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April 2nd-3rd severe weather outbreak


LithiaWx

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Moderate mainly in south Alabama on the new Day 2.

day2otlk_1730.gif?1491156549692

 

...Eastern MS...AL...Western GA...FL Panhandle...
   A line of severe thunderstorms capable of particularly damaging
   winds and tornadoes will be ongoing at 12Z Monday roughly from
   northwest AL into southern MS. Although the storm mode will be
   mostly linear along the front, embedded circulations and QLCS
   tornadoes are expected given strong shear profiles. In addition,
   discrete supercells may form ahead of the line, especially across
   the Moderate Risk area where instability will be greatest. A few
   strong tornadoes are possible in this corridor.

   There are predictability issues with the initial position of the
   early day storms. If they are farther west than expected, a more
   widespread wind threat could exist farther northwest than currently
   forecast. 

   ...Eastern GA into SC...
   Several models support the idea of supercells forming along the
   returning warm front across eastern GA into western SC during the
   day. Forecast sounding show impressive hodographs supportive of
   supercell tornadoes given the favorable instability profiles. As
   such, have expanded the Enhanced Risk into the region. The ESRL HRRR
   model shows supercells developing around 18Z, moving into central SC
   by late afternoon and evening.
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5 minutes ago, jrips27 said:

Moderate mainly in south Alabama on the new Day 2.

day2otlk_1730.gif?1491156549692

 


...Eastern MS...AL...Western GA...FL Panhandle...
   A line of severe thunderstorms capable of particularly damaging
   winds and tornadoes will be ongoing at 12Z Monday roughly from
   northwest AL into southern MS. Although the storm mode will be
   mostly linear along the front, embedded circulations and QLCS
   tornadoes are expected given strong shear profiles. In addition,
   discrete supercells may form ahead of the line, especially across
   the Moderate Risk area where instability will be greatest. A few
   strong tornadoes are possible in this corridor.

   There are predictability issues with the initial position of the
   early day storms. If they are farther west than expected, a more
   widespread wind threat could exist farther northwest than currently
   forecast. 

   ...Eastern GA into SC...
   Several models support the idea of supercells forming along the
   returning warm front across eastern GA into western SC during the
   day. Forecast sounding show impressive hodographs supportive of
   supercell tornadoes given the favorable instability profiles. As
   such, have expanded the Enhanced Risk into the region. The ESRL HRRR
   model shows supercells developing around 18Z, moving into central SC
   by late afternoon and evening.

That's a lot stronger wording for us, than the 2 weeks ago event, where there was widespread golf ball to baseball sized hail, and almost zero chance of tornados! Keep an eye to the sky tomorrow !

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18 minutes ago, jrips27 said:

Moderate mainly in south Alabama on the new Day 2.

day2otlk_1730.gif?1491156549692

 


...Eastern MS...AL...Western GA...FL Panhandle...
   A line of severe thunderstorms capable of particularly damaging
   winds and tornadoes will be ongoing at 12Z Monday roughly from
   northwest AL into southern MS. Although the storm mode will be
   mostly linear along the front, embedded circulations and QLCS
   tornadoes are expected given strong shear profiles. In addition,
   discrete supercells may form ahead of the line, especially across
   the Moderate Risk area where instability will be greatest. A few
   strong tornadoes are possible in this corridor.

   There are predictability issues with the initial position of the
   early day storms. If they are farther west than expected, a more
   widespread wind threat could exist farther northwest than currently
   forecast. 

   ...Eastern GA into SC...
   Several models support the idea of supercells forming along the
   returning warm front across eastern GA into western SC during the
   day. Forecast sounding show impressive hodographs supportive of
   supercell tornadoes given the favorable instability profiles. As
   such, have expanded the Enhanced Risk into the region. The ESRL HRRR
   model shows supercells developing around 18Z, moving into central SC
   by late afternoon and evening.

That the second time strong tornadoes have been mentioned as a possibility for the Atlanta metro.  The potential is here for a decent severe event to unfold today and tomorrow for Dixie alley. 

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Obviously everyone knows how to read a forecast discussion, but this one has some pretty "severe" wording, especially for our area.

Quote

Now onto the interesting stuff... Very deep upper low/highly
amplified trough will continue to march across the Plains tonight,
dragging a cold front across the Deep South tomorrow and toward the
Southern Appalachians Monday afternoon. This is an impressive setup
for severe weather, and will just go ahead and start out with the
upgrade to Enhanced on the Day2 outlook for NE GA and most of the
Upstate. Instability increases in the warm sector ahead of the front
starting around noonish tomorrow, with both the NAM and GFS bringing
over 1000 J/kg - significant for our area in the spring - though at
slightly different times (GFS a little faster than the NAM). Deep-
layer shear is impressive with 50-70kt 0-6km as both low-level (40-
50kt southerly) and upper jet (60-80kt SSW to SW) increase. At the
surface, a little mesolow is progged by just about all the guidance
to ride up the prefrontal trough across GA midday Monday, which will
contribute to backing of surface winds across the Upstate during the
afternoon hours. This results in some out of this world helicity
values over over 600 m2/s2 during peak heating tomorrow. Resulting
STPs even on the more conservative GFS are above 3 across the entire
Upstate and NE GA, with even higher values on the NAM. This is a
pretty big deal for the Upstate/Southern Appalachians where these
kinds of parameters aren`t often observed.

Looking at reflectivity and updraft helicity forecasts, it is very
concerning. At the minimum, a squall line with embedded supercells
can be expected, but discrete supercells certainly not out of the
question with a strongly curved hodograph. As the trough digs, upper
jet will bring upper winds around to the S instead of SSW, which
would be more supportive of a squall line. Indeed, the WRF NMM has
BOTH - supercells moving across the area mid-afternoon followed by a
squall line moving through in the evening. Either/both certainly
possible with still some uncertainty in timing, but convective
chances ramp up quickly after noon and into the mid-afternoon hours,
right now peak looks around 21z/5p (rush hour). Widespread damaging
winds, large hail, and tornadoes (cannot rule out isolated strong)
can be expected with these storms tomorrow. Cannot under-emphasize
the importance of going over safety plans especially with kids who
may be home alone tomorrow afternoon.

 

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4 minutes ago, Solak said:

Brad PanovichVerified account @wxbrad 9m9 minutes ago

 
 

Preliminary Futurecast of tomorrow's severe storms and threats. #cltwx #ncwx #scwx #wxaware

C8b7mOwXsAgpNu_.jpg

That doesn't look that special!? When events get overhyped, sometimes they come up a little short on expectations, this case, that's a good thing! It's supposed to be cloudy and drizzly in tomorrow AM, that should limit instability???

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13 minutes ago, mackerel_sky said:

That doesn't look that special!? When events get overhyped, sometimes they come up a little short on expectations, this case, that's a good thing! It's supposed to be cloudy and drizzly in tomorrow AM, that should limit instability???

600 shear value is nearly unheard of for around here so any potential overhype is worth it imho. 

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Some of the signals I'm seeing from various higher res guidance and the SREF are troubling tomorrow across GA. There seems to be potential for either the ongoing MCS from tonight's convection to break up into more discrete elements or for new cells form in the warm sector. Very high shear looks to be present especially near the differential heating boundary in eastern sections where locally backed low level flow will enhance low level SRH. These cells would definitely be capable of higher end severe assuming the morning convection doesn't completely wash the warm sector out (which is still a reasonable scenario mind you). The way the trough accelerates northeastward, shifts negatively tilted with time and positions its axis right over the warm sector is consistent with some of the more potent events here in the past.

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RAH updated HWO

.DAYS TWO THROUGH SEVEN...Monday through Saturday.

A powerful storm system will bring a risk of strong to severe
thunderstorms, mainly Monday evening into the overnight hours of
Tuesday morning. The primary severe threats will be damaging winds
and isolated tornadoes, especially south of Highway 64.

Another storm system may bring a threat of severe thunderstorms to
central NC late Wednesday afternoon and Wednesday evening. The
primary severe weather threats will again be damaging winds and
possibly a few tornadoes.
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Complex forecast tomorrow

Squall line will come through in the morning-very early afternoon and won't provide much of a tornado risk unless the squall line breaks up into discrete cells or has cells develop ahead of it. Looks like there will be some air mass recovery across GA/AL and it won't take much sunshine for there to be substantial instability given LLJ strength. Looks like discrete cells develop after this and provide a decent tornado risk throughout the afternoon/evening for GA/AL/SC. One thing tomorrow has that today didn't is that these cells will be more isolated and spread out over a larger area.   Still a lot of uncertainties if these cells can maintain itself and mature into tornado producing supercells. Parameters are certainly there for significant tornadoes though and will need to be watched closely. Still a possibility the squall line completely ruins the setup and turns it into horse crap and useless garbage. Potential is there for some higher-end severe though including strong tornadoes.

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02z HRRR has 78/69 in Macon tomorrow around 1PM with storms nearby. Some areas of East Georgia get into the 80's.

 

Will be interesting to see the new Day 1 here in a couple of hours. There seem to be quite a few hi-res models picking up on supercells developing in East GA and moving into South Carolina in the mid-afternoon hours. If I had to guess I bet the SPC will extend the moderate risk through GA and into SC to account for this. 

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