[BNAWX] Severe Storm Outlook Narrative

[EMWIN Server]

ACUS11 KWNS 181800
SWOMCD
SPC MCD 181800
TNZ000-ALZ000-MSZ000-182000-

Mesoscale Discussion 0812
NWS Storm Prediction Center Norman OK
0100 PM CDT Thu May 18 2023

Areas affected...Northeast Mississippi to northern Alabama and
southern Middle Tennessee

Concerning...Severe potential...Watch unlikely

Valid 181800Z - 182000Z

Probability of Watch Issuance...5 percent

SUMMARY...Isolated strong downburst winds and occasional severe hail
are possible this afternoon. This threat will remain too transient
and localized to warrant watch issuance.

DISCUSSION...Convective initiation is well underway across northern
MS into northern AL in the vicinity of a weak surface low and
attendant weak warm front/differential heating boundary draped to
the east. Latest GOES imagery and lightning trends indicate that
much of this convection is intensifying, likely owing to ample
diurnal warming with temperatures warm through the upper 70s into
the low 80s. Further warming, combined with cool temperatures aloft
in the vicinity of a weak upper low, will support MLCAPE values
upwards of 1500-2000 J/kg by mid-afternoon across northern AL to
southern middle TN. Although deep-layer shear is fairly modest,
favorable thermodynamics (aforementioned buoyancy combined with
PWATs above 1.5 inches and low-level lapse rates near 8 C/km) will
support the potential for damaging downburst winds as storms begin
to cluster and propagate north/northeast. Additionally, sporadic
hail approaching severe limits will be possible with the more
intense updraft pulses, though storm longevity will likely remain
too limited to support a substantial hail threat.

Further south across south-central MS, stronger mid-level flow is
likely supporting effective bulk shear values on the order of 25-30
knots within a similar thermodynamic environment. While this region
is conditionally more favorable for organized severe convection,
confidence in storm coverage remains very limited owing to very
weak/localized forcing for ascent.

..Moore/Grams.. 05/18/2023

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MRX...OHX...BMX...HUN...MEG...JAN...

LAT...LON   33708646 33798715 33848805 33628863 33428928 33258984
            33469011 34028983 34578923 35168803 35458737 35578695
            35598632 35428601 35268587 34778570 34298557 33898568
            33708601 33708646
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