Heavy To Excessive Rainfall Will Be Possible At Times This Week Amid A High Moisture Content Air Mass
The Storm Prediction Center Has Updated For A Slight To Marginal Risk For Severe Thunderstorms Between 8:00 AM Thursday and 8:00 AM Friday ( July 14-15 )
*A Marginal Risk is currently forecast to continue through Friday into early Saturday from the Cumberland Mountains southward.
Storm Prediction Center Updated Risk – 8 AM Thursday To 8 AM Friday ( July 14-15 )Storm Prediction Center Updated Discussion
A heavy to excessive rainfall potential will continue to be a weather concern in coming days, along with the potential for strong-severe thunderstorms by late week ( July 14-15 ). A front is likely to stall across the area by this weekend to continue the daily chance for showers & thunderstorms.
**Depending upon where the boundary stalls, an increased risk for heavy-excessive rainfall may arise by late Friday into Saturday as very light winds develop aloft for slow storm motion on anything that develops.
Overnight Into Tuesday Morning
Partly to mostly cloudy with a chance of hit-miss showers and thunderstorms. Areas of dense fog. SW to WSW winds 5-10 mph on mid-upper elevation mountain ridges. Temps in the upper 50s to mid-upper 60s ( mildest along exposed middle-upper elevation ridges and plateaus ).
Tuesday Afternoon
Showers & downpours in thunderstorms becoming likely. SW winds 5-15 mph, with higher gusts. Temperatures in the 60s to lower 70s in upper elevations to the mid-upper 70s ( warmer south toward the Tri-Cities ).
Tuesday Night Into Wednesday Morning
Chance of a shower or thunderstorm. Areas of dense fog. Winds WSW-WNW at 5-15 mph, with higher gusts, along middle-upper elevation mountain ridges. Temperatures widespread in the 60s.
Wednesday Afternoon
Chance of showers & downpours in thunderstorms. Humid. Winds SW-W at 5-10 mph, with higher gusts. Temperatures varying from 70s in upper elevations to the low-middle 80s ( warmer south toward the Tri-Cities ).
Wednesday Night Into Thursday Morning
Chance of showers & thunderstorms. Humid & hazy with areas of dense fog. SW-W winds 5-15 mph along mid-upper elevation mountain ridges. Temps in the 60s to lower 70s.
Thursday Afternoon
Showers & thunderstorms likely. Some storms may be strong to severe. Winds SW-WSW 5-10 mph, with higher gusts. Warm & humid with temperatures varying from 70s in upper elevations to the 80s across low-middle elevations.
Thursday Night Into Friday Morning
A chance of showers & thunderstorms, especially during the early evening. Areas of dense fog. Winds SW-W 5-10 mph on mid-upper elevation mountain ridges & plateaus. Mild with temperatures in the 60s to around 70 degrees.
Weather Discussion ( July 9-14 )
Thursday Overnight Notes
For days now models have been showing a very unstable air mass developing across the mountain region on Thursday, with high CAPE and low LI values combined with a bounty of moisture for potential water loading of downdrafts.
Debris clouds from upstream convection or early development of clouds-storms over the mountains could alter this by keeping the air cooler and more stable. Something that will have to be tracked through Thursday into Friday to see how it unfolds.
NAM 12 KM Model Forecast CAPE & Mean Sea Level Pressure – 8 PM Thursday
It is hard to conceive that at least a few storms will not go severe, or be very strong, amid this type of air mass. The main thing that is needed will be a trigger to initiate convection, with the terrain plus outflow boundaries from activity to the northwest & north as well as an actual surface boundary all being potential low-level triggers for convective firing.
NAM 12 KM Model Precipitable Water Forecast – 8 PM Thursday ( July 14 )
Although downpours will certainly occur with any storms Thursday into Friday, the late Friday into Saturday period is currently catching my eye as parameters for local areas of heavy-excessive rainfall will increase.
Forecast Skew-T Above Wise County At 8:00 AM Saturday – July 16
Mean winds aloft drop under 10 knots by later Friday into Saturday within the surface-8 km layer as air remains very moisture ( 1.50″ to 2.00″ of precipitable water ).
Stay tuned to NOAA Weather Radio and your favorite media sources for possible watches and/or warnings that may be needed during the Thursday-Saturday period of July 14-16.
Previous Discussion
Gorgeous weekend conditions graced the Cumberland Mountains with day-time MAXS in the 70s to lower 80s coupled with nights in the 50s and 60s.
Majestic Big Cherry Lake of High Knob Massif – July 9, 2016
I measured 4.10″ of rain at Big Cherry Lake Dam on Saturday, which had fallen during the previous week, amid frequent showers and downpours in thunderstorms.
*The lake level was still below the Dam spillway with 127+ Million gallons of water having been released from the lake during June to augment flow on the Powell River ( allowing room for the lake to still hold back run-off ).
Black Mountain MesoNET – Daily Climate Data For July 1-10, 2016
Temperatures at highest elevations barely broke 70 degrees on Saturday & Sunday ( July 9-10 ), with 71.8 degrees being the weekend MAX observed at 4031 feet on Black Mountain.
Rugged Pickem-Stone Mountain of High Knob Massif – July 9, 2016
Although several trees were blown down in the area the damage was spotty in nature and not widespread, as was the case for folks lee of the mountains in the Great Valley.
NAM 4 KM Model Total Rainfall Forecast Next 60-Hours – AM July 11 Run
Some gully washing downpours have been observed Monday, with a much better coverage of showers & downpours in thunderstorms expected to develop Tuesday and periodically there-after during the remainder of this week-weekend and likely into next week.
NAM 4 KM Model Total Rainfall Forecast Next 60-Hours – PM July 11 Run
Like last week, models continue to vary from run to run on where and how much rain will fall. A repetitive pattern in a high moisture content air mass suggests some places will receive heavy to locally excessive rainfall.
Observed Composite MEAN 500 MB Pattern During June 22-July 9, 2016
The pattern during Summer 2016 ( June-July ) has been very consistent, especially since mid-late June, with a 500 MB air flow pattern very close to what MEAN 51-Member European Ensembles are forecasting during the next 10 days.
European Ensembles MEAN 500 MB Forecast – DAYS 1 to 5
This being especially true if combining DAYS 1-5 with DAYS 6-10, such that the MEAN is very close to the Observed Composite MEAN graphic illustrated above for the June 22 to July 9 period.
European Ensembles MEAN 500 MB Forecast – DAYS 6 to 10
The notable difference being a vertical expansion of the atmosphere across the nation as we enter what is often, climatologically at least, the hottest part of summer.
Observed Composite MEAN 850 MB TEMP Anomalies – June 1 to July 9
The hottest conditions so far during Summer 2016 ( above ) have been centered over the central-western USA, with a general W-WNW-NW flow into this region.
European Ensembles Composite MEAN 850 MB TEMP Forecast – DAYS 1-5
This type of pattern is forecast to continue during the next 10 days, with tendencies for increasing NW flow during the 5-10+ day period. This implies that more organized clusters of thunderstorms will become likely, some with a damaging wind potential to accompany heavy rainfall during the mid-late July period.
European Ensembles Composite MEAN 850 MB TEMP Forecast – DAYS 6-10
NOTE I use the MEAN of the 51-Member European Ensembles since they are BY FAR ( and have been ) the most stable outward in time, and nothing suggest’s that they will not continue to be.
Part of, or superimposed upon, the above pattern has been developing drought across the southeastern USA into the Tennessee Valley and southern Appalachians.
*Differences being locally exemplified by nearly as much rain in the High Knob Massif since May 1 ( beginning of the convective season ) as observed in the Tri-Cities during the entire year.
USA Drought Monitor As Of July 5, 2016
The Bottom Line…Although there are always waxes and wanes that force daily weather changes, the big picture or synoptic-scale pattern remains consistent this summer and suggests that more of the same is upcoming for the mountain region during mid-late July. This being superimposed upon drought that is trying to spread across the Deep South into parts of the Mountain Empire, as much wetter conditions and cooler mean temperatures continue from the local mountains ( High Knob Massif ) northward.
Meso-scale Notes On Monday – July 11, 2016
High Knob Massif Webcam – University Of Virginia’s College At Wise
The High Knob Massif has acted as a cloud generation zone for booming thunderstorms, with gully washing rain, that have been over the adjacent Tennessee Valley Divide ( along the border of Wise and Dickenson counties ).
Note how the clouds in these individual frames can be seen extending back to the summit region and heads of the High Knob Lake, Big Cherry Lake, and Norton Reservoir’s basins.
High Knob Massif Webcam – University Of Virginia’s College At Wise
An example of how wetness over the massif feeds into the over-lying atmosphere to develop towering clouds that go along with the atmospheric steering flow field to rain upon adjacent locations ( it happens all the time, but this is a nice current example that is visually obvious ).
*Total precipitation for 2016 has now reached around 40.00″ in the High Knob Massif versus less than 20.00″ for portions of the Great Valley only 30-35 or so air miles toward the south.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Any doubts about the massif impacting air flow can be eradicated by noting these nice lenticular mountain waves forming amid the wake zone ( fishtails on some above and stacked below ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
A really nice NASA visible showing clouds literally arising from the crest zone of the High Knob Massif and streaming across the southern portions of Dickenson and Buchanan counties into the extreme southern portion of West Virginia.
