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NorthGeorgiaWX

Thursday, April 23

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Good morning!

Round 1 is underway this morning and is just entering north Georgia. All the severe weather is well south of the area and you can see where the current Tornado Watch is located this morning.

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We should not see any severe weather from round 1.

Round 2 from the SPC

Quote

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1258 AM CDT Thu Apr 23 2020

   Valid 231200Z - 241200Z

  •    ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF FAR EASTERN MISSISSIPPI EAST ACROSS PARTS OF ALABAMA...SOUTHERN GEORGIA...NORTHERN FLORIDA AND THE FLORIDA PANHANDLE...TO SOUTHERN SOUTH CAROLINA...

   ...SUMMARY...
   Severe thunderstorms are expected across a large portion of the Southeast Thursday through Thursday night, including the potential for a few strong tornadoes along with damaging winds and large hail.

   ...Synopsis...
   Between a pair of low-amplitude ridges near the West and East Coasts, broadly cyclonic flow aloft will prevail across the U.S. through the period.  Within this broad cyclonic regime, a short-wave trough is forecast to move steadily eastward across the southeastern quarter of the country.  

   At the surface, a low -- initially expected to lie in the vicinity of the Ozarks -- will move east into the Tennessee Valley area by late afternoon/early evening, and then east-northeastward across the central Appalachians.  A trailing cold front will sweep across the Southeast, while a wedge/damming front will be slow to retreat across the Carolinas.

   ...The Southeast...
   A somewhat complex/messy scenario is unfolding for today, as widespread convection currently spreading across the mid and lower Mississippi Valley into parts of Tennessee, Mississippi, and Alabama will continue moving eastward early this morning.  By 12Z, the strongest convection -- including some ongoing risk for severe weather -- should extend west-southwestward from east-central Alabama to southeast Louisiana.

   As diurnal heating/destabilization occurs ahead of the convection, expect storms to intensify -- likely organizing linearly into bands of strong/ severe storms -- which should sweep across southern Georgia and the Florida Panhandle/northern Florida, and southern South Carolina through the afternoon.  The storms will be accompanied by potential for damaging winds, along with large hail and a few tornadoes.  

   Meanwhile, in the wake of this convection, it appears that enough clearing/heating will occur across eastern Mississippi and southeast Louisiana, and into northern and central Alabama to allow sufficient airmass recovery/destabilization to occur.  Up to 1500 to 2500 J/kg mixed-layer CAPE may evolve across parts of Mississippi and Alabama, and up to 300 to 500 J/kg northward across Tennessee and into central and eastern Kentucky.

   As the cold front advances, in conjunction with the short-wave toughing aloft, this destabilization will allow new storm development to occur by early afternoon -- from east-central and southeast Mississippi east into west-central Alabama, and then northward across the Cumberland Plateau into Kentucky.  With strengthening/veering flow with height providing favorable shear for supercells, potential for tornadoes will accompany these storms -- a few of which could be strong.  Large hail is also expected, along with damaging winds.

   The convection will continue eastward across Alabama, and eastern portions of Kentucky and Tennessee through the afternoon, and into Georgia.  However, uncertainty with respect to degree of severe risk increases with eastward extent across Georgia, due to questions regarding the degree of airmass recovery which will have occurred in the wake of earlier storms -- likely still ongoing over northern Florida.  Still, it appears that fairly substantial all-hazard severe risk will extend into at least central Georgia into the evening hours, before risk begins to diminish.

586361648_SPC_CO_Day1State(4).thumb.png.931c54b4b70e7325979aa6eab12c6606.png

765612359_SPC_TP_Day1State(4).thumb.png.61ccba52f87468b375f80747bff3a360.png

970567135_SPC_WP_Day1State(4).thumb.png.75bd12937f5108aac8fb38be24814e9c.png

1600807805_SPC_HP_Day1State(3).thumb.png.f8b5706112e869cfdca3cd461163a40d.png

Keep in mind that the hatched areas indicate increased probabilities of "Significant" hail/wind/tornadoes.

This from the Atlanta NWS

Quote

For the most part we should continue to see rain across the area through daybreak with the main frontal boundary approaching NW GA by 12z. This system looks like it is weakening a bit especially along its northern half and should continue to do so as it nears the state. The models do show some strengthening of this system during daytime heating while this system is directly over central GA.

A brief lull in convection is likely during the late morning/early afternoon before firing during the mid-late part of the afternoon. The warm front is currently over southern AL and is moving slowly northward. This front should stall across Central portions of GA this afternoon. Conditions will become favorable for discrete convection that may eventually morph into another strong line/QLCS during the afternoon and evening hours. The afternoon convection will also have 60+ dewpoints to work with, which will contribute to CAPE values 1500-2000 J/kg range. This will also be determined by just how far north the warm front moves today. The mid and upper levels will also be favorable with a 60-80kt 850 jet, strong shortwave energy and broad/strong upper divergence. Forecast hodographs still show good potential for tornadoes along with damaging wind gusts.

With all this being said SPCs enhanced risk area still looks good and it appears the best chances for severe storms will be after 2pm across mainly central and portions of N GA. This frontal system is expected to weaken a bit after sunset as it moves south of the area by 2am Fri. A drier airmass moves in behind this system and Friday looks to be dry with high temps in the 70's and 80's.
 


The NWS has requested Spotter activation for this afternoon and evening.

Quote

*** ALERT ***
Spotter activation is requested for this afternoon and tonight across central and portions of northern Georgia. Please relay any information about observed severe weather to the NWS while following all local, state, and CDC guidelines. 

 

I'm still not see a big severe weather event for north Georgia and I personally think the wedge will hold on longer that the SPC thinks. We'll see if we know more about Georgia wedges than they do. 🙂 Here is a loop showing the two previous outlooks from yesterday and the current so you can see how it's evolved. 


Here is the HREF high resolution short range ensemble and this loop is showing the probability of seeing STP>1 (Significant Tornado Parameter) Notice the energy fades as it approaches. 

 

I will be tracking the severe weather all day and into the evening, so check back for the latest updates. 
Hope everyone stays safe and has a great day!

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1 minute ago, Jeff9702 said:

I love Pecos Hank's work, been following him for awhile.

Me too. He also has some great "educational" type videos that I used when I did some weather classes for 4th graders. I like his calm demeanor. You never hear him get excited. Great stuff.

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Just now, NorthGeorgiaWX said:

Me too. He also has some great "educational" type videos that I used when I did some weather classes for 4th graders. I like his calm demeanor. You never hear him get excited. Great stuff.

That is the key. most videos are dudes freaking out and ruining the video. his stuff was the first time i heard a tornado in a video. i wannna hang out with him so bad lol.

 

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I'm still not see a big severe weather event for north Georgia and I personally think the wedge will hold on longer that the SPC thinks. We'll see if we know more about Georgia wedges than they do. 🙂 


 

I pray you’re right. Thanks so much for all that you do. It’s so important.

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See the change? See the wedge? 🙂 1333724161_fema04_swody1(1).thumb.png.d66ddcdf85fdcecbbfbffb63386a66c0.png

Quote

In addition to destabilization inland related to warm-frontal
   passage, muted diurnal heating is expected beneath the anvil-cloud
   cover.  Theta-e advection inland from the Atlantic over parts of
   southeastern GA also should contribute.  The northward extent of the
   destabilization favorable for surface-based inflow is uncertain, but
   increasingly appears to be not as vigorous as suggested by earlier
   guidance, due to the MCS' projected translation relative to the
   inland pace of the warm front, and its spread of downshear precip/
   clouds well northeastward across GA/Carolinas. As such, some
   southward shunting of the northern probability lines is warranted. 

   In addition, a band of strong-severe convection may shift as far
   south as central FL by the end of the period. 

   Severe potential still exists with a possible second episode,
   along/ahead of the cold front from the Tennesseee Valley region
   southward, but is very conditional.  
Substantial stabilization to
   near the Gulf Coast is associated with the leading MCS.  Only a
   narrow back door of at least marginally favorable theta-e advection
   and related airmass recovery will exist to the west, which comes
   with offsetting influences:
   1.  Southwesterly near-surface flow ahead of the front will yield
   the best trajectories for theta-e recovery around the morning MCS
   outflow, but also contribute to relatively reduced low-level shear
   and convergence. 
   2.  Any southerly to southeasterly trajectories from the MCS passage
   will be more convectively stabilized.
   Still, a narrow plume of favorable buoyancy may develop -- with
   MLCAPE ranging from around 500-1000 J/kg in the north where deep
   lift, cooling aloft and shear will be greatest, to around 2000 J/kg
   in the south under weaker ascent and shear.  With uncertain
   coverage, duration and intensity of convection in this regime, the
   risk level is not as great as farther southeast, and should diminish
   markedly after dark.

 

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Once the lockdown it over, we should have some sort of wedge party, lol.

But seriously, even the bit theybpushed back is in the shape of the wedge, that is awesome.

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All the images are slow to update, but here are the latest tornado/wind/hail probabilities. All good news. This will mainly be just a rain event for north Georgia. It is not a ZERO probability though. Notice some areas of northwest Georgia still have a 5% chance for a tornado within a 25 mile point. 

1145698591_SPC_TP_Day1State(5).thumb.png.68d926bdb0c917bae311a5848b3b0bc9.png

20911261_SPC_WP_Day1State(5).thumb.png.e82fdf4d855d1268c2f9e4140173f746.png

946062115_SPC_HP_Day1State(4).thumb.png.78d881fa8e1e0f207f9c889a76a81449.png

 

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Dude. There is some serious wind on the back edge of this rain. Holy cow! Our power flickered several times and we NEVER have power issues where im at!

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I hate having so many trees around. My weather station doesnt get a good wind reading but our dogwood was leaning over from it!

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11 minutes ago, HiTekRedNek said:

Dude. There is some serious wind on the back edge of this rain. Holy cow! Our power flickered several times and we NEVER have power issues where im at!

We're in Cobb and having a lot of power flickering too, plus have a ton of trees in our backyard. Hopefully none come down and the power stays on. 

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Yeah after the back edge of the rain shield moved through I had a wind gust of 31 on my weather station in Buford

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13 minutes ago, Shannon said:

Yeah after the back edge of the rain shield moved through I had a wind gust of 31 on my weather station in Buford

Yea, I have too many trees and shrubs around the perimeter of our yard, so wind is not what I do well right now. I'm getting ready to send my Davis VP2+ back for a refurbish. Once we get moved I'll reinstall and reset all my data for the new location. The nice thing about the VP2+ is that I can detach the anemometer from the main station so that I can mount it on the roof. I'll then be measuring winds at 2000 feet somewhat accurately. 

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mcd0457.gif.6e93ff879a98a6bcd793d9d966e90726.gif

Quote

   Mesoscale Discussion 0457
   NWS Storm Prediction Center Norman OK
   0929 AM CDT Thu Apr 23 2020

   Areas affected...southern Georgia and northern Florida

   Concerning...Severe potential...Watch likely 

   Valid 231429Z - 231530Z

   Probability of Watch Issuance...80 percent

   SUMMARY...
   The severe threat including potential for damaging wind
   and tornadoes is expected to spread eastward through southern
   Georgia and northern Florida during the late morning into the
   afternoon. A tornado watch will likely be needed soon.

   DISCUSSION...
   This morning a line of severe storms extends from
   southeast AL into the northwestern Florida Panhandle. Embedded
   supercell structures continue to be observed on the northern End of
   the line over southeast AL. This activity is moving east around 40
   kt. A warm front currently extends from northern FL northwest into
   into far southeast AL. A 50 kt southerly low-level jet will migrate
   through this region in association with progressive shortwave trough
   and contribute to northward advance of the warm front into the
   afternoon. As this occurs, dewpoints will rise through the low to
   mid 60s F resulting in northward destabilization of the boundary
   layer and MLCAPE increasing to 1500 J/kg. Vertical wind profiles
   with 50+ kt effective bulk shear and large low-level hodographs will
   support organized storms including supercells and bowing segments
   capable of damaging wind and tornadoes.

 

 

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