02.20.10

First Chase Day???

Posted in Severe Weather Forecast at 12:27 pm by Rebekah

Saturday, February 27, 2010…just another cool and stable day, or the first Southern Plains supercell storm chase day of the year?  I can dream, right?  🙂

A lot can change in 180 hours, so at this point it’s all wishcasting.  Based on the GFS model, a negatively-tilted trough is forecast to dig in to the Oklahoma/Texas Panhandle region by 00Z on the 28th.  A closed, upper-level low is over eastern Colorado/western Kansas and positive vorticity advection is occurring is southwest Oklahoma and western Kansas.  There is also plenty of warm-air advection in Oklahoma and Kansas (especially in western Oklahoma).

A surface low is forecast in eastern Colorado, and it looks like a cold front may extend south of the low into the Texas Panhandle.  The model shows southeast surface winds over northern Texas, Oklahoma, and southern Kansas.  Warmest temperatures in the region may be in the mid-50s in western Oklahoma, southwest Kansas, and the eastern Texas Panhandle; temperatures in the Lawton, OK to Wichita Falls, TX area may reach the lower 60s.  Dewpoints could reach the lower 50s (highest around Wichita Falls).

CAPE values are forecast to be between 750 and 1000 J/kg in western Oklahoma (not terrific, but could be worse).  Both direction and speed wind shear look like they could be sufficient for supercells with even a marginal tornado threat, especially as a low-level jet is forecast in central Oklahoma and central Kansas.

It looks like the biggest problem with regard to severe thunderstorm formation may be the cap…forecast soundings show a high cloud layer over western Oklahoma, which may prevent the surface from receiving enough solar heating to break the cap.  IF this can occur (i.e., if the high clouds are able to clear out), and this is a huge if, I think we could be looking at the first decent storm chase opportunity west of I-35 this year, especially from Hobart to Lawton, OK to Wichita Falls, TX.

Stay tuned!

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