Subj : MESO: Mesoscale Discussion 1621
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Tue Jul 18 2023 22:43:00

ACUS11 KWNS 182242
SWOMCD
SPC MCD 182242=20
NDZ000-SDZ000-190045-

Mesoscale Discussion 1621
NWS Storm Prediction Center Norman OK
0542 PM CDT Tue Jul 18 2023

Areas affected...portions of central/eastern ND/SD

Concerning...Severe potential...Watch possible=20

Valid 182242Z - 190045Z

Probability of Watch Issuance...60 percent

SUMMARY...Isolated to widely scattered strong to severe
thunderstorms are expected by 00z. Large hail will be the main
hazard with this activity. A watch may be needed in the next couple
of hours.

DISCUSSION...Southerly low-level flow ahead of a sharpening and
southeastward-advancing cold front has allowed for a corridor of
mid/upper 60s F dewpoints to overspread much of central ND/SD.
Dewpoints decrease to the upper 50s/low 60s over the eastern
Dakotas. Pockets of strong heating and steep midlevel lapse rates
have allowed for moderate to strong destabilization. Warm advection
is resulting in some cloudiness on the eastern periphery of stronger
instability, and some elevated weak convection is currently ongoing.
However, further west closer to the cold front and zone of stronger
low-level convergence, deepening cumulus has been noted in visible
satellite. As stronger ascent spreads eastward this evening,
isolated to widely scattered thunderstorm development is expected.

Low-level flow will remain rather weak, but effective shear
magnitudes greater than 40 kt will support organized cells.
Elongated hodographs, in conjunction with steep midlevel lapse rates
and 30-40 kt westerly flow between 3-6 km suggest large (and
possibly isolated very large/2+ inch diameter) hail will be possible
with this activity. Timing of convective development is a little
uncertain, but the severe risk is expected to increase by 00z, and a
severe thunderstorm watch may be needed in the next couple of hours.

...Leitman/Edwards.. 07/18/2023

....Please see https://urldefense.com/v3/__http://www.spc.noaa.gov__;!!DZ3fj=
g!_5hg6BJf6I0_2ZeKOJ-QO9UdfSvIxkD1B-C05-TukQaZItEEIXvrj6Y4qyIN8G9AGAqzi6YYg=
kXJDaQNPGRMqrC1v_I$  for graphic product...

ATTN...WFO...FGF...FSD...ABR...BIS...UNR...

LAT...LON   44580116 46370112 47460101 48070080 48419999 48509910
            48329851 47979790 47379761 46629753 45769754 44259824
            43859897 43819958 43810013 43960067 44580116=20


=3D =3D =3D
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