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  • DAY48SVR: Nws Storm Prediction Center Norman Ok

    From COD Weather Processor @1:2320/107 to All on Thu Aug 20 08:31:18 2026
    ACUS48 KWNS 200830
    SWOD48
    SPC AC 200829

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0329 AM CDT Thu Aug 20 2026

    Valid 231200Z - 281200Z

    ...DISCUSSION...
    An upper trough will move slowly across the Northeast Sun/D4 into
    Mon/D5, with thunderstorms likely ahead of a cold front. This front
    will likely push offshore on Mon/D5 as a surface low ejects
    northward across Quebec. A moist air mass will remain ahead of the
    front across the Mid Atlantic and into New England, though ongoing
    rain and thunderstorms reduce predictability as far as how unstable
    it will become on Sun/D4. Also mitigating overall severe risk
    appears to be relatively modest low-level wind speeds, with 10-20 kt
    at 850 mb. These areas will be monitored for possible low severe
    probabilities in the coming days.

    To the west, low severe probabilities are possible over parts of the
    northern High Plains, as a small but progressive shortwave trough
    moves out of the Northwest and across the northern Rockies atop the
    upper ridge. West to northwest winds across the northern High Plains
    combined with a lee trough and ribbon of 2000 J/kg MUCAPE should
    support at least isolated hail/wind activity, perhaps from eastern
    MT into the Dakotas.

    Additional storm potential, generally low-end, will be possible
    Tue/D6 into Wed/D7 over much of the Midwest to Great Lakes, though predictability is quite low in forecasting the track of the northern
    wave, which may begin phasing with a developing upper low over
    Ontario.

    ..Jewell.. 08/20/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Fri Aug 21 08:56:24 2026
    ACUS48 KWNS 210856
    SWOD48
    SPC AC 210854

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0354 AM CDT Fri Aug 21 2026

    Valid 241200Z - 291200Z

    ...DISCUSSION...
    A mid-level trough will move across the Northeast on Monday and the
    surface front will be mostly offshore, reducing the severe weather
    threat. As this trough departs, ridging will build across the
    Rockies. This will eventually set up a pattern featuring individual
    mid-level shortwave troughs within northwesterly flow from the
    northern Plains to the Midwest. Some severe weather will likely
    occur with mid-level shortwave troughs within this flow, but these
    details likely will not become more clear until the short term.

    Model consensus indicates a stronger mid-level shortwave trough
    traversing the Pacific Northwest on D7/Thursday. This pattern would
    be favorable for some severe weather threat across Montana, but at
    this time, it appears moisture will stay farther east. Therefore, no
    severe weather is anticipated.

    ..Bentley.. 08/21/2026

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    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Sat Aug 22 07:44:26 2026
    ACUS48 KWNS 220744
    SWOD48
    SPC AC 220742

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0242 AM CDT Sat Aug 22 2026

    Valid 251200Z - 301200Z

    ...DISCUSSION...
    Overall, the long range pattern will feature a ridge centered over
    the southern High Plains which may shift slightly west through the
    period. Some severe weather may occur within the northwesterly flow
    pattern from the northern Plains to the Ohio Valley Tuesday/D4 to
    Thursday/D6, but confidence is not high enough for probabilities at
    this time. There is an emerging signal for a seasonably strong high
    pressure to build into the eastern CONUS and shunt most of the
    richer low-level moisture to the Gulf Coast states. If this occurs,
    a relative lull in severe weather potential would exist from the
    Mid-Atlantic and Northeast to the Upper Midwest into next weekend.

    ..Bentley.. 08/22/2026

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    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Sun Aug 23 08:41:00 2026
    ACUS48 KWNS 230840
    SWOD48
    SPC AC 230838

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0338 AM CDT Sun Aug 23 2026

    Valid 261200Z - 311200Z

    ...DISCUSSION...
    ...D4/Wednesday to D6/Friday...
    A mid-level trough will amplify across the Great Lakes region while
    the mid-level ridge maintains its amplitude across the Rockies.
    Within this pattern, some severe weather potential may exist as a
    cold front moves from the Great Lakes to the Northeast. However, the
    signal is not that strong and thus, it is unclear if more than an
    isolated threat will exist; but the evolution of this front and the
    instability associated with it will be monitored.

    ...D7/Saturday to D8/Sunday...
    There is still a fair amount of uncertainty with the evolution of
    the pattern by next weekend, but a general trend toward flattening
    of the upper-level ridge is apparent in the deterministic, AI, and
    ensemble guidance next weekend. This includes moderate flow within
    the zonal region across the central/northern Plains and into the
    Upper Midwest. This period will need to be watched closely as strong instability and moderate shear appear to overlap across a relatively
    broad region, which should support diurnal thunderstorm activity
    given the flattening of the ridge. The specific timing/location of
    these threats will depend on evolution of the pattern and the
    embedded shortwave troughs within the flow. However, it is worth
    noting that the EC-AIFS and the AIGFS both have a signal for a more consolidated mid-level shortwave trough moving across the northern
    Plains on Sunday/D8, which has also been consistently shown by the
    EC-AIFS for the past 4 runs. If this trend continues, there may be opportunities for probabilities to be added in later outlooks.

    ..Bentley.. 08/23/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Mon Aug 24 09:01:06 2026
    ACUS48 KWNS 240900
    SWOD48
    SPC AC 240859

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0359 AM CDT Mon Aug 24 2026

    Valid 271200Z - 011200Z

    ...DISCUSSION...
    A strong mid-level ridge will be centered over the Rockies on
    Thursday with a broad trough centered across the Great Lakes. The
    ridge will break down over the weekend with a more zonal flow with
    embedded shortwave troughs extending from the Northwest to the
    northern Plains and into the Northeast. Beyond this weekend,
    guidance differs on the evolution of the pattern with considerable
    uncertainty.

    ...D7/Sunday to D8/Monday - Northern Plains...
    Guidance continues to consolidate around an unseasonably strong
    mid-level shortwave trough across the northern Plains into the Upper
    Midwest on Sunday and Monday. There is still some spread around the
    timing of this trough and also the degree of destabilization ahead
    of it. However, despite these timing differences, a moderately
    strong signal for an increasing severe weather threat in this period
    appears to be emerging as a trough with a consistent convective
    signal is shown by the ECMWF and GFS and also by the AI-GFS and
    AI-ECMWF. Ensemble guidance shows a flattened ridge with a mid-level
    jet streak across this region during the same timeframe.
    Surprisingly, AI/ML guidance shows very little signal for a severe
    threat across this region. Analysis of individual ensemble members
    suggests this is likely reflective of the uncertainty in timing and
    location of this trough and greater spread among the ensemble
    guidance. Nonetheless, the potential for an organized severe weather
    threat across the northern Plains and/or Upper Midwest late this
    weekend into early next week appears to be increasing. If guidance
    continues to consolidate with decreasing spread about the timing of
    the trough, severe weather probabilities may eventually be needed.

    ..Bentley.. 08/24/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Tue Aug 25 08:30:18 2026
    ACUS48 KWNS 250829
    SWOD48
    SPC AC 250827

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0327 AM CDT Tue Aug 25 2026

    Valid 281200Z - 021200Z

    ...DISCUSSION...
    Severe weather is possible across the northern Plains into the Upper
    Midwest starting Day 4/Friday and continuing through the weekend.
    The specific evolution remains unclear with quite a range of
    ensemble solutions at this time. Nonetheless, expect severe weather
    somewhere within this broad region each day.

    ...Day4/Friday...
    As the upper-level ridge flattens on Friday, lee troughing will
    develop across the northern High Plains. Moderate to strong
    instability is forecast to develop across the western Dakotas ahead
    of this lee trough. Any weak mid-level shortwave trough to provide a
    focus for this threat remains nebulous. Therefore, the location of
    any surface features remains unclear and thus, it is difficult to
    highlight a more specific region with a greater severe weather
    probability at this time.

    ...Day5/Saturday...
    Severe weather may be possible across portions of the Upper Midwest
    on Saturday, but this threat will be somewhat dependent on the
    location and intensity of Day 4 convection.

    ...Day6/Sunday...
    The ECMWF and AI-ECMWF remain relatively consistent showing a trough
    traversing the northwest on Saturday and emerging across the
    northern Plains on Sunday. Meanwhile, the GFS and AI-GFS have
    trended more progressive, and the individual GEFS members show
    substantial spread in the upper-level pattern for Sunday/Day6. The
    relative consistency in timing and location of the upper-level
    trough from the ECMWF build confidence for this solution. However,
    even the ECMWF and AI-ECMWF trended slightly less amplified with
    this trough. Therefore, the combination of large spread in the upper
    pattern from GEFS members and a slightly deamplified trend from the
    ECMWF provide enough uncertainty to avoid adding probabilities at
    this time.

    ..Bentley.. 08/25/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Wed Aug 26 08:44:10 2026
    ACUS48 KWNS 260843
    SWOD48
    SPC AC 260842

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0342 AM CDT Wed Aug 26 2026

    Valid 291200Z - 031200Z

    ...DISCUSSION...
    ...D4/Saturday - Northern Plains to Upper Midwest...
    A mid-level ridge will move slowly east across the Plains with
    slight suppression through the day. A lee trough will consolidate
    into a surface low across the northern Plains through the day
    Saturday. Ahead of this surface low, strong instability is forecast
    across South Dakota and vicinity. Despite the favorable environment
    across this region, primary forcing will be focused on the nose of
    the low-level jet across Iowa and into Wisconsin, well east of the
    greatest instability and near the Canadian border. Therefore,
    limited storm coverage precludes severe weather probabilities at
    this time, but given the favorable environment, it will need to be
    monitored closely.

    ...D5/Sunday - North Dakota and Vicinity...
    A mid-level shortwave trough will move from the Pacific Northwest to
    the northern Plains Saturday/D4 and Sunday/D5. 00Z guidance has come
    into fairly consistent agreement with the location and amplitude of
    this trough across eastern Montana at 00Z Sunday evening. However,
    there is considerable disagreement with the degree of
    destabilization across North Dakota, where forcing will be greatest.
    The GFS dry bias across most of the Plains has severely lessened the instability. However, despite this challenge, it is apparent that
    most of the instability significantly southeast of the upper-level
    forcing. The GFS-Para seems to have a more realistic handle on
    low-level moisture/instability magnitude but it also shows a
    significant disconnect between where this instability is located and
    the deeper forcing.

    The deterministic ECMWF forecast shows a potentially significant
    severe weather event across North Dakota with strong instability and
    shear ahead of a robust convective QPF signal. This is supported by
    the AI-ECMWF which shows a similar evolution. However, the
    EC-ensemble mean of instability shows at least some trend toward the
    GEFS with primary instability southeast of the best forcing.

    It is also worth noting that the wave is forecast to eject across
    North Dakota relatively late (~06Z) which may be a somewhat limiting
    factor to a greater threat. This potential timing disconnect,
    combined with some hint of limited overlap between the greatest
    instability and the primary upper forcing, cast enough uncertainty
    to preclude severe weather probabilities at this time. However, it
    is worth noting that if a solution similar to the ECMWF
    materializes, a significant severe weather event is possible.

    ...D6 and Beyond...
    By early next week, the primary mid-level ridge appears to center
    around the southern Appalachians with broad southwesterly flow from
    the Southwest to the Great Lakes. Within this area of southwesterly
    flow, multiple embedded mid-level shortwave troughs are forecast. Predictability of these smaller scale features is relatively low at
    this range, but some continued severe weather threat will likely
    persist around the periphery of the ridge from the Plains to the
    Great Lakes and potentially into the Northeast.

    ..Bentley.. 08/26/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Thu Aug 27 08:00:42 2026
    ACUS48 KWNS 270800
    SWOD48
    SPC AC 270758

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0258 AM CDT Thu Aug 27 2026

    Valid 301200Z - 041200Z

    ...DISCUSSION...
    ...D4/Sunday - Northern Plains...
    Some severe weather is possible across the northern Plains on
    Sunday, but details remain unclear. The primary mid-level shortwave
    trough and associated large-scale ascent is expected to traverse
    northern Montana and North Dakota. However, the greater instability
    is focused farther southeast across eastern South Dakota and
    southwest Montana. The ECMWF shows enough instability developing
    farther north into south-central North Dakota to support some severe
    weather threat. The uncertainties regarding destabilization and
    storm coverage preclude severe weather probabilities at this time.

    ...D5 and Beyond...
    The forecast next week features multiple mid-level shortwave troughs
    and considerable uncertainty with the timing of these features.
    However, there is a larger scale trend toward a ridge building
    across the Plains with northwesterly flow from the Upper Midwest to
    the Mid-Atlantic/New England. Moderate to strong instability along
    this corridor will support some severe weather potential next week.
    However, specific areas of greater severe weather potential will
    depend on the timing and amplitude of embedded mid-level shortwave
    troughs. Therefore, no probabilities can be added at this time.

    ..Bentley.. 08/27/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Fri Aug 28 08:51:48 2026
    ACUS48 KWNS 280851
    SWOD48
    SPC AC 280849

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0349 AM CDT Fri Aug 28 2026

    Valid 311200Z - 051200Z

    ...DISCUSSION...
    An upper ridge will meander eastward across the central and eastern
    CONUS through the week, with multiple mid-level shortwave troughs
    and other smaller embedded impulses poised to pivot around the ridge
    and traverse the northern Plains to the Mid-Atlantic. Several days
    of at least scattered strong to severe thunderstorms are expected
    along the periphery of the upper ridge as appreciably strong
    mid-level flow overspreads a seasonably moist boundary layer,
    especially during the middle of the week. By the end of the week,
    appreciable instability builds back into the northern Plains and
    upper MS Valley, but predictability is too low to ascertain any
    localized severe potential this far in advance.

    ...OH Valley to the Mid-Atlantic and southern New England...
    The strongest signal for severe thunderstorms currently exists for
    Days 5-6 (Tuesday-Wednesday). Guidance differs on the details
    regarding placement and timing of mid-level troughs/impulses on Day
    5 (Tuesday), though severe thunderstorms will probably develop
    somewhere between the eastern Great Lakes to the Eastern Seaboard.
    Once details become clearer on where storm development is most
    likely, 15 percent severe probabilities will likely be introduced.

    For Day 6 (Wednesday), there is a general consensus among
    medium-range guidance that at least one impulse will traverse the
    eastern Great Lakes to the Mid-Atlantic/southern New England
    corridor. A 50+ kt mid-level northwesterly 500 mb jet will
    overspread mid 60s F surface dewpoints, yielding both 1500+ J/kg
    MLCAPE and 40-50 kts of effective bulk shear amid a convective
    signal. As such, a 15 percent severe area has been introduced for
    Wednesday where these aforementioned ingredients best overlap.

    ..Squitieri.. 08/28/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Sat Aug 29 08:57:46 2026
    ACUS48 KWNS 290857
    SWOD48
    SPC AC 290855

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0355 AM CDT Sat Aug 29 2026

    Valid 011200Z - 061200Z

    ...DISCUSSION...
    Medium range guidance consensus depicts a persistent ridge fortified
    across the central CONUS through the Days 4-8 (Tuesday-Saturday)
    period. Multiple mid-level shortwave troughs and smaller scale
    impulses will pivot around the broader upper ridge and traverse the
    Pacific Northwest to northern Plains, Great Lakes, and Northeast
    through the week. The best chance for rounds of organized strong to
    severe thunderstorms will be with impulses overspreading a moist
    boundary layer from the Upper MS Valley to the southern New England/Mid-Atlantic regions. Details regarding the timing and
    placement of some of these impulses varies among medium-range
    guidance, rendering predictability too low for several potential
    severe scenarios.

    ...Days 4-7 (Tuesday-Friday) - Northeast/Mid-Atlantic...
    The Northeast to Mid-Atlantic will experience the east-northeast
    periphery of the aforementioned upper ridge, with multiple impulses
    expected to overspread the region through the middle of the week. At
    least isolated to scattered severe thunderstorms are expected each
    day Tuesday-Friday. At the moment, medium range guidance consensus
    shows the strongest signal in a mid-level impulse impinging on
    southern New England and the Mid-Atlantic on Day 5/Wednesday, where
    severe probabilities have been maintained.

    Guidance also depicts these same regions to have adequate vertical
    wind shear and instability Tuesday and Thursday, perhaps even
    extending into Day 7/Friday. Like Wednesday, several members of
    medium range ML/AI generated guidance also has severe probabilities
    over these regions Days 4-7. Unlike Wednesday though, deterministic
    medium range guidance varies in place and time of the more subtle
    impulses expected to support severe weather over the Northeast. It
    is acknowledged that severe probabilities will likely be needed in
    the future. However, probabilities have been withheld outside of
    Wednesday out of prudence given the degree of changes in forecast
    details expected in the coming days.

    ..Squitieri.. 08/29/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Sun Aug 30 08:39:22 2026
    ACUS48 KWNS 300839
    SWOD48
    SPC AC 300837

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0337 AM CDT Sun Aug 30 2026

    Valid 021200Z - 071200Z

    ...DISCUSSION...
    An upper ridge will remain centered over the TN Valley/central
    Appalachians through the end of the week before retrograding
    westward toward the Plains by next weekend. Multiple mid-level
    impulses and shortwave troughs will traverse the upper ridge this
    week before upper troughing dominates the Interior West toward the
    end of the extended forecast period. The best chances for severe
    thunderstorms will be with the aforementioned impulses traversing
    the ridge over the Great Lakes to the East Coast, particularly
    during the middle of the week.

    ...Days 4-6 (Wednesday-Friday) - Northeast to Mid-Atlantic...
    Severe probabilities have been maintained for portions of the lower
    Hudson Valley into the Mid-Atlantic Day 4/Wednesday, as guidance
    consensus continues to show a well-timed shortwave trough
    overspreading this region. Medium-range guidance continues to show a
    convective precipitation signal accompanying this impulse along with appreciable buoyancy and vertical wind shear. It should be noted
    that convective overturning from Day 3 (Tuesday) storms may
    stabilize part of this area, with the specific location of storms
    becoming dependent on residual baroclinic boundaries. As such, the
    exact placement of Wednesday's severe probabilities may need to be
    adjusted accordingly.

    Likewise, for Day 5/Thursday, another mid-level impulse will
    traverse the northeast extent of the upper ridge and overspread the Mid-Atlantic. Given adequate buoyancy and shear likely remaining in
    place, 15 percent severe probabilities have been introduced. As with
    the previous day, these probabilities may need some adjustment in
    future outlooks based on where airmass modification along baroclinic
    zones occurs.

    Medium-range guidance continues to show a pronounced mid-level
    impulse, accompanied by adequate deep-layer shear and buoyancy,
    impinging on the Mid-Atlantic on Day 6/Friday, which would support
    at least an isolated severe threat. ML/AI guidance also suggests
    that the Friday severe threat would encompass the ending stages of a
    potential multi-day severe episode. Given the multiple preceding
    days of storms and constant shift in favorable corridors modulated
    by baroclinic zones, confidence is very low for realistically
    pinpointing a focused severe area. However, it appears the Delmarva
    may be the most likely area for seeing organized storm activity.

    ..Squitieri.. 08/30/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Mon Aug 31 08:48:32 2026
    ACUS48 KWNS 310848
    SWOD48
    SPC AC 310846

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0346 AM CDT Mon Aug 31 2026

    Valid 031200Z - 081200Z

    ...DISCUSSION...
    An upper ridge will persist across the TN Valley this week before
    retrograding to the Plains states and further amplifying into early
    next week. As this occurs, upper troughing will also amplify along
    the East Coast and Interior West. The best chances for severe storms
    will be closer to the East Coast Days 4-5 (Thursday-Friday) as a
    series of mid-level impulses will crest the Ridge and traverse the
    Mid Atlantic, where instability will be present.

    ...Days 4-6 (Thursday-Saturday) - Mid-Atlantic Region...
    The amplification of the broader upper trough along the East Coast
    will result in a farther southward shift of accompanying mid-level
    impulses, which will promote deep-layer ascent over the Mid-Atlantic
    region. The severe threat may also be modulated farther south given
    established baroclinic zones from prior rounds of storms. On
    Thursday, storms should develop along a differential heating zone
    somewhere around Delmarva or points immediately west. Surface
    dewpoints in the upper 60s to near 70 F beneath seasonably cool
    temperatures aloft will yield 1500-3000 J/kg MLCAPE. Given over 30
    kts of effective bulk shear expected, multicells, supercells, and
    short bowing segments will likely develop, accompanied by a severe
    wind/hail threat.

    For Day 5 (Friday), the upper trough will amplify further, allowing
    for a surface differential heating zone to become established across
    the southern Mid-Atlantic, where adequate moisture and instability
    will likely coincide with modest vertical wind shear, supporting
    another day of severe potential. Damaging gusts will likely be the
    main threat.

    Some lingering severe potential may exist across the Carolinas on
    Day 6/Saturday before the upper trough departs the region, as
    indicated by some ML/AI guidance. However, predictability on the
    timing of details (i.e. baroclinic boundaries and overlapping
    corridors of vertical wind shear) is too low for the introduction of probabilities this outlook.

    ...Day 4 (Thursday) - Upper Midwest...
    Some guidance depicts the potential for severe thunderstorms along
    an effective warm front across portions of the Upper Midwest, where
    rich low-level moisture will reside ahead of a surface trough. Given
    stronger mid-level flow and cooler temperatures overspreading the
    warm front, enough shear and instability may manifest to support a
    severe threat. While calibrated guidance has been ramping up severe probabilities over this area, synoptic features (such as a
    pronounced mid-level impulse) do not appear strongly evident in
    deterministic guidance, precluding the addition of severe
    probabilities to this outlook.

    ..Squitieri.. 08/31/2026

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    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Tue Sep 1 09:59:18 2026
    ACUS48 KWNS 010830
    SWOD48
    SPC AC 010828

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0328 AM CDT Tue Sep 01 2026

    Valid 041200Z - 091200Z

    ...DISCUSSION...
    An upper ridge will meander from the Mid-MS and TN Valleys toward
    the Plains through the extended period, with upper troughs poised to
    amplify along the East Coast and over the Interior West. Multiple
    mid-level impulses will traverse this flow pattern, translating from
    the Pacific Northwest to the northern Plains and Upper MS Valley,
    then the Mid-Atlantic. It is in this elongated, roughly zonal
    corridor that thunderstorm potential will be highest.

    The severe threat with the relatively highest degree of
    predictability will be across the Mid-Atlantic Days 4-5 (Friday and
    Saturday). On Friday, a diffuse differential heating boundary,
    generated by thunderstorm clusters from previous days, will likely
    become established somewhere across the southern Mid-Atlantic. As an
    upper trough amplifies over this differential heating boundary,
    thunderstorms should develop amid rich low-level moisture beneath
    stronger flow aloft. The more organized storms may produce damaging
    wind gusts (hence the maintenance of 15 percent severe
    probabilities). Calibrated ML/AI guidance suggests that the severe
    threat may persist into Saturday across the Carolina Piedmont.
    However, deterministic guidance shows the upper trough advancing
    further into the Atlantic this weekend, along with upper support. As
    such, storm coverage and initiation mechanisms for Saturday remain
    too unclear this far in advance for the introduction of severe
    probabilities at this time.

    Amplification of the Interior West upper trough will support surface
    lee troughing and accompanying low-level moisture advection across
    the Plains states. While at least isolated severe thunderstorms may
    occur any where from the northern/central High Plains toward the
    Upper MS Valley, predictability of any severe potential is too low
    this far out.

    ..Squitieri.. 09/01/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Wed Sep 2 08:46:20 2026
    ACUS48 KWNS 020846
    SWOD48
    SPC AC 020844

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0344 AM CDT Wed Sep 02 2026

    Valid 051200Z - 101200Z

    ...DISCUSSION...
    Upper ridging will prevail over much of the central and eastern
    CONUS into the middle of next week. The upper trough meandering over
    the Interior West will eventually eject into the northern Plains and
    pivot around the upper ridge while another upper trough (currently
    along the East Coast) slowly drifts out to sea. As this occurs,
    surface high pressure and cooler air will overspread the
    northeastern quadrant of the U.S.

    In the extended period, the best chance for some severe storms will
    be in and around the Carolinas on Day 4/Saturday. A diffuse
    differential heating zone will continue to drift south while being
    reinforced from storms on previous days. By Saturday afternoon,
    heating along this boundary, amid a very moist environment, will
    promote damaging gust potential, hence the introduction of 15
    percent severe probabilities.

    There is also some hint at an MCS propagating southward across
    eastern ND into northern and central MN along a moist and unstable
    surface warm front on Saturday as well. While ML/AI calibrated
    guidance consensus is beginning to elevate severe probabilities in
    this area, upper support for this feature is quite weak at best,
    limiting confidence for the introduction of severe probabilities
    this outlook.

    Lastly, the ejection of an upper trough into the northern Plains
    early next week (i.e. next Monday or Tuesday) will support surface
    lee troughing and the northward advection of rich low-level moisture
    beneath cooler temperatures and stronger flow aloft. At least an
    isolated severe thunderstorm risk may materialize from this
    scenario, but details on timing and placement of key features are
    too nebulous for the confident introduction of severe probabilities
    this outlook.

    ..Squitieri.. 09/02/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)