Spring in Winter

What transition from last week to this week.  Lets have a flash back on last week.  Here is what the setup was in the upper levels of the atmosphere. 

This is a 300mb map for the middle of last week when all of the cold weather was coming through.  The purple colors is what known as a jet streak which is an area of strong winds compared to what is surrounding it.  This map shows where the jet stream is which separates warm air from the south and cold air from the north and is caused by this contrast in temperatures.  Now what this is showing is the path that the cold front travelled that gave the southern states all of the snow.  The winds are significant because they are showing how fast the weather pushed on through which holds strong because the snow lasted less than 12 hours before it completely left Mississippi and rapidly moved across the other southeastern states.  The pink lines are areas of upper level divergence meaning areas that air is being lifted from lower levels of the atmosphere creating some instability which is a key factor for areas of precipitation.  The main point of the map is to show how deep the trough is that was pushing all the cold, arctic air into the Southeast region.

Now lets look at the pattern in the upper levels for today at 00z on Thursday (this is at 6PM CST). 

Can you see the difference?  If not, then allow me to tell you and show you what makes this week so much different, and more spring-like, than last week.  First, I would like to point out the ridge that is visible in the central part of the U.S.  This may not seem like anything special, but what it means is that warmer air is pushing further north and giving the southern states warmer air along with a more stable atmosphere.  The last thing I would like to point out is where the jet stream is.  Much further north than last week which keeps us away from the paths of low pressure systems.

So now you know the reason why this week is the way it is, last week was the way it was, and why it all happened.  For all of you spring lover's, expect the current pattern to persist because these upper level troughs and ridges last much longer than the ones closer to the surface.  Since the ridge is west of the southeast states, this day to day pattern of warm, spring-like temperatures in the upper 60's and lower 70's and some places much warmer will continue to occur until this weekend.  A trough will reach the Mid-Atlantic Region and could spread some showers in for the Southeast Region and with the warm temperatures the possibility of a thunderstorm here and there is not out of the question.  A short ridge will pus the trough out of the way leaving the southeastern states dry for Tuesday and Wednesday.  A deep, slow moving trough will be creeping towards the southern states in the middle of next week giving way for some higher chances of precipitation and cooler temperatures.