AWUS01 KWNH 171741
FFGMPD
ALZ000-MSZ000-172335-

Mesoscale Precipitation Discussion 0053
NWS Weather Prediction Center College Park MD
139 PM EDT Wed Mar 17 2021

Areas affected...East-Central TN into Southwest/Central AL

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

Valid 171735Z - 172335Z

SUMMARY...Severe supercell thunderstorms will be capable of
producing some flash flooding this afternoon with localized
repeating of cell activity and impacts on areas that have recently
seen heavy rainfall and have saturated soil conditions.

DISCUSSION...The latest GOES-16 satellite imagery shows convection
rapidly developing and expanding in coverage across the Deep South
with visible imagery showing a substantial amount of low-level
cloud street activity focusing across especially areas of southern
MS and southwest AL as thinning low clouds allows robust diurnal
heating to ensue and couples with a moist south-southwest
low-level jet of 40 to 45 kts for rapid boundary layer
destabilization.

The 17Z RAP mesoanalysis suggests a moderate to strongly unstable
airmass already pooled across the region with MLCAPE values as
high as 2000 to 2500 j/kg across much of central/southern MS and
west-central to southwest AL. Meanwhile, there is a significant
amount of shear in place which is being aided by the approach of a
strong upper low over the southern Plains. Already strong
kinematic profiles are favoring warm-sector effective bulk shear
values of 50 to 60 kts.

Overwhelmingly, the dominant hazard across the South this
afternoon and evening will be severe weather, as this highly
favorable thermodynamic environment couples with strong low to
mid-level shear profiles over the region for strong and locally
discrete supercell thunderstorms. Please see the latest SPC Day 1
Convective Outlook and Tornado Watch #0029 for more details.

However, there are portions of east-central MS and southwest to
central AL that will also have a somewhat elevated concern for
flash flooding if any of these supercell thunderstorms impact or
perhaps even locally repeat over the same area. Several areas in
east-central MS in between Hattiesburg and Meridian received as
much as 5 to 7 inches of rain since early yesterday morning, and
similar amounts have been noted in parts of southwest to
south-central AL from west-southwest of Montgomery to the MS/AL
border.

The latest HRRR guidance suggests some tracks of supercell
thunderstorms potentially repeating over the same area and
supporting as much as 3 to 4 inches of rain with isolate heavier
amounts going through the late-afternoon hours. This will drive
some concerns for flash flooding as a result, with a particular
emphasis on the areas that have seen heavy rainfall over the last
24 to 36 hours and thus have saturated and highly sensitive soil
conditions.

Orrison

ATTN...WFO...BMX...HUN...JAN...MOB...

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

LAT...LON 34008656 33238586 32258687 31558815 31258931
31558986 32118976 32858918 33648806
$$
--- SBBSecho 3.12-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)

AWUS01 KWNH 172053
FFGMPD
GAZ000-ALZ000-MSZ000-180250-

Mesoscale Precipitation Discussion 0054
NWS Weather Prediction Center College Park MD
452 PM EDT Wed Mar 17 2021

Areas affected...Northeast MS...Central/Northern AL

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

Valid 172050Z - 180250Z

SUMMARY...Supercell thunderstorms will continue to advance
northeast over the next few hours, with concerns for flash
flooding in addition to the all severe weather hazards.

DISCUSSION...The latest radar imagery shows numerous supercell
thunderstorms lifting northeast up through areas of east-central
to northeast MS and across central and northern AL as strong
instability, low-level moisture convergence, and enhanced shear
profiles facilitate a widespread severe weather outbreak for
portions of the Deep South and Mid-South.

There are growing concerns for additional repeating of supercell
thunderstorms going into the evening hours across areas of
especially central and northern AL which are expected to enhance
the flash flood threat on top of the severe weather hazards.

In fact, the last few runs of the HRRR guidance continue to trend
wetter and suggest some of the supercells may be capable of
producing as much as 2 to 2.5 inches of rain in one hour, with
resulting swaths of as much as 3 to 5 inches of rain going through
00Z where repeating cell activity occurs. Multiple rounds of
convection will be possible going through the late-evening time
frame as the latest guidance suggests additional convection in the
00Z to 03Z time frame from supercell thunderstorms currently
breaking out and expanding in coverage over the lower MS Valley.
Portions of this activity will arrive later in the evening and add
to the potential for excessive storm rainfall totals more broadly.

Some of these rains will overspread areas that have already seen
heavy rainfall earlier today or from yesterday, and therefore with
soil conditions locally saturated, and the short-term rainfall
rates quite high, there will be elevated concerns for flash
flooding. This will especially be an issue in and around any of
the urban corridors/cities that may also be impacted significantly
by ongoing severe weather hazards.

Orrison

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

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

LAT...LON 35008691 34968612 34858573 34498543 33928552
33408617 33038721 32928814 33108854 33378870
33768863 34368831 34658796 34848756

$$
--- SBBSecho 3.12-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)

AWUS01 KWNH 251258
FFGMPD
NCZ000-GAZ000-TNZ000-ALZ000-MSZ000-251856-

Mesoscale Precipitation Discussion 0065
NWS Weather Prediction Center College Park MD
856 AM EDT Thu Mar 25 2021

Areas affected...northern AL, southern TN, northwest GA

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

Valid 251256Z - 251856Z

Summary...A gradual increase in the flash flood risk is expected
across portions of northern AL, northwest GA and southern TN as
convection persists across the region through the morning.

Discussion...Convection is expanding in coverage/intensity this
morning across portions of northern AL into southern TN. This is
being driven by very strong low level moisture transport, with the
bulk of activity focusing on the northern instability/moisture
transport gradient. The southern extent of the moisture transport
axis over southern MS/AL will generally remained capped through
the morning hours...however continued convective development is
expected further north closer to the area of enhanced low level
convergence from northern AL into southern TN and far northwest GA.

The environment is not really conducive for true backbuilding
cells...however it is favorable for continued upstream convective development...given the persistence of moisture transport and
available instability...which will then likely track across the
same areas through the morning hours. It is this multiple rounds
of cells that will lead to some flash flood risk as the morning
progresses. Initially the flash flood risk will be isolated...but
as soils begin to saturate...and additional rounds of convection
continue...the flash flood risk is expected to increase as the
morning progresses. Recent HRRR runs seem to have a decent handle
on the current activity and expected evolution over the next
several hours. Generally looking at amounts as high as 2-3"
through 18z over the MPD area. Additional rain after 18z is
expected...with an uptick in the flash flood risk possible as
intense convection moves over saturated soils. We will continue to
monitor the area through the day.

Chenard

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

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

LAT...LON 35658564 35658432 35198397 34458483 33758670
33568748 33968801 34088808 34658823 35168814
35438709
$$
--- SBBSecho 3.12-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)

AWUS01 KWNH 272113
FFGMPD
TNZ000-ALZ000-MSZ000-280300-

Mesoscale Precipitation Discussion 0076
NWS Weather Prediction Center College Park MD
513 PM EDT Sat Mar 27 2021

Areas affected...Tennessee

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

Valid 272112Z - 280300Z

Summary...Additional flash flooding is expected to develop in
response to more thunderstorms that produce heavy rainfall through
the evening.

Discussion...After a relative lull from storms which produced
heavy rainfall this morning and early afternoon, additional
thunderstorms capable of producing downpours are expected to
develop later tonight. The greatest concern will be over areas
which received heavy rainfall earlier today, although flash
flooding is a concern where any of the cells begin to train. The
most favored axis for heavy rainfall through the evening is along
and north of a quasi-stationary front along the border of
Tennessee and Mississippi/Alabama. Southerly flow with wind
speeds of 30+ knots will continue focus the moisture flux
convergence along the front and provide a steady feed of moisture
for storms which develop along or north of the boundary.

The numerical guidance has been consistent in roughly depicting
the same corridor of favored convective training/backbuilding,
which builds confidence in the placement for potential flash
flooding and with the idea that areal coverage of rainfall will
increase this evening and persist through at least late evening.
Both the HRRR and RAP have converged on additional rainfall
amounts of widespread 1 to 3 inches with narrow embedded maximum
values of 5 or 8 inches. Flash flood guidance values were lowered
to 0.5 inches in a 3 hour period over central Tennessee after this
mornings rainfall while other areas in the outlook had flash flood
guidance closer to an inch to 1.5 inches per 3 hours extending
southwestward towards the Tennessee/Arkansas state line.

With the anticipated increase in areal coverage of heavy rainfall
and the soils already being saturated or nearly saturated,
additional flash flooding or worsening of on-going flooding is
anticipated this evening.

Bann

ATTN...WFO...HUN...MEG...MRX...OHX...

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

LAT...LON 36468812 36448607 36468454 35678457 35068508
34878822 34858966 35858942 36398943

$$
--- SBBSecho 3.12-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)

AWUS01 KWNH 032003
FFGMPD
SCZ000-GAZ000-040001-

Mesoscale Precipitation Discussion 0144
NWS Weather Prediction Center College Park MD
402 PM EDT Mon May 03 2021

Areas affected...Northern GA...Western/Central SC

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

Valid 032001Z - 040001Z

SUMMARY...Areas of repeating showers and thunderstorms will pose a
concern for flash flooding going through the late afternoon and
early evening hours.

DISCUSSION...The latest radar imagery shows several broken areas
of heavy showers and thunderstorms that are tending to locally
repeat over the same area from areas of northern GA east into
western SC. GOES-16 IR satellite imagery shows the cloud tops
continuing to locally cool in response to moderate to strong
instability that is pooled across the Southeast and along with
robust moisture transport courtesy of a southwest low-level jet of
30 to 40+ kts, and this is suggestive of additional strengthening
of the convective cores along with heavier rainfall rates. All of
this is in place as a low amplitude shortwave traverses the TN
Valley and moves into the southern Appalachians. This is favoring
a divergent flow pattern aloft more broadly across the Southeast
and thus is facilitating some deeper layer ascent.

The rainfall rates per area dual-pol radars with the ongoing
activity across northeast GA and far western SC have been as high
as 2.5 inches/hr and is reflective of the efficient moisture
transport regime and stronger instability parameters. Over the
next several hours, conditions will remain favorable for a
combination of some supercells and organized multi-cell convection.

Given the enhanced rainfall rate potential and favorable pattern
for convection to repeat over the same area, the rainfall amounts
are expected to be locally excessive. Despite high flash flood
guidance values initially, the enhanced short-term rainfall
potential will suggest at least some flash flooding potential, and
this will especially be the case for the more urbanized areas
including adjacent suburbia.

Areas of northern GA (including the Atlanta metropolitan area)
have already seen flash flooding today, and may see some renewed
runoff concerns from upstream showers and thunderstorms.
Meanwhile, downstream areas across western/central SC, and
especially the Columbia metropolitan area will need to closely
monitor this activity for enhanced runoff given the short-term
rainfall potential.

Orrison

ATTN...WFO...CAE...FFC...GSP...ILM...

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

LAT...LON 34508127 34508026 34028008 33658061 33388128
33138222 33058323 33238391 33588441 34128429
34268261
$$
--- SBBSecho 3.12-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)

AWUS01 KWNH 301719
FFGMPD
ILZ000-MOZ000-OKZ000-KSZ000-302318-

Mesoscale Precipitation Discussion 0417
NWS Weather Prediction Center College Park MD
119 PM EDT Wed Jun 30 2021

Areas affected...Eastern KS into MO

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

Valid 301718Z - 302318Z

SUMMARY...Expanding convective development over the next couple
hours is expected to lead to a scattered flash flood risk across
portions of eastern Kansas into Missouri.

DISCUSSION...We are tracking a pretty well defined mid level vort
over eastern KS...with convection expected to expand in coverage
ahead of this feature through the afternoon hours. MLCAPE is
generally 1000-2000 J/kg across the area, with PWs averaging ~2"
within the MPD area. Thus the environment is certainly sufficient
for producing heavy rainfall rates...with the flash flood risk
more coming down to longevity/duration of these higher rates.

Currently not anticipating any long duration training/backbuilding
given the setup...which will cap the upper bound of rainfall
magnitudes. However the MCV should provide enough of a trigger to
result in good convective coverage. The flow aloft remains broadly
diffluent as well, in between the upper high to the south and the
northern stream jet energy. This may help aid in maintaining
convection a bit longer than would otherwise be the case. Low
level inflow is only ~10-15 kts out of the southwest...but this
could be just enough to result in some brief southward
backbuilding with any convection that organizes enough.

From purely a rainfall magnitude perspective this setup does not
seem all that significant...with the aforementioned ingredients
resulting in hourly rainfall up to 2" and totals locally as high
as 2-4" through the afternoon. However soil conditions over most
of the MPD area (especially the northern half) are well above
normal saturation levels. Thus FFG is lower than normal over this
area. So while this event may typically only result in very
localized flash flood issues...the more susceptible conditions
suggest the likelihood of flash flood coverage more in the
scattered range...so a tick up in impacts compared to a typical
summer convective day.

Chenard

ATTN...WFO...EAX...ICT...LSX...PAH...SGF...TOP...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...NWC...

LAT...LON 39459373 39399265 39099170 38519077 38239041
37988984 37668977 37399088 37239135 36629269
36499416 36639490 37099554 37779609 37849618
38319635 38709602 39239477
$$
--- SBBSecho 3.12-Linux
* Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)