Severe Weather Discussion May 28 – June 1, 2013.

Severe Weather Discussion May 28 – June 1, 2013.
Issued:  05/28/2013.
Highlights:
–  Severe thunderstorms are likely on Wednesday.  Primary threats are tornado, destructive hail, and damaging winds.
–  Severe thunderstorms are possible Thursday-Saturday across parts of Oklahoma.
Discussion:
Severe thunderstorm watch is posted for far northwest Oklahoma and the panhandle until 10pm.  Currently an area of severe thunderstorms is located near Amarillo, north-northeast into Beaver County.  This area should progress eastward during the early evening hours and eventually dissipate.
Additional severe thunderstorms are likely across western Oklahoma on Wednesday.   The dryline will mix eastward to the eastern Texas pahandle as an upper system translates into the region.  Wind fields will increase across the entire state with CAPE values @2500 J/Kg.  Models have consistently low-balled CAPE values on Wednesday and this may be due to widespread cirrus.  A narrow ribbon of decent CAPE is expected in the eastern Texas panhandle and far western Oklahoma at the very least.  Models agree that storms will initiate during the mid-afternoon hours.  Models show a strong veer-back-veer profile for Wednesday and this may limit tornado potential.  SPC has a moderate risk up and that may be more for destructive hail; which appears likely in the threat area.
Thursday looks to be much more robust than Wednesday as the dryline mixes eastward into Oklahoma and strong veering profile develops with height.  NAM is a little interesting and somewhat distressing given the dryline about 60 miles west of OKC.  Storms will likely develop by mid-afternoon as has been the case the past few weeks.  As is common, convection the day before will play a major role in what happens on Thursday.  However, this day has the potential to be a medium-end event and I do expect SPC to issue a moderate on the 17:30z 05/29 update.
The threat for Friday isn’t any easier to determine and will be strongly governed by activity on Thursday.  18z NAM shows not as much turning on Friday in the low levels but CAPE values look to be extreme.  Either way, a dryline should be in the area with robust moisture and decent winds.  Anything can happen.
12z EC/GFS, 18z NAM, and a variety of convection allowing models all were used for this forecast.  Models are in decent agreement, although there are a few important surface feature placement details to be sorted out.  I did defer to the NAM given good performance recently.
On a personal note, I’ll try to get these out as I can but I’m working 12 hr shifts/7 days a week.
Probabilities:
Risk area for any part of Oklahoma (valid:  05/29 Day 1, Day 2, Day 3):
Slight:  100%, 100%, 100%
Moderate:  100%, 100%, 0%
High:  0%, 0%, N/A
Chase Status:
Level 4 – Normal – not that  we aren’t interested, just can’t get away.
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