Tuesday, January 22, 2013

North Arkansas Ice Possible


8:40AM Monday Update... This is just a quick update to show you how bad the NAM is right now.  This model is run 4 times a day.  Look at the difference between the Monday night run of the model compared to the Tuesday morning run.  This is valid at the same time, Thursday morning at 6AM.

This is the run last night showing the surface low in OK.  That's the black closed line with "1016" on it.  The warm front extends eastward through central and eastern AR.  That's the sharp pointed area along the back line extending from the low.  The faint gray arrows show you surface wind flow.  South of that front it's all southerly...WARM!!!!


And now the new run shows the low and warm front much further south with strong and cold northeasterly winds at the surface over central and northern Arkansas.  This is a HUGE difference!!!!!  Just a couple of days ago, this model was taking that surface low up towards St. Louis!  This model is just bad right now.  BUT, notice how it's trending towards the more reliable Euro and GFS.  See post below for possible icing northern AR.
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It's back to blogging!  Hope you all had a great weekend.  I just took a few days off work and really enjoyed it with great friends and family. 

The cold arctic air I was talking about for the past week is here!  As I cautioned you, where it would be directed was a question and it took aim on areas north and east of us.  Wind chill readings in MN and ND approached -50!  We're going to have a roller coaster over the next few days with a very important system to watch by the middle of next week.  Some computer model guidance suggests this could come through harmlessly while others show a round of strong storms.  This being 7-8 days away, we'll fine tune that forecast as we get closer, but pay attention to the 29th and 30th! 

Some long term forecasting gurus are shouting about a cold and stormy February for much of the central and eastern United States.  While their reasoning is deeply rooted in evidence and science, remember we're dealing with mother nature.  Let's see how this unfolds and keep a close eye on it.  There's a good chance they will be right, but you know how I feel about long term forecast (past 7-10 day).

Now onto the situation Thursday night into Friday morning.  Let's just throw out the NAM.  I haven't even looked at it this morning.  It has been in la la land all winter and it continues to amaze me people are still using it this season for their forecasts.   The ONLY way I'll ever do that is if it agrees with the GFS and/or Euro.  Also, the NAM seems to catch onto things once within 24 hours.  That's pathetic.

Yesterday, it took the surface low Thursday wayyyy north and no other piece of data shows that.  The Euro shows a surface low sliding east through the state late Thursday with surface winds staying east-northeast across northern Arkansas and surface temperatures around freezing.  The amount of frozen precip isn't much, but we all know that it doesn't take much to cause problems.

Here are the maps.

This is the Euro valid Friday night at midnight.  The dark blue line is the 32 degree line and you can see that cuts through northern AR.  Everything north of that is below freezing.  The green and gray indicates light sleet/freezing rain moving through that area.   It's a cold rain further south.
It's exiting Friday morning and the freezing line stays almost in the same place as precip moves through.
This is the GFS a midnight Friday morning.  The red line is the 32 degree line and there's very light precip coming through.  The next frame shoots the freezing line to the north so it says the light frozen precip would change to plain rain, but the Euro implies it stays frozen across the far north.
I called attention to this situation via twitter Monday and now the HPC has shifted the area where ice is possible further south.  This map shows you the chance for at least .01'' of freezing rain is greater than 50% across northern Arkansas.
In summary, at this time, it appears the target is northern Arkansas for light icing late Thursday night into Friday morning.  How long will it stay frozen is a question mark at this time, but we all know it doesn't take much to cause problems. 

3 comments:

Will said...

Yes Todd, you were correct that this last cold snap was directed North and East and that the NAM is not performing great at the moment but your favorite, (EURO) and mine (GFS) have also been erratic. I believe it's all about the trends and those trends as well as the "science" all indicated a significant cold this week, which did happen, just not here. Now on to next week...There is a significant storm and associated cold coming next week, bank on it. It's all about the timing as to what we'll get as I think that there will be a significant Severe weather threat as well as a major Winter storm for someone in our region. Only time will tell as it is the Long Range and as you have said many times, Long Range forecasting is just not that accurate but since I don't get paid to be a weatherman it's easy for me to make that forecast. One more good snow and then it's time for some Oaklawn weather.....

Will said...

To clarify, The cold that I am referring to is coming in the week of Jan 28th.

Anonymous said...

Interesting to note that today, NE AR was the coldest part of the state today. Then I realized it's because of the stratospheric warming event and whatnot which caused the NE to get arctic air.