We’ve been talking for a while now about the chance to get a “nice” snowstorm by the end of the work week.  As it stands now the area will be affected by a large storm that will contain all snow for a change.  Some other details such as accumulation range are a bit hazy because of the environment the eventual surface low will track.  I’m going to break down the things we are watching as things start to come together in the next couple of days.

First off we are going to take a look at the storm itself.  Yep, you are looking at her.  This dip, outlined by the blue arrows is the key for everything coming together.  The Water Vapor Imagery shows us how much moisture is in the mid levels of the atmosphere, and with that, we can see how the atmosphere is moving.  The dip, meaning there is a pocket of cold air a loft in the atmosphere, will move down the west coast of the United States.   (The land mass directly above the “U” shape is Alaska.)

Wednesday, a Surface low will develop in the four corners region of the United States.  The next few graphics will show how the storm will evolve by the end of the week.  Southern Minnesota and north Iowa will likely see a brief period of heavy snow initially Thursday evening that could last into early Friday morning.  Snow has the chance to continue to fall into early Saturday morning.  The snow, however will be much lighter going forward with the event, and the heaviest snow should fall as the storm starts on Thursday.  We will take a look at why this will happen after the sequence of graphics.

Notice the center of low pressure doesn’t move much from Thursday night to Friday night.  That is because, the atmosphere is in a blocking pattern so the pipeline will be clogged up.  That will in turn make a long duration snow event, but it will also tend to give us lighter precip during the event since the storm will be battling a ridge of high pressure that is blocking things up.  A change in this pattern could cause significant changes to the storm and therefore the forecast over the next couple of days.   The picture below shows the dip that is currently (as of 2/17) near Alaska, now in the four corners and heading towards a ridge of high pressure.  That ridge will act to weaken the low a little bit, but also cause it to stall close to the area, keeping us in the light snow for a long period of time.

As things become a little more clear, we will fine tune tune the details!

Posted under winter, winter weather

I’m going to break down the science behind this extended sunshine.   We are expecting sunshine and dry weather to persist at least into Wednesday.  The next chance of rain will come by on Thursday and it will be a slight chance at that.  So why so sunny?  We are currently in a blocking pattern in the atmosphere.  Think of this as an unstoppable force up against an immovable object.  This is the current set-up in the atmosphere:

This set up is known in meteorology as the omega block, in the next image you will be able to visualize why.  Air flow around a low pressure system is counter counterclockwise. For a high pressure system it is just the opposite.  It is clockwise.  Think of these systems as gears in a clock.  The high (The blue H on the map above) is being pushed down, by the low pressure on the right, but it is also being pushed up by the low on the left.  Therefore nothing is able to move and everything gets blocked.  Long story short, the high pressure stays where its at…over us for a couple of days.  The pattern will stay like this until one of the systems starts to weaken.  The east and west coasts are getting the short end of the stick on this one.  They will see cooler temps and rainy conditions while us in the midwest will see sunshine!!   Sometimes these blocking patterns can last over 10 days!!

This is why this pattern is called the omega block:

This is a look of the pattern in the middle of the atmosphere.  The orange colors represent warm air and the yellows and greens represent cool air.  Notice the two areas of cooler air to the east and west.  That is where our two lows will be..and notice the warm section in the central part of the country…that is out high.  The shape of the warm air almost looks like the Greek letter “omega”.  The “omega” is pictured below.

Hope you all enjoyed this meteorology lesson!  Enjoy the sunshine!!

Posted under atmospheric phenomenon, just cool, spring, weather