SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0132 PM CST Thu Nov 26 2020

Valid 262000Z - 271200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON ACROSS PARTS OF THE FLORIDA PANHANDLE...SOUTHERN GEORGIA
AND SOUTH CAROLINA...AND TONIGHT ACROSS PARTS OF SOUTHEASTERN TEXAS
AND SOUTHERN LOUISIANA...

...SUMMARY...
Isolated damaging winds with thunderstorms remain possible in narrow
corridor across parts of the Florida Panhandle through southern
Georgia and far southern South Carolina this afternoon.  Isolated
large hail will be possible, mainly overnight, near the northwest
Gulf coast.

...20Z Outlook Update...
Some adjustments to the categorical and probabilistic lines have
been made, mainly to account for the ongoing progression of the
synoptic and sub-synoptic features.

As expressed in the prior discussion appended below, support for
severe storms across the Southeast remains quite marginal.  However,
5 percent severe wind probabilities have been extended along a
narrow corridor of modest prefrontal boundary-layer destabilization,
from parts of the western Florida Panhandle into far southern South
Carolina.

..Kerr.. 11/26/2020

.PREV DISCUSSION... /ISSUED 1028 AM CST Thu Nov 26 2020/

...Southeast AL/southwest GA this afternoon...
Occasional weak supercell structures will remain possible within a
band of convection drifting southeastward along a surface cold
front.  Ascent along the front will be aided by weak embedded speed
maxima aloft moving over the lower MS/TN Valley regions, in concert
with the diurnal heating cycle.  However, low-level shear will be
weak and deep-layer shear will be on the lower margins for
supercells, in an environment with MLCAPE near 1000 J/kg.  Thus, any
severe threat should be confined to isolated wind damage this
afternoon, prior to the storms weakening this evening.

...Southwest LA coast this afternoon into southeast TX overnight...
Low-level moisture is beginning to return northward toward the
northwest Gulf coast, and a few thunderstorms are ongoing across the
northwest Gulf along the warm front/buoyancy gradient.  Moisture
will spread inland this afternoon into tonight in a weak warm
advection regime, with the potential additional influence of a
subtle speed max aloft moving east-northeastward from northwest
Mexico.  A few thunderstorms will develop inland over southwest LA
this afternoon, with more substantial storm development expected
farther west and north in southeast TX after 06z tonight.  Low-level
shear will not be particularly strong, but effective bulk shear of
40-50 kt, midlevel lapse rates of 7-8 C/km, and MUCAPE near 1500
J/kg could support isolated hail near 1" with slightly elevated
convection.

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