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4/7-4/10 possible severe WX

Dec 12, 2018
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Spartanburg, SC
A closed upper low and associated surface low will reach the
Central Plains by Wednesday, and become a partially cutoff upper
low and occluded surface low somewhere over the Mid-Mississippi
Valley by Thursday morning. A couple showers/storms may develop
with daytime heating Wednesday afternoon, but the main focus for
deeper convection will remain well to the northwest near a pre-
frontal trough along the Mississippi River. After midnight
Wednesday night, a vort max rotating around the base of the cutoff
low and associated height falls will move into Central Alabama
along with a LLJ and moisture axis. Kinematics during this time
may be supportive of a marginal threat of severe storms, but
confidence in sufficient moisture return/instability for organized
severe storms is too low to mention in the HWO at this time for
late Wednesday night. The moisture axis and vort max depart the
area Thursday morning. The forecast for Thursday
afternoon/Thursday evening will be dependent on the position of
the cutoff low and a possible secondary vort max that may rotate
around it, as well as air mass recovery in the wake of any morning
showers/storms. Latest model runs are hinting at increased
coverage of showers and storms back along a pre-frontal trough
over Mississippi and northwest Alabama. If this occurs, CAPE
values around 2000 J/kg, fairly steep mid-level lapse rates and
0-6km bulk shear values around 50 kts would be supportive of a
couple severe storms with large hail and damaging winds. Low-level
shear/helicity and associated tornado potential look marginal at
this time unless a secondary surface low and LLJ forms. Given
uncertainty regarding morning convection and inherent uncertainty
with cutoff lows this far out, confidence is too low to mention
severe storms in the HWO at this time for Thursday. Models may be
trending drier for Friday, but that will depend on the evolution
of the cutoff low.


Staff member
Jan 4, 2017
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Chalybeate Springs, NC
Hah with blocked up flow to
Last April = big AK ridge/block And Big vortex in Canada with S/Ws rounding the base giving severe wx outbreaks
This April : -NAO block slowing flow and giving us severe?
I'm not sold we get enough low level moisture recovery with that vortex off the EC but we will see.