Jump to content
  • Forum Image
NorthGeorgiaWX

Wednesday, February 19

Recommended Posts

Good morning!

Lingering showers are the forecast for this morning as the front slowly sags south. To the north colder ir and to the south, it is much warmer. The battle line has been drawn.

Snap346063843.thumb.png.f5e9b40845ababaf12e329319e461edd.png

 

Let's get right to the chances for a few people seeing some snow. 

First, the NWS Atlanta thoughts.

Quote

The other forecast note of interest on Thursday will be wintry
precipitation potential in parts of far north Georgia.
Precipitation will be ongoing as an upper shortwave trough sweeps
southward toward the Tennessee Valley and Appalachians. With cold
air advection, temperature profiles would support a rain/snow mix or
transition to light snow across primarily the higher elevations
of far north Georgia by midday Thursday into Thursday afternoon
.
While some valley locations could see a mix or brief transition
to snow, surface temperatures appear marginal for much/any
accumulation outside of the
higher elevations where an inch or
perhaps as high as the 2" range would be possible before
precipitation comes to a quick end Thursday evening.

 

The WPC has the northeast corner of the state as the area with the highest probability of seeing accumulating snow. 

Snap346063844.png.99f19b0302ee27ab71ccf22df6869e5c.png

 

For a minute, let's assume the NAM 3km is somewhat correct in its depiction of the actual event. 

Rain would start changing over to freezing rain starting around 6-7 AM tomorrow for the higher elevations. The precip would be very light with some of it not reaching the ground initially. 
nam-nest-conus-atlanta-instant_ptype_3hr-2200000.thumb.png.ab352c8fe210f5f0dcf140569c2cd610.png

 

The pink areas are below freezing, and as you can see, much of the area is at or above freezing with a cold rain falling.
nam-nest-conus-atlanta-t2m_f-2200000.thumb.png.38195dcb76bb3759ab7a1cd568bbb5d5.png

 

This continues for a couple more hours. Initially temperatures drop due to evaporational cooling, but by now, the atmosphere is saturated and the dewpoint depressions point that out. Evaporational cooling won't help at this point.

nam-nest-conus-atlanta-instant_ptype_3hr-2210800.thumb.png.c8118fd66b5aba7f5e633ff1045f3aba.png

nam-nest-conus-atlanta-t2m_f-2210800.thumb.png.b4779d97e59d4870f52434e8f5f18040.png

nam-nest-conus-atlanta-dpt_dep-2210800.thumb.png.f3b1e7f30c0cb0d22efc8816e76c8759.png

 

Keep in mind that the NAM temperatures have warmed since the previous run... trend or not? We'll see. 

nam-nest-conus-atlanta-t2m_f_dprog-1940800.thumb.png.4f0c532651430f461e94f3ea6e1018ed.png

 

But to me, the profile temperatures are just so marginal while the precip is around that I find it hard to see how most people will see any appreciable snow. Once again, this is the NAM at the 850 mb level. It's critical that this area be below freezing and you can see that for much of the period when the moisture is around. These loops are from 1 AM Thursday through 1 PM Friday.

nam-nest-conus-atlanta-t850-1582092000-1582156800-1582308000-80.thumb.gif.1734de46cb84a32dc30a0e03b6a2e108.gif

 

Further down at 925 mb (about 2500 feet) we see these temperatures for the same time period. 

nam-nest-conus-atlanta-t925-1582092000-1582178400-1582308000-80.thumb.gif.ebe81658190e223d435fb44e59fef86a.gif

 

For those reasons, this is the "official" NW forecast for snow. 

THIS IS A FORECAST 🙂 

ndfd-conus-atlanta-total_snow_10to1-2264800.thumb.png.4a62d118fc195627c437a32ad8bf7a36.png

 

Th NAM is overdone with the snow amounts in my opinion and the impacts will not be as great as the NAM snow image would suggest.

NOT A FORECAST

827025615_nam-nest-conus-atlanta-total_snow_10to1-2264800(1).thumb.png.54d0898ab18423f0426b9c07e34f68f3.png

 

Right now the road and soil temps are too warm for anything to freeze without a prolonged below freezing period. Snow may accumulate on elevated surfaces and of course bridges and overpasses, so be cautious if you're out driving in it. 

Road Temperatures

Snap346063846.thumb.png.37419f859a27f3608163f6479ec6aebd.png

 

Soil Temperatures

t5.png.e5de691710081bb27fe1f71408e9c011.png

 

There could be some freezing on the roadways from runoff later in the day and Thursday evening. After all this rain, water is still running across roadways and temperatures will get very cold Thursday night. See how that most of the below freezing temperatures during the day are confined to the higher elevations in the mountains. 

nam-nest-conus-atlanta-t2m_f-1582092000-1582178400-1582308000-80.thumb.gif.2b7f895b79bc66032681832b43e2a261.gif

 

So that's it. I do not think we'll see what we saw last time, I just don't believe the temperatures support that happening again. 

We'll be following this throughout the day, so please keep checking back, you never know what might happen!
Have a great day!

ffc-19.png.12231fd9dd1b8390e7a83598cfff01bd.pngmrx-19.png.e9a8ec48057e49853deae7a102ddff67.pngbmx-19.png.cca15f6112cb19eff7643239e6d73bea.png

 

 

 

 

 

nam-nest-conus-atlanta-frzr_total-2264800.png

nam-nest-conus-atlanta-total_snow_10to1-1582092000-1582178400-1582308000-80.gif

  • Like 4

Share this post


Link to post
Share on other sites

Guess we'll have to hang our hopes on that fellow with the "blizzard" forecast, eh?

 

:classic_laugh:

  • Haha 2

Share this post


Link to post
Share on other sites
11 minutes ago, Tanith said:

Guess we'll have to hang our hopes on that fellow with the "blizzard" forecast, eh?

 

:classic_laugh:

His time period is still coming up. 🙂 We'll see. 

I hope this system overperforms like the last one we had, but I'm just not sure that it has what it takes to do so. 

  • Like 1

Share this post


Link to post
Share on other sites

Robert at WXSOUTH just sent out an update via Facebook and seems even the 85 corridor could flash over to heavy sleet or wet snow tomorrow due to the cold and dryer air aloft working down the Appalachians (think a wedge situation). Interesting at the least.

  • Like 1

Share this post


Link to post
Share on other sites
21 minutes ago, Shannon said:

Robert at WXSOUTH just sent out an update via Facebook and seems even the 85 corridor could flash over to heavy sleet or wet snow tomorrow due to the cold and dryer air aloft working down the Appalachians (think a wedge situation). Interesting at the least.

🙂 I saw that. I don't think that will extend too far this way though. Toward the end of the 06z NM you could see a little lingering snow along I-85, so some may fall, but it will be a little too late to make much difference.

  • Like 1

Share this post


Link to post
Share on other sites

I've known Robert for a long time. I actually had the pleasure of helping him get his first paid site up and running. He's a great meteorologist and a great guy! 🙂

Share this post


Link to post
Share on other sites

HRRR is looking like primarily a mountain event and very marginal temperatures there. An inch or higher is unfortunately probably going to be reserved for areas over 2,500-3,000'.

  • Like 1

Share this post


Link to post
Share on other sites
Just now, Preston said:

HRRR is looking like primarily a mountain event and very marginal temperatures there. An inch or higher is unfortunately probably going to be reserved for areas over 2,500-3,000'.

My thoughts as well, and that's why I haven't been really fired up about it. You should get lucky though!

Share this post


Link to post
Share on other sites

I adore a snow day, just dread the potential for panicked school pickups in unexpected snow 😅😅 but that’s why I follow you now instead of local news! 

  • Like 1

Share this post


Link to post
Share on other sites

At times we have talked about evaporative cooling taking place on other systems where temps were 6-8 *above freezing.  This system over and over you have said , or at least that is what I heard, that temps will stay above despite heavy snowfall rates ( wet snow) Can you explain why at 39, you would began to get a rain snow mix to a heavy wet snow why it wouldn’t pull the temp the rest of the way down and get accumulating snow on grass at least?

  • Like 1

Share this post


Link to post
Share on other sites

First time poster, long time follower.  Love the site!  Quick question, why does the NAM continue to show so much snowfall so deep into GA?  It does not line up with the rest of the output.

  • Like 1

Share this post


Link to post
Share on other sites
28 minutes ago, AaronW said:

First time poster, long time follower.  Love the site!  Quick question, why does the NAM continue to show so much snowfall so deep into GA?  It does not line up with the rest of the output.

I know what you are talking about I believe. On TropicalTidBits it seems the output on the NAM is a little off. It seems to count anything falling from the sky as snow if its around 35 degrees or cooler and therefore you have the skewed snowfall maps.

  • Like 1

Share this post


Link to post
Share on other sites

We are looking to make a day trip from Murphy to Atlanta and back, tomorrow. Should we be concerned? 

Share this post


Link to post
Share on other sites
53 minutes ago, RickyD said:

At times we have talked about evaporative cooling taking place on other systems where temps were 6-8 *above freezing.  This system over and over you have said , or at least that is what I heard, that temps will stay above despite heavy snowfall rates ( wet snow) Can you explain why at 39, you would began to get a rain snow mix to a heavy wet snow why it wouldn’t pull the temp the rest of the way down and get accumulating snow on grass at least?

Depending on how dry/moist the atmosphere is will partially determine how much evaporative cooling will work. 
Let's say it's 35 degrees and the dew point is 25. You might get heavy enough precip to bring that 35 down to 30 and the dew point up to ~30. 
Some people will get snow on the grass when they are above freezing IF it comes down hard enough. The snow rate just has to overwhelm the melting rate. It takes a little while to drop the ground temps cold enough to allow the snow to overcome the heat. 

 

33 minutes ago, AaronW said:

First time poster, long time follower.  Love the site!  Quick question, why does the NAM continue to show so much snowfall so deep into GA?  It does not line up with the rest of the output.

Welcome!
The NAM is known to have a bias for over amplification. When you're talking about snow amounts that are associated with such tiny liquid precipitation amounts, it doesn't take much more liquid precip to get a bump up in snow totals. The other reason is that the NAM is/was thinking there will be colder temperatures than some of the other models.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Who's Online   0 Members, 0 Anonymous, 12 Guests (See full list)

    There are no registered users currently online



×
×
  • Create New...