Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
430 PM EDT Thu Jun 18 2026
Day 1
Valid 16Z Thu Jun 18 2026 - 12Z Fri Jun 19 2026
...THERE IS A HIGH RISK OF EXCESSIVE RAINFALL FOR THE CENTRAL GULF
COAST...
...WIDESPREAD AND LIFE THREATENING FLASH FLOODING LIKELY TODAY FOR
THE CENTRAL GULF COAST...
...1600 UTC Update...
A widespread and life-threatening flash flood event is underway
across the central Gulf Coast and will continue to expand
northeastward deeper into the Southeast throughout the day. Flash
flood emergencies have already been issued both in southeastern and
central LA as well as southern Mississippi where bands of
backbuilding, training thunderstorms have already lead to MRMS
estimated rainfall totals of 9-11" (see WPC MPD #450 for more
details). Torrential rainfall is expected to continue throughout
the day with these ongoing storms as well as additional bands of
thunderstorms supported by a surface low associated with the
remnants of Tropical Storm Arthur, an impressive ~40-50 kt low
level jet off the Gulf, and daily-record level PWATS over 2". Some
modest adjustments were made to the inherited outlook based on
ongoing thunderstorms and the latest 12Z hi-res guidance including
a westward expansion of the High Risk to central Louisiana where
ongoing life-threatening flash flooding is occurring. A slight
northeastward expansion was also included across southern
Mississippi and Alabama given moderate to high probabilities from
the HREF of 5-8"+ of rainfall. Guidance in general has suggested a
northeastward expansion of the flash flood risk bringing heightened
concern to southwestern to central Georgia as well as further
north into the southern Appalachians.
Elsewhere, the Slight Risk over portions of the southern
Plains/Texas was also expanded based on the latest 12Z hi-res
guidance. Thunderstorms are expected to develop later this evening
and into the overnight hours in vicinity of a wave of low pressure
along an approaching cold front and southward along the dryline.
Sporadic/slow storm motions and clustering of storms will support
locally heavy rainfall, especially if the collective
clustering/merging of cold pools can result in more organized
complexes as suggested by some of the hi-res guidance. This
includes both along the Red River Valley, where a Slight Risk is
already in place, as well as further south along the dryline into
the Texas Hill Country where the Slight Risk has been expanded.
Some of the latest hi-res guidance (including the RRFS) is more
bullish on the potential for heavier rainfall spreading southward
given expected storm motions and potential for a more organized
complex to develop.
Another round of thunderstorms is expected today over portions of
Arizona and New Mexico where some locally heavy rainfall/isolated
flash flooding will be possible given heightened moisture in place.
Most storms will likely be diurnally driven along the more complex
terrain. Increased moist southerly flow off the Atlantic into
interior New England/Upstate New York ahead of an approaching low
pressure system will also bring the threat for some locally heavy
rainfall (1-3" totals) and isolated flash flooding.
Putnam
...Previous Discussion...
...Southeast...
The remnants of Post Tropical Cyclone Arthur are moving into the
Central Gulf Coast this morning. While the cyclone center may have
dissipated, the moisture plume and associated rainfall shield most
certainly have not. Rainfall moving into southeastern Louisiana
right now are producing rates to 3 inches per hour. These kinds of
rainfall rates are expected to continue with the strongest cells
for much of the day today across the central Gulf Coast. An
impressive 50 kt low level jet at 850 is advecting very deep
tropical moisture into the coast. This is pushing PWATs to over 2.6
inches. Meanwhile instability over the Gulf is up to 4,000 J/kg.
This is supporting very efficient cells capable of multiple inch
per hour rates to the east of the remnant circulation center.
Multiple waves of storms will track south to north across eastern
Louisiana into southern Mississippi this morning. The area has been
hard hit with heavy rain in recent days, so larger rivers are
already flooding, and soils are nearly saturated, so nearly all of
the heavy rainfall is expected to convert to runoff, resulting in
more significant river, stream, and creek rises though the morning.
The eastern side of the plume of moisture will spawn additional
numerous thunderstorms into southern Alabama and the Florida
Panhandle through midday. The storm organization is expected to
change a bit into the afternoon with peak heating. To the west
across Mississippi and Louisiana, backbuilding and training
convection is expected to form into 1 or 2 nearly stationary lines,
as the individual cells embedded within train towards the east
along the line. Meanwhile, over Alabama, multiple lines of eastward
moving lines of storms will get the flooding and heavy rainfall
started as early as mid-morning. The western end of the line in
LA/MS will become the trailing storms on the southwest end of the
MCS associated with post tropical cyclone Arthur. This line will
very slowly drift southeastward towards the Gulf Coast, likely
impacting Mobile and eventually the Pensacola area, as well as
points north. This will result in multiple hours from mid-afternoon
into the evening where training storms track over the same areas.
The eastward moving convection is expected to move faster towards
the east than the storms can backbuild, so the trailing line
responsible for the worst flooding should gradually shift east as
well. The storms could persist as long as until midnight in the
Florida Panhandle, but most guidance has it moving on and
dissipating earlier in the evening. Regardless, with potential for
multiple inch per hour rainfall rates with numerous storms through
the day tracking over the same areas, the storm total rainfall in
these areas is likely to pile up very quickly. Guidance suggests
rainfall totals in many areas of the High Risk could exceed 12
inches, though local amounts could approach 20 inches.
Widespread and potentially life threatening flash flooding is
likely as a result of these double-digit rainfall numbers. Urban
areas that could be impacted from New Orleans (in a higher-end
Moderate Risk), Mobile, and Pensacola could see life-threatening
flash flooding occur as a result. Everyone should heed the advice
of local authorities as warnings are issued.
Across central Alabama into northern Georgia, storm coverage and
intensity of the strongest cells are expected to be a bit lower,
but antecedent soil conditions remain nearly saturated. Multiple
hours of moderate to at times heavy rain are expected up as far
north as Birmingham and northeast as Atlanta. The Moderate Risk for
these areas remains in place with few changes. An eastward
expansion of the Moderate Risk in west-central Georgia was also
made.
...Ohio/Tennessee Valleys...
A cold front pushing south across the Ohio Valley today will run
into the northern extent of the deep plume of tropical moisture
associated with the remnants of Arthur. With daytime heating, the
clashing of air masses along the front will result in numerous
showers and thunderstorms developing along the front, which will
likely be along the KY/TN border, extending ENE into eastern
Kentucky and southern West Virginia. The storms will be in a
favorable environment for training as the plume of moisture tracks
parallel to the front as well. A shortwave trough will help the
front advance south and east across the area more quickly this
evening through tonight, which should end any backbuilding and
training from the afternoon and allow everything to progress
eastward, ending the flooding threat.
...Southwestern Oklahoma into North Texas...
Overnight tonight, an MCS is expected to develop across
southwestern Oklahoma and north Texas in response to both proximity
to the dry line, deep tropical moisture with PWATs approaching 2
inches, and a developing low over West Texas, encouraging the
formation of a low level jet into the storms. Given this is a
smaller feature than the remnants of Arthur to the east, the CAMs
are struggling much more with where and how long the storms in the
area will form, and where they will track. Most likely the storms
will remain along the Red River/OK-TX border. The inherited Slight
covering most of the rest of Oklahoma into Arkansas was dropped to
a Marginal as this MCS should remain well separated from the rains
with Arthur to the east, with little rain in between.
Wegman
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
328 AM EDT Fri Jun 19 2026
Day 1
Valid 12Z Fri Jun 19 2026 - 12Z Sat Jun 20 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL IN EFFECT FOR
PARTS OF THE CENTRAL GULF COAST REGION...
...Central Gulf Coast States...
Lingering flood impacts following the deluge over the last 24
hours will be exacerbated by additional rounds of slow-moving
convection today from central MS and eastern LA to the FL Panhandle
and far southwest GA. Low-to-mid level convergence will extend in
a west-east orientation just to the north of the Gulf Coast and
remain a focus for broken areas of showers and thunderstorms
throughout the day. These storms will tap into PWs above 2" and
remain relatively slow-moving with westerly convergent 850mb flow
less than 15 kts, leading to hourly rates of 2-3"/hr. Activity will
likely be ongoing across the region at 12z and pulse throughout
the day and into the overnight period. 00z HREF probabilities for
at least 3" per 6-hrs start the day 1 period as high as 60% across
southern AL and the FL Panhandle before becoming more scattered in
nature and lowering to around 30% for the overnight period. The
primary factor for maintaining the MDT risk is the fact that these
storms are likely to overlap with an area that recently received
widespread 4-8" rainfall totals (locally over 12") and soils are
easily overcome when rainfall rates exceed 2"/hr. This will lead to
additional scattered flash flood concerns on top of ongoing flood
impacts and recovery efforts.
...Southern Plains to the Upper Texas Coast...
Scattered flash flooding is also a concern from southern OK into
much of central and eastern TX today as thunderstorm activity
begins early this morning and gradually meanders east with time
through tonight. Vast amounts of uncertainty exist with the
mesoscale details surrounding the excessive rainfall forecast in
this area, particularly for being a day 1 forecast, but PWs
near/slightly above 2" and widespread dew points into the upper 70s
and low 80s point to an environment ripe for intense rainfall
rates. As convection develops early this morning the expectation is
for an MCV or multiple MCVs to spawn ahead of an approaching weak
shortwave and within a building ridge over the south-central U.S..
This weak steering pattern will lead to conditions where MCV
location and outflow boundaries could drive the convective mode.
Even if thunderstorms remain mostly progressive after cold pools
develop, intense rainfall rates of 2-3" are possible throughout the
Southern Plains into eastern TX and the ArkLaTex. One area of
focus to monitor into the overnight period into Saturday morning
will be across eastern TX into central LA where a frontal boundary
is forecast to drape and potential interact with a weak surface
low or remnant MCV. Several CAMs indicate more widespread
thunderstorm activity around 12z Sat. here or just to the south
across southeast TX as the nocturnal low-level flow increases
towards the frontal boundary. 00z HREF neighborhood probs for at
least 3" per 6-hrs are generally around 30% here, but REFS probs
are much higher (60%) and farther south along the upper TX
coastline. Thus, a large SLGT risk is in effect for this region to
highlight the widely scattered/uncertain nature of thunderstorms,
but while also likely containing intense rainfall rates capable of
flash flood impacts.
Snell
Day 1 threat area:
www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
328 AM EDT Fri Jun 19 2026
Day 2
Valid 12Z Sat Jun 20 2026 - 12Z Sun Jun 21 2026
...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF
THE CENTRAL PLAINS AND MISSOURI VALLEY...
...Central Plains and Missouri Valley...
A large area of heavy rain associated with a developing MCS
starting Saturday afternoon and continuing into Saturday night is
expected to bring widespread heavy rainfall across portions of the
central Plains into the Missouri Valley with the greatest threat
currently expected across southeastern Nebraska, northeastern
Kansas, and far northwestern Missouri/southwestern Iowa. Storms
are expected to initiate Saturday afternoon with peak heating over
the central High Plains and ahead of a racing shortwave crossing
the Rockies. Meanwhile, a LLJ of southeasterly flow will pump deep
Gulf moisture up the Plains through the day. This will force the
dryline to race eastward in response. The warm front associated
with the low and the dry line will uplift the deep moisture,
resulting in widespread shower and thunderstorm development. These
storms are expected to grow upscale into an expansive, organized
convective system into the evening and overnight hours that will
then track southeasterly across the risk area.
The latest deterministic guidance shows areal average rainfall
totals along the expected path of the MCS in the 2-3" range with
locally higher amounts of 4-6", more than sufficient to lead to
scattered and potentially widespread flash flooding, which has
prompted the level 3/4 Moderate Risk. As is usually the case with
convective systems the exact path and duration will be determined
by more mesoscale details than the guidance can typically pin down
at this time frame, so some areal modification and possible
expansion of the Moderate Risk will be likely over the next couple
of days. The most likely area for expansion would be further to
southeast into more of western Missouri and east-
central/southeastern Kansas. However, given the noted uncertainty
with the evolution of these types of systems at this timeframe,
have limited the extent of the risk area to also overlap where the
greatest support/confidence is shown by the ensemble
mean/probabilistic guidance.
...Eastern Texas through the Central Gulf Coast...
One more day of scattered slow-moving storms is expected on
Saturday across the Deep South between eastern TX and southern
AL/FL Panhandle. The lingering frontal boundary draped north of the
Gulf Coast will begin to lift north during the day and leave
convection widely scattered, but more focused activity is likely
during the morning hours as high pressure over the Tennessee Valley
keeps the thermal/moisture gradient rather sharp and focuses
ongoing thunderstorm activity within PWs above 2". Lingering MCV(s)
from the day 1 period across eastern TX and the Lower Mississippi
Valley could also add locations for more organized thunderstorm
activity. The soils in this region also remain extremely saturated
and sensitive to additional intense rainfall rates, leading to the
potential for scattered instances of flash flooding on Saturday and
the SLGT risk of excessive rainfall.
Snell
Day 2 threat area:
www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
328 AM EDT Fri Jun 19 2026
Day 3
Valid 12Z Sun Jun 21 2026 - 12Z Mon Jun 22 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM EASTERN
OKLAHOMA AND THE OZARKS THROUGH MUCH OF THE MIDWEST AND OHIO VALLEY...
...Midwest...
By the start of the day 3 forecast period a potent shortwave and
related surface low are expected to eject eastward out of the
central Plains into the Midwest. There remains some uncertainty
regarding the speed and latitude of these features, but PWs above
the 90th climatological percentile (per the 00z GEFS) overlapping
with soils likely still recovering from recent heavy rain in the
Midwest will lead to at least scattered flash flooding concerns.
NBM probabilities for at least 2" are very high (between 60-80%)
and cover much of the northern SLGT risk area from MO/IA to OH.
Locally higher totals are likely given the convective environment.
The progressive nature of these storms may end up limiting the
severity of flash flood impacts, but a MDT risk upgrade is possible
should training/back- building elements become more obvious in the
short range updates, particularly along the leading warm front
ahead of the primary surface low.
...Southern Plains, Ozarks, and Lower Ohio Valley...
The setup on Sunday could lead to a southern secondary axis of
heaviest QPF and flash flooding impacts. The southern end of the
Saturday night thunderstorm complex/MCS is likely to sink
southeastward near a trailing cold front and impact areas near the
Ozarks early Sunday. Then, the expectation is for reforming
scattered convection during peak daytime heating and reorganization
of thunderstorms overnight Sunday associated with the LLJ to span
from OK to the Lower Ohio Valley, including northern AR, southern
MO, and western TN/KY. This combines for guidance to currently
depict current QPF amounts of 2-4" and an average localized max of
6". There remains obvious mesoscale uncertainties at this stage,
but with Pws near the 90th climatological percentile and a
favorably oriented west- east frontal boundary, it's possible a MDT
risk upgrade may be needed once CAMs come into forecast range. For
the Lower Ohio Valley in particular, some guidance also highlights
thunderstorms associated with the initial warm front lifting
northward, which could add yet another potential for slow-moving
repeating thunderstorms.
Snell
Day 3 threat area:
www.wpc.ncep.noaa.gov/qpf/99epoints.txt
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
328 AM EDT Fri Jun 19 2026
Day 4 and Day 5
Valid 12Z Mon Jun 22 2026 - 12Z Wed Jun 24 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE SOUTHERN PLAINS, LOWER MISSISSIPPI AND TENNESSEE VALLEYS, AND
CENTRAL APPALACHIANS ON DAY 4...
Day 4 continues to an active pattern through a good portion of the
CONUS, east of the Mississippi with a progressive trough axis
pushing through the Great Lakes and Northeast leading to periods of
moderate to heavy rainfall from the Ohio Valley into the Mid
Atlantic and Northeast. Areas of the Northeast are subject to
thunderstorm prospects with the best chance for flash flooding
likely to occur in the urban footprint from Philadelphia up to
Boston with an expansion inland to the Hudson Valley down through
eastern PA. Current probs off the latest ensembles and National
Blend indicate a large zone of 50-80% probs for >1" across the
aforementioned area above with deterministic outputs closer to
2-2.5" into parts of Southern New England. MRGL risk inherited
remains in effect, but there's potential here for an upgrade as we
move closer to the D4 window, but want to see more of the CAMs to
make that decision.
Across the Southern U.S., heavy precipitation will preclude another
round of convection forming along a quasi-stationary front draped
from the Southern High Plains to the Southeastern CONUS. Probs for
>1" are highest in-of the areas of Eastern OK into the Lower
Mississippi and southwestern Tennessee Valleys. Elevated theta_E's
and PWAT anomalies +2 dev. or greater indicate a formidable
environment capable of continued heavy rain potential that will
likely produce rainfall of 2-4", at least in some of the
thunderstorm activity that develops. The focal point along the
front will likely be where the heaviest rain will occur, or at
least be a low-level convergence mechanism that can enhance
regional convection. There's high enough confidence in the location
of convection for the D4 period to overlap with areas that will
have seen several inches the periods prior which led to an upgrade
to a SLGT risk positioned over portions of the Southern Plains
through parts of the Lower Mississippi and neighboring Tennessee
Valleys. The risk extends through the Smokey Mountains up into
parts of the Central Appalachians in eastern KY up into WV as the
convergence regime follows the frontal positioning over these
areas.
Day 5 is a transition period into a more typical summer time regime
for the CONUS with a longwave trough over the Northern U.S. and a
dome of mid and upper ridging positioning itself across the
Southwest. This will cause a persistent northwesterly flow pattern
across the Central and Southern High Plains over into the Lower
Mississippi Valley as progressive shortwave pulses eject out of the
Rockies and ride the prevailing northwesteries in place between the
ridge and trough. This highlights potential for MCS development and
flash flooding scenarios from the Front Range and points southeast
as the steering flow orients between the base of the trough and the
northeastern flank of the ridge. This is historically projecting a
case of thunderstorm maturation and upscale growth over the area
between CO/KS down through OK/TX with potentially the Red River
Basin as a focus for thunderstorm activity. Eventually this ends up
migrating into the ArkLaTex and/or Lower Mississippi area which is
showing up in the QPF footprint on ensembles. With this becoming a
more stable signal in the global ensembles and aligning with the
NBM QPF output, a MRGL risk was added to the new D5 to account for
this potential evolution.
Kleebauer
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
328 AM EDT Fri Jun 19 2026
Day 4 and Day 5
Valid 12Z Mon Jun 22 2026 - 12Z Wed Jun 24 2026
...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
THE SOUTHERN PLAINS, LOWER MISSISSIPPI AND TENNESSEE VALLEYS, AND
CENTRAL APPALACHIANS ON DAY 4...
Day 4 continues to an active pattern through a good portion of the
CONUS, east of the Mississippi with a progressive trough axis
pushing through the Great Lakes and Northeast leading to periods of
moderate to heavy rainfall from the Ohio Valley into the Mid
Atlantic and Northeast. Areas of the Northeast are subject to
thunderstorm prospects with the best chance for flash flooding
likely to occur in the urban footprint from Philadelphia up to
Boston with an expansion inland to the Hudson Valley down through
eastern PA. Current probs off the latest ensembles and National
Blend indicate a large zone of 50-80% probs for >1" across the
aforementioned area above with deterministic outputs closer to
2-2.5" into parts of Southern New England. MRGL risk inherited
remains in effect, but there's potential here for an upgrade as we
move closer to the D4 window, but want to see more of the CAMs to
make that decision.
Across the Southern U.S., heavy precipitation will preclude another
round of convection forming along a quasi-stationary front draped
from the Southern High Plains to the Southeastern CONUS. Probs for
>1" are highest in-of the areas of Eastern OK into the Lower
Mississippi and southwestern Tennessee Valleys. Elevated theta_E's
and PWAT anomalies +2 dev. or greater indicate a formidable
environment capable of continued heavy rain potential that will
likely produce rainfall of 2-4", at least in some of the
thunderstorm activity that develops. The focal point along the
front will likely be where the heaviest rain will occur, or at
least be a low-level convergence mechanism that can enhance
regional convection. There's high enough confidence in the location
of convection for the D4 period to overlap with areas that will
have seen several inches the periods prior which led to an upgrade
to a SLGT risk positioned over portions of the Southern Plains
through parts of the Lower Mississippi and neighboring Tennessee
Valleys. The risk extends through the Smokey Mountains up into
parts of the Central Appalachians in eastern KY up into WV as the
convergence regime follows the frontal positioning over these
areas.
Day 5 is a transition period into a more typical summer time regime
for the CONUS with a longwave trough over the Northern U.S. and a
dome of mid and upper ridging positioning itself across the
Southwest. This will cause a persistent northwesterly flow pattern
across the Central and Southern High Plains over into the Lower
Mississippi Valley as progressive shortwave pulses eject out of the
Rockies and ride the prevailing northwesteries in place between the
ridge and trough. This highlights potential for MCS development and
flash flooding scenarios from the Front Range and points southeast
as the steering flow orients between the base of the trough and the
northeastern flank of the ridge. This is historically projecting a
case of thunderstorm maturation and upscale growth over the area
between CO/KS down through OK/TX with potentially the Red River
Basin as a focus for thunderstorm activity. Eventually this ends up
migrating into the ArkLaTex and/or Lower Mississippi area which is
showing up in the QPF footprint on ensembles. With this becoming a
more stable signal in the global ensembles and aligning with the
NBM QPF output, a MRGL risk was added to the new D5 to account for
this potential evolution.
Kleebauer
