Severe Weather Discussion for March 12 – 18, 2012

Severe Weather Discussion for March 12 – 18, 2012.
Issued:  03/11/2012.
Highlights:
– A few thunderstorms are possible on Friday, severe chances appear low.
– Severe thunderstorms are possible Saturday and Sunday across western Oklahoma.  Confidence is low due to the D6/D7 potential but will handle with special discussions should a medium-end or greater threat develop.
–  Temperatures will be near 80F on Monday, low 80s Tuesday, near 80F Wednesday-Thursday, and upper 70s Friday-Sunday
Probabilities:
–  Severe Thunderstorms in Oklahoma:  40%
–  Storm Chase:  25%
–  Winter Precip:  < 5%
Discussion:
Southwest U.S. closed low currently ejecting northeast today and will clear the region tonight.  Upper system will weaken as it shifts northeast with little push on moisture to the south of Oklahoma.  As such, big warm-up is expected this week, lasting much of the weak.  Models do prog temperatures to cool a little as robust and deep layer moisture return commences by the weekend, with subsequent development of low clouds.
GFS and ECMWF are consistent and in decent agreement on a western U.S. longwave trof developing by Friday and shifting slowly eastward into the central U.S.  The timing is likely suspect as models tend to develop these systems a little too fast.  However, even with current timing, storm chances will increase by the weekend with Saturday and Sunday both looking favorable for thunderstorms.  Strong and veered flow aloft appears to indicate potential for organized storms and hence severe potential.  The 40% probability is for at least low-end severe chances, approaching medium-end.
GFS is preferred this week, odd to say the least but the ECMWF looks too deep.  Even if the ECMWF does verify, the overall impact on the Friday-Sunday forecast seems limited.  Currently, Friday has some potential for severe thunderstorms in northwest Oklahoma as deep moisture resides just east of a dryline in the Texas panhandle.  Mid/upper level flow looks weak but certainly enough for some shear.  Additionally, CAPE values are @1500J/Kg across parts of NW OK with the GFS showing near 2000 J/Kg.  Saturday looks to be a better setup as stronger flow aloft moves over the region and the dryline advances eastward.  Sunday has a similar setup and the flow strengthens even more.  Kansas may see the better activity as the strongest flow aloft will move over that region.  Given time of year, tough to say if the setup will truly develop into a medium-end event but the potential certainly exists.
Models lift the system northeast across the area on Tuesday which would seemingly continue severe chances into Monday and Tuesday.  These days are beyond this forecast period but at this juncture it appears storm season will kickoff on-time this year.
Didn’t get fancy with numbers, didn’t even look at MOS.  Temperatures will be very warm this week, due in-part to the impressive deep layer moisture return, which has already begun.  18z GFS shows low 50s surface dewpoints into central Canada by late week.
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