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Severe WX April 19-22nd, 2023

C

ColdFront

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Still a slight risk?

I don’t have any kind of expectation for this one, but per Trey’s analysis a rogue cell is always possible.

I actually think this lull may last a bit longer than we all thought.
 
TheSuckZone

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ColdFront said:
Still a slight risk?

I don’t have any kind of expectation for this one, but per Trey’s analysis a rogue cell is always possible.

I actually think this lull may last a bit longer than we all thought.
Click to expand...
Slight risk with a large hatched area was introduced D3 by Broyles on Sunday night. We'll see if he is in tonight to upgrade to Moderate
 
ashtonlemleywx

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nam_2023041818_084_30.17--90.92.png


New Orleans Midnight from the 18z NAM Saturday morning.
 
JBishopwx

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Today:
SPC.jpg
SPCTOR.jpg

.THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS WESTERN
OKLAHOMA...CENTRAL/EASTERN KANSAS...SOUTHEAST NEBRASKA...NORTHWEST
MISSOURI...AND PARTS OF IOWA...

...SUMMARY...
Severe thunderstorms with the potential for very large hail, a risk
for a few of tornadoes, and severe gusts will be possible late this
afternoon into tonight across parts of the central states.

...Central/Southern Plains to the Upper Midwest Vicinity...

A closed upper low is forecast to meander over eastern MT to
southern SK today/tonight. An upper shortwave trough attendant to
the low will pivot across the central/southern Rockies and into the
Plains during the afternoon and into the overnight period. As this
occurs, increasing southwesterly deep-layer flow will overspread the
Plains, with a 55-70 kt 500 mb jet developing over KS/NE by 00-03z.


An initial surface low is forecast near the southeast NE/northeast
KS border this morning, before occluding by midday. However, as the
mid/upper trough begins to eject over the Rockies and into the
Plains, stronger cyclogenesis will result in a deepening low over
western KS by late afternoon. This low will lift northeast during
the evening, with a sharpening dryline extending southward across
central KS into western OK/TX. Overnight, a cold front will sweep
southeast across the central/southern Plains.

A relative max in severe thunderstorm potential is expected in the
vicinity of the triple point from central KS into southeast NE where
the best combination of favorable shear, stronger forcing and
adequate boundary-layer moisture will reside. Forecast guidance
still indicates some degree of spread with regard to northward
moisture return, but dewpoints to at least the low 60s F seem likely
across central/eastern KS, northeast into the mid-MO Valley
vicinity. Very steep mid-level lapse rates atop modest
boundary-layer moisture will promote strong destabilization, and
convective initiation appears likely near the triple point from
north-central/northeast KS into southeast NE by 00z. Initial
supercells capable of very large hail are possible. A few tornadoes
also will be possible near the surface low and along the warm front
where low-level vorticity and shear will be enhanced. As a low-level
jet increases during the evening and the cold front surges
southeastward across the central Plains, some upscale development
into a line is possible with an accompanying increase in damaging
wind potential. This activity should spread northeast into
IA/southern MN and WI/northern IL overnight with a continued
wind/hail threat.

A more conditional threat is expected with southward extent along
the dryline into parts of western/central OK, and perhaps as far
south as western north TX. A sharp dryline will reside across
western OK with surface dewpoints in the mid 60s possible.
Large-scale ascent will be weaker with southward extent. However,
strong heating along the dryline and favorable low-level convergence
is likely to aid in attempts to overcome moderate capping. If
capping is overcome, isolated discrete supercells will have a narrow
window of opportunity to develop across parts of western/central OK.
While mixing/entrainment of drier air is expected (and may delay
convective initiation until near/after 00z), ECAPE still indicates
MLCAPE near/above 2500 J/kg. Furthermore, enlarged low-level
hodographs becoming elongated above 3 km are forecast. This
parameter space will be more than sufficient to support potentially
very large hail (3+ inch diameter). A tornado or two, along with
damaging gusts also will be possible with any supercell that may
develop. If cells can become established, severe potential will be
limited in time/space given expected late initiation timing and
increasing CINH with eastward extent after 00z.

...TX dryline...

Model guidance currently indicates a paucity of convective potential
along the dryline over parts of north-central TX southward to the
Edwards Plateau. A conditionally very unstable boundary layer and
deep-layer shear will support supercell potential. Any storm that
manages to develop will likely pose a large-hail threat for at least
an hour or two before this risk diminishes by mid evening.
Click to expand...
 
JBishopwx

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Tomorrow (Thursday)
SPC.jpg

000
ACUS02 KWNS 190601
SWODY2
SPC AC 190600

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Wed Apr 19 2023

Valid 201200Z - 211200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE MID MISSISSIPPI VALLEY...SOUTHERN OZARKS...ARK-LA-TEX AND
SOUTHERN PLAINS....

...SUMMARY...
Severe thunderstorms associated with wind damage and large hail will
be possible across parts of mid Mississippi Valley southwestward
into the Ark-La-Tex and southern Plains Thursday afternoon and
evening.

...Ozarks/Ark-La-Tex/Southern Plains...
Southwest mid-level flow will remain established across the Great
Plains and Mississippi Valley on Thursday, as an upper-level trough
approaches from the west. At the surface, a cold front will move
southeastward into the Ozarks and into north-central Texas. Ahead of
the front, surface dewpoints will generally be in the 60s F, which
will contribute to moderate destabilization by midday, from the
southern Ozarks southwestward. Surface heating and increasing
low-level convergence along the front will result in scattered
thunderstorm development during the early afternoon, with convective
coverage gradually expanding during the late afternoon.
Thunderstorms will be likely along the front, but also could form
southeastward across the moist sector. Several cell clusters and
line segments are expected to move east-northeastward across
southern Ozarks, Ark-La-Tex and east-central Texas during the late
afternoon and evening.

NAM forecast soundings at 00Z from southwest Arkansas southwestward
to near Dallas, have MLCAPE in the 1500 to 2500 J/kg range with
700-500 mb lapse rates near 8.0 C/km. This, combined with about 40
knots of 0-6 km shear will be favorable for severe storms. Low to
mid-level winds are forecast to be parallel to the front, suggesting
that linear mode could be favored. Multicells that can organize
could be associated with wind damage and hail.

Further southwest into east-central Texas, instability is forecast
to be even stronger, with MLCAPE peaking near 3500 J/kg. Low-level
winds are forecast to be more backed with a gradual veering profile
with height. This, along with 0-6 km shear around 40 knots could be
favorable for supercells, especially if storms remain discrete.
Hailstones of greater than 2 inches in diameter would be possible
with the more dominant supercells in areas where strong instability
develops.

...Mid to Upper Mississippi Valley...
An upper-level low will move through the northern Plains on
Thursday, as southwest flow remains strong at mid-levels across much
of the north-central United States. At the surface, a cold front
will move eastward into the mid to upper Mississippi Valley. Surface
dewpoints ahead of the front are forecast to be mostly in the lower
60s F, which will contribute to weak destabilization by early
afternoon. Large-scale ascent associated with the upper-level system
will aid thunderstorm development early in the day, with these
storms expanding in coverage and moving northeastward across the
region. In spite of the weak instability, 0-6 km shear is forecast
to be about 50 knots over much of the mid to upper Mississippi
Valley. This, along with steep mid-level lapse rates will likely
support isolated severe storms. Wind damage and hail will be
possible with the stronger multicell line segments, although the
potential for wind may be the greater of the two threats.

..Broyles.. 04/19/2023

$$
Click to expand...
 
C

ColdFront

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TornadoFan said:
Seems there's concern for a conditional strong tornado threat in Oklahoma according to the latest D1 outlook.
Click to expand...

Yeah SPC doesn’t seem that bullish on it. Seems like more of a “let’s get this possibility out there in the very slight chance it verifies”
 
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