Monday, February 13, 8PM
All evening model runs like the idea of rain changing to snow before sunrise tomorrow morning, and possibly becoming very heavy across areas north of about the Inter County Connector in Montgomery county. Some of the totals being spit out by the mesoscale models are ridiculous as they are programmed to do a 10 to 1 ratio and that isn’t likely as temperatures are going to be very marginal. I would ignore any computer generated snowfall maps from the models like the NAM, RAP, and HRRR, but regardless of how much snow actually accumulates, the bigger issue would be the snow intensity rates that these models are suggesting. This is a very dynamic system and some areas may see incredible snowfall rates and even thunder-snow that would make for hazardous driving conditions. Winter Weather Advisories are out for northwestern Montgomery, all of Howard, and all counties bordering the PA line for Tuesday morning.
I am not very confident but my thinking is that rain will change to snow from northwest to southeast from 5-8AM and be moderate to heavy. Keep in mind that because of the rain, roads can not be brined so conditions have the potential to deteriorate very quickly. Even if air temperatures are above freezing, if there is heavy snow falling, surface temperatures will cool quickly and slush would accumulate. As far as snow accumulations, I think the elevated areas of Carroll and northern areas along the PA border have the best chance of 3 or more inches with a sloppy 1-2” across the rest of the areas in the advisories. Conditions look to be vastly improved by about noon tomorrow.
Again, I am not very confident and can see this being pretty lame, but it is difficult to ignore the consensus from all the models. I’ll update with a brief post later this evening after the 0z NAM nest runs.
The Weather Mill 