AWUS01 KWNH 251746
FFGMPD
ALZ000-MSZ000-252345-

Mesoscale Precipitation Discussion 0066
NWS Weather Prediction Center College Park MD
146 PM EDT Thu Mar 25 2021

Areas affected...Eastern Mississippi and western Alabama

Concerning...Heavy rainfall...Flash flooding possible

Valid 251745Z - 252345Z

Summary...Thunderstorms over south-central Mississippi are
expected to continue to develop and track northeast this afternoon
across areas that saw heavy rain over the past day.

Discussion...Convective thunderstorms are expanding in
coverage/intensity this afternoon across south-central MS which is
in the warm sector south of the warm front. This activity is
being driven by very strong low level moisture transport through
rather unstable air. PWs are quickly rising to 1.75 inches over
southern MS (which is 2.5 standard deviations above normal) with
SBCAPE around 3000 J/Kg per recent RAP runs and the 15Z raob from
KJAN. Hourly rainfall of 1.5 inches has already been estimated
southeast of KDGX in Simpson Co, MS. These rates are agreed upon
from the 16Z HRRR.

One hour flash flood guidance is 1 to 1.5 inches near I-20 in
eastern MS as well as farther north in eastern MS along the AL
border. Given deep layer southwesterly flow, the south-central MS
activity will likely exceed FFG as it crosses these particularly
sensitive areas. Then toward 22Z to 00Z additional heavy rain is
likely with the cold frontal passage. So the flash flood
sensitivity increases through the day and we will continue to
monitor the area until the cold front passes.

Jackson

ATTN...WFO...BMX...JAN...MEG...MOB...

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

LAT...LON 34338881 34248771 33708707 33118744 32668779
31888886 31418980 31379045 32198991 32788948
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AWUS01 KWNH 251847
FFGMPD
NCZ000-SCZ000-GAZ000-TNZ000-ALZ000-260046-

Mesoscale Precipitation Discussion 0067
NWS Weather Prediction Center College Park MD
247 PM EDT Thu Mar 25 2021

Areas affected...Northern Alabama and Georgia through the
Tennessee Border into the Western Carolinas

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

Valid 251846Z - 260046Z

Summary...Scattered heavy thunderstorms across northern
Alabama/Georgia will continue to shift east along a warm front
this afternoon while activity moving into western Alabama will
lift northeast over similar areas through this evening. Flash
flooding is likely where this activity repeats over increasingly
sensitive areas, particularly in northern Alabama.

Discussion...Convective activity will continue to shift east
across northern GA to the Carolina portion of southern Appalachia.
This activity is being driven by strong low level moisture
transport over the warm front despite marginal instability (MUCAPE
generally around 500 J/Kg per recent RAP runs). Higher moisture
and instability over central/southern AL, where PWs are quickly
rising to 1.75 inches (which is 2.5 standard deviations above
normal), will continue to lift northeast on 50kt southwesterly
850mb flow, bringing a second round of heavy thunderstorms through
this evening. Hourly rainfall of 1.5 inches has already been
estimated southeast of KDGX in Simpson Co, MS. These rates are
agreed upon from the 16Z HRRR.

One hour flash flood guidance is generally 1.5 to 2 inches over AL
into northwest GA and higher farther east where it had been fairly
dry over the past week. Three hour flash flood guidance is
generally 3 to 4 inches over northeast GA and along the NC/SC
border and closer to 2.5 inches just north of there in the Blue
Ridge terrain. Given max hourly rainfall of 1.5 to 2 inches, over
already saturated areas in northern AL/northwest GA, flash
flooding is likely there and possible farther east over the
southern Appalachians. The cold front will cross this area late
this evening through the overnight, so this third round of
activity will continue to be monitored until the cold frontal
passage.

Jackson

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

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

LAT...LON 35898149 35458124 34848143 34228284 33858455
33338666 33598720 34508718 34928627 35038512
35328378 35528306

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