LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1250 AM CDT Sun Aug 13 2023
Valid 131200Z - 141200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF SOUTHEASTERN KANSAS...FAR NORTHEASTERN OKLAHOMA...AND INTO THE
OZARKS VICINITY...
...SUMMARY...
Severe thunderstorms are possible Sunday from portions of the
southern and central Plains into the Middle Mississippi, Lower Ohio
and Tennessee Valleys.
...Synopsis...
Ridging aloft will prevail over the western U.S. today, as well as
over the south-central and southeastern states. Meanwhile, a rather
vigorous mid-level short-wave trough will advance southeastward
across the northern and central Plains through the day, and into the
Upper Midwest overnight.
At the surface, an evolving cold front is forecast to progress
southeastward across the northern and central Plains. By sunset,
the front should extend south-southeastward from a weak low over the
eastern South Dakota vicinity to the Texas/Oklahoma Panhandles.
Meanwhile, a weak warm front should extend southeastward across
Missouri and into the Tennessee Valley area. Additionally, various
convective boundaries are forecast to reside over the
Kansas/Oklahoma/Missouri area. These surface features -- both
synoptic and convectively induced -- will contribute to the
likelihood for multiple rounds of convective activity through the
period, from the central Plains vicinity to the Mid
Mississippi/Lower Ohio/Tennessee Valley areas.
...Mid Missouri Valley to the Texas/Oklahoma Panhandles, and
eastward to the Tennessee/Kentucky vicinity...
A rather complex convective scenario is evident for today across the
primary risk area that extends from the Plains to western fringes of
the Appalachians. Convection will likely be ongoing at the start of
the period across portions of the Plains and possibly into the
Ozarks area. The storms should continue through the day, moving
eastward with time, reinforcing the various convective boundaries
across this area.
As daytime heating occurs on the periphery of these boundaries, and
along/ahead of the advancing cold front, additional storm
development is expected. Given the belt of generally 35 to 45 kt
mid-level westerlies atop the region, shear will be sufficient to
support potential for strong/locally severe storms, with hail and
locally damaging wind gusts the primary risks. Delineating any
potential area of more concentrated severe risk remains difficult at
this time, but one area where greater severe-weather coverage may
manifest is across the Ozarks vicinity. Along with a warm front
expected to lie across Missouri, a roughly west-to-east outflow
boundary may evolve -- and possibly become the effective focus for
multiple rounds of storms. With a corridor of enhanced (40 to 50
kt) west-southwesterly flow expected to lie atop this region,
episodic strong/damaging gusts are expected, which warrants
inclusion of 30% wind probability/ENH risk across this region. In
addition, with backed low-level flow expected to the cool side of
the aforementioned boundaries, corridors of enhanced low-level
veering/shear suggests potential for a few tornadoes.
Risk will likely continue through the evening and into the overnight
hours, as additional storms associated with the southeastward cold
frontal advance evolve/spread southward and eastward into early
Tuesday morning.
...New England...
Modest low-level moisture is expected to remain in place ahead of an
eastward-advancing cold front. As diurnal heating peaks through the
afternoon, mid-layer CAPE around 1500 J/kg is expected to evolve,
supporting widely scattered afternoon storm development. With
mid-level westerlies around 40 kt expected across the area, shear
sufficient for organized storms suggests marginal hail and locally
strong/damaging wind gusts will be possible with a few of the
strongest storms, before convection weakens into the early evening
hours.
..Goss.. 08/13/2023
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