Severe Weather Discussion – 2008-8-6

Severe Weather Discussion for April 9 – 10, 2008.
Valid: 04/09/2008.

***Significant Severe Weather Outbreak Today and Tomorrow***
***This is a Life Threatening Situation***

Highlights:

– Widespread severe thunderstorms will occur today across Texas and
Oklahoma. During the evening into overnight hours, there will be an
enhanced severe weather threat across southern Oklahoma into north
Texas. In this area strong tornadoes, along with destructive hail and
wind are all expected. SPC has an enhanced moderate up this area.
The remainder of Oklahoma and much of Texas are in a slight risk.

– Excessive rainfall event is likely for Oklahoma tonight. Widespread
2-3 inches are likely with localized amounts to 5 inches.

– A continuation of the outbreak today is expected tomorrow across
Missouri/Arkansas/Louisiana. Destructive tornadoes, destructive hail,
and damaging winds are all likely. SPC has a moderate risk up for
this area and an upgrade to a high risk is likely tomorrow.

Discussion:

No change to prior forecast reasoning. Upper system moving east
towards the region while tropical moisture surges north across Texas.
The warm front was across central Texas early this afternoon and as
expected this boundary is having trouble moving north. Northward
movement should increase later this afternoon as the surface low and
low jet increase across the region. The warm front is expected to
move into Oklahoma during the evening hours.

For this afternoon the primary threat will be elevated severe
thunderstorms with the potential for hail to golfball size. As
evening approaches and the warm front moves into north Texas, surface
based storms are expected. These storms will have rich boundary layer
moisture and impressive speed/directional shear. As such, supercells
are likely with attendant threat of tornadoes, a few of which may be
strong. The threat will continue during the overnight hours, although
the area should shift east during the early morning hours on Thursday.

Flash flooding is a major concern and flash flood watches are posted
for much of Oklahoma. Rainfall of 2-3 inches, with localized amounts
to 5 inches appear likely overnight into Thursday. Another issue is
the rapid amount of rain in a short period of time. Given prior
excessive rainfall in eastern Oklahoma, flash flooding is likely
tonight into Thursday. Broken Bow lake is expected to exceed the
flood pool if these rains occur.

Storms may be occurring Thursday morning in the LA/AR/MO area or
redevelop during the afternoon hours. Either way, the stage is set
for a significant severe weather event to the east of this region.
SPC discussed a high risk for the Day 2, not a common discussion, and
decided to hold off. Depending on the atmospheric setup, it appears
that a high risk will be issued for parts of LA/AR/MO tomorrow.

It is emphasized that this is a dangerous situation for the affected
areas. All persons are urged to review safety rules and be prepared
for quick action should a watch or warning be issued.

Probabilities:

Risk area for any part of OK/TX (valid: 04/10 Day 1):

Slight: 100%
Moderate: 50%
High: 0%

Chase Status:

Level 1 – Normal

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About Putnam Reiter

Putnam has been storm chasing since 1990 and is a co-founder of Hook-Echo.com. For his day job, Putnam works in emergency management for information technology.
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