Winter (Severe) Weather Discussion 2008-4-6

Winter (Severe) Weather Discussion for February 15 – 17, 2008.
Valid: 02/15/2008.

*Significant Severe Weather Episode for Central/Eastern Texas on Saturday*

Highlights:

– Active severe weather day is likely on Saturday for much of central/eastern Texas. This is a potentially dangerous situation with the possibility of strong tornadoes. Additionally, large hail and damaging winds are expected.

– Winter Storm Warning for western Oklahoma and TX/OK panhandles through Sunday morning.

– Winter Weather Advisory for central Oklahoma through northeast Oklahoma into Saturday morning.

– Flash Flood Watch for eastern Oklahoma through Sunday.

Discussion:

Very busy day weather wise and looks like we're just getting started.

For tonight, additional showers beginning to develop in northwest Texas as low level jet of 25-30kts develops. Area of mass convergence is noted in this region per the 21z RUC 850mb winds. Additionally, it is on the leading edge of 8C dewpoints. Activity should continue to increase and will result in freezing rain for areas that are below 32F. Warming should occur early Saturday morning and bring much of central and eastern Oklahoma above freezing. As such, the widespread precipitation on Saturday should be rain. There is potential that western Oklahoma will remain below freezing and the winter storm warning continue through Sunday for this concern.

Late Saturday temperatures should drop back below freezing as the surface low moves east of the region. Snow is likely in western and northern Oklahoma, with 4-6 inches accumulations. This is assuming that the 500mb low tracks across eastern Oklahoma as currently progged. In eastern Oklahoma widespread rain should occur much of the day on Saturday. Totals of 3-4 inches seem likely given impressive transport of moisture. I still expect some changes to the forecast for Oklahoma, but for now confidence has greatly improved.

Saturday is shaping up to be a very interesting day for the eastern half of Texas. Upper system will traverse eastward into western Texas during the day as the surface and 850mb lows strengthen. Very strong directional shear is likely with helicity values over 400m^2/s^2. The main component to monitor is early morning activity and resultant affects on afternoon temperatures. At this point, I think the ultimate instability values probably aren't a big deal and lead more to the development of discrete storms than anything. If temperatures can warm, then the development of discrete storms is more likely. These storms will have tornadic potential, some of which could be strong. As the upper system moves through northern Texas later Saturday a strongly forced squall line is expected. Due to continued directional and speed shear, embedded supcerlls are possible. SPC has a moderate risk area up for the southeast quarter of Texas with a 45% area. I think the continuation of a
moderate is likely, I'm not sure this will warrant a high risk unless skies are clear Saturday afternoon in the threat area.

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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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