0z Canadian

[aggiecutter]

has a similiar solution to the 12z EURO with a 1055mb high centered over the central plains ridging down into Texas.

120hr...

http://meteocentre.com/models/glb00_120.html

144hr...

http://meteocentre.com/models/glb00_144.html

[southerngale]

Does that mean colder temps for us down here in Southeast Texas than most are anticipating right now?

I just checked one local met here (KFDM) and they have us with highs in the 40's for Friday and Saturday with lows in the mid-30's and then at freezing. I know they rely on the GFS a lot because they mention it often in their online forecast discussions.

[Stormsfury]

That is a very dense arctic high pressure and the SFC temperatures will be just as cold as the 850mb temperature scheme, if not colder.

[Air Force Met]

That is a very dense arctic high pressure and the SFC temperatures will be just as cold as the 850mb temperature scheme, if not colder.

Actually...down here in SE Texas...it is not unusual to have 850 temps 10-20 degrees F higher than the SFC during an arctic outbreak. The airmass is so shallow.

Here is a good example from Bismark. The SFC temp is -26C but the 850 temp is only -5C. So...it is almost 40F warmer just a couple of thousand feet above the sfc.



That is siberian air...and that is why the models have a problem forecasting it. It slides under the flow.

[GalvestonDuck]

I'm sorry, AFM, but you know me...just a simple weather watcher, not a pro.

Am I reading that right? Are you saying that the SFC temps will be colder than the 850 mb temps? So, a couple of days ago, when I was looking at the GFS model for 1/18, it showed a 850 temp of 15º for the Hou/Galv area. That means it will be less than 15º here at the surface? I mean, I get the terms "arctic" and all that. Been there, done that, used to live up north. But since I've lived here, the coldest I've ever experienced was 31º on March 3rd, 2002. Would we really get temps in the single digits on the island?

Or did I get lost somewhere?

[CaptinCrunch]

The artic front is futher south than what models show, at this time most temps along the KS, OK state line are at 32 and that will be the high for them today, NWS FTW has artic front coming across the Red River tonight before stalling till bigger push of cold air on Wednesday. Timing of this front with the approching Low from CA. will be tricky. Could see anything from Server Storms to the east and freezing precip to the north and west.

It's all timing at this point.

[sertorius]

CaptinCrunch:

The gfs and ETA, esp. the gfs, are hinting that that front is going to surge back Northwards tomorrow as a warm front-I'm not totally convinced of that, but the eta has trended much warmer here for the surface the last 2 runs-I just can't believe with that front that far south, that it can get back here-it all depends on the track of the low-if the low goes north of me here in Lawrence, then yea we will warm up.

[Air Force Met]

Am I reading that right? Are you saying that the SFC temps will be colder than the 850 mb temps? So, a couple of days ago, when I was looking at the GFS model for 1/18, it showed a 850 temp of 15º for the Hou/Galv area. That means it will be less than 15º here at the surface? I mean, I get the terms "arctic" and all that. Been there, done that, used to live up north. But since I've lived here, the coldest I've ever experienced was 31º on March 3rd, 2002. Would we really get temps in the single digits on the island?

Or did I get lost somewhere?

Yes...the 850 temps are usually quite a bit warmer than the sfc temps in an arctic front. Look at that Bismark sounding again. It's almost 40 degrees warmer at the 850. What happens is this: The arctic air is cold and dense. Arctic air is known as cA air (continental arctic). Normal cold fronts are cP (cont. polar). What happens is the arctic air is usually only 2000-3000' thick and is slides UNDER the cP air. IN the case of TX...it may actually slide under the maritime tropical (highly modified this time of year) airmass (mT). This is why models have a hard time...because you actually have two airmasses...one that is real shallow and likes to move straight south and the other that sits on top of it and wants to be steered with the upper flow like normal. That is why a cA airmass can move south for 2 thousand miles in zonal flow...because it is (in a way) disconnected with the rest of the flow.

There are two source regions for cA air that affect the US. 1) is Siberia and the arctic regions of Alaska. The source region of the current airmass is Siberia. The other source region for cA air is northern Canada. When the source region is Siberia...that airmass usually dives south into the plains. When it is northern Canada...then the airmass usually takes a path more to the east into the NE US. That is why I am bullish on the air coming all the way down...climo. Most of the time when you have a building ridge over AK and into Siberia...with temps<-50F...and sfc pressure of 1050mb+...that airmass will move into the southern plains...and it really doesn't matter what the upper flow over the central and southern US is doing. When the ridge builds over Eastern Ak and western Canada and the western US...then that airmass is usually shoved east...but the source region of the cA air is also usually over northern Canada when that happens.

[GalvestonDuck]

Very cool...you painted a perfect picture with your explanation (I tend to understand visual explanations better). I love it!

Thanks bunches, sir! It helped immensely.