Severe Weather 12-29-21 and 1-1-22

[cheese007]

Looks like at least one more chance for severe weather in 2021 coming soon:

...D5/Wed - Northern Mississippi, northern Alabama, and vicinity...
   Prior to D5, the warm sector moisture has been contaminated by
   continental air which has led to weak instability across much of the
   warm sector. However, by Tuesday night, a true maritime tropical
   moisture feed is forecast to overtake the western Gulf of Mexico.
   Persistent southerly flow will advect this airmass inland from
   eastern Texas to northern Mississippi/Alabama by Wednesday
   afternoon. Moderate instability should develop south of a front,
   which is expected to be in place from eastern Texas into the
   Tennessee/Ohio Valley region. There is decent model agreement with
   the increasing low-level moisture and the relative position of the
   surface front. However, the upper-level pattern does cast more
   uncertainty on the forecast. 

   The details of any severe weather threat will come from the
   evolution of the low-amplitude wave to eject from the larger scale
   western CONUS upper-level trough. Predictability of the
   timing/amplitude of upper-level troughs such as these is inherently
   challenging, especially at Day 5. Therefore, it is unsurprising that
   there is still considerable spread between available mid-range model
   guidance. The last 2 runs of the ECMWF have shown a more amplified
   mid-upper level trough which would initiate a greater low-level mass
   response and likely lead to a greater severe-weather threat. 

   Therefore, uncertainty remains regarding the evolution, timing, and
   amplitude of the upper-level pattern on Wednesday. However, there
   has been a consistent signal for surface-based storms in an
   environment with moderate buoyancy and strong shear for several
   days. The aforementioned arrival of a maritime tropical airmass in
   the vicinity of a surface front and at least weak height falls aloft
   is consistent with at least scattered storm development. Therefore,
   confidence is high enough to introduce 15 percent severe
   probabilities for Wednesday.

   ..Bentley.. 12/25/2021

[cheese007]

Image description: SPC 15% contour covering far southeastern Arkansas, far northeastern and central Louisiana, most of Mississippi, and a significant portion of western Alabama

[cheese007]

D3 slight risk for areas listed above and D5 15% covering a similar area with the addition of more of Arkansas and Louisiana, portions of middle and western Tennessee, Missouri bootheel, and south-central Kentucky 

[nwohweather]

Might get a little busy on this thread here today

[nwohweather]

That environment is gonna pop off at 3-4 Central here. I’d be real worried in N MS today, strong LLJ with little CIN and ample instability

[Derek30]

Starting to unzip in portions of AR and far N LA. That Haynesville cell just went severe warned.

[nwohweather]

Tons of shear aloft and decent SRH, but looks like some solid CIN is really putting the lid on this evening. Just nothing really taking off despite a Tornado Watch that is cautioning for even intense tornadoes. I’m just not seeing it here

[Witness Protection Program]

3 tornado warnings for south Georgia at the moment.

 

[brianc33710]

I think that we probably need to rename this thread from 12-29-21 and 1-1-21 to 12-29-21 and 1-1-22. 

[cheese007]

NYD threat upgraded to ENH for sig tors

[buckeyefan1]

4 hours ago, cheese007 said:

NYD threat upgraded to ENH for sig tors

Day 2 Convective Outlook CORR 1
   NWS Storm Prediction Center Norman OK
   0114 AM CST Fri Dec 31 2021

   Valid 011200Z - 021200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
   OF THE DEEP SOUTH AND TENNESSEE VALLEY....

   CORRECTED FOR SIGNIFICANT TORNADO LINE TYPE

   ...SUMMARY...
   Widespread thunderstorms are expected from the ArkLaTex to the
   Western Appalachians on New Year's Day. All severe-weather hazards
   are possible including large hail, damaging winds, and tornadoes, a
   couple of which may be strong.

   ...Synopsis...
   A positively tilted upper-level trough will be centered near the
   Great Basin to start the period. This trough will maintain its
   positive tilt as it shifts eastward across the Plains and into the
   Midwest by 12Z Sunday. An embedded mid-level shortwave trough will
   move quickly from the southern High Plains across the Midwest and
   Ohio Valley Saturday to the Northeast by Sunday morning. A surface
   reflection of this mid-level shortwave trough is expected to travel
   along the front from the Ozarks to the Ohio Valley and into the
   Mid-Atlantic.

   ...Ohio Valley into the central Appalachians...
   There is still considerable uncertainty regarding the northward
   extent of the destabilization and severe-weather threat based on the
   position of the position of the surface front and the strength of
   the surface low. The NAM is stronger with the surface low with a
   much farther north warm front bringing low 60s dewpoints north of
   the Ohio River into southern Illinois, southern Indiana, and
   Southwest Ohio. However, the operational GFS is much weaker and
   southeast with the surface low and only brings low 60s dewpoints
   into south-central Kentucky. The ECMWF solution is between these two
   locations with the frontal position, which also closely resembles
   the GEFS mean. Therefore, the northern extent of the marginal and
   slight risk threat areas match the ECMWF and GEFS mean. 

   A line of storms is expected to move through this region during the
   afternoon and early evening hours. Forecast soundings show more than
   50 knots of flow only a few hundred meters above the surface.
   Therefore, mixing this strong flow to the surface should not be that
   difficult, even in a weak buoyancy environment. Low 60s dewpoints
   should yield MLCAPE around 250 to 500 J/kg across southern Kentucky,
   which increases the confidence for severe winds as the squall line
   moves through. In addition, a QLCS tornado threat will exist given
   the strong low-level speed shear present ahead of this line of
   storms. However, the limited instability and veered surface flow
   will be limiting factors to a greater tornado threat along this
   portion of the line. 

   ...Portions of the Deep South into the Tennessee Valley...
   A large area of thunderstorms, some of which may be severe, is
   expected to be ongoing from western Kentucky to northern Texas
   Saturday morning. As the surface low moves from the Plains into the
   Ozarks Saturday morning, this convection is expected to become
   better organized, likely into a squall line, and start to advance
   eastward. Dewpoints are forecast in the mid to upper 60s ahead of
   these storms, which should yield MLCAPE around 500 to 1500 J/kg from
   north to south. This should be more than sufficient to maintain a
   strong squall line through the afternoon and into the overnight
   hours across eastern Arkansas, most of Tennessee, and northern
   Mississippi and Alabama. A 50 to 60 knot low-level jet will result
   in strong low-level speed shear across the entire warm sector.
   Forecast soundings show mostly unidirectional flow in the lowest 1
   km due to the veered surface flow across most of the warm sector as
   a result of the elongated nature of the surface pressure pattern.
   This should temper the tornado threat somewhat, but with the strong
   speed shear and the expectation of a well balanced squall line, the
   environment will still be supportive for QLCS tornadoes. 

   Most guidance hints at the potential for some warm sector supercell
   development across portions of Mississippi, Alabama, and Tennessee
   Saturday afternoon/evening. The ECMWF has been especially bullish
   with pre-frontal convection for the last several days, which
   continues through the latest 00Z run. Any strong supercells which
   can develop in the open warm sector will likely have the greatest
   threat for significant to potentially intense tornadoes. The most
   likely region for pre-frontal supercell development will be from
   eastern Arkansas to northern Alabama and possibly southern Tennessee
   where greater instability is forecast. Veered low-level flow will
   keep low-level directional shear limited during the first half of
   the day. However, at least slightly greater low-level turning is
   shown by forecast soundings during the late afternoon into the
   evening hours as surface flow remains south-southwest, while the
   low-level jet starts to veer more westerly as the main wave shifts
   east. This may result in a slightly higher tornado threat into the
   overnight hours from far eastern Mississippi into northern/central
   Alabama and northwest Georgia.

   ..Bentley.. 12/31/2021

[brianc33710]

So they may go Moderate if convection doesn't overwhelm the dynamics & makes these areas "messy."

[brianc33710]

WOW! Bham 77 temp 70 dewpoint! This would be impressive for Tampa Bay today! But the best dynamics appear to be NW of us. Happy 2022 everyone while I'm at it. 

[CheeselandSkies]

Slight risk upgrade for 1/2 including most of GA, NW FL, SE AL, and the Carolinas.

[buckeyefan1]

53 minutes ago, CheeselandSkies said:

Slight risk upgrade for 1/2 including most of GA, NW FL, SE AL, and the Carolinas.

The hrrr has shown a few rotating cells the past few runs 

[nwohweather]

2 hours ago, buckeyefan1 said:

The hrrr has shown a few rotating cells the past few runs 

Orangeburg wouldn’t be a bad place to post up today