foot sensor height.
Brilliant Color In Flag Rock Recreation Area – September 30, 2017
Another interesting feature is wind chills along the high mountain crest lines. This is being caused by a compression of thicknesses by night + a pressure gradient around a High currently centered over Pennsylvania.
If anyone doubts that nocturnal wind chills are a factor, then just drive up to the High Knob Lookout and that doubt will be quickly eradicated. Winds relax into the day as thicknesses increase.
NAM 12 KM Model Mean Sea Level Pressure-Streamlines at 8 PM October 1
This type of setting is not ideal for coldest conditions in the higher mountain valleys; however, a relaxation during pre-dawn and sunrise periods is enough to allow for rapid temp drops in the favored frost pockets ( where temps often drop below surface dewpoints reported at any given time ).
Black Mountain Mesonet at 12:55 AM Monday – October 2, 2017
Wind chills in the upper 30s to lower 40s are being observed along high mountain crest lines, especially in the frequent gusts. This low-level jet setting weakened into morning hours of October 1 and will likely weaken again into this morning ( October 2 ).
If the High center slides a little more southwest, allowing the nocturnal pressure gradient to weaken, conditions will actually become more favorable for cooling within the high mountain valleys into Tuesday and Wednesday mornings. Therefore, I have continued the alert for cold nights since no official advisories have been issued.
European Model 51-Member Ensemble Mean 500 MB Height Anomalies: Days 0-4
While there is little to no chance of rain this week, there are signs of important changes ahead that could break this dry streak out in the 5-10 day period ( below ) as eastern USA ridging ( above ) breaks down.
European Model 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
Meanwhile, it will be wise to avoid any outdoor burning.
