Keeping a close eye on your blog knowing that you're keeping a close eye on the weather for us.

Are you telling us there is a greater potential for snow and accumulations next week Steve?

I've already got plans for our snow days in Gwinnett! it can't be a bad snow! please tell me it ain't so!

LOL!!! Mention snow and people come out of the woodwork!

The system Thursday is marginal as I said above. I was actually kind of shocked to see the Atlanta NWS issue a Special Weather Statement for Thursday, they are usually very conservaative. Birmingham NWS (upstream) doesn't believe they'll have any issues. We'll know much more tomorrow.

As far as next week goes, all the SE NWS offices are finally talking about the cold air, and according to the Atlanta NWS, it will arrive here on Sunday night/Monday. There will be several reinforcing shots of cold air next week. It's too far away to look of for precip until we get the cold air in here.

1st call by one meteorologist
http://www.daculaweather.com/images/2013_01/1stcall.jpg

Video from the NWS about Thursday
http://youtu.be/vWoXbqFuA04

Now... on the other hand, the HPC says this...

SYSTEM MOVING THROUGH THE SOUTHEAST
PREFERENCE: NON-NAM COMPROMISE WITH AVERAGE CONFIDENCE

THE 12Z NAM WAS STRONGER THAN THE OTHER GUIDANCE ALOFT, WHICH
LEADS TO A MORE NORTHERLY SURFACE LOW TRACK ACROSS THE SOUTHEAST.
THE 12Z NAM LIES ON THE NORTHERN FRINGE OF THE 00Z GLOBAL ENSEMBLE GUIDANCE WITH ITS SURFACE LOW SOLUTION (WITH THE 12Z GFS NOT THAT FAR BEHIND WITHIN THE SOUTHEAST), AND EVEN THE 09Z SREF ARGUES FOR A WEAKER SOLUTION ALOFT/MORE DEPRESSED SURFACE LOW TRACK, WHICH IS WORTH NOTING CONSIDERING ITS NUMBER OF MEMBERS WITH WRF PHYSICS (THAT WOULD OTHERWISE FORECAST A STRONGER SOLUTION ALOFT). THE SYSTEM SHOULD SHEAR OUT/WEAKEN AS IT MOVES THROUGH THE SOUTHEAST, MOVING UNDER THE BASE OF THE EASTERN TROUGH AT THAT TIME, WHICH ARGUES AGAINST A NAM-LIKE SOLUTION. THE PREFERENCE IS FOR A NON-NAM COMPROMISE SOLUTION (WHICH EFFECTIVELY DEALS WITH UNCERTAINTIES ALOFT AND AT THE SURFACE) WITH AVERAGE CONFIDENCE CONSIDERING ITS PROGRESSIVE NATURE.

Basically, they are saying the system will shear out and weaken. In order to get anything here we would need a strengthening system. Who's correct? :-) That's part of the fun!

408 AM EST WED JAN 16 2013

...BRIEF WINTER WEATHER POSSIBLE ACROSS NORTH GEORGIA THURSDAY
AFTERNOON AND EVENING...
...BLACK ICE POSSIBLE ACROSS NORTH AND PORTIONS OF CENTRAL GEORGIA
THURSDAY NIGHT AND FRIDAY MORNING...

A STRONG LOW PRESSURE SYSTEM WILL MOVE ACROSS THE STATE ON THURSDAY.
AHEAD OF THE SYSTEM...A DEEP SOUTHERLY FLOW WILL SPREAD AMPLE
GULF MOISTURE NORTHWARD...RESULTING IN WIDESPREAD RAIN ACROSS
NORTH AND CENTRAL GEORGIA. AS THE ASSOCIATED COLD FRONT PUSHES
INTO THE CAROLINAS THURSDAY AFTERNOON...A DEEP COLD AIR MASS WILL
BEGIN TO SPREAD INTO THE AREA FROM WEST TO EAST THURSDAY WITH
TEMPERATURES GENERALLY FALLING THROUGH THE DAY.
... continued

RAIN IS EXPECTED TO MIX WITH AND CHANGE OVER TO SNOW OR A
SNOW/SLEET MIX ACROSS PORTIONS OF NORTH GEORGIA THURSDAY AFTERNOON
AND EVENING. DESPITE WARM GROUNDS FROM RECENT UNSEASONABLY WARM
TEMPERATURES...THERE IS THE POTENTIAL FOR SOME LIGHT SNOW
ACCUMULATIONS ACROSS PARTS OF THE NORTHWEST GEORGIA MOUNTAINS
DURING THE LATE AFTERNOON HOURS ON THURSDAY...AND PARTS OF THE
NORTHEAST GEORGIA MOUNTAINS THURSDAY EVENING. ACCUMULATIONS ARE
EXPECTED TO BE LIGHT...LESS THAN ONE HALF INCH...AND WOULD BE
MAINLY OVER ELEVATED AND GRASSY SURFACES.

ALTHOUGH LIGHT SNOW COULD BE SEEN AS FAR SOUTH AS THE NORTH
ATLANTA METRO AREA...NO ACCUMULATION IS EXPECTED OUTSIDE OF THE
HIGHER ELEVATIONS OF THE MOUNTAINS. AT THIS TIME...NO WIDESPREAD
TRAVEL DIFFICULTIES ARE EXPECTED WITH THE INITIAL SNOWFALL
THURSDAY AFTERNOON AND EARLY EVENING.

... continued

OF GREATER CONCERN HOWEVER IS THE POTENTIAL FOR PATCHES OF BLACK
ICE DEVELOPING ON BRIDGES AND OVERPASSES FROM LATE THURSDAY
EVENING THROUGH MID FRIDAY MORNING AS TEMPERATURES FALL BELOW
FREEZING. NORTHWEST WINDS BETWEEN 10 TO 15 MPH WILL HELP TO DRY
ROADS OFF AS THE PRECIPITATION EXITS THURSDAY EVENING...BUT THIS
WILL LIKELY NOT HAPPEN QUICKLY ENOUGH TO ELIMINATE THE BLACK ICE
POTENTIAL. THE POTENTIAL FOR BLACK ICE EXISTS AS FAR SOUTH AS A
COLUMBUS TO GREENSBORO LINE. HOWEVER THE GREATEST THREAT REMAINS
IN PORTIONS OF NORTH AND WEST CENTRAL GEORGIA AS TEMPERATURES WILL
FALL TO BELOW FREEZING NEAR MIDNIGHT THURSDAY NIGHT.

ALL INTEREST ACROSS NORTH AND CENTRAL GEORGIA SHOULD CONTINUE TO
MONITOR LATER FORECASTS AND REMAIN ALERT FOR THE POTENTIAL OF
WINTER WEATHER THURSDAY AFTERNOON AND EVENING ACROSS NORTH
GEORGIA...AND FOR THE POTENTIAL OF BLACK ICE ACROSS NORTH AND
PORTIONS OF CENTRAL GEORGIA THURSDAY NIGHT AND FRIDAY MORNING.

From meteorologist Allan Hoffman less than a minute ago:

It is nice to see the latest runs of the NAM, GFS, and ECMWF now all showing a simiilar scenario. By the way for those of you who cant see it, the ECMWF snow accumulation map is pretty similar to the NAM/GFS.

This is not a setup for your classic winter storm in these parts with antecedent cold air in place, a great storm track, cold high pressure over the Northeast. But it does look like a setup where a closed low will move across the Southeast and actually take on a negative tilt during the day tomorrow which should induce rapid cyclogenesis off the Southeast coast. As this happens a vigorus deformation band will set up which will put many areas of TN/NC/Va in an area of strong lift with cold air winning the battle.

This is not a recipe for a widespread major winter storm, but the odds are looking good that many in at least TN/NC/VA will see a period of snow.

http://www.daculaweather.com/4_hpc_extended_disco.php

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
114 AM EST WED JAN 16 2013

VALID 12Z SAT JAN 19 2013 - 12Z WED JAN 23 2013

BY THE END OF THE MEDIUM RANGE PERIOD THE RIDGE/TROUGH PATTERN
ACROSS THE CONUS MAY START TO BREAK DOWN. THE UPPER VORTEX OVER HUDSON BAY IS FORECAST TO LIFT TO THE NORTHEAST WHICH ALLOWS NORTHERN ENERGY TO RIDE THE NORTHWEST FLOW OUT OF CANADA THROUGH THE GREAT LAKES AND NORTHEAST... BRINGING IN THE COLDEST AIR OF THE WINTER TO MANY PLACES. THE MODELS AND ENSEMBLES REMAIN IN GOOD SYNOPTIC AGREEMENT AND HAVE FINALLY COME CLOSER TOGETHER ON THE TIMING/DEPTH OF THE ARCTIC AIRMASS EARLY NEXT WEEK. QPF POTENTIAL STILL LOOKS LIGHT OVERALL OUTSIDE THE FAVORED LAKE EFFECT AREAS INCLUDING UPSLOPE AREAS OF THE CENTRAL APPALACHIANS.

Also... the air next week will be cold, but not the coldest in several years. We have the rest of February for that! :-)
Here's a map of forecast temperatures next Tuesday morning
http://www.daculaweather.com/images/2013_01/23_wed_am_temp.jpg

Read the NWS Atlanta morning forecast discussion:
http://www.daculaweather.com/4_afd_ffc.php

From WXSouth.com moments ago:

"Just sent out an alert with the details and timing of the changeover to all my premium subscribers. I'll have extensive maps and hour by hour changeover graphics after the noon model runs.

In a nutshell this has trended to what WxSouth thought upper low climatology supports. The upper low holds intact and turns negative tilt running through Georgia and through the Eastern Carolina's and just offshore Virginia. This will place the comma head and best dynamic lift from extreme northern Ga, eastern TN , western NC and into northern and central NC to much of Virginia, where all those areas turn over to wet, heavy snow around dark. 2" per hour snow rates and thunder snow in some areas under excellent lift and dynamic cooling. Very bad news for trees and power lines."

But we're still OK down here, right?

Just for kicks...12z NAM extracted data snowfall totals for a few cities...

Huntsville, AL - 1.5"

Birmingham, AL - 4.1"

Chattanooga, TN - 3.1"

Crossville, TN - 4.5"

Knoxville, TN - 6.7"

Bristol, TN - 7.1"

Rome, GA - 3.1"

Gainesville, GA - 0.9"

Asheville, NC - 5.7"

Hickory, NC - 5.5"

Boone, NC - 10.9"

Charlotte, NC - 4.8"

Raleigh, NC - 3.9"

Atlanta GA, Athens GA, Greenville SC - ZIP

LOL!!! Snow flurries and a little black ice is not a winter weather event. This ain't south Florida.

We're now under a Winter Storm Watch

URGENT - WINTER WEATHER MESSAGE
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
244 PM EST WED JAN 16 2013

...WINTER STORM POSSIBLE ACROSS NORTH GEORGIA THURSDAY INTO
FRIDAY MORNING...

.A STALLED SURFACE FRONT THAT CONTINUES TO BRING WIDESPREAD RAIN
TO MOST OF NORTH AND CENTRAL GEORGIA IS EXPECTED TO SHIFT SOUTH
AS A COLD FRONT ON THURSDAY AFTERNOON. BEHIND THE FRONT...A COLD
POLAR AIRMASS WILL BEGIN TO SPREAD INTO GEORGIA. AT THE SURFACE...A LOW
BEGINS TO STRENGTHEN ACROSS EAST GEORGIA. AS THIS LOW TRACKS TO
THE NORTHEAST...WRAP AROUND MOISTURE SHOULD SWING INTO THE COLD
AIR MASS AND CAUSE THE RAIN TO CHANGE TO SNOW ACROSS NORTH GEORGIA
THURSDAY AFTERNOON INTO THURSDAY EVENING. THE HEAVIEST SNOWFALL SHOULD BE
IN THE NORTH GEORGIA MOUNTAINS.

This is a rapidly evolving system and more changes to come. More in an hour or so.
http://www.daculaweather.com/national_alerts/4_severe_alert.php

Tommy, possibly an inch here.

FRIDAY MORNING...

THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS ISSUED A
WINTER STORM WATCH...WHICH IS IN EFFECT FROM THURSDAY AFTERNOON
THROUGH FRIDAY MORNING.

• LOCATIONS...NORTH OF A LINE FROM CARROLLTON TO ATLANTA TO JEFFERSON.

• HAZARD TYPES...SNOW AND BLACK ICE.

• ACCUMULATIONS...2 TO 4 INCHES ACROSS THE NORTHEAST AND NORTHWEST
GEORGIA MOUNTAINS...ONE INCH OR LESS ACROSS THE REST OF THE
WATCH AREA.

• TIMING...SNOWFALL SHOULD BEGIN IN NORTHWEST GEORGIA BY MID
THURSDAY AFTERNOON...THEN THE REST OF NORTH GEORGIA THROUGH THE
LATE AFTERNOON AND EARLY EVENING HOURS.

• IMPACTS...LIGHT SNOWFALL ACCUMULATIONS UP TO ONE INCH ARE
POSSIBLE ON ROADWAYS ACROSS HIGHER ELEVATIONS IN THE MOUNTAINS.
BLACK ICE IS LIKELY ACROSS THE WATCH AREA THURSDAY NIGHT AND
FRIDAY MORNING WHEN TEMPERATURES FALL BELOW EVENING.

Rain will change over to snow in the afternoon tomorrow

From my buddy Larry just a minute ago:

"My guess for ATL-AHN northward (but below the mountains), largely based on the 0Z Wed. Euro, is that there will be a rain/snow (possibly also some IP) mix ~3-7 PM Thursday afternoon and possibly a period of almost pure snow (maybe with some IP) ~4-7 PM in heavier precip. Some accumulations of up to ~1" are possible on some elevated surfaces like bushes and maybe even on some grass if it falls at a heavy enough rate. IF tonight's 0Z Euro continues the colder trend, then things could get even more interesting for these areas, especially as regards accumulation potential as well as accumulations on more surfaces."

I've had people ask me if the ground is too warm for accumulations, and the answer is generally yes. That can change quickly if you happen to sit under a deformation band and snow falls at a high rate you can still get accumulation. Some of the snow is wasted as it cools the ground, but enough of it at once will do the job. Here's what aa meteorologist said today.

"In heavy wet snow situations such as this, ground temperature is more of an afterthought rather than a primary limiting factor for snowfall accumulation since heavy snowfall rates can easily overcome a warm ground temperature. "

Winter Storm Watches and Warnings are going up all across the south right now. You can get to all of them from here:
http://www.daculaweather.com/national_alerts/4_severe_alert.php

Also, this is one of my main maps at this point in the game http://www.daculaweather.com/4_spc_meso_analysis.php

I was going to explain the options that that could take several post on their own. But if you click on "Change Sector" near the top of the page, choose Conus, then go down a little and click on "Basic UA" and then 500 mb. 33You will see the upper level low over Texas. We're going to track this across the SE and see where she goes.

Another meteorologist just posted:

"This system is being underrated, yet all the maps I've seen suggest a really powerhouse storm. Do not underestimate the power of the ULL, mid-lapse rates, and snowfall rates!"

Smokin'

This is wonderful. Thank you. I have tried to follow weather at your main site but, frankly, since I know little, that first step is too large to make sense of it so I gave up. You are explaining things here. Very helpful.

I went looking at daculaweather.com for more systematic info on the SSW but I couldn't find it. Is it there and I couldn't figure it out? For now, I expect, your earlier post is good.

Also, although I will never be a weatherman, I am interested. I think right now, what I want most is a glossary of terms. What's a "Basic UA?" 12zNAM?

Meanwhile, I will get ready for the big chill...now where are my mucklucks?

Again, thanks.

drdata

Thanks Bob!

First the SSW stuff. Believe it or not Bob, there is not a lot of information short of research papers that I am aware of. I do have lots of links on my site under "Links" and "Weather Education" but one in particular is very good... http://www.theweatherprediction.com/ I don't know if SSW's are talked about there but it does have lots of good weather information.

Basic UA simply stands for Basic Upper Air .When you click on those links you see various levels of the atmosphere starting slightly above ground level at 925 mb on up to 300 mb or roughly 30,000 feet. There will be several "layers" we will be looking at now, 500 mb (~18,000 feet) and 850 mb (~5000 feet). You'll notice on both those maps that it has the temperatures at those levels also. Those will be very important for this storm because it's going to have to generate its own cold air and it's going to pull it from above in the upper levels of the atmosphere around 18,000 feet. That is what a dynamic system like this does, depending on the strength, they are capable of drawing a tremendous amount of cold air from those levels down to the surface.

12Z NAM - The NAM is a short range model or North American mesoscale model. It has a higher resolution that the long range models and it only goes out to 84 hours. The 12Z means it ran at 12Z (Greenwich Mean Time) or roughly 7am our time.

That link is excellent. Er...I will be back in a coupla months....

OK, maybe not...

You lapse into inside baseball--which is OK because it allows compacting a lot of info into a small space. I have jargoned, too.

OK, so 300MB equal, roughly, 30,000 feet...of elevation? That looks to me like 1 MB = 300 feet? If so, why does 500MB = 18,000 feet? See, there is something non-linear going on.

Ah...12 Z = 12 zulu. That I get. Don't know from mesoscale.

Meanwhile, this is a pretty neat event, isn't it?

drdata

Temps at the 850 mb level in the low are about -6º right now and about -14º at 500 mb. Those are the temps that this low can draw from and use to make it's own snowstorm.

If they'd let the blog posters have more room to type, I could give better explanations!

Birmingham AFD excerpt:
.DISCUSSION...

IT'S BEEN AWHILE FOR CENTRAL ALABAMA...IN FACT I BELIEVE THAT LAST
TIME ANYONE IN OUR CWA SAW SNOWFALL OF ANY GREAT SIGNIFICANCE
/SHY OF MOUNT CHEAHA/ WAS FEBRUARY OF 2011...ALMOST 2 YEARS
AGO...BUT THE LACK OF SNOW IS ABOUT TO COME TO AN END TOMORROW.

From James Spann over in Birmingham:

"A deep, cold core upper low will pass right over North-Central Alabama tomorrow, and should bring our first snow event of the winter to our state. Before I get into the details here, just a reminder… we don’t have very good skill at handling snow amounts, or placement, under one of these. Cold core upper low, weatherman’s woe. So, expect some surprises tomorrow as the event unfolds."

"If they'd let the blog posters have more room to type, I could give better explanations!"

Post on the full explanation on your site and link from here.

Will we have any snow in Northern Gwinnett County?

Lori... I'm watching the latest model run unfold right now. It's beginning to look more and more like snow will fall here. Models are showing the upper low staying together as a closed vortex much longer than they normally would in this situation. We may see an inch or so later tomorrow. Surprise!

Most if not all major media outlets will always play the conservative card when there are situations like this. They really look bad when they are wrong. Me on the other hand, don't care. :-) Seriously, I pass along the very latest weather information available. There aren't many places you can get that. What I pass along in terms of forecast is based on the opinions of multiple meteorologist and and various other resources. You don't have to wait on the next forecast update,

That being said... I can't promise snow tomorrow but I can tell you it's looking better and better each hour. Like i quoted James Spann above "Cold core upper low, weatherman’s woe" and that's what we have.

Consider what I give you to be raw data that you will hear first. Speaking that, my meteorologist friend Robert Gamble just release this:

*****MAJOR WINTER STORM TO IMPACT ALABAMA, GEORGIA, EAST TENNESSEE, NORTHERN SC, MOST OF NC AND SOUTHERN HALF VIRGINIA*******

Models trend colder, stronger, snowier, longer. A strong "bowling ball" type upper low, with cold air, longer duration than previously thought, and heavier axis of comma head snow, will aim at this region Thursday afternoon, night and early Friday. The upper low itself will provide snow and sleet through central and northern parts of Miss, Ala and Ga tomorrow but tomorrow night the precipitation EXPLODES quickly in most of western SC, central to west NC, eastern TN and southern VA. The atmosphere will cool off as all upper lows provide cold air and a crashing column when they're this strong. Rain will switch to snow and sleet suddenly then all snow, in all these areas."

... continued

" The heaviest snow looks to be as I have been pointing out for a while now, northern Georgia, eastern TN, and initially western NC and western, southwest Virginia, but spreading east across the Carolinas during the night. The way the axis sets up, the orientation of the "tilt" of the upper low, the most lift and dynamic cooling will occur much the same way March 2009 occurred..with all the Southern Apps receiving a 4 to 8 hour period of EXTREMELY heavy snow rates, which is much higher than the average Winter storm. Prepare now for power outages in east TN/ W NC/Central NC/sw VA/S VA, and scattered outages possible in northeast GA and Upstate SC. The storm will be short -lived, but very intense.
Trees will come down in some areas. Thundersnow will occur in some areas. Snow rates will be 2" per hour in some areas. Prepare now for suddenly changing weather beginning Thursday afternoon and reaching climax overnight Thursday night.-Robert, www.wxsouth.com";

Summary for the evening...

The models are forecasting a stronger cold core upper level low than was previously forecast. This increases the chance for winter precipitation in the north metro area for later tomorrow afternoon.

James Spann 10:31 PM - Public
Some points to consider before going to bed….

*As I have stated here in recent days, we have a limited skill set in dealing with snow output from cold core upper lows like this. No two systems act the same, and I can almost guarantee you there will be surprises. Some of you will get more snow than you expect, and others will see nothing more than a flake or two. There is very little skill in identifying the exact placement of the heaviest band of snow."

Good morning!
Stiil on track this morning for a winter weather event today. We are now under a Winter Weather Advisory while the mountains of north Georgia are under a Winter Storm Warning. Here's the latest from the NWS

URGENT - WINTER WEATHER MESSAGE...CORRECTED
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
338 AM EST THU JAN 17 2013

...SNOW EXPECTED ACROSS PORTIONS OF NORTH GEORGIA THIS AFTERNOON
AND TONIGHT...

.A STALLED SURFACE FRONT THAT CONTINUES TO BRING WIDESPREAD RAIN
TO MOST OF NORTH AND CENTRAL GEORGIA IS EXPECTED TO SHIFT SOUTH
AS A COLD FRONT THIS AFTERNOON. BEHIND THE FRONT...A COLD POLAR
AIRMASS WILL BEGIN TO SPREAD INTO GEORGIA. AT THE SURFACE... A LOW
WILL STRENGTHEN ACROSS EAST GEORGIA. AS THIS LOW TRACKS TO THE
NORTHEAST...WRAP AROUND MOISTURE WILL SWING INTO THE COLD AIR
MASS. RAIN WILL MIX WITH AND CHANGE OVER TO SNOW ACROSS PORTIONS
OF NORTH GEORGIA THIS AFTERNOON AND EVENING. THE HEAVIEST SNOWFALL WILL BE IN THE NORTHEAST GEORGIA MOUNTAINS.

...WINTER WEATHER ADVISORY IN EFFECT FROM 1 PM THIS AFTERNOON TO
7 AM EST FRIDAY...

THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS ISSUED A
WINTER WEATHER ADVISORY FOR LIGHT SNOW AND BLACK ICE...WHICH IS
IN EFFECT FROM 1 PM THIS AFTERNOON TO 7 AM EST FRIDAY. THE WINTER
STORM WATCH IS NO LONGER IN EFFECT.

• LOCATIONS...NORTH OF A LINE FROM CARROLLTON TO ATLANTA TO
JEFFERSON...AND SOUTH OF A ROME TO HIAWASSEE LINE.

• HAZARD TYPES...LIGHT SNOW AND BLACK ICE.

• ACCUMULATIONS...LESS THAN 1 INCH OF SNOW ON GRASSY AND ELEVATED
SURFACES.

• TIMING...RAIN WILL MIX WITH AND BEGIN CHANGING TO SNOW IN
NORTHWEST GEORGIA BY EARLY AFTERNOON...SPREADING ACROSS THE REST
OF NORTH GEORGIA THROUGH THE EARLY EVENING HOURS.

• IMPACTS...SNOWFALL CREATING NUISANCE DRIVING CONDITIONS. BLACK
ICE IS LIKELY ACROSS THE AREA TONIGHT AND FRIDAY MORNING WHEN
TEMPERATURES FALL BELOW FREEZING.

• WINDS...NORTHWEST 10 TO 20 MPH WITH GUSTS UP TO 30 MPH.

• TEMPERATURES...IN THE MID 40S THIS MORNING DROPPING TO THE LOWER
30S BY MIDNIGHT.

Atlanta NWS had a long AFD this morning
http://www.daculaweather.com/4_afd_ffc.php

...WINTER STORM WARNING IN EFFECT FROM 10 AM THIS MORNING TO 7 AM
EST FRIDAY...

THE NATIONAL WEATHER SERVICE IN PEACHTREE CITY HAS ISSUED A
WINTER STORM WARNING FOR HEAVY SNOW AND BLACK ICE...WHICH IS IN
EFFECT FROM 10 AM THIS MORNING TO 7 AM EST FRIDAY. THE WINTER
STORM WATCH IS NO LONGER IN EFFECT.

* LOCATIONS...NORTH OF A LINE FROM ROME TO HIAWASSEE.

* HAZARD TYPES...SNOW AND BLACK ICE.

* ACCUMULATIONS...1 TO 3 INCHES OF SNOW...WITH UP TO 4 INCHES
POSSIBLE AT HIGHER ELEVATIONS.

* TIMING...RAIN WILL MIX WITH AND BEGIN CHANGING TO SNOW IN
NORTHWEST GEORGIA BY EARLY AFTERNOON...SPREADING ACROSS THE REST
OF EXTREME NORTH GEORGIA THROUGH THE EARLY EVENING HOURS.

* IMPACTS...SNOWFALL CREATING HAZARDOUS DRIVING CONDITIONS. IN
ADDITION...BLACK ICE IS LIKELY ACROSS THE WATCH AREA TONIGHT AND
FRIDAY MORNING WHEN TEMPERATURES FALL BELOW FREEZING.

* WINDS...NORTH 10 TO 20 MPH WITH GUSTS UP TO 35 MPH.

* TEMPERATURES...IN THE MID 40S THIS MORNING DROPPING TO NEAR 30 BY
MIDNIGHT.

A little more about this system from my buddy Robert Gamble at WXSouth.com

"GFS looks almost identical to NAM tonight at 5H. Have folks forgot what strong upper lows do on this track? This is one exquisite track for changing rain to snow suddenly along and northwest of it's track. Hi Res NAM leads the way , and should be the model of choice, as it was in the previous 2 upper lows last Fall, when GFS and ECMWF joined late. The details here mean a lot, and upper lows are best portrayed by high res models. The column crashes with the upper low as it moves east then northeast, along I-85 from Atlanta to Charlotte to Raleigh ( notice GFS now is close to Elizabeth City now). NAM has led the way the entire time on this event, as much as I hate to admit.

GFS looks much like NAM maybe shorter lived by a fraction, but remember deformation bands die a slow death in the lee of the Apps. I've seen it a few times and upper lows are kind of my specialty, and damming."

... continued

"This will be a very remarkable event, once the upper low wraps the precip around its core , beginning in Alabama, then stretching in a very nice deformation axis from Richmond to just north of Atlanta tomorrow night. The Carolina peeps should be in hog heaven with this track, despite marginal 850's. Dynamic forcing through the roof for 4 to 6 hours under that band, and some areas more, namely southern VA and western NC mtns, eastern TN where cold is first to arrive. But the absolute best lift, tilt and forcing from being on the northwest side is just north of Atlanta, through the western Carolinas into southern VA and that all slides east overnight....only slowly weakening aloft, which is usually overdone some. Thunder and lightning on the nw shield as well, which will make some insane rates for some areas. Hard to say exactly where that ends up, but it will certainly happen. "

... continued

"Unfortunately, the downslope may cause a warm bubble too, but that's hard to predict in the lee as well. Overall, this will go down as one of the best Upper Low type storms from northern Alabama through much of the Carolinas and southern Virginia I think, and could approach the March 2009 system in some areas, but that's hard to say exactly where. This one looks faster than that, and that could save many folks , but still when you get 2" per hour or even 3" per hour under the convection, you'll see firsthand what can happen with upper lows. After the fourth hour, the trees start really creaking and making scary noises. Let's hope it doesn't come to that."
"

Just need enough for my kids to have a snowball fight and a 4 day weekend!

Not sure about a 4 days weekend but very posy a delay on Friday morning. I work for GCPS so I'm cheering for it too! :-)

My1st graders students will be doing the snow dance this afternoon (along with many teachers!)

I'll be right there with them Julie! I do keep our teachers and staff informed at work and when I'm walking down the hall I see little dances from people too!

The bowling ball upper level low is currently centered over Arkansas, Louisiana, and western Mississippi with a core temperature of -24º. Those temperatures at 18,000 feet and lower, will be drawn down toward the surface by the storm. causing heights to crash and in turn, causing snow. The area forecast discussion by Atlanta this morning was excellent (I've got to find out who TDP is) in describing how this process will occur. Please keep in mind, and I can't stress this enough, this is a very dynamic system, one that it literally making it's own snow storm. Because of the dynamics, it is next to impossible to tell EXACTLY where any snow may fall or how much, this is not your typical SE snow storm. Read what I posted this morning, it describes in great detail, and from several points of view, how this may play out. It won't take much, one way or the other to have dramatic effects. At this point it's a NOWCast type of event, much like what we had back on January 9th, 2010. It's hour by hour, and as it gets closer, minute by minute.

Do what the meteorologist are doing... cross your fingers.;-)

I hate these systems. Gwinnett always falls on the wrong side. I remember the March '09 storm where it rained at my house, snowed like crazy in Bethlehem, Roswell, and buried my farm in Madison County with over a foot of snow. We got a few flakes here in Braselton before it quit. This one will most certainly behave the same way. It also stinks, because even if it does snow, as soon as the low moves on it warms up and melts within a few hours. I would imagine the NWS sees that too, hence the downgrade to an "advisory". At least we certainly need the rain.

And, by the way, for grins I checked out weather underground this morning. They say 64 next Saturday. LOL

You are absolutely correct Tommy. Right now the models have north Georgia in a warm bubble this afternoon and that may limit the snow potential. The track of the low and when it begins it's turn NE will decide our fate.

I'm thinking the low will travel too far to the north for decent snowfall here.

Could we have some light snow? Maybe on grassy surfaces?

Oh yes, not saying it NOT going to snow... it most likely will. But if the low moves much further north it would be much quicker and lighter.

Snowing over 2/3's of Alabama right now...

Thank you! I'm from South Florida and haven't seen much snow before. What time frame do you think for Gwinnett County?

Right now I'm thinking around 6-7pm, that may change. Watch this radar loop for signs of snow. This is Dual Pol data from the Atlanta NWS radar in Peachtree City. This particular loop can distinguish between rain and snow and ice. Light blue is dry snow, dark blue is wet snow, and pink is ice.
http://www.daculaweather.com/grlevel4/4_ffc_hhc.php

Also, here's what the Birmingham image looks like right now
http://www.daculaweather.com/images/2013_01/bmx_snow.png

Temperatures falling at 6º/hr here now and currently at our low for the day.

Down to 43º F here and falling at more than 6º/hour.

The Winter Storm Warning is creeping south toward us.
.FFC WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING UNTIL 7 AM EST FRIDAY FOR THE FOLLOWING
ZONES: BARTOW...CATOOSA...CHATTOOGA...CHEROKEE...DADE...DAWSON...
FANNIN...FLOYD...GILMER...GORDON...LUMPKIN...MURRAY...PICKENS...
TOWNS...UNION...WALKER...WHITE...WHITFIELD.

IN GENERAL...EXPECT 2-4 INCHES OF SNOW...WITH ISOLATED AMOUNTS UP TO 5 ACROSS FAR NORTH GEORGIA...AND SMALLER AMOUNTS ACROSS THE NORTH METRO
AREA.

MAIN AREA OF RAIN SHOWERS ON ITS WAY INTO THE CAROLINAS THIS
AFTERNOON...AND AREA OF WINTER PRECIP ASSOCIATED WITH UPPER LOW
EXPECTED TO PASS OVER NORTH GEORGIA TONIGHT. WINTER PRECIP IS
GENERALLY EXPECTED NORTH OF A HAMILTON TO WASHINGTON LINE...BUT
ACCUMULATIONS SHOULD BE LIMITED TO A LINE NORTH OF CARROLLTON TO
ATLANTA TO JEFFERSON. IN GENERALLY...EXPECT 2-4 INCHES OF
SNOW...WITH ISOLATED AMOUNTS UP TO 5 ACROSS FAR NORTH GEORGIA...AND
SMALLER AMOUNTS ACROSS THE NORTH METRO AREA. EXPECT INITIAL
PRECIPITATION TO BE A MIX OF RAIN AND SNOW...THEN TRANSITIONING TO A
WET SNOW. WARM SURFACE TEMPERATURES SHOULD KEEP ACCUMULATIONS
LIMITED AT FIRST...BUT CONVECTIVE NATURE OF THE PRECIP SHOULD
OVERCOME THE WARM SURFACE TEMPERATURES. EXPECTING HEAVIEST SNOWFALL
OVER FAR NORTHEAST GEORGIA WHERE BANDING AND POTENTIAL TERRAIN
ENHANCEMENT WITH THE WIND TRAJECTORY ARE EXPECTED TO INCREASE
SNOWFALL TO THE ISOLATED 5 INCH AMOUNT.

Gwinnett is right on the line for 2-4". Wouldn't take much to get us a decent little snow at this point.

Yes, I said that, and yes, we were going to be... and still might be. But the NWS has been bumping up accumulations this afternoon so the potential exists for some minor accumulations here. Wouldn't surprise me to see some flakes in a little while.

This afternoon when I was outside around 3pm, we had some very light snow flakes flying around.

A little snow reported in Villa Rica a few minutes ago.

FWIW, with all this rain, Lake Lanier is up a bit over 2' since 1/1/13 and over 4' in the last month.

http://lanier.uslakes.info/Level.asp

Guys... I hate to say it, but it's not looking good for us. There are small bands of precipitation moving in but it is light and diminishing in coverage. There are some wet flakes mixed in and you may get all snow for a little while. Here's an image of where the upper low is now. You'll see how we missed the mark.
http://www.daculaweather.com/images/2013_01/500mb_low.png

Yea, it just looks wet and soggy here! Nothing pretty and white!

The moon and stars are never as pretty, nor the skies so clear as when some form of winter weather alert is issued. LOL Really is nice to see them. Another big swing and a miss. Does this mean we are in store for those mid-60's next weekend?

No, we missed the mark. From the beginning it didn't appear that much would happen here. It went back and forth yesterday, but once it started to lift north we were doomed. The mountains killed any wrap-around moisture on the backside of the storm. Again, it's all about the track, in the winter here in Atlanta, we need the low to track along the Gulf coast in order to get a snow storm here and this one went directly over us. We were hoping for better dynamics over our area but as the upper low moved over the 850 mb temps actually warmed. We lost the dynamics and North Carolina got slammed with thundersnow. Of course.

As far as the upcoming weather...

EXTENDED FORECAST DISCUSSION
NWS HYDROMETEOROLOGICAL PREDICTION CENTER COLLEGE PARK MD
155 AM EST FRI JAN 18 2013

VALID 12Z MON JAN 21 2013 - 12Z FRI JAN 25 2013

NEXT WEEK BEGINS WITH QUITE AN AMPLIFIED PATTERN FOR THE NATION
HIGHLIGHTED BY STABLE MID-UPPER LEVEL WEST COAST RIDGING AND A
WELL CARVED AND QUITE COLD DOWNSTREAM EAST-CENTRAL MID-UPPER LEVEL TROUGH. IT DOES NOT LAST.
THE PATTERN BREAKS DOWN SURPRISINGLY QUICKLY BY GUIDANCE AS PROGRESSIVE ERN PACIFIC TROUGH ENERGY/WEATHER CRASHES INLAND THROUGH THE WRN US RIDGE POSITION BY MIDWEEK AND SUBSEQUENTLY ACTS TO SIGNIFICANTLY WARM LEAD DOWNSTREAM CENTRAL TO ERN US TEMPS AND ALLOW EVENTUAL INCREASE OF MOISTURE AVAILABILITY AND WIDESPREAD/ORGANIZED PCPN POTENTIAL...ALBEIT A WEEK AWAY.

From Robert Gamble about what went wrong down here:

"Basically, the cold was too thin for that area, and too late to arrive, and the upper low was speeding up, which further reduced the already short window of opportunity there. Without cold air firmly in place, it's always a risky proposition that many times won't work out right."

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
639 AM EST FRI JAN 18 2013

...ISOLATED PATCHY BLACK ICE POSSIBLE ACROSS PORTIONS OF NORTH
GEORGIA THIS MORNING...

SOME ISOLATED SPOTS OF PATCHY BLACK ICE...MAINLY ON BRIDGES AND
OVERPASSES ARE POSSIBLE THIS MORNING ACROSS PORTIONS OF NORTH
GEORGIA. MOTORISTS SHOULD SLOW DOWN AND PROCEED WITH CAUTION.

Here's a summary of the winter storm. It also list snowfall amounts so you can see where the snow actually fell.

http://www.daculaweather.com/4_hpc_winter_storm_summary.php

Tommy , the models are showing a quick shot of arctic air this weekend after a warm up Fri/Sat. After that, the high moves out to sea in a more zonal flow. Right now the blocking is just not in place to produce a prolonged cold outbreak. The models are are showing a breakdown of the Pacific ridge which would allow warm and moist Pacific air back into the picture.

I think we'll see intermittent shots of cold air until/if ridging can get established. February is still looking below normal in the long range CFSv2 models.

So basically, all that talk they were doing last week about a split in the polar vortex and a lot of cold air was simply BS trying to fill in an otherwise boring weather news week? Appears again to be a winter that wasn't. And you were exactly right when you were saying the type "storm" they were predicting yesterday never works out. I'm good with that. I've seen enough snow this year already.

Not really. The strat warming has brought about changes, the extent of the changes are still to be seen. I'll have a new post tonight about the longer range outlook.

A quote from meteorologist Allan Hoffman today. Allan graciously allows me to display his model images on DaculaWeather.com. Allan works for the Raleigh Examiner and is very knowledgeable about southeast weather.

"The ensemble guidance wants to pop a –EPO ridge into the Gulf of Alaska and build it into western North America as that week progresses, which should progress the trough out, and at the same time we see continued positive height anomalies over the poles (blocking). The ensembles are in pretty good agreement today that the trough will move into the Plains/Midwest by 1/29-1/30 and cover much of the eastern half of the nation by 1/31 into early February. The look of the ensembles is pretty cold late in the 11-15 day period. We see a –AO, a –NAO, and a ridge over the west coast of North America. This sets up the polar vortex over Hudson Bay and a cold pattern across much of the eastern half of the nation. This is supported by the latest CFS and ECMWF weekly forecasts which keep a cold pattern through mid-February. So perhaps there will be more snow chances for many of us in the month of February."

Great image of where the snow did fall
http://www.daculaweather.com//images/2013_01/snow_google.jpg

From another meteorologist friend. Jason lives in Dahlonega and said this around 8am this morning:

"For the GA peeps I have a clear view of Woody Gap (3,300 ft), Blood Mountain (4,000 ft) and the mountains north of Helen GA. I see no snow anywhere."