The Fine Line Between a Snow Storm and Blizzard

nam_namer_054_1000_500_thick As I look at some of the latest model runs this evening, my concern is growing that this won’t be just a snow storm that impacts Iowa and the rest of the Midwest.  I fear this could turn into a serious blizzard, severely impacting travel in portions of the state if not crippling it all together. 

First of all we need to look at what exactly a blizzard is.  The National Weather Service follows a strict criteria for the weather condition.  Sustained winds or frequent wind gusts must be greater than 35mph with blowing or drifting snow that reduces visibilities to less than a quarter of a mile for three hours or more.  This is something that is a very real possibility over Iowa this week and a threat that forecasters are keeping a very close eye on.

So how does this happen.  Simply put, it’s all in the power of the low.  As the center of the storm (slated to pass southeast of Iowa) grows stronger, the pressure falls, creating a large difference between the low and ridges in the atmosphere.  This sharp contrast is represented by lines of pressure on a map, known as isobars.  The tighter these lines are together, the sharper the difference, and the stronger the winds.  If, as expected, the center of the storm strengthens quickly Wednesday Night, then winds will begin to ramp up quickly.  That would produce blizzard conditions over areas receiving heavy snow.

Such an event could reduce visibilities to near zero, and would threaten the outright closing of some highways.  As some Iowans found out just a couple years ago, conditions can become so terrible, that law enforcement is unable to even rescue stranded motorists.  In the Iowa City area, a blizzard two seasons ago forced the National Guard to rescue drivers stranded in the snow drifts. 

The combination of heavy snow and strong winds through Thursday Morning would also bring air travel to a standstill, not just here in Iowa, but the rest of the region affected by the storm.  This of course will have a major impact on the upcoming holiday travel.  All in all it’s a very bad situation that’s taking shape and one that everyone MUST stay up to date on.  We will monitor the latest trends and if they continue, we could see parts of the state upgraded to a blizzard watch as soon as tomorrow. 

Regardless of the final winter weather headlines, everyone in the path of this storm should stay abreast of the latest forecast and snowfall projections.  Get all the information you need before you venture out.  And always make sure you have essential items stashed in your car in case you do become stranded.  This is a very dangerous situation but one that can be prepared as long as everyone makes smart decision. 

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