The question I get all the time-- When is it going to snow?

 Christmas Snow was nice for people west of the Blue Ridge, but accumulating snows never made it into Lynchburg. I wasn't shocked, but it was definitely a snow win for the Roanoke Valley. 

This pattern is weird in that November was so warm AND the Jet coming off the Pacific is so strong, we can't build any cold air in North America. We have good blocking  in the NAO and AO regions, but when those areas are toasty warm,  it doesn't matter. This active storm pattern with cold air would have a few snow to ice to rain events, but the lack of cold air gave us a marginal ice event and that's it for winter events. . 

Moving forward, a few things will happen:

1. Seasonal temps just get lower. I mean, It's January. Easier to snow with our lowest temps of the year because it doesn't have to be a huge anomalous cold. 

2. The blocking over Greenland (Good if you like snow) will drift even further west towards  Baffin Island, Canada. This aides in our cold air regions. It doesn't allow for Pacific air to invade Canada. They cool down, even if about normal and it is forced south. 

3. We have a Sudden Stratospheric Warming starting early January. The simple version is winds reverse way up in the stratophere that helps weaken the Polar Vortex. This sounds counter intuitive, but a strong polar vortex is bad for us and weak is better because it pushes cold air away from the artic regions and down to the mid latitudes where we reside. 

These both pre and post conditions to the Warming are likely connected by various factors and it should help shape a good pattern from January 15th into parts of February if you are a fan of cold and snow. We have no specific threats at this time, but my hunch says by mid January threats for snow and ice may be on tap. The last time we had something like this happen was 2018 and the pattern held up about 6 weeks with 3-4 winter events. (The last was snow on April 9th in Lynchburg and the Timberlake Tornado happened 5 days later)

Summary: Colder air should be in place by mid month with some specific storm threats likely at that time. Pattern may last 4-6 weeks of colder/ threats for winter precipitation. 

Red to Brown is higher heights over Greenland into NE Canada (Baffin Island) and Green and Blue over Aleutian Islands (Lower Heights, vortex) is a good look for cold and snow. 

Wednesday December 16th is worth watching for snow/ice threat.

After literally no real threats last winter, December 16th maybe worth watching for a winter event. 

Sunday night into Monday brings in MORE rain, adding to our record setting year of precipitation in Lynchburg. At this point the plot thickens..

What we know-

1. Cold air is building in from the North and west Tuesday into Wednesday.

2. Storm associated with a short wave develops in the mid south. 

What we don't know-

1. How much cold air will be in place. This matters greatly for obvious reasons. 

2. Storm track- Some data shows this as a "Miller B" where a low forms and moves to our west while a secondary low forms off the Atlantic cost somewhere.  With our proximity to the mountains, often this means we warm at the mid levels but not at the surface.  Snow usually changes to ice in these set ups, faster the further south and east you are located from Lynchburg. 

When will we know?

Wednesday is 5 days away so generally we know there should be a storm that day and enough cold air should be in place for for some winter precipitation.  General ideas of what to expect should be in place by Sunday. 

Highest risk for snowfall will be places along I-18 from the Mt Empire, through the NRV, Roanoke and heading towards Harrisonburg. A change or mix to ice and even rain very much in play here too. 

Next risk Level would be Smith Mountain lake towards Lynchburg with Snow and ice combination likely that could end as rain. 

Lastly, Southside including Martinsville, Danville and South Boston would have the lowest risk but snow/ice and rain are likely. Still may end up with a significant winter event. 

General rules I follow about these type events. 

1. We tend to warm at the mid levels faster than modeled- meaning if a mix or change may happen, I usually speed it up on my forecast.

2. Surface temps like to be colder than modeled in this set up. Cold air damming (Surface high to our north that forces cold air down the east side of the mountains) tends to be stronger than modeled. A change to ice doesn't mean warmer at the surface. I usually lean a few degrees colder at the surface. 

Will send updates as needed as more data becomes available. It seems like there could be a decent amount of moisture associated with this event-  from .75 to maybe 1.25 inches of liquid equivalent, meaning whatever falls (Snow, Sleet, Freezing rain and or rain) will be impactful to your work week starting late Tuesday and into Wednesday and Thursday. 

Winter outlook 20-21

 Well, winter literally could not have gone any worse in Lynchburg with the first goose egg ever. (Some data may show otherwise, but I have searched climate data for years here, we had never had a zero. At my house in Forest we had more than a trace ( about 3/10 of an inch) but still. Horrible. 

Winter 20-21 will feature a low to moderate La Nina. Isolating those years, One year was our best winter ever (1995-1996) and recent winters of 2010-2011, 2016-17 and 2017-2018. 

2010-2011 had a snowy December, a near miss in January then winter ended (Missed a small event in March)

2016-2017 had a decent event in Early January then a miss (not near miss) early March. 

2017-2018 was a good winter South and East of Lynchburg and Roanoke and decent for those along the 460 Corridor (Blacksburg had a huge late March snow too) There was a decent event in December, especially south and east of Lynchburg, a decent snow better south and east of Lynchburg in January. February was warm but had one minor event. March was cold and snowy. 

La Nina winters tend to be drier than normal and we have to rely on the polar branch to deliver snow.  The mean storm track isn't great- to our west and north but at times leads to the 2-5 inch snow to ice events, especially Along 460 with a risk for a bigger/decent event. 

Temps- 2-3 degrees above normal for the winter, Risk for coldest month is December and first half of January. Warmest Month - February. Could have an extended winter well into march. 

Precipitation 10-20% below normal for the winter. 

Snowfall by region-

Southside including Danville-  3 to 10 inches. 

NRV including Blackburg 12-20 inches. 

Roanoke region- 10- 15 inches.

Lynchburg region 8-14 inches. 

* One big storm can ruin these small totals*

Will run an update before December 1.