Severe Weather Discussion for November 5 – 11, 2012

Severe Weather Discussion for November 5 – 11, 2012.
Issued:  11/04/2012.
Highlights:
–  A few severe thunderstorms are possible Saturday afternoon and evening.  Widespread showers and thunderstorms are possible for the southeast 2/3rds of Oklahoma late Saturday through Sunday.
–  Temperatures will be in the upper 60s Monday, low 70s Tuesday, mid 70s Wednesday, near 80 Thursday-Friday, upper 70s  Saturday, and upper 50s Sunday.
Probabilities:
–  Severe Thunderstorms in Oklahoma:  20%
Discussion:
Shortwave trof will translate southeast across the state on Monday.  Limited moisture will keep precipitation chances too low to mention.  Eastern U.S. longwave trof will then move eastward as a mid-level ridge develops across the region.  All of this is part of a pattern change, which will result in the formation of a large western U.S. longwave trof.  The likes of which we haven’t seen since May (at best).
EC and GFS are in decent agreement on this trof developing on Friday and then moving eastward into the plans.  A month ago this could have been a decent severe weather producer, but alas it isn’t October.  Either way, much needed rainfall appears likely Saturday afternoon into Sunday.  Initially, a dryline will form in western Oklahoma and shift into central sections on Saturday.  GFS has limited CAPE values, but still near 1000 J/Kg at peak heating in a narrow strip along the dryline.  Basically HWY 81 to I-35.  Wind fields aloft will be very favorable for organized thunderstorms, hinting at the potential for a few severe.  At this juncture do not see a medium-end event, as was also noted in SPC D4-8.  Indicators are that thunderstorms will develop Saturday afternoon and move eastward.  The dryline, stalled at the time, will be overtaken by the cold front as the northern stream low ejects into south-central Canada Sunday morning.  Models hint at/agree that a large part of the trof will hang back southwest and move across the region on Sunday.  Models are typically too quick with the movement, so not convinced the GFS’s QPF depiction is correct.  However, I’ve covered much of Oklahoma with POPs on Sunday, so won’t go too deep.  The cold front should stall for a period of time in southern Oklahoma as decent Gulf moisture lurks just south of it.  The resulting isentropic lift should produce widespread clouds and rainfall across parts of the state.  GFS does show some CAPE values in Texas/southeast Oklahoma, so thunder appears warranted.  Not sure on severe chances, so will leave that out for now.
Temperature wise, looks pretty straight forward and first guess was inline with going forecasts.  Did lower Sunday’s temp into the upper 50s and that maybe too high.  But, I think the upper 50s is enough to get the point across that next Sunday should be a cool, cloudy,  and rainy day across parts of the state.  Of course, knowing my luck, we’ll be in the mid 80s.
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