(All days are valid from 12 UTC - 12 UTC the following day)
Note: A severe weather area depicted in the Day 4-8 period indicates 15%, 30% or higher probability for severe thunderstorms within 25 miles of any point.
PREDICTABILITY TOO LOW is used to indicate severe storms may be possible based on some model scenarios. However, the location or occurrence of severe storms are in doubt due to: 1) large differences in the deterministic model solutions, 2) large spread in the ensemble guidance, and/or 3) minimal run-to-run continuity.
POTENTIAL TOO LOW means the threat for a regional area of organized severe storms appears unlikely (i.e., less than 15%) for the forecast day.
Forecast Discussion
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 090854
SPC AC 090854
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0354 AM CDT Thu Apr 09 2020
Valid 121200Z - 171200Z
...SEVERE WEATHER OUTBREAK POSSIBLE ON D4/SUN...
...DISCUSSION...
An outbreak of severe thunderstorms appears possible on Sunday
across parts of Louisiana, Mississippi, Alabama, and possibly into
Georgia by Sunday night. Tornadoes (potentially strong/long-tracked)
and widespread damaging winds are expected to be the primary
hazards.
...D4/Sunday: TX Gulf Coast eastward through the Southeast into the
Carolinas...
Ingredients for a potential severe thunderstorm outbreak appear
likely to come together Sunday into Sunday night. An ejecting
shortwave trough is forecast to take on a neutral to somewhat
negative tilt by Sunday afternoon as it moves quickly
east-northeastward across the Southeast states. Rich low-level
moisture will be drawn inland from the Gulf of Mexico in advance of
a deepening surface low that will move from the mid-MS Valley into
the Ohio Valley by Monday morning. Moderate destabilization in
conjunction with an 80-100 kt midlevel jet and 50-60 kt low-level
jet will result in a very favorable environment for organized
convection, including the potential for long-track supercells and a
corresponding strong tornado risk. Very strong low/midlevel flow
fields will also support widespread damaging wind potential.
Some uncertainty remains regarding the northward extent of the most
significant severe potential, given the presence of widespread
convection in advance of the ejecting shortwave. Guidance also
continues to trend slightly slower, with the GFS still a notably
fast outlier. A 30% probability contour has been introduced from LA
into central/southern MS/AL and southwest GA, where confidence is
highest in the outbreak potential at this time.
An organized severe thunderstorm threat will likely continue into
Monday morning, with the potential for damaging wind and/or a few
tornadoes likely spreading into portions of the Carolinas by 12Z
Monday.
...D5/Monday: Coastal Carolinas into Southeast GA/Northern FL...
The severe threat will likely continue into at least Monday morning
from portions of the Carolinas southward into northern FL. Very
strong wind fields will support a threat of damaging winds and
perhaps a few tornadoes before convection finally moves offshore
sometime later in the day.
...D6/Tuesday - D7/Wednesday: Southeast...
Predictability decreases substantially in the wake of the powerful
system described above. The 09/00Z ECMWF depicts the development of
a frontal wave across the northeast Gulf Tuesday night, which then
moves northeastward into GA and the eastern Carolinas into
Wednesday. Such a scenario would support some severe threat along
and south of the low track, but there is little model agreement at
this time range.
..Dean/Dial.. 04/09/2020
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