Tuesday, November 26, 2013

More Extreme Arkansas Weather In December?



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November has gone from one extreme to another and December has that same potential as well.  What an amazing 10 days we have seen here!  Here's something AMAZING in my opinion, but I'm a weather geek.  We had the 6th warmest November day on Sunday November the 17th in Little Rock weather history with 84 degrees.  Exactly one week later, we had the 6th coldest November day in Little Rock weather history with 34 degrees.  That's a difference of 50 degrees!  By the way, we shattered the daily record high temperature on November 17th with that high of 84.  It broke a record which dates back to 1921.  

Here's something else extreme...  The high temperature last Sunday of 34 degrees ties the previous coldest maximum for the day (34 in 1950)!  Amazing stuff, eh!!!

We're heading for a low temperature Thanksgiving morning in the lower 20s.  The record low is 19 set in 1887!!!!!!  So we could challenge a record which has stood for more than 100 years.  Are you shaking your head yet in disbelief?  As they say in those commercials, but wait, there's more!

We're going to dig our way out of this hole we're in.  Temperatures should go to average or even above for a time next weekend into next week.  However, I'm already seeing signs of another big push of bitter arctic air.  As I always preach, long range forecasting is extremely tricky.  But when you see a big ridge of high pressure building over Alaska, LOOK OUT!  So while we may get into the 60s again and MAYBE 70 for a little bit, it may not last and another deep freeze could grip the state.  Here's the difference, we'll be into December and these air masses get colder and colder as we head into winter.  Will this happen?  Remember, long range forecasting is not a perfect science.

We're looking here at the European 10 day 500 mb map.  At jet stream level you can see the ridges and troughs across the northern hemisphere.  Remember, the flow is from west to east around those ridges and troughs.  Look at that big high (ridge) over Alaska!!!  The Euro dumps the downstream (cold) trough over the western United States.  If this happens, the cold would be delayed and eventually get  shoved eastward.  What could happen, with all the cold air up north, sometimes that low level arctic air can spill down the plains.  We're talking about something 10 days away so this map will not verify exactly.  What if that trough over the west is centered a bit further to the east?  Whole different ballgame!!!!  What I have learned over the years is that when a ridge builds into Alaska, they warm up and we cool down!
The GFS has more of a blocking look to it with the potential for cold, low level arctic air to spill down the plains as the trough over the west is not as deep  with more potential for troughing further east.  Only time will tell how this plays out.  But look at that Alaskan ridge.  There it is!  Just like the Euro above!
Here are the Euro surface temperatures in 10 days.  Look how the cold air corresponds with the placement of the trough.  Ridging in the southeast keeps it mild here, BUT look at all that cold air in the northern Rockies and Canada!  Those are readings around -20 degrees. It would modify the further south it travels.   That cold pool of air may get a shove south and the models will not handle this well in the long range.
The GFS in 10 days shows the chilly air over Canada with the leading edge in the northern Plains.  This is similar to the Euro, but not as cold.

In summary, after a cold week, I do expect temperatures to moderate.  After that, there's the potential to return to some cold air again.  There are so many questions as to how this plays out.  Where is this cold air going to go?  How strong is it?  As I said above, when you see a ridge over Alaska, look out, especially one that strong.  The European model implies there's a ton of cold air.  It's heavy and dense and can flow downhill very easily like water on a tilted table top.   I'll keep you updated!

2 comments:

Will said...

Hey Todd, I also am seeing quite a bit of conversation on some of the weather forums about some historic cold in Mid December. I know you're a big fan of the the WeatherBell site as am I and I think this headline from that site says it all....

Upper Ridge Over Alaska, Strong Negative WPO Set Stage for Historic Cold Threat Weeks 2 and 3

Will said...

I love the cold and I think it's on the way so get your coats and scarves ready, the Arctic hounds are coming next weekend..... :)

I need Snow Bird Bob's help here to get all these bloggers wound up.