SPC Apr 30, 2017 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook

Day 4-8 Convective Outlook  
NWS Storm Prediction Center Norman OK
0346 AM CDT Sun Apr 30 2017

Valid 031200Z - 081200Z

...DISCUSSION...
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
Pacific Coast.

...D4/Wednesday: Portions of Central/Eastern Texas to the Lower
Mississippi Valley...
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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