December 16th event

[eyewall]

Good work Jeremy!

Need to put that link in your sig.

Thank you! I will go ahead and do that.

[DaculaWeather]

I like how FFC has lowered the low tonight to 31 with rain. Hmmm, do you think they know it might freeze?

[magpiemaniac]

Right on the border between 1" and 1-3", Eyewall. I'll take it!

Indeed. I'm a couple of miles north of the blue/green boundary. I hope this verifies.

[georgiawx11]

I like how FFC has lowered the low tonight to 31 with rain. Hmmm, do you think they know it might freeze?

I think temps will be rising throughout the night, and probably be near 40 by tomorrow morning's rush hour.

[jrips27]

As for this storm, not sure anything will make it over here before it warms up with it being pretty dry. Will keep update yall if I see anything.

[Lowpressure]

Nice work on the map eyewall, seems quite reasonable at this juncture.

[DaculaWeather]

From Snowdevil in west Georgia

Hi,

Edit: Sleet and snow now!! Heaviest of the day.

I have some stupid post limit and I dont know how to get the mods to lift it. But I wanted to tell you I live right north of Lagrange ga and we had sleet and snow about 2 hours ago and now about 20 mins ago we had all snow.

The snow was light but turned into legit flurries and it was all snow. But I got to tell you as soon as it starts it quits. The air is just too dry. You can post my message on the forum if you want. Hope this helps.

[georgiawx11]

There have been reports of Snow and Sleet in Carroll County, near the AL border.

[eyewall]

Thank you guys. I realize I will be continuing work on the formatting etc. and my wording of discos etc. It is a work in progress.

[DaculaWeather]

Here's the current thickness levels for us

[Brian]

Here's the current thickness levels for us

What does this mean?

[Lowpressure]

Brian

http://www.google.com/url?sa=t&source=web&cd=1&sqi=2&ved=0CBMQFjAA&url=http%3A%2F%2Fweatherfaqs.org.uk%2Fnode%2F152&ei=LAIJTcX6H4X6lweZh9TZAQ&usg=AFQjCNFnr_0GyI9zzXHmQbke1vOcMww-Aw&sig2=aVlLBMpDpVPiEjpip9Htjw

[BIG FROSTY]

I am working on building a site for the Sandhills region but I already posted a forecast there along with a call map.

Go to http://www.sandhillswx.com

The forecast and discussion pages are up and running. I am still working on the rest

In short here is the NC Call:

Looks good eyewall, I'll take my 1-3 and be happy

[georgiawx11]

Snowing in West Georgia. I don't remember FFC mentioning snow ? All I thought we were going to get was sleet and freezing rain ???

[DaculaWeather]

It's easier for me to copy and paste:

"Now that you know a little about thickness, it is time to apply these ideas to winter storm systems. When meteorologists make forecasts, if the thickness is large and the temperature near the ground is above freezing, it will rain. In contrast, if the thickness is small and the temperature near the ground is below freezing, it will snow. This thickness that separates rain and snow is called the critical thickness, which is defined as the 1000-to-500-mb thickness where there is a 50 percent probability of rain and a 50 percent probability of snow. This value is an important tool that meteorologists use when forecasting precipitation type for an area.

The standard value for critical thickness is 5400 meters, or 540 decameters (dm). However, 540 dm is not always the clear cut line between rain and snow. Sleet and freezing rain can also occur near the critical thickness depending on the temperature structure of the atmosphere. Critical thickness is not always 540 dm because it varies depending on such factors as elevation and location. As we will discover, the critical thickness is not always the best indicator of the fine line between rain and snow."

Critical thickness value and p-type forecasting

Thickness is the vertical distance between two isobaric surfaces, which is often proportional to the temperature of that layer. As such, empirical studies have shown that certain values of differing thickness have shown some skill in differentiating between rain or snow.

• 1000-500 mb (5400 m) Red Line
• 1000-700 mb (2840 m) Green Line
• 1000-850 mb (1300 m) Blue Line
• 850-700 mb (1540 m) Yellow Line

The magenta line is the 0c surface temp line.

[Brian]

Brian

http://www.google.co...DpVPiEjpip9Htjw

Thanks for the info, I have bookmarked it....:snowman:

[DaculaWeather]

Snowing in West Georgia. I don't remember FFC mentioning snow ? All I thought we were going to get was sleet and freezing rain ???

The air is so friggin cold and dry! Right now my site is estimating cloud height to be 6586 where it's -2 degrees. The air is still too cold for sleet and freezing rain, that will come later as the upper levels warm and the precip falls into colder air.

[radiobrian]

This image from WRAL made me laugh. Way to have the tongue of rain bend over Raleigh. This is the type of image that could send Brick over the edge.

[georgiawx11]

It's snowing well south of that 5400 critical thickness line.

[DaculaWeather]

It's snowing well south of that 5400 critical thickness line.

Maybe a met or someone with more knowledge than myself can explain that.

http://piercelegeion.com/meteo482/writing/5400m.html

[ams30721us]

Finally...

Winter Wx Advisory for NW GA

[MotoWeatherman]

I would expect to start hearing snow/sleet reports coming from the Atlanta area. A nice batch of precip is moving in at this time.

[snowlover91]

It's snowing well south of that 5400 critical thickness line.

The reason being, to my knowledge, is that the 540 critical thickness line is just an average of the heights from 500mb to the 1000mb level. Right now the 500mb temperatures are not exceptionally cold compared to normal, so as a result the thicknesses are higher than they normally might be. However the snow layer, generally 700mb to the surface, is below freezing and condusive for snow hence why you are getting snow south of the 540 line. It is used generally as a guideline and not the rule of thumb. Best way to know is by using soundings and looking at the entire column of air.

[georgiawx11]

Advisories as far south as Southern Alabama, and in GA only in the Extreme North ? Wow.

[jrips27]

Winter WX Advisory one friggin county away!!!!

[MotoWeatherman]

It's snowing well south of that 5400 critical thickness line.

Honestly the "540" thickness line is not the main tool when forecasting snow. Soundings tell the whole story. All that matters if you have enough of a freezing layer from cloud level to just above the surface to support the flake falling all the way down. I've seen it snow with thickness above 5460.

[MotoWeatherman]

Finally...

Winter Wx Advisory for NW GA

Now that's a cool map...bookmarked it.

[Ben]

I had some verrrrrry light sleet/graupel about 20 minutes ago here in Acworth. Now nothing.

[georgiawx11]

Nice little burst of snow here in West Georgia. Sleeting also. Some of these flakes are really big.

[jrips27]

Nice little burst of snow here in West Georgia. Sleeting also. Some of these flakes are really big.

Your in dallas right?