Thursday, January 22, 2015

9:50pm update on snow potential for Friday - as challenging as it gets

Will keep this brief, as it's getting late, but after earlier today backing off the potential for snow during the day on Friday and calling for just a chance of a rain/snow mix as precip ends Friday evening, models (and the atmosphere) are again leaning a bit more towards a potentially cooler solution for the early morning hours Friday.

Any snow that can mix in will likely be caused by an atmospheric process called "dynamic cooling," which is too complicated to explain here but is basically a lowering of air pressure due to rising motion. The lower pressure causes temps (above the surface) to cool. Even 1-2 degrees could be enough to mix snow with rain in the early to mid-morning hours, even though we'll be in the mid 30s at the surface. The challenge is that this process is very difficult to forecast until it occurs.  We can see that the potential is there, but we don't know if it will be enough to push us over the edge for snow.  What we do know is that 1000' up, precipitation will be mostly snow! Whether it melts prior to reaching the surface is the big question.

We also know this - even if some snow mixes with rain during rush hour through mid-morning, the ground and air temperatures will be ABOVE freezing. Any accumulation (should there be enough snow to cause it) would be on grassy surfaces or bare ground and would be minimal and quickly washed off by rain. Roads are expected to be wet, not icy.

We'll see what we wake up to. In the meantime, plan on schools being in session, roads being wet, and temperatures being cold! Get the latest official MWN forecast on our website or apps, linked below.

Erik Proseus
MWN Meteorologist

Follow MWN on Facebook, Twitter, and Google+
Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

No comments: