Forecast 8/19/09

Updated 17Z Analysis, new target area is Perry OK.

Synopsis:

An upper level trough sits just to the west and north of the forecast area with a stationary front along the same axis.

12Z 200mb Analysis:

Discussion:

A difficult forecast today with the chances for rain and severe weather through the next 24 hours but great difficulty in nailing down the scenario. The models and the Tulsa WFO blew the call on the crapvection this morning in the Tulsa area. All indicators were that it should have stayed just to the NW, however we have ongoing convection and rain through the late morning hours.

1530Z INX Radar:

The real challenge with this forecast is trying to get a handle on the severe threat later in the day. The RUC and NAM are showing CAPE values in excess of 2000Kjg this afternoon and evening with a CAP that should erode to our NW mid to late afternoon. The models are also showing decent shear to the NW and over the forecast area early evening to overnight. This combination should provide the ingredients for a severe scenario in the late afternoon and the early evening hours. The SPC has a 5% tornado risk just NW of the forecast area and based on the parameters in the latest model runs I agree with this assessment.

At this time the most likely scenario is storms will fire in south central KS in the afternoon and make a run at NE OK in this evening. The best chance for severe weather including tornadoes will be to the NW in the south central KS and north central OK region in the early evening hours. The severe threat should decrease to the south east of this area. My best guess at this time is the storms will stay discreet for a short time in the late afternoon and evening before lining out as an MCS headed for NE OK.

12Z Surface:

If I were chasing today (and the more I think about it, I just might be) I would probably pick somwhere between Wellington KS and Ponca City OK as a target around 20Z. With 0-3km helicity values up to 300, CAPE pushing 3000, LI around 10 and low LCL's, the target area should be prime. Td's in the upper 60's should provide plenty of fuel as long as we get some day time heating, but that is really in question at this point e.g. latest visable sat... http://www.rap.ucar.edu/weather/satellite/displaySat.php?region=ICT&itype=vis&size=small&endDate=20090513&endTime=-1&duration=0

All that said, due to the ongoing convection this morning and cool temperatures the models may be over doing instability and this forecast could bust in NE OK. Conditions will need to be monitored throughout the day as they evolve. Long story short, if the sun breaks through this afternoon we may be in for it tonight...

12Z 500mb:

12Z 700mb:

12Z 850mb: