Serious ice or serious sleet? Big event on the way region wide.

 Winter Storm watches are out for everyone in our region for a little snow, some sleet then ice. 

The basic set up is we have a piece of the polar vortex moving across New England pushing cold air into our region at the same time the "south east ridge" ridge means warmth in weather terms. This battle between the warm and cold will make for very moisture laden system with precipitation amounts of 1 to maybe 1.5 inches. 

I'm somewhat optimistic at this point that it will be a serious winter storm in the NRV to ROA to LYH with some icing concerns but we may just see enough sleet to mitigate HUGE issues with our power grid. (May, not a lock yet) This could keep freezing rain total UNDER a catastrophic level. Southside is another issue where they will get mostly freezing rain. As bad as the Farmville to Charlotte to Halifax area saw, this could be worse and more wide spread with more precipitation and colder tempatures. 

1. It may be a smidge colder, especially early on. You may be shocked to know that ice builds up more at 29 degrees than 31 or 32. 

2. It may rain harder, which is actually a good thing with freezing rain because it can't freeze fast enough but the duration will likely offset this. 

Basic Details:

Snow sleet and freezing rain develop overnight Wednesday into Thursday. Midnight to 4 am)

Southside: Quick burst of sleet to freezing rain. This will have a huge impact on the power grid. An inch or more of freezing rain will fall and build up on trees, power lines etc. I expect serious issues in this region with long term power outages.  Ice build up will be greater than a half inch most areas. It may take days to restore power. 

North of an Amherst to Daleville line, precipitation may start as an inch or two of snow, then sleet. 

** Caveat** The GFS blast a quick burst of snow from the NRV to Charlottesville that is in the 4-8 inch range before ice. I don't think it's going to happen but wanted to throw it out there. This gives Lynchburg an inch or two at the same time before any sleet falls. 

NRV to Roanoke to Lynchburg- 

A quick burst of snow will flip to sleet. We should see a good bit of sleet before freezing rain because the "warm layer" sits pretty high, above 5000k feet and from that point to the ground is a solid 3--6 degrees below freezing. That's a classic sleet signal. We could see between 1-4 inches of  quick burst of snow then mainly sleet. This should eventually mix with then become freezing rain and we will get a quarter inch of freezing rain build up. Most places had that in this past event, so I think we can mostly survive without HUGE power issues. With that, this is a Fragile forecast because if we change to freezing rain sooner, the Ice build up and power outages will be greater. 

For this region, I mostly see 1-4 inches of sleet, then freezing rain of about .25 build up. This is close to a crucial breaking point but hopefully we stat at this level. 

Temperatures may creep above freezing later Thursday but the damage will be done. We have better antecedent cold air, so there is a shot we remain at 31-32 until Friday AM. 

I'll pop some images on the bottom of this post but here are two- the top is predicted sleet  and ice accumulation from the RGEM model.  Note the sleet is total in inches and that in general 1 inch of rain is 3 inches of sleet. (meaning that most those in that area see an inch of precipitation fall as sleet.  Also note that the freezing rain map counts all that has fallen but it all won't freeze because when it is HEAVY freezing rain much runs off before it freezes. With that, those totals over 1.5 inches will be catastrophic. (At this point, those in Southside and Northern NC)

Wintery 10 days coming up- can we do better than mostly ice?

 We have a fun, fascinating pattern setting up where a piece of the polar vortex will position itself over the upper Midwest. (Great for Cold)

We also have a Southeast ridge based on other issues in the pattern ( Leads to warmth for the southeast) We sit in the Northern part of the south, tucked in near the Blue Ridge and quite honestly, the next 10 days will be chaotic. 2-4 chances of winter precipitation(and rain) We could see 2-3 inches of liquid in that time frame and trying to separate what falls when and where will be a challenge. 

Event 1 2-11/12. Cold air sinks in from the North, rain changes to freezing rain then sleet and perhaps snow. In general the further north you go the more sleet and snow you see. This likely won't be a big snow maker but 15 miles may be the difference between 3inches  of a sleet snow mix and a half inch of freezing rain. 

* I think the kids are out of school regardless most places Friday and maybe even Thursday*

Event 2 possible as early as 2/13 or Saturday as another weaker wave drops some light freezing rain during the day Saturday. 

Event 3 has the potential to be the worst of the three. This would be on or about February 16th.  The cold air REALLY builds in at the surface and some data suggests an ice storm that starts while temps are below 20. This would be Monday into Tuesday time Frame.  This is just one plausible outcome, but isn't the forecasted outcome at this time.  Liquid amounts of over an inch with temps in the teens rising towards freezing has BIG TICKET written all over it. 

This is a map of the heights anomalies. In simple terms, heights are calculated by the average temperature below that level. Those area blue and purple along the Canadian border and much lower than normal heights, meaning COLDER than normal temperatures. (Actually a piece of the polar vortex is there) The red over the Southeast USA is higher heights, or what should be warmer than normal temperatures.  

This gradient between higher heights and lower heights is creating all these storms. Cold air likes to push south in this pattern but is being pushed back by the Southeast Ridge. If that ridge wasn't there, we'd be cold and dry and that meaning very cold.  If that colder anomaly was not there, we'd be rather warm. What makes our situation unique is the Blue Ridge Mountains where the cold air, which is heavy and dense gets trapped and can't be moved out. (Remember, cold heavy- warm, lighter)  Some of the data for our storm Tuesday has surface temps in the teens but 5000 feet above temps are in the 40's. For those who remember the ice storms of 1994, this pattern is not far off looking 6-7 days out. 

The first of three chances is on Sunday- Monday.

 The long story short is we should have 3 distinct chances at some wintry precipitation starting Sunday. We can get all 3, we could get 2-3, (Which by Meatloaf standards isn't bad) We could only strike on one event and we could miss all 3 (And with three strikes you're out)

Setting up Sunday is a storm cutting to our west Friday that cause some rain then drag a cold front through.  A second piece of energy will then trail up that cold front. Where this gets dicey is- some model data doesn't push the cold through enough and primary low goes into the Ohio Valley then a secondary low forms. This set up ALWAYS changes us over or event starts as ice or rain OR the boundary could push too far south and is oriented in a way that allows it to escape harmlessly out to sea.  

I'm leaning towards Ohio Valley transfer at this time- but have plenty of time to adjust. This favors more snow in western regions, mix/rain set up East of Blue Ridge and Mainly Rain southside. 

Event two will be about Feb 11 second change at a winter event. (It's also the 38 year anniversary of the Megalopolitan storm of 1983 that dumped 15-20 inches region wide in our area of Virginia. I was 9 years old and we had true blizzard conditions at my home in New Castle, Delaware. 

We should have better cold air in place for this event and if there is any threat, it would be suppressed (To our south) or sheared (Upper energy weakens) and the storm falls apart. 

Looking past Valentines day, the 14-16 range may hold the best potential of the year as the blocking maxes out and just starts to relax. Often, in those relaxation stages a big storm pops. This is 2 full weeks out but this image shows strong cold air in place via upper air energy (starting the 50/50 lat/lon) with pieces of the a weakened polar vortex across the upper mid west. Energy near Cali indicates either ONE big storm potential or several smaller events if only pieces of the that upper energy comes out. 

The red stretching from Maine to Minnesota is a fragment on the weakened polar vortex while that red over the northern Baja is upper energy from the sub tropical jet.  

 

Again, this is about potential, not actual events. Things will change and adjust as we get closer. If you love snow, get your favorite lucky mug and if you are a snow hater, well- we went 700 days without accumulating snow. We know what they say about paybacks! 

Not a bad week, do we have an encore on deck?

 Well, region wide we did well with most places seeing between 4-7 inches of snow and sleet last night and today. For those in the Lynchburg vicinity, we broke out of our two year long snow drought. 

Wednesday night and Thursday ended being an official 2.1 inch snow.  I was a little worried when it was raining in Roanoke and 41 degrees here, but the "sounding" of the LYH was literally cold enough for snow, except for the surface. Sure enough, a few sprits of drizzle then snow. 

Last night and today was a bit of a challenge but one thing I said is that the 2 short term models that didn't have a decent snow were too slow bringing in the precipitation. Sure enough, that's exactly what happened. Round 1 was a half inch to an inch, we had a lull and fired up quickly, region wide as snow. Everyone had a little ice on top and now we sit at my house at 31.5 degrees. 

The Lynchburg seasonal total is officially 7.3 as measured by WSET while my house with 2 smaller events sits at 7.8 inches. 

We seemed destined for a week warm up and by the time the snow melts off the warm up may be only a couple of days. A late week storm will cut up into the Great Lakes regions. VERY cold air will filter in behind the storm Friday and some data suggests another storm forms and approaches the area Sunday. IF we get the snow and the cold, we will go in the ice box for a few days with multiple days possible below freezing. Here is a temperature map 2 days after the storm, at 1pm with temps in the TEENS across the region. Even if it is 10 degrees too cold, we are in the upper 20's early afternoon. 

So, road conditions will slowly improve tomorrow, we get a break from winter weather then we wait for the fine details of late weekend.  Could end up being just a blog that I post later isn't an option or we are forced to keep tracking it. 

Yes, it can snow in Lynchburg, and more may be coming.

Apologies for you non Lynchburg readers but we went almost 2 years without accumulating snow. The official WSET total reported to the NWS will be 2 inches on the nose, ending the worst snow drought in recorded history. Had a little drizzle to start at my place and was worried but snow started at 40 degrees and we quickly tumbled to 33 then 32. Beautiful snow that stuck to everything.

Sunday looks promising with the usual caveats meaning things can change this far out. 

1. We don't have much wiggle room with for a north trend. Often this close (under 72 hours) the north trend isn't the snow line moves north but they realize on the models the heaviest snow will be north of displayed on the model. 

2. Simple set up to start. We have a cold, dry air mass in place and warm air starts to ride over it creating snow. With strong cold air replacement, this means an eventual change to ice then rain. 

3. There is a primary low that will travel into Kentucky, maybe even Ohio that is forced under the strong blocking to our north. Depending on where this develops, we could get a little bonus snow Monday but I am not banking on this. This low will be slow to move out and some places, like DC area north to Philly suburbs will have a decent coastal event. 

What we need is the block to hold this little piece of energy in a confluent jet that will keep the cold in place and push the storm south. 

             Southside- Martinsville, Danville to South Boston 1-3 inches of snow to sleet and freezing rain. Ends as rain. Temps remain in mid 30's through Monday. 

              460 Corridor from East of Blue Ridge, into Lynchburg region including north SML to Altavista to Appomattox. 3 to 6 inches of snow, ends as ice. Freezing drizzle possible until Monday. Additional light accumulations possible Monday. 

Snow starts after Midnight Saturday and most is done by noon Sunday. Reminder. If the cold air isn't as strong, we will change to ice and rain faster, changing these amounts. This is a first look. 

 

 

That red dot east of Cape Cod needs to remain in place to hold our cold air in place and force the system south enough

Wednesday Night- Thursday Snow storm.

 Well, we made it to Sunday and we still have a snow threat middle part of the week. With that, the threat changed in how it is set up. 

The first view on the models had well into cold and very dry air and a storm even cutting west of our region, snow would break out and likely maintain as snow as the low jumped towards the coast. 

As we've gotten closer, the storm seems to be about 12 hours faster, starting overnight Wednesday and the cold air is not quite as strong changing the storm to a dynamically driven event. (And that's if the event takes place) This means we have to rely on the a strong upper air low to interact with the surface low and cool the atmosphere by both pulling in the cold air that is slowing sinking towards our region AND the strong lift (rising air cools, sinking air warms) from the deepening low.  This is because we don't have cold air in place, but arriving and being created as the storm unfolds. 

We have 2 basic storm evolutions displayed:

1. Precipitation from the west comes in over head as the upper air and surface low interact. Storm gets close enough and we got heavy rain to heave snow. Data showed 4 to 8 inch snow totals in this event with a sharp south cut off. Remember, 4 days out thinks like to drift north so this could happen but we get next to nothing. 

Another evolution problem is that some models showed the precipitation moving in from the west and as the transition happens the precipitation collapses quickly towards the low. Hence, we get the higher end solution but it infers risks that little to no snow could fall in that region. (That zone was east of the Blue Ridge)

Variations of this are show on the GFS and to an extent the Canadian Model. 

European model risk of 3 inches in percentages. 

American Model risk of 3 inches. 

2. Very little precipitation over head initially but the upper air low initiates a round of snow more along the lines of 1-3 inches. These tend to be more challenging to forecast because upper air snow "form during the event"-- so some people get it and some don't. The models showed a NW to SE band of snow that coved much of our region. 

Variations of this have been shown on the Euro and UK met model. 

Snow Potential. 

30% chance your specific location gets no measurable snow. (Trace amounts fall here)

40% chance your location sees a coating to 2 inches. 

20% chance your location sees 2-4 inches

10% chance your location sees over 4 inches. 

Here are my current views for risks

Very broad brushed at this time, but this is by far our best shot region wide for some snow. Each region has reasons why they could miss. Southside could be too far south, NRV and I81 region could be too far west. Lynchburg could literally be to east, too west, to north and too south. (It feels that way after almost 2 years with no measurable snow) 

To Ridge or not to Ridge

 Despite the mini blizzard in parts of the region yesterday,  we have no specific threats on the horizon for winter weather. We've had some great blocking in the North and East of us (Good for snow) but inconsistent blocking to our West. This lack of blocking, combined with the very Warm December has killed any change of snow. If we had any level of pre existing cold, we'd of had a few events at this point. Instead, Lynchburg and Danville have no snow while Roanoke and Blacksburg are inching forward with small events. 

A key source of our cold air comes from the EPO region (Eastern Pacific Oscillation) and where that Ridge sits controls if Canada gets cold. Remember, Canada was very warm after December and the cold has been blocked on the other side of the  world. 

There could be some light rain or maybe even light snow Friday across the region but early next week there is a threat of something (January 25 to 27) Some models are running the low pressure across the Great Lakes (maybe some ice to Rain) Some are taking it right at us which is snow to ice to rain some places and a few, which in build that ridge across Alaska force it to our south and we see some snow. I have no faith in this ridge because it's been "forecasted" to build all month and simply has not, but eventually it should.  If the ridge isn't there, the cold air that comes in simply isn't that cold and the storm will move to our north. 

In a La Nina winter, quite often the best threats are in February and actually into March but early month I was somewhat optimistic we'd have an event or two by now. At this point, I am just hoping we can get an event or two this winter. La Nina winters are use less than average snow save a winters aside. 

Will we Cash Out or Crap Out?

 In the digital world of weather, the 0Z (Midnight run) of the Euro had 3 digital storms starting with Friday that brought us all snow each storm. The end total was 10 to 18 inches total from the three storms region wide. 

Will We Crash in or Crap out? The noon run of the same model lost all 3 storms, for those wondering. 

Specific to Friday's event. Those who forecast this right will have a blend of both luck, skill and climo knowledge. 

Summary- A low pressure and associate upper air low will approach the area. Some unusual factors make it a challenge to see how far north this storm will make it. Further, this may be a rare case where the upper air low impacts our area. Last big time I think this happened, Roanoke and Blackburg had 10 inches of snow in 3 hours during February of 2014 (after 10 had already fallen)

I am against showing the digital snow maps but I will show a few to show the challenge. Making it worse, the models often shift back and forth on what the outcome will be. 

Mid afternoon run of 12k NAM, Big snows southside, misses most of Roanoke to Lynchburg. 

Noon run of American Model that show now snow within 60 miles of Lynchburg. 

\

3k NAM run mid afternoon, big snows into LYH, still mostly a non event in Roanoke. 

We are 48 hours from the event where clarity is not event close and many outcomes are possible. With that, it's not called forecasting for nothing. 

My initial thoughts for this first event-

Snow breaks out towards Morning southside and over spreads the entire region. This first push first guess is 2-4 inches from about the NRV South East towards South Boston. Further SW VA may do better here ( 3 to 6) Along 460 From Roanoke to Lynchburg this round will bring 1-3 inches. 

From this point, the forecast is tricky. The upper air support should then create a second round of snow. This is more tricky because it should be convective (think thunderstorm like, hit and miss) You get in these bands, you could get another 3-5, if you just get brushed another inch or two. Some places may be done after the initial push of snow. Very challenging. 

So, my current "First Guess"

  NRV down to Southside- 2-4 inches then we wait on the bonus snow.  If you get in the good bonus snow another 3-5 is possible. everyone won't get this. 

Roanoke to Lynchburg 1-3 initial push. 3-5 bonus snow possible too. Same disclaimer for not everyone will get it.

Everyone won't get it because often these bands set up and just don't really move. Then then weaken in that spot and form elsewhere. 

This is not a final call and this will change before the event.  Some timing issues where some models really hold off accumulating snows until late afternoon and other have snow on the ground in Lynchburg by 7 am. 

Other events worth watching early next week and then NEXT weekend.  Expect updates via Twitter and FB. 

The answer may be Friday/ Saturday to the question I get asked the most.

There is an event I've been tracking a few days that looks to take place in the Friday to Saturday time frame. We have the "Blocking" pattern I discussed but not a ton of cold air. A few models have hinted at the block forcing a system to our south with just enough cold air for snow in parts of the region. In the past couple runs of the models, there seems to be growing concensus in the models that the storm will both travel to our south and have "just enough cold air" in place. 

 Points to ponder- 

1. Things change as we get close. This is an outlook 5 days away. 

 2. Timing is not locked in as some models show early Friday start and others early Saturday. 

 3. Models have looked colder, not super cold as we get close. We obviously need the cold. Some places east and south may not have enough cold air or depending on timing, places may start as snow and end as rain. 

 4. This event that may stay to our south with the upper air puts is in "cold conveyer belt snows" where the upper air feature provides "banded" snow. Heavy in those bands and sad for those outside. Makes for a wide range of totals. 

 5. Would not throw out any totals but potential is there for an "advisory type event" which is an event of basically under 4 inches and yes, there is potential for a "Warning" event which is more than 4 inches.

 I'll tweet or FB updates more often if warranted and then throw another blog out by sometime Tuesday. We should have a pretty good handle on if the storm will come to fruition in some shape by that time.

This maps shows our blocking (red- higher heights and blue lower heights. Should help keep this storm south.

This is our upper air low moving due east from TN into NC. That's a great track for our region. As always, models like to push the precipitation NW as the event gets close, but data is a bit suppressed for our region, which is a good thing 5 days away.