Severe Weather Discussion 2009-5-4

Severe Weather Discussion for April 25-26, 2009.
Valid: 04/25/2009.

Highlights:

– Active severe weather day expected across the western 1/3rd of
Oklahoma. The most significant threat area is west of a line from
Altus to Fairview. In this area strong tornadoes and destructive hail
to baseball size are possible. A lesser threat exists across the
remainder of western Oklahoma with the primary threats of destructive
hail and isolated tornadoes.

– Severe thunderstorms are likely on Sunday across much of western and
central Oklahoma. The significance of the threat remains conditional
due to expected convection tonight.

– Active severe weather pattern will continue through next week with
severe thunderstorms possible each day.

– Chase Status is increased to Level 4 – leaving at 2pm. We should be
streaming video at http://www.hook-echo.com, look for the Severe
Studios logo.

Discussion:

No change to prior forecast or reasoning. SPC has issued a moderate
risk for the western one-quarter of Oklahoma with a 15% tornado area.
Current model and observation data indicates the potential for
isolated strong tornadoes between 6:30pm – 8:30pm across a small part
of west-central and northwest Oklahoma. The area most likely to be
impacted is west of a line from Sayre to Fairview. There is seemingly
great concern for a strong tornado in this area by early evening. The
threat is conditional due to storm evolution this afternoon. If a
cluster of storms develops, which seems unlikely, then the tornado
threat would decrease. If storms remain isolated, this would increase
the tornado threat.

Storms should rapidly develop this afternoon between 4-5pm in the
eastern Texas panhandle north-northeast into northwest Oklahoma. A
dryline is expected to be in the eastern Texas panhandle with a
stalled cold front in northwest Oklahoma. Both of these boundaries
will provide favorable convergence for thunderstorm initiation later
today. Wind fields aloft will be favorable for supercells through
early evening. Low-level flow will increase and back at sunset and
this may enhance tornado potential with discrete storms. After 10pm
wind fields aloft are expected to weaken and surface instability will
also decrease. This should reduce the tornado threat, although severe
thunderstorms will continue to be possible throughout the night in
northwest Oklahoma.

Sunday's threat remains the same and will be addressed once parameters
are clearer.

Probabilities:

Risk area for any part of OK/TX (valid: 04/26, Day 1, Day 2, Day 3):

Slight: 100%, 100%, 100%
Moderate: 75%, 0%, 0%
High: 10%, 0%, N/A

Chase Status:

Level 4 – Heading to Roger Mills County around 14:00 CDT.

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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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