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Severe WX Severe Weather Threat 3/14-3/16

TornadoFan17 said:
Friendly reminder for my folks in the central timezone:

Zulu time is now 5 hours ahead of us with the new time change.

0Z now corresponds to 7pm CT.
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If you're ever unsure, you can always use a site or app like this one! Never hurts to double check your Z time, especially when we change over clocks.
 
cdc15695-712f-42ba-9642-b071ed348cfd.gif

Moisture is disappearing on the GFS because the lead wave is slower on Wednesday. Will likely limit the threat significantly if it continues.
 
All 00z models decreasing moisture for Friday thus far. Pretty obvious what the failure mode here is. Lead wave is faster -> bigger threat, lead wave is slower -> threat decreased substantially.
 
00Z GFS still looks rather nasty for the Deep South, though there is some discrepancy in instability and kinematics. Hopefully this trend continues.
 
Clancy said:
00Z GFS still looks rather nasty for the Deep South, though there is some discrepancy in instability and kinematics. Hopefully this trend continues.
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0z GFS shows less convective contamination from Friday and Friday night when heading into Saturday morning because of the delayed moisture on Friday and resultant less in the way of convective coverage. That is leading to the model showing more robust instability for Saturday. The 0z GFS is also slower with the development of the secondary low-level jet max over Alabama on Saturday compared to previous runs, but still has it fully in place going into the peak of daytime heating. If the trend to more delayed moisture return Friday is where this is really headed, I could see a situation where this ultimately leads to the more impactful day possibly being Saturday across the Deep South and Tennessee Valley instead of Friday to the west. There has been a seasonal trend for these systems to be more aggressive off to the east of the original outlook higher risk areas and for these systems to be more squarely aimed over here in this area. I wouldn't be shocked in the slightest if that is how this ultimately plays out...
 
Fred Gossage said:
0z GFS shows less convective contamination from Friday and Friday night when heading into Saturday morning because of the delayed moisture on Friday and resultant less in the way of convective coverage. That is leading to the model showing more robust instability for Saturday. The 0z GFS is also slower with the development of the secondary low-level jet max over Alabama on Saturday compared to previous runs, but still has it fully in place going into the peak of daytime heating. If the trend to more delayed moisture return Friday is where this is really headed, I could see a situation where this ultimately leads to the more impactful day possibly being Saturday across the Deep South and Tennessee Valley instead of Friday to the west. There has been a seasonal trend for these systems to be more aggressive off to the east of the original outlook higher risk areas and for these systems to be more squarely aimed over here in this area. I wouldn't be shocked in the slightest if that is how this ultimately plays out...
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Really good points! In any of the cases we've seen modelled, Deep South states will have to be particularly watchful, and there's definitely a tendency for events to surprise us on the eastern flanks.
 
Well the Euro/UK combo didn't back down much from the Arklatex/Mid South threat on Friday. Both are essentially regional outbreaks.
 
06z GFS not as favorable as the 18z yesterday. But it's still a bad look. The CAPE is actually more impressive over Alabama than the 12z yesterday. It's the bonkers shear that is not as much as it was in that run that's hampering things in the 06z. But nonetheless, a likely very bad event will still occur on the 06z. A 30% is warranted like the guys at SPC put down. Dangerous couple of days at the end of the week.
 
Latest mid-range disco sounds like bad news.
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0354 AM CDT Mon Mar 10 2025

Valid 131200Z - 181200Z

...DISCUSSION...
...Day 4/Thu - Southeast...

A shortwave upper trough will move across the Southeast on Thursday.
Stronger deep-layer flow will mainly be focused over the Gulf.
However, cooler temperatures aloft will support weak instability and
a strong storm or two may occur over portions of AL/GA and the FL
Panhandle. Overall severe potential appears limited.

...Day 5/Fri - ArkLaTex to the Mid/Lower MS Valley vicinity...

A regional outbreak of severe storms is forecast late Friday
afternoon into the overnight hours. An intense upper cyclone will
deepen as it ejects northeast from the central/southern Plains to
the Upper Midwest by Saturday morning. A 100+ kt 500 mb jet streak
will move across OK into the Ozark Plateau during the late afternoon
and evening, before lifting north across the Mid-MS Valley
overnight. At the surface, a rapidly deepening surface low will move
across the central Plains to the Upper Midwest, with a cold front
surging east across the region from late afternoon into Saturday
morning.

Deeper Gulf moisture will be confined to the I-20 corridor Friday
morning. However, intense low-level flow will quickly transport
moisture northward through the mid-MS Valley. Surface dewpoints
greater than 60 F will likely remain south of the MO Bootheel
vicinity, with a broader area of more modest moisture as far north
as northeast IA/southwest WI and northern IL. While moisture will be
less favorable with northward extent, strong large-scale ascent,
intense deep-layer flow and a surging cold front will likely be
sufficient for severe convection even amid weak instability. Further
south from the ArkLaTex vicinity to the Lower MS Valley, better
quality moisture is expected to overlap intense shear. Overall, this
pattern will support all severe hazards, with a potential mixed mode
evolution (QLCS and supercells).

The north and east extent of severe potential remains a bit
uncertain either due to moisture concerns and/or spread among
various guidance in timing and position of key features. Severe
probabilities will likely be refined over the coming days as these
features become better resolved.

...Day 6/Sat - Southeast...

The Upper Midwest cyclone will eject northeast into Ontario on
Saturday. Meanwhile the base of the larger-scale upper trough over
the Plains ejects east toward the Lower MS Valley and Southeast.
This will maintain strong deep-layer southwesterly flow across the
region, with an intense low-level jet expected to develop by late
afternoon as stronger height falls overspread the Deep South.
Ongoing convection at the beginning of the period from the Lower OH
Valley toward northern MS/LA adds some uncertainty regarding how the
airmass will destabilize (especially with northward extent).
However, it appears likely that a very favorable corridor of rich
boundary layer moisture will overlap strong shear from
central/southern MS into northern AL ahead of a cold front expected
to surge across the area during the evening. This overall pattern
appears favorable for both supercells and an eventual QLCS.

...Day 7/Sun - Eastern states...

The upper trough over the central U.S. will lift northeast over the
eastern states on Sunday. Some severe potential is possible given
strong deep-layer flow atop a moist boundary layer ahead of the
eastward-advancing cold front. However, destabilization may be
limited by widespread training precipitation.

..Leitman.. 03/10/2025
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