- Täna
- Homme
- Day Three
000
acus01 kwns 231952
swody1
Storm Prediction Center ac 231950
Day 1 convective outlook
National Weather Service Storm Prediction Center Norman OK
0150 PM CST Sat Feb 23 2019
Valid 232000z - 241200z
..there is a moderate risk of severe thunderstorms from central
through northern Mississippi into southwest and south central
Tennessee and northwest Alabama...
...
Threat for a few strong tornadoes, scattered damaging winds, and
isolated large hail should persist through this evening across the
lower Mississippi Valley into the Tennessee Valley. The most likely
period for strong tornadoes is expected through 8 PM CST across
northern Mississippi, southwest and far southern middle Tennessee,
and northwest Alabama.
..lower Mississippi through Tennessee Valley region...
Primary change to previous outlook has been to trim from the west
behind broken line of storms. The warm sector continues to
destabilize from northeast la and especially central through
northern MS where pockets of diabatic warming have boosted
temperatures into the mid-upper 70s. The special 18z radiosonde observation data from
Jackson MS sampled the warm sector and indicated around 1000 j/kg
MLCAPE. Scattered pre-frontal showers and thunderstorms have been
slow to intensify due to an inversion present around 700mb. However,
as the primary zone of forcing along the warm conveyor belt shifts
eastward and interacts with the destabilizing boundary layer, some
storms should evolve into supercells given favorable wind profiles
with 60+ kt effective bulk shear and 200-400 m2/s2 0-1 km storm
relative helicity along the strengthening low-level jet.
.Dial.. 02/23/2019
Previous discussion... /issued 1018 am CST Sat Feb 23 2019/
..lower MS and Tennessee valleys...
No change made to previous outlook except behind ongoing convection
in The Ark-la-tex. Overall forecast scenario is anticipated to
unfold from midday through tonight.
A surface cyclone over far northwest OK will translate quickly
northeastward, reaching southern WI around midnight. The cyclone
will deepen rapidly in conjunction with an ejecting midlevel
shortwave trough and the left-exit region of a strengthening (100+
kt) mid-upper jet streak. The deepening cyclone will draw the moist
warm sector northward from the central Gulf Coast states into parts
of the mid-south to perhaps as far north as the lower Ohio Valley
later this afternoon/evening to the east of a cold front, as a 50-60
kt low-level jet shifts across the northern part of the warm sector.
Marginally severe hail could occur with the stronger elevated storms
across the mid MS valley, but the primary severe threat is expected
farther to the south in the warm moist sector.
Ongoing convection across the Sabine valley into southern Arkansas will
increase in coverage/intensity as large-scale ascent overspreads the
northwest portion of the rich moist sector characterized by upper
60s to lower 70s boundary-layer dew points. The most robust
insolation appears to be underway downstream of this activity across
northern la into central/northern MS where surface temperatures
should warm into the upper 70s. This will support afternoon MLCAPE
of 1000-2000 j/kg, with only weak convective inhibition.
Semi-discrete storms are expected within the lingering band of
ongoing convection, and in the open warm sector, given strong
deep-layer shear and substantial cross-boundary shear vectors. The
tornado threat will be greatest from about 20-02z across
central/northern MS into northwest Alabama and southwest Tennessee. A few strong
tornadoes appear probable given 0-1 km/effective srh of 300-500
m2/s2 and effective bulk shear near 60 kt in the rich moist
environment. Thereafter, storms should weaken by 03-06z, though
isolated tornado/damaging wind potential could persist into the
early morning across northeast Alabama/northwest Georgia where storms will
encounter a remnant wedge front.
$$
Mesoscale Discussion
000
acus11 kwns 232035
sels mesoscale discussion
Storm Prediction Center mesoscale discussion 232035
msz000-232130-
Mesoscale discussion 0127
National Weather Service Storm Prediction Center Norman OK
0235 PM CST Sat Feb 23 2019
Areas affected...central and north-central MS
Concerning...Tornado Watch 5...
Valid 232035z - 232130z
The severe weather threat for Tornado Watch 5 continues.
Summary...a relative weakness in low-level shear has limited
potential for storm-scale rotation up until now. Low-level shear
and hodograph enlargement is forecast for the remainder of the
afternoon into the early evening. A corresponding increase in
severe risk is expected.
Discussion...kdgx VAD data through the early afternoon has exhibited
relatively modest low-level shear (0-1 km srh less than 150 m2/s2).
Coupled with some weakness in the mid-level lapse rate above 500mb,
the two factors have combined to limit storm organization in the low
levels and the severe risk through 200-230 PM CST. However, a
gradual increase in 700mb flow is expected through 6 PM and
low-level storm rotation potential is expected to increase
coincident with the hodograph enlarging and not exhibiting the
degree of veer-back-veer tendency shown in earlier raobs. As such,
gradual storm intensification and increase in the severe risk with
an accompanying threat for tornadoes is expected.
.Smith.. 02/23/2019
..please see www.Spc.NOAA.Gov for graphic product...
Attention...WFO...Meg...Jan...
Latitude...Lon 32649088 33898929 33838869 33368850 32399011 32319053
32369084 32649088
