Yes, Maryland, there is snow coming .... I will have a more complete and detailed report late tonight, but for now, here is how things are shaping up.
The future storm is now on land in the west, so we will now be able to collect more and accurate data to feed into the computers. Throughout today we should see the computer models begin to synthesize the outputs more consistently. But, thus far there is consensus in the models that we will have snow this week. The question mark which remains is the accumulation.
Why is accumulation a question mark? This time of the year (as I detailed in my previous post) it is more difficult to have snow stick. Snow will only accumulate this week IF it falls at a very heavy rate. If that happens, the moisture will cool the atmosphere near the surface, and the snow will build upon itself on the ground faster than the ground can melt it. When that happens, the top snow layer stays cold since the surface atmosphere has now cooled, and the lower layers of snow stay frozen because the top layer is insulating the bottom. But this can only happen if the snow falls at a heavy pace.
Another question mark is if there will be any mixing of rain. If rain mixes in that will reduce accumulation. Given the projected temps, we are most likely looking at wet and heavy snow. Not only is that snow dangerous to power lines, it is more difficult to estimate how much will accumulate. Wet heavy snow compacts when it hits the ground, with the weight of the top layer forcing itself closer to the ground.
Snow accumulation is calculated from the surface temp computed with the amount of precip. The models predict the amount of precip but not how much snow. Given all that I said above, we can't just use the mathematical model. For instance, generally 0.1" of precip equals 10" of snow. But given what I said above, that same 0.1" might only accumulate to 4-5". The conditions make it difficult to forecast amounts.
TIMING: It appears the timing is now late Tuesday into early Thursday.
ACCUMULATION: Didn't I say enough on this above? hehe ... This is NOT my forecast, but data is showing central MD could see 4-6+ with S MD maybe a bit more. But again, this is based on pure data, NOT yet my forecast.
I will have a detailed update late today. Follow me daily on Twitter (@wxmanmd) for weather updates and tidbits.