Jump to content
  • Forum Image
NorthGeorgiaWX

Potential Winter Threat - December 6-11

Recommended Posts

Question.... how reliable is the WRF-ARW and the WRF-ARW short range models. Are they used by the NWS and it reliable to them. Cause that 12z run was very cold and well interesting 

Share this post


Link to post
Share on other sites

This blurb from latest GSP discussion is what I am talking about.

Deeper moisture will then return with profiles steadily saturating
through Saturday and upglide developing as the southern tier surface
low works eastward along the Gulf Coast. The deeper layer Q-vector
convergence with the upper forcing will arrive toward evening. As
the profiles wet bulb down, there should be a lot of isothermal near
zero profiles evident, and the concern exists for frozen ptypes to
impact more of the forecast area and sooner. Will trend PoPs up a
bit faster, add more QPF for the afternoon hours, and increase the
snow accums over mountain sections a bit sooner. This may require
moving the current hazard products up a bit, perhaps as early as
Noon for the existing warning.

Temps wetbulbing downward earlier than expected in the morning, and changing to mix or snow quicker. At that point falling snow, especially at heavy rates, can make warming at the surface harder. then a fairly stout near surface SE flow, up to around 925 millibars, will blow in  colder dryer air also cooled by snow in NC. And if dewpoints keep falling then temps will keep wetbulbing down. Now this is the perfect scenario and may not happen, but NWS is suggesting that it may.

  • Like 2

Share this post


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

Question.... how reliable is the WRF-ARW and the WRF-ARW short range models. Are they used by the NWS and it reliable to them. Cause that 12z run was very cold and well interesting 

Guess you're talking about this? 

wrf_ref_arw_se_49-07.png

Share this post


Link to post
Share on other sites
2 minutes ago, NorthGeorgiaWX said:

Guess you're talking about this? 

wrf_ref_arw_se_49-07.png

Ugh yes. Down to 29-30 degrees in Gwinnett if taken verbatim and not to mention a decent amount of precip incoming. Ultimately just wanted to know if it’s a reliable or useful tool used by the NWS.

Edited by Shannon

Share this post


Link to post
Share on other sites

Allan's latest thinking.

<blockquote class="twitter-tweet" data-lang="en"><p lang="en" dir="ltr">My updated forecast. Again subject to change and if need be I will make another update tomorrow pm. <a href="https://twitter.com/hashtag/ncwx?src=hash&amp;ref_src=twsrc%5Etfw">#ncwx</a> <a href="https://twitter.com/hashtag/scwx?src=hash&amp;ref_src=twsrc%5Etfw">#scwx</a> <a href="https://twitter.com/hashtag/vawx?src=hash&amp;ref_src=twsrc%5Etfw">#vawx</a> <a href="https://t.co/gm4x4oeh2D">pic.twitter.com/gm4x4oeh2D</a></p>&mdash; Allan Huffman (@RaleighWx) <a href="https://twitter.com/RaleighWx/status/1071117371224571904?ref_src=twsrc%5Etfw">December 7, 2018</a></blockquote>
<script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>

Edited by KingOfTheMountains

Share this post


Link to post
Share on other sites
4 minutes ago, KingOfTheMountains said:

This blurb from latest GSP discussion is what I am talking about.


Deeper moisture will then return with profiles steadily saturating
through Saturday and upglide developing as the southern tier surface
low works eastward along the Gulf Coast. The deeper layer Q-vector
convergence with the upper forcing will arrive toward evening. As
the profiles wet bulb down, there should be a lot of isothermal near
zero profiles evident, and the concern exists for frozen ptypes to
impact more of the forecast area and sooner. Will trend PoPs up a
bit faster, add more QPF for the afternoon hours, and increase the
snow accums over mountain sections a bit sooner. This may require
moving the current hazard products up a bit, perhaps as early as
Noon for the existing warning.

Temps wetbulbing downward earlier than expected in the morning, and changing to mix or snow quicker. At that point falling snow, especially at heavy rates, can make warming at the surface harder. then a fairly stout near surface SE flow, up to around 925 millibars, will blow in  colder dryer air also cooled by snow in NC. And if dewpoints keep falling then temps will keep wetbulbing down. Now this is the perfect scenario and may not happen, but NWS is suggesting that it may.

Really great pints here. Earlier snowfall leads to colder air at the surface funneling down here. 

Share this post


Link to post
Share on other sites

Think I should be worried about travelling up 75 (285 to Pickens County) Sunday afternoon? I'm not liking what I'm seeing. State of Georgia is saying they have enough brine to ensure the roads are safe, but the last time I heard that I got stuck on 75 for 11 hours lol. 

Share this post


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

Question.... how reliable is the WRF-ARW and the WRF-ARW short range models. Are they used by the NWS and it reliable to them. Cause that 12z run was very cold and well interesting 

And herein lies the problem. EVERY model has a slightly different solution, not one is exactly the same as another one. So what do you do? 

Have to dig a little further. Which one is initializing the best? While no guarantee, it's helpful to know which model currently has the best grasp of the setup and what's currently going on. 

 

  • Haha 2

Share this post


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

Ugh yes. Down to 29-30 degrees in Gwinnett if taken verbatim and not to mention a decent amount of precip incoming. Ultimately just wanted to know if it’s a reliable or useful tool used by the NWS.

Oh yes. Useful and as reliable as any of the short range models. It's going to be very, very close. 

Share this post


Link to post
Share on other sites
4 minutes ago, KingOfTheMountains said:

Hmm don’t know why that didn’t work the first time, but Allan Huffmans latest thinking.

 

Yes, I saw that a few minutes ago. I like Allan and have followed him for a long time. Many years ago before he moved his models to the AMWX forum, he use to let me post his model images on my site. 🙂

  • Like 2

Share this post


Link to post
Share on other sites
1 minute ago, NorthGeorgiaWX said:

Oh yes. Useful and as reliable as any of the short range models. It's going to be very, very close. 

That’s why I was asking. I thought I have seen the NWS using it especially when you read their discussions. Wonder if they mention it in there afternoon briefing...

Share this post


Link to post
Share on other sites
7 minutes ago, KingOfTheMountains said:

Hmm don’t know why that didn’t work the first time, but Allan Huffmans latest thinking.

 

LOL I'm literally 30 minutes driving time to B,C,D, and E. UGH THIS IS KILLING ME 

  • Haha 1

Share this post


Link to post
Share on other sites
2 minutes ago, NorthGeorgiaWX said:

Yes, I saw that a few minutes ago. I like Allan and have followed him for a long time. Many years ago before he moved his models to the AMWX forum, he use to let me post his model images on my site. 🙂

Yeah he has been a must follow for weather in the South in my opinion along with Robert at WxSouth of course. And I'd certainly love to pick his brain on this one. 

  • Like 1

Share this post


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

Yeah he has been a must follow for weather in the South in my opinion along with Robert at WxSouth of course. And I'd certainly love to pick his brain on this one. 

I helped Robert get started on his first paid site. 🙂

  • Like 2

Share this post


Link to post
Share on other sites

I see the same thing happening on this storm that happened on Florence.  The meteorologists are not believing the models.  Interesting.  I can understand not believing big snow totals.

  • Like 1

Share this post


Link to post
Share on other sites

Can we expect the NWS ATL update before their briefing at 4pm?

Share this post


Link to post
Share on other sites
1 hour ago, rwarren5 said:

I'm running two monitors at work. One is dedicated to being productive, the other is 5 tabs of weather related nonsense 🤣

This was me yesterday— TOTALLY relatable!! 😆

  • Like 1
  • Haha 2

Share this post


Link to post
Share on other sites
1 minute ago, HaireFam said:

This was me yesterday— TOTALLY relatable!! 😆

Same and I’m a teacher! Brought my personal computer just for this😂

  • Like 1
  • Haha 3

Share this post


Link to post
Share on other sites
6 minutes ago, SlicNic13 said:

Can we expect the NWS ATL update before their briefing at 4pm?

Probably nothing until then. I'm sure they are busting butt trying to figure stuff out. Lots of VERY smart people working on this. 

  • Like 2

Share this post


Link to post
Share on other sites

Latest in the new NWS Atlanta AFD

Quote

SHORT TERM /Tonight through Saturday Night/...

A strengthening storm system will gradually track from Texas to the
Lower Mississippi Valley and eventually the Southeast/Southern
Appalachians over the weekend with a series of upper level
disturbances maintaining inclement weather across north & central
Georgia into early next week.

Here are a few of the forecast challenges with this package:

1. Duration, locations and amounts of wintry precipitation across
northeast Georgia Saturday night into Sunday. **See below for
further discussion on this**

2. Heavy rain Saturday into Sunday that could lead to river/stream
flooding. Confidence is high that this will occur.

3. Strong easterly winds late Saturday through Sunday morning.

4. Mix of rain/snow showers Sunday night into Monday with locally
heavy snow possible in the northern mountains.

Starting with #1... both the NAM and ECMWF continue to show an area
of sleet/snow/freezing rain developing late Saturday across the
higher elevations of northeast GA. Into Saturday night as the colder
low lvl air aided by the "wedge" becomes reinforced, this area of
wintry precip is expected to expand south/west int the typical
"wedge zone" (Hall/Jackson/Madison/Banks/northern Gwinnett & Barrow
counties). Model soundings from Blairsville (Union Co.) to
Gainesville show temperature profiles supportive of any and all
wintry p-types (snow/sleet/freezing) from late Saturday through
Sunday, so trying to figure out what p-type and how much is
extremely challenging at this point. Also, there is still some
uncertainty as to how cold it will get near the surface. Went
conservative with initial Ice accums but expanded the area farther
south/west from earlier forecasts.

Snow/sleet accums should be confined to the highest of elevations in
Towns, Union, Lumpkin and White counties Saturday night into Sunday.
Will maintain Winter Storm Watch across these areas until confidence
becomes a bit higher on whether to upgrade to a Warning.

Outside of the winter weather concerns, what`s fairly certain is the
potential for heavy rain and strong/gusty winds developing Saturday
afternoon and continuing into early Sunday morning. Tightening
pressure gradient between sfc low moving just south and high
pressure over the Mid Atlantic will increase easterly winds across
the area. Strong 40-50kt winds around 925mb raise a level of concern
for winds especially in the higher elevations. On top of everything
else, may need to consider Wind Advisory for Sat PM through Sunday
morning. Two to locally 4 inches of rainfall is expected in the next
36-48 hours which will lead to localized river/stream flooding along
with flooding over poor drainage/urban areas.

Wrap-around precip lingering across the area Sunday night into
Monday could bring some snow showers across north GA, especially in
the favored NW-flow mountainous areas. Something to watch as we
progress through the weekend but let`s get through this initial
round of weather first.

 

Share this post


Link to post
Share on other sites
Guest
This topic is now closed to further replies.



×
×
  • Create New...