An outstanding post. The info on likelihood and timing is very helpful. Hopefully, the severe weather aspect of this does not come to pass -- can't understand why people root for thunderstorms :(

please can an expert explain where/how a possible tornado figures into this mix?

Winds are going to be changing with height a bit as you go up through the atmosphere (southerly at the surface, more southwesterly about 30,000 feet up). This creates some rotation which could allow a few tornadoes to form, especially in SE VA. The risk here is not non-existent, but low.

Will this affect air travel? I'm flying out of BWI tomorrow morning (9:00 am)... Thanks!

boooo 12z

I'm not a meteorologist, but it's a tough call at that particular hour. Tomorrow's 7am forecast sounding for Dulles shows veering winds (S through SW to W) in about the first mile of the atmosphere, but winds at all levels are almost uniformly from the west by 1pm.

That tells me that the surface front will be passing sometime in that period, which unfortunately is when your flight is scheduled.

I wouldn't doubt that there will be significant delays tomorrow morning along the east coast, however.

Thanks for the tutorial! I love educational content.

Really like the "when will it occur" part. Very helpful as I have early afternoon plans that I was considering cancelling, but think I will go through with them now.

Also, a colorful visual of the bigger picture:

http://www.wunderground.com/US/Region/US/2xpxWindSpeed.html

Until next winter............

Most areas will receive .50-1.50 rainfall during the next 18 hrs. The trajectory of movement favors the Shenandoah Valley and eastern slopes finally getting a decent shot of rain, probably averaging more than the D.C. area.

This is nowhere close to enough rain to create any significant flood threat, irrespective of the FFW. The soil moisture level is very low, stream flows, both large and small are very low (some at historically low levels for this date).

Urban areas could see ponding of water in low lying areas, where a localized downpour occurs, and runoff is of course enhanced by the "Blacktop Jungle" of pavement.

Late week looks interesting. All the models have converged on the idea of a storm, but track preference varies widely. Temps. will be very marginal. High Elevations and western areas seem to be most favored for frozen precip., but this evolving potential bears watching.

This is really helpful. What, where, when (awesome to know this!), and why. Keep up this kind of post, please, and thanks for being a great site!

working from home: priceless

Unemployed for the first time: Priceless!

Augusta Jim,
Yes I also see the models also tending toward a coastal storm. I don't see enough cold air here though at present. This is it as far as our "last best chance" at anything major this year. I think by this time next week we will either be saying "finally!" or else it will be Requiem for Winter. Sadly in the light of the pattern-that-never-changed this year, I predict the latter...

Augusta,

Models are still all over the place with the storm. What would have to occur for us to get snow in DC.

Henry M of accuweather is still calling for the big daddy, but he's kept drawing his little line on the mountains and west, so we're probably effed again on snow. :(

The Weather Channel is not ready to call this yet! They indicated that the models this afternoon are all over the place and it may be another day or two before they have a handle on this.

Greg,Weatehrdude,

Greg I agree. Model speculation this far out can cause headaches. Especially when they do not concur with eachother. It still too early to tell on precip. It is likely a storm is going to scoot the coast.

Henry at accuweather made it clear that he didn't know the storm track this early.

Do not rule this storm out unitl all the models begin to agree on a similar track.

Also, 3/20 is of interest now according to some mets.

3/20 is of great interest because it's the first day of SPRING!!!!

Seriously, even the biggest snow lover of them all, Topper Shutt, throws in the towel after 3/15.

Yes, it seems likely that there will be a coastal event Saturday/Sunday, but anyone who makes a quantitative forecast four days out based on models should be summarily ignored.

"can't understand why people root for thunderstorms"

some women think thunderstorms are romantic

I love t-storms because of their sheer power. It's like a free show from madre nature.

DC and the surrounding counties are under a TORNADO WATCH