Severe Weather Discussion for October 17, 2007.
*Active Severe Weather Day Expected Tomorrow*
– Severe thunderstorms are expected Wednesday afternoon and evening for central/eastern Oklahoma northward into Kanssas. Primary threats are tornadoes, destructive hail, and damaging winds.
– Showers and isolated thunderstorms are possible tonight into Wednesday morning.
– Thunderstorms are possible on Sunday.
Little has changed in the evolution of this event today. There are some major questions, which will not be answered until tomorrow morning.
Models continue to advertise a negative tilt trof moving into the region Wednesday afternoon and evening. Very impressive speed and directional shear will overspread the region during the day. This combined with unseasonable moisture provides potential for a significant severe weather event. Two issues for this event involve 1) overnight/morning convection and 2) dryline location.
12z NAM-WRF is quite aggressive with overnight convection and activity during the day. It develops a narrow area of QFP across central Oklahoma, generally around I-44 throughout much of the day. By late afternoon the upper system swings through the state and associated convection lifts northeast. The 06z NAM was a little less aggressive and even developed more CAPE in the area. The 12z GFS is a little less on the QPF but still keeps clouds around during the day. While the HRW is even less on QPF, having very little overall. The GFS is probably good middle ground as enough lift should move into the region to develop activity overnight. Until tomorrow morning, it is tough call on how much or the resulting affects on the atmosphere. If showers do occur and they move out by noon, then there should be sufficient time for heating to occur. While I do agree with Day 2 that sun angle is an issue, the sun doesn't have to heat the ground much either.
The other issue is dryline location and I think the dryline will be near Weatherford tomorrow afternoon. It should push into central Oklahoma by evening and maybe somewhat into eastern sections. The cold front will rapidly catch it, so the location after convective initiation is irrelevant. Either way, I do not think it will be knocking at I-35 at 3pm, more like 7-8pm. By then, the show should be in eastern Oklahoma.
SPC made no changes to the Day 2 and for now this looks good. No reason to change the forecast as we really won't have a good clue until late morning.
Thunderstorms are possible again on Sunday as moisture returns ahead of the next system. I'm not going into any details but SPC has the state highlighted in the Day 6 product.
Risk area for any part of OK/TX (valid: 10/17 Day 1):
Level 2 – monitoring
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