Friday, December 8

[NorthGeorgiaWX]

Good morning!

We are going to have a fairly dynamic system come through this weekend, and even though we'll be warm enough for rain, we'll pretend like it's a practice run for this winter when it's colder. 🙂

An upper level trough will be advancing our direction over the next day or so, and that will be our next weather maker. A few days ago the system looked worse than it is going to be, but thankfully the bulk of the severe weather will be confined to our west. 

 

This is the Day 3 Convective Outlook from the Storm Prediction Center. 

Quote

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0222 AM CST Fri Dec 08 2023

   Valid 101200Z - 111200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF THE
   SOUTHEAST STATES...

   ...SUMMARY...
   Isolated severe thunderstorms will be possible through Sunday
   evening across parts of the Southeast States, mainly in the form of
   sporadic damaging winds and a few brief tornadoes.

   ...Synopsis...
   An amplified, positive-tilt upper trough from ON to east TX at 12Z
   Sunday will take on a neutral to slight negative tilt as intense
   mid-level southerlies become asymmetrically confined ahead of it.
   This will induce surface cyclogenesis from the central/southern
   Appalachians across the Northeast into New England through early
   Monday. Greater surface low deepening should occur during the latter
   half of the period.

   ...Southeast...
   A swath of showers and embedded thunderstorms will likely be ongoing
   Sunday morning from eastern TN to the western FL Panhandle vicinity
   along a convergent surface cold front steadily progressing eastward.
   Diurnal diabatic heating ahead of this activity is still expected to
   be muted, with extensive low-level moistening and resultant
   cloudiness anticipated. Consensus of guidance, especially the 00Z
   deterministic ECMWF and its ensemble mean, suggests that low-level
   warm theta-e advection from the western Atlantic across the
   Carolinas will probably result in a secondary swath of convective
   development during the day. Amid weak mid-level lapse rates, MLCAPE
   in excess of 500 J/kg appears unlikely, especially where 850-mb
   winds greater than 40 kts are prominent. Even so, transient
   low-level updraft rotation will probably be occasionally noted in
   the relatively deeper convective elements in both the frontal and
   warm conveyor regions. These will  be conditionally capable of
   producing a few brief tornadoes and sporadic damaging winds where
   scant to meager surface-based instability can develop.

   ..Grams.. 12/08/2023

 

The severe weather will be concentrated over Louisiana, Arkansas, and Mississippi on Saturday, so that will leave us with some general showers and thunderstorms.

Saturday

 

If we have any severe, we will see it early Sunday morning in advance of the cold front. These are shear values. Notice the sharp dip in the winds as the upper level trough begins a negative tilt. 

 

Those upper level winds will be ripping above us on Sunday. 

250 mb or ~34,000 feet

 

500 mb or roughly 18,000 feet

 

700 mb winds or roughly 9,900 feet

 

View of the upper level trough taking on a slightly negative tilt. 

 

Sunday

 

More details from the Atlanta NWS office.

Quote

This trough will slowly shift E through the
remainder of the weekend, with widespread showers returning to the
area by Saturday afternoon. Isolated to scattered thunderstorms are
possible with this system, with the best chances Saturday evening
across the NW zones. Instability will be limited, but wind shear
will be high. The greatest threat of isolated strong storms is
expected Sunday morning when CAPE values increase to 200-300 J/kg and
coincide with increased wind shear. If this activity develops, it
will be just ahead of the cold front.

South winds will increase and become gusty Saturday night into Sunday,
with the highest gusts over the North Mountains late Saturday night and
across a more widespread area Sunday afternoon as strong low-level
winds mix to the surface. Wind gusts may approach 50 mph across some
of the highest terrain of NE GA on Sunday, with gusts near 40 mph
across much of N Central, NE, and E Central GA (including portions of
the Atlanta metro area).

As scattered light showers linger Sunday evening and colder air
begins to filter in, some light snow showers are possible over the NE
mountains. .1-.2 accumulations are possible on the highest terrain.

Colder temperatures and drier conditions are expected again early
next week, with nighttime lows dipping to near 20 across the NE
mountains and subfreezing temperatures expected across most of
the remaining area. Temperatures will gradually warm through the
remainder of the upcoming week.

 

Temperatures will fall sharply behind the front, and by 6 AM Monday morning, we'll be looking at a 25 degrees drop in temperatures compared the same time Sunday morning.

 

The anomalies at 8 AM Monday.

 

Temperatures Monday morning will be in the upper 20's and lower 30's for most of north Georgia.

 

As noted in the discussion above, the winds will start to pick up on Saturday, and peak during the night Saturday and into Sunday morning before the passage of the cold front, and then again on Monday behind the cold front. These are winds and gusts on Monday.

Winds at 33 feet (official reporting height).

 

Wind gusts at 33 feet.

 

And yes, they did mention the potential for some of the white stuff to fly in and around the higher elevations, but the chances are small. This first image shows the "expected" amounts. Don't blink or you'll miss it. 🙂

 

There is a very low 10% chance of seeing this much.

 

And your chances of seeing 0.1" or more of snow. This would be a dusting.

 

The deterministic models show the "wrap around snow", but they all keep it further to our north over the Smokies. Early in the season, we see a lot of cold chasing the moisture, hopefully as we get colder, that will change. Of course, that is never a good way to try to get some snow. 

 

Rainfall amounts will be fairly high for north Georgia, with totals of 1-2" with locally higher amounts. We need the rain, so let it pour. The Atlanta NWS and the Weather Prediction Center are in sync with rainfall totals though the evening on Sunday.

 

The latest drought monitor data shows that north Georgia is solidly in the D3-D4 range, which his "Extreme Drought", so we can use all the rain we can get. 

 

 

The models are starting to come around to the current thinking about the winter season, and beginning to show colder weather beginning around the Christmas timeframe and  beyond. Combine the colder air with our active southern jet, and we start to see opportunities for some snow.  These are the extended range models, and two of these go out to January 8th, and the other one to the 11th. 

[NorthGeorgiaWX]

 

 

[NorthGeorgiaWX]

I have two new pages on my website now, one is for the NWS Snow Forecast images, and the other is the GOES 16 satellite loops. 
 

GOES 16 Satellite Loops

WWW.DACULAWEATHER.COM

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GOES16 Satellite Loops

 

NWS Snow and Ice Forecast

WWW.DACULAWEATHER.COM

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NOAA NWS Winter Probabilities

 

[NorthGeorgiaWX]

Two areas to our west may be looking at Tornado Watches.

[NorthGeorgiaWX]

New Tornado Watch just issued.

[NorthGeorgiaWX]

It's clear where the cold front is, and these are dew points. The warm front has move a little further north (yellow line) than what the map shows, and it will eventually arrive here. 

[Asperman1]

1 hour ago, NorthGeorgiaWX said:

New Tornado Watch just issued.

Do you think any will need to be issued in Georgia as the night goes on?

[NorthGeorgiaWX]

11 minutes ago, Asperman1 said:

Do you think any will need to be issued in Georgia as the night goes on?

Probably not. they are still hours and hours away, so no heat to work with. The shear values are high, but I don't believe a Tornado Watch will be issued for most of north Georgia. 

[Asperman1]

Just now, NorthGeorgiaWX said:

Probably not. they are still hours and hours away, so no heat to work with. The shear values are high, but I don't believe a Tornado Watch will be issued for most of north Georgia. 

So, there will be storms over night, but due to the fairly low temperature today, and the fact it will be dark, severe threat should be fairly low, but still existing, for north GA?

[NorthGeorgiaWX]

13 minutes ago, Asperman1 said:

So, there will be storms over night, but due to the fairly low temperature today, and the fact it will be dark, severe threat should be fairly low, but still existing, for north GA?

Correct

[NorthGeorgiaWX]

14 minutes ago, Asperman1 said:

So, there will be storms over night, but due to the fairly low temperature today, and the fact it will be dark, severe threat should be fairly low, but still existing, for north GA?

Generally 4 to 7 am for most of north Georgia,

[NorthGeorgiaWX]

19 severe thunderstorm warnings, 1 considerable, and 2 tornado warnings at 7 pm. Those are dew points.

[Weatherdude]

 

[Weatherdude]

 

[Weatherdude]

 

[NorthGeorgiaWX]

 That's cool!

[Preston]

The top down process for snow this evening has begun. The webcams in Highlands, NC (4,100ft) are showing some flakes flying at 34 degrees. I don't think we will get there this evening here in the valley in Clayton at 2,000ft. We are currently 45 with rain.  

Highlands NC Webcams - Highlands Chamber of Commerce

WWW.HIGHLANDSCHAMBER.ORG

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Highlands, NC webcam featuring the downtown section of Highlands, NC and the Whiteside Mountain area just east of Highlands NC on Highway 64 between Highlands and Cashiers.

 

[Weatherdude]

 

[Weatherdude]

 

[Weatherdude]

 

[Weatherdude]

 

[Weatherdude]