October Festival Guide

Update on Snow Potential Next Week

ecmwf_apcp_f132_us

Our wild ride continues over the next 7 days with a nice stretch of warm and dry weather heading into the weekend, followed by yet another chance for snow next Tuesday.  Medium range models have been showing the potential for a nor’easter next Tuesday and Wednesday for the east coast for several days now, with the main impact for Virginia coming on Tuesday.  Stop me if you’ve heard this one before.  The snapshot below shows an impressive low bombing off the Mid-Atlantic coast Tuesday.

ecmwf_apcp_f132_us

This system, should it verify as shown above, would be different from our last two snow events.  Our last two systems had a very pronounced mid-level warm layer that resulted in sleet, freezing rain, and even a cold rain at times.  Surface temps were cold enough with the last two events for whatever to fall to cause a problem with icing.  The system next Tuesday will be colder aloft, allowing all snow as the precip type, but warmer at the surface, limiting the accumulation potential. That’s not to say we won’t see accumulating snow, because there are plenty of reasons to think that we could. There will be factors hurting us as well as helping us. 

Here’s what will hurt us:  time of day, time of year, and surface temps. The daytime arrival will allow solar radiation (yes, even with cloud cover) to keep surfaces warm.  The time of year in late March means a higher sun angle and greater incidence and period of radiation.  The surface temps will likely be very marginal for sticking snow, somewhere in the 34 to 38 degree range.  Should all this come to pass, we’d see a very pretty snow falling with big snowflakes, but the roads would stay slushy and the grassy surfaces would see an accumulation of very wet snow.

Here’s what will help us:  precip type, precip rate, and loading.  The precip type in this situation should be almost all snow.  The rate of precip will be so heavy at times, that snow could quickly accumulate even with above-freezing surface temps.  The rate of precip will result in “loading” or frictional drag, pulling colder air off the surface down to the surface and allowing surface temps to cool to freezing or below.

The Euro has done a great job nailing the pattern a week or so out, but along with most of the other models, has not done well with snowfall totals.  Here’s the latest QPF from the Euro, the most aggressive model with this system, which is within an inch of what it was showing yesterday.

state snow euro

My feeling is that we will see some wet snow that will accumulate on grassy surfaces and for a short time on the roads. I’d have to see something much more potent to call this thing “major”, and it will have to be more than a bunch of over-the-top snowfall maps that will no-doubt be shared thousands of times on the internet. That’s my realistic look at what will happen next week.  It ain’t sexy or sensationalized, and won’t garner me a boatload of facebook likes, but I call it as I see it, and hopefully folks can appreciate that.  Expect more updates on Facebook and Twitter over the coming days, for those of you that have “liked” or “followed”, as there certainly will be some changes.  For now, enjoy the fine Spring weather.  -Zach

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