ALERT FOR BITTER COLD CONDITIONS DEVELOPING WEDNESDAY NIGHT INTO THURSDAY WITH SINGLE DIGIT AND SUB-ZERO WIND CHILLS
Low Cloud Bases And Dense Fog Will Increase Across Mid To Upper Elevations Overnight Into Wednesday Morning, With Freezing Levels Dropping Into The Norton-Wise Area By Morning. Caution Is Advised.
Overnight Into Mid-Morning Tuesday
Partly-mostly cloudy ( mainly high clouds following break up of low clouds-dense evening fog across high mtn ridges ). Areas of fog possible in some lower elevation locations. W-NW winds 5 to 15 mph shifting to SSE-SSW into morning. Temperatures varying from 20s in colder valleys at upper elevations to the low-mid 30s, except rising temperatures overnight into morning along high mountain ridges.
Mid-Morning Through Tuesday Afternoon
Cloudy with light rain and showers developing. Light SSE-SSW winds shifting SW by late. Chilly with temperatures mostly in the 30s to low-mid 40s ( steady or falling into the 30s in upper elevations above 3000 feet ).
Tuesday Night Into Wednesday Morning
Cloudy with a chance for drizzle or high elevation light snow. Cloud bases lowering with dense fog formation from around the elevation of Wise upward toward midnight into the morning. Freezing fog developing by morning at locales above 2500 to 3000 feet. NNW-NNE winds 5-10 mph, with higher gusts, along mid-upper elevation ridges-plateaus. Temperatures varying from low-mid 20s to low-mid 30s, coldest in upper elevations. Wind chills in the 10s and 20s.
Wednesday Afternoon
Mostly cloudy. Low clouds possibly lingering across high elevation crestlines ( or lifting briefly ). Seasonably cold. N-NW winds mostly less than 10 mph. Temps varying from upper 20s to lower 30s in upper elevations to the mid 30s to around 40 degrees.
Wednesday Night Into Thursday Morning
Partly to mostly cloudy. Becoming windy and bitterly cold. Chance of flurries and snow showers. Light accumulations of very dry, fluffy snow possible along upslope side of the mountains. WNW-NW winds 10-20 mph, with higher gusts. Temperatures varying from to 0 to 5 degrees at highest elevations to the lower-middle 10s ( a little “milder” lee of the mountains into valleys of the Clinch, Powell, Holston ). Wind chill factors in the single digits above and below zero, except -10 to -20 degrees below zero along upper elevation mountain ridges ( especially in the many gusts expected ).
Weather Discussion ( More Bitter Air )
Tuesday Night Update
I have updated the forecast to include more clouds through Wednesday into Wednesday night. At the present time low cloud bases are engulfing locales above 3000 feet elevation, with very dense fog that is freezing at highest elevations.
As colder air arrives overnight, on northerly upslope flow, the threat for dense fog engulfing Wise and adjacent locales will increase with bases being in or just above the town.
High Knob Massif Webcam – University Of Virginia’s College At Wise
Interesting clouds were observed above the High Knob Massif and Norton-Wise area during Tuesday ( above ) amid chilly showers.
As bitter air arrives Wednesday Night into Thursday there could be some snow showers; however, with no connection to Great Lake moisture sources any accumulations will be light ( as has been the recent trend ).
*Frozen precipitation types ( mainly sleet and/or freezing rain ) are being monitored at the onset of another storm system set to impact the region by late Friday Night-early Saturday before a change to all rain. A change back to frozen types and/or snow will then be possible as cold air tries to catch deep moisture Sunday. Significant rain will be possible in the middle. Stay tuned for updates on this messy looking storm system.
Previous Discussion
While more bitter air is on the way, the first topic is about another soaking rainfall with heavy 1.00″ to 2.00″ amounts in upslope locales of the High Knob Massif-Black Mountain corridor during Monday.
Big Stony Creek Stream Levels – November 26 to December 12
Whitewater creeks are again gushing with Big Stony Creek near the red alert level at 4 vertical feet of water depth. A automated rain gauge at top of its 42 square mile watershed reported 1.40″ of rainfall; however, with 20-30 mph sustained winds and gusts of 40 to 50+ mph, there was at least a 20-30% undercatch on the gauge located at 4196 feet above sea level.
Caleb Ramsey measured 1.10″ of rainfall at the City of Norton Water Plant up to 9:00 AM Monday, with more rainfall after this time ( 3.76″ December / 52.33″ 2016 ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
The latest rainfall came between a couple of gorgeous sunsets, with mountain waves being illumnated late Sunday ( above ) as winds ROARED across the High Knob Massif in advance of the rains. More waves were seen lingering after the rain event late Monday ( below ).
High Knob Massif Webcam – University Of Virginia’s College At Wise
A much weaker system will develop more cold rain showers across the area Tuesday, with a wind shift to northerly into Tuesday Night-Wednesday Morning likely to lower cloud bases on upslope to engulf Wise and adjacent communities in dense fog ( by the Midnight-Sunrise period ). Situations like this typically generate very dense fog that can be dangerous to those not expecting the low visibilities.
*If happening in the Tri-Cities this would generate a Dense Fog Advisory, but here it is nearly always overlooked and has simply become neglected despite covering hundreds of square miles in the upslope advection zone ( orographically generated clouds ).
European 51-Member Ensemble MEAN 850 MB Temp Anomalies: 7 AM Thursday
The main short-term feature will be another bitter hit of arctic cold air, with the MEAN of the 51-Member European Ensemble group forecasting temperature anomalies on the order of 20-30+ degrees Fahrenheit below average by early Thursday. This will mean air temperatures near 0 degrees at the top of the high country, with 10s in “milder” locales at lower-middle elevations in the mountains.
Wind chill factors of 0 to -20 below zero are expected across upper elevations, especially amid the many gusts that will occur, with single digits to around 10 degrees at lower & middle elevations in the Cumberland Mountains. CAUTION IS CERTAINLY ADVISED.
European 51-Member Ensemble MEAN 850 MB Temp Anomalies: 7 AM Saturday
A dramatic temperature increase is expected as the next significant rain maker develops by this weekend, with a strong 850 MB low-level jet stream developing once again to crank up orographics for yet more heavy rainfall.
Forecast vector wind flow is nearly ideal versus climatology for another heavy rainfall event within the High Knob Massif – Black Mountain corridor, with potential for more rain than just received. This will need to be closely followed as it could push creeks hard enough to cause water problems.
While there could be some frozen on the edges, I can not stress enough yet again that the pattern is simply not what one would want for significant snowfall in the southern Appalachians. In fact, it may be warming in the MEAN during the week before Christmas to continue what is currently the only drought going…a Snow Drought.
*Things can, of course, change quickly and this does not mean there will not be a White Christmas this year. It also does not mean that there will not be significant snowfall this winter. During the October-December 2015 period only a trace to 0.5″ accumulated in the mountain area. Some 78″ followed during January-February atop the High Knob Massif, with 40-50″ in the Norton-Wise area. So do not give up yet snow lovers!
