Friday, December 07, 2012

You Want Cold? I'll Give You Cold!

9:50 AM Friday Update... Remember this is ONLY 1 model showing this, but I wanted to throw this out there.  Remember, this is NOT our forecast at this time, but I'm watching it carefully.  I have mentioned below the chance for some of the rain to change over to some snow flurries as the precipitation comes to an end Monday morning.  IF something like this were to happen, remember while it would be much colder, temperatures at the surface will be above freezing and the ground temps will be warm as well from all the warmth lately.

This data is from the NAM and it's the BUFKIT profile for Little Rock.  I'll explain what it means below the picture.

You must read this from right to left.  The bottom line in brown shows the time.  The right side is now and the far left is Monday morning.  The green lines indicate rain and the red solid line indicates the 2 meter temperatures according to the NAM.  Look at that red line dive as the cold air pours in Sunday night into Monday morning.  The orange line could be a little sleet, then the blue lines show a few hours where we COULD have a chance for LIGHT snow.  This is ONLY one model and NOT the forecast right now, but I'll keep you updated.

  The much talked about cold front here on the blog will blast through the state late Sunday, but let's put this into a little perspective.

The average high temperature this time of the year is in the mid 50s.  Readings for the first several days of this month were close to 20 degrees ABOVE that average.  Now, I think Monday and Tuesday will have the potential to only make it into the mid 40s at best.  That's about 10 degrees below that average.  So this is nothing unusual, but it will be a shock to many of us considering how warm it has been.  Do the math and there will be a 30-35 degree swing in regards to our high temperature.  So the bottom line, it's going to finally feel like December and early winter and I'm extremely happy about that.  According to the poll on the right, it looks like many of you are as well.

Also, there's something new I haven't done before.  Check out the countdown clock
to the right.  This is the estimated time of arrival of the onset of colder air and it could be off by an hour or two.  I'll adjust it as we get closer.

Not only will there be colder air, but there's a very slight chance for a snowflake or a little sleet.  THIS WILL NOT BE A BIG DEAL AND THE CHANCE IS VERY SMALL.  ANYTHING WILL BE LIGHT.  Remember, temperatures will be still above freezing, most of the moisture will be gone, and surfaces are still warm.  I'll explain below.

This is the GFS valid Sunday at 6PM.  The front is entering central Arkansas as cold high pressure dives down the plains.  The black, solid lines are isobars.  With the circulation around the high clockwise, strong northerly winds will develop after frontal passage and could reach 20 mph+ Sunday night into Monday.  If you look closely at the tiny arrows, you can see where the wind at the surface is coming from.  Across the NW half of the state, it's northerly, and the south half is southerly.  There will a battle in temperatures at this time across Arkansas.  The shaded areas of green are precipitation amounts over the past 6 hours.  Rain and thunderstorms will be likely.  The severity of those storms will depend on instability.  Clouds will help hold it down I think.  However, we'll watch that carefully, especially across the south portions of the state.

By the time you wake up Monday morning at 7AM, most of the moisture is exiting and the cold air is pouring into the state on strong northerly winds.  That blue dashed line is the famous "540 line".  This is typically the location of the rain/snow line, but remember the moisture is leaving.  I would not be a bit surprised to see a spit of snow flurries or a sleet pellet Monday morning as the moisture leaves the state.  Again, NO big deal.
This is the 500 mb chart from the GFS Monday morning.  There's still some energy out to the west which will bring cloud cover with the cold air moving in.  I think highs will stay in the 30s up north and only 40s central and south.  Also, because this piece of energy is still west of us, I can't completely rule out a flurry or sleet pellet until it moves east.  Again, NO big deal.


1 comment:

donaldwaynebrown said...

very good job Todd,,thanks! bring on the four letter word,,,{SNOW} :)

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