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  • DAY48SVR: Nws Storm Prediction Center Norman Ok

    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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    --- scorpsmtpd
    * 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)
  • From COD Weather Processor @1:2320/107 to All on Thu Sep 3 07:44:40 2026
    ACUS48 KWNS 030740
    SWOD48
    SPC AC 030738

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0238 AM CDT Thu Sep 03 2026

    Valid 061200Z - 111200Z

    ...DISCUSSION...
    A mid-level trough will persist across the central CONUS through
    early next week, before gradually weakening in favor of more
    amplified, progressive upper troughs. Through the beginning of next
    week, a few impulses ejecting into the northern Plains may be
    accompanied by enough buoyancy and vertical wind shear to support an
    isolated severe threat. However, confidence is too low to delineate
    a more focused severe threat at this time. Likewise, there is a lack
    of consensus among medium-range deterministic and ML/AI guidance
    regarding the track and timing of any particular shortwave upper
    trough later next week, precluding the introduction of any severe
    probabilities this outlook.

    ..Squitieri.. 09/03/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Fri Sep 4 07:50:14 2026
    ACUS48 KWNS 040750
    SWOD48
    SPC AC 040747

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0247 AM CDT Fri Sep 04 2026

    Valid 071200Z - 121200Z

    ...DISCUSSION...
    ...Days 4-6/Mon-Wed -- Northern Plains to Great Lakes...

    An upper shortwave trough is forecast to move across the Canadian
    Prairies and Upper Midwest through Tuesday, before continuing east
    toward the Lower Great Lakes on Wednesday. This will shift the
    amplified upper ridge over the Plains at the beginning of the period
    eastward over the Midwest, before flattening the ridge over the
    Great Lakes through mid-week. As this occurs, enhanced
    west/southwesterly flow will overspread portions of the northern
    Plains/Upper Midwest and eventually the Great Lakes. A surface low
    will track east/northeast across central Canada, and a trailing cold
    front will move across the region on Tuesday/Wednesday. Some severe
    potential could develop across the Dakotas into the Upper Midwest
    Monday and Tuesday given enhance southwesterly flow aloft and
    sufficient moisture ahead of the surface boundary. However, warm
    midlevels may result in capping while large-scale ascent will be
    focused mostly north of the international border. As a result,
    severe potential and storm coverage are uncertain, precluding 15
    percent probabilities at this time.

    The cold front will weaken on Wednesday as the upper low lifts into
    northern Ontario, and deep-layer flow will veer, becoming mostly
    westerly. While some severe potential could develop into parts of
    the Midwest and eastern Great Lakes vicinity, confidence is low
    regarding where the greatest risk could emerge.

    ...Days 7-8/Thu-Fri...

    The upper ridge is forecast to once again amplify over the Rockies
    and into the Plains late in the week and severe potential appears
    limited.

    ..Leitman.. 09/04/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Sat Sep 5 07:55:52 2026
    ACUS48 KWNS 050746
    SWOD48
    SPC AC 050744

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0244 AM CDT Sat Sep 05 2026

    Valid 081200Z - 131200Z

    ...DISCUSSION...
    ...Days 4-6/Tue-Thu -- Central Plains to Great Lakes/Ohio Valley and Mid-Atlantic...

    An upper shortwave trough will shift east across the Upper
    Midwest/Great Lakes and northeast through Thursday. An associated
    surface low will mainly remain over Canada, but a trailing cold
    front will sweep across parts of the central Plains and Upper
    Midwest on Tuesday, before continuing south and east into Kansas and
    across the Great Lakes on Wednesday. By Thursday, the boundary is
    expected to continue south and east across the Ohio Valley and
    Mid-Atlantic. Stronger large-scale ascent will likely remain focused
    near and north of the international border. Furthermore, the
    corridor of deeper boundary layer moisture may be somewhat limited,
    especially Tuesday into Wednesday, due to a prior cold frontal
    passage and surface high pressure over the Midwest. Nevertheless,
    enhanced deep-layer flow, and corridors of at least modest
    instability along the cold front could support some severe risk.
    However, confidence in 15 percent or greater coverage is low at this
    time frame.

    ...Days 7-8/Fri-Sat -- Northern/Central Plains to Upper Midwest...

    At the end of the period, another upper shortwave trough may dig
    southeast from the Pacific Northwest and into the Plains. Another,
    perhaps stronger, cold front could sweep across the Plains and the
    Mid/Upper MS Valley. Depending on moisture return in the wake of the
    earlier cold frontal passage, some severe risk could develop during
    the weekend. Furthermore, large spread exists among various guidance
    regarding the evolution of the this upper trough, resulting in
    uncertainty in greater corridors of severe potential.

    ..Leitman.. 09/05/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Sun Sep 6 07:51:36 2026
    ACUS48 KWNS 060751
    SWOD48
    SPC AC 060749

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0249 AM CDT Sun Sep 06 2026

    Valid 091200Z - 141200Z

    ...DISCUSSION...
    An upper shortwave trough will move from the Great Lakes and over
    the Northeast through Day 5/Thursday. As this occurs, a cold front
    will develop southeast and east across much of the Midwest and
    Northeast. Some strong to severe thunderstorm potential could
    develop near the front, especially on Wednesday across parts of the
    Midwest. However, deep-layer flow will largely remain parallel to
    the boundary and stronger flow aloft will remain displaced to the
    north of better instability.

    Lower amplitude westerly upper-level flow is expected on Day
    6/Friday before another upper trough digs southeast across the
    western U.S. and emerges into the Plains by Day 8/Sunday. Some
    severe potential could return to the Plains during the weekend as
    low-level moisture returns across the region and lee cyclogenesis
    occurs with the approach of the late-period upper trough. Trends
    will be monitored and probabilities may become necessary across
    parts of the central Plains vicinity if confidence in severe
    potential increase.

    ..Leitman.. 09/06/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Mon Sep 7 07:34:00 2026
    ACUS48 KWNS 070733
    SWOD48
    SPC AC 070732

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0232 AM CDT Mon Sep 07 2026

    Valid 101200Z - 151200Z

    ...DISCUSSION...
    An upper shortwave trough will weaken as it spread east across the
    Northeast on Day 4/Thursday. As this occurs, a surface cold front
    will shift east/southeast across the Northeast and the Mid-Atlantic.
    A moist airmass will be in place, but vertical shear will weaken
    through the day and deep-layer flow will remain parallel to the
    surface boundary. Thunderstorms are expected in the vicinity of the
    front, but may tend to be just to the cool side of the boundary.
    Nevertheless, some low-end severe potential could develop from the
    Ohio Valley to the Mid-Atlantic as the front sags southward across
    the region.

    During the weekend into early next week, forecast guidance suggests
    a more progressive upper pattern will emerge across the northern
    tier of the U.S. A series of shortwave upper troughs will move from
    the northern Rockies to the Great Lakes and eventually the Northeast
    during this time. Some severe risk is likely to develop ahead of the
    upper shortwave troughs around the Day 5/Friday to Day 8/Monday time
    period. However, large spread exists in both the timing and
    intensity of these upper trough, resulting in vastly different
    evolution and timing of key surface features (mainly surface low
    position). These differences have large implications for where the
    best corridors of severe potential will ultimately develop, but
    severe probabilities may become necessary in later outlooks for
    portions the northern/central Plains to the Upper Midwest during the
    weekend.

    ..Leitman.. 09/07/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Tue Sep 8 07:26:44 2026
    ACUS48 KWNS 080726
    SWOD48
    SPC AC 080724

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0224 AM CDT Tue Sep 08 2026

    Valid 111200Z - 161200Z

    ...DISCUSSION...
    ...Days 4-5/Fri-Sat -- Plains to the Great Lakes vicinity...

    Severe potential could develop across portions of the Plains into
    the Upper Midwest on Day 4/Friday as boundary layer moisture spreads
    northward ahead of a southeastward-advancing cold front. Moderate to
    strong destabilization ahead of the front, and enhanced vertical
    shear courtesy of a modest upper shortwave trough moving across the
    northern Plains/Upper Midwest vicinity, should be sufficient for
    organized convection mainly from Friday evening into early Saturday.

    Some severe potential could persist into Day 5 Saturday as the
    surface front stalls over the central/southern Plains vicinity but
    continues eastward across the upper Great Lakes region. A moist
    boundary layer will be in place, but stronger flow aloft will become
    increasing displaced to the north of stronger instability,
    precluding 15 percent delineation at this time.

    ...Days 6-8/Sun-Tue...

    An upper trough over the northwestern U.S. will develop eastward
    across the Plains and Great Lakes early next week. Another cold
    front will move across the area, and some severe potential could
    again sweep across the Plains to the Upper Midwest/Great Lakes
    vicinity. Medium range forecast guidance generally maintains
    stronger instability offset from enhanced flow aloft, partly due to
    the early cold frontal passage in the Day 4-5/Friday-Saturday time
    frame and strong surface high pressure over the Great Lakes in the
    wake of that frontal passage. Trends will be monitored and
    probabilities could become necessary in later outlooks.

    ..Leitman.. 09/08/2026

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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 9 07:29:22 2026
    ACUS48 KWNS 090729
    SWOD48
    SPC AC 090727

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0227 AM CDT Wed Sep 09 2026

    Valid 121200Z - 171200Z

    ...DISCUSSION...
    ...Day 4/Sat - Central Plains...

    A cold front will stall across the central Plains on Saturday.
    Low-level east/southeasterly flow will maintain rich boundary layer
    moisture across KS and into eastern CO. Early day convection may be
    ongoing in the vicinity of the stalled boundary within the low-level
    warm advection regime. It is uncertain if airmass recovery and
    renewed thunderstorm development will occur within the unstable warm
    sector given nebulous large-scale ascent and modest vertical shear.
    While low severe potential may eventually evolve, probability
    appears less than 15 percent at this time.

    ...Days 5-6/Sun-Mon -- Central Plains to the Great Lakes...

    An upper trough is forecast to move from the northern Rockies to the
    Great Lakes through early Day 7/Tuesday. This will bring enhanced
    southwesterly flow to portions of the northern/central Plains into
    the Great Lakes, particularly on Monday. With the approach of the
    trough, lee low development is forecast across the northern/central
    High Plains on Sunday. Increasing southerly low-level flow will
    transport moisture northward to NE/SD ahead of a
    southeastward-advancing cold front. This could support some severe
    risk across parts of the northern/central Plains and Mid-MO Valley
    vicinity on Sunday. However, large spread exists among forecast
    guidance with regards to the surface low placement, northward extent
    of moisture return, and frontal position. As a result, corridors of
    greater severe potential are uncertain on Sunday.

    As the upper trough continues to lift east/northeast through the
    Great Lakes on Monday, severe potential could develop eastward into
    parts of the Mid/Upper MS Valley and upper Great Lakes vicinity.
    Stronger deep-layer flow may become displaced to the north of better instability, and similarly large model spread continues into this
    time frame. Depending on trends, severe probabilities could
    eventually be needed for Sunday and/or Monday.

    ...Days 7-8/Tue-Wed...

    Lower amplitude, quasi-zonal flow is expected to develop by the end
    of the forecast period as the early-week uppers shortwave trough
    lifts into eastern Canada and the sub-tropical high begins to
    rebuild over the southern U.S. This should largely limit severe
    potential, though abundant moisture will reside from the southern
    Plains into the Southeast and Mid-Atlantic and daily sporadic strong
    storms could still occur.

    ..Leitman.. 09/09/2026

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    --- scorpsmtpd
    * Origin: capitolcityonline.net * KY, USA (1:2320/107)
  • From COD Weather Processor @1:2320/107 to All on Thu Sep 10 07:46:52 2026
    ACUS48 KWNS 100746
    SWOD48
    SPC AC 100744

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0244 AM CDT Thu Sep 10 2026

    Valid 131200Z - 181200Z

    ...DISCUSSION...
    ...Days 4-5/Sun-Mon -- Central Plains to the Mid-MS Valley...

    A progressive upper pattern is expected early in the week. An
    initial upper trough over the Great Lakes will spread east as upper
    ridging builds across the Plains. Meanwhile, another upper trough
    over the Northwest will shift east, moving across the northern
    Plains and Upper Midwest on Monday, breaking down the upper ridge.
    Surface high pressure over the Great Lakes on Sunday will suppress
    low-level moisture southward across the central/southern Plains and
    the Mid-MS/Lower OH Valleys. A very moist airmass will be in place
    to the south of a stalled frontal boundary across the region.
    Widespread showers and thunderstorms will be possible near the
    surface boundary within low-level warm advection over the Middle to
    Lower MO Valley. Vertical shear will be weak, but strong instability
    could some strong gust potential, though convection may stay mainly
    to the cool side of the surface boundary. Overall, severe potential
    appears less than 15 percent on Sunday.

    Severe potential will likely increase on Monday as the upper ridge
    breaks down and stronger southwesterly flow overspread the
    northern/central Plains to the Mid/Upper MS Valleys. Rich boundary
    layer moisture will be in place ahead of a southeastward-advancing
    cold front. Convection may be ongoing from the northern Plains into
    IA/IL Monday morning. This results in some uncertainty in position
    of best severe potential. Currently, the best overlap of rich
    boundary layer moisture, strong instability and favorable shear near
    the advancing cold front appears to be from eastern NE into IA and
    vicinity. A 40+ kt southwesterly low-level jet is expected to
    develop during the nighttime hours across KS/NE into IA, oriented
    along the surface front, supporting an organized line of storms
    tracking southeast ahead of the front, and promoting damaging wind
    potential. Overall, the pattern appears favorable for at least
    isolated severe storms on Monday, and a 15 percent delineation has
    been included.

    ...Days 6-8/Tue-Thu...

    The early week surface front will stall from the southern Plains to Mid-MS/Lower OH Valley through mid-week. A very moist airmass will
    persist south of the boundary, and persistent low-level warm
    advection could favor bouts of heavy rain. While some low-level
    severe potential could develop where pockets of strong
    destabilization occurs, weak vertical shear should largely limit
    more widespread potential, precluding probabilities.

    ..Leitman.. 09/10/2026

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