• HVYRAIN: Excess Rain D3-5

    From Mike Powell@618:250/10 to All on Sun Jun 14 08:16:43 2026
    FOUS30 KWBC 140803
    QPFERD

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

    Day 3
    Valid 12Z Tue Jun 16 2026 - 12Z Wed Jun 17 2026

    ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR THE WESTERN AND
    CENTRAL GULF COAST...

    ...South Texas...

    The entire focus of heavy rainfall across South Texas Tuesday will
    be the speed of movement of the upper level disturbance which
    likely in part the upper level circulation of former east Pacific
    tropical storm Cristina. The global guidance is in alright
    agreement, but it could certainly be better. The EC is far slower
    with its movement than the GFS. For this period, the difference
    between the two is small enough that there is at least some
    confidence in the subsequent meteorological effects. Essentially
    the upper level Pacific moisture with Cristina will combine with
    exceptionally deep Gulf moisture along the western periphery of the
    Gulf, to raise PWATs to near record territory for this time of year
    for some areas of deep south Texas, particularly along the coast.
    With the disturbance in place, and strengthening with time, this
    abundant moisture will be focused into slow-moving bands of heavy-
    rain producing thunderstorms. PWATs will exceed 2.5 inches along
    the coast, with some areas even nearing 2.75 inches. The exact
    track of the slow-moving disturbance will be key as to who sees the
    most rain, as the storms ride north off the Gulf and into coast to
    the east of the center of circulation.

    Rain wrapping around the circulation will spread west across all of
    deep south Texas, right to the Rio Grande. This will lead to a
    second consecutive day with exceptional rainfall totals in spots,
    with areal average rainfall for the period likely exceeding 3
    inches (with much higher localized amounts) from essentially
    Galveston south and west. At the moment, the heaviest totals look
    to concentrate for the portion of south Texas from Corpus Christi
    south and west to the Rio Grande, but again any change in track or
    speed of the upper low and any possible surface circulation will
    change this dramatically. Regardless, considering the overlap from
    the Day 2/Monday period, should this rainfall forecast remain
    similar with future updates, a Moderate Risk will be necessary as
    FFGs in this area will be much lower than they are now. Further,
    there will be urban flooding impacts from Brownsville to Corpus
    Christi as well.

    ...Louisiana into the South...

    Up the coast from south Texas, the plume of abundant Gulf moisture
    will continue to stream north into the slow moving front that will
    remain set up from east Texas through northern Louisiana and into
    western Mississippi. The good news for Tuesday is that the likely
    influence of the upper level low over deep south Texas/Mexico will
    make for downstream ridging, which should limit the coverage of
    heavy rain from Houston east across the South. That said, the front
    will still be a potent forcing feature, and training storms
    tracking east parallel to the front will still pose a localized
    flash flooding problem. Thus, the inherited Slight for this region
    remains in place, especially considering the likely much more
    favorable hydrology as this will be the second or third day
    (depending on where you are) of heavy rain for this region. This
    will likely offset the somewhat lighter rainfall totals expected
    Tuesday and Tuesday night. A faster forward speed of the upper
    level disturbance could also re-increase the rainfall forecast for
    this region and also push some areas close to Moderate Risk
    territory with future updates.

    Wegman


    Day 4 and Day 5

    Valid 12Z Wed Jun 17 2026 - 12Z Fri Jun 19 2026

    ...THERE ARE SLIGHT RISKS OF EXCESSIVE RAINFALL FOR PORTIONS OF
    MIDDLE MISSISSIPPI VALLEY, OHIO VALLEY, MID-SOUTH, AND GULF COAST
    ON DAY 4 AND DAY 5...

    An anomalous upper-level pattern will be the catalyst for active
    days 4-5 timeframe from the Gulf Coast on north to the OH Valley
    and as far east as the central Appalachians. Southeast TX and
    portions of the Deep South will also experience widespread thunderstorms.

    On Day 4 (Wed.) a robust 500mb vorticity maximum will spawn a
    strong area of low pressure at the nose of a 500mb jet streak.
    ECMWF SAT percentiles show show MSLP values that are among the
    lowest in the CFSR database (1979-2009) over the Midwest by 00Z
    Thursday that continue into early Thursday morning over the Great
    Lakes. 850mb winds will be roaring to the tune of 50 kts and
    potentially stronger than that over the OH Valley. The combination
    of highly anomalous low pressure over the Midwest paired with high
    pressure south of Bermuda will force Gulf moisture to race
    northward into the Middle MS Valley and on east into the OH Valley.
    With PWs also above the 90th climatological percentile, storms may
    be fast movers, but they will contain efficient warm rain
    processes. A Slight Risk was introduced from the MS Valley to as
    far east as central OH to account for the increased flash flood
    potential. Farther south, the pool of anomalous PWs accompanied by
    a strengthening southerly IVT over the western Gulf will keep the
    TX Coast at risk for Excessive Rainfall. While guidance still shows
    some differing solutions, the region will only continue to see
    soils grow more sensitive after multiple days of rain prior to
    Wednesday. A Slight Risk was introduced for the Lower and Central
    TX Gulf Coast, aligning with where the heaviest WPC QPF is located.

    For Day 5 (Thurs.), between the NAEFS and ECMWF SATs, the
    southerly winds within the 1000-500mb layer over the western Gulf
    are remarkable with the entire layer's southerly wind anomalies
    averaging at least the 97.5 climatological percentile. This means
    the Gulf is wide open for business, not just with low-level
    moisture but into the mid-to-upper levels as well. ECMWF and GEFS
    ensemble means on Day 5 have PWs above 2.2" over the central Gulf
    Coast with >90th climatological PWs as far north as the OH Valley.
    A strong cold front will trigger widespread thunderstorms within
    this environment that is likely to pose a flash flood threat in
    portions of the recently more sensitive soils of the OH and TN
    Valleys, leading to the issuance of a Slight Risk in these areas.
    Farther south, guidance shows varying solutions of what could
    transpire in east TX. The 12Z ECMWF EFI has a swath of >1 Shift of
    Tails (SoT) from east TX to as far north as northern MS, and even a
    small >2 SoT north of I-10 in east TX, indicating a signal for
    locally significant rainfall being possible in these areas. The
    details on the development of low pressure in the Deep South remain
    unclear. That said, there is no denying the copious amounts of
    moisture at these thunderstorms disposal and soils throughout the
    region will have only grown more sensitive after multiple days of
    Excessive Rainfall. A Slight Risk was introduced over the Upper TX
    coast on east into southwest LA where it aligns with not only the
    ECMWF EFI signal but the overlap with the more anomalous moisture
    content and the heavier WPC QPF within the TX/LA area.

    Mullinax
    $$
    --- SBBSecho 3.28-Linux
    * Origin: Capitol City Online (618:250/10)
  • From Mike Powell@618:250/10 to All on Mon Jun 15 07:30:06 2026
    FOUS30 KWBC 150903
    QPFERD

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

    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 which includes some of the upper
    level remnants of former East Pacific tropical storm Cristina will
    interact 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 into western
    Louisiana by Thursday morning. Immediately in advance of the center
    of this low, heavy rains will continue into the upper Texas Gulf
    coast and the Houston metro 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.

    There remains considerable uncertainty as to how fast the low will
    track up the Texas Gulf Coast towards the lower Mississippi Valley.
    A faster progression may require a northeastward expansion of the
    Slight to cover more of central Louisiana, and if even a bit faster
    still, would re-impact western Mississippi late Wednesday night,
    requiring a significant upgrade from the current blank ERO for that
    area. Thus, significant changes are probable with future updates.

    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.

    ...Midwest...

    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...

    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
    $$
    --- SBBSecho 3.28-Linux
    * Origin: Capitol City Online (618:250/10)
  • From Mike Powell@618:250/10 to All on Tue Jun 16 07:42:48 2026
    FOUS30 KWBC 160821
    QPFERD

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

    Day 3
    Valid 12Z Thu Jun 18 2026 - 12Z Fri Jun 19 2026

    ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
    THE LOWER MISSISSIPPI VALLEY THROUGH CENTRAL ALABAMA...

    ...Lower Mississippi Valley through Central Alabama...

    The tropical low and its associated moisture are expected to start
    the Day 3 period over northern Louisiana or western Mississippi.
    The leading band of heavy rain will be ongoing from eastern
    Louisiana into southern Mississippi. The low will slowly drift
    eastward across Mississippi through the day, then gradually
    increase its forward speed Thursday night as it tracks east across
    Alabama and ends the period in northern Georgia. A very persistent
    heavy band of rain will remain south and east of the low center
    throughout the Day 3 period. This will focus the heaviest rains in
    the Moderate Risk corridor from central Louisiana through central
    Alabama. Prolonged southerly flow of the deep tropical moisture
    with PWATs to 2.5 inches will support development and redevelopment
    of convection ahead of the main band associated with the low. Thus,
    heavy rain with multiple inches of rain per hour rain rates are
    expected through the Moderate Risk area. Soils in Louisiana and
    Mississippi are already saturated now even before Days 1 and 2's
    rains. While some parts of central Alabama have dry soils, that
    should change as the soils are primed today/Day 1. Thus, by Day 3,
    the entire Moderate Risk area should have well wetter than normal
    soils. Thus, hydrology will play a big role in flash flood
    development. For western areas, nearly constant heavy rain in Days
    1-2 will make flooding into D3/Thursday very easy. Further east
    into Alabama, the southerly flow of deep tropical moisture will
    last longer as the low tracks eastward, so there will be a longer
    period where heavy rain may be occurring over Alabama. In
    coordination with BMX/Birmingham, AL forecast office, the Moderate
    Risk was expanded east across central Alabama with this update.
    Even once the low center passes, the air mass will be largely
    unchanged behind the low, as the tropical air mass will still be in
    place into the lower Mississippi Valley, thus, the low's cold front
    could continue to produce storms into southern Alabama into
    Thursday night.

    ...Ohio Valley...

    The northern edge of the deep tropical air mass supporting the
    tropical low to the south will bump up against a strong cold front
    that will be set up along the Ohio River on Thursday. As the
    plentiful moisture on southwesterly flow runs into the front,
    training thunderstorms are expected through much of Kentucky,
    particularly the southern half, Thursday afternoon and evening.
    This could lead to a prolonged period of heavy rain due to training
    and backbuilding thunderstorms over the region. For this reason, an
    internal higher-end Slight was issued for the southern 2/3 of the
    state. The Slight into the mid-Appalachians was trimmed on the
    northern side around Pittsburgh, PA due to less moisture making it
    that far north and east, and with the cold front over Kentucky
    concentrating the storms further west, coverage of storms into West
    Virginia also appears to have diminished in the guidance. Thus, the
    Slight was dropped to a lower-end Slight.

    At the western end of the front into southeastern Oklahoma and
    parts of Arkansas, an MCS may develop late Thursday night as the
    nocturnal jet intensifies. A Slight Risk was drawn in from far
    north Texas along the MO/AR border to the Mississippi/Ohio River
    confluence for expected slow-moving and training storms along much
    of the front, though the highest concentration of storms should be
    into southeastern Oklahoma.

    Wegman


    Day 4 and Day 5

    Valid 12Z Fri Jun 19 2026 - 12Z Sun Jun 21 2026

    ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
    THE SOUTHERN PLAINS, MID SOUTH, AND SOUTHERN APPALACHIANS ON DAY 4...

    ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER THE PARTS OF
    THE MIDWEST ON DAY 5...

    Day 4's (Friday) Excessive Rainfall threat remains fixed across
    much of the South. The combination of the lingering disturbance,
    that may become a more formidable surface cyclone, will reside
    within an environment that contains >2.0" PWs over much of the
    Mid-South. Sufficient instability aloft will continue to support
    thunderstorms that can produce highly efficient rainfall rates.
    Much of the region will also have received a steady dousing of
    heavy rainfall during the work-week as well, priming soils for more
    potential flash flooding. Farther west, a shortwave trough over TX
    and the return of low-level SErly flow will introduce will
    reintroduce more Gulf moisture over central TX and as far west as
    southwest NM. The TX Hill Country is most prone to flash flooding,
    although some localized flash flooding over the Guadalupe and
    Sacramento mountains could also transpire.

    By Day 5 (Saturday), a potent 500mb shortwave trough over the Great
    Basin will race east towards the Northern Rockies around midday and
    reach the northern High Plains by Saturday night. As a cold front
    races south from Canada, a warm front lifting north through the
    Central Plains will deliver a plume of anomalous moisture and
    foster an increasingly unstable environment over the Midwest by
    late Saturday. While the exact placement of the developing
    thunderstorm activity varies by model, they all show a deepening
    surface low over the Central Plains and a strengthening LLJ that
    results in a >500 kg/m/s IVT field over the Midwest. Storms should
    be able to produce efficient rainfall rates thanks to a growing
    shield of >1.5" PWs over the MO River Valley, which does surpass
    the 90th climatological percentile. For these reasons, a Day 5
    Slight Risk was introduced. Farther south, a weakening frontal
    boundary and residual anomalous moisture aloft will help trigger
    additional storms from South TX on east across many of the Gulf
    Coast States. Given the South's increasingly sensitive soils and
    the presence of PWs hovering around 2.0", thunderstorms could
    produce localized flash flooding Saturday afternoon and evening.

    Mullinax
    $$
    --- SBBSecho 3.28-Linux
    * Origin: Capitol City Online (618:250/10)
  • From Mike Powell@618:250/10 to All on Wed Jun 17 10:42:34 2026
    FOUS30 KWBC 170822
    QPFERD

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

    Day 3
    Valid 12Z Fri Jun 19 2026 - 12Z Sat Jun 20 2026

    ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL FOR MUCH OF
    SOUTHERN ALABAMA...

    ...Southeast...

    Any lull in heavy rainfall across southern Alabama from Thursday
    night behind the precipitation shield associated with the remnants
    of Potential Tropical Cyclone 1 will end in a hurry Friday morning
    as the cold front over the Tennessee Valley continues to press
    southward and runs into the ongoing southerly flow and low-level
    jet of deep tropical moisture from off the Gulf. The clash of these
    air masses looks to maximize over southern Alabama, where storms
    are likely to continue in some form or fashion for much of the day
    Friday. Assuming the multiple inches of rain from Thursday occurs
    in these same areas, the slightly lower storm total rain on Friday
    will make little difference for the flooding risk, as multiple
    inches of rain fall over the same areas very hard hit from
    Thursday. This very good overlap in the storm placement from
    Thursday to Friday necessitated a risk upgrade across southern
    Alabama for the Day 3/Friday period. Should this overlap continue
    to hold and the widespread multiple inches of rain with localized
    totals to double digits from Thursday occurs as forecast, it's
    entirely feasible that the hardest hit areas may need further
    upgrades to the flooding risk. Unfortunately the track record with
    the CAMs ensembles on maintaining continuity day to day on where
    the storms will occur is not very good, so any movement breaking
    the overlap will greatly improve the rather ominous flooding
    outlook for southern Alabama on Friday. Convective coverage over
    Alabama should diminish greatly Friday night as heavier rains to
    the west and the departing system to the east should put the state
    in a relative ridging pattern, allowing for a much needed break
    from the rainfall.

    ...Texas Hill Country...

    Southeasterly flow of deep moisture from off the Gulf will
    continue across much of Texas through the Day 3 period.
    Northwestward moving convection on the leading edge of the deep
    moisture will collide with storms that form along the dry line and
    the Mexican mountains Friday evening, resulting in MCS development
    that turns the storms back towards the best instability to the
    southeast. This should result in some areas seeing multiple rounds
    of heavy rain producing storms over the historically flash flood
    prone region of the Texas Hill Country. Thus, a Slight Risk area
    remains in effect for the region. Lesser amounts of rain are
    expected further east into north-central Texas and the Metroplex,
    so the Slight Risk inherited with downgraded in that area.

    Wegman


    Day 4 and Day 5

    Valid 12Z Sat Jun 20 2026 - 12Z Mon Jun 22 2026

    ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
    THE OF CENTRAL PLAINS THROUGH THE MID MISSISSIPPI INTO THE LOWER OHIO VALLEY...

    Day 4...
    A well-defined 500mb shortwave trough will move from the Great
    Basin into the northern Rockies midday Saturday, reaching the
    northern High Plains by Saturday night. Ahead of a southward
    advancing Canadian cold front, a northward-lifting warm front
    across the central Plains will lead an anomalous moisture plume
    into an increasing unstable environment. While exact convective
    placement varies, the deterministic models remain in generally
    good agreement -- depicting a deepening surface low over the
    central Plains that will help to focus moisture along the leading
    edge of a strengthening low level jet. A deepening pool of
    moisture (PWs increasing to 1.5-2 inches) over central
    Nebraska/Kansas eastward into southwestern Iowa and western to
    central Missouri will support efficient rainfall rates. This ample
    moisture along with large- scale ascent afforded by mid-level
    shortwave and right- entrance region jet forcing will further
    encourage heavy rainfall and the potential for flash flooding
    across the region. Therefore, a Slight Risk was maintained across
    the region. Farther south, a weakening frontal boundary and
    residual tropical moisture will trigger additional thunderstorms
    from South Texas across the Gulf Coast. Localized flooding will
    likely remain a threat given the increasing sensitive soils.

    Day 5...
    Forecast confidence lowers notably heading into the latter half of
    the weekend as guidance begins to diverge on the track of the
    leading wave forming over the central Plains on Day 4. Notably, the
    ECMWF offers one of the more northerly solutions compared to other
    guidance. Beyond the primary wave's track from the Midwest into the
    East, considerable model spread exists regarding the timing of the
    trailing front and subsequent wave and storm development. With the
    continuation of ample moisture, instability, and strong forcing
    areas of heavy rainfall and flash flooding appear likely. Given
    the model spread, the outlook area, including a Slight Risk
    extending from the lower Missouri to the lower Ohio Valley, relied
    most heavily on a multi-model ensemble mean.

    Pereira
    $$
    --- SBBSecho 3.28-Linux
    * Origin: Capitol City Online (618:250/10)
  • From Mike Powell@618:250/10 to All on Thu Jun 18 07:39:13 2026
    FOUS30 KWBC 180826
    QPFERD

    Excessive Rainfall Discussion
    NWS Weather Prediction Center College Park MD
    426 AM EDT Thu Jun 18 2026

    Day 3
    Valid 12Z Sat Jun 20 2026 - 12Z Sun Jun 21 2026

    ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF THE
    CENTRAL PLAINS AS WELL AS FOR PORTIONS OF THE SOUTHEAST...

    ...Central Plains...

    A large area of heavy rain associated with a developing MCS
    starting Saturday afternoon and continuing into Saturday night will
    bring multiple inches of rain to a large area of southeastern
    Nebraska through northwestern Missouri. Storms are expected to
    initiate Saturday afternoon with peak heating. An LLJ of
    southeasterly flow will pump deep Gulf moisture up the Plains
    through the day. A developing surface low and upper level shortwave strengthening the low over Colorado will eject into the Plains.
    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 in the form of an MCS. The MCS will track southeast
    into southeastern Nebraska, far northern Kansas, and eventually to
    the Missouri River. Additional storms capable of multiple inch per
    hour rain rates will develop on the southern end of the MCS, where
    the greatest rainfall totals will be. Urban areas in the path
    including Lincoln and maybe Omaha, Nebraska, Topeka, Kansas, and
    eventually St. Joseph and Kansas City, Missouri after midnight will
    likely be impacted. Widely scattered instances of flash flooding
    are likely. Given the amount of moisture present for these storms
    to feed on and the urban areas likely to be impacted, additional
    increases in forecast rainfall may require an upgrade to a Moderate
    Risk with future updates. Since CAMs do poorly and the models
    frequently shift where the heaviest rains will be leading up to an
    event, the Moderate Risk was not considered at this time.

    ...Southeast...

    An MCS tracking from the Ozarks following the same front that
    entered interior portions of the Southeast as a cold front on
    Friday will help that same front now retreat as a warm front on
    Saturday. Heavy rains are expected Saturday morning over the Slight
    Risk area from northern Mississippi to southern Alabama as storms
    track southeastward along the retreating front. Daytime heating
    will likely support additional clusters of storms into the
    afternoon in these areas. The heaviest rains over the most
    widespread area will be Saturday morning in northern Mississippi.
    They will be less organized as they move into southern Alabama
    Saturday afternoon, but given the prior day's expected rains in
    these same areas, the Slight Risk includes southern Alabama as well.

    Wegman


    Day 4 and Day 5

    Valid 12Z Sun Jun 21 2026 - 12Z Tue Jun 23 2026

    ...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF
    THE OZARKS THROUGH THE MIDWEST AND INTO THE UPPER OHIO VALLEY...

    Day 4... By the start of the day 4 forecast period a potent
    shortwave and related surface low are expected to eject eastward
    out of the central Plains into the Midwest. There will also be a
    trailing frontal boundary extending into the southern Plains to add
    a focus for additional thunderstorms. 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 between 30-55% and
    cover much of the SLGT risk area. 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. This is
    especially the case given the sensitivity of the affected regions
    to additional rainfall.

    Day 5... The shortwave and low pressure on day 4 is forecast to
    continue east towards the Mid-Atlantic and Northeast, with
    additional uncertainties in latitude and speed. Additionally,
    thunderstorms should reform along the attached frontal boundary
    extending westward across the Tennessee Valley and into the
    southern Plains. At the moment most convection appears scattered in
    nature and low confidence in placement of heavier QPF. Therefore, a
    MRGL risk is highlighted and will be refined in future updates.
    Additional thunderstorm activity is likely into the High Plains,
    with uncertainty surrounding the impact of a nearby southern Canada
    upper low on thunderstorm activity in the northern High Plains.

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