The temperatures Monday night and Tuesday will likely be in the teens and lower twenties. This puts snowfall ratios around 2o:1 (20 to 1 = 20 inches of snow from one inch of rain) or higher instead of the typical 10:1 ratio when temperatures are right around freezing. So let’s take a look at how Washington could be digging out from a plowable snow on Tuesday with widespread closings:
Here is the latest Short Range Ensemble Model showing how much liquid may fall… with .02 being the bare minimum and 1.39″ being the maximum. Okay, so the average of the members is just over a half an inch of liquid (.68″).
Notice at National Airport (Inside the Capital Beltway in the proverbial Snow Hole) the average liquid forecast is slightly over a half an inch of liquid. Okay let’s do some math using a 20:1 ratio. (20 multiplied by .6″ = 12″ of snow).
Finally, here are the latest forecast models showing 10:1 ratios (the ratios will be closer to 20:1 or higher meaning a lot more snow could fall than what these ar showing):
Winter Storm Watches will likely be issued for the Washington Area some time today (probably this afternoon/evening).
I would like to also point out that if the forecast models are correct and the trends continue, there will be snowpack on the ground which could deliver even colder actual air temperatures than we have seen in decades around here.
When Tuesday’s storm departs, high pressure will eventually move overhead setting up radiation-cooling (clear skies, calm winds at night). Add snowpack to clear skies and calm winds at night and temperatures have a tendency to plunge well below zero.
Parts of the Washington Area could be looking at actual air temperatures dropping into the single digits and teens below zero during the middle portion of this week. If it doesn’t happen you can blame me, that’s fine, but I like to discuss real possibilities to keep people prepared. I don’t see temperatures rising above freezing for the remainder of the work week possibly extending through next weekend with record shattering cold on the horizon. Wind chills and actual air temperatures are two separate things. It would be amazing to have actual air temperatures well below zero in the DC Area. Winter is coming late this year… it’s looking stormy again next weekend!