Sunday, December 29, 2013

Cold still coming-- Snow no chance.

Maybe some light snow, rain or flurries Tuesday AM, but no real shot of anything more.

Was totally wrong on the Thursday event-- won't do much of anything.

Cold air still incoming-- a few days 32 degree range.

Can't seem to break the cycle of Cold shot, cold air departs as storm approaches and then warm up for storm, back to colder temps. Need some blocking in the northern Atlantic to lock our cold air in.

Saturday, December 28, 2013

Cold is coming is a lock-- snow is POSSIBLE.

Merry Christmas and Happy New Year to all--

Dusting off the weather blog to do some updates.

December has been an active month with a few "winter type storms"..

Temps have been what I expected, slightly above normal. We are running a +3 on the month, but 2 days have bumped that up where the lows were in the MID 50's-60 ish rather than mid 30s or so. We'd be in my 1-2 range I thought if not. We should end up between 2-3+ for the month.

It has been much more stormy than I had anticipated. We should be 3-4 inches above normal precipitation wise by months end with the rain coming tomorrow.

More cold air is heading our way.

1. One model shows a round of snow Monday night into Tuesday AM-- this is ONLY the NAM and it usually stinks in this range. It be coating to a couple inches. There is some energy on the backside of a cold front that causes this. Not buying this-- but it's on the "watch" list.

2. Some VERY cold air comes in New Years Day-- highs in the 20's a couple days.

3. A stronger piece of energy comes in Jan 2-3. Models have been all over the place, but something called the ensembles have slowly agreed on a more southerly track that keeps the cold air in place (It's been an issue with no blocking to the north to hold our cold air in place.

The air is VERY cold and as modeled now, it's not a super wet storm with modeled precipitation being near .5 to .6 of an inch. However, with it being very cold aloft, snow rations could be more like 15-1 so .5 could be 7-8 inches.

Key issues will be how strong the upper air energy is and can we keep the cold air in place, but not TOO strong to suppress the storm to our south.

This is MUCH higher on my list than the Monday night event. :) Will update as needed...

Monday, December 9, 2013

Quick update: Ice wrap up, and maybe a little snow and sleet to end RAIN tomorrow.

We dodged  bullet-- had that morning sleet and ice been more intense, I think power outages would have been more common. Instead, things looked cool, pretty- whatever adjective you choose and life is pretty normal.

I'm sure most of you saw footage from the Eagles-Lions game. Pretty incredible that they were expecting up to an inch via forecast, and they got slaughtered with 8 inches in the 95 corridor from Wilminton, DE to the Linc on Broadstreet. This is still an inexact science and mistakes will be made.

Another wave passes through tomorrow. Should start as rain towards morning, could mix with a little sleet and end as a burst of snow. I think the snow idea is a bit far fetched, and you may see a few maps on FB bringing 1-2 or 2-4 inches down to our region. Overdone-- 64 north will be the region that gets the 2-4, maybe 3-6.  Will keep you posted, but our best case scenario is 1-2 hours of wet, big flakes falling that MAYBE coat the ground.

Saturday, December 7, 2013

Late evening Update-- Potential to get much more serious.

We had 2 options to prevent a big ice event. (Colder air was a lock)

1. Colder profile-- more sleet and snow.
2. Less stuff falling.

1. Profile has done a typical CAD where under 5k up has cooled a little and lasted longer while above will warm fast. At some point, the surface will be 29 or so and 5000k will be 50. WOW...

2. Models have trended wetter-- mostly. Minimum is .50 falling, max is up over an inch.

Most ominous is the RGEM-- Note this is in MM, and puts the 460 corridor in  25 mm, which is about an inch, give or take. Orange is right on top of 460.

Will update on FB on twitter from here. PM w any specific questions. 

Yo'-- Let's kick it. Ice Ice Baby

No big changes--

Snow and sleet develop north of 460 between 5 and 8 am tomorrow. 
Sleet, with maybe a few snow flakes, quickly changing to freezing rain develops southside Between 4am and 7AM.

460 north could see up to 2 inches of snow and sleet, mainly sleet. I suspect it's mostly freezing rain by mid afternoon, with a little sleet mixed in. For those wondering, sleet accumulates about a 3-1 ratio, so one inch of rain water  3 inches of sleet. I suspect that between .2 and .4 max falls as sleet. That's a half inch to about an inch and a quarter based on my best guess. 

Freezing Rain- southside will see a glaze to .25 at the most. 
460 corridor gets .15 to .40
Once you get NW Amherst County, Rockbridge, Fincastle north, .25 to maybe .60 could occur. The best moister wants to focus on that area JUST north of 460. Something to watch on radar tomorrow. 

Friday, December 6, 2013

Winter Storm Watches Hoisted-- Complicated forecast.

As is often the case, with our storm as some details clear up others become more murky.

It really seems like a mix of snow and sleet develops and begins a drift towards freezing rain, starting in areas to the SW and spreading north and northeast.

Drier air is a concern and where exactly the best lift sets up is a concern as well, because some areas that are expecting a decent snow and ice event COULD end up rather dry, with just freezing drizzle the bulk of the day. Anywhere from 460 south needs to be aware of this concern.

This will likely be a "winter storm warning" but will lack the total moisture to be a "big ticket event". The colder temps will make it a travel concern but major power outages, ect are not likely, especially from 460 south. North of there, snow and sleet should minimize ice build up.
Add caption
Yellow: Initial burst of sleet, maybe a little snow switching to Freezing Rain. up to a coating of sleet and snow, up to .15 ice build up.
Green:  Sleet and snow mix to start, Coating to 2 inches. Ice build up from .1 to .25 in hardest hit areas.
Pink;  Coating to 3 inches of snow/sleet. .15 to .40 ice build up. 

Yellow area includes: Martinsville, Danville and South Boston. 
Green area includes: Blacksburg, Lyncburg and Roanoke
Pink area includes: Northern Amherst, Northern Botetourt, Lexington, Staunton, Waynesboro. 

Thursday, December 5, 2013

The devil is in the details.

No real changes-- AGAIN. Don't mean to bore you.

Let me "retract" my comments that sleet/snow chance have dropped. Model data has cooled and I think we can see a coating to 3 inches depending on location.

Southside- Danville, Martinsville could start as a quick burst of sleet and snow.

460 Blacksburg to Roanoke to Lynchburg= Coating to an inch or two of sleet and snow

North and west, more sleet snow and ice- Lexington, Fincastle, Staunton areas.

Key issue= from 460 south, including Roanoke and Lynchburg the once the sleet and snow flip to freezing rain some of the model data really slows down the precipitation. So, while it will be below freezing, we won't get a ton of ice in these areas. Southside is in the same boat, just less sleet and snow on the front side.

Second wave? So-- we flip to freezing rain and then it slows down. Some data suggest we will have a second wave of heavier stuff late evening as temps creep towards freezing.

Somewhere between late Sunday evening and Monday AM we should break freezing.

Lynchburg Christmas parade is in jeopardy .

Wednesday, December 4, 2013

Morning Update

No real major changes--

Big battle underway for this event between a HUGE SE Ridge (Ridge=heat) Between Thursday and Friday we should hit 70, with nearby cities like Raleigh hitting 80 possible. (that's record heat down there)

Ridiculous arctic front comes through and the exact details are a  bit mushy but we know it will precipitate and some layers of the atmosphere will be below freezing. The one change is my Coating to 3 inches may be generous for LYH and ROA, as it's trending more towards a more mostly if not all freezing rain event.

One model, the CMC or Canadian model is colder and has a longer period of sleet and a little snow. The rest are mostly freezing rain. The rest may and should have a burst of sleet. (Common when dry air is in place to moisten the atmosphere) and mostly freezing rain. I still think Lynchburg and Roanoke temps bottom out in the upper 20's and Danville to Richmond closer to 30 or maybe just 32.

Total precipitation will be between .5 and an inch.. and if it is just a slow, steady freezing rain-- that's the best way to get ice build up.

One thing to look for is as we get close, do the models trend colder from the arctic air density OR is it just because the cold air damming isn't established enough to really push the cold air down to our region. (West of the Mountains will warm nicely and have rain, it's east where the cold air is trapped because it's heavier and more dense)

Look at this dry air at 700 mb Sunday AM on the NAM-- that's 40 dewpoint. This model extrapolated our would have a decent sleet burst.

More updates on FB and twitter and full blog later.

Tuesday, December 3, 2013

Brief update on pending ice event.

Model data has trended as expected. For those of Facebook a lot, some "model" snow based maps were flying that showed 6-10 inches in our region. They were total bunk, not even correct because there was a warm layer above not shown. (AKA-- sleet more than snow)

So, don't expect a big snow-- at all. 

Will have a better update by tomorrow AM. 

Should get a nice bout of rain Friday and Saturday should be dry and cooler setting the stage. Temps COULD be at or slightly above freezing when it starts and quickly drop to the mid to upper 20's for a while Sunday. 

SOME data suggest a decent period of sleet mixing, while others are more beating the freezing rain drum. 

I still like my idea of coating to 3 inches of sleet and snow (especially north and west of Lynchburg)-- think more coating in LYNCHBURG, more as you hit Lexington and Staunton area.. then a decent ice event. If the model data comes in as I think it will, it should be our largest ice event in years. 

Many factors still up in the air, including:

Temps-- ice at 26 vs ice at 31-32 is a world of difference

Sleet/snow-- that tends to coat the group and make ice build up easier on roads, etc. 

Second wave MAYBE Tuesday? (after a warm up)

More late. 

Sunday, December 1, 2013

Possible wintry event next weekend..

Well, November ended up 3-4 degrees colder than normal and December is continued the trend of frequent bouts of COLD air. 

We should have a respite for a few days with some seasonable days early in the week and then a few MILD days with temps reaching the 60's later this week. 


All week an arctic front will be slowing moving east, reaching our area sometime late Friday to sometime Saturday. This air as modeled is VERY cold. 

We have a unique set up with a strong -EPO ( blocking up west of Alaska that is currently pushed north near the Arctic Circle, pushing COLD air to our side of the globe) So, despite other things we need-- +PNA, -AO and -NAO the cold air keeps heading to our area. 

As the front passes our region, it slows down thanks to the SE ridge. Flow aloft turns to the SW and we get what's called "over running".  This will set the table for a possible major to significant snow and ice event. 

How much and When??

Hard to say EXACTLY at this point. 

Some key factors--

1. Strength of cold air both aloft (snow vs sleet and freezing rain) and surface (rain vs freezing rain) Cold air is often under modeled at the lowest levels in arctic outbreak, but sometimes overdone at the mid levels. 

2. Where does the cold front slow down-- Southern VA, Southern NC. SC?? This would tell the difference between more snow and less ice.

3. How much moisture transports into our region? AKA--how much stuff falls out the sky. 

First Thoughts:

I'm fairly confident we see some type of an event next weekend.  I'd guess a period of snow gives way to sleet and then eventually freezing rain. The big story will be figuring how much is sleet and how much is freezing rain. This won't be like that event last week with 3 day old stale and exiting cold air. This will be fresh cold air, maxing out during the event with MORE cold air pumping into the storm.  

Under this set up-- a typical event like this would be a Coating to maybe 2-3 inches of snow and sleet followed by some freezing rain with possible significant ice accumulation. We have a ton of factors in limbo that we don't know yet, but this is a "typical" outcome we'd see. More snow and sleet NW of Lynchburg and Roanoke, more freezing rain south and east of the area. 

Updates will be more frequent with this pending event. Lot's of Christmas events including my daughters FDA Christmas show next weekend AND the Lynchburg Christmas parade Sunday.