012516 Forecast

My Forecast For Today ( January 25 )

The ALERT For Strong Winds Has Begun For Upper Elevations ( 3:00 PM ) With Downward Mixing Into Middle Elevations Expected Tonight

Caution For Possible Icy Patches From Refreezing Of Water And The Continuation Of Hazardous Travel On Untreated Roadways

ALERT For Strong & Gusty SSW-SW Winds Developing Across Mid-Upper Elevation Mountain Ridge-Plateaus During Monday Night Into Tuesday Morning

*Light freezing rain may be possible in sheltered mountain valleys by the predawn-morning hours of Tuesday, as well as on cold road surfaces running along northern slopes.

Overnight Into Monday Morning

Cold with high clouds.  SSE-SSW winds at generally less than 10 mph below 2500 feet.  SW-WSW winds 10-20 mph, with higher gusts, along exposed upper elevation mountain ridges & plateaus.  Large vertical temp spread between snow covered mountain valleys with calm winds and exposed mid to upper elevation ridges.  Temps varying from single digits and 10s in colder valleys to mid 20s-lower 30s on exposed mountain ridges ( wind chills in the 10s to low 20s ).

This Afternoon

Sunshine & high altitude clouds.  S-SSW winds increasing to 10-20 mph on mountain ridges & plateaus below 2700 feet.  Winds SSW-SW 15-25 mph, with higher gusts, along ridges above 2700 feet.  Temperatures in the 30s to low-mid 40s.  Wind chills in the 20s & 30s ( coldest at high elevations ).

Tonight Into Tuesday Morning

Mostly clear skies giving way to clouds.  A chance of light rain or showers by morning.  Possibly freezing in sheltered valleys and on northern slope roads.  Windy across exposed mid-upper elevation mountain ridges & plateaus.  SSW-SW winds 15-30 mph, with higher gusts, on ridges-plateaus at elevations below 2700 feet.  SW winds 25 to 35 mph, with gusts to 40-50 mph, on upper elevation mountain ridges.  Temperatures varying from low-mid 20s in colder valleys to the 30s on exposed ridges & plateaus.  Wind chills in the 10s & 20s ( coldest at highest elevations ).

*Some blowing and drifting of snow will be possible at high elevations as wind speeds increase Monday Night, especially across northern slopes and shaded sides of crests where snow tends to be shaded from direct sunshine ( keeping recent low density top layer snow loose & able to blow more efficiently ).


Weather Discussion ( January 24-25 )

Afternoon Update

The ALERT for strong SW winds has now started with recent gusts to between 40 and 50 mph along the high crestlines of the High Knob Massif and Black Mountain.

Black Mountain MesoNET
Black Mountain MesoNET At 4:30 PM on January 25, 2016

 Although temperatures have risen into upper 30s to around 40 degrees, it feels like 20s along the high mountain ridges.

Nora 4 SSE - Elevation 2640 feet
Nora 4 SSE – ENE of Wise At An Elevation of 2650 feet

Following a MIN of 12 degrees at Clintwood 1 W the PM temp climbed to 44 degrees before dropping back to 38 degrees as of 5:00 PM.  Low-Mid 40s have also been reported in Norton-Wise and the adjacent ridge communities on increasingly gusty SW winds ( and warm air advection ).

European Model 850 MB Wind Field Analysis
European Model 850 MB Wind Field Analysis At 7 AM Monday – Jan 25
A low-level jet and wind speed max will be moving up along the western side of the Appalachians tonight, with greatest impact across mid-upper elevations of the Cumberland Mountains.


My Overnight Discussion

Upslope snow finally ending into early hours of Sunday and low clouds began to break for some locations.  A real temp plunge took readings down to around 0 degrees or locally below in some places.

MIN Temperatures Sunday Morning

Burkes Garden
-2 below zero

Clintwood 1 W
1 degree

South Fork of Pound
5 degrees

Jonesville Airport
7 degrees

Upslope clouds held tough along and just north of the High Knob Massif to keep temps a bit “milder” into Norton-Wise, with upper single digits to lower 10s reported ( heatwave ).

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

The day featured beautiful blue skies and only scattered high altitude ice crystal clouds.  A nice day for NASA to capture Landsat Images of widespread snow cover.

January 24 - NASA Landsat Visible Image
January 24 – NASA Landsat Visible Image
Observe that flat or rolling terrain tends to show snow better than mountainous, convex topography
January 20
January 24 – NASA Landsat Visible Image

Unless you are really into climatology, an aspect that is never talked about on a day like Sunday is that snow glare causes thermometers to read too high, that is unless they are shaded completely ( e.g., on northern exposures ).

January 24
January 24 – NASA Landsat Visible Image

Even National Weather Service MMTS Thermometers can read too high with intense snow glare reflecting sunlight upward into radiation shields from the ground.

Nora 4 SSE ( Northern Exposed Thermometer )
Nora 4 SSE ( Northern Exposed Thermometer ) – Elevation 2650

That is one reason I like to use Nora 4 SSE observations, at the official NWS station of Wayne & Genevie Riner, where the thermometers are on the north side of the house and protected from radiation and intense snow glare.

The MAX temperature of 30 degrees was more representative of what elevations such as Wise truly had, with the elevation of this station being only 34 feet lower than Lonesome Pine Airport where the reported MAX reached 37 degrees.
*Snow glare radiation caused many Weatherbug Stations to read absurdly high during Sunday ( roof + snow glare ).
Black Mountain MesoNET At 2:45 AM - January 25, 2016
Black Mountain MesoNET At 2:45 AM – January 25, 2016

As always it seems amid this complex terrain, interesting weather variations are on display once again tonight with colder valleys 10 to 15 degrees at 2:45 AM ( Jan 25 ) verses a temp trend that has been rising along high crestlines into the lower 30s on steady and gusty SW winds ( WCF 10s ).

GFS Model 850 MB Streamline & MSLP Forecast
GFS Model 850 MB Streamline & MSLP Forecast – 7 AM Tuesday ( Jan 26 )

Speaking of which, SW winds are going to really begin to CRANK along the Cumberland Mountains late Monday into Tuesday Morning as this next weather maker arrives.

NAM Model Sounding Forecast Above Wise
NAM Model Sounding Forecast Above Wise At 1 AM Tuesday – January 26, 2016
This low-level inversion will be stronger than the NAM predicts since valley temperatures in many places will drop off fast during Monday evening above snow, before rising overnight into Tuesday morning for places that have enough turbulent, vertical mixing to overcome stratification ( warmer air above cold air ) and recouple calm valleys back up with strong flow along top of the boundary layer field ( the recoupling point being dependent upon the local terrain features and varying with location ).

An inversion will further enhance this setting by aiding channelization of air flow between the High Knob Massif and Black Mountain, as SW winds stream up through the High Knob Landform corridor tonight into Tuesday.

A possible freezing concern will be any valleys that remain decoupled, with light to calm winds, since precipitation will be developing by the predawn-sunrise period of Tuesday.  In addition, as past climatology shows, northern slope roads will also be a concern since surfaces will be very cold.

NAM 4 KM Model Total Precipitation
NAM 4 KM Model Total Precipitation Forecast Next 60-Hours
While precipitation amounts with this next system are yet to be fully resolved, the high-resolution NAM fits climatology with an axis of heaviest amounts extending northeast across the Cumberland range on strong SW flow.
*In particular, the upslope-downslope couplet being shown between the High Knob Massif-Black Mountain corridor and Russell Fork-Levisa Fork basins fits climatology of strong SW flow regimes well.
NAM 4 KM Model Total Precipitation
NAM 4 KM Model Total Precipitation
Although relatively close, the SW Upslope Flow snow potential with this system seems currently to be reduced by above freezing air forecast for the 825-775 MB layer.  However, should that layer cool then the threat would increase.  A trend to monitor today.

 Make it a great Monday.