April Showers (SNOW) bring May Flowers (Hopefully)

Well in what will likely be remembered as the oddest storm of the season ( like that is saying much this winter) lets face it - - we missed this one big time.  Let's look at what went wrong.

Originally, this storm was supposed to be a rainmaker   From a distance this storm looked like it would take the ideal winter storm track for us here in SWVA.  The only problem was.... it's April.  The thinking was the air would not cool sufficiently regardless of the track, so we called for rain.  Well Wednesday, the NAM and the GFS models - - both which get better as we get closer to events BOTH suggested that cold air would stay in place for just enough time to produce a heavy wet snow.  This was a sudden shift.  ON closer examination however, it is one that I should have seen coming from a week away.  Why?

1)  The air in place PRIOR to the storm was exceptionally dry and cold - - and of Arctic origin.  Yesterday Morning, when the dew points were in the teens and temps were in the 30's, I KNEW we would see some wintry precipitation.

 This process is known as "evaporational cooling".  When moisture falls into cold, dry air, it moistens up the air, but subsequently cools it as well.

2)  While snow starting out was expected, it was not expected to last THAT long.  We had the perfect setup with a high JUST off the NE coast.  This only reinforced the cold air that has been gripping us - - especially over the NC and SWVA Mountains.

3)  At the same time - - moisture arrived at a perfect angle from the SW to maximize heavy precip at the height of the cold air.  One thing we look for when tracking precip here is "what is it doing in NE Tennessee - - and it poured there all day yesterday.  We knew this heavy precip was coming - - and it came at the absolute PERFECT time.  An hour or two later - - the cold air loses it's grip just enough to cause rain.


If you noticed - - again western slopes did not see much of anything.  This is due to the "cold air wedge" that so often influences our weather.  Easterly winds really helped keep the cold air banked against the Eastern Mountains.  North of Roanoke - - didn't do so well either.  Why?  The precip arrived just late enough AFTER the high to the NE had started to slide east.  The angle was also more favorable for a NC/SWVA wedge than a Shenandoah/Central Va Wedge.

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All in all - - I think this is THE END to what is probably the wildest winter season I can remember.  A couple things to take note of:

1)  First measurable snow was Halloween - - last was April 4th.  That's a 157 day season - - which is a new record in Blacksburg.

2) Roughly 29 inches fell in Blacksburg - - which is right at normal.  26" in Carroll County at my house (roughly for both).  What started out as a very warm winter turned rather snowy in March - April

3) One big storm in January - - followed by several 1-3" type snows - - they added up quick

4)  Spring Winter:  Two major snows in SWVA in Spring:  (March 25th and April 5th)

Finally the last major point I want to make about the season is this:  We only saw one snow that the Shenandoah/Nova shared with us.  The January snow, all of the little ones, and this most recent one, were all strictly restricted to SWVA.  The Palm Sunday storm we shared with the Shenandoah/NOVA  -- and the early March storm was strictly a Shenandoah storm was well.  They also had some snow around Christmas when we had ice.  A very atypical thing to have so many events that affect us but not them in one winter.

Also -- upslope NW snows - - really pushed Blacksburg over the top.  Roanoke comes in at 19" but I think we can all agree they had more "impactful" snows than we did.  Not sure on the final number - - but they seemed to have more moderate snow events than the NRV did - - while we had plenty 1-2" type storms.


How will you remember this winter?  What started out as such a lousy winter turned into a fun year.  I wouldn't call it a snowy one - - just a fun one.  Forecasting wise, one of the more challenging winters I've seen - - with so many borderline events and diverse setups.

I'll leave you with this - - a rough shot map I drew by hand based on reports for final snow amounts from yesterdays storm.

My Head Hurts

Complex forecast going ahead.  Here is what looks to be happening . A low pressure system will ride west of the Apps into Kentucky, while at the same time an area of low pressure will parallel it up the coast.  The energy will eventually transfer to the low off of the Mid-Atlantic Coast.  As always, Carroll County seems to be on the line.

The setup is similar to that of March 6th, except cold air wedging is MUCH stronger this time around.  Consequently, the cold air is deeper and will be harder to scour out.  For this reason - - I think a couple of inches of snow is possible on the front side of thing.  Known as Warm Air Convection; we will see an "arm", or band of precip move in from the SW tomorrow.  I expect precip to fall as snow/sleet in this band over the vast majority of the region.  Just how much sleet mixes in will be key, but I think 1-4" is a safe bet with this initial band.  Also - - expect this band to be strongest and heaviest from 460 SOUTH.  (It will begin to fizzle wants it gets into the Shenandoah Valley).  This is key because heavier precipitation rates mean a better chance at staying snow/ and or sleet.  Really thinking this is going to be more like 1-2" of mainly SLEET - - but a few higher totals where snow stays the longest is possible.  A very slushy type deal

THEN - - the bigger question in my mind is just where does that energy transfer take place.  Given that there is already a low off of the NC Coast - - I think this happens a bit earlier than most setups when low's ride west of the Apps.  Just exactly where this takes place will be crucial.  Once this transfer happens, heavy deformation band snows will wrap into the area where this transfer takes place.  Most computer models have this happening NORTH of our Region, but some have trended farther South.  For now I am sticking to my initial thoughts and think this thing happens JUST north of our Region.  So the steady/longer snows happen NORTH of Roanoke.  - - About 12 hours after the first "thump" comes through and drops a wintry mix.


Bottom Line:  For Roanoke, NRV, it is all about that first "thump" that comes through.  Only lasts about 3-5 hours.  If this stays all snow, we are talking 3-5".  If it stays mainly all sleet - - we are talking 1-2 of slush.  Tough forecast.  I am leaning towards more sleet suppressing amounts.  Everything has to be perfect to realize higher amounts.  Threading the needle but it appears possible

For Shenandoah/NOVA - - you don't get much from the front end.  Your snow comes as the low transfers energy to the coast.

Wintry day appears likely.  Whether it is mainly snow or mainly sleet will make all the difference between 1" and 4". .

Final Snow Map

FINAL SNOW MAP. No big changes. Heaviest snow stays NORTH of I 64. Will be a close call for those south of say US highway 60. Sharp cutoff. Amounts increase RAPIDLY north of here Confident in Roanoke - Bedford - Lynchburg South seeing <2". Some snow showers will rotate in over the NRV/ Roanoke Valley's that COULD drop an inch or two - - however it WON'T be widesrpead. Favored Upslope areas look to be the biggest area of change - - I hadn't accounted for backside snow in my previous map - - and it looks like they get some. Especially South of the Virginia border. Here 1-4" are likely in typical upslope areas - - areas above 4k' will likely see at least 6" however. Very typical upslope event. 

Selected Cities going from South to North:

Boone - 3" - - Upslope on Backside
Bluefiled - 3" - - Upslope on Backside
Galax/Blacksburg/NRV - Dusting - locally 2"
Roanoke <2"
Bedford 2"
Lynchburg 1"
Lexington - 6"
Staunton 8"
C'ville - 7"
H'burg - 12"
Winchester - 15"
Leesburg - 13"
Breezewood, PA - 13"
Altoona PA - 5"
Gettysburg - 9"
NYC - 5" (much more in Hudson Valley)
Western Mass - 6-10"

First Snow Map - - Thoughts Welcome

Well SWVA let's face it - - we got ours in January when those North of Roanoke got the shaft.  Appears karma is catching up to us.  Check the snow map - - words after for more in depth.

Here is my first snow map (will be refined to a more local level tomorrow at final call).

The essentials: Roanoke SW stay in light snow showery type stuff. There will be snow flying - - but not heavy stuff. Very possible that somewhere in the NRV/Roanoke gets a couple inches in a heavier band that breaks off - - very possible someone gets NOTHING. The main deformation band will be North and East of our area, so what snow showers we do receive will not be steady and will rotate in from a North/East angle. It WILL snow. You will see flakes and you may see a white ground -- very spotty however and NOT a big deal. UPSLOPE areas (Bluefield, Beckley, Mount Rogers, Boone) - - get an inch or two on the BACKSIDE of the low (Wednesday Night) - - typical upslope type stuff, again, nothing major.

From Fincastle to Bedford to Lynchburg is a highly uncertain area still. I have you guys in 1-4" but that could very well bust as well. I don't think you see much more than that, however. This area will extend east into Buckingham/Appomattox counties along the 460 Cooridor into Richmond.- - south of 460 amounts drop off QUICKLY. IT IS THIS AREA WHERE I HAVE THE HIGHEST AMOUNT OF UNCERTAINTY. A small shift north and you are hanging dry. Best guess here: Think 1-2"... but 4-5" not a total shock if it does happen.

It is North of 64 (Lexington - Staunton).. from Lewisburg to Covington to Lexington where I expect snow amounts to increase rapidly. Fully expect Lexington, Buena Vista to see 4-8" of snow. This area will expand east into Charlottesville and extend East Southeast into the Central Virginia Piedmont. Generally along and NORTH of US HIGHWAY 60.

North of Staunton into the heart of NW Virginia I expect the highest amounts 8-16" generally, with no doubt some places (probably along the Parkway) getting up to 20"+. Generally along and NORTH of 64 (north of Staunton) and West of 29 (West of Charlottesville). EAST of here into the Northern Piedmont and DC Metro/Baltimore Metro I expect 6-12", however some rain will likely hold accumulations out of the double digit range in most spots.

Selected Cities:

Leesburg - - 10-15"
Harrisonburg 12-16"
Staunton 8-12"
Lexington 5-7"
Bedford 1-2"
Lynchburg 2-5"
Hillsville - <2"
Bluefield 1-3" (NW Backside Snows)
Roanoke <2"
Richmond 3-5"

BOLD

After POURING over the data (honestly guys I've slept 3 hours in past 30)... I'm going to make a very BOLD call.

FOR THOSE SOUTH OF HIGHWAY 460 - - I DO NOT expect this to be a major deal. IN FACT - - I could see some areas not even seeing a white ground. Now certainly I do think some light snow falls in patches of this region, but as a WHOLE, significant snow is avoided in this area. -- this is a very BOLD call and a very different call than what has been advertised. However, if you've read my posts carefully you can clearly see this area has been my highest area of uncertainty - - and that uncertainty is starting to become somewhat clear.


FOR THOSE BETWEEN 460 and I64 - - there is still a level of uncertainty. I DO NOT think you see historic snowfall amounts - - but a few inches certainly are still in play IMO.


For those NORTH OF I64 . Particularly NOVA. This appears to be your storm. The "bulls-eye", the historic March storm, the "crippling" - - looks to happen here. along and north of I 64 specifically.

Let's go into a bit of the reasons WHY I think this happens.

1) The piece of energy coming into the Northern Plains is coming in significantly further East than what was modeled yesterday. This has been a very clear trend and is not just one model run. It has reflected more so and more so with every run. The consequence of this is that the piece of Upper Level Energy we talked about yesterday is going to have to take a VERY STEEP NW-SE angle to dig far enough South - - that does not appear likely.

2) EVEN if it were to dig far enough South - - it appears the Block we talked about is shifting to the East - - this will keep the ULL positively tilted longer - - meaning it doesn't explode til it is EAST of our region.

3) The steeper track will likely result in more of a NW flow resulting in downsloping winds drying out the atmosphere.

All in all this results in a whole lot less precip as a whole over Southern Virginia - - and the storm not bombing out til it is off the VA Capes. Remember in my blog post yesterday I stated that a track like that historically, is MUCH more likely - - well that appears to be coming to fruition and history appears to be winning.

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LOTS of hype around this storm - - and understandably so. SOMEONE is going to get a foot of snow. I have narrowed it down and think that it will be NORTH of I64 into NOVA. Important to remember when hype is so large around a storm, it is crucial to make sure you do not over hype yourself - - and that is what I am trying not to do. The Mid Atlantic is a large region - - and when hype is so large around a storm it is easy to get caught up and think that it is automatically you. To me, it is JUST as important if not more so to warn those people who think they are in line for a big storm, when they are not. This tempers expectations and in my mind, if it verifies adds some great credibility.
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I made a post yesterday saying I had a high confidence that 3"+ is possible from NC to DC, and quickly deleted it. I did this because I realized given the track and the overall setup that it was not going to happen like that.

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TO RECAP: I AM OFF THE WINTER STORM TRAIN FOR SOUTHERN VIRGINIA. YES I know this is a very BOLD call - - I am aware that some models still kill us with snow. I've seen this song before however - - and we typically DON'T do well when it involves Northern Energy diving in from the NW in any way. It is simply HARD to get it far enough South because of our latitude. Think of a "Miller B'.. when a storm rides up west of us, then redevelops off of the Coast - - kinda the same thing. Hard to get that energy to transfer fast enough to snow on us. MOST of the snow modeled for us came in on a deform band rotating in from the North - - the more I look at it the more I think I realize - - and the models start to realize too, that it just isn't likely.

1) Southern Virginia - - minimum impact. Patchy light snow but nothing major.

2) 460-164 - - potential for several inches but believe major amounts will be largely avoided here. HIGH uncertainty here as I am not confident these amounts will even verify -- still worth noting.

3) North of I 64.. say Bath County to Lexington -- north into Nova - - significant Winter Storm with the highest impact.

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AGAIN BOLD CALL HERE - - AND I WILL BE MORE THAN HAPPY TO EAT MY WORDS WEDNESDAY IF IN FACT I AM WRONG.

Maybe the last... but loudest.. train to Kitty Hawk

So as I'm sure you have heard by now there is a potential storm coming next week.  Let's kinda slow the talk down a little bit here and talk about what we are confident in happening.

1)  There will be a significant snowstorm somewhere in the East next week
2)  It appears to be a potentially major (12"+) storm - - but we are not certain where exactly this happens

I'm confident in those two things.  Now let's talk about what this could potentially be for WHERE it hits.  I do believe this has potential to be a historic crippling snow for somewhere in the Mid Atlantic - - let's talk about that.

1)  Confident that somewhere will see 12-24" of Heavy Wet snow over a fairly large area.  Impossible to tell exactly where.  But Power outages - significant tree damage appears likely in some place.

2) Heavy snowfall rates - 1-2" an hour... picture January 17th of this past year on a much large scale.  For Carroll County this was a bad storm - 12" of heavy wet snow.  It appears that this magnitude of a storm could happen on a much larger scale.  If you recall Interstate 77 was shutdown in Bland County and was all but shut down from Fancy Gap to Wytheville.  Appears that this type of standstill will happen SOMEWHERE - - on a larger scale with this storm.

To summarize, I am confident in a Major Storm - - Crippling - - Historic - - for somewhere in the East.  Exact locations to be pinned down.

NOW let's talk about the setup and some things that can possibly clue us in.

The storm setup is one that for snow at this latitude in the Mid Atlantic is pretty atypical.  As you all know, we are in a rather cold pattern, with a trough in place over the Eastern United States.  Early next week, a strong piece of upper level energy, just now entering the Pacific NW, will track across the Northern Plains.  What is key here is 2 things  .. 1) This is not of Arctic Origin - - Pacific, meaning it is likely a stronger piece of energy.  2)  It is a strong piece of Upper Level Energy - - which I'll expand upon later.  Long story short, it is not your typical "clipper" type of dry energy coming out of the NW.  AT the same time, a small surface low will form in the South Central Tennessee Valley and ride up west of the Appalachians.  As you know, typically this is NOT a good track for snow in our area.  In fact, we will probably see some rain on Tuesday as a warm front with the initial surface low passes somewhat southwest of our area.  However, what is KEY here, is the Upper Level Energy diving through the Plains.  This is a STRONG piece of energy and will dive south as the jet stream has a trough over area.  What essentially going to happen is, this ULL, the stronger piece of energy will become the stronger piece of energy.  It will become Vertically stacked, and essentially blow into a major low pressure system wherever this happens.  The term we use for this is "digging".  How far South does the ULL, or that energy over the Northern Plains "dig".

here you can see the "track" of the ULl crossing NC.  This would be a brilliant track for snow from I40 North

There are some signals that show us this will happen at a latitude that is rather unusual for this time of year.  The big one here is this area of high pressure over Eastern Canada - - otherwise known as Blocking.  For days I have said that I don't think this will setup and HOLD.  It appears that it won't hold.  It will shift and breakdown after next week.  However, it does appear more and more like it will hold in place enough to shove this ULL south of the Ohio River.  That is critical because typically, it doesn't happen that way.  A typical track is somewhere north of the Mason Dixon Line, but again, the blocking appears to be strong enough to force this ULL south of the Mason Dixon Line.  This tells me that this low will explode likely somewhere over the Carolina's or Southern Virginia.

This is an image of the Block over Eastern Canada.  You can see a MASSIVE area of High Pressure preventing the storm from cutting essentially North of Virginia.

That being said, the key thing is the track of the ULL and where exactly it goes.  Every model today digs it into Upstate South Carolina, from here it blows it up, goes negative, and tracks ENE across Eastern NC and off the Coast.  This would hammer Western NC, Every square inch of Virginia, up into Southern PA with HEAVY snow.  

Today's EURO run at the 500MB level.. here we can see thw track of the ULL - - good for snow over Virginia.  You can se the ULL begin to go negative in this frame.  

Here is the GFS, a bit courser of a model, but very good agreement between the two.  

However, we haven't seen too much consistency in this throughout the past few days.  Yesterday most models kept this north of here, tracking it across VA and off the Delmarva Coast. This would shift the snow to the North.  Some of the models dug the energy all the way into Georgia and off the South Carolina Coast - - missing Virginia to the SOUTH.  So again here, there hasn't been a consistency over the past few days within the operational models.

If the ULL tracks between these two red lines Virginia Would get crushed.  Every Model shows a track between these two lines.  

HOWEVER - - when looking at all of the ensembles and operational models; there appears to be a consistency taking this ULL no further NORTH than the VA border and no further SOUTH then say Greeneville, SC.  This tells me that the areas between I-40 in NC and the Mason Dixon Line have the best chances at seeing this widespread major storm.  The I81 Corridor in Virginia appears to be the best place to be at this point.  There is wiggle room to the North, and wiggle room to the South.  Basically, take the data we see today, barring no major shifts in the track, Virginia appears to be on track for a Potentially Major, Crippling Late Season Winter Storm.  

For fun and games, here is the EURO snow map for today.  Has 8-16" from VA/NC border north and a bullseye of 1-2' over the Shenandoah.  NOT a forecast, just a model output.  

Some closing thoughts.  The NC/VA border counties appear IMO to be too far South to be in the bulls-eye at this point in time.  Yes with this track it appears we will see some very good snows.  But it appears the heaviest snow could setup north of us over the Shenandoah Valley.

YES NOVA- - This storm looks to be very large - - so I think you get in on it too.

North Carolina is the big question mark  - - particularly south of I-40 or US 421.  Need it to dig a bit further South.  Do think far Northern NC  is very much in the game though.

I won't put out a snow map yet.  Remember, we want a track along or SOUTH of Interstate 40.  A track further North of this is still possible.  I will post an update tomorrow and again Monday as the storm draws closer.  We are within almost 3 days of the storm now so we are entering a window of Higher confidence.  The specifics aren't important now - - just know that the Mid Atlantic will likely bit very hard in some portion by Thursday Morning.

Ice Ice, Baby

Hey folks, quick update to talk about the ice storm coming tonight.  Been very lax on the blog as of late - - it's school -- trying to finish on a strong note :).

ANYWAYS, this is going to be a significant event for some, so it is worth a blog post.


The situation:  A closed off upper level low is currently wrecking havoc on the central plains dropping between 1-2' of snow from The Panhandles of Texlahoma to Kansas City.

 At the same time a warm front, combined with a forming low along the Carolina Coast will throw widespread precipitation over our area tonight into tomorrow.  For most of us, this will fall in the form of rain.  For those in the New River Valley/Roanoke and Shenandoah Valley's - this will fall in the form of some light ice transitioning to rain.  For those along the Blue Ridge south of Roanoke however, this will fall in the form of freezing rain and sleet.  It is a unique setup, one that is very local and very elevation/orographically dependent.  I will try my best to explain.

When winds blow from the East, they pick up moisture from the Atlantic Ocean.  Easterly is an already "cool wind direction".  When the winds blow from the East, they hit the Blue Ridge Mountains (Highlighted). When this happens the air rises, and condenses. Because this air is from a maritime origin (moist) when it hits the higher ridges condensation occurs at a greater/easier rate than say if the winds were from a continental air mass (less moisture).  This type of set up is known as "Cold Air Damming"; "Cool Air Wedge" or simply "Easterly Flow".  This is the type of setup that typically leads to many days of fog and drizzle and cool temps even in the summer time.  A big reason while Fancy Gap stays so foggy is this type of setup.  This type of setup is what will happen tonight.  Winds will blow from the SE and create a "wedge" of cold air at the surface.  Not only will this create a wedge it will also aid in precipitation as we will see some upslope enhancement.  (Checkout Google if you don't know what that is).  This same upslope enhancement will also only further aid in the development of colder surface temperatures.  This is a very literal "dam" so to speak, as the higher ridges of the Blue Ridge literally block the cold air from progressing to the West.  It is for this reason, that places like Wytheville, Bland, Abingdon, Marion, and Beckley can be 60 degrees while Hillsville is 35.  When the air blows down the opposite side of the Blue Ridge - - it descends and "dries out", speeds up, warms up etc etc.  This allows enough warming at the surface to rise these temperatures above freezing.  Hopefully - - that explains the setup.

Here we can see how cold air will pool on the East Side of the Blue Ridge in Situations like this.  

Above is a big reason why the highlighted areas will stay coldest the longest.  In this type of setup, winds will quickly blow in from the SW in the Clouds - - and if there is nothing challenging them at the surface, then the surface will warm too.  That is why many areas like Bluefield/Wytheville/Bland who are below freezing now, will actually RISE above freezing throughout the night.  In the white however, as winds at the surface blow from the East, the "dam" described above will only strengthen, and temperatures will stay below freezing at the surface while they warm significantly in the atmosphere.  This will create freezing rain.  

The image below is a "bufkit sounding" or a graph showing the projected model outputs for freezing rain at a selected location - - this location is Fries.  As you can see if you read the graph, the model average outputs .35" of freezing rain.  Very good model agreement that .25" of Freezing Rain will at least occur. 

Map Below -- basically this will not be a significant even for everyone.  Many areas will see ice to start, but quickly change over to rain as the surface warns.  However, places highlighted in Red and Purple, are areas that will be stuck in the "dam".  It is these areas, especially South of Roanoke above 2500', that I expect to have major ice tonight.