(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.
ZCZC SPCSWOD48 ALL
ACUS48 KWNS 260836
SPC AC 260836
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0336 AM CDT Sun May 26 2019
Valid 291200Z - 031200Z
On D4/Wednesday, a mid-level disturbance will eject across the
southern Plains and eventually merge/phase with a weaker trough over
the Missouri Valley region. Meanwhile, a nearly stationary boundary
will remain oriented from southwest to northeast from west Texas to
Illinois. Ahead of this boundary, strong instability will remain in
place owing to low 70s F dewpoints and modestly steep mid-level
lapse rates. Storms should evolve into one or two expansive
clusters along the OK/TX Red River and migrate into Arkansas.
Strong deep shear will be in place, with sufficient veering with
height for organized storms and perhaps a few supercells. A risk of
all severe hazards will exist with this activity, and a 15% risk
area remain in place. Farther northeast, convective coverage is
uncertain across portions of Illinois/Indiana, although a severe
risk should develop along and ahead of a weak boundary and weak
surface low just west of the area. This region will be monitored
for a greater severe risk in later outlooks.
On D5/Thursday, differences in the large-scale pattern become large
enough to cast doubt on any potential severe weather. Some risk
will exist from portions of the Ohio Valley northeastward toward
southern New York ahead of a weak wave over the Midwest, although a
lack of a distinct synoptic-forcing mechanism (that would foster a
concentration of severe storms) precludes 15% probability
delineations at this time.
From D6/Friday onward, the pattern shifts to quasi-zonal with much
weaker flow aloft (more characteristic of summer). The risk of
severe storms should remain low enough during that period to
preclude any highlighted areas for the remainder of the forecast
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