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jaxjagman

Tn Valley Severe Weather

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This regional forum was created to separate the NE GA and the Carolinas from the west side of the Apps as it is generally two different discussions when it comes to winter weather. There are no definitive lines for weather in Alabama/Mississippi etc for discussion in here. That discussion is welcome and was evident in the last snow that came through MS...we just happen to have more active TN Valley posters than the rest of this side of the Apps...

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The flashes of lightning and the sounds of thunder Monday evening were particularly sweet! I feel like last thunder was early this fall, creating a longer than usual wait. Also...

First thunder after the new year is always nice; but, I felt extra content this year. Almost a feeling of peace, tbh. Why those descriptions? It has been a trying ten and a half months so far with the pandemic, damaging tornadoes* and not chasing much last year. Lightning and thunder felt like a preview of a possibly (hopefully likely) more normal spring and summer.

*While I'm interested in severe, high impact tornadoes are a turn-off. I'm hoping spring 2021 offers safe chase days in Dixie, and a Plains season later.

For some thunder Monday brought snow Wednesday! Does that count? 

Anyway we are flexible on severe wx. Birmingham tornado was late and nobody was watching. By morning Twitter had it. Then TLH is Southeast.

If it's not middle of the night we'll talk about North Alabama, most of Mississippi and southern Kentucky. Huntsville and Muscle Shoals, AL are definitely Tennessee Valley. We sometimes go as far west as the Delta and south as Birmingham.

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25 minutes ago, AMZ8990 said:

Had some lighting strikes in Hardeman county tonight, decent little cell pushed through around dinner.  All rain now

Heard a few rumbles here a few minutes ago 

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If tomorrow is what some of these short range models are showing, it should be a active day if you like severe.

 

Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1125 AM CST Sat Feb 27 2021

   Valid 281200Z - 011200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
   THE SOUTHERN PLAINS INTO THE LOWER MISSISSIPPI VALLEY AND OHIO
   VALLEY...

   ...SUMMARY...
   Isolated strong to severe thunderstorms appear possible from parts
   of Texas into the Ohio Valley on Sunday. Damaging wind gusts should
   be the main hazard, but some hail and a couple tornadoes may also
   occur.

   ...Southern Plains into the Lower Mississippi and Ohio Valleys...
   Multiple mid-level shortwave troughs will move eastward across the
   CONUS on Sunday. One such shortwave trough is forecast to advance
   from the northern Plains and Upper Midwest to the Great Lakes by
   Sunday evening. Another shortwave trough should develop slowly
   southeastward from the Great Basin to the Southwest, eventually
   closing off over AZ/NM late Sunday night. The primary surface low is
   expected to develop northeastward across the Upper Midwest/Great
   Lakes and into southern Ontario by Sunday evening, in tandem with
   the previously mentioned shortwave trough. A cold front extending
   southward from this low should be located over parts of the lower OH
   Valley into the Mid-South and southern Plains Sunday morning. This
   cold front will shift slowly southeastward through the period across
   these regions, and it will likely provide a focus for convection.

   A fairly broad swath of enhanced mid-level southwesterly winds
   should overlie the frontal zone, but stronger forcing associated
   with both shortwave troughs is likely to remain north of the warm
   sector. Still, forecast soundings from northeast TX into the lower
   MS Valley/Mid-South and continuing into parts of KY indicate a
   veering and strengthening wind profile with height through mid
   levels. Upwards of 50-60+ kt of effective bulk shear appears likely,
   which is clearly sufficient for organized storms, including
   supercells. However, two potentially limiting factors remain
   apparent. One is the orientation of the front nearly parallel with
   the southwesterly mid-level flow. Tendency may be for storms to form
   along the front and then get quickly undercut while becoming
   elevated. The other limitation may be generally weak low/mid-level
   lapse rates and related modest instability. Even so, the presence of
   surface dewpoints generally in the 62-68 F range coupled with some
   diurnal heating south of the front should support MLCAPE around
   250-1000 J/kg by Sunday afternoon.

   Current expectations are for mainly elevated storms to be ongoing
   across parts of the lower OH Valley Sunday morning in a strong
   low-level warm advection regime. Additional convective development
   appears likely along much of the length of the cold front by late
   Sunday morning or early afternoon. Short bowing line segments may
   pose an isolated damaging wind threat as they move
   east-northeastward. Even though low-level flow should tend to veer
   to southwesterly across much of the warm sector through the day,
   enough low-level shear may remain to pose a threat for a couple
   tornadoes with either semi-discrete storms or circulations embedded
   within the line segments. Eventually, this isolated severe threat
   should wane across the lower MS Valley and TN Valley Sunday evening
   as storms become mainly elevated behind the front. Finally, some
   hail threat may exist with elevated storms both Sunday morning and
   Sunday night across parts of TX into the ArkLaTex vicinity.
   Mid-level lapse rates should be modestly steepened across this
   region in advance of the shortwave trough over the Southwest, and
   deep-layer shear will likely be rather strong and uni-directional,
   potentially supporting elevated supercells.

   ..Gleason.. 02/27/2021

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National Weather Service Nashville TN
330 PM CST Sat Feb 27 2021

.DISCUSSION...

Went with a blended model solution through next Saturday
afternoon. Good initialization and generally good
solution agreement. Big player in this potential significant
rainfall event unfolding across mid state region through early
Monday will still be a surface warm front moving well north
of mid state region tonight, shifting heavier rain axis up into
Ohio Valley. Trailing this warm front is a cold front that will
drop into mid state region later Sunday, and then work south of
our area overnight. Late Sunday/Sunday night will be our biggest
threat of flooding as most of expected rainfall will come during
that period and some river flooding possibly continuing well
through next work week. Severe parameters also a bit enhanced for
Sunday afternoon into Sunday evening across our area. Afternoon
high temps on Sunday expected to sore into mid 70s south with a
good amount of instability and favorable lapses rates for strong
to severe convection development, especially if rainfall does not
move into this portion of mid state region until late afternoon
hours allowing for increased atmospheric instability due to
enhanced diurnal heating influences. SPC has placed entire mid
state region in a marginal risk during Sunday afternoon through
Sunday evening time frame. Still looks like all this rain will
end as Monday morning hours progress. Past and future QPF have
been quite consistent over the previous few model runs giving
our area a total rainfall event of 2-4 inches, with isolated 4+
inches possible. Thus a Flood Watch continues from 12Z Sunday
through 12Z Monday for most of mid state region expect south
central and southeast counties where lesser amounts are expected.

This developing weather pattern will result in unseasonably warm
lows are tonight as low level warm air advection becomes
increasingly established. Lows tonight will actually be higher
than seasonal normal high temperatures! Lows tonight will range
upper 50s north to lower 60s south. Highs on Sunday will range
from upper 60s north to mid 70s south. Lows Sunday night will fall
into low to mid 40s as surface frontal passage occurs. As a
cold air advection pattern from our north settles into mid state
region as Monday progresses, highs will be actually a few degrees
cooler than seasonal normal values generally in lower 50s.

Following this system, potential of scattered showers will
continue across mid state region through Tuesday night as now
both latest GFS/ECMWF solutions move a system across mid state
region as Tuesday night progresses. Dry conditions should finally
prevail across our area Wednesday through Thursday afternoon
as upper level ridging influences build across mid state region.
Also noted is now better agreement between latest GFS/ECMWF
solution as next weekend approaches. However will still
maintain forecast consistency with mentioning just a chance of
showers across mid state region Thursday night through Friday
night.

Temperatures are expected to stay around seasonal normal values
Tuesday through next Saturday afternoon. Maybe some wintry
precipitation mix working in during Tuesday and Wednesday morning
hours, but no significant accumulations expected. Mid state
continues to get a break from Old Man Winter!
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Rut roh Rorge (from MRX):

 Within this high shear, low CAPE environment, there will be a very low chance
of a QLCS tornado within the convective line across our western
and southwestern counties on tonight. While the risk of a QLCS
tornado is very low, it is a risk that will need to be considered
and monitored closely tonight.

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 Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1144 PM CST Sat Feb 27 2021

   Valid 281200Z - 011200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE ARKLATEX
   TO MIDDLE TENNESSEE...

   ...SUMMARY...
   Strong to severe thunderstorms are likely from parts of Texas into
   Middle Tennessee on Sunday. Damaging wind gusts and a few tornadoes
   should be the main hazards, but some large hail may also occur.

   ...Synopsis...
   Several mid-level shortwave troughs are embedded within a larger
   trough across the central CONUS. A stronger shortwave will move
   through the Upper Midwest/Great Lakes through the day. A compact
   shortwave will develop into a closed low across the Southwest
   throughout the day while several weaker perturbations will move
   through moderate southwesterly flow extending from the Southern
   Plains to the Ohio Valley. At the surface, an area of low pressure
   will begin the day in Iowa before deepening as it moves
   northeastward into the Great Lakes. As this surface low strengthens,
   a cold front will sharpen and advance southeastward from the Midwest
   to the southern Plains. Numerous thunderstorms, some severe, are
   expected along and ahead of this cold front.

   ...Southern Plains to the Ohio Valley...
   A shortwave trough seen on Water Vapor across northern Mexico early
   this morning will move quickly northeastward through the morning.
   Weak ascent associated with this mid-level shortwave is expected to
   overspread a moist and unstable warm sector across
   north-central/northeast Texas and southeast Oklahoma this morning
   which will likely initiate scattered convection. Supercells are
   possible given moderate instability (1000-1500 J/kg), steep
   mid-level lapse rates (~7.5 C/km) and effective shear around 65 kts.
   All severe weather hazards will be possible with these early storms.
   This includes the potential for a tornado or two given the moderate
   low-level shear.

   Temperatures ahead of the cold front are expected to increase into
   the low 70s with dewpoints in the low to mid 60s from the southern
   Plains as far northeast as southwest Kentucky by mid afternoon. This
   should yield MLCAPE around 1000 to 1500 J/kg from the southern
   Plains northeastward to far southern Kentucky. This destabilization
   of the air mass, combined with the tightening low-level frontal
   circulation should support widespread storm development along the
   front by early to mid afternoon. Storms may initially struggle to
   become severe due to some warmer temperatures near 700mb and the
   propensity for storms to initially move to the cool side of the
   boundary and become elevated. However, through time, storms are
   expected to grow upscale into a forward propagating MCS.

   This line of storms will likely pose a threat for damaging winds
   given the strong low-level flow and a broad region of weak to
   moderate instability downstream. 00Z CAM guidance suggests the most
   robust linear segments may occur from northeast Arkansas into
   western Tennessee where height falls and cooling temperatures aloft
   may assist in stronger updraft development. Low level flow is
   expected to increase above 40 knots at 0.5 km in this region which
   will support a greater threat for severe wind and a favorable
   low-level shear profile for potentially a few tornadoes embedded
   within the line. By late evening, instability is expected to weaken
   substantially which will likely support the line weakening by the
   early overnight hours.

   ...South Texas...
   A few storms are expected to form late in the period (after 07Z)
   near the Edwards Plateau and move eastward. Moderate instability
   (1500 to 2000 J/kg) is expected in this region with steep mid-level
   lapse rates around 8 C/km. Supercells will be the likely storm mode
   given effective shear around 60 to 65 knots. Low level flow will
   remain quite weak and thus large hail will be the primary threat
   with this activity.

   ..Bentley/Darrow.. 02/28/2021

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Tornado Watch

TORNADO WATCH OUTLINE UPDATE FOR WT 13
NWS STORM PREDICTION CENTER NORMAN OK
220 PM CST SUN FEB 28 2021

TORNADO WATCH 13 IS IN EFFECT UNTIL 1000 PM CST FOR THE
 FOLLOWING LOCATIONS

TNC005-017-021-023-033-037-039-043-045-047-053-055-069-071-075-
077-079-081-083-085-095-097-099-101-109-113-117-119-125-131-135-
147-157-161-165-167-181-183-187-010400-
/O.NEW.KWNS.TO.A.0013.210228T2020Z-210301T0400Z/

TN
.    TENNESSEE COUNTIES INCLUDED ARE

BENTON               CARROLL             CHEATHAM
CHESTER              CROCKETT            DAVIDSON
DECATUR              DICKSON             DYER
FAYETTE              GIBSON              GILES
HARDEMAN             HARDIN              HAYWOOD
HENDERSON            HENRY               HICKMAN
HOUSTON              HUMPHREYS           LAKE
LAUDERDALE           LAWRENCE            LEWIS
MADISON              MARSHALL            MAURY
MCNAIRY              MONTGOMERY          OBION
PERRY                ROBERTSON           SHELBY
STEWART              SUMNER              TIPTON
WAYNE                WEAKLEY             WILLIAMSON
$$


ATTN...WFO...LZK...OHX...MEG...LMK...PAH...
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2 minutes ago, Calderon said:

This cell is on a precarious path, to say the least. Directly at Nashville.


.

How bizarre,it was around this time last year when tonadoes struck

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 URGENT - IMMEDIATE BROADCAST REQUESTED
   Severe Thunderstorm Watch Number 15
   NWS Storm Prediction Center Norman OK
   810 PM EST Sun Feb 28 2021

   The NWS Storm Prediction Center has issued a

   * Severe Thunderstorm Watch for portions of 
     Far south-central Kentucky
     Middle Tennessee

   * Effective this Sunday evening from 810 PM until 1100 PM EST.

   * Primary threats include...
     Scattered damaging wind gusts to 70 mph possible
     A tornado or two possible

   SUMMARY...Cluster of strong to severe storms may produce damaging
   winds and a brief tornado before it weakens later this evening.

   The severe thunderstorm watch area is approximately along and 40
   statute miles north and south of a line from 80 miles west of
   Crossville TN to 20 miles northeast of Crossville TN. For a complete
   depiction of the watch see the associated watch outline update
   (WOUS64 KWNS WOU5).
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Weekend was interesting along an east-west boundary. Thankfully it' didn't March 2-3, 2020 again.

Mid-Range the weekly models have shown that trough west with low SER look mid-month; and, operational models are similar now in the 11-15 day period. Weeks 2-3 are the edge of any forecast value; but, it's nice they agree. Forecast AO/NAO is positive. Bering Sea ridge (not Alaska) could anchor the downstream Rockies to Plains trough. Get thunderstorms going Mid-South to Ohio Valley?

Severe Season overall I'm somewhat bullish, but not crazy lit. I see La Nina hanging in there. It's not a pure La Nina resurgence since it's still first year, but it has that bullish lean for severe. Recent MJO activity and Kelvin wave placement in the Tropical Pacific has juiced the La Nina status (esp 3.4 region). +TNI is in question. Right off South America (region 1&2) is still cool. It had been warning up; but, the said activity impacted the whole basin. If 1&2 can warm to near or above normal, while 3.4 stays cooler than normal, then we have +TNI flavor. Either are bullish. Missing one should not be bearish if the other holds.

Finally got a chance to compare La Nina flavors, and I think this year is closer to 2012 and 2008 than 2011. The latter was a true resurgent La Nina second year, strongest correlation with severe; but, we are still first year. However 2021 looks more active than 2017 or 2018, weaker or weakening La Ninas. 2021 is La Nina hanging in, not technically resurgent, but holding well.

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29 minutes ago, nrgjeff said:

Weekend was interesting along an east-west boundary. Thankfully it' didn't March 2-3, 2020 again.

Mid-Range the weekly models have shown that trough west with low SER look mid-month; and, operational models are similar now in the 11-15 day period. Weeks 2-3 are the edge of any forecast value; but, it's nice they agree. Forecast AO/NAO is positive. Bering Sea ridge (not Alaska) could anchor the downstream Rockies to Plains trough. Get thunderstorms going Mid-South to Ohio Valley?

Severe Season overall I'm somewhat bullish, but not crazy lit. I see La Nina hanging in there. It's not a pure La Nina resurgence since it's still first year, but it has that bullish lean for severe. Recent MJO activity and Kelvin wave placement in the Tropical Pacific has juiced the La Nina status (esp 3.4 region). +TNI is in question. Right off South America (region 1&2) is still cool. It had been warning up; but, the said activity impacted the whole basin. If 1&2 can warm to near or above normal, while 3.4 stays cooler than normal, then we have +TNI flavor. Either are bullish. Missing one should not be bearish if the other holds.

Finally got a chance to compare La Nina flavors, and I think this year is closer to 2012 and 2008 than 2011. The latter was a true resurgent La Nina second year, strongest correlation with severe; but, we are still first year. However 2021 looks more active than 2017 or 2018, weaker or weakening La Ninas. 2021 is La Nina hanging in, not technically resurgent, but holding well.

Very interesting pair of analogs because those years behaved very differently during the spring and summer here in the upper Midwest. Very wet/stormy with numerous tornadoes and widespread flooding problems ('08) vs. exceedingly warm and dry ('12).

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11 hours ago, nrgjeff said:

Weekend was interesting along an east-west boundary. Thankfully it' didn't March 2-3, 2020 again.

Mid-Range the weekly models have shown that trough west with low SER look mid-month; and, operational models are similar now in the 11-15 day period. Weeks 2-3 are the edge of any forecast value; but, it's nice they agree. Forecast AO/NAO is positive. Bering Sea ridge (not Alaska) could anchor the downstream Rockies to Plains trough. Get thunderstorms going Mid-South to Ohio Valley?

Severe Season overall I'm somewhat bullish, but not crazy lit. I see La Nina hanging in there. It's not a pure La Nina resurgence since it's still first year, but it has that bullish lean for severe. Recent MJO activity and Kelvin wave placement in the Tropical Pacific has juiced the La Nina status (esp 3.4 region). +TNI is in question. Right off South America (region 1&2) is still cool. It had been warning up; but, the said activity impacted the whole basin. If 1&2 can warm to near or above normal, while 3.4 stays cooler than normal, then we have +TNI flavor. Either are bullish. Missing one should not be bearish if the other holds.

Finally got a chance to compare La Nina flavors, and I think this year is closer to 2012 and 2008 than 2011. The latter was a true resurgent La Nina second year, strongest correlation with severe; but, we are still first year. However 2021 looks more active than 2017 or 2018, weaker or weakening La Ninas. 2021 is La Nina hanging in, not technically resurgent, but holding well.

SPC today almost shows a basin wide moderate NINA,but the SOI is acting like this is a more ELNino the last few days,been awhile since it went negative,the SOI

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I was playing with my new toy above.

CFS looks active in the Pacific upcoming.Sure this will change  some but the models will probably struggle with the upcoming pattern.GFS is already trying to hint at bulding another  Sub-Tropical ridge into the GOM.But this time frame should be our best shot upcoming at some possible severe weather.

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CFS is  showing another EKW the next couple days getting into 1+2,the last one that went through a few days ago has warmed this region up pretty good recently.

 

 

 

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Time to tee it up! Just kidding, gotta do the basketball March Madness first.

Monday could be a thing in the Tennessee Valley iff everything happens just right - which is not progged attm. SPC gives us a mention for Monday but no graphic. LLJ may be quickly weakening as main kinematic and short-wave energy ejects north into Hoosier Alley, which looks too stable. Still be the boundary will be here and wind at / above 500 mb, but that's junk without a proper LLJ.

Looks like a cool period starting middle to late next week after the main trough and all the surface lows. Then late March is anybody's game.

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23 hours ago, nrgjeff said:

Time to tee it up! Just kidding, gotta do the basketball March Madness first.

Monday could be a thing in the Tennessee Valley iff everything happens just right - which is not progged attm. SPC gives us a mention for Monday but no graphic. LLJ may be quickly weakening as main kinematic and short-wave energy ejects north into Hoosier Alley, which looks too stable. Still be the boundary will be here and wind at / above 500 mb, but that's junk without a proper LLJ.

Looks like a cool period starting middle to late next week after the main trough and all the surface lows. Then late March is anybody's game.

Definite not seeing nothing consistent  with the models

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Models have converged in the last 36 hours of runs. Did you see the GFS/EC divergence Monday?

On 3/9/2021 at 2:42 PM, jaxjagman said:

Definite not seeing nothing consistent  with the models

SPC just refused to add Monday. Plains snobs dissin' Dixie, lol! However Monday does have problems. Trough ejecting north, pulling away the best kinematics. Also instability is meh, but that's March. Also if the LLJ does try to recover with the southern-stream short wave, Monday will go. Wednesday is a possibility too, but will focus on Monday now.

After next week looks like a quiet period. Ensembles and weeklies BN temps Southeast but warm North. That says, wake me up after the Final Four. I'll stay up if Kansas or Tennessee do well, lol!

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