• DAY48SVR: Nws Storm Prediction Center Norman Ok

    From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Thu Jun 19 08:47:12 2025
    ACUS48 KWNS 190847
    SWOD48
    SPC AC 190845

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0345 AM CDT Thu Jun 19 2025

    Valid 221200Z - 271200Z

    ...DISCUSSION...
    ...D4/Sunday...
    The upper-level trough over the West is forecast to take on more of
    a positive tilt on Sunday, as an embedded shortwave and attendant
    midlevel jet maximum move across the northern Rockies/High Plains.
    As this occurs, a surface low is forecast to move from SD toward the
    upper Great Lakes, as a trailing cold front moves through the
    northern/central Plains. Guidance varies regarding frontal timing,
    though generally agrees that stronger mid/upper-level flow will tend
    to lag behind the front.

    While details remain uncertain, strong to potentially severe storms
    may develop near/north of the surface low across parts of the
    Dakotas/MN, and also along the trailing cold front into the central
    Plains.

    ...D5/Monday - D8/Thursday...
    The upper ridge across the Southeast is expected to remain in place
    through at least early next week, with some guidance suggesting
    potential for deamplification by the middle of the week. Multiple
    shortwaves may emerge from the persistent (though weakening) western
    trough through at least Wednesday, resulting in some potential for
    strong to severe storms along the periphery of the upper ridge from
    the Plains into the upper Midwest and Great Lakes, and possibly
    parts of the Northeast. However, predictability remains quite low
    regarding the details of any organized severe threats during this
    time frame.

    ..Dean.. 06/19/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Fri Jun 20 08:45:49 2025
    ACUS48 KWNS 200844
    SWOD48
    SPC AC 200842

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0342 AM CDT Fri Jun 20 2025

    Valid 231200Z - 281200Z

    ...DISCUSSION...
    ...D4/Monday...
    A mid/upper-level shortwave trough initially over the northern
    Plains and upper Midwest is forecast to move into Ontario on Monday,
    along the northern periphery of an amplified upper ridge over the
    eastern CONUS. A cold front will move through parts of the Great
    Lakes, Upper Midwest and central Plains. The strongest deep-layer
    flow may tend to lag behind the front, but moderate to strong
    instability could support strong to potentially severe storms along
    the front during the afternoon and evening.

    Farther east, strong instability is generally forecast to develop
    across parts of the Mid Atlantic into New England. However, due to
    the influence of the upper ridge, there is currently little signal
    for diurnal storm development across this region on Monday.

    ...D5/Tuesday...
    Extended-range guidance is in reasonably good agreement that a cold
    front will move southward across the lower Great Lakes into New
    England on Tuesday. Favorable low-level moisture and strong
    instability could support severe-storm potential along the front
    during the afternoon and evening. However, coverage of storms is
    currently uncertain, due to the lingering influence of the upper
    ridge, and a tendency for stronger large-scale ascent to be
    displaced well north of the front.

    The western upper trough is forecast to deamplify on Tuesday, with
    most guidance suggesting that mid/upper-level flow will tend to
    weaken downstream across the Great Plains and upper Midwest.
    However, strong to locally severe storms could again be possible
    near the front, which may begin to move northward across the central
    Plains as a warm front through the day.

    ...D6/Wednesday - D8/Friday...
    Predictability begins to wane by the middle of next week regarding
    the evolution of synoptic features across the CONUS, though the same
    general pattern of a weak upper trough in the West and an upper
    ridge over the East may continue through at least Wednesday. In the
    absence of any apparent strong forcing mechanisms, organized severe
    potential (if any) may tend be focused near a convectively
    influenced front across parts of the Plains into the Midwest and
    Great Lakes.

    ..Dean.. 06/20/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Jun 21 08:43:59 2025
    ACUS48 KWNS 210843
    SWOD48
    SPC AC 210842

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0342 AM CDT Sat Jun 21 2025

    Valid 241200Z - 291200Z

    ...DISCUSSION...
    ...D4/Tuesday...
    Aside from some modest deamplification, little change to the
    large-scale pattern is expected on Tuesday. An upper trough will
    remain over the western CONUS, while an upper ridge persists over
    the East.

    Scattered to numerous thunderstorms will again be possible along the
    western and northern periphery of the upper ridge, from the
    central/southern High Plains into the Upper Midwest. Deep-layer flow
    will generally be modest, but some severe threat could evolve in the
    vicinity of an outflow-influenced front, in the presence of
    favorable low-level moisture and moderate to strong buoyancy.

    Farther east, a cold front is forecast to move southward across
    parts of northern New England. Guidance varies regarding the extent
    to which stronger deep-layer flow and large-scale ascent lag behind
    the front, but moderate to strong buoyancy could support at least an
    isolated severe threat during the afternoon and evening.

    ...D5/Wednesday...
    Continued modest weakening of both the western trough and eastern
    ridge is generally forecast on Wednesday. Scattered to numerous
    thunderstorms will again be possible from the High Plains into the
    Midwest, Great Lakes, and Northeast, along the periphery of the
    ridge. Deep-layer flow is expected to be relatively weak across most
    areas, but mesoscale corridors of somewhat greater severe threat
    could evolve within this pattern.

    ...D6/Thursday - D8/Saturday...
    Predictability of the large-scale pattern begins to notably decrease
    by the end of next week. In general, an upper ridge may persist over
    the Southeast, while one or more mid/upper-level shortwave troughs
    move across the northern CONUS. This pattern may eventually yield an
    increasing threat for organized severe storms across the northern Rockies/Plains and Upper Midwest, but details are very uncertain at
    this forecast range.

    ..Dean.. 06/21/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sun Jun 22 08:34:10 2025
    ACUS48 KWNS 220834
    SWOD48
    SPC AC 220832

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0332 AM CDT Sun Jun 22 2025

    Valid 251200Z - 301200Z

    ...DISCUSSION...
    ...D4/Wednesday...
    Extended-range guidance generally indicates that the persistent
    upper ridge across the eastern CONUS will begin to dampen on
    Wednesday. Multiple low-amplitude midlevel shortwave troughs will
    move along the periphery of the upper ridge from the
    central/northern High Plains into the Great Lakes. Mid/upper-level
    flow will generally be rather weak, but may be locally stronger in
    the vicinity of any shortwave troughs.

    Some severe threat could develop where pockets of somewhat stronger
    flow overlap moderate to strong buoyancy along the periphery of the
    ridge. An MCS may develop late on D3/Tuesday and move across parts
    of the central Plains and Midwest into at least early Wednesday.
    This MCS could persist through the day, with additional development
    possible along an outflow-influenced front. Other strong to severe
    storms may again develop across parts of the central/northern High
    Plains. Confidence regarding the details of any organized severe
    threat is too low to delineate a 15% area at this time.

    ...D5/Thursday - D8/Sunday...
    Guidance generally suggests that the persistent upper ridge will
    continue to weaken with time, resulting in a more zonal pattern by
    the upcoming weekend. Stronger flow may become increasingly confined
    to the northern tier of states. This could lead to periodic severe
    threats across parts of the northern Plains into the Great Lakes and
    Northeast.

    One area of interest is across parts of the northern Plains Friday
    into Saturday. Some guidance takes a mid/upper-level shortwave
    trough from the Pacific Northwest into the northern Great Plains
    during this period, where it may impinge upon increasing low-level
    moisture and instability, resulting in potential for organized
    severe storms.

    ..Dean.. 06/22/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Mon Jun 23 09:01:14 2025
    ACUS48 KWNS 230901
    SWOD48
    SPC AC 230859

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0359 AM CDT Mon Jun 23 2025

    Valid 261200Z - 011200Z

    ...DISCUSSION...
    ...D4/Thursday: Parts of the Midwest/Great Lakes...
    An area of interest for severe-storm potential on Thursday resides
    from eastern IA/southeast MN into northern IL/southern WI. A
    mid/upper-level shortwave trough is generally forecast to move
    across parts of the Midwest into the Great Lakes during the
    afternoon, potentially accompanied by a frontal wave. While
    deep-layer flow will generally remain rather modest, rich low-level
    moisture and strong heating will support moderate to strong buoyancy along/south of the front. Strong to potentially severe storms may
    develop as the approaching shortwave trough impinges upon the
    favorable buoyancy. Uncertainty regarding frontal position and the
    sufficiency of deep-layer shear precludes higher confidence at this
    time.

    ...D5/Friday: Northern Plains...
    An area of interest for Friday resides across parts of the northern
    Great Plains. A mid/upper-level shortwave trough is forecast to move
    across the northern Rockies toward the northern High Plains, though considerable spread remains regarding the timing of this relatively low-amplitude shortwave and attendant cold front. The front may
    impinge upon strong instability across parts of the Dakotas, with
    scattered storm and eventual MCS development possible. Deep-layer
    shear may remain relatively modest, but the magnitude of instability
    will likely support some organized severe threat.

    ...D6/Saturday: Northern Plains/Upper Midwest...
    Some continuation of severe-storm potential is possible into
    Saturday, potentially shifting eastward into the Upper Midwest.
    Spread in guidance becomes quite large at this range regarding
    placement of the warm sector Saturday afternoon, but strong
    instability and at least modest deep-layer shear could support
    severe storms along/east of the cold front.

    ..Dean.. 06/23/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Jun 24 08:58:49 2025
    ACUS48 KWNS 240858
    SWOD48
    SPC AC 240857

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0357 AM CDT Tue Jun 24 2025

    Valid 271200Z - 021200Z

    ...DISCUSSION...
    Models are in good agreement with the overall pattern through
    Tuesday/D8, depicting a low-amplitude trough moving from the
    northwestern states on Friday/D4 across the northern tier of states
    and toward the Great Lakes by around Sunday/D6. This wave is then
    forecast to amplify across Ontario/Quebec through the end of the
    period, with cooler/more stable air pushing south with a cold front
    from the Midwest into the Northeast.

    Severe storms are currently forecast over parts of the Dakotas into
    northwest MN on Friday/D4 as the stronger flow aloft interacts with
    a moist and unstable air mass already in place. Damaging winds
    appear the most likely mode of severe, along with sporadic large
    hail as storms form during the afternoon within a surface trough,
    and beneath increasing winds aloft. While severe storms may also
    occur on Saturday/D5 over parts of the northern Plains or upper MS
    Valley, predictability is lower given expected storms the previous
    day and potential for long-lived convective systems. However, given
    such strong instability forecast on Saturday/D5, a risk area is
    likely to be issued in later outlook cycles over parts of the upper
    Midwest/MS Valley.

    Elsewhere, daily thunderstorms within the moist and unstable air
    mass are forecast for the bulk of CONUS from the Plains eastward,
    though in a generally weak shear environment. Portions of those
    areas may see low/marginal probabilities as the events enter into
    the Day 3 outlook time frame.

    ..Jewell.. 06/24/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Wed Jun 25 08:30:54 2025
    ACUS48 KWNS 250830
    SWOD48
    SPC AC 250829

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0329 AM CDT Wed Jun 25 2025

    Valid 281200Z - 031200Z

    ...DISCUSSION...
    Models are in general agreement with the upper air pattern, but
    increasing spread is seen from Sunday/D5 and beyond.

    On Saturday/D4, a low amplitude wave will lift out of the
    ND/northern MN vicinity and move into Ontario. This will result in
    temporary height rises during the day before gradual falls occur
    overnight and into as a secondary wave moves from MT into the
    Dakotas overnight. Early day storms may exist over parts of northern
    MN in association with the low-level jet, and this activity could
    weaken during the day. Then, strong instability is forecast for
    several models, perhaps MUCAPE to around 5000 J/kg, over eastern SD
    and NE and into IA and MN. Heating within the surface trough may
    spur afternoon development from SD into NE, with some potential for
    activity to spread east/northeast. However, shear will likely be
    weak, with 500 mb winds averaging around 15 kt. Despite very strong instability, the weak-forcing situation in the wake of the exiting
    wave suggests low-predictability at this time.

    Around Sunday/D5, the secondary wave is forecast to amplify across
    the upper MS Valley and upper Great Lakes, with a cold front pushing
    south and extending roughly from WI to NE. Strong instability will
    likely exist ahead of such a boundary, though shear will again be
    weak. Still, storms will likely develop across the region, with
    areas of damaging gusts potential.

    From Monday/D6 through Wednesday/D8, the aforementioned trough will
    spread across the Great Lakes and Northeast, with what appears to be
    an end to the extreme instability levels. Scattered storms will
    likely persist over much of the Southeast and Mid Atlantic, with
    sporadic strong gusts daily.

    ..Jewell.. 06/25/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Thu Jun 26 08:54:09 2025
    ACUS48 KWNS 260854
    SWOD48
    SPC AC 260852

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0352 AM CDT Thu Jun 26 2025

    Valid 291200Z - 041200Z

    ...DISCUSSION...
    On the large scale, a low-amplitude upper trough over the northern
    Plains on Sunday/D4 will amplify as it moves toward the upper Great
    Lakes into Monday/D5, and more so into Tuesday/D6 when it will
    stretch across into the Northeast.

    At the surface, high pressure will extend into the northern to
    central Plains on Sunday/D4, with a trough affecting the upper MS
    Valley to central Plains. This trough/front will push farther south
    on Monday/D5, extending roughly from the OH Valley into the southern
    Plains, and eventually, into the Gulf Coast states into Wednesday/D7
    as high pressure spreads into the MS Valley.

    For the period, instability looks to be strongest on Sunday/D4 ahead
    of the front from NE/KS into IA/MO/IL with upper 60s to lower 70s F
    dewpoints common. While unstable, only weak westerly flow aloft will
    be present, and this will likely result in south to southwest
    propagating cluster of storms producing areas of gusty winds. Given
    substantial storm coverage over much of the central Plains to
    upper/middle MS Valley, predictability remains low for denoting
    precise risk areas.

    A low-end risk of severe storms with wind potential could develop
    into the Mid Atlantic on Tuesday/D6 as the Great Lakes/Northeast
    trough amplifies with westerlies increasing to 30 to perhaps 40 kt
    at 500 mb. Otherwise, scattered storms will also occur away from
    this boundary, across much of the Southeast as the moisture and
    instability remain in place in a weak shear environment.

    ..Jewell.. 06/26/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Fri Jun 27 08:58:43 2025
    ACUS48 KWNS 270856
    SWOD48
    SPC AC 270855

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0355 AM CDT Fri Jun 27 2025

    Valid 301200Z - 051200Z

    ...DISCUSSION...
    A mid-level trough will amplify across the Great Lakes at the
    beginning of the period D4/Monday and shift into the Northeast by
    Tuesday. A surface cold front will shift east across the Great Lakes
    on Monday and to the Northeast and Mid-Atlantic on Tuesday. Moderate instability may develop across a large area east of the Appalachians
    on Day 5/Tuesday. The strongest shear is forecast from Pennsylvania
    northward, beneath the strongest mid-level flow. However, the
    greatest instability should remain mostly south of this better flow.
    Therefore, a favorable corridor may develop for some strong to
    severe storms near the Mid-Atlantic/Carolinas where instability and
    modest shear overlap, but this remains too uncertain for severe
    weather probabilities at this time.

    Beyond Day 5, mid-level ridging will shift east across the central
    CONUS. At the surface, high pressure will build across much of the
    eastern CONUS. The combination of weak mid-level flow beneath the
    mid-level ridge and surface high pressure should limit severe
    weather potential for Day 6 and beyond. Strong instability is
    forecast to return to the northern Plains, but given the lack of
    mid-level flow, any storms will likely only be marginally severe at
    best. Some stronger mid-level flow may return to the northern Plains
    by next weekend as the ridge starts to break down, which may be the
    next chance for more organized severe storms in the latter portion
    of the extended period.

    ..Bentley.. 06/27/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sat Jun 28 08:02:06 2025
    ACUS48 KWNS 280801
    SWOD48
    SPC AC 280800

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0300 AM CDT Sat Jun 28 2025

    Valid 011200Z - 061200Z

    ...DISCUSSION...
    A mid-level trough will move from the Great Lakes to the Northeast
    on Day 4/Tuesday. At the surface, a cold front will move east
    through the period. Moderate instability is expected along this
    front and some severe weather may be possible from the Mid-Atlantic
    to the Northeast. Slight risk (15%) probabilities may eventually be
    needed within this zone, but there is potential for
    cloudcover/thunderstorm activity from Monday evening to impact
    destabilization. Therefore, confidence is not high enough for
    probabilities at this time.

    Beyond Day 4, a relative lull in severe weather potential is
    expected. Multiple reinforcing mid-level troughs will amplify the
    larger-scale trough across the eastern CONUS. As this occurs, the
    surface cold front will move south, potentially to the Gulf Coast
    and into the western Atlantic. This will eliminate the very moist
    airmass which resulted in moderate to strong instability across much
    of the eastern CONUS for the past few weeks.

    The greater low-level moisture is expected to remain and perhaps
    advect north across the central Plains beneath a large-scale ridge.
    This could result in some thunderstorm activity, but shear is
    expected to be very weak, and the building ridge aloft may suppress
    convection on D5/Wednesday to D6/Thursday.

    By next weekend, this ridge is expected to flatten with some
    stronger mid-level flow moving across the northern Plains. The exact
    evolution of the upper-pattern remains uncertain and therefore,
    confidence is low, but severe weather chances may increase across
    the northern Plains by next weekend.

    ..Bentley.. 06/28/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Sun Jun 29 08:21:42 2025
    ACUS48 KWNS 290820
    SWOD48
    SPC AC 290819

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0319 AM CDT Sun Jun 29 2025

    Valid 021200Z - 071200Z

    ...DISCUSSION...
    The cold front which may result in severe weather on Day 3/Tuesday
    will move into the Atlantic and near the Gulf Coast across Florida.
    A reinforcing mid-level trough will maintain northerly flow across
    the eastern CONUS as an area of high pressure builds into the
    region. A drier, more continental airmass across the eastern CONUS
    will keep severe weather chances minimal.

    Upper 60s to low 70s dewpoints will remain across the Plains,
    beneath a strong upper-level ridge. By the time the ridge starts to
    break down on Day 6/Friday some severe weather is possible as a
    mid-level trough moves into the northern Plains. However, the ECMWF
    shows less than 20 knots of flow across the Plains. Therefore, shear
    will likely be limited. Thunderstorms will be likely along the cold
    front as it traverses the central and eastern CONUS next weekend.
    However, the lack of stronger mid-level flow casts doubt on storm
    organization. Therefore, no severe weather probabilities have been
    added at this time.

    ..Bentley.. 06/29/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Mon Jun 30 08:55:14 2025
    ACUS48 KWNS 300855
    SWOD48
    SPC AC 300853

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0353 AM CDT Mon Jun 30 2025

    Valid 031200Z - 081200Z

    ...DISCUSSION...
    A mid-level ridge will start the extended period across the Plains
    on D4/Thursday. This ridge will shift east through the extended
    period. A surface low will develop in the lee of the Rockies and
    move slowly north and east, reaching eastern Ontario by D7/Sunday.
    This surface low and its associated cold front will likely be the
    only potential for any severe weather during the extended period.
    However, at this time it appears the stronger shear will be well
    displaced from the greater instability. Therefore, severe weather
    probabilities are not necessary at this time.

    Outside of this frontal zone during the Day 4 to Day 7 period,
    thunderstorms are likely. However, weak lapse rates and very weak
    shear is anticipated, with minimal storm organization.

    ..Bentley.. 06/30/2025

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  • From COD Weather Processor@1:2320/105 to wx-storm@lists.illinois.edu on Tue Jul 1 09:03:55 2025
    ACUS48 KWNS 010902
    SWOD48
    SPC AC 010900

    Day 4-8 Convective Outlook
    NWS Storm Prediction Center Norman OK
    0400 AM CDT Tue Jul 01 2025

    Valid 041200Z - 091200Z

    ...DISCUSSION...
    A mid-level trough will traverse the Northern Plains and Upper
    Midwest on Friday. This will likely be the most substantial severe
    weather threat during the extended period before broad, strong
    ridging builds across much of the eastern/central CONUS.

    ...Day 4/Friday...
    As a positively tilted mid-level trough traverses the northern
    Plains on Friday, strong southerly flow will advect moisture
    northward across a broad warm sector near the Upper Midwest. This
    will result in moderate to strong instability as temperatures warm
    well into the 80s. Widespread thunderstorms are likely along the
    frontal zone during the afternoon/evening. 35 to 40 knots of
    mid-level flow will overspread the warm sector which will provide
    some shear for storm organization. However, southwesterly surface
    winds will also increase during the afternoon within the warm front
    and therefore, the net shear may remain somewhat minimal. Some
    organized storms with a threat for large hail and severe wind gusts
    are possible, but the aforementioned concerns about deep-layer shear
    preclude the confidence needed for 15% severe weather probabilities
    at this time.

    Beyond Day 4, moderate to strong instability is forecast across much
    of the central and eastern CONUS with widespread thunderstorm
    activity likely. However, shear will remain mostly nebulous with the
    stronger mid-level flow confined to areas north of the better
    instability. Therefore, some marginal regional severe weather threat
    will be likely most days, but a more organized severe weather risk
    appears unlikely at this time.

    ..Bentley.. 07/01/2025

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