Monday, January 27, 2014

Pattern Finally Shows Signs of Delivering Moisture

1:15 PM Monday update...  I don't want to hang my hat on a particular model run or two when it comes to a forecast that's more than a week away.  However, everything is pointing towards plain rain and even thunder starting a week from Tuesday.  We'll take that given the fire danger across the Natural State.  If enough cold air can get in front of this system and the track of the storm goes south, that could change.

I wanted to use this update to show you something very interesting when we look out even further in the long range.  I find it remarkable how cold it can get here in Arkansas without any snow cover over the state or just north of the state.  Many times arctic air will modify less as it descends south over snow fields.  The only snow fields are located well northeast of the state and I'll show you that below.  With the system next week, I'm very confident it will be a MAJOR and very SIGNIFICANT storm system and it will lay down a ton of snow.  At this time, it looks like the favored area would be from the Texas panhandle up to the I-70 corridor and points eastward.  Following that storm is the possibility for another plunge of cold arctic air.  This time, there will be deep snowpack to the north and the potential is there for more bitterly cold temperatures.  

Here's snow cover across the country this Monday according to NOAA.  Look at the lack of it over the Plains!!!

This is the new European model total snow out to 10 days.  You can clearly see the swath of snow with the storm Tuesday/ Wednesday over the Gulf coast up into the Carolina's, AMAZING!  Now, look at the huge and fresh snow cover over the plains into the Great Lakes!!! That's from the system estimated to arrive February 4th and 5th.  As that storm leaves, a new arctic high may come out of Canada and advance over that cold snow north of us.

Lo and behold, here's the climate model (CFS) for the period February 5th through the 10th.  This is showing you near surface temperature mean forecast departure in degrees Celsius.  That's some very cold air again over the plains banked up along the front range of the Rockies diving into the southern plains and mid south.  This is indicating readings which could be at least 10 degrees Celsius below where they typically are for this time period.  This isn't showing you what the temperature will be, but the departure from what it SHOULD be for this time period.

The cold is here and it's here to stay until the middle of the week.  You know me, I'm already looking well past that.  The wildfire situation has become very bad and there's no relief this week.  However, I see signs of a significant change the first week of February.  It's a change that could bring large amounts of moisture.  I know many of you want to know what type of precipitation will be falling.  

First of all, this current cold snap breaks Thursday and we'll have rain chances this next weekend.  Not a lot of rain, but some.  Temperatures will warm up.  I just looked at the overnight run of the Euro and it indicates readings going back into the 60s by Friday, then cooler temperatures arrive for the weekend with some wet weather possible.

Next week shows an active and very challenging weather set up.  Previous runs of the European and GFS showed quite a bit of cold air around with the storm track just south of the state.  However, the new Euro and the Canadian indicates the track of low pressure will be much further to the north opening up the possibility for heavy rain and thunder.  The GFS wants nothing to do with that so we have an interesting system to watch by next Tuesday February 4th.  This being 8 days away, getting too specific is dangerous and what I like to call "meteorological malpractice".  I'm looking to an index called the "arctic oscillation" (AO) for some guidance.  When this is in its negative phase, it tends to send cold air to the south.  When it's in the positive phase, warmer air usually finds its way into Arkansas.  Meteorologist John Lewis with the National Weather Service office in North Little Rock presented some research a couple of years ago that really got my attention.  When this index jumps rapidly from negative to positive, we open up the chances for heavy rain and severe weather.  This makes sense if the cold air retreats and the storm track can shift to the north opening up the Gulf of Mexico which is our main moisture supply.

Most of the data has shown this index to remain neutral to negative as we go into February.  One run of the operational Euro from last night is the first time I have seen this pop into the positive.  Until I see more evidence, I'll consider it an error.  The GFS and a climate model called the CFS still indicate this will remain negative. 

Here's the bottom line, it appear a significant storm system will arrive by the beginning of next week.  As is usually the case this time of year, the track of this storm is far from known and it's crucial when dealing with what kind of weather we will experience.  The good news out of this is the fact our wildfire danger may improve.

The overnight run of the Euro shows low pressure over the Arklatex moving northeast.  This is valid Tuesday, Feb. 4th.  Most of the state has milder air with only some cold air locked up over the far north.  This solution is a rain maker as moisture can come in off the Gulf.
This is the GFS valid at midnight Feb 4th.  The surface low is forming over west TX.  This is further south and west than the Euro.  Remember, buying into the specifics is pointless.  The message here is cold, cold, cold with a new area of arctic high pressure nosing in from the north.  This is hinting at some frozen precip, especially from OK to the northeast.
By noon Tuesday on the 4th, the GFS shows heavy amounts of moisture with the low well south tracking more to the east, northeast.  IF this solution were right, it would turn out to be a major snow and ice storm for most of the plains north and east.

In summary, don't look at the specifics at this point.  I'm not saying we're going to have wintry weather and I'm not saying it's only going to be rain.  The point of this post is to present to you the challenges facing us next week.  That's the purpose of this blog and why I'm so thankful you come here. 


Stacy H. Pine Bluff said...

Thanks so much for loving the weather, Todd! You make it fun and educational. Also, it's nice to have someone who loves snow as much as I do, reporting!

Anonymous said...

Great info, Todd. This is why I always come to the KATV weather blog whenever I want complete information about the forecast. My crazy husband goes to accuweather or Not me. I trust a local meteorologist who is passionate about the science and wants to spread his knowledge. Thank you, Todd!

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