Subj : MESO: Mesoscale Discussion 1688
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sun Jul 23 2023 22:37:36

ACUS11 KWNS 232237
SWOMCD
SPC MCD 232236=20
NEZ000-SDZ000-240100-

Mesoscale Discussion 1688
NWS Storm Prediction Center Norman OK
0536 PM CDT Sun Jul 23 2023

Areas affected...Portions of southwestern SD into western/central NE

Concerning...Severe potential...Watch unlikely=20

Valid 232236Z - 240100Z

Probability of Watch Issuance...20 percent

SUMMARY...An isolated supercell should pose a threat for large hail
and severe wind gusts as it moves southeastward this evening. Since
the overall severe threat is expected to remain quite isolated,
watch issuance will probably not be needed this evening.

DISCUSSION...An isolated supercell has recently strengthened as it
moves slowly southeastward off the Black Hills in southwestern SD.
The immediate downstream boundary layer is very well mixed, with
recent surface observations indicating temperatures around 100 F and
dewpoints in the mid 40s. Still, greater low-level moisture is
present into western/central NE to the east of a weak surface
trough. Steep mid-level lapse rates are also present over much of
the northern/central Plains, and are aiding a plume of moderate to
strong instability to the east/southeast of the ongoing supercell.
34-45 kt of mid-level northwesterly flow is present along the
eastern half of a prominent upper ridge centered over much of the
western states. Similar values of effective bulk shear will easily
support mid-level updraft rotation with the ongoing supercell into
this evening.

Isolated large hail should remain a concern as long as this
thunderstorm remains discrete. With a southerly low-level jet
expected to only modestly strengthen tonight, and only nebulous
large-scale ascent present over the northern/central Plains, the
potential for upscale growth into a small cluster in western NE
remains highly uncertain. If a small MCS can eventually form, then a
greater threat for severe winds would exist. Regardless, the overall
severe threat will likely remain quite isolated this evening, which
suggests that a watch will probably not be needed.

...Gleason/Thompson.. 07/23/2023

....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj=
g!4VYf-eTUDYwpH6M7VxP3ozqKb2e1TGZVJ23YEB9-cOL9DtvFD2W49451dkgrPetwQaaWtppBC=
bBESRK080ZcdAGJYz0$  for graphic product...

ATTN...WFO...LBF...UNR...CYS...

LAT...LON   43500288 43560228 43240156 42460051 41640007 41050026
            40760079 41030203 41300262 42410300 43140311 43500288=20


=3D =3D =3D
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