Sunday, March 12, 2017

How Much Snow Monday night and Tuesday??

I'll start with the details and then elaborate for those who care!

New River Valley up 81 to past Roanoke 3 to 6, up to the Blue Ridge.

East of the Blue Ridge - North of Altavista , Cutting north to Farmville , Including Lynchburg 2-4.

Martnsville, Danville, Ect coating to 2 inches.

If this is a Dud: Ending as snow in NRV, LYH and ROA and all Rain southside.

If we over achieve, 4 to 8 NRV, ROA and LYH, 2 to 4 down to Martinsville and Danville.

If this were January, we'd be looking at 6-10 inches region wide, maybe some bonus snows in the north and east areas. It's not too warm, it's just March, mid March at that.

To not overcomplicate my discussion,  we have storms that are phased and unphased, Phase, simply put is when 2 branches of the jet streams, and their upper air energy work together.

Early on, a phase seemed likely, then models moved away from that. Today, they are more phased and the net gain is best snows should be west of the Blue Ridge.

What a phase does is strenghten the low fast enough to cool the air from top to bottom by creating strong vertical motion upwards.  The models currently strengthen the low a little sooner and enough cold is in place along -81 for mostly snow, or rain changing to snow. As the low deepens and pulls east a rapid change over takes place. However, the snow ends pretty quickly after it changes over with maybe 2-3 hours of accumulating snow and then 2-3 hours of light snow and flurries.

Roaonoke and NRV, a mix of snow, sleet and rain develops late afternoon, changing to all snow in the evening. Snow will be briefly heavy. Snow ends in the pre dawn hours. 3 to 6 on colder surfaces, slushy mess on roads, etc.

Area including Lynchburg: Rain and sleet develop, maybe all rain for a while then changing to snow. Snow could be heavy an hour or three, before ending as 2-3 hours of light snow and flurries. It's gone by sunrise with 2-4 inches falling, mainly grassy areas. The roads will have some slush on them..

Southside. Rain and maybe a little sleet ending as snow, coating to 2 inches.

Crazy talk: In my "weather chats" with various people I've predicted that if the  low deepens to 995mb before Cape Hatteras we see 4-8 in all areas except southside. I still believe that. I think we miss it by 50-75 miles. (AKA, Past the VA/NC border.

More Crazy talk: Pretty good odds school is out Tuesday. Snow will be gone by noon. Gone, as in melted.

Even More Crazy Talk: Winter is hanging on a little after NO winter. May need to blog later about other events.

What can go wrong? If the low is SLOWER deepining, we get some rain ending as lighter snow, but no accumulations to speak of.

If you're up, the snow may rock a couple hours nice big flakes from 10pm to 3am.
Thunder, as the low deepens with both the rain and snow is possible.

Huge event just north of DC. My baby sis lives 20 miles NW of Philly near where I was raised, I think she sees 12-20 inches.

I think that the NWS will go Winter Weather advisory for most areas NOT southside and MAYBE winter storm watches/warnings for Amherst, Bortetourt and Rockbridge Counties.

Doubt I will make another full blog. Thank you for the "ad clicks"of appreciation.

 I will update with model runs, and updates, upgrades and downgrades on social media. Remember you can follow my FB Page, VirginiaWx  me personally, Keith D. Huffman, (do a FR or follow) and/or twitter which is VirginiaWx

Friday, March 10, 2017

Sunday looking small- Monday- Tuesday Standing Tall

First, Sunday-- Southside and Mt Empire/NRV may get more than a coating but not big deal .  Roanoke-Lynchburg,  flurries and some light snow, not much more than a coating. Not a big deal. The energy got sheared out and suppressed. I don't think many churches will be looking at closing except the extreme southwest areas near Hillsville.

Monday into Tuesday looks like a legit good threat. 5 days out, some changes will happen, but It seems things are slowly coming into focus.

A low pressure, aided by the "lack of storm"Sunday will form in the Gulf of Mexico and move from a point east of Charleston, SC to just east of the VAB. A clipper type system with some northern energy is moving towards us at the same time.  The models have moved away from a strong phased system, but there is some interaction which helps the storm get stronger.

You all know that I like snow,so this is pro snow-- if you want snow

1. We want the low stronger, faster.
2, We want it close enough to bring the best moisture, but far enough to not change over.
3. To maximize accumulation, a little slower on the onset to avoid the March sun.

General Pitfalls:
1. It won't be all snow in southside, It should start as snow, mix with sleet/rain and then end as snow.
2.The sleet line may challenge forecasts all the way up to the Blue Ridge Parkway, including Lynchburg.
3. Western regions COULD see a little less precipitation hence a little less snow.

General ideas: WAYYYY to early to set out calls at this time, but I want to give a heads up to the impact possible. This is clearly subject to change.

 Martinsville to Gretna to Brookneal and south will mix and a broad 1-4 inches of snow and slush seem possible.

Every where else,  including Blacksburg, Roanoke, Bedford, Lynchburg  4 to 8 inches of snow seem like a good starting point. We have plenty of time to fine tune and adjust these based on the exact tract and strength of the low pressure.

I'd like to see at least 4 in LYH and 6 in ROA to continue the double digit snow years to 5 years.

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Wednesday, March 8, 2017

Snow still on the table, maybe even a second storm.

Quick update this AM:

1. Event 1, Saturday night into Sunday is still on the table. The storm trended south, as expected and is also weaker (For those wondering, it had 10-14 inches region wide a couple runs of the American model) The Euro model is weakest and most south.

A. Can't totally rule out the weakest, most southern track.
B. The big, 10-15 inch event was never really an option.
C. Light to moderate snows still on the table. Light to moderate, 1-3, 2-4, 3-6 type events. This is not a lock yet.

2. Trends are for a second event "maybe" Tuesday.  This could form just a smidge north and miss our region or be just a small event a blow up just to our northeast.

A. The Canandian Model is very agressive with this storm, give a NICE storm (but little Sunday)
B. Euro forms it but WAY north for us.
C.GFS is coming around to a small event Sunday and small/moderate event Tuesday.
D. Temps could be an issues with this, especially east of the Blue Ridge.

My thoughts: Even with the weaker solution, I think we see a slow shift north in this event Sunday. This won't be a "huge" but a decent event is possible, and a smaller event is likely.
Tuesday: 6 days out-- A lot can change, not too confident for our area yet. I like the areas north of Philly for event 2.

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Will continue updates on model runs at noon today.

Monday, March 6, 2017

Yes, the snow talk is legit..5 things you need to know about the weekend snow potential in Roanoke, Lynchburg, Danville and Blacksurg.

But, 5 days is a long ways away.

I try to communicate the uncertainty when I talk storms and explain what can go wrong, because things will go wrong. 5 days is forever and we are currently on the southern fringe of a storm. Usually, the north trend would seem huge and we'd already be telling you yeah, models says yes but the end results will be north of here.

There are occasions where storms trends south.. those usually have strong confluence and/or strong cold air advection. This one currently has both..

So- basically a storm slides to our north Friday and drags a cold front through. Cold air is still pushing in as the storm approaches form our west. The blocking/confluence forces the storm to our south (EG, near Nashville, to Charlotte then reforms off the NC coast) Yes, it's march, yes- we are having a very warm winter but our weather history is littered with storms that had very warm temps the day or three before the event.

So here are 5 key things to know!

1. 5 days out is a long time and things can and will change. Anyone who tells you "exactly" what will happen is just guessing.
2. There is reason to suspect there could be a further adjustment south which is great if you want snow because of confluence/north trends.
3. Beware of snow maps on FB, what your app says and anything old floating around. I've had someone tell me "it's supposed to be 50 saturday, my app just says rain, etc) Bloggers and really anyone with a computer can pull up the latest model data. There are legit trends that point towards a storm.
4. If there is an event, timing looks to be Saturday late into Sunday. Literally all types of precipitation are possible meaning snow, sleet, rain and freezing rain. All options are on the table-- from a mostly rain event to a mostly snow event. 2 runs of the GFS push the rain/snow line right up to 460 from Roanoke to Richmondand ring out a good bit of snow really fast.
5. Model data at this point comes in every 12 hours, except the American Model (GFS) which runs every 6 hours. Each run should help clarify what direction we are going in. And, Relax--it's a March storm. Even if we max out snow and get a nice event, roads are much easier to clear in March.

2 Cool maps/graphs...

1. This is a composite of matching patterns based on what the models show 5 days out. Our region averages out to a 6-8 inch snowfall.

2. A list of those analogs and explaining what events are popping up. 

So, those are the best matches at 300 mb for the upcoming event. A perfect score is a 1.. Some of the bigger events listed.
2/20/83-- 18 inches Roanoke, 15 Lynchburg.
2/15/03-- Big sleet storm. 3-7 inches region wide.
1987 1-25  18 inches Roanoke, 13 Lynchburg.
3/12/1993-- 30 NRV, 19 Roanoke, 15 Lynchburg.
1/20/2010--8-15 inches region wide.

So, point being we have some potential for some type of snowfall.
My thoughts match the analog map listed. I believe Winchester to Harrisonburg to Leesburg have the best shot for a 6+ inch event. Next area would be DC Metro down to CHO to Fredricksburg-- slightly less chance. The next bracket would include Roanoke, Lynchburg and Richmond. I think we see a shift south per the pattern but then the storm nudges north late, which always happens. Of course, all the midnight model runs could lose the event too :)

Will try to do a blog tomorrow evening and will tweet/post more during model runs. Feel free to share this and ask questions if you have them.