2009.02.27
Time to take a few snow guesses for this weekend
It's getting close to time to start throwing our hats into the great pond of meteorological mayhem and start making some predictions on this winter storm that will affect all or part of the Southeast, Appalachians and Mid-Atlantic region. The one thing that appears very likely now is that there will be a substantial storm system, coming in two waves, over the next 48-72 hours. The first wave arrives Saturday, some rainfall as Gulf of Mexico moisture overruns an increasingly cold surface layer. That rain may eventually mix with or change to sleet and snow on Saturday evening, but may end before it gets too carried away. A few inches are possible north and west of Roanoke, but a ground-whitening layer of slush would probably be the most to expect in the Roanoke Valley by Sunday morning. The bigger show is Sunday, when it appears quite likely that a strong low pressure system will form at the surface over the Southeast U.S., responding to a potent upper-level low moving in from the northwest. The track of this storm is very much in question, but it does appear it will pass quite a bit to the southeast of us. That's usually a favorable track for snow in our area, unless it goes too far southeast or doesn't throw moisture back far enough, which could leave us dry. Though right now I would think somewhere southeast of us would be the bullseye of heaviest snow (and the linked HPC map for Sunday night and Monday concurs, though even there, Roanoke is on the edge of moderate risk for 4-plus inches), I think it's going to be hard to miss the snow entirely come Sunday. Not impossible, but difficult.
Here's a range of probability forecasts for various amounts of snow for Roanoke, totalling snow that falls Saturday night through Monday. This is the kind of system where the amounts probably won't differ a great deal between the Roanoke and New River valleys ... NRV may get a little more Saturday night, but I could envision situations where Roanoke's more easterly location could mean more snow than NRV come Sunday night. Less than 1 inch includes zero, flurries and a dusting ... at this stage of a long winter season, it's all the same to me.
Less than 1 inch: 40 percent
1 to 3 inches: 25 percent
3 to 6 inches 20 percent
6 to 12 inches; 10 percent
12-plus inches: 5 percent
This is my personal best guess on probabilities of various snow amounts, and I will update as the weekend progresses. Feel free to offer your comments as we watch winter's ninth-inning at-bats.
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I would say maximum of 2 inches based on gut feel for most of our area, with the higher amounts in the far south and eastern areas, or in WV where some of the upslope winds may squeeze some out on the backside of the storm. I feel that while the inch-drought for snow may end for Roanoke, that this system just won't produce anything memorable for the area.
Comment by Other John — February 27, 2009 @ 5:47 pm
In case you're curious ... the swirl of clouds up over Nebraska and the Dakotas is the upper-level low that is expected to be the trigger for this weekend's mayhem:
http://blogs.roanoke.com/rtblogs/weatherjournal/files/2009/02/sat0227.jpg
Comment by kevinmyatt — February 27, 2009 @ 5:59 pm
Adding it up, I have a 65 percent chance of 3 inches or less ... so, at least for now, I'm on the same page with you, Other John. But I'm still leery of this being an "all or nothing" kinda storm where there's 6 inches one place and no significant accumulation 50 miles away ... a la Jan. 25 2000, when Lynchburg got 8 inches and Roanoke/Blacksburg got zippo ... that was a different air mass, lots of cold/dry air that cut the moisture off, but you get the picture ...
Comment by kevinmyatt — February 27, 2009 @ 6:08 pm
IWBIWISI. My prediction: less than one inch at RRA. And so much for Day One of our 4-day precip event. 0.09 inches at RRA. What a joke. I print out TWC's Hourly Forecast nearly every day that I work for my fellow carriers. Today's WRONG forecast by them showed less than a 30% POP for the morning hours (less than 15% for 10AM and 11AM), then shooting up to 80% at noon and staying there for the afternoon. So what happened?? It rained lightly between 10:10 and noon, and then was dry for the entire afternoon!! But I do not mind it as far as my job is concerned when decent rains are predicted and never materialize. When the opposite happens I get very ticked off!! Almost go pos--l !!!
Comment by Doug Griggs — February 27, 2009 @ 6:21 pm
This is a strange one alright..........to have a closed circulation low coming out of Nebraska. But I'll not get too excited and just predict 2 inches on Sunday in Wytheville at my house, 2400' elevation. Should be a good snowman snow however.
Rick
Comment by Rick Post — February 27, 2009 @ 7:28 pm
I think probably 5 to 8 inches in Wytheville and farther south, and about 4.5 inches for Roanoke and farther east.
Comment by AnitaJ — February 27, 2009 @ 7:30 pm
I'm quite familiar with those scenarios. They happened quite a bit down in Hampton Roads with nor'easters with a very sharp dividing line between both little/no snow areas and the major snow areas, and the major snow areas with rain only areas. I guess we'll have a better idea by tomorrow evening of what may happen.
Comment by Other John — February 27, 2009 @ 7:44 pm
The NWS forecasts keep bouncing around too. They've flip-flopped between rain and ran/snow for tomorrow afternoon and evening, along with tomorrow night and into Sunday. It looks like they think the bulk of the precip will be rain, and by the time the cold air moves in the precip will be on the way out. They dropped the precip chances to 30% for Sunday, with total accumulations of less than an inch. From what I can see, they seem to be forecasting more snow for the Outer Banks and Wilmington, NC than for here at this point.
Comment by Other John — February 27, 2009 @ 8:48 pm
Very interesting to me the discrepancy between the NWS forecasts and the HPC forecasts ... both under the NOAA umbrella, one centralized out of DC focusing on precipitation, other at various local offices focused on general forecasts ... of course HPC's discussions right now still mention that there are wide array of solutions and they're basically just averaging the extremes until there is better model agreement ... then again, some of the NWS forecast discussions are saying something similar.
The 0Z models (based on early Thursday evening data ... 0 Greenwich Mean Time, hence the name) will be starting to come in soon ... the closer we get to the event, the more real data on these atmospheric features will be fed into the computers, and the less missing data will be papered over by silicon hallucinations ... hopefully they'll show some kind of trend so we can at least tell how vigilant we need to be about this the next day or two.
Comment by kevinmyatt — February 27, 2009 @ 9:02 pm
Just took in the 0Z North American Model ... wow it's weird ... it's back to the Savannah-Myrtle Beach-Jacksonville(!) snowstorm idea on the big low, but actually makes a bigger deal out of the 1st wave for us on Sunday morning ... we could get a few inches of snow then if it's right. (I don't think it will be)
Almost but not quite aligns some northern stream energy with the strong southern low ... if that happened, it would pull it more northward ... almost happens.
I only pay close attention to models run by run on 2 occasions: (1) winter storm threats and (2) storm chasing. Equally frustrating, each time.
Comment by kevinmyatt — February 27, 2009 @ 9:37 pm
If my old hometown (Jax. Fl.) gets more snow that we do I'm moving!
M\
Comment by Angela — February 27, 2009 @ 10:02 pm
A closer examination showed that the model was showing more cold rain than snow down toward south Georgia and north Florida ... the upper levels are right, but not enough cold air at the surface ... still, if the NAM is right, the second storm would be mostly a miss to the east for us.
Comment by kevinmyatt — February 27, 2009 @ 10:39 pm
I just don't know what to make of this, I think I'm giving up on attempting to understand what may happen and just sit back and watch my weather rock...I know it will be right, 100% of the time.
Comment by Other John — February 27, 2009 @ 10:56 pm
The latest run of the Global Forecast System model -- the major American model -- is a significant to major snowstorm for almost all of Virgina, except maybe the far southwest tip. It turns the whole storm up the East Coast.
It's one run of one model, but we're getting closer to go time. Snow lovers live to play another day.
I'm ready to start seeing some of this developing in real time rather than on a computer screen. Very interesting weekend ahead. It could be a season-maker or a heartbreaker for all you jilted Roanoke Valley/Southwest Virginia snow lovers.
Comment by kevinmyatt — February 27, 2009 @ 11:01 pm
GFS: Gone Fully Senile.
I'll believe it when I see it. I think a lot of us feel that way.
Comment by Brandon R. — February 27, 2009 @ 11:07 pm
The significant thing isn't really the precise details of what the GFS is showing, or any of the models, it's some of the trends ... the GFS phases northern stream and southern stream energy together to pull the storm up the coast rather than letting it drift out to sea ... the NAM almost did the same thing ... today's European model run partially did it, and the GFS has moved closer to that solution rather than the other way around.
This could all be gone with the next silicon daydream in 12 hours ... and I'm very much in the IBIWISI crowd ... but the pieces are on the table for something memorable and historic for SOMEONE or many someones in the Eastern US ... how that plays out and where we fit into that, that's the fun of what we get to sort out in the next 24-36 hours.
Comment by kevinmyatt — February 27, 2009 @ 11:16 pm
I've seen miraculous things happen in baseball when it's the bottom of the 9th...
Comment by Brandon R. — February 27, 2009 @ 11:28 pm
The bases are loaded with two outs, and the strong-armed pinch hitter is headed to the plate ...
Comment by kevinmyatt — February 27, 2009 @ 11:46 pm
Clearly this storm does have potential .... it is fairly big, and is not coming in from Ohio and West Virginia, where Roanoke's offensive line nearly always does a super job of "blocking." If the low gets into position at or near ("near" in this context being inland a few miles, not out to sea) the NC coast, SW Virginia could get a real snowstorm. And temps will be much cooler on Saturday, than today or even this Friday evening. And the ground will have more moisture because of Saturday's rains.
Comment by Doug Griggs — February 27, 2009 @ 11:48 pm