Final Call Forecast – March 13-14 Winter Storm

This has been an extremely challenging forecast. We’ve had little consensus between the models that gave any confidence on what was going to happen, until last night. Now, all the short range, high resolution guidance has converged. The guidance pushes a significant period of sleet and freezing rain in the I-95 corridor because they track the low just off the coast. I have a slight concern regarding freezing rain, which I discuss below.

Edit: Winter Storm Warnings and Winter Weather Advisories are in effect, see map for locations

Snow moves in between 6 and 9PM this evening. The initial precip will be responsible for cooling the surface numbers down – which will happen quickly. There may be a brief period of rain as the precip moves in, but it would quickly change to snow. Between 11PM and 1AM, the sleet pushes NW into the I-95 corridor where it sits until 7AM. Areas just east of I-95 could see some freezing rain too, I’ll explain below. Afterwards, colder air wraps around the storm as it pulls away and pushes snow eastward – and some of that could still be heavy enough for a few inches Tuesday morning. Snow exits after noon, with snow showers linger through the day.

First, I’ve cut snow totals in the I-95 corridor and east. N&W, I’ve generally left the numbers alone. You will get crushed with this storm. Most of the 1″-3″ band occurs Tuesday morning after the return to snow. Any snow that occurs before the changeover will likely be washed away.

And there is the precipitation type you can expect:

And here’s Futurecast, from one computer model, which is pretty close to what I think will happen. Note: I’ve added in the precip type around the cyan colored dashed lines. The color of the radar itself may not accurately represent the precip type falling (it’s only an algorithm, and its not perfect)

Schools: 

Montgomery, Howard, Baltimore, Harford, Cecil & all counties west: Likely closed Tuesday

Charles, PG, Anne Arundel County: good chance closed or delayed, but possibly on-time

St. Marys, Calvert: possibly delayed, but most likely operating on-time

 

Discussion:

First thing I want to address is the potential for freezing rain, because it’s not something that has been mentioned by anyone, including myself. Here’s why I’m watching it closely.

I raise this concern because several of the short range models show the freezing rain potential. I think they’re being too aggressive, but it raises a concern.

Take a look at the map below, the area that I highlighted is an area that I expect will be at or below freezing the entire event (once the temps fall Tue evening). The models raise the surface temps in this area above freezing as the low passes, which causes the model to see the precip as either sleet or plain rain (depending on the atmosphere above the surface). However, this is an area that is usually notoriously stubborn to warm up, when warm air tries to overtake cold air. This isn’t guaranteed though, as each situation is different, and temps could rise to 33/34 and it’s just rain – but it’s worth watching closely. It’s one of those things you pick up after forecasting in an area for several years. The dynamics with this system could also help keep the temperature profiles in the atmosphere slightly cooler than the models show, which results in partial melting (sleet), as opposed to full melting (rain).

Getting ice to form is a complex process, and not all the liquid would turn into ice (assuming there is any) – which is a good thing, because probably an inch of liquid or more will fall over the area during the overnight hours. Some light icing is possible in the areas I mentioned.

In terms of sleet, there will probably be enough of it we’ll see accumulation of sleet, and in some spots it could be an inch or two.

Between Midnight and 6AM, the best dynamics with the storm will be over us. Expect heavy precipitation, whether it be snow, sleet or rain. If you’re a light sleeper and live in the I-95 corridor, you could very well be woken up by sleet. Thundersnow is also possible during this time frame.

 

I’ll be posting updates as necessary overnight and through the storm on the Facebook page. Any questions, please ask!

-Andrew

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