Severe Weather Discussion 2008-6-2

Severe Weather Discussion for March 17, 2008.
Valid: 03/15/2008.

Highlights:

– Active severe weather day is possible on Monday for southern Oklahoma southward into south Texas.

– Isolated severe thunderstorms are possible across the Texas panhandle on Sunday, primary threat is hail to quarter size.

– Isolated severe thunderstorms are possible in Oklahoma on Monday. Excessive rainfall is also possible late Monday into Tuesday for southern Oklahoma into north Texas.

Discussion:

Models continue prior trend of developing a deep southern stream trof across the western U.S. tonight into Monday. This system will deepen significantly by Monday as it moves east. At the surface a Canadian cold front pasted through the region early on Saturday and this has pushed deep moisture into the Gulf. As the surface ridge moves east on Sunday, shallow moisture return will commence in west Texas. This moisture will move into the Texas panhandle with 50-55F dewpoints possible. 00z NAM indicates less than 50F dewpoints and this may limit the severe weather threat for this area. Directional and speed shear will be sufficient for rotating updrafts. Space and time scales of the event are very limited.

Upper system will start to split in two on Monday as the northern part ejects northeast and the southern part closes off. NAM indicates decent moisture moving north by midday Monday with near 60F expected in Oklahoma just east of a sharpening dryline. While many ingredients will be in-place for a significant severe weather event, climatology is against us. 00z NAM continues prior trend of developing early morning showers across Oklahoma and continuing this activity throughout the day on Monday. This will serve to limit daytime heating and lower severe chances. However, given the dynamics of the system, isolated severe thunderstorms cannot be ruled out in Oklahoma on Monday. The northeast moving shortwave trof will erode the cap early in the day as very impressive jet streaks move across the region. 200mb jet streak of 125kts wit ha 500mb jet streak around 90kts. All of this will combine to develop impressive lift and turn over the atmosphere.

Farther south into Texas the real concern appears to develop. This area will be capped during much of the day and not strongly influence by the northeast moving shortwave trof. Additionally, the best lift from the jet streaks should be westward removed from the warm sector. 00z NAM develops activity along the dryline by early afternoon across western North Texas with southward developing during the afternoon. This seems correct as some influence from the ejecting shortwave trof brushes the Texas warm sector. Speed and directional shear will be impressive and any organized updrafts will rotate. The main issue will be where the squall line develops and how far south discrete storms can initiate. SPC has a 10% hatched and 30% area up for much of Texas and this appears reasonable right now. NAM keeps instability low across Texas and I'm not convinced of this solution.

Probabilities:

Risk area for any part of OK/TX (valid: 03/16, Day 2):

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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