Xtreme Weather
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Severe DEEP SOUTH Severe Weather threat 18-20th
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Xtreme Weather
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GFS says what SVR threat LoL to the North confines greatest risk over Southern portions
3K NAM was scary as well line fires up along I-65 corridor yikes STP parameters of the charts if correct
3K NAM was scary as well line fires up along I-65 corridor yikes STP parameters of the charts if correct
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The WRFs should be a good indication to which way we should be leaning.
The 3km NAM would definitely be concerning. I'd like to see a deeper moisture profile, but if we get to what it's showing it may not matter. It has temp of 69 with a dewpoint of 67 across east AL. That would put LCLs on the ground.
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Xtreme Weather
Member
18z 3km NAM continues to sound the alarm also more of West GA involved
Xtreme Weather
Member
NAM continues to trend more unimpressive.
Natedogg25
Member
So it’s backing off of the threat a bit?
Stormlover
Member
Continues to? 18Z was very impressive, so it's the 0Z that wasn't as impressive
Still impressive for AL TN
The 12km NAM has been on a downward trend all day. Low level shear is decreasing, moisture depth in the boundary layer is growing more shallow, seeing much more capping from warm air aloft and lapse rates and CAPE are dropping steadily.
Bama Ravens
Member
SPC has added an enhanced risk area into the day 2 outlook (Monday). The enhanced risk has a 30% hatched area.
Enhanced risk TN AL GA. DAY2
6z NAM breaks the trend. Looks like it wants to go back to forming a small lobe of low pressure that creates a very highly sheared environment across the northern half of AL and GA. It also shows solid lapse rates and instability. It's also the first time the NAM showing explosive convection as well. The WRFs agree to supercell development around I65 as well.
WXinCanton
Member
Great AFD by Steve Nelson. One of FFC's best IMO
As vigorous shortwave moves east over TN valley, broad and
unusually strong westerly flow to the south remains in place. In
my experience with severe weather forecasts both here and in the
southern plains, this pattern has a great deal of potential to
produce atypically high instability and very strong deep vertical
wind shear with supercells the dominant mode. It has been over a
year since this area has seen supercell storms of this magnitude
(Jan 22 2017). Large hail and a few tornadoes will be likely.
Given MLCAPE values 2000-2500 J/kg and 0-6km bulk shear of
60-70kts, hail will likely be much larger than the Jan 2017 event
with sizes of 2 to 3 inches likely. If there is a bright side to
this story, it could be the low level shear, 0-1km bulk shear is
only progged of 30-35kts. This is still quite strong and should be
sufficient for a few tornadoes, but unlikely to see the larger
/long-tracked tornadoes that we saw with the Jan 2017 event or
other notable supercell-based tornado events and outbreaks.
Interestingly, CIPS top 15 analogs based on 00Z NAM valid 00Z Tue
do not contain any events in the last 10 years, so could be some
analogs with lower storm report density and thus lower analog
probabilities. Top analogs is Apr 3 1998 which produced widespread
hail over north GA but other dates have hit or miss coverage of
reports and not too many tornado events though there area some.
Other bright side of supercell events is that coverage/probability
of any point seeing severe storms will be lower than with linear
events. Not something you want to take a chance on however, plan
accordingly. Have kept PoPs closer to guidance and perhaps lower
with mainly 40-60pct Monday afternoon and evening.
Will certainly keep a close watch on this and will continue with
steady pace of impact briefings.
SNELSON
As vigorous shortwave moves east over TN valley, broad and
unusually strong westerly flow to the south remains in place. In
my experience with severe weather forecasts both here and in the
southern plains, this pattern has a great deal of potential to
produce atypically high instability and very strong deep vertical
wind shear with supercells the dominant mode. It has been over a
year since this area has seen supercell storms of this magnitude
(Jan 22 2017). Large hail and a few tornadoes will be likely.
Given MLCAPE values 2000-2500 J/kg and 0-6km bulk shear of
60-70kts, hail will likely be much larger than the Jan 2017 event
with sizes of 2 to 3 inches likely. If there is a bright side to
this story, it could be the low level shear, 0-1km bulk shear is
only progged of 30-35kts. This is still quite strong and should be
sufficient for a few tornadoes, but unlikely to see the larger
/long-tracked tornadoes that we saw with the Jan 2017 event or
other notable supercell-based tornado events and outbreaks.
Interestingly, CIPS top 15 analogs based on 00Z NAM valid 00Z Tue
do not contain any events in the last 10 years, so could be some
analogs with lower storm report density and thus lower analog
probabilities. Top analogs is Apr 3 1998 which produced widespread
hail over north GA but other dates have hit or miss coverage of
reports and not too many tornado events though there area some.
Other bright side of supercell events is that coverage/probability
of any point seeing severe storms will be lower than with linear
events. Not something you want to take a chance on however, plan
accordingly. Have kept PoPs closer to guidance and perhaps lower
with mainly 40-60pct Monday afternoon and evening.
Will certainly keep a close watch on this and will continue with
steady pace of impact briefings.
SNELSON
Xtreme Weather
Member
Not a loaded gun sounding but damn close. What you normally see in the
Plains though i.e dry punch
Plains though i.e dry punch
Parker
Member
Pretty high STP numbers on latest NAM
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