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Severe Weather for Sunday, April 14

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Thought I'd create a new topic for this event so that we can keep all of the talk and updates here. I'll still add some comments etc in the morning update each day, but the main discussion will be here.  Much of this first post is a re-cap from the morning post, but I'll still go ahead and re-share here. 

As of now... the Storm Prediction Center has placed the north Georgia area under an "Enhanced" risk for severe weather on Sunday. 

GA_swody3-12.png.5f615d5a18772d0c86aef6ba26860d36.png

 

UPDATED VERSION as of 4/13/19 5:40 am

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Quote

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0230 AM CDT Fri Apr 12 2019

   Valid 141200Z - 151200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM SOUTHERN
   OHIO AND WEST VIRGINIA SOUTHWARD INTO THE SOUTHEAST...

   ...SUMMARY...
   Strong/severe thunderstorms are anticipated Sunday -- centered over
   the mid and upper Ohio Valley, and central and southern
   Appalachians.

   ...Synopsis...
   A strong mid- and upper-level trough exiting the Plains early in the
   period is expected to advance steadily east across the
   Mississippi/Tennessee/Ohio Valleys and central Gulf Coast states,
   reaching a position from the lower Great Lakes to the southern
   Appalachians/Southeast late in the period.

   At the surface, a deepening low is forecast to shift east-northeast
   across the Ohio Valley through the day, and then across the central
   Appalachians to the Hudson Valley vicinity by the end of the period.
   Widespread thunderstorms -- and a broad severe risk -- will
   accompany this system.

   ...The Ohio Valley and central Appalachians south to the Southeast...
   Showers and thunderstorms are forecast to be ongoing in a
   north-south band from Indiana to Alabama early in the period, ahead
   of the advancing cold front.  As modest heating of a moistening
   pre-frontal warm sector commences, 500 to 1000 J/kg mixed-layer CAPE
   is expected to evolve ahead of the ongoing band of convection, from
   the Ohio Valley to the Gulf Coast.  This should result in a gradual
   intensification of storms through the afternoon, aided by a very
   strong deep-layer wind field accompanying this storm system --
   including 80 to 100 kt south-southwest flow at mid levels.

   Primary storm mode is progged to be banded/loosely linear, with
   embedded/complex bows and rotating updrafts.  Damaging winds will
   likely be the primary threat, though tornadoes will also be possible
   across much of the area -- particularly near and west of the
   mountains.  Risk should diminish gradually through the evening,
   though local wind risk may persist through the end of the period.

   ..Goss.. 04/12/2019

 

We probably won't see a 3 day update again, as the next update is 4:30 am tomorrow, so we'll start looking for the Day 2 updates late today. 

Again, it's ALWAYS good to check the upstream forecast offices for their updates, they see the storms before we do, so knowing what they are thinking goes a long way toward what we may see here.

Huntsville AFD - http://wx.northgeorgiawx.com/afd_hun2.html/

Quote

Now, to discuss the severe potential with this system. The very
strong low level wind field and good jet aloft will result in strong
shear over the area Saturday night into Sunday. Due to the timing and
better heights falls to the west of the area, lapse rates don't
really steepen until storms are on our doorstep, which would yield
CAPE of around 500 J/kg. The better co- location of shear/instability
is off to the SW over the ArkLaMiss, where supercellular storms
could develop Saturday afternoon. As the system shifts east towards
the TN Valley these individual storms should begin to merge into a
QLCS. The strong low level winds should still allow for some embedded
supercellular like structures in the line. SRH values could be
upwards of 400-500 m2/s2. All of the parameters are lining up to
suggest a potentially damaging severe weather event across the area.


Models still have some disagreement in the timing of storms into
area, but looks likely to occur close to midnight. (North Alabama area) They've been
showing a slower arrival, but we've seen cases where this was a 3-4
hours too slow and it could be as early as 10pm in NW. Confidence in
this is still low. With the event occurring during the overnight
hours an emphasis should be placed on making sure folks have ways to
get the warnings.


One possible issue that could limit the overall threat is a signal in
the QPF fields along the Gulf Coast. It's possible that as storms
develop Saturday afternoon they eventually merge into a complex that
will feed off of and move along the higher instability axis to the
south. This could end up limiting our instability even further and
based on the timing could be a case where the western half of the
area has the greatest chances for severe weather and not much to the
east. While I mention this, think that the overall strength of this
system and the forcing over the area will limit this scenario but
it's just something to look out for.


As the system continues east on Sunday, lapse rates aloft steepen
further and it's possible that as the actual front moves across the
area we see a redevelopment of activity Sunday afternoon. A strong
dry slot will be moving over the area, which combined with even
stronger shear could result in storms not able to sustain their
updrafts to result in a widespread severe threat. It's still
possible that we see some isolated severe storms Sunday afternoon.

 

This in the hazardous Weather Outlook from the Atlanta NWS office

Quote

.DAYS TWO THROUGH SEVEN...Saturday through Thursday...

...SEVERE THUNDERSTORMS POSSIBLE SUNDAY...

Scattered severe storms are possible beginning as early as Sunday
morning, as a strong storm system moves through the state. Damaging
winds and a few tornadoes will be possible. The threat for severe
weather should end early Monday morning.
 

ffc_sunday_12.thumb.jpg.235eafc2828da0f22d2bad26adf59da2.jpg

 

So keep checking back here and make sure you "follow" this topic. 

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Following closely. 

Steve, I’ve noticed that other than the city limits of Dallas itself, there’s MANY in my area that do NOT hear tornado/warning sirens even when they are tested. Who would you suggest contacting or what dept is in charge of that? Public safety? I’m literally JUST OUTSIDE city limits and hear nothing. Could potentially be very dangerous for those who don’t have access to cell phone alerts or if power goes out. 

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NWS Birmingham Discussion

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Meanwhile, a surface low pressure system lifts northeastward out of Southeastern
TX and into the Ozarks by Saturday evening, stretching a cold front
through the ArkLaMiss. Guidance suggests a pre-frontal shortwave
could lift through as well, being a trigger for convective
initiation. The upper level trough becomes more negatively tilted
Saturday night, and the low level jet ramps up substantially across
Central AL during the overnight hours. I expect a broken line of
storms to move through MS and into western portions of AL after
midnight Saturday night into Sunday. Ahead of this line, the
environment is highly sheared with 0-6km bulk shear over 50kts and 0-
3km SRH over 350 m2/s2. The mode of storms is still somewhat in
question with some latest guidance suggesting more of a cluster of
convection along the line versus cellular, but 0-6km shear vectors
are forecast to be 40-50 degrees in relation to the north-south
oriented boundary, so I would expect more of a broken line with
individual cells. This is picked up well in the 00z NAM and ECMWF
being consistent with streaks in the precipitation fields. A couple
more potential limiting factors are instability and lapse rates.
Model guidance has gone back and forth on just how much instability
persists given the overnight timing of the storms. Considering the
strong jets at 925mb and 850mb, I think we should be able to
maintain some instability even with the loss of daytime heating due
to the increase in low level moisture and warm air advection from
the Gulf. With the tall, skinny CAPE profiles, it doesn't take much
change in either the temp or dewpoint to make significant
differences in the overall instability, which helps explain the back
and forth nature in the model guidance. The lapse rates aren't
overly impressive, but the strong dynamic forcing should help
overcome this. Therefore, I've increased the overall risk of severe
weather across Central AL and kept the timing mainly in the early
morning hours Sunday to early afternoon. Some newer guidance tries
to bring in a second line of rain behind the main line, but
environmental variables do not look sufficient in the late afternoon
to Sunday evening to support any severe storms.

 

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2 minutes ago, LHarkins913 said:

Following closely. 

Steve, I’ve noticed that other than the city limits of Dallas itself, there’s MANY in my area that do NOT hear tornado/warning sirens even when they are tested. Who would you suggest contacting or what dept is in charge of that? Public safety? I’m literally JUST OUTSIDE city limits and hear nothing. Could potentially be very dangerous for those who don’t have access to cell phone alerts or if power goes out. 

Tornado sirens are generally one of the last forms of notification you want. They are primarily made for areas where there are outdoor activities going on. Sirens are also for very specific areas and not intended to be heard outside of that range.  I would say that the vast majority of areas don't have any at all. 

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Quote

Tornado sirens are no longer the best way for Gwinnettians to stay ahead of inclement weather.

At least not according to Gwinnett County Spokesman Doug Nurse. He said residents today are better off utilizing the county’s wireless emergency alerts to stay ahead of tornado activity.

“Sirens, those are outdoor warning devices,” Nurse said. “In a storm, everybody is already indoors and everybody has smartphones, now.”

Gwinnett County has had the wireless emergency alert system for about two years now, he said. The alerts send as a push notification to residents’ phones if a tornado touches down near by — the same circumstances that would set off a traditional tornado siren.

“We’ve had it for two years and we haven’t had to use it, yet,” Nurse said.

Residents don’t need to subscribe to any service or download an app to get the alert notifications.

Nurse said residents can opt out of the alerts if they want, but he wouldn’t recommend it. The alerts don’t add any cost to phone bills.

Still, residents who choose to opt out of the county’s alert systems can stay ahead of tornado activity in ways other than listening out for tornado sirens, Nurse said. He suggested listening to a NOAA weather radio, tuning in to local radio or television stations or downloading the Ready Georgia mobile app.

“We recommend something like that as opposed to sirens,” Nurse said.

In part, that’s because electronic media alerts easily reach more Gwinnett County residents than sirens do. As of now, six of Gwinnett’s 15 cities have tornado sirens. That includes Berkeley Lake, Dacula, Duluth, Norcross, Sugar Hill and Suwanee.

Georgia Gwinnett College and Gwinnett Technical College also have sirens on their campuses.

If residents are outside in these areas and hear the long wail of a tornado siren, Nurse said they should seek cover immediately, preferably in a bathroom or sturdy structure. If getting into a building isn’t an option, he said officials recommend lying flat in a ditch or other low-lying area.

In the end, as long as residents stay safe, Nurse said it doesn’t really matter how they keep ahead of stormy conditions.

“Many systems are in place to provide information about severe weather,” he said. “We encourage people to stay informed.”

 

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Posted (edited)

Steve I noticed that Bham NWS had issued a level 3 threat for all their coverage area. The SPC only has level 2. Bham said they felt the need to raise to level 3.  I am worried some about a squall line, but the biggest worry is discreet super cellular cells——if they form.  You see anything that would warrant their move?

 

 

Edited by RickyD
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NWS Atlanta update from Steven Nelson. 

Quote

Main concern in the period is likelihood, timing, modes and
intensity of convection on Sunday. 12Z guidance in good agreement on
overall timing and intensity of short wave trough, located near Ern
OK/Wrn AR 12Z Sun with very strong jet ahead of it over the SE
CONUS, H5 speeds over 100kts and considerable 0-6km deep shear

progged. Evolution of convection much more difficult to predict.
Expect line of convection from overnight Sat night to be moving east
into NW GA after 12-15Z Sun. 3km NAM nest indicates this line will
weaken as it pushes east into more stable air while new convection
develops to the west in north AL around 21Z, closer to the upper low
and original pre-frontal trough or cold front and moves into NW
counties around 00Z. Not enough hires guidance available to support
this solution, local WRF models and NCEP hires windows only go to
48hrs. Have created hourly grids for the Sunday period to better
show best estimate of timing. Siding more with thought that original
line will hold together longer than 12Z NAM nest indicates.

Regardless of timing, environment will be favorable for some
supercells ahead of the line of convection. Deep shear, as
mentioned, very strong and due SW direction just on the favorable

side of cell-based convective mode. Low level shear may be a tad
weak as will be SBCAPE which is "only" progged around 1000 J/kg. If
line weakens quicker than expected and more sunshine occurs Sunday,
would see more substantial CAPE than this, but not seeing any
indication of this in guidance. Main threat should be damaging wind
with potential for significant tornadoes contingent on seeing
greater instability and low-level shear. If line can slow down,
moving into Georgia around 18Z, that would also provide better
environment for tornadoes.


After upper low moves out late Sun night, brief, one-day cool down
followed by warmup in advance of next system progged for Thur/Fri.
Models a bit slower than the prev forecast with this wave. Too far
out to reliably gage how much instability and vertical wind shear
will be present but overall pattern and strength very similar to
this weekend's system. Can't rule out another round of
vigorous severe storms Thurs or Fri.

 

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38 minutes ago, RickyD said:

Steve I noticed that Bham NWS had issued a level 3 threat for all their coverage area. The SPC only has level 2. Bham said they felt the need to raise to level 3.  I am worried some about a squall line, but the biggest worry is discreet super cellular cells——if they form.  You see anything that would warrant their move?

 

 

Yes, especially over MS and west central AL

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25 minutes ago, Thebrookes said:

What are your thoughts on this trend?

Screenshot_20190412-143259.png

That is a "possibility" and was mentioned int he SPC discussion. However, the dynamics are still in place and that may overcome any moisture cutoff. 

 

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31 minutes ago, NorthGeorgiaWX said:

That is a "possibility" and was mentioned int he SPC discussion. However, the dynamics are still in place and that may overcome any moisture cutoff. 

 

I am slowly getting more and more scared, especially Since my family is going to the renaissance festival Sunday

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29 minutes ago, Asperman1 said:

I am slowly getting more and more scared, especially Since my family is going to the renaissance festival Sunday

Sunday is NOT the day to go to that. Saturday is much, much better.

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2 minutes ago, NorthGeorgiaWX said:

Sunday is NOT the day to go to that. Saturday is much, much better.

I wish we could change it, but we have other stuff going on on Saturday and have had the tickets for a while now, aside from the obvious of just don’t go, do you have any tips to stay safe?

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2 minutes ago, Asperman1 said:

I wish we could change it, but we have other stuff going on on Saturday and have had the tickets for a while now, aside from the obvious of just don’t go, do you have any tips to stay safe?

Well... for a tornado out in the middle of nowhere, laying flat in a ditch is about it. The car is fine for a thunderstorm as long as you aren't parked under a tree. 

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1 minute ago, NorthGeorgiaWX said:

Well... for a tornado out in the middle of nowhere, laying flat in a ditch is about it. The car is fine for a thunderstorm as long as you aren't parked under a tree. 

Thank you, I hope this all weakens before Sunday though 

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1 hour ago, Asperman1 said:

Thank you, I hope this all weakens before Sunday though 

Do you think there is a chance they might close the Ren Fest for that day, given the weather situation?  I'd think they wouldn't want their employees and visitors to be in danger.  Maybe they will refund your ticket charge, if you pre-purchased?

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5 minutes ago, Bagsmom said:

Do you think there is a chance they might close the Ren Fest for that day, given the weather situation?  I'd think they wouldn't want their employees and visitors to be in danger.  Maybe they will refund your ticket charge, if you pre-purchased?

No Clue, but maybe

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Getting really worried for the Northern Louisiana region on Saturday. I've got friends in that area and the HRRR is trending more unstable by the hour. Hopefully it's overdone.

 

 

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9 hours ago, Thebrookes said:

What are your thoughts on this trend?

Screenshot_20190412-143259.png

Is it just me or did Glenn wipe his Facebook posts out? He seems so sensitive.

 

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8 minutes ago, JenRay said:

Is it just me or did Glenn wipe his Facebook posts out? He seems so sensitive.

 

He did 

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