Monday, January 07, 2013

Mild To Wild?



2PM Monday Update... Remember, please don't panic and please read this entire blog that I started early this morning.  This is just one model that shows something interesting Sunday, but I wanted to show you the things I look at.  Other models just show a cold rain.

Look at what I'm talking about when it comes to shallow arctic air.  The American GFS continues to indicate another wave of moisture most of Sunday where most previous runs of the Euro do not.  HOWEVER, the new Euro does show additional light rain moving into the southern half of the state Sunday afternoon so it may be the start of a trend with that model.  If you look at the surface temperatures with the European model valid next Sunday, most of the state is ABOVE freezing where the GFS brings much colder air into the state at low levels.  So we have a fight on our hands.  Will it be plain rain or something else.  Here are a few maps below explaining the situation.

This is a forecast sounding from the GFS valid next Sunday at noon.  We're looking in the vertical... from the ground up.  I have outlined in black the freezing line which goes from the middle of the sounding to the upper right.  The temperature is the line in red.  Notice the shallow low level arctic air pushes the temperature to the left of the freezing line.  This is very low level and shallow arctic air working in from the north.  This isn't ideal for a fast southward movement since the Ozarks would delay the onset.  Usually, a northeast wind at the surface is needed.  Now, look just above that shallow layer and look how the temperature goes to the right of the freezing line.  This is a very large and significant layer of melting.  So anything falling would NOT be in the form of snow.  If the subfreezing layer at the surface is significant, and I have doubts about that, we're talking about ice.

Here's the GFS using BUFKIT. This is read from right to left.  Those green lines indicate rainfall.  The first set of green lines show the mid week heavy rainfall event, then a break, then more rain with the arctic front Saturday.  The red lines indicate frozen precipitation Sunday.
The European is now showing rainfall in southern AR Sunday, but look at the white line at noon Sunday.  That's the freezing line at the surface and it's wayyyyy north so it would be just a cold rain according to this model.

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10:30 AM Monday Update... Here's a quick video update showing you the newest GFS just in this morning.  PLEASE READ THE FULL POST BELOW.  This is just 1 computer model and it's very much in the long range, but I wanted to show you the things I'm keeping an eye on for you.




For those of you who have been coming to the blog over the past few years, you know the purpose of it. It's not to necessarily make an official forecast, but to show you some of the data meteorologists must look into when we sit down to make that forecast.  There are things we must consider and place in the forecast and other things we just simply ignore because we know it's garbage.  I have always intended this blog to give you that inside look at how we "make the sausage".

In light of the historic Christmas storm, we must be very careful with what we put out there because we do NOT want to cause any unnecessary panic.  When a quarter of a million people lose electricity and sustain damage to their home and property, the mention of more winter weather can stir anxiety.  For others, according to the poll on the right side, they want MORE snow!  I lost power for 3 days and I still want more snow.  I DON'T WANT ICE!  Remember what I said about the Christmas storm, 10 inches of snow doesn't cause devastation.  Heavy ice, 10 inches of snow, and high winds WILL cause devastation.  Add into the mix weakened trees from the historic summer drought and it was the perfect storm for power outages.

With all that said, I'm not going to stop showing you the things I'm looking at on the computer models.

It's important to note here the vast differences in the long range data.  It really is the GFS vs the Euro next weekend.  One will be right or there could be a compromise between the two.  It's also important to tell you to relax, this could turn out to be a bunch of nothing.  Or it COULD turn out to be more winter weather.  IF that happens, at this time, I DON'T see anything as powerful as the Christmas storm.  

First of all, I think I have gotten the message out there about the potential for heavy rain Wednesday.  There could be a few thunderstorms as well.  At this time, the severe potential looks very low, but it's worthy of watching as we get closer to mid week.  The highest threat for severe storms will exist south of Arkansas.

Now onto the model data for next weekend.  After the mid week system exits, I fully expect well ABOVE average temperatures until a powerful cold front arrives late Saturday.  This should bring temperatures back below average next week.

The differences exist next Sunday.  It looks like the GFS is hanging a piece of energy back and developing an additional wave of low pressure along the arctic boundary once it's past Arkansas.  With the exception of a couple model runs, the GFS is consistent in throwing a few hours of precipitation back into the colder air.  IF this were to verify, it could be frozen depending on how intense the low level air is behind the front.  The Euro simply moves the front threw here with little if any frozen precipitation behind it.  Here's the data.

This is the upper level (500mb) chart from the 00Z GFS valid next Sunday morning at 6AM.  I know this looks like my 3 year old drew on it, but it has meaning.  The cold air is moving into place at the surface at this time, but look out over southwest TX.  See that trough and those yellows?  That's upper level energy coming at us from the west.  This would in turn develop low pressure along the cold front just east of us and throw precip back into the colder air.
The Euro at the same time is much less gung ho about it.

Back to the GFS.  It shows the surface low over the Great Lakes and a trailing cold front east of Arkansas.  The 540 line is still NW of Arkansas, but low level cold air is oozing into the state.  Look at the precip developing over TX by 6AM next Sunday.  That overspreads the state during the day.

And here's the Euro at the same time, there's less development and this is more progressive moving to the east.
In summary, it's wayyyyy to early to make a call on this, but it is something to watch and that's what we do on the Arkansas Weather Blog.  The other long range models do bring in pieces of energy into the state, but further down the road so the pattern looks very active.  If you're a winter weather lover, this type of pattern can be exciting.  Let's just enjoy this mild week and see what kind of "wild" the following weeks can bring.

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