Severe Thunderstorm Chances Continue for Oklahoma City on Thursday

Slight chances for severe weather still exist for areas east of US-81 in Kansas, Oklahoma & Texas. This includes Wichita, Oklahoma City & Dallas. Moderate risk is now starting to show up. This area includes Tulsa, Joplin, Springfield (MO), Fayetteville, and Fort Smith. Continue to monitor the latest forecast. I have a feeling this will be changing again. Here is what the Storm Prediction Center is saying about this severe weather outbreak.

Day 2 Convective Outlook
National Weather Service/Storm Prediction Center Norman OK
1258 am CDT Wednesday Apr 13 2011

Valid 141200z – 151200z

There is a MDT risk of severe thunderstorms across parts of southeast Kansas, eastern
Oklahoma, far southwestern Missouri and far northwest Arkansas.

There is a slight risk of severe thunderstorms across parts of the Central Plains, Southern Plains, mid-Missouri Valley, the Ozarks and the Ark/LA/Tex.

Regional outbreak of severe storms and possibly tornadoes across parts of the southern and central Plains Thursday afternoon and evening.

Southern Plains/Central Plains/Ozarks/Mid-Missouri Valley: An impressive negatively-tilted upper-level trough is forecast to
close off over the Central High plains Thursday. The exit region of a 70 to 80 knots middle-level jet rounding the base of the trough will create strong deep layer shear profiles across the region creating an environment favorable for severe storm development. At the surface, a well-developed low is forecast to deepen quickly across central Kansas at midday moving northward into Nebraska. Thunderstorm initiation should first occur near and to the north of the surface low during the afternoon where strong low-level convergence and cold temperatures aloft should result in a large hail threat. The models are consistent developing strong convection during the late afternoon southeastward into central to eastern Kansas and east central Oklahoma along the western edge of an axis of moderate instability. The storms should initiate just to the east of a dryline oriented north to south along the I-35 corridor.

Forecast soundings along the instability axis at 00z Friday show MLCAPE values from 1500 j/kg in ecntrl Kansas to 2500 to 3000 j/kg in east central OK. This combined with 0-6 km shear values of 50 to 65 knots will create a thermodynamic and shear environment favorable for supercells and large hail especially across the moderate risk area in southeast Kansas, eastern Oklahoma, far northwest Arkansas and far southwest Missouri. The greatest severe threat coverage should occur on the nose of a plume of steep middle-level lapse rates which combined with the moderate instability and strong deep layer shear will be favorable for very large hail with the more dominant supercells. Tornadoes will also be possible especially as the low-level jet strengthens during the early evening. Forecast soundings in eastern OK from 00z to 03z show 0-3 km storm relatively helicities of 350 to 450 m2/s2 which will make an isolated threat for strong tornadoes possible. However, this threat should be conditional upon moisture return and storm mode. Squall-line development instead of the tendency for discrete convection would result in more of a wind damage threat.

Further south across NE Texas, forecast soundings at 21z to 00z show a stout capping inversion which is expected to hold for much of the afternoon and evening. For this reason, the severe threat should drop off quickly with southward extent in NE Texas. During the evening and overnight period, the models are consistent with developing an mesoscale convective system in the Ozarks and driving this feature eastward into the lower to middle Mississippi valley. Although severe threat coverage should decrease during the late evening and overnight period, a threat for hail and isolated wind damage may continue as far east as south central Missouri and east central Arkansas where surface dewpoints should be in the lower 60s f and 40 to 50 kts of low-level flow is forecast.


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