Friday, January 04, 2013

Think It's Cold Now? Look At This...

This blog post is strictly about cold air and mostly NOT about any snow or ice.  Forecasting precipitation in the long term is nearly impossible.  I'm looking at trends on the various long range computer models and I see some specific trends that I feel confident enough to talk about here.

First, this week and most of next week will be our "January Thaw".  We have an interesting system coming through here by the middle of next week that looks to be mostly a rain maker and a few thunderstorms thrown in as well.  However, this storm looks to be closed off and these can throw curve balls.  While the models weaken the cold air signature underneath the upper low, I think it's possible for a wintry mix depending on the track.  That track is far from certain right now, but my best guess at this time is from Texas into eastern Oklahoma and maybe clipping northwest Arkansas.  Most of us will stay in the form of rainfall with this, but it's at least worth watching to see what happens underneath that low.

Second, after that system departs, we'll have a very brief warm up as a new round of arctic air moves into the western United States and into the plains.  That arctic air will surge south and COULD affect Arkansas by the end of next week thus ending our January thaw.

Third... and this is very iffy right now due to the long range, but it's at least possible for this cold air to stick around.  It may come in waves, but this pattern looks sooooooooo much different than what we had last winter.  There really is no comparison.

Like I said, I'm not going to speak about any precipitation chances other than the middle of next week.  Once and IF I see anything, I'll let you know.  Here are a few maps below which backs up what I'm saying above.

This is the European next Thursday AM.  It's 6 days out so this isn't likely to verify 100% whatsoever.  But it does show you the things I'm looking at across North America.  Let me explain what you're looking at here.  You see the greens over AR, OK, KS and MO?  These colored contours you see are reflecting the upper level low pressure area coming through with mostly rain.  Do you see that closed white circle?  That's a pocket of cold air aloft and is the "540 line" which does help us forecast where upper level conditions can be favorable for the production of snow.  The big question mark here is the surface temperature?  While the chance is low, it isn't impossible to get a rain/snow mix, especially across the higher elevations of the Ozarks.  This is a low chance, but I thought I would point this out to you since these closed lows can throw curveballs in our forecast.  Now onto what's happening northwest of the state.  You see all those blues?  That's cold air surging south out of western Canada and into the western United States and the northern plains.  The area between the closed low over AR and that surging cold air will be our brief warm up.  Look at that closed black circle in southern Canada.  That's the surface low and a trailing cold front south of that marking the leading edge the cold air and the end of the January thaw.
Fast forward to Saturday morning January 12th.  A wave of low pressure near Chicago is moving along the arctic boundary.  The counterclockwise flow into the low is wrapping cold air behind the circulation into the southern plains and even into Arkansas.  The black lines are isobars.  There's a significant pressure gradient between that low and the arctic high.  This would result in windy and cold conditions for most of the state.
According to the European model, the cold air is in and out quickly.  Look at the surface high over the Gulf coast.  A return flow is setting up quickly and temperatures are milder, but there's another batch of cold air moving out of Canada heading south.  The GFS model also shows another batch of cold air taking aim on the south as well, but there are differences as to how this plays out.  That can be expected since this is very, very much in the long range.
In summary, the January thaw will be here for the next week with temperatures hovering near average (50 degrees) or even slightly above.  The system next Wednesday looks to be mostly rain, but lets keep a watchful eye on the Ozarks and where that low tracks.  This will be followed up by a brief warm up, then cold air moves back into the country and is likely to impact Arkansas.  More specifics as we get closer here on the Arkansas Weather Blog.


Anonymous said...

Sounds interesting. Wonder how cold it will get!

Will said...

Long range guidance continues to advertise very cold air coming our way in the 10+ day time frame. Depending upon what model / guidance you chose to believe it could be transient shots of cold air more like the EURO is suggesting or more of a longer duration event which is what I think will happen as a result of the Stratospheric Warming events that will result in the Polar vortex splitting. We had one of these events last year but all the cold air went to Europe which was extremely frigid last year, if you remember. The EURO hasn't been that great on the long range side of things this winter so I'm going discard the EURO for the time being. I think this air will be the coldest we've had since maybe the great freeze of 1989.

I would love to hear SnowBirdBob's thoughts on this.......

Joshua said...

This might be a stupid question, but is this a Rossby Wave action? Also, how long are you thinking the cold will stick around?

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