Subj : MESO: Mesoscale Discussion 0772
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri May 12 2023 17:17:28

ACUS11 KWNS 121717
SWOMCD
SPC MCD 121717=20
MOZ000-IAZ000-NEZ000-KSZ000-SDZ000-121915-

Mesoscale Discussion 0772
NWS Storm Prediction Center Norman OK
1217 PM CDT Fri May 12 2023

Areas affected...Northeast Nebraska and adjacent areas of South
Dakota...Iowa...and Kansas

Concerning...Severe potential...Tornado Watch likely=20

Valid 121717Z - 121915Z

Probability of Watch Issuance...80 percent

SUMMARY...Surface-based thunderstorms are expected by the 19-21 UTC
period, which will increase the threat for all severe hazards. A
tornado watch will likely be needed in the next couple of hours to
address this concern.

DISCUSSION...Latest radar/IR imagery shows a plume of convection
gradually intensifying across central NE ahead of a weakening
synoptic low. Surface observations and RAP mesoanalyses suggest that
much of this convection remains elevated within a zone of isentropic
ascent ahead of the main wave. However, surface-based cumulus across
central to eastern NE has shown signs of vertical development over
the past 60 minutes as temperatures warm into the upper 70s amid
mid/upper 60s dewpoints. Filtered insolation through mid-afternoon
will maintain destabilization as lift along a surface cold
front/dryline continues. The expectation is for ongoing elevated
convection to eventually become surface based across north-central
NE while additional storms initiate along the surface boundaries
further east towards the MO River Valley this afternoon.=20

Nearly meridional flow above 1 km will allow for discrete storm
motions off the surface boundary into the warm sector. Although
mid/upper-level winds are expected to weaken through the evening,
effective bulk shear should be sufficient for organized convection.
Additionally, backed flow below 1 km will support 0-1 km SRH values
on the order of 100-150 m2/s2, adequate for a tornado threat with
the more organized storms across north/northeast NE. Across
southeast NE, the more meridional orientation of the boundary will
favor higher probabilities for initially discrete cells to
cluster/grow upscale by late afternoon/early evening, though a
severe threat will likely accompany this activity. A watch will
likely be needed within the next 1-2 hours to address this concern.

...Moore/Mosier.. 05/12/2023

....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj=
g!8i3WRjUw9gaOGMB2DPYY_8DVeMhuF2ztVXQ_s3gplOTWBx2AoB205NAC9c8MHeuGi-Vbo8cLe=
R1EzGI_qj_b_21oBvo$  for graphic product...

ATTN...WFO...EAX...FSD...OAX...TOP...ABR...GID...LBF...UNR...

LAT...LON   40969848 41309961 41720004 43070024 43779981 43989891
            43119647 42129582 41339554 40649538 40199538 39839584
            39829687 40439757 40969848=20


=3D =3D =3D
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