Long title, but hopefully it conveys the truth – and not the hype. Right now it looks like the latest data continues to trend northward with the most significant threat for severe weather. That means places south of I-20 may not see as much severe weather as originally anticipated.
Though, that is far from a “in the clear” designation. There is still a chance for storms and severe weather south of I-20. It is just that the threat looks to be higher north of I-20.
From the SPC
The SPC has introduced a Moderate Risk area across parts of Mississippi and Alabama. That is a “4” on the 1-to-5 scale where “5” is the highest risk for the most significant severe weather. The SPC has kept the Enhanced Risk, the “3” on the same scale, in roughly the same area as yesterday. They only shifted it slightly north.
Discussion from the SPC:
…SUMMARY…
A potential outbreak of severe storms including several long track strong tornadoes, large hail and damaging wind will exist Thursday into Thursday evening across a portion of the lower Mississippi Valley and Southeast States.
…Lower Mississippi Valley and Southeast States…
Shortwave trough currently over the Southwest States will move from southern TX early Thursday through the lower MS Valley during the day and into the OH Valley overnight. Thursday morning a cold front will extend from the Great Lakes southwest to a weak surface low in northeast TX, then south into the western Gulf. In response to the ejecting negative-tilt shortwave trough, the cyclone is forecast by some models to undergo significant deepening as it develops northeast during the day. As this occurs, a cold front will accelerate through the lower MS Valley into the Southeast States, while a warm front initially from northeast TX into northern LA, central MS and southwest AL develops northward into the TN Valley.
Some model differences do exist with the NAM being slightly less amplified and more progressive with resulting weaker cyclogenesis. It still appears likely that elevated storms will be in progress at the start of the period within the warm advection regime across northern MS, AL and TN.
This activity is expected to continue lifting northward, allowing for destabilization from the south with time. Rich low-level moisture with upper 60s to near 70 F dewpoints will advect northward through warm sector contributing to moderate instability with up to 2000 J/kg MLCAPE. Discrete storms are expected to develop over the lower MS Valley as the surface layer destabilizes during the afternoon. The low-level jet will strengthen to 60+ kt over the lower MS and TN Valleys in response to forcing within exit region of the migratory mid-upper jet accompanying the shortwave trough.
Vertical wind profiles with very strong shear and large 0-1 km hodographs (0-1 km helicity from 300-400 m2/s2) will support supercells with low-level mesocyclones capable of producing strong tornadoes and large hail. Some bowing structures are also likely. Activity will spread northeast through the lower MS and TN valleys during the day and into the evening. Additional storms may also develop along the cold front with linear structures capable of damaging wind.
A secondary area of thunderstorm development might occur in vicinity of the ejecting vorticity maximum and near and just south of the surface low track from northern AR into southern MO. All hazards will be possible in this region, but threat is more conditional at this time given uncertainty regarding how much destabilization can occur. Will maintain this region in a SLGT for now, but continue to monitor for upgrade to higher probabilities in later updates.
Courtesy: spc.noaa.gov
The Karrie Meter
Looking at Thursday’s setup, the numbers were running in the ~6.5 range from the 12z data on Tuesday. Running the overnight data into Wednesday morning, things looked a bit different:
The average this afternoon was taken from just the “First Four” because we were stilla. bit too far out to get into the “shorter-range” guidance. But now the data can be grabbed from all eight, including the shorter-range models. While the shorter-range models can generally give added insight into a potential outcome by themselves, in this case, since there is now more data to pull from, the addition of the shorter-range guidance to the “First Four” probably gives a better estimate of the true threat.
The interesting part is that the Karrie Meter number came down ~0.4 but the TOR numbers and the ratio is much lower on the shorter-range guidance than the “First Four” numbers.
Here is a look at how the 00z HRRR data suggests things play out:
The 00z HRRR may be running a bit “hot” with the numbers as the 00z NAM data looks a bit less ‘punchy’ for the region.
Again, it is comforting to see shorter-range guidance suggesting a lower overall threat and a lower threat for tornadoes for areas south of I-20.
South Mississippi Breakdown
Looking at the counties of southern Mississippi, here is a county-by-county timeline and breakdown of what to expect on Thursday, given the latest data available on Tuesday night and into Wednesday morning.
NORTHERN COUNTIES
Simpson County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado.
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength).
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Smith County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado.
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength).
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Jasper County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado.
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength).
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Clarke County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado.
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength).
6p-10p – A few severe storms may linger in the area through 7p. After that, isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
HIGHWAY 84 CORRIDOR
Lawrence County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength)
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Jeff Davis County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength)
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Covington County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength)
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Jones County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength)
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Wayne County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength)
6p-10p – A few severe storms may linger through 7p. After that point, isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
HIGHWAY 98 CORRIDOR
Walthall County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength)
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Marion County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength)
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Lamar County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF3 in strength)
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Forrest County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF2 in strength)
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Perry County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF2 in strength)
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
Greene County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF2 in strength)
6p-10p – Isolated storms coming to an end. Followed by a thin line of storms moving through the area during this time. Storms may be strong with heavy rain, some lightning, and gusty wind.
HIGHWAY 26 CORRIDOR
Pearl River County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF2 in strength)
6p-10p – Storms ending
Stone County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF2 in strength)
6p-10p – Storms ending
George County
10a-2p — Passing clouds with isolated storms developing. Strong to marginally severe storms will be possible during this time with heavy rain, frequent lightning, wind gusts up to 60mph, up to dime-sized hail and the potential for a brief tornado
2p-6p — Isolated strong to severe storms possible. Storms may produce heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and a chance for a tornado (up to EF2 in strength)
6p-10p – Storms ending
The Bottom Line
Severe weather still looks possible for the Gulf Coast region of Louisiana, Mississippi and Alabama. a bulk of the severe weather threat looks to be north of I-20, but that doesn’t mean places south of that region are in the clear.
Have a way to get warnings from the NWS on Thursday. Things like a NOAA Weather Radio or an app on your phone set to ping you when a new warning for your area is issued. Or have both!
The timeline for the severe weather threat will be late morning through early evening. And all types of severe weather will be possible: heavy rain, frequent lightning, wind gusts up to 70mph, hail up to the size of golf balls, and tornadoes.
While the worst-of-the-worst may not be in your area, we can’t know for certain at this time who, specifically, will see the most significant severe weather. So it is important to have a plan, just in case ist happens in your area.
