The European forecast model that came out was the last piece of information that I was waiting for. Sorry for not posting my updates earlier, I was sitting in rush hour. Models now agree on track (they moved slightly north today) with some slight differences in timing, speed and temperature profile. What the models do agree on is that a period of very heavy snow will fall Thursday morning between 4AM and 7AM across the immediate Washington Metro Area.
Timing (from the latest High-Resolution-Rapid-Refresh models):
HRRR for Snowfall Accumulation:
North American Model:
- Road crews, please be aware that snow squalls are likely tomorrow across the region. With temperatures plummeting into the 20s, any snow squalls could put down a quick dusting to one inch in a short amount of time. Your services will be needed even after the heavy wet snow tapers off from west to east between 6 and 9AM.
Finally check out the temperature plunge:
5pm — the mild conditions right now will be a distant memory tomorrow.
Temperatures by 7AM (notice the northern and western suburbs at or below freezing) – there will be slick travel on untreated roadways and the heavy rain that will fall prior to the snow will wash away much of the pre-treatment.
DC Storms 
The light blue and grey zone on my map could certainly perform to the upside… I could see a quick 2″ coming down in one hour between 5AM and 7AM in the metro… but mainly on grassy surfaces. You’re right that this is an extremely dynamic system!
I know these type of events are very difficult to forecast, but what the models are hinting at is a possible instability event with rapid cooling aloft (causing thundersnow), where a signficant amount of snow comes down in a short amount of time.
I believe the best example of that was in March 1984, where in the northern suburbs there were 4″ of snow in 45 minutes with high winds and continous lightning and thunder. Whiteout conditions and truly spectacular!
I know hoping for that is like hoping for a Patriots win halfway through the 3rd quarter, but I guess stranger things have happened!