Which version of snowfall totals do you prefer–the NAM on the right, or the GFS, shown below? (Click images to enlarge.)

If you live out east, the question is purely academic. I doubt that you much care which forecast model is the more accurate, because either way, you’re going to be sitting under a ton of snow by tomorrow. That much is no secret. While the forecast models shown here are for 00Z Saturday night, the show has already started.

Farther down the page, you can see a level 2 radar grab from Sterling, VA, taken shortly after 10 p.m. It’s much prettier to look at than the picture that is unfolding over the nation’s capitol as I write in the form of heavy snow, freezing fog, mist, freezing rain, blustery winds, blizzard conditions–just about every kind of winter weather you can throw at one area in the space of a few miles as temperatures drift from below to above freezing.

The current Baltimore forecast for tonight and tomorrow reads as follows:

Tonight: Snow and areas of blowing snow. The snow could be heavy at times. Low around 29. Breezy, with a east wind between 16 and 23 mph, with gusts as high as 37 mph. Chance of precipitation is 100%. Total nighttime snow accumulation of 15 to 21 inches possible.

Saturday: Snow and areas of blowing snow. High near 29. Blustery, with a north wind between 18 and 22 mph, with gusts as high as 37 mph. Chance of precipitation is 100%. New snow accumulation of 4 to 8 inches possible.

Ugh! For once I’ll take a Michigan winter forecast over what’s being served up elsewhere. Right now my friend Kathy out there in Greenbelt, MD, is getting her clock cleaned. It’s a good night for her and her boyfriend to eschew the Washington nightlife and hunker down inside. For that matter, I doubt there’s much happening in the way of a Washington nightlife on a night like tonight.

Meanwhile, down in the warm sector, much of eastern North Carolina is under a tornado watch. The radar shows a pretty grungy-looking, non-severe, low-topped squall line that doesn’t show much likelihood of putting out anything tornadic, but it nevertheless adds to the East Coast’s overall weather ambience.

Have fun out there, kiddies, those of you who live out east. As for me, I’m going to pour me a mugful of Bell’s Amber Ale and, for once, enjoy watching the snow not fall outside my window. Gloating over such things is permissible for lifelong natives of the Great Lakes.

Yesterday’s trough passed through pretty much as expected, without a whole lot of fanfare and certainly not with anything tornadic. So the question is, what lies ahead? Anything?

Maybe.

At least we’re not locking in under another ridge. Today is the first day of autumn, the weather patterns are changing, and the GFS and ECMWF seem to agree on a 500 mb trough affecting the Midwest over the next several days. And yeah, yeah, I know it’s just reading tea leaves, but here are a couple 132-hour GFS maps for next Sunday at 00Z. At the risk of stating the obvious, click on the images to enlarge them. The first shows sea level pressure (shaded), surface wind barbs, and 500 mb height contours.

The second map shows 500 mb winds (shaded) with wind barbs, and 300 mb wind contours.

The big question mark may be moisture. But this far out, it’ll be nice if that even matters by the time Sunday arrives. This time of year, living in the Great Lakes, the best one can do is hope. But there’s nothing wrong with hoping.

Earlier today, I opened up GR3 just out of curiosity and noticed some blobs of convection along the Lake Michigan shore by Chicago. Here are a couple radar grabs.

These images interest me for several reasons, all of which have to do with a Great Lakes phenomenon called the lake breeze zone. The lake breeze zone is not a fixed area. Its boundaries are atmospheric, not geographic.

And boundaries truly are what it’s all about. Probably the most immediately noticeable feature on these radar images, besides the obvious storms, is the north-south boundary set up by the onshore breeze. It’s a great point of convergence where overall westerly surface winds butt up against backing winds from off the big lake. You can see how outflow from the storms that have fired up within the lake breeze zone interacts with the lake breeze boundary.

Another less immediately obvious by-product of the lake breeze zone is helicity. Notice how the wind barbs farther inland are all westerly, but inside the lake breeze zone, they’re easterly. Now, I’m no expert on this stuff, but I know enough to recognize the potential for localized helicity to occur even when the large-scale flow is unidirectional. During the day, strong thunderstorms can go tornadic when they encounter a backing onshore breeze near Chicago, along the Wisconsin shoreline, and along the Lake Huron and Lake Erie shores of eastern Michigan. The same can happen in the evening along Michigan’s western coast as the land cools and an offshore breeze prevails. Many times I’ve noticed the NAM and RUC showing a small sigtor centerered over Berrien County when there are no sigtors anywhere else in the region, and I’m sure this phenomenon is largely due to the lake breeze in that area.

Right now I see storms firing up farther north around Gladwin and Roscommon.

A glance at the Gaylord VWP shows west winds neatly stacked from the surface on up. But look at the METARs along Lake Huron. Without much in the way of bulk shear, the storms are subsevere, just little popcorn cells. But it will nevertheless be interesting to see what comes of them as they work their way into those backed shoreline winds. You just never know.

Bill called to say that he and the crew just saw a wedge out there in western Oklahoma. The LSR gives the town of Crawford, near the Texas panhandle border, as the location.

Good for the lads–and the lass, as I understand there’s a new female member of the crew. As for me, sitting here in my La-Z-Boy sofa, nursing a chest cold and watching the radar, naturally I feel like shooting myself through the head. A wedge on a PDS day–and the show is just getting started. And I’m not there! AAAAAHHHHHH!!!!!!!

If there’s any consolation, it’s knowing that I’ve been able to make myself useful doing a little nowcasting. And it sounds like the team got some cool footage. Can’t wait to see it.

Mostly, though, I can’t wait to kick whatever is causing this blasted chest congestion and get out to take some video of my own. Tornado season 2009 is underway!

Shifting gears, last night’s gig at One Trick Pony with Francesca and Friends was a blast, even if I was feeling under the weather. Wright McCargar and I had a discussion about the impact of musicians on each other’s playing. In my experience, one bad musician can drag a whole group of good musicians down; and, conversely, one great musician can kick good players up to the next level. There’s nothing like being with really good musicians, and Francesca and her rhythm section are exactly that.

Moving back to storm chasing, it’s time for me to publish this post and then check out the radar. The storms bumping off of the dryline look to be going tornadic, and I’m thinkin’ that my buddies will have their hands full for the next five or six hours. Sure wish I was with them. But GR2AE ought to keep me entertained; maybe I can capture a few radar grabs to correspond with the photos that I’m sure will be coming back from out west.