FOUS30 KWBC 140803
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
403 AM EDT Sun Jun 14 2026

Day 1
Valid 12Z Sun Jun 14 2026 - 12Z Mon Jun 15 2026

...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL FOR THE SOUTHERN
PLAINS AS WELL AS FOR NORTHERN NEW ENGLAND...

...Southern Plains...

Today will likely be the calmest of the next 3 days across Texas,
which isn't saying much as it will still be plenty active. A very
slow moving cold front will sink south across Oklahoma and Arkansas
today. Ahead of the front, an impressively moisture-laden air mass
is in place over not just Texas, but much of the Gulf Coast. Across
eastern Texas, an ongoing MCS across Oklahoma and Arkansas
delineating the leading edge of the aforementioned cold front will
continue to drift south and weaken through the morning hours, which
is typical behavior for MCSs once the sun comes up. While the MCS
will have some forward speed to it, the availability of plentiful
moisture, with PWATs to 2 inches will continue to support heavy
rainfall with the strongest cells. The remnants of the MCS will
likely impact the Metroplex in the mid-to-late morning.

Meanwhile, plentiful southerly flow off the Gulf into southeast
Texas will lead to widespread but largely disorganized shower and
thunderstorm activity from the Houston and San Antonio metros
north. The plentiful moisture will still be available, so anywhere
where cell mergers or localized training features develop,
localized flash flooding will be possible today. Any urban areas
will only increase the flash flooding potential, though there's
considerable uncertainty whether any of the biggest cities in Texas
will be directly impacted.

Across west Texas and the Hill Country, afternoon and evening
thunderstorms will impact those areas, with portions of west Texas
recently hard hit from heavy rains at a higher threat for
additional flash flooding. A higher-end Slight has been issued for
this region. For the Hill Country, the main flooding threat will be
tonight, as an MCS develops due to plentiful merging thunderstorms
and a southward push of the cold front in that region. The storms
will run into increasing resistance tonight in the form of a
strengthening LLJ, which should slow down the forward speed of the
storms as the traverse the Hill Country. Due to the flashy nature
of the terrain in the Hill Country, the higher-end Slight was also
introduced for this region as well. Back into New Mexico,
afternoon and evening storms could interact with both the terrain
features in the area, such as the Sacramento Mountains, urban El
Paso, and any burn scars in the area.

...Northern New England...

A Slight Risk upgrade was introduced with this update in
coordination with BTV/Burlington, VT and CAR/Caribou, ME forecast
offices. The same cold front that will be impacting the Southern
Plains will have a much easier time pushing eastward, as a large
upper level low over Canada pushes frequent shortwave disturbances
east across the northeastern U.S. Despite the progressive nature of
the front, a surge of moisture will rapidly advect north into New
England ahead of the front, aided by increasing upper level support
as a strong shortwave becomes more negatively tilted with time as
it rounds the southeastern periphery of the upper level low. The
moisture surge will also increase the instability, with MUCAPE
values around 1,000 J/kg expected on average, and values up to
2,000 in some areas, including southeastern VT. The plume of
moisture and instability will support numerous fast-moving
thunderstorms training northeastward along the Canadian border. The
training storms will impact recently hard hit areas of northern New
England, where soils are wetter than normal going into this event.
While there's some question as to how strong the storms will get,
the likelihood they will train along and south of the plume of
greatest rainfall is high. The storms will train over northern New
England for several hours before the cold front sweeps across from
west to east tonight. Topographic effects could locally increase
rainfall rates, as well as worsen any possible flash flooding.
This further supports the Slight Risk upgrade for the area.

...Elsewhere...

The Marginal Risk for the Mid-Atlantic and the east coast of
Florida are largely the same. For the Mid-Atlantic afternoon and
evening storms feeding on the same moisture plume that will advance
into New England could lead to localized instances of flash
flooding, especially in urban areas along the I-95 corridor, though
the severe threat appears greater.

On the east coast of Florida, sea breeze interactions with the
abundant moisture over the state should allow for a renewed
development of afternoon and evening thunderstorms today. The
storms will be nearly stationary, so mergers will pose the greatest
threat for more prolonged periods of heavy rain, though all strong
cells will be capable of localized heavy rain.

Wegman


Day 2
Valid 12Z Mon Jun 15 2026 - 12Z Tue Jun 16 2026

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM SOUTH TEXAS
THROUGH THE LOWER MISSISSIPPI VALLEY...

As far as changes to the inherited forecast go, the day 2 forecast
is the most similar to the prior forecast. A strong cold front over
north Texas through southern Arkansas at the start of the day will
continue making painfully slow progress south towards the western
Gulf Coast on Monday. Meanwhile a surge of deep tropical moisture
will actually further increase the amount of available moisture
the storms will have to work with as they push south across Texas.
The MCS from Sunday night along the Rio Grande will continue south
into Monday morning along the Rio Grande and the Texas Hill
Country. This MCS will weaken by midday, only to be replaced with
far more numerous showers and thunderstorms all across southern and
eastern Texas. These storms will form as the surge of moisture and
plentiful instability from the Gulf advects north and west into
southeast Texas. The storms from any morning MCs will quickly
evolve into a slow moving line of storms from east Texas into
Mississippi due to the abundant moisture and instability running
into the very slow-moving cold front roughly near the AR/LA border.
For some areas of east-central Texas, northern Louisiana, and
western Mississippi, there may be no stop between any early morning
rain from overnight MCS and the afternoon convection that quickly
blossoms along the frontal interface. High FFGs and somewhat drier
than normal surface soils going in to the Day 2 (depending on what
happens today), should work to preclude Moderate Risk level
coverage of flash flooding, but the whole area is in a higher-end
Slight and a Moderate Risk upgrade is possible with future updates.

For South Texas, the primary flash flooding threat for the period
will occur overnight Monday night. While the abundant moisture will
be in place in this region, there will be a lack of forcing, due
to the distant cold front over the Hill Country, until the arrival
of a potent upper level disturbance. This disturbance is likely at
least in part the remnant circulation of former East Pacific
tropical storm Cristina. As this feature pushes northeast out of
the mountains of Mexico towards south Texas, it will not only
increase the low level inflow of tropical moisture, but will
provide ample forcing to organize the storms into slow-moving lines
of training cells that track northwestward with time up the Rio
Grande. PWATs will be 4 sigma above normal, exceeding 2.5 inches at
times, so any and all storms will have impressive amounts of
moisture to work with to produce heavy rain. Instability due to
extensive cloud cover commensurate with such amounts of moisture
will likely be the only limiting factor for coverage of heavy rain.
A Moderate Risk may also need to be considered in south Texas
should coverage of storms remain similar with more CAMs coverage and
portions of this area get significant rainfall on Day 1/today.

Wegman

$$
--- SBBSecho 3.28-Linux
* Origin: Capitol City Online (618:250/10)

FOUS30 KWBC 150903
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
503 AM EDT Mon Jun 15 2026

Day 1
Valid 12Z Mon Jun 15 2026 - 12Z Tue Jun 16 2026

...THERE ARE MODERATE RISKS OF EXCESSIVE RAINFALL FOR MUCH OF THE
TEXAS GULF COAST AND SOUTH TEXAS AS WELL AS FOR A PORTION OF WEST-
CENTRAL MISSISSIPPI...

...Texas Gulf Coast and South Texas...

A very impressive setup for flash flooding will begin to unfold
along the Gulf Coast of Texas today, and will continue into future
days. The impressive ingredient is the sheer amount of moisture
that will be advecting north into south Texas and the Gulf coast
over the next few days in advance of a potent upper level low, some
of the remnants of former east Pacific tropical storm Cristina.

PWATs advecting into deep south Texas are likely to broach close to
record territory today, as they climb to as high as 2.75 inches.
This is a function of well above normal sea-surface temperatures
in the Gulf adding low-level moisture, and preexisting upper level
moisture from Cristina. The combination of these could fully
saturate the atmosphere up to the tropopause, with melting layers
as high as 17,000 ft. This will make any storms that develop in
this environment having an almost unnatural ability to produce
heavy rain. As the aforementioned upper level disturbance
approaches and lee cyclogenesis begins east of the Mexico mountains
tonight, expect multiple rounds of storms across Deep South Texas
to impact the area. A westward moving band may start off around
peak heating this afternoon, then as the disturbance approaches
tonight, a nearly stationary or slowly eastward moving band is
expected to develop overnight tonight which will persist for much
of the night as competing forcings create an area of low level
convergence over Deep South Texas. There is some uncertainty as to
where this convergence sets up, but it appears it's most likely
closer to the Rio Grande Valley on the western side of Deep South
Texas. Given the incredible moisture available for the storms,
localized cells could produce rainfall rates as high as 5 inches
per hour, with 3 inch/hour rates common. Despite dry soils going
in, these incredible rain rates will easily overwhelm the areas
experiencing them, resulting in widespread and locally catastrophic
flash flooding, especially in any towns or cities that experience
an extended duration of rainfall rates of that magnitude.

Further north, the north-south oriented bands over Deep South Texas
will impact a strong but slow-moving cold front drifting
southeastward towards the Texas Gulf Coast. This will funnel the
prodigious moisture northeastward paralleling the coast. The storms
will follow, resulting in training. As in Deep South Texas, despite
slightly, and I mean only slightly lower PWATs, rainfall rates to 3
in/hr will be common with localized rates to 5 inches/hour here as
well. FFGs are significantly lower from Corpus Christi northeast to
Houston as compared with further south down the coast, thus, these
prodigious rainfall rates will have no trouble exceeding FFGs.
Frictional convergence of the onshore flow and the front will make
for nearly stationary bands of storms along much of the middle
Texas Coast. Thus, expect storm total rainfall amounts today easily
exceeding 3 inches, but localized amounts will be much higher,
perhaps approaching 8 inches, as noted by the HREF probabilities.
With some uncertainty as to how prolific the storm total rainfall
amounts will be, the Moderate Risk may need to continue to be
upgraded in the hardest hit areas through the day, especially if
those include urban areas from Brownsville through Houston.

...West-Central Mississippi...

The same incredible moisture plume as over Texas is already in
place across all of Louisiana and southern Mississippi this
morning. The same front as in Texas will be even stronger to the
east in Louisiana and Mississippi. Thus, with southwesterly LLJ
flow into this front, expect numerous thunderstorms to develop
across northern Louisiana and west-central Mississippi by midday
today. The storms will run into a "wall" that is the cold front,
forcing them to turn eastward, resulting in a well-defined line of
storms along the frontal interface. It appears this is most likely
to occur along the I-20 corridor. The heaviest rains will occur
from midday through sunset, after which there may be a break before
more scattered convection redevelops in the early morning hours of
Tuesday. Multiple inch per hour rates are likely with these storms
as well due to the deep moisture with PWATs at record territory
between 2.25 and 2.5 inches. Portions of western Mississippi have
been recently hard hit with heavy rains, resulting in wet soils,
and the Jackson area due to urban concerns is also vulnerable to
flash flooding due to heavy rainfall. In coordination with the
JAN/Jackson, MS forecast office, a Moderate Risk upgrade has been
introduced. While soils are less supportive of flooding further
west into northern Louisiana, persistent multiple inch/hour rates
along the I-20 corridor could result in an expansion of the
Moderate Risk with future updates.

Wegman


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

...THERE ARE MODERATE RISKS OF EXCESSIVE RAINFALL FOR THE ENTIRE
TEXAS GULF COAST AS WELL AS FOR WEST-CENTRAL MISSISSIPPI...

...Texas Gulf Coast...

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.

...West Central Mississippi...

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
$$
--- SBBSecho 3.28-Linux
* Origin: Capitol City Online (618:250/10)

FOUS30 KWBC 160821
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
421 AM EDT Tue Jun 16 2026

Day 1
Valid 12Z Tue Jun 16 2026 - 12Z Wed Jun 17 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE TEXAS GULF COAST THROUGH THE LOWER MISSISSIPPI VALLEY...

An impressive and dynamic setup with multiple mesoscale features
is expected to develop through the day today from the Texas Gulf
Coast through the lower Mississippi Valley. The most rainfall for
the day will occur through this morning. A tropical disturbance
over Deep South Texas will support the strengthening of the typical
diurnal low level jet out over the Gulf, driving a plume of
impressively deep tropical moisture northward into the Texas and
Louisiana Gulf Coasts. Meanwhile a stationary front currently over
southern Arkansas and northern Mississippi will advance southward
as a cold front due to a disturbance and push of cooler drier air
south behind the front. This clash of air masses will result in
continued upscale development of storms that have broken out over
northern Louisiana through the overnight and into Tuesday morning.
FFGs are already lower in many spots west from the western tip of
Mississippi. This nearly stationary line of training storms is
likely to persist well into the afternoon, which could make for a
narrow but nevertheless severe area of very high totals of storm
total rainfall, especially into western Mississippi. Guidance has
suggested this narrow corridor, highlighted in much of the guidance
since yesterday along the I-20 corridor has now shifted a few
counties south, extending from Alexandria, LA east almost to
Hattiesburg, MS. The inherited Moderate Risk for this area was
trimmed on the north side both with the current start of convection
in this corridor and the southward trend in the guidance.

Meanwhile, a number of other pieces of CAMs guidance suggest that
the showers and storms developing along the immediate coast roughly
from Galveston/Trinity Bays east to Lafayette, LA will be the
primary and dominant line of showers and storms impacting the
northwestern Gulf Coast today. This line would from largely from
sea breeze/frictional convergence of the strong onshore southerly
flow into the coast. The front to the north may play a role in
maintaining the storms where they are, but would likely play a
secondary role. Should this line develop robustly, it will force
the aforementioned line of storms over northern LA/southwest MS
eastward, resulting in less rain over northern/central LA. Most
likely there will be a combination of the two, with the east-
northeastward moving storms along the southwest Louisiana coast
continuing with the line to the northeast over western Mississippi.
Once again the Moderate Risk here remains in place with few changes.

Finally, further south along the Texas Gulf Coast, the larger
synoptic level disturbance, responsible for the heavy rains and
flash flooding over Deep South Texas yesterday will likely eject
east into the Gulf today. As it does so, it will create localized
bands of heavy rain along the Middle Texas Coast, which will then
advect northeast to join the line east of Houston. This area from
Corpus Christi to Houston remains the most uncertain portion of the
Moderate Risk area, as a small south/east shift in the track of the
disturbance will take the lion's share of the associated rainfall
ahead of the low track out over the open Gulf, and greatly limit
any rainfall today along the coast. The inherited Moderate Risk was
trimmed completely south of Corpus Christi, with just a Slight
along the immediate lower Texas Gulf Coast to account for ongoing
rains in the area. The threat will shift off the coast by late this afternoon.

With all three areas of heavy rain above, they will all diminish
and dissipate as a significant heavy rain threat by this evening.
Occasional showers and a storm or two may impact the immediate Gulf
Coast through the overnight, but for the most part the heavy rain
threat through tonight should be minimal.

Wegman


Day 2
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 THROUGH SOUTHWESTERN LOUISIANA...

...Gulf Coast...

An upper level shortwave disturbance over the northwestern Gulf
will likely contribute to the development of a small surface low
or surface trough along the Texas Gulf Coast on Wednesday. This
disturbance will gradually track parallel to the coast towards the
northeast, and move into southwestern Louisiana this evening. The
exact track of the center of circulation will remain the
distinctive factor determining how much rain penetrates inland
along the Texas coast, including into the Houston Metro. Some of
the CAMs guidance has trended west with the track of the low, which
will prolong a period of heavy rain into Houston as cells ride
northwestward ahead of the low in a small but very potent band of
heavy rain. It will be potent not just because of the multiple
sources of forcing for the heavy rain, but also the sheer amount of
atmospheric moisture that will be available for the storms to tap
into. PWATs will remain exceptionally high, likely peaking in the
upper 2s as the low reaches its peak intensity this afternoon.
While the predominant southerly flow will advect some instability
into the low, extensive cloud cover will work against achieving
heavy rainfall rates in many cases. The hydrology will become
increasingly favorable for flash flooding even with less than
optimal rainfall rates as prior days' rains combine with the new
rainfall to continue lowering FFGs. The Moderate Risk was nudged
west in coordination with HGX/Houston, TX forecast office to
include all of the Houston Metro. Prolonged northwestward moving
cells in a narrow band could easily start causing flash flooding
problems over the Houston metro should the track optimize.

Further east, there is more certainty with heavy rainfall rates
impacting the area from Beaumont east into southwestern Louisiana.
Southerly flow exactly orthogonal to the coast, frictional
convergence, and then the low itself impacting the area from late
in the day Wednesday through Wednesday night will all contribute to
additional heavy rains over an area of Louisiana already hard hit
from the current rain and expected rain in the area on Day 1. The
Moderate Risk area was little changed from inherited in this area.

Further north and east, the heavy rain threat will concentrate over
the Wednesday night timeframe. As the low and associated upper
level disturbance move into Louisiana, a leading band of heavy
rain, oriented southwest to northeast, will overspread portions of
central and eastern Louisiana and continue into western
Mississippi. There is considerable uncertainty how far into
Mississippi the heavy rain gets. But it will likely extend from the
coast south of Lafayette northeast through Baton Rouge and into
southwestern Mississippi. Here too, favorable hydrology due to wet
soils from heavy rains from today/Day 1 will contribute to any
resultant flash flooding. For now, this appears to stay west of New
Orleans, but will likely be too close for comfort, and the New
Orleans Metro could see occasional heavy rain from passing cells.

...Midwest...

Very few changes were needed to the large Slight Risk across much
of the Midwest on Wednesday. A strong and impressively potent low
driving eastward from the Plains will run into increasing amounts
of deep tropical moisture as it moves into the Great Lakes. This
will contribute to increasing coverage of showers and storms, first
with its warm front from Chicago east along Michigan's southern
border, then followed very quickly in some areas by stronger storms
associated with the low's cold front. Favorable hydrology from
several bouts of heavy rain over the past week will support flash
flooding development. However, this low and its associated storms
will be racing eastward. Thus, duration of heavy rain will be very
limiting in many areas. For the corridor forming the northern half
of the Slight Risk area, heavy rain duration will be longer, as the
warm front and associated elevated convection quickly followed by
stronger convection with the cold front could allow for some areas
to see multiple hours with interspersed heavy rain through the day.
Instability may be more limited in this area however, so that will
work against heavy rains.

For the southern half of the Slight, there will be significantly
more moisture and instability for the storms to work with as they
race southeastward, so rainfall rates should be higher than further
north. However, it's likely just the cold front's storms that will
impact most areas, so it's one shot and done. Training and
backbuilding won't be a concern until you get back into Missouri
and Kansas. Once again, the soils remain wet in these areas, so it
may be enough to get widely scattered instances of flash flooding,
particularly in urban areas. As is typical this time of year, the
cold front will hang up on its southern and western periphery, as
it runs into the southwesterly low level jet. This will greatly
extend the potential for heavy rain from southeastern Kansas
through southern Missouri Wednesday night. These areas have also
been hard hit with heavy rain in recent days, as well as the
topography of the Ozarks, so the Slight remains in place there with
few changes.

Wegman
$$
--- SBBSecho 3.28-Linux
* Origin: Capitol City Online (618:250/10)

FOUS30 KWBC 170822
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
422 AM EDT Wed Jun 17 2026

Day 1
Valid 12Z Wed Jun 17 2026 - 12Z Thu Jun 18 2026

...THERE ARE MODERATE RISKS FOR EXCESSIVE RAINFALL FOR THE
CHIACAGOLAND REGION AS WELL AS FOR PORTIONS OF THE MISSISSIPPI DELTA...

...Chicagoland...

A potent low racing out of the Plains and across the Great Lakes
today will run into an increasingly moist air mass in place ahead
of the low over the Midwest. As the low approaches the Chicagoland
region late morning, convection will break out along the low's warm
front extending east of the low center. The initial hit of rain
with the warm front is unlikely to feature too much heavy rain,
though embedded elevated convection could make for brief heavier
downpours. Immediately behind the warm front, however, a surge of
moisture and instability will fuel backbuilding thunderstorms
during the afternoon ahead of a strong cold front trailing behind
the low. These storms are progged by many of the CAMs to generate
into several broken lines of storms as they cross northern Illinois
and into northern Indiana and southern Michigan through the late afternoon/early evening. These storms will have ample forcing
allowing them to organize into severe clusters of storms. They are
likely to locally produce rainfall rates of up to 2 inches per hour
where they backbuild. However, since the series of line segments
will be sufficiently separated by much lighter or no rain, it seems
any flash flooding that results from these storms will be more
localized and less widespread. Further, as mentioned, the storms
will be racing very quickly, likely moving at 40+ mph. This will
greatly reduce the time any one area sees heavy rain, but since the
lines are expected to align parallel to the windflow, those areas
may see a bit longer time of heavy rainfall.

Hydrologically, the Chicagoland area has seen several bouts of
heavy rain in recent weeks that have left the soils above normal
for moisture content as well as prone to flash flooding with
sufficiently heavy rain. Of course, the large urban area of Chicago
will also help to worsen any flash flooding that develops, so in
those local areas where heavy rain overlaps with urban areas,
locally considerable flash flooding is possible. Further east into
Indiana, eastern Michigan, and eventually northwestern Ohio, the
lines of storms this evening should align with the cold front and
largely orthogonal to the flow. This should lower the flash
flooding risk in these areas, despite similarly favorable hydrology.

...Mississippi Delta...

The moisture plume of Potential Tropical Cyclone 1 (PTC1) will
continue to slowly advect northeast across the northwestern Gulf
and into southern Louisiana today into tonight. For much of the
day, the heaviest rains will remain offshore, and except for
occasional showers and an isolated storm or 2, much of the area
should not contend with much heavy rain. That changes tonight as
the center of circulation of what may be Tropical Storm Arthur
moves ashore near the TX/LA border. All of the deep moisture will
be east of the center of circulation, so that will direct the
fire-hose of heavy rain into south-central Louisiana, from the
Abbeville/New Iberia area northeast near Baton Rouge and into
southern Mississippi after midnight. By that point, the diurnal
strengthening of the nocturnal jet will function as the the primary
driver of heavy rain as northeastward moving storms backbuild into
the jet. The area from around Baton Rouge northeast to the north of
Lake Pontchartrain and into far southern Mississippi is likely to
be the corridor with the heaviest rain.

There is considerable uncertainty first of the eastern extent of
the axis of heaviest rain, particularly in relation to the New
Orleans Metro. For now most of the guidance makes a very tight
gradient of moisture, which most of the city remains on the drier
side of. However, this axis of heaviest rain has been shifting
east from model run to model run over the last couple days, which
any further eastward drift would bring New Orleans right into the
corridor of multiple-inch per hour rainfall for multiple hours.
Regardless, even if New Orleans misses out on the heaviest
rainfall, feeder bands of showers and storms could still cause
localized flash flooding in the city. Thus, the Moderate Risk
remains largely unchanged and includes New Orleans. More than a
couple CAMs do bring strong cells over the city, which would very
quickly lead to flooding problems.

Wegman


Day 2
Valid 12Z Thu Jun 18 2026 - 12Z Fri Jun 19 2026

...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHEAST...

...Southeast...

Very heavy rain associated with what will be the remnants of PTC1
will be ongoing at the start of the period over most of southern
Mississippi and likely extending into southwestern Alabama. These
storms will be fueled by a strong low level jet pumping deep
tropical moisture into a corridor that covers much of the Moderate
Risk area. By around midday, the rapidly increasing instability and
the typical weakening of the low level jet will allow the
widespread convection to transition into training lines of storms
that track east with time, as the line gradually drifts south
towards the greatest instability and moisture source that is the
Gulf. Thus, the greatest focus of heaviest rain now appears to set
up from southeastern Mississippi east across the southern tier of
Alabama and far western Georgia. 3+ inch/hour rainfall rates from
individual storms will combine with multiple hours of rain as the
storms train along the east-west oriented lines. Storm total
rainfall for the day could easily exceed 8 inches in spots. Mobile,
AL will be the biggest city in the crosshairs of the heaviest rainfall.

With this rather dramatic southward shift in the guidance of where
the heaviest rainfall totals are expected, the Moderate Risk
inherited was trimmed significantly on the north side, while
expanded across southeast Alabama, the western Florida Panhandle,
and far southwestern Georgia. The Moderate Risk was downgraded out
of both the Birmingham and Atlanta metros as those areas see
leftover heavy rains from the much more potent and heavy rain
producing storms much closer to the Gulf Coast. Nonetheless,
periodic convection and a long duration of light to moderate rain
is still expected over those metros, so the higher-end Slight
remains in effect. Convective coverage greatly decreases Thursday
night over all of the Southeast, but isolated to widely scattered
storms could persist through the night in some areas.

...Ohio/Tennessee Valleys...

Further north from the Gulf Coast along the Ohio and Tennessee
Valleys, a cold front will start the day following roughly parallel
to the Ohio River. The front will slowly sink southward over
Kentucky through the day. Meanwhile, daytime heating and
unidirectional southwesterly flow ahead of the front is expected to
generate a long line of storms. The storms will be training and
backbuilding along the KY/TN border and extending into West
Virginia. Guidance has shifted a bit further south, especially with
the western end of the line, so the higher-end Slight now follows
the entire length of the KY/TN border, and now includes Nashville,
while the Ohio River has largely been removed from the risk area.
With nightfall and the loss of daytime heating, the flash flooding
risk from storms will also diminish.

...Arkansas/Oklahoma...

On Thursday night, the westernmost extension of the low-level jet
over Texas will run into the same stalled out front that extends
east into Kentucky. This clash of air masses is likely to result in
the development of an MCS over eastern Oklahoma, which will then
propagate southeastward into western Arkansas. Here too the soils
are wetter than normal from multiple bouts of heavy rain in recent
weeks, so a Slight Risk remains in place over the area with few changes.

Wegman
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* Origin: Capitol City Online (618:250/10)