110417 Forecast

Mountain Area Forecast ( Nov 4-6 )

ALERT For Strong ( ROARING ) SW Winds At Mid-Upper Elevations Into Monday Morning In Advance Of A Line Of Showers-Thunderstorms.  Caution Is Advised.

Strong SW winds will continue to blow into the overnight ahead of an approaching line of showers-thunderstorms.  Expect wind gusts of 30-40+ mph to continue, and to also mix downward into some SW flow wave zones across the northern portions of Wise and Dickenson counties.

An outbreak of severe thunderstorms is looking likely by later this weekend over the Ohio Valley, with potential for one or more bowing squall lines.  The eastward progress of this will need to be watched as it approaches the western side of the Appalachians by Monday. 

ALERT For Areas Of Local To Widespread Dense Fog Into Saturday Morning

Overnight Into Saturday Morning

Cloudy.  A chance of rain showers, especially by morning.  Low clouds with dense fog at upper elevations, and local to widespread at other elevations.  Light winds.  Temperatures widespread in the 50s.

Saturday Morning Into The Afternoon

Cloudy.  A chance of rain showers, especially along and southeast of the Tennessee Valley Divide and High Knob high country.  Breaks in the overcast possible by mid-late afternoon, especially north of the high terrain.  SSE-SSW winds 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges & plateaus.  Temperatures varying from 50s in upper elevations to the middle-upper 60s ( warmest at lower elevations in the Russell Fork-Levisa Fork basins ).

Saturday Night Into Sunday Morning

Partly-mostly cloudy in the evening, becoming cloudy overnight into the morning with a chance of drizzle or showers.  SSE-SSW winds 5-15 mph, with higher gusts, on mountain ridges below 2700 feet.  S-SW winds 10-20 mph, with higher gusts, on mountain ridges above 2700 feet.  Mild for the season with temperatures mostly in the 50s.  Area of dense fog possible, especially at high elevations along the High Knob Massif-Tennessee Valley Divide.

Sunday Afternoon Updated

Partly-mostly cloudy.  Unseasonably warm & gusty.  S-SW winds 10-20 mph, with higher gusts.  Temperatures from the 50s to low 60s at upper elevations to the upper 60s to low 70s ( warmest at lower elevations in the Russell & Levisa Fork basins, as well as to the south into the Great Valley ).

Sunday Night Into Monday Morning

Partly-mostly cloudy & windy.  A chance of showers and thunderstorms, especially overnight into Monday.  Winds S-SSW 10-20 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet.  Winds SW at 15-25 mph, with higher gusts, on mountain ridges above 2700 feet.

Transition into a colder weather pattern is expected next week, with temperatures trending back toward near to below average.


Weather Discussion ( Moist-Mild )

Sunday Evening Updated Discussion

Strong SW winds are roaring over mountain ridges-exposed plateaus in the Cumberland Mountains this evening and will continue into the overnight as a line of showers and thunderstorms approaches the Appalachians.

Black Mountain Mesonet

Caution is advised to be extra careful of breaking limbs or trees, especially in the mid-upper elevations, but also at some lower sites in climatologically favored zones where mountain waves on SW winds break downward, such as within the Pound-Clintwood corridor and locations lying downstream of the High Knob Massif – Black Mountains.


Previous Discussion

A moist & unseasonably mild November air mass will grip the mountain landscape throughout this weekend, with a notable increase in gusty S-SW winds expected by Sunday into early Monday in advance of a cold front.

Storm Prediction Center Risk Regions – Sunday Into Monday Morning

A rather large region from the Ohio Valley and lower Great Lakes into the middle Mississippi Valley will come under the gun for potential severe thunderstorms by Sunday.  While the strongest activity is currently expected to remain west of the mountains, any east-southeast moving squall lines will need to be monitored as they cross into Kentucky.

European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 1-5

Storminess will be occurring in advance of a major transition in the upper air pattern during next week; however, still not the complete change upstairs ( as highlighted below ).

This change being forced to occur as the atmosphere fights to establish some type of balance, between a simply HUGE autumn temperature gradient across North America ( noted above in the region between the eastern front range of the northern Rockies and the southern Plains & Mexico ).
European 51-Member Ensemble Mean 850 MB Temp Anomalies: Days 6-10

  A shift from unseasonably mild to below average temperatures is currently forecast by the MEAN of European Ensembles.

European Model 500 MB Height Anomalies at 8 AM Friday – November 3, 2017

However, before winter fans get carried away, it should be pointed out that anomalously strong 500 MB heights over the Aleutians and Bering Sea is present currently and is forecast to remain in place through the next 10 days.

*Observe how strikingly similar the current pattern ( above ) is to that observed ( in the mean ) during Winter 2016-17 ( below ).
Observed 500 MB Height Anomalies – Dec to Feb of Winter 2016-17

If you do not understand why this is important, simply look back at the MEAN pattern observed during last winter and note that there is a strong correlation between positive 500 MB height anomalies with a Bulls-eye type of configuration over the Aleutians & Bering Sea and milder than average weather conditions in the eastern-southeastern USA.

500 MB Height Anomaly Pattern During February 2015

If the positive 500 MB height anomaly pattern should lose its “bulls-eye” type of configuration, becoming elongated as observed above, during February 2015, then a completely different result would occur ( much different! ).

A negative trend in the Arctic & North Atlantic Oscillations is forecast to occur during the next 1-2 weeks; however, due to persistence of a “bulls-eye” type of 500 MB height anomaly centered over the Aleutians-Bering Sea a -PNA pattern will continue to fight against eastern USA troughing.
It remains early, with the high latitude winter pattern just now taking shape, such that current blocking does not mean that the outcome will be the same as last winter ( every winter season is different, so stay tuned for updates as mixed signals are being teleconnected from the Arctic region at present…some which favor a “bad” winter and some favoring another mild season ).