061216 Forecast

Mountain Area Forecast ( June 10-12 )

Humidity, heat, and haze will be increasing into this weekend along with chances for at least hit-miss showers & thunderstorms  ( especially by late Saturday into Sunday ).  Slow down and take it easy as heat-humidity increases.
Thunderstorms could become strong to locally severe if clusters develop amid WNW-NW flow ( with potential for activity passing north of the Cumberlands initially to generate outflow boundaries that function as new trigger zones…stay tuned for later updates ).

Overnight Into Friday Morning

Partly cloudy ( high clouds ).  Light and variable winds.  Temperatures varying from low-mid 40s in cooler valleys to the 50s across mid-upper elevation ridges-plateaus.

Friday Afternoon

Partly to mostly sunny ( high clouds ).  Light WNW-N winds. Warmer with MAX temperatures varying from low-mid 70s in upper elevations to the low-mid 80s.  Some increase in humidity and haze.

Friday Night Into Saturday Morning

Partly cloudy ( some high clouds ).  Light S-WSW winds less than 10 mph along middle elevation ridges below 2700 feet. Winds SW to WNW at 5-10 mph, with some higher gusts, on mountain ridges above 2700 feet.  MIN temperatures from low-mid 50s in cooler mountain valleys to the low-mid 60s.

Saturday Afternoon

Partly cloudy.  Significant increases in humidity & haze.  Hotter.  Chance of a shower or thunderstorm.  Winds W at 5-10 mph.  MAX temperatures varying from mid-upper 70s in upper elevations to the mid to upper 80s ( hotter to the south toward the Tri-Cities ).

Saturday Night Into Sunday Morning

 Hazy, warm & humid.  Chance of a shower or thunderstorm ( especially in northern locations ).  WSW-WNW winds 5-15 mph, with higher gusts, along middle elevation mountain ridges and plateaus below 2700 feet.  Wind WNW-NW 10-20 mph, with higher gusts, along mountain ridges above 2700 feet.  Temperatures varying from 60-65 degrees in cooler valleys to around 70 degrees on exposed mountain ridges.

Sunday Afternoon

Partly to mostly cloudy.  Chance of showers & downpours in thunderstorms.  Some storms could be locally strong-severe with damaging winds.  Winds WNW-NW at 5-15 mph, with higher gusts.  Temperatures varying from lower 70s to the lower to middle 80s ( coolest at highest elevations ).

An increasingly stormy pattern into next week will need to be monitored for the potential of heavy to locally excessive rainfall amounts, as well as strong-severe thunderstorms.  Stay tuned for later updates in coming days at the pattern becomes more clear.


Weather Discussion ( June 9-12 )

A spectacular June air mass graced the mountain landscape during Wednesday into Thursday, with unseasonably cool temperatures that featured MINS in the 30s to lower 40s within mountain valleys by early hours of June 9.

Spectacular June Air Mass In Cumberland Mountains
Spectacular Air Mass In Cumberland Mountains – June 9, 2016

Seasonally cool conditions continued to be featured through Thursday ( June 9 ) with PM MAXS varying from 60s at highest elevations in the High Knob Massif to the upper 70s to around 80 degrees at lower elevations.

European Ensembles MEAN 500 MB Height Anomalies
European Ensembles MEAN 500 MB Height Anomalies – DAYS 1-5
A persistent WNW to NW flow pattern will be featured during coming days, with a huge heat ridge centered across central portions of the USA in the MEAN.
While a upper low could form and cut-off beneath the heat ridge, there will be a significant trough over or near New England to generate a baroclinic zone regardless of upper low formation.
European Ensembles MEAN 500 MB Height Anomalies
European Ensembles MEAN 500 MB Height Anomalies – DAYS 6-10

This type of pattern will tend to keep the hottest air suppressed to the south and west of the Cumberlands as debris clouds ( blow off from upstream thunderstorms ) in this WNW-NW flow works together with terrain induced cloud formations to hold temperatures back a little more than would otherwise occur ( as is predicted by feedback from a wet May 1 to June 6 period ).

*It will still be hot, but not as intense or as prolonged in nature given May 1 to June 6 wetness.  This wet period will now become an important factor as evapotranspiration from trees and vegetation feeds into the overlying air in coming days to help increase clouds and chances for showers and thunderstorms ( by next week this could aid formation of an increasingly stormy, wet pattern ). 

Although details remain to be worked out, it appears that a persistent northeastern USA upper trough will enhance a temp gradient that aids thunderstorm development across the Great Lakes and Upper Midwest in coming days, with debris cloudiness ( initially ) advecting southeast across the Appalachians to partially filter insolation.  A local shower or thunderstorm could develop off the terrain Saturday.

Thunderstorm chances will increase along a front that forms in the temperature gradient by Saturday Night into Sunday, as haze, humidity levels increase significantly.

Next week a upper level low may form beneath the heat ridge ( or a WNW-NW flow will persist ) to enhance the risk for showers and downpours in thunderstorms.  Depending upon how this may play out, a heavy to excessive rainfall potential could arise and will need to be closely followed along with the chance for strong-severe storms.

GFS Model Total Rainfall Forecast Next 16 DAYS
GFS Model Total Rainfall Forecast Next 16 DAYS – 2 PM June 9 Run
Forecast models will jump around with heaviest rain amounts, but the signal for heavy to excessive rainfall totals is there on the GFS and European ( most importantly ) models and many ensembles.
GFS Model Total Rainfall Forecast Next 16 DAYS
GFS Model Total Rainfall Forecast Next 16 DAYS – 8 PM June 9 Run

Meanwhile, slow down and take it easy as the first surge of true summer heat & humidity develops into this weekend.