022716 Forecast

My Weekend Forecast ( Feb 27-28 )

ALERT For Strong SW Winds Tonight Into Monday Morning Is In Effect For The Cumberland Mountains

Reference my 022616 Forecast for details on current conditions.

Saturday Forecast

A period of partly to mostly clear evening skies Friday will give way to mostly cloudy conditions overnight into the sunrise to mid-morning period on Saturday ( a few more flurries can not be ruled out, especially in upslope sites ).

Expect light valley winds and W-WNW winds of 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges & exposed plateaus.  Temperatures will vary from teens to mid-upper 20s across most of the area.

Clouds begin breaking up for a longer time period during the morning, with partly to mostly sunny afternoon skies expected to give way to a cold and mostly clear night.

Expect Saturday afternoon temperatures to vary from 30 to 35 degrees over snow along high crest lines and north slope locations in the High Knob Massif to the lower-middle 40s, with a little milder conditions lee of the mountains toward river valleys of the Clinch, Powell, Holston and Tri-Cities.

Saturday night will feature an increasing vertical temp spread between mountain ridges and valleys, with SW to WSW winds of 10-20 mph, and higher gusts, along mid to upper elevation mountain ridges & exposed plateaus.

This will cause temperatures to tend to rise at the highest elevations from late Saturday Night into Sunday Morning.  In contrast, valleys with light-calm winds will drop such that temperature spreads will vary from 10s to low 20s in colder valleys to 30s along exposed mountain ridges.

An ALERT for strong & gusty winds may be needed for middle to upper elevations by late Sunday into Sunday Night as the pressure gradient tightens along the Cumberland Mountains in advance of the next weather system.

Sunday Forecast

The day begins with mostly clear skies and a relatively large temperature spread between valleys sheltered from gusty SW-WSW winds and exposed locations & mountain ridges.  Although deep valleys will have colder air temps, wind chills along high ridges will make it feel just as cold.

Mostly sunny skies are currently expected with a large temp spread between upper and lower elevations.  A bias toward a little cooler valley conditions will also exist for locations along and southwest of the High Knob Massif & Tennessee Valley Divide, where rising air will hold PM temperatures lower than with sinking on SW flow into lower elevations across the Russell Fork & Levisa Fork basins.

Specifically, afternoon temperatures will vary from the lower-middle 40s over snow cover at upper elevations & northern slopes in the High Knob Massif to the middle-upper 50s ( 60+ may occur in some downslope locales ).  Actual “feels-like” conditions will be more extreme with wind chills making the afternoon feel like 20s to mid 30s for those who might dare to visit the High Knob Lookout.

Late Sunday into early Monday will feature increasing winds & clouds with a chance for developing rain showers.  SW-WSW winds of 20-40+ mph will become possible across middle-upper elevation mountain ridges & plateaus.


Weather Discussion ( February 26+ )

Some late PM brightening of cold, cloudy conditions helped to illuminate widespread snow cover across the High Knob Massif, and set the stage for a beautiful and colorful sunset.

High Knob Massif Webcam
High Knob Massif Webcam – University Of Virginia’s College At Wise
High Knob Massif Webcam
High Knob Massif Webcam – University Of Virginia’s College At Wise

This was a day featuring prolific mountain waves on NW flow, with NASA visible imagery offering some nice views.

NASA Visible Satellite Image
NASA Visible Satellite Image at 8:00 AM on Friday – February 26, 2016
There is little doubt where the true mountains begin, with waves popping out from the Cumberland Mountain Overthrust Block and Pine Mountain southeastwards.
Some instability became superimposed on the NW flow into the afternoon, with “bumpy” clouds over much of Scott County along and lee of the High Knob Massif amid turbulent flow.
NASA Visible Image
NASA Visible Satellite Image at 12:00 PM on Friday – February 26, 2016

Looking ahead, a volatile pattern will open the first week of March with up-down temperature swings and more periods featuring strong winds, rain, and snow.

Big Stony Creek Stream Level
Big Stony Creek Stream Levels During December 1 to February 26

As I have already highlighted, the time with gushing whitewater draining from the High Knob Massif is a testimony to winter storminess already experienced.

This latest storm system pushing total precipitation into the 25.00″ to 30.00″ range for upper elevations in the High Knob Massif since December 1.
Reference Winter Majesty In High Knob Massif for totals measured before this latest major storm dropped an additional 2.50″ to 3.00″ of precipitation on the massif area ( 2.44″ being measured on the northern base of the massif at the City of Norton Water Plant ).
GFS Ensembles Arctic Oscillation Forecast
GFS Ensembles Arctic Oscillation Forecast To 7:00 AM March 13, 2016

As highlighted in my 022016 Extended Outlook, the big picture will feature a prolonged negative trend to the  Arctic Oscillation coupled with a positive Pacific North American oscillation.

GFS Ensembles Pacific North American
GFS Ensembles Pacific North American Oscillation Forecast

This will maintain a general western USA ridge and eastern USA trough pattern in the mean, with tendency for colder than average conditions ( in the mean ).  Radical up-down temperature swings will also remain likely in early days during March ( with perhaps a more stable cold pattern arising later…still too early to tell about the stability ).

European Ensembles 500 MB Height Anomalies
European Ensembles MEAN 500 MB Height Anomalies – DAYS 1-5

While the mean western USA ridge & eastern USA trough pattern is very clearly seen on the MEAN of the 51-Member European Ensembles, there is a potential for an Omega type of blocking setting toward DAYS 7-10 ( featuring ridging centered more on the Rockies-western Plains ).

European Ensembles
European Ensembles MEAN 500 MB Height Anomalies – DAYS 6-10

To be honest, the upcoming pattern will be complex and greatly complicated by waves in the Polar and Sub-tropical Jet Streams that will at times have the potential to phase.  Any phasing could alter the upper air configuration and skew it away from the MEAN shown.

European Model Sea Level Pressure Anomaly Forecast
European Model Sea Level Pressure Anomaly Forecast – 7 AM Wednesday ( March 2 )

Initial focus this coming week will be on a couple of potentially major storm systems.  The first one of note arises by Tuesday-Wednesday ( March 1-2 above ).

The next potential storm ( below ) will also be a concern with Gulf of Mexico moisture connection yet again.

European Model Mean Sea Level Pressure Anomaly Forecast
European Model Mean Sea Level Pressure Anomaly Forecast – 7 AM Friday ( March 4 )

Tracks and intensities on these remain to be determined, but clearly the stage is being set via the upper pattern and embedded waves in the Polar & Sub-tropical Jets for more storminess in coming days.  These will be the focus of future forecasts, so stay tuned for updates.

Have a great Weekend.