Weekend Storm Taking Shape

A large winter storm continues to take shape seemingly a world away, off the coast of the Pacific Northwest.  But there is little doubt that it will be a major storm for someone in the Upper Midwest.  But the largest question remains, what will the final storm track be?  Why is this a big deal?  The track of this storm is a little more critical than other storms of its nature because it will be bringing a lot of moisture and relatively warm air along with it.  This brings into question precipitation type, AKA rain versus snow.  This would have a huge impact on areas this storm would affect and right now there are still half a dozen solutions that we could wind up with.  All of these would give many areas a much different picture than our current forecast.

So here are those potential storm tracks.  It doesn’t look like they are all that far apart, and in the grand scheme of things, they aren’t.  But when temperatures are expected to be awfully close to freezing, 50 miles can make a world of difference.  For example, 50 miles in a storm like this could mean the difference between an inch of rain versus a foot of snow.  Now at this point, if this storm takes a more northerly track, warmer air would move further north and give the majority of our area rainfall instead of snow.  But if it takes a southerly track, the majority of us would get snow, which could be heavy in many areas.  You see why this is so critical now?? But as it stands, the highest probability solution would likely take the storm path somewhere between the red and dark blue line.  This would give at least a little snow to most of the area, but the heaviest by far would stay across the north and west. 

So here is the current thinking.  With a middle of the road solution, the following image would be the likely outcome.

The majority of the far north and many areas west of the James River would be all snow.  With the exception of the first few hours, snowfall will be the predominant precipitation type with heavy snow possible the first half of Sunday.  The green shaded areas in the southeast would likely be all rain with very little if any snow accumulation, even when colder air moves in.  Although rain may mix with snow at times, snow accumulation would be very minimal.  Now the pink shaded areas are the biggest question because a degree or two one way or another could drastically change the outcome in many of these areas.  Right now, the further north and west in that pink area that you are located, the greater your chances for significant accumulating snow (6 or more inches).  This area may also see the change over from rain to snow and vise versa occur several times during the event making for a very wet and slushy accumulation.  Because of this, amounts in these areas could drastically change.  The following 2 images show the potential snowfall totals from the 2 most northern storm tracks you see in the picture above.

The first one lays the snowfall across our far west and north with heavy snow from Winner to Pierre to Aberdeen.  The second image, much like its track, is further south and east bringing the heaviest snow to Winner, Chamberlain, Aberdeen, and Watertown.  If this low ends up taking the furthest track south (the least likely scenario, but still a possibility), then picture this same band of heavy snow another hundred miles further southeast putting the heaviest snow in Yankton, Mitchell, Sioux Falls, Brookings, Watertown and Marshall.

Now, The National Weather Service agrees with a middle of the road storm track and have issued the following forecast for snowfall you see below.

Clearly this isn’t your first rodeo so you know that your backyard totals will vary, not to mention that this forecast is far from concrete and may shift one direction or another in the upcoming couple of days.  But it does give you a general idea of how much snow somebody could get.

Here’s another way to look at.  Below are the probability forecasts produced by the Hydrometeorological Predction Center.  The first image shows the probability of getting at least 4 inches of snow from Friday night through Sunday night.

The HPC agrees that the best chances for significantly accumulating snow will be across the north and west with a 60 to 80 percent chance of receiving at least 4 inches of snow from Winner to Huron to Aberdeen and Watertown.  Only about a 10 percent shot in Sioux Falls.


Just for kicks, here is a look at the probability of receiving at least 2 feet of snow for the same time period. 

Obviously our chance is zero, but check out the northeast.  Boston has at least a 50 percent chance of more than 2 feet of snow.

Just because the southeast isn’t getting the beneficial snowfall, does not mean no precipitation will fall at all.  In fact, heavy rain is possible in areas of the southeast.  Check out the liquid forecasted totals for the Upper Midwest through Monday morning.

Now, this moisture will fall as snow in the north and west, but its mostly rain in the southeast leading to widespread amounts of a half inch to an inch of rain at least according to the Hydrometeorological Prediction Center.