SPC 0700Z Day 2 Outlook

Day 2 Outlook Image

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1153 PM CST Thu Nov 12 2020

Valid 141200Z - 151200Z


Isolated severe thunderstorms may occur across eastern Oklahoma and
the Ozarks/Ark-La-Tex regions late Saturday afternoon and night.

Large-scale trough amplification will occur from the
northern/central Rockies toward the Upper Midwest/upper Great Lakes
Saturday and Saturday night, with a very strong (100+ kt) polar jet
developing eastward over the middle Mississippi Valley/Ohio Valley
Saturday night. Related surface cyclogenesis is expected to occur
over the Upper Midwest Saturday night, with a surface cyclone
deepening from Iowa toward the Lake Superior/Lake Michigan vicinity
through early Sunday morning. Modest-caliber low-level moisture will
steadily advect north-northeastward in advance of an
east/southeastward-moving cold front that will reach the middle
Mississippi Valley/ArkLaTex late Saturday night.

...Eastern Oklahoma/Ozarks/ArkLaTex...
Scattered showers and thunderstorms are likely to be ongoing
Saturday morning across much of the region, with little if any
severe-weather potential expected early in the day. This
precipitation will tend to hinder the northward extent of modest
destabilization later in the day, although at least some severe risk
is expected to materialize late Saturday afternoon and evening
related to the south/southwest fringes of this early-day
precipitation/residual cloud cover.

It is probable that low/some middle 60s F surface dewpoints will
develop north/northeastward into the region by late Saturday
afternoon and Saturday night in advance of the
east/southeastward-moving cold front. In terms of guidance, 00Z
NAM/GFS runs have trended a bit stronger with surface
cyclogenesis/moisture return as similar to prior ECMWF solutions
(which have been synoptically stronger and modestly more unstable),
further lending credence to at least some late-day/evening
severe-weather risk across the region.

Even while mid-level lapse rates will not be particularly steep at
these latitudes, MLCAPE could reach around 500-750 J/kg particularly
across eastern Oklahoma/western Arkansas by early evening. Very long
hodographs (45-60 kt effective shear) would support the potential
for some fast-moving semi-discrete supercells and linear segments,
with at least some potential for damaging winds and possibly a
tornado risk. Uncertainties regarding the exact degree of late-day
destabilization preclude a categorical Slight Risk at this time.

..Guyer.. 11/13/2020

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