SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0137 PM CST Sat Jan 30 2021

Valid 302000Z - 311200Z


Isolated severe thunderstorms remain possible through early evening
from northeast Oklahoma into southwest Missouri, as well as parts of
southeast Kansas and northwest Arkansas.

...20z Update - OK/KS/MO/AR...

The Marginal risk and 10% General Thunderstorm areas have been
trimmed on the western and southern edges. This adjustments have
been made based on the current position of the surface low and
associated cold front and warm front. Additionally, very dry
midlevel air, noted in water vapor imagery, and as sample by 12z
regional RAOBs is precluding development of deep convection
southward along the cold front/dryline. The best chance for strong
to isolated severe storms will remain near the triple point where
low level convergence is maximized. Strong ascent will also remain
focused north/northeast of the surface low, associated with the
eastward-ejecting shortwave trough. As such, a narrow corridor will
exist close to the track of the surface low the next few hours from
far northeast OK/southeast KS into far southwest MO/northwest AR.
The severe threat should quickly diminish after sunset. For more
details, reference MCD 44.

..Leitman.. 01/30/2021

.PREV DISCUSSION... /ISSUED 1022 AM CST Sat Jan 30 2021/

...OK/KS/MO/AR this afternoon...

Only minor adjustments have been made to previous forecast with main
limiting factor being expected very weak buoyancy. A well-defined
midlevel shortwave trough moving through western OK as of late this
morning will continue east-northeastward over OK/KS today and MO/AR
this evening. The associated surface cyclone will likewise develop
eastward along the KS/OK border, reaching southwest MO this evening.
Low-level moisture return within the cyclone warm sector remains
limited by ongoing air mass modification over the Gulf of Mexico in
the wake of a prior frontal intrusion. However, midlevel moistening
and lapse rates have been sufficient to support clusters of elevated
thunderstorms (rooted near 700 mb) this morning in the zone of
ascent preceding the midlevel trough.

Ongoing elevated thunderstorms will likely persist from eastern OK,
southeast KS, and western AR into early afternoon and southwest MO
through mid afternoon. In the wake of the elevated convection, a
zone of surface heating along a dryline will overlap a narrow
corridor of boundary-layer dewpoints of 50-55 F from southeast KS
across northeast OK, from midday into the afternoon. Destabilization
in this narrow corridor might become sufficient for surface-based
convection to develop near and immediately south of the surface
cyclone. Steep low-midlevel lapse rates and 500 mb temperatures of
-20 C and colder may support MLCAPE of 250-500 J/kg, with a brief
window of opportunity for low-topped supercells within the left-exit
region of the midlevel jet. Isolated damaging gusts and hail, as
well as an isolated tornado, remain possible this afternoon with
peak buoyancy, before diminishing rapidly this evening with eastward
extent and the onset of nocturnal cooling. Given lingering concerns
regarding destabilization potential, will maintain MRGL category for
this outlook and continue to monitor for a possible SLGT risk in the
upcoming 20Z update.

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