Slushy spring wintry mix for Sun.
A year ago this weekend. on Saturday, March 24, 2012, parts of Franklin County and the Smith Mountain Lake area gained a white coating up to 6 inches deep … but it wasn’t snow. An unusually well organized supercell thunderstorm for this region tracked from Patrick County — where baseball-sized hail was reported — northeast toward the Ferrum and Rocky Mount areas and then Smith Mountain Lake. You can click here for a reminder of the event as covered on the Weather Journal blog. Numerous tornado warnings were issued on the storm based on Doppler radar indications of tight circulation but there was no ground evidence of a tornado touchdown was ever found. Low-level wind shear was the only parameter that was missing for a tornado.
We’re not talking about tornadoes or severe thunderstorms locally on the same weekend this year — that’s staying near the Gulf Coast. Instead the warmest March weather on record setting us up for severe weather, a March with a legitimate shot at being one of Blacksburg’s five coldest since 1954 and Roanoke’s 10 coldest since 1912 has set us up for an early spring wintry precipitation event on Sunday. Like most of the wintry 
events when it actually was winter, this one is a murky borderline event between snow, sleet and rain, as the boundary between warm-air advection aloft and cold-air wedging on the east side of the mountains is likely to fall right across our region. Generally, a slushy mix is expected in the Roanoke and New River valleys with minor accumulations (2 inches or less), with more snow and more accumulation the farther north you go, maximized in higher elevations, and less southward. There is some risk, though, that moisture will rush in more intensely than forecast in a slightly colder atmosphere, and, if that happens, snow could come down hard for a few hours and quickly pile up a few (2-4) to even several (4+) inches. A few forecast models have shown this, particularly the North American Model, which has depicted it for several runs. The Weather Prediction Center this morning has a moderate risk of 4+ inches of snow nudging Roanoke and Blacksburg, while also barely having a coin’s flip chance of getting just 1 inch. Spring snow events are known for being mercurial like this, often forecasting busts in either direction. Just a little warmer than modeled in the bottom mile of the atmosphere and it could easily be just cold rain with maybe some mixed sleet.
Most models show two waves of precipitation with the complex and somewhat loosely organized storm system featuring two low-pressure centers, one moving west of the Appalachians and the other developing in the western Atlantic. One precipitation wave arrives during the mid-morning or so and the other on Sunday night into early Monday morning. The first wave has the best chance of being heavy snow, but also more chance of being rain or mix. The second wave would probably be snow, but not as intense. Midday to afternoon snow rates often have to be quite heavy to accumulate much because of the higher sun angle leading to more absorption of solar radiation than in midwinter, even with cloud cover. It is possible some places will see some accumulation in the first wave, have it mostly melt off afterward, then get a little more Sunday night and early Monday.
Bottom line: Expect to see at least some snow in the Roanoke and New River valleys northward on Sunday. Major disruptions are not expected at this time, but do keep an eye on radar and forecasts for changes that could develop rapidly during the day Sunday. Roads can quickly become slushy even in spring, even at 33-34 degrees, if wet snow and/or sleet falls heavily enough. Because of the cold weather, we have not had nearly the same greening of trees we saw in 2003 before the March 30 snowstorm, and therefore would not expect the same level of tree damage if heavier snow occurs, but January 17 showed us that wet snow can still do quite a bit of tree damage and knock out power to thousands even without that. If we start getting above 3 or 4 inches, that would be a concern.
March 23, 2013 - 9:45 AM
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Kevin- Do you think Bent mountain will get higher snowfall amounts tomorrow? My husband, Ron, is playing up at Amhrien’s winery and we’re wondering about the likelihood of the storm impacting this or making travel to the event or coming home from the event difficult. I don’t want him to get stuck up there
Thanks!
Bent Mountain will probably get an inch or two more, at least, than immediately surrounding lower elevations, yes. But if the rain/snow line moves north of the Roanoke Valley, even Bent Mountain might not get much.
KM, So you are saying we will be lucky to see an inch of snow here in Rocky Mount? It sucks that one day we have a forecast that depicts up to 7 inches and then the next its an inch. I truly believe that storms of this nature should be discussed only 48 hrs from the event to insure accuracy and less heart break.
BTW KM thank you very much for what you do. You are truly my go to source for weather.
Mr. Winter: I’m not aware of any forecast that has projected 7 inches of snow in Rocky Mount. I am aware of individual forecast model runs that have shown this (and some still do). It is a different thing to say a forecast model shows something than to say that is what is forecasted.
It is POSSIBLE that you will see several inches of snow tomorrow. WPC has Rocky Mount within its slight risk of 4+ inches, for instance. But the compilation of forecast model data would seem to indicate mix with lighter amounts. It’s a highly variable situation that could shift up or down, even more so than most winter storms.
Amen matt
Agree with KM above. Again…”North of 64 will have more in store”
I mentioned the possibility of the Gulf Coast thunderstorms could rob the energy away and translate this mess away from the Mid-Atlantic. Something to keep an eye on.
The March 30, 2003, event is very instructive of what can happen. That one was expected to accumulate only in higher elevations with brief changeover in lower elevations. But trees were breaking by 8 a.m. in the Roanoke Valley and 4-12 ended up falling over mosat of the area. On the flip side, it looked like there was a good chance of 2-4 inches in late March 2011, but a squall line moving through the South sucked the moisture dry and we got fractional amounts of sleet/snow mix.
If it doesn’t snow tomorrow, you can all blame me. I put the blade back on the tractor Thursday morning and jinxed it.
Here’s 5 reasons right now I don’t buy the NAM bigger snowfall amounts for Roanoke and southwest:
(1) The NAM has a habit of overestimating total moisture within 24-36 hours of a storm.
(2) Even the NAM shows the 0C/850mb line (or 32F a mile up) basically right over Roanoke for hours. That’s just too close to expect precipitation to stay snow for hours.
(3) GFS/Euro trends toward smaller snow amounts, 1/2 to 3 inches.
(4) The Canadian model is heavier than the NAM, but so it was on March 5-6. I can’t remember the last time it was right ahead of the other models on a local winter storm setup. (I do remember it being ahead of all the other models on a severe weather setup during a Plains storm chase one year.)
(5) It’s a Miller B storm. We seldom get big snow from these in midwinter, let alone in spring.
All that said — it might be right. Let’s see what happens.
The NAM is holding course on the widespread 6+ inch idea. Even expands the area of it a bit from last run.
http://raleighwx.americanwx.com/models/nam/12znamsnow_SE036.gif
The consistency is impressive enough to give one pause about whether it might be on to something. Would like to see some of is brethren move its way, though, before jumping in with it too much.
The opposite of comment #10, some reasons it might be worth considering the NAM bigger snow amounts:
(1) Consistency. Been showing the same basic idea every run for 2 days.
(2) NAM sometimes thought to better handle overrunning moisture situations, which the initial wave of this essentially will be.
(3) NAM sometimes thought to handle cold-air wedging a little better.
The March 30,2003 storm put down 2″ of snow in Bedford and Lynchburg with much heavier amounts just west of here. Roanoke got about 6″ of snow but I can’t find any records showing the storm because of the 7 year snow data gap. Even the Roanoke Coop site didn’t record snow for that event for some reason.
On Miller B storms the last one I can think of really working out for us was February 5-6 2010 with 9″ in Roanoke and I measured 7.7″ of snow here in Bedford. We still had a lot of sleet after getting snow at the begining with the big totals over Nothern Virginia. There may be other Miller B storms that had 4+ inches of snow here but I can’t think of any back to the late 1970′s.
Donnie: Feb. 5-6, 2010 was kind of an A-B hybrid. There was a continuous low that stayed south and east of us, but some inland influence that drew enough warm air over us to mix snow with sleet in the afternoon. A few days later, there was a Feb. 9-10 storm that dropped 4 inches in Roanoke, more toward Craig County, and probably less for you that was pure Miller B.
Early December storms in both 2002 and 2003 were Miller Bs, with 4-10 inches widespread, topped by some sleet and ice. Inland low in both of those cases was moving north-northeastward west of the Apps before transferring energy. Cold air was deeply dammed into our area.
I have seen reports of snow bursts in Burlington, NC. Is Burlington in the mountains or Piedmont?
Don’t we love living in a challenging forecast area? Here goes …
Things going for it: 1- GFS heaviest precip now happens with thickness (1000-500) values are 542 or less (and when it’s dark). 2-There is an impressive feed from the north (massive ENE flow field northward). 3-Yeah, NAM is insistent. 4-Canadian does tend to be aggressive, but it doesn’t hurt to have it on board. 5- If the clouds keep us from hitting the mid-50s today, that’s good (Kevin mentioned this early on).
Working against it: 1- I again agree with Kevin that it would seem most of the heaviest precip would be early (NAM also insists on this), WAA (warm air advection) style, before the best return of cold air. 2- Tthe first low holds strength a little longer than usual (still 996 mb Monday 12Z!). 3- It’s never good to have the Euro model totally against you … it’s a darn good model. And, or course, 4- it’s LATE season. Do you realize the sun is as high in the sky now as it is Sept. 19th, the end of calendar SUMMER!
Wally: Excellent point about the sun angle being equal to Sept. 19. The sun angle reaches its lowest at the winter solstice, near the beginning of our cold season.
Mr. Winter: NC disturbance today is the same one that hit Arkansas/Missouri on Thursday. Way way back there, the models were showing it as a possible overrunning snow event for us today, and some even took it down to the Gulf and phased the second piece of energy in the Plains now with it for a Miller A type coastal storm.
The February 9-10 2010 storm was about 1.5″ here Bedford. The Early December 2002 and 2003 storms were both between 5 and 6 inches of snow here. I alway’s thought of those 2 storms as overrunning events, but they did transfer so they go down as the rare Miller B that does work out for us.
New GFS hasn’t finished yet, but looks colder and a bit more moist than previous runs.
Here’s a simulated radar WRF for Sunday at 2 pm. Pretty impressive precip area, but mainly NRV and Roanoke northeastward. (Prior hours did not have much red).
http://weatherroanoke.com/wrf.png
12Z GFS snowfall through Monday morning shows 6+ I-81 corridor and NW (generally from Chrisitansburg northward) and 4+ all the way east to Lynchburg and south into Franklin County.
http://raleighwx.americanwx.com/models/gfs/12zgfssnowdepth048.gif
New GFS really emphasizes the backside snow on Sunday night and into Monday morning.
Even allowing for the spring wet snow 25% discount, if this trends, I think you might see some winter storm watches go up.
Winter ’12 / ’13 – Storm #7 – Call for Forecasts!
Deadline for entries: 10:30 PM EDT SAT…23-MAR-13
Details @
http://newxsfc.blogspot.com/2013/03/winter-12-13-storm-7-call-for-forecasts.html
im doin a ustream on the storm live at
ustream.tv/channel/TheMountaineerShow
GFS has us for 6-8″. I don’t really see it though, heading towards 50 right now! No matter what it will still be some good moisture heading into the growing season. The golfers are biting at the bit for spring to show up!
Around 5 inches of wet snow for the Roanoke Valley, that is what my basement instruments are indicating.
Hey there Kevin or anyone else! Could you post the new 12z NAM snow map just to compare with the GFS!? Thanks a bunch!
Dan: It was in my 10:42 a.m. comment, but here it is again.
http://raleighwx.americanwx.com/models/nam/12znamsnow_SE036.gif
Really, this map is 12 hours short of the GFS map — but it doesn’t matter since the NAM doesn’t have a lot of snow for us late.
Here is a higher res snow output:
NAM/WRF 4-km
weatherroanoke.com/hires_snow.png
The Canadian has gone bonkers … trying to follow the NAM lead
weatherroanoke.com/cmcsnow.png
And a very zoomed GFS
weatherroanoke.com/gfs.png
System looking a little wetter (meaning liquid equivalent). I’m not sure whether the charts really mean any frozen precip, which includes snow and sleet, even snow pellets and snow grains (not freezing rain or rain).
Sleet has a 1:4 ratio compared to 1:10 (usually) for snow, though wet, heavy snow can do down to 1:6.
If they do, then it may be expressed in snow equivalent. That is, 8″ of snow equivalent, but really 4″ of snow and 1″ of sleet. I’ll have to ask the computer guys. It’s just hard to imagine the Canadian model really telling us a foot of pure snow.
Ooops, let me complete the URLs
Here is a higher res snow output:
NAM/WRF 4-km
http://weatherroanoke.com/hires_snow.png
The Canadian has gone bonkers … trying to follow the NAM lead
http://weatherroanoke.com/cmcsnow.png
And a very zoomed GFS
http://weatherroanoke.com/gfs.png
Entered this contest, NEWx. (Re #22, 12:02 p.m.)
Jared…Don’t worry about the temps being at 50-degrees. That is Jack Frost weather compared to March 29th of 2003 when it soared to almost 80-degrees and the next day Roanoke got a blanketed with 6-7″ of very, very wet snow. It was the most destructive snow I have ever seen. The Bradford pear trees and other foliage look like they were in a battle zone. Many power lines down. I hope a snow never decimates so many trees again. Point is…it can be very mild, if not balmy and snow can stick the next day. Hard to believe but it happens!
This is the way it almost always happens in spring, mild to warm the day before a snow. April 1971 had a big snow that was in the 70s the day before. Heck, it was 64 here on the day before our Feb. 19 snow last year. If a significant snow happens, this might actually be one of the colder days we’ve had on the day before a spring snow. A good thing if you want snow, since there aren’t huge drivers for new cold air this time, mostly just a subtle push of residual cold air from this intense blocking pattern, some evaporational cooling, and perhaps some dynamic cooling from the low deepening on the coast. The March 30, 2003, storm had a major Arctic cold front cutting into the rain.
Do any of you remember a heavy snow around the middle of April 1978? Something like 12-15 inches. I remember it knocked the power out at the old White Motors (now Volvo) for a couple of days.
We’ll see what happens for sure. 47 degrees here with a Dew Point of 23. NRV Airport says 43/18. The only thing I know for sure…tomorrow looks like a good day to be inside with a fire burning in the fireplace, and college hoops on TV.
Sending you guys some thunder this morning
to give you what i think will be mostly rain for you..
Active storm though ..and raced off to the east at 50kts.,
Some hail signatures in it..though none here.
Most active about 15 miles south of me..
Mr Winter…Burlington is to Greensboro as Martinsville is to Danville..
Burlington is the next big town east of Greensboro…bout a quarter of the way to Durham.
I wonder why the Canadian model has lowered the sledge hammer down on SW VA? Wonder what that model is seeing? Simple as more cold and more moisture? One foot seems a bit much to me! Taking into account warm surface temps!
The slurry truck hit 221 before 9 AM this morning. Must be expecting something.
Toughest forecast of the year maybe. Confidence is low on my part. Thinking 1-4 area wide lower ends south higher ends north. Potential to bust EITHER way is HIGH.
http://blueridgeweather.blogspot.com/2013/03/my-head-hurts.html
Think any advisories or watches will go out for the Roanoke area, Kevin? Saw where the Canadian was a pretty big hit for our area as well.
Whoa…GFS and NAM moved a little south. Winter Storm Watches in store?
i hope the nam and canadian models r right bring it
When is this suppose to start? I have plans for tomorrow. thanks
Will King Euro speak at 2:30? What say he?
@KM #30
Good luck!
Forecasts can be amended as often as you like right up until the deadline.
Only the last entry counts.
—
NAM and GEM holding on to their earlier solutions.
GFS coming up quick on the outside.
Yep – mild to warm up here. Currently 51 and cloudy. Have seen very little of the sun and there is no wind.
I’m hearing a second hand report from someone I consider very knowledgeable that the 12Z Euro has trended toward the NAM.
I’m still leaning toward 1″ or less at my house…our slightly lower elevation, and general mountain blocking all around tends to cut back precip amounts and causes us to sometimes have more rain than snow compared to other places in the NRV with a bit more elevation to them.
It’s up to a very mild 52 degrees, with a 27 dew point now. Looks like some strong mechanisms to bring colder air in will be needed, assuming my readings are accurate.
Are you thinking about bumping up snow totals now kevin?
I think I might be thinking 1-4 inches at this point for Roanoke/NRV. Big question mark for me is marginal surface temps/ground warmth. Not as much as it could be this time of year, but always a factor in late March. First round may roll in when sun is highest.
Another question is, is how much energy/precip does a potential thunderstorm outbreak on the gulf steal from our precip!? Another factor that makes the forecast tricky! Headaches for sure! when a euro snowfall map comes out could someone post it for fun!? Thanks! I just love my clown maps!
New Euro (12Z) is interesting … range of 4-7″ in Roanoke County, SW with the highest, NE with lowest. Hillsville and WV/VA border areas get 10″. Widespread 5″ around those areas. At least it is up from it’s paltry 1″ (or less) recently.
Any links to the 12z euro anyone?
Kevin…. what is the timeframe of the precip from start to finish in your opinion?
10 a.m Sunday to 6 a.m. Monday would be a pretty good guess, Flutie — not constantly, though. Heaviest on Sunday afternoon, and maybe another period late Sun PM/early Mon AM.
I am so torn right now. On one hand I want snow on the other I want my boys to play more baseball. However its going to be cold and something will be falling, so might as well be snow.
Yeah, just saw a pic of 12z Euro snow map…it has hopped on the Euro train and is taking a ride! I dont know if its over cooked though…has blacksburg/roanoke in the 9-12 inch zone…bigger precip shield and colder are to blame i guess?
SREF (Short Range Ensembles) which utilize output from the NMM and ARW 48 hour models is more like the NAM … and the composite shows enough liquid equivalent falling for 6″ of snow (with low ratio – 1:6), but we know that won’t happen (it won’t be all snow). Mitigating with sleet and any rain, 3-4″ seems reasonable for the area, still. (3 for the Valley floor, 4 surrounding areas, with 5+ in elevated areas.
Temperatures are so critical in the lower elevations (Valley floor) that it may only end up with 2″.
Dew points east, and north, and NW look good.
New automated forecast calls for 2-3″ for Roanoke, 2-4″ Catawba, Botetourt, etc.
New runs, of course, may change all of our opinions.
Dan,,
In my opinion the Gulf does no stealing at
all…in fact much of the precip you get with
a flow from the Gulf is enhanced.
A relatively quick moving low pressure off the Atlantic
Coast or any system that gives u drier air from the north
is more likely a culprit to do moisture robbing…
Your moisture fairies send buckets to u generally
from the gulf or flow from the southwest.
The timing of that flow and uplift is a big factor.
https://www.facebook.com/photo.php?fbid=10151586769916614&set=o.129478830432717&type=1&theater
Here is the king’s snowfall map
As requested … Euro:
http://weatherroanoke.com/ecmwfsnow.png
But note is says based on 10:1 ratio, and it won’t likely be. Thinking 1:8 or 1:6, fudge it down.
18Z NAM is going to be a big hit. Heavy precip and colder tomorrow. Low energy already transferring to SC coast early in day.
Undeniable trends toward colder/snowier look on most models today.
Thank you Camden for the link to the euro snow map. No offense Wally I just like that map better than the one you linked with all the fudge;-).
18Z NAM snow totals through early Sunday afternoon (yes I said early Sunday afternoon)
http://raleighwx.americanwx.com/models/nam/18znamsnow_SE024.gif
Starts much earlier on this run, 7 a.m. or so. Period of rain/sleet quickly giving way to snow.
18Z NAM snow total through early Sunday evening … turn your head if your squeamish.
http://raleighwx.americanwx.com/models/nam/18znamsnow_SE036.gif
Will there be any thundersnow?
NWS- Morristown has Washington County, VA under a WSW from, get this LATE Sunday night through Tuesday afternoon, and are calling for 4″-8″ below 3,500′ (Michael Hogback ‘ville), and 6″-12″ above 3,500′. Again, not starting until LATE Sunday night. I’m confused, and I think so too is NWS Blacksburg, who have not yet updated their forecast as of 4:23pm today. They don’t know what to do.
Wow that would be awesome!!!!
)))))))
Love the 18Z NAM…. now if only it comes true
I cannot take that run of the NAM seriously.
Geez Kevin… How much of that 18Z is for real?
Factor out the NAM being usually too wet, some sleet/rain mix, early spring ground warmth, wet snow compaction, lower snow:liquid ratios than 10:1 presumption of most models, and just being a bit hard to believe, and that could still be a solid 4-10 for a lot of the area IF it’s true
NWS shows from 17z today ,,forecast for ROA..
TAF KROA 231738Z 2318/2418 28005KT P6SM BKN070
FM232300 34003KT P6SM BKN250
FM241100 08003KT P6SM -SN SCT030 OVC090
FM241500 09005KT P6SM -RAPL OVC020
,,,Light snow after 11z…(daybreak)
15z ,,(11am) mixed light rain and ice pellets..
Ill post another later..theyll get off the fence some as
to after 15z timeframe,,
‘
Note north winds today and tonight…then early in the am east wind..
(090 degrees at 5 kts)
Here’s the frame after the one Kevin posted on comment #65..
-
Even if these totals were cut in half it would still be 6-8″ for the Roanoke area.
http://raleighwx.americanwx.com/models/nam/18znamsnow_SE042.gif
To follow up on my other comment, it would be smart to cut those totals because of the NAM’s wet bias and the chance of mixing.
NWS-Blacksburg just posted a snowfall map showing 2-4 inch totals Roanoke/NRV. Scroll down on this site:
http://www.erh.noaa.gov/rnk/emer/emer.php
Haven’t issued advisories/watches/warnings yet except to northwest. May be deliberating about what exactly to issue.
Blacksburg NWS has a new snow map out.
Kevin there looks to be a lot of Rain/storms in the Florida pan handle, could this be a possible moister robber for or system?
Despite model guidance showing more snow, the WPC lowers our chances of seeing snow accumulate.
http://www.hpc.ncep.noaa.gov/wwd/day2_psnow_gt_04.gif
WPC has moved Roanoke out of their 4″+ risk assessment.
http://www.hpc.ncep.noaa.gov/wwd/day2_psnow_gt_04.gif
Raise your right hand and repeat after me…
I…”state your name” promise to not look at the 18Z NAM snow clown map.
Not buying it. I may up my snow totals to a definite 3-6″ widespread event but not 12-18″
on the other hand, the 12Z Euro does show another potential event for Good Friday.
You have to see it to enjoy it fully.
NAM 18Z snowfall
http://weatherroanoke.com/namsnow3.png
Loved the 18Z NAM graphic listed above, as it has SNOW DEPTH rather than snowfall. Of course, that makes a high figure even more remarkable.
Looking closer at latest SREF, some of it’s members are even more unbelievable, with amounts pushing two feet (if equivalent water going to frozen precip). This is INSANE. Okay, plenty of sleet & warm ground. If it comes down hard enough, the latter will not matter as much.
It’s been awhile since I’ve seen 2-3″ of sleet on the ground.
Anyway, lessen for NAM bias, lessen for rain/sleet mix, lessen for ground, etc. Maybe there’s a chance for 4-7″ after all? If more heavy flakes than sleet, there could be power problems. Am not jumping in with both feet, yet. There’ll be more model runs ahead.
Meanwhile, Blacksburg official forecast calls for 2-4″ total for Roanoke.
We’ll get a dusting in SW Noke City. Book it!
Can we assume the NWS-Blacksburg is completely discounting the NAM showing widespread 9″-14″ snow amounts across NRV and Roanoke? We have the most significant late season snow storm of the past 10 years at our doorstep, and they have issued no advisories except Bath/Greenbrier (and Ashe, for upslope). Interesting.
I was very surprised to see far SWVA under a Winter STorm Watch from tomorrow night into Tuesday. This is backside stuff and not on the front. I will be surprised to see it materialize but I could be surprised. I am a snow lover but as I have said before, I am ready for 70-80 degree weather.
Mass hysteria.
New blog post is up. Not saying anything revolutionary, just mainly as an anchor for more discussion.