(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 300846
SPC AC 300846
Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0346 AM CDT Sun Apr 30 2017
Valid 031200Z - 081200Z
Most of the extended period will generally be characterized by an
amplifying trough over the central/eastern US, with an upstream
ridge building over the Rockies. By next weekend,
ensemble/deterministic guidance indicate the ridge will build
towards the central US, as another amplified trough moves ashore the
...D4/Wednesday: Portions of Central/Eastern Texas to the Lower
Convection may be ongoing across parts of the Texas Gulf Coast and
Sabine Valley Wednesday morning, in response to a weak impulse
within the sub-tropical jet, as well as several areas of enhanced
warm-air advection. Additionally, guidance is in relatively good
agreement that storms will form along a cold front pushing southeast
across Texas during the afternoon/evening. Across eastern Texas,
early-day convection may stunt considerable destabilization, keeping
the afternoon/evening severe threat somewhat disorganized. Farther
west over central/southern Texas, steep mid-level lapse rates may
offer the potential for stronger storms, but weak/modest
low/mid-level flow will likely limit updraft organization.
Considering the aforementioned uncertainties and marginal evolution
of this system, 15-percent probabilities are not introduced at this
time. However, at least a Marginal Risk will probably be introduced
for parts of the region in later outlooks.
...D5/Thursday - D6/Friday: Central Gulf Coast to the Carolinas...
As the trough continues to amplify and evolve eastward towards the
Atlantic Coast, the warm/moist sector (and any related substantial
buoyancy) will likely become increasingly displaced from the
strongest ascent and confined to coastal regions. The relatively
narrow zone of potentially favorable shear/instability overlap and
inherent uncertainty at this time range preclude the introduction of
15-percent probabilities currently.
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