Monday, December 08, 2014

Upper Low We Must Watch For Snow


Whenever you're talking about a cut-off area of low pressure that's a week away, much can and will change.  However, the Euro and GFS indicate a similar track to a strong area of low pressure aloft moving through the mid-south.

On the Sunday news I talked about a more active week in weather on the way.  Not this week, but the next.  There should be a significant storm moving from west to east across the country.  Many times, these lows track north of east, however, this one could track south of due east which is interesting.  There will NOT be any arctic air in place for this system to work with so it must develop its own cold air and this is entirely possible.  

I'll take you back to December 2010 or 2011 (my memory is failing me this morning).  We had a cut off area of low pressure move through at night without any true arctic air in place.  Conventional wisdom says we need a negative arctic oscillation (AO) to get snow around here since that usually delivers cold air deep into the lower 48.  This particular time, the AO was positive.  If the track of the low is just right and it's strong enough, enough lift along and north of the track can cool the atmosphere just enough to produce a quick hitting snow.  These are usually never big storms, but they get your attention.

Like I said, trying to predict the exact path and strength of one of these lows 7 days out is nearly impossible, but since both models show this possibility, let's watch it.  At this time, I think the best forecast is one for rain a week from today, but just know I'm watching it!  It's also worth noting the Canadian model takes this system so far south, we stay dry.  However, I'm not a big fan of the Canadian model in this time range.

This is the Euro next Tuesday morning at 6AM.  This is the 500 mb chart and it shows a significant storm moving across east Texas and Louisiana.  This is an interesting track and it's worth watching.
The GFS is a touch faster.  This is valid at noon on Monday, December 15th.  The low is a bit further north as well and tracks northeast.  So you see both models have the storm, but differ in timing and location.  You want snow?  Then you want this to track just south of your location and at night when you can get the temperatures as cold as possible.  
In summary, don't get your hopes up just yet.  It's worth watching, but we're dealing with something many days away and it's a type of system notorious for difficult forecasting.


2 comments:

jimmylee42 said...

Todd-I remember the snow and I just double checked with the NWS site. It was the night of Dec 6 2011, started before midnite and ended early Dec 7 total l.6 inches maybe 2 or more in WLR. Didn't stay around long because of warm ground and no arctic air like you said.

Anonymous said...

Latest update from Joe Bastardi shows Arkansas and other states getting hammered starting the week of Christmas. The hits keep coming from that point onward. It will be interesting to watch.