- Day Three
acus03 kwns 210831
Storm Prediction Center ac 210830
Day 3 convective outlook
National Weather Service Storm Prediction Center Norman OK
0230 am CST sun Dec 21 2014
Valid 231200z - 241200z
..there is a slight risk of severe thunderstorms from the lower MS valley into
the Gulf coastal region...
..there is a marginal risk of severe thunderstorms over the lower MS valley into a
portion of the southeastern states and northern Florida...
Potential will exist for a few strong to severe thunderstorms from
southern portions of the lower Mississippi Valley through the Gulf
coastal region Tuesday into Tuesday night. The primary threats will
be isolated damaging wind gusts and a couple of tornadoes. Some hail
will also be possible...mainly over the lower Mississippi Valley
High-amplitude upper trough will advance slowly through the plains
with an embedded southern stream shortwave trough reaching the lower MS
valley region Tuesday night. Primary surface cyclone attendant to the
northern-stream shortwave trough will weaken as it moves toward the western
Great Lakes. The trailing cold front will continue through the MS
valley and likely extend from the Great Lakes southward into Alabama by the end
of this period. Weak cyclogenesis will also be possible in
association with the southern-stream impulse...and this feature should
lift northeastward along the front through MS into the Tennessee Valley overnight. A
warm front should stall over the Gulf Coast region.
..lower MS valley through the Gulf coastal region and northern Florida...
Primary complicating factor this forecast is potential for numerous
showers and thunderstorms to develop early in period over a portion
of the southeastern states within zone of isentropic ascent along and north
of coastal front. This should limit boundary-layer destabilization
potential with northward extent away from the Gulf Coast. Greatest cape
early Tuesday is likely over la and southern MS where remnant eml will
have advected above western fringe of the moist axis. MUCAPE in this
region may approach 1500 j/kg. Storms will likely increase during
the day along and north of the warm front from the Gulf Coast area
northward into the southeastern states promoted by a broad southerly low level jet. Given
effective shear from 40-50 knots...potential will exist for a few
supercells...and storms may become rooted near the surface over southern
portions of the lower MS valley and Gulf Coast region. Other storms
may develop as southeastward advancing front intercepts the moist axis.
Activity will develop eastward during the day and overnight through the
southeastern states and Gulf of Mexico and eventually into northern Florida. Will
maintain a lower-end slight risk this update given the conditional
nature of the threat.