Tuesday, January 3, 2017

"10 Things You Should Know" with snow in the forecast

Several thoughts as another "2016-'17 Winter Season" #ArcticFront comes barreling our way.

1. Fortunately, severe weather didn't materialize in our area on Monday. Plenty of thunder (even thunderfog, which is almost as cool as thundersnow), but no high wind or hail. I'm good with that. I root for people, not storms, despite trying to produce a good forecast that sometimes includes them. Folks near the Gulf Coast weren't so lucky, including Gulf Shores.

2. At the end of the day, as the back edge of the afternoon rain shield moved across the metro, the setting sun produced some spectacular skyscapes. Some folks were treated to brilliant double rainbows, others to an awe-inspiring orange sky. Scroll through our Twitter feed for a bunch of cool photos you nice folks sent, like the one below!
3. Looking ahead, the Arctic front arrives early this evening. You'll notice the wind shift to the north and pick up pretty good if you're out. If you're out later, you'll notice it'll be a lot cooler than it's been in a few days. By morning, we'll be in the mid 30s with wind chills in the 20s. Bundle the kids up as they head to school! We could see a few stray showers with the frontal passage late this afternoon into early evening. They'll be relatively minor compared to rains of the recent past!

4. Very cold air hangs around for several days as the high pressure of Arctic origin makes its way across the northern U.S. We'll be on the south side of it, but it'll still be plenty cold. Expect lows in the 20s and highs in the 30s starting Thursday morning and continuing into early next week!

Low temperatures Sunday morning according to this morning's GFS computer model. Yes, the freezing line is as far south as central Florida with below freezing temperatures across the vast majority of the CONUS. (WxBell)

5. The million dollar question, and one that everyone wants to know the answer to, is will it snow and if so when and how much?? The latter part of that question seems to have taken on a life of its own given recent rumblings of "snowmaggedon-like" snow totals in the south from some folks who would rather share model hype rather than be responsible.

5a. BTW - we don't recommend getting your weather information from sports talk figures (I'm looking at you Clay Travis), just like you don't want my analysis of Grizzlies trade rumors. Neither of us knows what we're talking about. Stick to the experts who have skin in the game and have proven responsible in the past, and aren't out just for ratings or social media numbers!

6. The REAL answer is: I'm not exactly sure yet.  "But Erik, that's not the answer I wanted to hear!" I know, but it's the responsible answer at this point in time. I DO think there's a decent chance most of us could see some snowflakes. But I don't know exactly when and I don't know how much. YET. Maybe you've heard about how hard it is to forecast winter weather in the south (in particular)? Below are a couple of visuals to help you understand. Then I'll give you my first educated guess, since you asked...

7. First are the snowfall maps (all valid through 6pm Saturday) from the last 12 runs (4 per day) of the American-made Global Forecast System (GFS) model. Greys are light snow, blues are snowman builders, pinks are snowmaggedon. Notice how the snow starts to our north, drops the hammer right over us, then backs off again and sinks south.The last frame is from this morning's model run.

We also have this graphic which shows run-to-run consistency (or not) for the GFS model. Each row represents a run of the model. Exactly three of the last 15 models runs (or roughly four days worth) has produced more than 2" of snow.

8. But that's the American model... the Europeans are far superior, right??  I give you the European model (credit Weather Bell Analytics), same parameter, run twice a day. This is from model runs of the past 6 days:

Oh yeah...FAR superior! Haha! I will give it this though - the past couple of days it has been somewhat consistent. But it still varies from a dusting to about 2" here in the metro over that time as you can tell from the graphic below. Again, multiple (the last 11 to be exact) runs of the European model. Only one has forecast more than 2".

9. All that said, here's my best guess at the possibilities, with all the caveats applied and with medium-low confidence. Thursday night has a chance for some flurries or maybe a dusting (meaning less than 1/4"). I don't think it's the time period of greatest concern, as far as traffic problems, etc. During the day Friday, there's a better chance we could see some minor accumulation - I'm talking about maybe an inch on average. It'll be very cold and cloudy so it wouldn't go anywhere right away. An inch could be enough to possibly cause some slippery roads, especially those elevated ones we keep building, but it's not enough to even cover the grass. If I end up conservative, we could get 2 inches - but that's my upper bound right now. Flurries could linger Friday night into early Saturday, but that's also a low probability.

10. Should you get all worked up or start changing plans? No. Will schools be closed?? I have no idea. Just stay tuned. Listen to trusted sources who have proven their mettle in the past. We'll keep you sane and provide the "real deal," not the wish-cast. As the event gets closer, especially tomorrow into Thursday, we'll get more model data that is higher resolution within the forecast window of concern and things will hopefully start to become a little clearer. But remember, it's the south. It's snow. Those things don't mix, and that applies as much to forecasting it as it does to driving in it! Keep an eye on our social media feeds listed below for the latest. And if all else fails, "if it looks too good to be true, it probably is!" Don't share it.

Erik Proseus
MWN Meteorologist

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