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Tuesday 10/01/2019 Day 2 Marginal

Posted: Mon Sep 30, 2019 12:31 pm
by thunderchaser83
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SPC AC 300558

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1258 AM CDT Mon Sep 30 2019

Valid 011200Z - 021200Z


Isolated strong to severe storms may occur Tuesday across parts of
the Central Plains into the mid Mississippi Valley, as well as the

...Central Plains into the Mid Mississippi Valley...
A band of enhanced southwesterly mid-level winds may develop above a
surface front on Tuesday from the southern High Plains into parts of
the central Plains and mid MS Valley. These winds would be distinct
from a separate mid/upper-level jet associated with a positively
tilted shortwave trough over the western CONUS. Scattered to
numerous elevated storms will likely be ongoing Tuesday morning
along and north of the surface front owing to lift associated with a
south-southwesterly low-level jet across the southern/central
Plains. There should be some weakening of the low-level jet through
the day, but it is forecast to persist from KS to IA.

A subtle vorticity maximum, possibly associated with convection from
Day 1, may overspread the central Plains into the mid MS Valley
Tuesday afternoon/evening. A weak surface low may also develop
northeastward along the nearly stationary surface boundary.
Confidence has increased slightly in the potential for surface-based
thunderstorm development across this region along and just south of
the front, mainly Tuesday afternoon. Effective bulk shear values of
40-50+ kt will be strong enough to support supercells. Around
1000-2000 J/kg of MLCAPE should also develop with diurnal heating,
although modest mid-level lapse rates may tend to limit updraft
strength somewhat. Any storms that form in this environment could
become severe, with all hazards possible. This isolated/marginal
severe threat should wane Tuesday evening with the loss of daytime

Modest mid-level height falls should occur over the Northeast on
Tuesday as a mid-level jet overspreads this region through the
period. There is some concern that morning convection may limit the
degree of instability in the afternoon based on recent model
guidance. Even so, weak diurnal destabilization appears possible
ahead of a surface cold front across western/northern NY as
low/mid-level westerly flow gradually strengthens. Forecast moderate
to strong speed shear may support some updraft organization with any
storms that can form along/ahead of the cold front Tuesday afternoon
and subsequently spread eastward. But, poor mid-level lapse rates
will likely temper more than a marginal/isolated severe risk.
Regardless, strong to locally damaging winds may occur with this
convection through early Tuesday evening before instability lessens
with the loss of daytime heating.

Tornado: 2% - Marginal
Wind: 5% - Marginal
Hail: 5% - Marginal

..Gleason.. 09/30/2019