Weather conditions for the 7th Annual Hellbender 10K will be nearly ideal this year, with light southwest winds and seasonally chilly conditions under partly to mostly sunny skies (featuring fair weather cumulus).
Frosty cold sunrise conditions in the Norton Valley will warm quickly through mid-morning. Air temperatures in the 40s (4° to 9° Celsius) can be expected along the course that follows a 10:00 AM start time Saturday.
Expect air to dry with increasing elevation. A drop in relative humidity values will occur above the valley floor, toward the summit level of the massif, through mid-morning into mid-day Saturday.
Mountain Valley Frost
Areas of frost were featured in colder valleys Friday morning, such as in the Norton Valley which had temps analogous to the summit level of the High Knob Massif (the main difference being low-mid 30s accompanied wind chills in the 20s at the summit).
NOTE: Significant differences are typical on these mornings between the Norton Valley and adjacent Wise Plateau, with colder temperatures and enhanced frost on the floor of the Norton Valley (including the Big Laurel to Esserville and Ramsey to Tacoma corridors), and low spots within the plateau, often contrasting with milder, frost-free conditions in exposed locations of the Wise Plateau and higher places within the City of Norton.
Forecasters should not confuse Norton with Lonesome Pine Airport in Wise (especially for those following obs), as they are within two distinctly different topographic settings with significant weather contrasts on nights featuring radiational cooling and cold air drainage.
The Norton Valley is influenced by cold air drainage from both the High Knob Massif and northeastern end of the Black Mountains versus the Wise Plateau which features only localized drainage into lower sections, especially those once known as The Big Glades.
Latent heat of condensation associated with fog formation will help to prevent or minimize any frost formation along major river valleys and near the larger, lower-elevation lakes.
River valley fog will continue to be a nocturnal feature, as typical at this time of year, to contrast with below freezing conditions developing overnight into Saturday morning within the colder, high elevation valleys from the High Knob Massif to Burkes Garden.
Cooler-Drier Than Normal Short-Term
Generally cooler and drier than average conditions will continue to dominate the short-term forecast period into next week, when a warming trend develops.
A drier pattern is very welcome in wake of wetness, with the past year featuring 100.29″ of total precipitation at Big Cherry Lake Dam in the High Knob Massif.
The first major cold front of the autumn season to transport polar air southward will begin impacting the mountain area Monday Night into Tuesday. A marginal risk of severe storms will be possible along and just ahead of the cold front.
While localized showers and areas of drizzle will be possible Monday, the main shield of rain-embedded thunderstorms will spread across the mountains Monday night. Downpours and a sharp drop in temperature are expected overnight as winds shift northerly into Tuesday morning.
Be alert for water level rises and ponding of water within poor drainage, low-lying locations overnight into Tuesday morning
Cloud bases are expected to lower on upsloping winds that will shift northerly behind the cold front, with lifting of moist air up across middle-upper elevations along and southeast of the Virginia-Kentucky stateline (especially in locations along and N-NW of the High Knob Massif-TN Valley Divide).
ALERT For Dense Fog Development Tuesday At Middle & Upper Elevations Along-North Of The High Knob Massif-Tennessee Valley Divide On Upsloping Northerly Winds
Expect temperatures mainly in the 40s to around 50 degrees at mid-upper elevations Tuesday in locations along and north of the High Knob Massif-Tennessee Valley Divide (with colder wind chills at higher elevations)
In the wake of general 1.50″ to 2.00″ rains over the high country there was an array of orographic and lenticular cloud formations.
Watch the right, sunset lit side of the slides during the darker images around sunset to best see stacked, lenticular mountain waves that are nearly stationary and extend across a much larger portion of the massif (opening slides show lingering, orographic cap clouds in wake of rains).
Remnant rains of Beta pushed the 12-month precipitation total at Big Cherry Dam to nearly 100.00″ (98.89″), which may be broken by the end of September.
Rainfall late Thursday Night into early Friday is expected to become enhanced as tropical moisture interacts with the right-rear entrance region of a strong jet streak aloft.
*Looking ahead, to the end of September and early October, an early winter-like pattern will be taking shape with much below average temperatures looking increasingly likely across the eastern portion of the USA.
While the GFS Ensemble pattern is impressive, the European Ensemble Mean is even colder and more impressive for the first few days of October. Air becomes so cold, in fact, that the first flakes of snow may fly along the Appalachians (especially at upper elevations) if the ECMWF ensembles are on target.
Certainly this would not be that unusual for the mountains, with accumulating snow common at upper elevations in the High Knob Massif during October (strong cold air intrusions being detrimental to autumn color along highest crestlines).
At the least, a pattern favorable for widespread frost and freezing temperatures will be developing into early October.
ALERT For The Potential Of Excessive Rainfall Into This Weekend
Previous Discussions
More than 2.00″ of rain fell in the Pound area of northern Wise County (2.28″ measured in Pound Gap near U.S. 23) late Wednesday, beneath slow moving thunderstorms.
Heavy rain potential will continue through this upcoming weekend, with excessive local rain amounts being likely.
This is part of a stormy, late summer pattern that is expected to continue through the next one to two weeks (reference increasing upper air trough formation over the eastern USA on these mean, 51-member European Model forecasts).
Derecho Recap_10 August 2020
An event that sparked my interest in weather as just a kid was associated with a gustnado that formed along an outflow boundary. I have been interested in these types of events ever since. The following links highlight what will be recorded as a historic Derecho event.
At least 10 Million acres of corn in Iowa alone, were destroyed by a classic Derecho that blasted across the Midwest on 10 August 2020.
This is estimated to represent more than 1 Billion bushels of corn and a loss of at least 3.4 Billion dollars (just in Iowa). This Derecho impacted more than 800 miles of varied landscapes, much of it in the nation’s heartland.
The peak recorded wind gust reached 112 mph in Cedar Rapids, Iowa.
Corn can be seen in a portion of Nick’s video, as part of a live broadcast associated with KGAN-TV during the event. A link to the full broadcast is below:
At this time, weakening is expected, however, this must be closely monitored and a severe potential will exist until it is seen that the system dissipates upstream of the local mountains. A right turn into most unstable, energy-rich air toward western and central Kentucky is likely.
Wind damage often continues as the system weakens with a downward transfer of high momentum air to the surface, such, that I include this in the term “dissipates” that extends somewhat beyond disappearance of stronger radar echoes.
It appears that locations toward Cumberland Gap will be at higher risk, versus locations to the north and east, but please stay tuned to NOAA weather radio and your favorite media sources for updates on this evolving situation.
Showers and thunderstorms Monday will initially impact southwestern portions of the region, with a general east to northeast expansion of the impact zone from Tuesday into mid-late week.
While the placement of heaviest rain varies on nearly every model run, the idea of locally heavy to excessive amounts in localized places is what needs to be monitored.
Development of upper-air troughing over the eastern USA, in combination with a break in the heat ridge across the Deep South, will support increasing chances for showers & downpours in thunderstorms through mid-late week.
A late summer weather pattern, with daily chances for showers and local downpours in thunderstorms (mainly hit or miss during afternoon and early evening hours), will continue through coming days.
A notable difference being cooler temperatures, versus average, for this time of year, with more typical August heating not returning until later this weekend into next week when the atmosphere expands vertically.
Tropical Storm Isaias, which is likely to become a hurricane once again, will dominate regional weather conditions through early this week.
Although wind shear will increase again beyond 24-hours, Isaias is in position for intensification late Sunday and will later develop more extensive impacts due to enhanced upper-level divergence within the right-rear quadrant of a upper-level jet streak.
Isaias will become absorbed, or partially absorbed, into a upper-level trough, the axis of which (below) was over the Mississippi River Valley at 8:00 PM Sunday, and will become a more potent weather maker for the entire expanse of the eastern seaboard Monday into Wednesday. Isaias will be a potent rain producer given upper-level divergence aloft lifting tropical moisture vertically above a major population corridor.
I like the European Model and its ensemble mean best for handling of the upper-level dynamics, although both the GFS and high-resolution NAM are in general agreement, with indirect rain and thunderstorm development likely in the southern-central Appalachians.
With deep low pressure (Hurricane Isaias) moving across the eastern Carolina’s and Virginia, inflow and terrain convergence, in association initially (at least Monday) with upper-level divergence, will favor shower and thunderstorm development along both flanks of the Appalachian chain.
Locally strong-severe thunderstorm development will be possible.
Stay tuned to NOAA Weather Radio and your favorite media sources for possible alerts and warnings which may be needed through early this week.
*An Enhanced Flash Flood Risk Is Expected Thursday Into Friday (30-31 July 2020)
3:00 PM Update_Friday_31 July 2020
Thunderstorms developing over central portions of Kentucky and Tennessee represent the next wave to impact the mountains into late afternoon-evening.
A southwest to northeast corridor with a heavy to excessive rainfall potential will be present into this evening and night.
A boundary from the Kentucky Foothills into the mountains along the Virginia-Kentucky border will need to be closely monitored for the potential of enhancement and training.
Antecedent Conditions = Run-off & Saturated Soils
Heavy rains have Big Cherry Lake overflowing, and water gushing through South Fork Gorge, following a dry first-half of July that dropped the lake level 2 feet below its spillway (this rise represented more than 75 Million gallons of water gained in the lake, and much more within the basin_not including overflow).
A total of 5.62″ of rain fell at Big Cherry Dam during the 27-31 July period, including 1.66″ of overnight rain since midnight this morning (31 July).
A potential for locally strong-severe thunderstorms, in addition to the flood potential, will continue through this weekend.
Previous Discussions (Below)
Following Thursday afternoon convection, that dropped 0.98″ of rainfall in Clintwood and up to 1.75″ at Big Cherry Dam in the High Knob Massif (where orographic feeder clouds were present…see images), I am now monitoring the potential for new convection and heavy rains to develop into the overnight as orographic forcing increases on southwesterly inflow.
Doppler radar tends to under-estimate rainfall amounts when orographic pilatus clouds are present and capping the High Knob high country. Why? Because radar detectable rain drops falling aloft out of seeder clouds (be them thunderstorm towers or other nimbus types) become enriched by falling through thick terrain capping clouds = increased rain volume with more rain reaching the surface than detected by Doppler radar.
The problem at hand, then becomes one of a SW low-level jet of unseasonably strong winds (given this is the convective season when organized winds are lacking in the mean) that will push upon the terrain.
The high-resolution NAM is nearly identical to the latest 18z European Model in forecasting this first wave of enhanced winds, with additional jets of enhanced low-level wind predicted at times through the upcoming weekend.
Since air can not go downward into the solid ground, the only option will be an increase in surface-based upward vertical motion. Not be a problem in a stable air mass, but with any instability in a high (rich and tropical) precipitable water air mass there is the potential for trouble.
The mountains are not merely static entities, as they counter atmospheric pushing with a torque (in this case, it is a Positive Mountain Torque force).
The Bottom Line…Remain ALERT for the potential development of heavy rains into the overnight and Friday (day-time).
A surge in precipitable water values to well above 2.00″ in combination with SW-W low-level inflow and convergence along the mountains is expected to enhance the potential for heavy rain and thunderstorms Thursday into Friday.
The location of any flooding can not be known for certain until actual rain-thunderstorms develop.
A moisture rich air mass is expected to combine with a stalling frontal boundary, and waves of low pressure, to support repetitive rounds of showers & downpours in thunderstorms during coming days.
A main focus is expected to develop by late Thursday into Friday (30-31 July), with any accumulated rain prior to this period acting to increase soil moisture and the flooding risk.
While the NAM Model is faster than the European Ensemble Mean, there is general agreement in a heavy to excessive rainfall potential developing this week.
Part of a stormy pattern likely to continue during the first week of August 2020.
The core of a strong heat dome retrogrades into the southwestern USA as a positively tilted upper trough deepens over the eastern USA.
This locks in a stormy, wet weather pattern.
Weakening of the western extent of the Bermuda High ridge could be an ominous development (should it occur as now predicted) for tropical activity, and at the least an aid to the feed of deep, tropical moisture into the eastern USA.
All Conditions Are Connected
It is no surprise to residents that far southwestern Virginia and southeastern Kentucky are among the foggiest area’s in the United States, with nocturnal fog formation along river valleys nearly every night from summer into autumn within the ecologically diverse river basins forming headwaters of the Upper Tennessee, Upper Cumberland, and Upper Ohio river systems.
The moisture visible as fog may disappear from human sight, with a phase transition from liquid to vapor, but energy represented remains and more often than not helps to fuel development of day-time showers and thunderstorms.
This is all part of a positive feedback loop that plays a simply vital role in the summer precipitation and air temperature regime.
Afternoon air temperatures across Virginia during this time (below) varied from 60s in the High Knob Massif, and City of Norton, to around 100 degrees in the Tidewater of far eastern Virginia.
A heat dome will be expanding eastward across the USA this week into the upcoming weekend, with warm (upper elevations) to hot (lower elevations) mid-summer conditions.
Instability driven, hit or miss, showers and downpours in thunderstorms will begin developing by later this week into next week.
While instability driven convection is mainly diurnal, favoring day-time hours, clusters of storms that develop in a ring of fire pattern can occur at any time of day or night and often favor night-time hours when they can undergo up-scale growth with increased low-level inflow.
Clusters of organized thunderstorms developing along the edge of heat will also become possible. These are often called “Ring of Fire” storms.
July rainfall totals have varied from 0.50″ or less to more than 3.00″ during this first half of the month, with much of the region running below average.
Climate System Feedback Loops
Have you ever wondered or became frustrated by, especially as a farmer or gardener, the hit or miss nature of summer showers and thunderstorms?
While part of this reason is related to the natural, chaotic nature of thermal convection, it is also due to positive feedback loops that develop between the surfaces of Earth and the overlying atmosphere.
I first started looking at feedback loops in the 1990s, as part of the seasonal variability of summer-time convection across three-dimensional terrain of the Mountain Empire.
Whether it be the long-term climate system, or a short-term weather pattern, feedback loops are critical components that function to either amplify or dampen the response to forcing mechanisms.
Feedback loops, by definition, change the sensitivity of the response to forcing.
*In this way, it becomes easier to understand how a synoptic-scale pattern, conducive to either wetness or dryness, can become amplified by a positive feedback loop which is naturally unstable in that it acts to push a set of conditions farther away from the initial state over time (that is, wet ground may become wetter and dry ground drier as time passes).
*Nothing in the climate system is ever as simple as it might appear. That is certainly true within complex, three-dimensional terrain where any given system that may be able to generate orographic forcing could potentially overwhelm a positive feedback for continuation of dryness or wetness. Orographic forcing tends to be limited in both duration and strength during the convective (warm) season, but can occasionally become a significant factor in rainfall enhancement [especially over smaller temporal-spacial scales versus the orographic forcing (cold) season (Nov-April) when widespread regional impacts are common].
A simplified (+) feedback loop runs like this, an initial increase in rainfall leads to an increase in soil moisture, which acts to increase evaporation and transpiration (evapotranspiration) from surfaces into the overlying atmosphere where water vapor increases within the troposphere.
A water vapor increase then aids production of additional rainfall (via thermal instability and associated differential heating and latent heat release) to continue this positive loop for amplification of wetness.
On the other hand, an initial decrease in rainfall leads to a decrease in soil moisture, which acts to decrease (reduce) the rate of evaporation and transpiration from surfaces into the overlying atmosphere where water vapor decreases.
A decrease in atmospheric water vapor then acts to hinder production of rainfall to continue and amplify this positive feedback for dryness.
The solid black line connecting the Latent and Sensible heat flux boxes indicate that they are connected in the surface energy balance, and while a moist surface will be dominated by the latent flux and a dry surface by the sensible flux, in reality, they may both operate at the same time with varying magnitudes dependent upon the moisture present within a given location (as suggested).
If you are a student of climatology, you already know where this is heading. This simplified feedback loop (at the top) becomes complicated by fluxes of energy driven by solar radiation and phase changes of water (surface energy budget graphic).
While the overall feedback remains positive, I have included a couple of negative couplings between soil moisture and sensible heat flux as well as between latent heat flux and temperature.
When soil moisture is present, and especially elevated, some of the incoming solar radiation from the sun (called insolation) will be diverted and used for evaporating water and for driving transpiration through vegetation. In other words, a soil moisture increase will tend to amplify the latent heat flux and diminish (dampen) the sensible heat flux such that air temperature tends to be lowerwhen moisture is present for evapotranspiration.
When soil moisture is lacking, and especially decreasing, nearly all of the insolation from the sun will be applied to sensible heating of surfaces which then act to heat up the overlying air. So a lack of soil moisture increases the sensible heat flux, forming a negative coupling (blue arrow above graphic), and the sensible heat flux dominates the surface energy budget to cause air temperature to increase.
The bottom line, there is strong correlation between soil moisture and air temperature during summer, with dry ground tending to support hot temperatures and wet ground supporting cooler, but often more humid, conditions (hotter by daytime, as dry ground often supports cool nights, especially within the mountains)…such that positive feedbacks tend to exert significance influence upon summer-time weather conditions.
Upcoming Weather Pattern
A major weather shift has occurred during July, with a transition from cooler than average conditions (in the mean, below) during May and June giving way to above average July temperatures and a significant drying (above) of surface soils (in the mean).
NCEP/NCAR Reanalysis from the Climate Data Assimilation System (CDAS).
Although rainfall with an incoming front July 10-11 will be important, as well as rainfall next week, this generally sets the stage for the development of heat wave conditions heading into mid-July.
A heat dome core (5940 meters), recently centered southeast of the Four Corners, will be expanding eastward across the USA next week to generate unseasonably hot, mid-summer conditions.
Feedback loops, as described above, will enhance heating over locations that maintain dry surface conditions.
Soil moisture remains above average through a deep layer, but surface soil is drying significantly due to high sun angles (strong insolation) and much below average July rainfall (in the mean, some locations have observed average to above average rainfall).
A ring-of-fire convective pattern may eventually develop, otherwise, hit-miss instability driven convection will form along the mountains.
The extent of such activity, including of course, day-time cloud formations above the mountains, will determine how high temperatures get through next week and how much amplification will occur with positive feedback loops.
Some thunderstorms could become strong to locally severe, especially by later Wednesday into early hours of Thursday ahead of a strong front. Locally heavy rains will be possible from Tuesday evening through Wednesday evening.
*Localized, hit-miss activity Tuesday will give way to more widespread action along a cold front trailing from deep low pressure to the north Wednesday.
*Conditions will turn significantly cooler from Thursday into this weekend as upper air troughing develops once again, with coolest air (relative to average) centered over the Great Lakes initially.
This will mark the beginning of a cooler and wetter weather pattern that will become dominant from this weekend through much of next week (*).
*It should be noted that model trends are divided for next week, with some ensemble members showing above average rainfall while others predict below average rainfall.
The track and development of low pressure in upper levels of the atmosphere will help determine rainfall amounts. Either way, until a prolonged dry pattern does develop the flash flood risk will remain higher than average (especially in locations having had the greatest precipitation amounts this year).
An elevated flash flood risk will continue and need to be closely monitored.
Anomalously wet conditions observed during the past 6+ months have created flashy conditions in locations within and near the High Knob Massif, but the entire region will likely need to closely monitor conditions given current forecast trends.
Local flash flooding observed in recent weeks could become more problematic (impacting more people). Stay tuned for later updates into next week.
Previous Update
*ALERT For Elevated Stream Levels Along Big Stony Creek (Including Devil Fork) And The South Fork Of Powell River Into Saturday
Torrential rain producing showers and localized thunderstorms have dropped a general 1.50″ to 3.00″ of rain between Maple Gap and Osborne Gap this afternoon, including the peaks of Eagle Knob, High Knob, Little Mountain Knob, Huff Rock Knob and Thunderstruck Knob of Powell Mountain.
Some of the headwater creeks impacted include: Big Stony Creek, Benges Branch, Chimney Rock Fork, Clear Creek, Cove Creek, Devil Fork, Glady Fork, Lost Creek, Robinette Branch, South Fork of Powell River and Straight Fork.
Check for updated precipitation totals for 2020, including early June, at the above link during the next couple of days.
Warmer Then Cooler As Cristobal Passes
Large-scale sinking air will renew warming as Cristobal moves through a weakness in an upper air ridge pattern across the eastern USA into early next week. This is expected to initially lower rain chances and increase air temperatures across the mountains and adjacent regions.
Shower & thunderstorm chances will increase along a cold front attached to Cristobal remnants by the middle of next week. Significant cooling will then occur with upper air trough formation by later next week-weekend.
A W-WNW flow pattern will need to be monitored for the potential of thunderstorm cluster development heading into the middle of June, which will tend to form around a developing heat dome anchored over the central Plains.
Some of the wettest and most stormy conditions are expected to develop along a thermal gradient between blazing heat and unseasonably cool air, such that the ultimate position of this horizontal temperature gradient will be a key factor in where clusters of showers and thunderstorms develop. The placement of this thermal gradient, and heat dome core, is yet to be precisely determined.
Stay tuned for updates as details of this new pattern become more clear.
The coldest opening to a June on record in Wise was in 1966 with 31 degrees (that same morning featured 30 degrees in Burkes Garden).
The coldest opening to a June on record in Burkes Garden was in 1930 with 26 degrees, while the coldest on record in Canaan Valley (WV) reached 24 degrees in 1960.
While all-time record mins will remain safe, the coldest temperatures in several decades will be likely on early Monday this year, with coldest temperatures in the 30s amid high mountain valleys (widespread 40s to around 50 degrees within many other locations).
Light gradient winds, clear skies, and a unseasonably large 850 MB dewpoint depression will generate frost in cold air collecting basins at upper elevations from the High Knob Massif to Canaan Valley.
The northern frost pocket site in Canaan Valley, West Virginia will have a chance to drop into the 20s and approach the all-time record MIN for June 1 in Canaan Valley, and the all-time MIN for the month, which can be followed at this link.
Humid-Unsettled Pattern Ahead
Developing upper air ridging across the USA will feature a separation in the ridge over the Southeast and Gulf Of Mexico, increasing the opportunity for unsettled conditions and possible tropical develop-ment over the Gulf by later in this period.
A dramatic transition from unseasonably cool to unseasonably warm air will occur as this pattern develops, with hit-miss to widespread showers and downpours in thunderstorms becoming likely.
*High water levels will continue along Big Stony Creek, Little Stony Creek, South Fork of Powell River and other steep creeks draining the high country along the Wise-Scott-Lee border area, as well as portions of Black Mountain, into today (Monday, 25 May 2020).
*A warm, moist air mass will dominate the mountain region through this week with hit-miss showers and downpours in thunderstorms.
The potential for local high water will continue with development of torrential rain producing showers and thunderstorms. Folks living and driving along streams and within flood prone locations should remain alert for the potential of rapid water level rises. This includes those hiking in remote locations of the High Knob Massif and Jefferson National Forest.
*An increase in moisture in advance of a strong cold frontal boundary, which may in part be contributed to by tropical moisture transport, will increase the coverage of showers-thunderstorms later this week into the early weekend.
*Much cooler air is being monitored for later this weekend into early next week during the transition into Meteorological Summer and the month of June.