tn discuss
Office: MEG
FXUS64 KMEG 061152
AFDMEG
Area Forecast Discussion
National Weather Service Memphis TN
652 AM CDT Mon May 6 2024
...New AVIATION...
.SYNOPSIS...
Issued at 522 AM CDT Mon May 6 2024
Shower and thunderstorm chances are expected to become isolated
into this afternoon as an upper-level disturbance moves away from
the Lower Mississippi Valley. An active period of weather is
expected for Tuesday into Wednesday night as a series of troughs
move through the Mississippi and Ohio Valleys. Severe
thunderstorms are possible Tuesday afternoon into Tuesday evening,
and especially Wednesday night. Cooler and drier air is
anticipated for the upcoming weekend.
&&
.DISCUSSION...
(Today through Sunday)
Issued at 522 AM CDT Mon May 6 2024
GOES-16 satellite this morning show the remnants of an MCV
centered near St. Louis. Nocturnal convection developed near the
nose of a 35 kt low level jet. This resulted in strong to severe
thunderstorms and heavy rainfall overnight especially over north
Mississippi where a corridor of instability between 1000-1500 J/kg
and 35 kts of shear existed. Convective activity has since waned
over the past hour with showers and thunderstorms located over
north Mississippi and portions of West Tennessee near the
Tennessee River. Strong to severe thunderstorms through mid-week
remain the primary concern in this morning's forecast issuance.
Short-term models suggest rain chances will gradually diminish
today in wake of the overnight convection as the atmosphere
stabilizes somewhat. Some CAMs indicate the potential for some
isolated showers and thunderstorms this afternoon. However,
confidence in occurrence and coverage remains low at this time as
shortwave ridging builds in across the Mid-South.
Additional showers and thunderstorms are expected to develop
across the Central and Southern Plains tonight as a mid-level
trough becomes negatively tilted and moves into the Middle
Mississippi Valley. This upstream activity is anticipated to
weaken as it moves towards the Mid-South late tonight into a
somewhat stable atmosphere. Instability is expected to increase
into Tuesday afternoon/evening with redevelopment of showers and
thunderstorms expected especially east of the Mississippi River.
The aforementioned surface-based instability combined with moderately
steep mid-level lapse rates and deepening shear suggest a
potential for strong to severe thunderstorms with large hail and
damaging winds as the main threats.
Confidence continues to increase with the potential for organized
severe thunderstorms across the Mid-South Wednesday into Wednesday
night as a shortwave mid-level trough rotates around an upper-
level low through the Middle Mississippi and Ohio Valleys.
Meanwhile, a surface low is expected to move across northeast
Missouri and northern Illinois. Favorable upper-level divergence
produced by the left exit region of a sub-tropical jet and perhaps
the right exit region of the polar jet combined with deep
directional and speed shear, very steep mid-level lapse rates, and
strong instability favor the potential for large hail, damaging
winds, and tornadoes. Colorado State University machine learning
guidance and St. Louis University CIPS analogs support the
potential for organized severe weather across the Ohio Valley and
Mid-South Wednesday afternoon and Wednesday night. At this time,
it appears the greatest threat for severe thunderstorms across the
forecast area will be Wednesday night as a capping inversion may
be in place across much of the Mid-South. This potential severe
weather event will be closely monitored over the next couple of
days. Stay tuned...
Long-term models indicate some residual showers and thunderstorms
will be possible on Thursday with cooler and drier air filtering
in for Friday into the upcoming weekend.
CJC
&&
.AVIATION...
(12Z TAFS)
Issued at 642 AM CDT Mon May 6 2024
An upper level disturbance is currently pivoting through the
region. A lone supercell continues to fire along a boundary
southeast of MEM. Scattered SHRAs and TSRAs are possible through
late morning, mainly near MEM and MKL. MVFR/IFR CIGs will
continue to affect JBR and MEM through late morning.
Most SHRA activity will be out of the region by late morning and
early afternoon. Thereafter, all sites will return to VFR.
Another round of SHRAs will arrive near the end of the period
along with MVFR CIGs.
AC3
&&
.MEG WATCHES/WARNINGS/ADVISORIES...
AR...None.
MO...None.
MS...None.
TN...None.
&&
$$
PUBLIC FORECAST...CJC
AVIATION...AC3
Office: OHX
FXUS64 KOHX 061129
AFDOHX
Area Forecast Discussion
National Weather Service Nashville TN
629 AM CDT Mon May 6 2024
...New AVIATION...
.SHORT TERM...
(Today through Tonight)
Issued at 155 AM CDT Mon May 6 2024
Our active weather pattern continues. Currently, we're in between
two rounds of storms during this overnight period. The first has
moved into KY and the second is in West TN, headed this way. While
no severe weather is expected with this second round, an isolated
wind gust or two of 40 mph isn't out of the question. The bigger
thing we're monitoring is the rainfall amounts. Over West TN, as
these storms came out of the Memphis area, 0.75 to 1.5 inches has
been noted in MRMS data. These numbers are possible in isolated
areas of western Middle TN over the next few hours, but on the
whole, everyone should get around an inch. Any training will lead to
the higher numbers. Here's the problem: the last few runs of the
HRRR have begun to hint at this round getting through the area by
about 15Z, then a third wave may develop in West TN and cross the TN
River by lunch time. If this does pan out, I'm a little worried
about at least localized flash flooding for those who get both the
second and third rounds of rains. Rainfall totals could be at 3
inches or better on top of already wet soils. We will need to
monitor this closely -- especially for areas along and north of I-40.
For the lunchtime development, forecast soundings are fairly spring-
like, but shear values are meager. Enough to support thunderstorms,
but severe chances are negligible, at best. Rain chances may linger
in the evening hours across the northern Cumberland Plateau, but
most should be dry tonight.
That's just today and tonight! I haven't even gotten to the severe
weather threats for Tuesday and Wednesday!
&&
.LONG TERM...
(Tuesday through next Monday)
Issued at 155 AM CDT Mon May 6 2024
Forecast soundings Tuesday and Wednesday continue to show some of
the more impressive environmental conditions I've seen this spring.
CAPE will build into the 1500-2000 J/Kg range on Tuesday as
temperatures climb into the low to mid-80s and dew points climb into
the upper 60s, close to 70 degrees. Shear values improve on Tuesday
and while they're not incredibly impressive, 40 kts of 0-6 km shear
and ~200 SRH is nothing to sneeze at. However, on Tuesday, I don't
see much of anything in the way of a focusing mechanism for lift --
at least in the models. Doesn't mean we can't get a outflow that
pushes into Middle TN from upstream storms, but even with the
impressive instability parameters, if we don't have some lifting
mechanism, we may be hard-pressed for get much more than isolated
storm development. For now, we'll carry a wind and hail threat for
any storms that do develop on Tuesday.
Wednesday still looks like the better day for severe weather. Heat
and moisture continue to build into the region leading to CAPE
values potentially north of 3000 J/Kg during the afternoon hours.
Without a doubt, the highest values we've seen so far this spring.
While that's all fine and dandy, we may struggle during the
afternoon to see anything that will provide lift. We'll have to
refine the Wednesday afternoon forecast over the next couple of
days, especially as we get into CAM range. However, as the
associated front moves into the region Wednesday evening, even our
global models are picking up on what looks to be a fairly intense
line of showers and thunderstorms Wednesday evening. While we'll
lose some of the heating of the day, CAPE values manage to remain in
the 1500-2000 J/Kg range and it's ahead of this line where shear
values start to increase and lapse rates get sharp (7.5+). If this
verifies, we'll be looking at all forms of severe weather being
possible. Wind, large hail, tornadoes - and with PWs being in the
90th percentile - flash flooding, as well. There's plenty to fine
tune over the next few days, so please be weather aware through the
first half of this week.
After Wednesday night, it looks like we should get a break from this
active pattern for at least a few days. Temperatures relax back into
the 70s and our next rain chances may not come until the end of next
weekend.
&&
.AVIATION...
(12Z TAFS)
Issued at 624 AM CDT Mon May 6 2024
Scattered showers and storms are moving through the terminals this
morning. There will likely be a break before more showers and
storms develop around midday and continue through the afternoon
and evening hours. The exact timing cannot be pinned down but
tempo tsra groups were added when confidence is highest. Showers
and storms should taper off no later than 00z-03z with the
remainder of the taf period being dry. Vis could be reduced to
IFR/MVFR when terminals are impacted by showers and storms. There
is a chance MVFR cigs temporarily impact CKV this morning but
confidence was not high enough to include. Winds will generally be
S/SW around 5-10 kts.
&&
.PRELIMINARY POINT TEMPS/POPS...
Nashville 82 67 85 68 / 90 30 60 60
Clarksville 80 66 84 66 / 90 40 50 50
Crossville 76 61 79 63 / 90 60 50 70
Columbia 83 66 84 66 / 70 30 50 60
Cookeville 77 63 81 65 / 100 60 60 70
Jamestown 75 61 81 63 / 90 60 60 70
Lawrenceburg 82 66 83 67 / 60 20 50 60
Murfreesboro 83 65 84 66 / 90 30 50 60
Waverly 82 66 83 66 / 90 40 50 50
&&
.OHX WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SHORT TERM...Unger
LONG TERM....Unger
AVIATION.....Reagan
Office: MRX
FXUS64 KMRX 061408
AFDMRX
Area Forecast Discussion
National Weather Service Morristown TN
1008 AM EDT Mon May 6 2024
...New UPDATE...
.UPDATE...
Issued at 1005 AM EDT Mon May 6 2024
Current radar shows a band of showers with some embedded thunder
moving northeast across the area. Will update PoPs/WX to better
show the progression of this band. Will also make some adjustments
to wind, temps and dew points, but overall the remainder of the
forecast still looks reasonable.
&&
.SHORT TERM...
(Today and tonight)
Issued at 333 AM EDT Mon May 6 2024
Key Messages:
1. Scattered showers and thunderstorms today with an upper-level
shortwave across the area.
2. Drier tonight as shortwave ridging builds in across the region
and a stronger system approaches from the west.
Discussion:
Model guidance and WV satellite imagery this morning shows
shortwave troughing across the Mid-Mississippi Valley, and this
unsettled weather will move eastward through the day. By this
afternoon, the upper-level trough is forecast to be over our
region with widespread scattered shower and thunderstorm activity.
There is a low probability of some stronger thunderstorms this
afternoon as the RAP shows MLCAPE around 2000 J/Kg; however,
limited bulk shear will limit overall storm organization and
mitigate the severe weather risk.
By tonight, shortwave ridging builds in from the west with drier
and clearing conditions. Fog will be possible if cloud cover can
significantly clear out as guidance suggests.
&&
.LONG TERM...
(Tuesday through Monday)
Issued at 333 AM EDT Mon May 6 2024
Key Messages:
1. Scattered to numerous showers and storms are likely Tuesday into
Tuesday night with a few strong to severe storms possible. Damaging
winds and hail will be the main threats.
2. More organized storms are increasingly likely Wednesday evening
into Wednesday night with all modes of severe weather possible.
Localized flooding will remain of concern to Thursday due to
repeated storms.
3. Much cooler conditions return by Friday through the weekend with
more limited rain chances.
Tuesday through Thursday
At the start of the period, an upper trough will be centered across
the Northern Plains with a downstream jet extending to the upper
Mississippi River Valley. A surface cold front will be located just
west of Missouri/Arkansas. Across the southeastern U.S. up through
the Ohio River Valley, a broad warm sector will be in place, along
with deep moisture indicated by PWAT values of near 1.4 inches, i.e.
above the 90th percentile. During the day on Tuesday, some height
falls are expected across the area as the upper-level features shift
slightly eastward. Diurnal heating and large-scale ascent will be
sufficient for scattered to numerous convection, especially in the
afternoon through the evening hours. During the day, most sources
suggest MLCAPE to peak in excess of 1,000 J/kg with deep-layer shear
reaching 30 to 35 kts. As this is the first run of the CAMs, a great
degree of uncertainty still exists with the timing and coverage of
convection. However, this overall environment is supportive of
better organization than all recent days. During the overnight
hours, low-level winds and shear will increase, but this will also
be when low-level instability decreases. A lot of the current model
sources are suggesting more development overnight. As such, the main
concerns will be damaging winds and hail, which is emphasized by mid-
level lapse rates near 6 C/km and more organized storm structures.
The abundant moisture and repeated rainfall will also keep the
localized flooding threat.
By Wednesday morning, a near 100-kt upper jet will extend into the
southern Mississippi River Valley, which will enhance upper
divergence via an indirect vertical circulation. Depending on the
evolution of convection from the previous night, activity may
continue through the morning. However, as the day goes on, dynamics
will continue increase with the aforementioned cold front
approaching from the west and 850mb flow exceeding 40 kts. Timing
differences still exist, but most sources indicate convection to be
ongoing to our west by the evening before moving in overnight. With
respect to instability, the main question will be how much activity
is ongoing through the day. With less activity, MLCAPE could be in
excess of 1,500 J/kg with deep-layer shear above 40 kts and 0-1km
shear of over 25 kts. In this scenario, all modes of severe weather
would be of concern, notably above and beyond that of Tuesday. We
are still at a temporal scale where CAMs will not reach into this
event, but concern continues to increase for a more notable severe
weather event Wednesday night into Thursday morning. This is further
emphasized by the CIPS Analogs and ensemble probabilities of over 50
percent for Supercell Composite Parameter of over 5, especially
along the Cumberland Plateau and southern Valley. By the day on
Thursday, the cold front will likely reach the area with activity
likely continuing through the day.
Friday through Sunday
By Friday, deep troughing will be over the area with much cooler
conditions following the passage of the frontal boundary ahead of
surface high pressure to the west. Still, weak ascent and remaining
moisture will be sufficient for lower but continued PoPs. Large-
scale troughing will persist into Saturday with high pressure
arriving from the west but weakening in the process. This will make
for cooler and drier conditions. Additional troughing into Sunday
will keep cooler temperatures in place with low-end PoPs based on
potential development of a weak system to our south.
&&
.AVIATION...
(12Z TAFS)
Issued at 706 AM EDT Mon May 6 2024
Showers and thunderstorms will impact terminals this morning.
Model guidance is having a difficult time resolving the current
convective activity, but timing on this complex of convection has
it impacting CHA around 12-13z and TYS around 15z. If this
activity holds together, it would impact TRI around 17z. Numerous
showers and thunderstorms will result in periods of poor flight
conditions throughout the day; exact timing is uncertain this
afternoon, but additional scattered thunderstorms are expected
later today. As this upper-level disturbance shifts eastward
tonight, probability of thunderstorms will decrease by 12z
Tuesday.
&&
.PRELIMINARY POINT TEMPS/POPS...
Chattanooga Airport, TN 83 66 86 68 / 60 30 50 60
Knoxville McGhee Tyson Airport, TN 80 63 82 66 / 80 70 60 70
Oak Ridge, TN 79 63 83 66 / 90 60 70 60
Tri Cities Airport, TN 76 60 81 63 / 80 80 60 50
&&
.MRX WATCHES/WARNINGS/ADVISORIES...
NC...NONE.
TN...NONE.
VA...NONE.
&&
$$
SHORT TERM...JB
LONG TERM....BW
AVIATION...JB
