SPC AC 060600
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
0100 AM CDT Tue Jun 06 2023
Valid 071200Z - 081200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE SOUTHERN HIGH PLAINS...NORTHWEST...NORTHERN PLAINS/UPPER
MIDWEST...CAROLINAS VICINITY...AND FLORIDA...
Isolated strong to severe thunderstorms appear possible Wednesday
across parts of the southern High Plains, Northwest, northern
Plains/Upper Midwest, Carolinas vicinity, and Florida.
Upper ridging will remain centered over the northern/central Plains
on Wednesday. An upper low is forecast to persist over the Northeast
and Canadian Maritime provinces, with a mid-level shortwave trough
expected to move generally southward across the Great Lakes, OH
Valley, and Mid-Atlantic through the period. This should encourage
mid/upper-level troughing over much of the eastern CONUS. Across the
western states, a mid/upper-level low initially over CA should
develop very slowly eastward across the Sierras and western Great
Basin. A modestly enhanced upper-level sub-tropical jet should
extend across northern Mexico into the southern Plains, Gulf of
Mexico, and parts of FL.
...Southern High Plains...
Scattered thunderstorms are forecast to form over the higher terrain
of central/eastern NM and west TX Wednesday afternoon. Although weak
upper ridging will persist across this region, modestly enhanced
mid/upper-level westerly winds should be present with southward
extent across the southern High Plains in association with a
sub-tropical jet. Deep-layer shear should generally range around
20-35 kt, perhaps slightly weaker towards CO/KS. Loosely organized
thunderstorm clusters spreading eastward Wednesday afternoon/evening
may be capable of producing isolated severe gusts as low-level lapse
rates steepen through the day. Occasional large hail also appears
possible, especially across parts of west TX where marginal
supercells may occur with slightly stronger effective bulk shear.
...Northern California into Oregon/Idaho and Western Montana...
Similar to Day 1/Tuesday, thunderstorms should initially develop
over the higher terrain of northern CA due to orographic influences
and weak ascent on the northern periphery of an upper low. With
seasonably cool temperatures aloft and modest deep-layer shear
forecast, some of these thunderstorms could produce marginally
severe hail. Additional convective development should occur farther
east into OR/ID and parts of western MT. While low-level moisture is
forecast to remain rather limited, sufficient instability to support
high-based thunderstorms is still forecast. 20-30 kt of effective
bulk shear should also provide modest updraft organization. Isolated
severe wind gusts should be the main threat with convective clusters
as they spread generally west-northwestward with time. Some hail
could also occur with initial development.
...Carolinas and Vicinity...
Weak to moderate instability should develop Wednesday afternoon
along and south of a weak surface trough/front from central GA
across coastal SC/NC. Low-level convergence is forecast to remain
weak, as low/mid-level flow should be mostly westerly and parallel
to the boundary. Still, strengthening winds with height, especially
at mid/upper levels in association with an amplifying upper trough,
should support around 25-35 kt of deep-layer shear. Any
thunderstorms that can form along the boundary and spread eastward
towards the Atlantic Coast could produce isolated damaging winds,
and perhaps marginally severe hail, before moving offshore. Overall
convective coverage should remain fairly isolated.
A weak, low-amplitude shortwave trough embedded within an
upper-level sub-tropical jet may advance eastward across the Gulf of
Mexico and FL Peninsula on Wednesday. A seasonably moist low-level
airmass should be present across this area, and daytime heating
should encourage at least moderate instability along the Atlantic
Coast by early afternoon. Thunderstorms should preferentially form
along the Atlantic Coast sea breeze and perhaps the Everglades,
where low-level convergence should be slightly greater. Low-level
winds are expected to remain weak, but west-southwesterly flow
should strengthen with height at mid/upper levels. Around 25-35 kt
of deep-layer shear should promote some updraft organization.
Occasional damaging winds and severe hail may occur with the more
robust cores before they move offshore. But, poor mid-level lapse
rates should tend to limit updraft intensity to some extent, and
keep the overall severe threat fairly isolated/marginal.
...Northern Plains/Upper Midwest...
On the eastern side of upper ridging, isolated to scattered
thunderstorms will probably develop Wednesday afternoon along a
nearly stationary surface front. This convection should then spread
southward across eastern Dakotas/NE and western MN/IA through early
evening. Although flow through mid-levels should remain fairly weak,
deep-layer shear peaking around 20-25 kt should aid modest updraft
intensity and organization. Loosely organized multicell clusters may
produce isolated strong to severe wind gusts, with some potential
for a remnant MCV to provide a focus for renewed convective
development Wednesday afternoon. Occasional marginally severe hail
may occur as well.
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