Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
821 PM EDT Mon Jun 15 2026

Day 1
Valid 01Z Tue Jun 16 2026 - 12Z Tue Jun 16 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR MUCH OF THE
TEXAS GULF COAST AND SOUTHEAST TEXAS AS WELL AS FOR A PORTION OF
CENTRAL-SOUTHWEST LOUISIANA AND INTO WEST-CENTRAL MISSISSIPPI...

01Z Update: Significant rainfall remains the forecast this evening
into early Tuesday morning across southern and eastern TX into the
Central Gulf coast region with an alignment of heavy rainfall
positioned near a quasi-stationary boundary analyzed along I-20 in
LA/MS. Surface low situated south of the lower RGV is aiding in
regional low-level convergence and surge of PWATs between 2.2-2.7
up through all of southern and eastern TX with some indications of
PWATs approaching 2.8-3.0" based on the latest RAP analysis. 18z
HREF and recent HRRR/RRFS runs continue to benefit the current MDT
risk initiated across the aforementioned areas with probs in the
ensembles really pinning a region of 2-5" of rainfall as an areal
average from the lower RGV up through the TX coastal plain,
extending north into LA/MS. Environmental conditions will be ripe
for rainfall rates to breach 2"/hr with 3-4"/hr rates not out of
the question as warm rain processes will be prevalent across the
affected area as WBZ heights are forecast between 14-16k ft, a
textbook example of tropical airmass presence and sufficient deep
layer moisture.

Highest probabilities for flash flooding will be situated across
Deep South TX within the proximity of a surface trough extending
north of the low level center positioned south of the lower RGV.
After 06z is when we'll see a slow push of the convergence zone and
increasing rainfall threat for areas further north along the TX
coast, eventually making headway into the Central Gulf coastal
areas of LA. Quasi-stationary front to the north will act as an
inflection point for available low-level ascent as the flow will
eventually make its way north with a strengthening BL convergence
signature popping up between 07-12z Tuesday morning. Hi-res has
been insistent on a regeneration of cells across the I-10/20
corridors and areas in-between putting areas within the upper TX
coast to southwestern LA at play for significant rainfall the end
of the period into the current D2. Rainfall will still be occurring
over the Central Gulf prior, so the grounds will remain saturated
with no reprieve in sight. Expect isolated flash flood prospects
initially between 00-07z this evening with a potential for more
scattered flash flood chances prior to sunrise.

Considering all the above, the MDT was maintained with a greater
than normal prospect for significant flash flooding over much of
south TX and along the TX coastal plain into the I-10/20 corridors
in LA into southwest MS.

Lingering heavy rainfall across eastern FL will maintain a low-end
flash flood prospect into the urban corridor before dwindling after
02z. Maintained a MRGL risk to account for the continued activity
over the area.

Kleebauer
 

Day 2
Valid 12Z Tue Jun 16 2026 - 12Z Wed Jun 17 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR THE ENTIRE
TEXAS GULF COAST INTO SOUTHWEST/CENTRAL LOUISIANA AND CENTRAL
MISSISSIPPI...

...Texas Gulf Coast...

20Z Update...
Today's update to the day 2 outlook included an expansion of the
MDT risk through central LA into central MS, which matches the
continuous plume of moisture and convergence axis extending
northeast from the strengthening mid-level cyclone over South Texas
early Tuesday. Expectations are for ongoing activity Tuesday
morning across coastal TX to gradually shift offshore during the
day, with lingering impacts crossing over from day 1. Some
uncertainty remains regarding a more consolidated area of low
pressure over the far northwest Gulf by Tuesday night and a
developing feeder band to the east-northeast of this low. Most
guidance keeps this highly efficient rain producing rain band
offshore, but if it makes it any distance inland extreme rainfall
and significant impacts for the TX Coast are possible.

Snell

Previous Discussion...
A plume of incredibly deep tropical moisture over the entire Texas
Gulf Coast will be in place at the start of the period Tuesday
morning. Ongoing lee cyclogenesis in advance of a strong upper
level disturbance will support continuous numerous showers and
thunderstorms in the onshore flow up the western coast of the Gulf
and into the Texas Gulf Coast. This disturbance will further
increase the amount of moisture available for the storms, as PWATs
rise to record territory in some areas, possibly exceeding 2.75
inches. Any and all storms that continue to develop ahead of the
low will be capable of multiple inch/hour rainfall rates, despite
the reduced instability in the early morning. When added to
Monday's rains, flash flooding is likely to continue all along the
Texas Gulf Coast until the low itself, which will track
northeastward roughly parallel to the coast passes a given
longitude, switching the wind direction from onshore southward to
offshore northwestward. Since the low will be barely moving, a
steady onshore flow across the middle and upper Texas Gulf Coasts
will continue to favor training storms impacting coastal areas,
with the Houston Metro remaining particularly vulnerable. Meanwhile
for the lower Texas coast, once the low moves offshore, the
northwesterly flow will dramatically decrease storm coverage and
intensity, though not completely shut it off due to the deep
moisture still in place even behind the low, with the front lagging
behind along the Rio Grande.

There is considerable uncertainty as to the northern and western
extent of the rainfall threat on Tuesday. The cold front bringing
much drier air will continue its progress south and east across
South Texas, so the threat will end from west to east during the
day. Meanwhile extensive cloud cover should limit instability well
away from the coast. Thus, the storms will have a progressively
narrowing portion of the Texas Gulf Coast that they will be able to
impact. Regardless, heavy rain will continue to impact the Lower
Texas Coast from the D1 period into Tuesday morning, and the heavy
rains will continue further up the coast throughout the period.
This supports a continuation of the Moderate Risk into the
southwest corner of Louisiana.

Wegman

...Lower Mississippi Valley to Southeast...

20Z Update...
Much of the Lower Mississippi Valley and Southeast will remain in
the favorable right-entrance region of a stout upper-level jet
centered over the southern Appalachians. This will allow for ample
moisture to flow northeastward out of the western Gulf and
thunderstorms to focus along a lingering stationary front.
Thunderstorms and widespread shower activity should start out well
inland during the daytime and then shift to focus along the coast
after sunset and overnight into Wednesday morning. The 12Z HREF and
REFS highlight coastal MS, AL, and the FL Panhandle as having
30-60% chances for 3" in 6 hours.

Snell

Previous Discussion...
Heavy rains across western Mississippi are likely to redevelop in
the same area along the I-20 corridor during peak heating Tuesday
afternoon, and perhaps in some areas never completely stop Tuesday
morning from any overnight rainfall. The front driving the heaviest
rainfall with the strongest storms will be completely stationary
over Mississippi, whereas in Louisiana and points west, it will
continue painfully slow south and eastward progress. Thus, when
storms refire Tuesday afternoon, they will be over many of the same
hard hit areas of central Mississippi as on Monday. Further east,
on Monday the storms will align east-southeastward from western
Mississippi to northern Florida. By Tuesday however, northward
progress of the front as a warm front will allow the heaviest
rains to impact further north into Alabama and Georgia. Despite a
lack of rain on Monday, the still wet soils across central Alabama
towards Birmingham and Montgomery may require an eastward
extension of the Moderate Risk area into central Alabama.
Regardless it appears western Mississippi will still be the area
that gets the most rain, especially over the combined 2 day period.
Rains in west central Mississippi should diminish with loss of
daytime heating Tuesday night with lingering storms pressing
southeastward toward southern Alabama and the Florida Panhandle
Tuesday night.

Wegman

...Southeast Florida...

Added a MRGL risk for the urban corridor of southeast FL for
Tuesday. PWs remain around 1.7-2.0" and the overall pattern remains
similar to previous days as an upper ridge axis remains near and to
the south of the region. This likely leads to a diurnal cycle of
thunderstorms developing along a weak axis of convergence along the
coast, with these storms slow to move and eventually weaken before
sunset. Given the overlap of these storms, the potential for 2"/hr
rates, and the highly sensitive urban corridor of southeast FL a
MRGL risk was introduced for this time period.

Snell
 

Day 3
Valid 12Z Wed Jun 17 2026 - 12Z Thu Jun 18 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR THE UPPER
TEXAS GULF COAST INTO SOUTHWEST LOUISIANA...

...Upper Texas Gulf Coast into Southwest Louisiana...

A potent upper level disturbance with an incredibly deep moisture
plume over the western Gulf to continue a multiple day heavy
rainfall event over a small portion of the upper Texas Gulf Coast
on Wednesday. The disturbance itself will make better forward
progress during the period, moving from off South Padre Island at
the start of the period towards the central/western Louisiana
coastline by Thursday morning. Immediately in advance of the
center of this low, heavy rains will continue into the upper Texas
Gulf coast from the D2/Tuesday period. The axis of heaviest
rainfall through the day is likely to be directed east of Houston,
along the Texas/Louisiana border near Beaumont. Thus, this area is
likely to see the worst impacts from flash flooding overall through
the day. The strongest storms will become increasingly tied to the
movement of the surface low and attendant upper level shortwave,
as the front that plagued much of Texas will follow behind the low,
clearing much of the rest of the state from heavy rains for a
brief time. Across the South, the front that was stalled from
central Mississippi through Georgia the past few days will
dissipate entirely in advance of the next strong cold front.
tracking across the Midwest.

Uncertainty remains with the speed and therefore eventual eastward
progression of this are of low pressure, which impacts where
confidence exists in flash flood impacts by Wednesday. Guidance
today has trended faster and east, which prompted the expansion of
the MDT and SLGT risk areas across LA. More changes are likely as
guidance comes into better agreement on the location and speed of
this system.

Since the upper Texas Coast area will have been hard hit on 2
consecutive days prior to Wednesday, the Moderate Risk continuation
into Wednesday was needed due to likely ongoing heavy rains through
the period. While there's better certainty into southwest Louisiana
for Moderate Risk level heavy rains, the Houston Metro was included
in coordination with HGX/Houston, TX forecast office due to
uncertainty largely on Wednesday morning as to how far west the
heavy rain shield will extend at that time. If guidance continues
to hedge eastward the risk level could be lowered for southeast TX
on Day 3.

Wegman/Snell

...Midwest...

20Z Update...

Only change to this outlook area with to shrink the MRGL and SLGT
on the northern section of the area where instability will be
limited across central WI and the northern L.P. of MI.
Otherwise, the forecast for scattered flash flooding appears to
remain consistent with latest model guidance.

Snell

Previous Discussion...
A potent area of low pressure over the Plains at the start of the 
period will progress east across the Midwest at a rather fast clip 
through the day on Wednesday. As the low moves into the mid- 
Mississippi Valley, it will increasingly tap into the large 
moisture plume present across much of the Southeast. The low will 
create its own moisture feed allowing the moisture to rapidly 
advect into the Midwest ahead of the low. The area from northern 
Illinois into Indiana has also been hard hit by periodic rounds of 
heavy rain in recent days, allowing for moist soils and high river 
levels to remain. Light rains at times are expected in the area 
Tuesday afternoon and evening, but due to lack of moisture, no 
significant flash flooding concerns are expected then. By Day 
3/Wednesday however, the tap into the Gulf moisture will change all
that. Numerous showers and thunderstorms will develop along the 
cold front ahead of the low as PWATs rise well above 1.5 inches, 
reaching as high as 2 inches at times. This will support storms 
capable of 1-3 inch per hour rainfall rates Wednesday afternoon 
through the overnight. The storms will be very fast moving, which 
will reduce the flooding threat, but the aforementioned moist 
soils, urban concerns, and increasing availability of deep moisture
will all support the potential for widely scattered instances of 
flash flooding. Expect a warm front to move across the area around 
midday to early afternoon, then a strong cold front to move through
late afternoon through the evening, which may consist of one or 2 
lines of storms. These lines of storms in rapid succession could 
support training- like effects as far as flash flooding potential. 
Given the very favorable hydrology for flash flooding, it's 
possible targeted Moderate Risk upgrades may be needed for portions
of the area, particularly northern Illinois into northern Indiana,
where a higher-end Slight is in effect. 

Wegman
 
Day 4 and Day 5

Valid 12Z Thu Jun 18 2026 - 12Z Sat Jun 20 2026
...THERE IS A MODERATE SLIGHT RISK OF EXCESSIVE RAINFALL FOR
PORTIONS OF THE LOWER MISSISSIPPI VALLEY & CENTRAL GULF COAST ON
DAY 4...

20Z Update: The main changes for the D4 period were the expansion
of the risk areas, including the MDT risk, further eastward to
account for the trends in being slightly faster with the PWAT surge
and mid-level vorticity ejection. This was noted within the global
ensemble means and correlated with a slight uptick in the pQPF
probs for the 1/2/3 inch thresholds. Maxima within the probs was
noted across south-central MS, expanding east to right around
western AL. Highest confidence given probability consensus was
across southern MS, so decided to align the MDT over the region
encompassing much of the Jackson, MS CWA bounds. The SLGT risk was
also expanded further east and north to account for the anomalous
PWAT advection regime anticipated by mid-week and beyond. The
expansion was to target the southern Appalachian front with
emphasis on northern GA into the escarpment of SC and western NC.
We'll be monitoring the trends closely as a further east push would
indicate a further expansion of the risks to the east, including
more of the I-20 corridor where Birmingham, AL and even
potentially Atlanta, GA becoming in play for a higher risk. In any
case, it's certainly the period to watch in the medium range for
enhanced impacts.

D5 is when we hit the back end of the more appreciable rainfall
prospects, however lingering deep layer moisture of tropical origin
will still allow for efficient warm rain processes and the ability
for continued heavy rainfall through a good portion of the
Southeastern U.S. up into the Southern Appalachians. The main
change was an expansion of the SLGT risk further north through the
southern Appalachians with a northern advancement into southwestern
VA. There's some discrepancy on the eastward extent of the
heaviest precipitation, however there was enough consensus to bring
the SLGT north in the terrain and maintain the high-end SLGT
posture across the Central Gulf coast into interior AL/MS.

Kleebauer

..Previous Discussion..
Attention is on the multi-day Excessive Rainfall threat in the
Deep South where an abundance of tropical moisture will engulf
areas from southeast TX to as far east as GA. There are notable
timing differences across guidance on the placement of the heaviest
rainfall, and this will come down in large part to the development
of the low-level disturbance in the western Gulf. Both its
development and track will likely be troublesome for guidance to
key in on for another 24-36 hours until the circulation is formed
over South TX. That said, the region in total will have witnessed
multiple rounds of Excessive Rainfall, particularly east TX,
central and northern LA, and into western MS in lead up to Day 4.
The 12Z ECMWF EFI showed a notable overlap of >0.7 signals from
southwest LA on east into central MS, including at least a 2
contour on the Shift of Tails. In collaboration with several WFOs
along the central Gulf Coast and the Lower MS Valley, a Moderate
Risk was issued to account for the concerns of additional Excessive
Rainfall over areas that will likely be dealing with ongoing flash
flooding in the days leading up to Thursday. It is worth noting
that the same axis of anomalous moisture in the South will stream
north into the TN/OH Valleys. These areas will have the benefit of
strong synoptic-scale forcing to produce widespread thunderstorms.
A Slight Risk stretches as far north as southwest PA to account for
flash flooding in these more flash flood prone areas.

Day 5 will see a weak 500mb trough axis over central TX tap into
lingering tropical moisture along the Gulf Coast. Lower pressures
over the Rio grande and persistent high pressure east of the
Bahamas will maintain the seemingly endless moisture tap emanating
out of the Bay of Campeche. Moisture out ahead of the upper trough
will also collide with a frontal boundary that will extend across
much of the South. The future of the upper-level feature that
originated over South TX early in the week may also still play a
key role in Excessive Rainfall, especially from southern LA on
east into northern GA. Accounting for various ensemble guidance
tonight, there is a sufficient signal for Excessive Rainfall in
areas across the South that received copious amounts of rainfall
the first four days of the work-week to be concerned for more
scattered instance of flash flooding that could be locally
significant. A Slight Risk was issued from the Lower Rio Grande
Valley to as far east as the Appalachians of northern GA.

Mullinax
 

Day 1 threat area: https://www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: https://www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: https://www.wpc.ncep.noaa.gov/qpf/99epoints.txt