Model Mania (Snow?)January 27th, 2010 at 10:19 am by Jeremy Wheeler under Weather
Ok I promised a new blog so here it is. I thought about waiting for the morning models to come in, but I didn’t want to wait that long. There’s my latest snow hope index. It’s at a 7. Odds are that this will go down tomorrow, and then back up on Friday, but we’ll see. Here’s the latest thinking about this system:
The Basic: An area of low pressure will move up from the Deep South Friday into Saturday. It will butt-up against some very cold air coming out of Canada on Friday. Snow showers in Central Virginia are a good bet. There is a chance for accumulating snow in the metro (hence the snow hope), but there is also a possible rain/snow mix in the forecast for a period. Scattered snow showers are expected late Friday night while the whole atmosphere moistens up from top to bottom. Then the mix would come in to some part of the viewing area early Saturday. As the low moves offshore Saturday, the cold air will push back south and snow showers will take over. Then the upper level low comes into play and can make for some light snow showers Saturay afternoon/evening. Here’s the latest forecast that I put together regarding the low pressure area at the surface:
The models (detailed): I first looked at the Canadian model. It has some light snow arriving late Friday night through a good portion of the area. Very light stuff though. Then Saturday morning it shows heavy snow near the Virginia/North Carolina Border. It looks like a mix from Virginia Beach Southward. Saturday afternoon/evening the low moves offshore and we get some moderate snow inland with a possible rain/snow mix in the metro. Rain/sleet for the Outer Banks at that time. We dry out later that night.
The overnight run of the GFS model has some rain/sleet/snow in North Carolina Friday night with virga over Virginia. It has the light snow coming in overnight with a rain/snow mix over northeast North Carolina. Light snow in the metro and heavy snow in Central Virginia. At that time the low is over South Alabama and stretches over to South Carolina. By Saturday morning it looks like a mix in the metro southward with heavy snow from about Suffolk northward. It would probably be the heavy/wet variety, but that’s a guess. By the afternoon the GFS has some moderate to heavy snow in the metro and north and west of here. The low then stretches from Florida up to just offshore of the Outer Banks. The upper level low then takes the baton and produces some light snow Saturday afternoon/evening as the surface low moves away. Here’ s the place that I go to look at the GFS and NAM models. It’s NCEP.
To me the European model looks further south and is more upper level dependent. It looks like less snow from the most recent model run, but maybe I’m not looking at a good source. Here’s the link that I use: European.
(update) I just checked the morning run of the Navy model. It is the driest of the models with most of the mixed precip across North Carolina. It is not very impressive, but it still advertises some light snow overall.
The morning run of the NAM is coming in now. Whoa! It shows dry conditions Friday night and overnight, but then it gets interesting. Saturday morning it has heavy snow over North Carolina with light snow in the metro. The surface low over South Georgia at that time. By Saturday afternoon we could see a rain/snow mix in the metro and in northeast North Carolina. But it suggests heavy snow from the metro northward and in central Virginia. The low stretching from Georgia to the southern Outer Banks at that time. By the evening everybody would see moderate to heavy snow showers as the low moves offshore. This looks a little supicious though as most of the moisture would come on the backside of the low at that point. It’s not out of the question, but it does look overdone. The upper level low would be coming into play at that time. We’d get the 500mb PVA (upper level spin) coming into play then too. If this model verifies, then we will be in trouble as we’ll have to measure the snow with a yard stick.
My 2 cents: So here’s my latest thinking based off of what I’ve seen so far. We’ll probably start off with some light snow showers very late Friday/early Saturday. This will turn into a mix in part of the metro Saturday morning as the low gets closer. Then as the low moves away the winds go more northeast and the cold air pushes down. Then we have a chance for snow showers even in the metro. The upper level low may produce a few light snow showers Saturday afternoon/evening, but it will be on the light side. This is also when snow may push as far south as the Albemarle. Some things that could impede snow in the area… If the low strengthens before it moves offshore, then it could throw some more warm air up this way. That could push the rain/snow line a little further north. It’s also possible that the low could move further south and then offshore. That could reduce the snow amounts significantly as most of the moisture would be further south. But it would also mean that the cold air is in place and then anything that fell would be snow. Things are getting interesting, but I am not going to get too excited yet. It’s still early. I’ll start talking about possible amounts tomorrow. Then it will be 2 days out. If there is any big updates on the morning run of the GFS, then I may update this around midday.
Meteorologist: Jeremy Wheeler