Midweek mess

Every so often, we meteorologists have forecasts that make us want to pound our heads against the nearest wall. The weather for the Tuesday-Wednesday timeframe this week is one of those situations...

The piece of energy that's going to cause our wintry weather isn't yet over land, so our computer models have very little data to use to try to depict how this is going to evolve. The NAM model moves the low through much later than the GFS model... in addition, the path of the low isn't the same, either.

There's a huge amount of uncertainty in the details of this forecast. The generalities, at this point, seem to be ironed out, at least: I expect a wintry mix to develop late Tuesday, lasting into Tuesday night. It may change completely over to rain; the chance of that happening increases the farther south you go. Then on Wednesday, the mix/rain turns over to all snow, along with gusty winds.

However, how much snow any location receives is pretty much completely up in the air at this point. Model output has been seemingly random even in the two most recent model runs; I've seen model output as low as about 2" and as high as 10". Obviously, that sort of range doesn't make me overly confident in how much snow we'll get. We wouldn't be putting out any snowfall forecast maps yet, anyway, but it goes to show how this whole midweek weather situation isn't an easy one to figure out.

We'll be focusing on a few things in determining the forecast this week... in particular, the temperatures at the surface up to about a mile high in the atmosphere. We'll be close to that oh-so-wonderful freezing mark in that entire layer... and a change of a couple degrees could play a big role in who receives what type of precipitation. Also, a more northerly low track would usher in warmer air and decrease the chance of heavier snow... but a southerly track would allow cooler air to prevail, leading to greater snowfall.