ACUS11 KWNS 140923
SPC MCD 140922
Mesoscale Discussion 1709
NWS Storm Prediction Center Norman OK
0322 AM CST Fri Dec 14 2018
Areas affected...parts of northern and central Louisiana into far
Concerning...Severe potential...Watch unlikely
Valid 140922Z - 141115Z
Probability of Watch Issuance...5 percent
SUMMARY...Isolated/marginally severe storms will remain a risk over
the next few hours.
DISCUSSION...Latest radar reveals a band of thunderstorms --
including a couple of stronger/semi-organized updrafts -- occurring
over northern Louisiana at this time. The storms are initiating
along a surface occluded front, just ahead of the main mid-level
center of circulation now centered just northwest of Houston.
Cold air aloft ahead of the upper low is contributing to steep lapse
rates aloft, and thus appreciable (around 500 j/kg) low-topped CAPE.
However, this instability remains rooted just above a slightly
stable boundary layer, with dewpoints only in the upper 50s to low
60s ahead of the occluded front.
Along with ample CAPE for continued sustenance of isolated/elevated
storms, shear through the cloud-bearing layer is quite supportive of
organized/rotating updrafts -- with veering/increasing flow with
height yielding roughly 50 kt 1km to 6km shear. Given this
environment, low-topped storms capable of marginally severe hail --
and possibly an isolated gust near severe levels -- will be
possible. A very weak/brief tornado is also not out of the
question, although the slightly stable boundary layer will remain
hostile toward appreciable tornado risk. At this time, the isolated
and marginal nature of the risk argues against any consideration for
...Please see www.spc.noaa.gov for graphic product...
LAT...LON 31139303 31599322 32049347 32659391 33139382 33309347
33309279 33169224 32509198 31699212 30999242 30819257