ACUS02 KWNS 140557
SPC AC 140556
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Mon Oct 14 2019
Valid 151200Z - 161200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF SOUTHEAST OK...WESTERN AR AND NORTHEAST TX...
A couple of strong to severe thunderstorms are possible Tuesday
afternoon across parts of southeast Oklahoma, western Arkansas and
...Eastern OK/TX and much of the Southern U.S....
An intensifying mid/upper low and attendant trough over the northern
Plains/Upper Midwest Tuesday morning will spread east/southeast from
the upper Great Lakes to the Gulf Coast by Wednesday morning.
Surface low pressure will deepen as the low tracks across the Great
Lakes, with a trailing cold front moving from the upper MS Valley
and central Plains during the morning, to near Lake Ontario
southwestward to MS/AL and the TX Gulf coast by Wednesday morning. A
weak lee low will drift eastward Monday night to western OK early
Tuesday. This feature is expected to then drift southeast along the
Red River to northeast TX by 00z. This will aid in a stronger surge
of deeper boundary-layer Gulf moisture northward across eastern TX
into eastern OK and the lower MS Valley ahead of the cold front.
Meanwhile, a warm front will lift northward across the Gulf Coast
states and isentropic ascent will result in periods of heavy rain
from eastern TX into the Deep South (see the WPC Excessive Rainfall
Outlook for more info on heavy rain potential).
While Gulf moisture will overspread much of the southern U.S.,
instability is expected to be weak and lapse rates poor as abundant
cloud cover limits heating. While shear otherwise would support some
severe threat, the overall thermodynamic environment coupled with
heavy rain potential should preclude severe concerns across much of
the southern U.S.
A narrow window of opportunity for strong to severe storms may
develop during the afternoon in the vicinity of the southern Plains
surface low and southward-surging cold front. This area is forecast
to be relatively free of morning convection, allowing for a pocket
of stronger heating, with high temperatures forecast to warm into
the mid 70s to low 80s. With surface dewpoints from 65-70 F, MLCAPE
values could potentially reach 1500-2000 J/kg. Modest midlevel lapse
rates from 6.5-7.0 C/km also are indicated by various guidance.
Backed southeasterly low-level flow in the vicinity of the surface
low will support 0-6km effective shear values around 35-50 kt and a
couple of supercells capable of strong gusts, marginal hail and
perhaps a tornado can not be entirely ruled out from around 20-03z.
While this scenario is uncertain and conditional, marginal
probabilities seem appropriate at this point based on NWP guidance
trends and at least a marginally supportive environment for a couple
...MAXIMUM RISK BY HAZARD...
Tornado: 2% - Marginal
Wind: 5% - Marginal
Hail: 5% - Marginal