Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Jul 21 2023 20:55:36

AWUS01 KWNH 212055
FFGMPD
NCZ000-SCZ000-GAZ000-TNZ000-ALZ000-MSZ000-220230-

Mesoscale Precipitation Discussion 0782
NWS Weather Prediction Center College Park MD
454 PM EDT Fri Jul 21 2023

Areas affected...Southern TN...Northern AL...Far Northeast
MS...Northern GA...Western NC...Western Upstate SC...

Concerning...Heavy rainfall...Flash flooding likely

Valid 212055Z - 220230Z

SUMMARY...Repeat/Training ahead of MCV with spots of 2-4" over
recently wetted grounds pose possible incidents of flash flooding.

DISCUSSION...Core of strong MCS is moving through western TN.  At
the surface, the trailing end of the larger northern stream cold
front is positioned nearly splitting TN from west to east.  South
and ahead of the MCV, a narrow ribbon of enhanced unstable air
with MLCAPE of 2500-3000 J/kg, while CIRA LPW shows core of very
deep layer moisture is along the southern TN boarder totaling from
1.75 over the E to nearly 2.25" in the core of the MCS.   Moisture
convergence along the cold front with weak southerly WAA ahead of
the MCS has expanded convective coverage along and south of the
cold front in Middle TN.  Visible and RADAR loops show storms are
expanding/filling in with cold tops and strong updrafts to support
2-2.5"/hr rates.  Effective cold front of MCS is oriented
perpendicular to the MCS motion maximizing moisture convergence
along/ahead, which may even reach up to 2.75-3"/hr or at least
2"/15-30 minutes as suggested by the 18z HRRR.

Deep layer flow, like the deep moisture axis, is fairly parallel
to the frontal boundary to support at least a short period
repeat/training environment. However, propagation vectors likely
supported by any weak cold pools over the next few hours may
deflect effective storm motions just south of due east.  This
should limit most significant training, but even 1 to 1.5 hours of
training suggest spots of 3-4" are possible.  These totals in a
sub-3hr period are above the 3hr FFG (generally below 3" within
the area of concern), with a few areas of fully-saturated soils
across N AL and SE TN due to recent rains.  As such, scattered
incidents of flash flooding are considered likely over the next
few hours.

Gallina

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!9RBfgeaKsbOk5iPC5x3fgQtY-uW783LMdo_lMawBmLy9mH_h4uaxxG_lslmkpuTOdivh=
ZnS6YZCFTOFF9wTqBLFlTSg$  for graphic product...

ATTN...WFO...BMX...FFC...GSP...HUN...MEG...MRX...OHX...

ATTN...RFC...LMRFC...OHRFC...SERFC...NWC...

LAT...LON   35768653 35718336 34848256 33978315 33798408=20
            33808596 33808736 33978895 34808868 35398851=20
            35628824=20

=3D =3D =3D
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