112616 Forecast

Mountain Area Forecast ( Nov 25-27 )


ALERT For Dense Fog & Freezing Fog Across Upper Elevations Above 3000 Feet Into Saturday Morning.  Locally Lower Bases In Places Along & N to NW From The High Knob Massif and Tennessee Valley Divide.

As of 10:00 PM Friday air temperatures had dropped to freezing ( 32 F ) on the highest peaks, with low cloud bases producing dense fog at elevations above 3000 feet.  The freezing fog level will drop toward 3000 feet overnight, with very low visibilities at times.  Some freezing drizzle and/or drizzle will be possible into Saturday morning.

A Drop In Cloud Bases Is Being Monitored For Later Friday Into Saturday Morning On Upsloping NNW-NW Winds, with Freezing Fog Possible At Higher Elevations Above 3000-3300 Feet Along & North Of The High Knob Massif-Tennessee Valley Divide.

Overnight Into Black Friday Morning

Partly to mostly cloudy.  Areas of fog.  S-SW winds 5-15 mph with higher gusts ( especially along upper elevation ridges ).  Temperatures varying from 30s in mountain valleys to the 40s across exposed mid-upper elevation ridges.  Wind chills in the 30s along high ridges.

Friday Afternoon

Mostly cloudy.  Turning cooler.  Chance of sprinkles or light rain showers & drizzle.  N-NW winds 5-15 mph, with higher gusts on ridges.  Temperatures varying from the mid 40s to the mid 50s ( coolest at high elevations ).  Wind chills in the 30s and 40s ( coldest at highest elevations ).

Friday Night Into Saturday Morning

Cloudy.  Turning colder.  Low clouds with dense fog across higher ridges becoming freezing fog.  Winds NNW to NW at 5-15 mph.  Temperatures varying from low 20s to lower 30s  ( around 20 on highest peaks ).  Wind chills in the 10s & 20s.

Saturday Afternoon

Low clouds giving way to partly-mostly cloudy skies.  Winds NW-N at 5-10 mph.  Temperatures varying from 30s to low 40s ( around 30 degrees at highest elevations ).  Winds chills in the 20s & 30s ( around 20 degrees on highest peaks ).

Saturday Night Into Sunday Morning

Mostly clear.  Cold.  Winds becoming light & variable, except along upper elevation mountain ridges where NW winds of 5-10 mph will occur.  Temperatures varying from the 10s to mid 20s ( 10-15 in colder valleys versus steady or slowing rising temperatures along highest ridges into the 30s overnight into morning ).


Weather Discussion ( Wet Pattern )

Friday Night Update

A developing inversion below 850 MB is combining with cold air advection on upsloping NNW-NW winds to develop dense fog at high elevations along the Cumberlands.

Black Mountain MesoNET
Black Mountain MesoNET – Observations Ending At 10:40 PM Friday
Friday evening visibility has been very low on Eagle Knob of the High Knob Massif, with cloud bases having dropped downward to around 3100 feet in elevation as of 9:45 PM.

Freezing fog developing at highest elevations will drop into the overnight toward 3000 feet and could locally get a little lower along & north to northwest of the High Knob Massif.  Some freezing drizzle ( or just drizzle at lower elevations ) will also be possible into Saturday morning.

Cloud bases will lift into Saturday afternoon, but much of the day could remain cloudy along the upslope side of the mountains ( keeping conditions raw and cold ).


Previous Discussion

Smoky conditions again became a significant issue across the region on Wednesday, with lingering Thanksgiving day smoke beneath partly-mostly cloudy skies.

Smoky Morning Sunrise Above Long Ridge
Smoky Morning Sunrise Above Long Ridge of Tennessee Valley Divide
Wayne Riner Photograph Thoughts:
Wildfires filled the morning sky with smoke, turning the sun red and blurry.
Black Mountain MesoNET
Black Mountain MesoNET
Thanksgiving day MAXS reached around 50 degrees at highest elevations ( versus 60-65 at lower elevations ) with dense fog and low cloud bases obscuring high crest lines during much of the day.  Rainfall only totaled around 0.05″ at Big Cherry Lake Dam.

A wind shift Friday, with development of N-NW flow, will again push away the smoke and turn air chilly in the Cumberland Mountains.

NAM Model Forecast Sounding
NAM Model Forecast Sounding At 7 AM Saturday – November 26, 2016
Clouds and the potential for some freezing fog at high elevations is being watched for late Friday into Saturday morning and will be dependent upon the transport of low-level moisture into the area.  A low-level inversion could alter this, so stay tuned for updates.

There appears to be more uncertainty in the short-term, with fine details, than in the big picture of the longer term which looks to turn wet across the Mountain Empire.

Reference My 112316 Forecast Discussion For Previous Details.
European Ensemble MEAN 500 MB Height Anomalies
European Ensemble MEAN 500 MB Height Anomalies – DAYS 4 to 8

There have been no changes in my previous thinking, with model ensemble groups actually becoming stronger and in better agreement with a flow pattern conducive to a shift into wetness across the Mountain Empire next week.

The European Ensemble MEAN basin average rainfall is around 1.50″ during the next 7 days, with 2.50″ to 3.00″+ during the next 14 days ( which means the potential for locally heavier amounts ).

A deepening southwesterly flow, with a tap into Gulf of Mexico moisture ( a lacking ingredient in recent months ), will be a key factor in this shift to wetness.

GFS 21-Member Ensemble Precipitation Forecast
GFS 21-Member Ensemble Precipitation Forecast – Next 12 DAYS

Rainfall can not be truly counted, of course, until it becomes measured in the rain gauge…but certainly the upcoming pattern offers much hope and represents a radical shift from Autumn 2016.