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Severe WX Severe Weather Event April 13-14, 2019

The way the timing and ingredients are trending, Atlanta area might get an unpleasant early Sunday morning surprise.
 
Basically all of the CAMS are rushing the line of storms/cells into Alabama around midnight, a little after...some show more storms than others...but idea I have is that the evening CAPE will not diminish as much as shown, values could still be nearly 1000j/kj, possibly 1200. Storm mode will be somewhere around supercell/QLCS or becoming linear with time.
 
Richardjacks said:
Basically all of the CAMS are rushing the line of storms/cells into Alabama around midnight, a little after...some show more storms than others...but idea I have is that the evening CAPE will not diminish as much as shown, values could still be nearly 1000j/kj, possibly 1200. Storm mode will be somewhere around supercell/QLCS or becoming linear with time.
Click to expand...

It seems like the models are going back in forth in terms of storm mode, my uneducated guess would be QLCS.
 
BMX Discussion
.LONG TERM...
Saturday through Sunday.

Saturday begins with the previously stalled frontal boundary already
to our north. There is some isentropic lift in the morning on the
south side of that boundary, which could lead to scattered showers
across our northern and northwestern counties, but this should also
lift north of our area by the afternoon/evening hours. 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.
 
champal3003 said:
BMX Discussion
.LONG TERM...
Saturday through Sunday.

Saturday begins with the previously stalled frontal boundary already
to our north. There is some isentropic lift in the morning on the
south side of that boundary, which could lead to scattered showers
across our northern and northwestern counties, but this should also
lift north of our area by the afternoon/evening hours. 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.
Click to expand...
that disco was from this morning, they just repeated it this afternoon.
 
From the NWS Huntsville: 10:01 PM: We are aware that most of our radio transmitters are out right now, including Arab, Cullman, Florence, Fort Payne, and Winchester. We are actively and continuously working with technicians to get these back up ASAP. We will post an update as soon as we have one.
 
Tornado probabilities for tomorrow through 7am Sunday:

day1probotlk_1200_torn.gif


From the Storm Prediction Center’s discussion:

A potential for long-track tornadoes will be possible and a regional outbreak of tornadoes could occur across parts of the moderate risk area. By early evening, the cluster of severe storms is forecast to move into southwestern and central Mississippi where a potential for strong tornadoes will continue. However, the wind-damage threat may become the more dominant hazard as the convection moves further to the east where instability is forecast to be weaker.
Click to expand...
 
Makes sense as many have suggested that areas E of the MS river into MS might have some serious issues; definitely think south-central MS is gonna get rocked too

A 6z Moderate retention is not surprising, but by the time I get up I expect to see a High Risk. I'm sure it's last minute storm mode and convective initiation questions holding them off for now
 
Richardjacks said:
Basically all of the CAMS are rushing the line of storms/cells into Alabama around midnight, a little after...some show more storms than others...but idea I have is that the evening CAPE will not diminish as much as shown, values could still be nearly 1000j/kj, possibly 1200. Storm mode will be somewhere around supercell/QLCS or becoming linear with time.
Click to expand...
So a midnight and after tornadoes could happen? I hate night storms.
 
06z HRRR is nasty across Alabama. It has an axis of 1000+ j/kg CAPE to roughly I-20 and it depicts a line of supercells/embedded supercells moving across the state overnight. If the recent trend of speeding the line up holds, then I think these cells will move across a pretty supportive environment (better thermos)for tornadoes, given that they are able to stay within the axis of greater instability.

1359
 
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