• Storm Prediction Center 10 08

    From LU9DCE@21:5/101 to ALERT on Sat Aug 10 04:10:01 2019
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    ESTACION DE PACKET RADIO - BUENOS AIRES (GF05OM)
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    MD 1684 CONCERNING SEVERE POTENTIAL...WATCH UNLIKELY FOR PARTS OF
    SOUTH CENTRAL NEBRASKA
    Mesoscale Discussion 1684 NWS Storm Prediction Center Norman OK
    0109 AM CDT Sat Aug 10 2019
    Areas affected...Parts of south central Nebraska
    Concerning...Severe potential...Watch unlikely
    Valid 100609Z - 100815Z
    Probability of Watch Issuance...5 percent
    SUMMARY...Isolated strong storms may continue to pose a risk for
    severe hail and locally strong surface gusts south of Broken Bow
    into the Kearney, Lexington and Holdrege areas of south central
    Nebraska through 3-5 AM CDT.
    DISCUSSION...Strong thunderstorm development continues, mainly
    focused across central Nebraska, near the Broken Bow area, where
    a couple of storms may still be producing severe hail and locally
    strong surface gusts. Even this activity has exhibited recent
    weakening trends, and there appears little mid/upper support.
    However, convection has been focused within stronger low-level warm
    advection, aided by the nocturnal southerly low-level jet, along the
    eastern periphery of a low-level moist axis which is contributing
    to CAPE of 1500-3000 J/kg. In the presence of strong vertical
    shear, beneath modest northwesterly mid-level flow, occasional re-intensification of an isolated storm or two might still be
    possible, with a tendency for convection to propagate southward
    toward the Kearney, Holdrege, Lexington areas through 8-10Z.
    ..Kerr/Thompson.. 08/10/2019
    ...Please see www.spc.noaa.gov for graphic product...
    ATTN...WFO...GID...LBF...
    LAT...LON 41589986 41289894 41049856 40609833 40199898 40379979
    41589986
    SPC 1200Z Day 1 Outlook
    Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1202
    AM CDT Sat Aug 10 2019
    Valid 101200Z - 111200Z
    ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM EASTERN
    OREGON INTO WESTERN MONTANA...FROM SOUTHERN MONTANA INTO FAR NORTHERN WYOMING...AND OVER A SMALL PART OF EASTERN NORTH CAROLINA...
    ...SUMMARY... Severe storms producing large hail and locally
    damaging wind gusts are expected from eastern Oregon into western
    and southern Montana during the afternoon and evening. A cluster of
    storms, some severe, is also expected over eastern North Carolina
    during the afternoon. Other isolated activity is likely from the
    Black Hills into the central High Plains with marginal hail and wind. ...Synopsis... An upper low will move northeastward across OR, with
    cooling aloft spreading over ID and western MT. At the surface, low
    pressure will exist over northern NV into southern ID, with a cold
    front from northwest NV into eastern OR late in the day. Increasing
    southerly winds along with heating will result in scattered storms,
    some with large hail and locally damaging winds, mainly from eastern
    OR into western MT.
    To the east, an upper ridge will exist over the High Plains, with
    weak lee troughing and backed surface winds aiding westward moisture
    transport and destabilization. Scattered daytime storms are again
    likely from southern MT into eastern CO, and isolated severe storms
    cannot be ruled out from afternoon through early evening.
    Meanwhile, an upper trough will lift across the Northeast, with
    moderate northwest flow across the Mid Atlantic. A surface trough
    will develop over the Carolinas, with a stalled front over NC
    providing a focus for clusters of strong to severe storms.
    ...OR into southwest MT... The overall setup for severe storms
    appears more robust than on the previous day, with lift over
    a large area and impressive lapse rate profiles and deep-layer
    shear. Scattered storm coverage is likely by mid afternoon as capping
    will be removed by 18Z, with storms becoming numerous over central
    ID and into western MT by late afternoon. Hail will strongly be
    favored with long hodographs, and a few damaging wind gusts will be
    possible. Other isolated cells are expected to form over eastern OR,
    and over Owyhee county ID which will then move across the valley
    with a threat of hail in excess of 1.00" (with isolated reports
    to ping-pong or golf ball size). A few storms may affect extreme
    eastern WA as well. The threat of hail may persist into the evening
    as the upper trough continues across the region providing lift.
    ...Eastern North Carolina... The combination of a stalled front,
    a sea breeze, and strong inland heating of a very moist air mass
    will lead to MLCAPE in excess of 2000 J/kg, beneath west/northwest
    winds aloft which will lengthen hodographs. A cluster of strong to
    severe storms is expected to form around 18-19Z, with splitting cells
    possible. Hail will be possible despite warm midlevel temperatures,
    along with a few damaging wind gusts.
    ...Southeast MT into northern WY... East to northeast surface
    winds will maintain a band of upper 40s to lower 50s F dewpoints
    over southern MT and northern WY, with storms expected to form over
    the higher terrain by 21Z. Southwesterly mid to upper-level winds
    will result in long hodographs favoring cells capable of hail,
    and perhaps a few severe wind gusts with any small bows.
    ...Eastern CO into western KS and southern NE... Strong instability
    will develop with heating beneath the upper ridge from eastern CO
    into western KS/NE, with easterly surface winds counteracting mixing
    of dewpoints. Storms will form over the Front Range by around 21Z,
    and may produce a few damaging wind gusts as they travel across CO
    and into western KS. Other storms are possible along a modifying
    outflow boundary, possibly near I-80, with localized severe wind
    or hail late in the day.
    ..Jewell/Cook.. 08/10/2019
    SPC 0600Z Day 2 Outlook
    Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1256
    AM CDT Sat Aug 10 2019
    Valid 111200Z - 121200Z
    ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER A PORTION
    OF THE CENTRAL PLAINS...
    ...SUMMARY... Areas of strong to severe storms are expected over
    portions of the northern through central High Plains Sunday into
    Sunday night.
    ...Synopsis...
    Upper trough now approaching northern CA will transition to an open
    wave and continue through the northern Rockies and northern High
    Plains Sunday and Sunday night, flattening the northern periphery
    of an upper ridge centered over the southern Plains. By 12Z Sunday a
    cold front will extend from northern MN southwest into northeast WY.
    The western extension of this boundary will stall before moving
    north as a warm front through eastern MT. A secondary front will
    extend from a weak surface low in IA westward through southern NE.
    The western extension of this boundary will stall near the KS/NE
    border.
    ...Central High Plains region...
    Model consensus is that storms may be ongoing over a portion of
    northern KS into southern NE within zone of isentropic ascent on
    nose of a southerly low-level jet. This activity is expected to
    shift east and diminish during the day. In wake of morning storms,
    rich low-level moisture with mid-upper 60s F dewpoints and diabatic
    warming will support a corridor of moderate to strong instability
    (2000-2500 J/kg MLCAPE) in vicinity of the stalled front. Easterly
    upslope flow will exist north of this boundary, and storms are
    expected to develop over the higher terrain as well as near the
    front/lee trough intersection during the late afternoon and spread
    east during the evening. Belt of moderate (35-40 kt) southwesterly
    mid-level winds will develop in gradient zone between the ejecting
    upper trough and the southern Plains upper ridge supporting 40-45
    kt effective bulk shear, especially in vicinity of the front where
    surface winds will be backed to east southeast. Some supercell
    structures appear likely as the initial storm mode, before evolving
    into lines/clusters and spreading east through NE overnight. Large
    hail and damaging wind will be the primary threats, through a couple
    of tornadoes will also be possible.
    ...Northern Rockies through northern High Plains...
    Moist axis will be shunted southwestward by the south-advancing
    cold front, before retreating back north as a warm front through
    eastern MT. The corridor of modest low-level moisture with upper 50s
    F dewpoints beneath steep mid-level lapse rates will support moderate instability (1500-2000 J/kg from central MT through northeast WY
    and possibly southwest SD as the surface layer warms during the
    afternoon. Storms are expected to develop over the higher terrain and
    spread northeast through the relatively narrow instability corridor
    during the afternoon and early evening. A belt of stronger winds
    aloft accompanying the upper trough will support 40-45 kt effective
    bulk shear supportive of organized storms including a few supercells
    with large hail and damaging wind the main threats.
    ...MAXIMUM RISK BY HAZARD... Tornado: 5% - Slight Wind:
    30% - Enhanced Hail: 30% - Enhanced
    ..Dial.. 08/10/2019
    SPC Day 1 Fire Weather Outlook
    Day 1 Fire Weather Outlook NWS Storm Prediction Center Norman OK
    1247 AM CDT Sat Aug 10 2019
    Valid 101200Z - 111200Z
    ...CRITICAL FIRE WEATHER AREA FOR EAST-CENTRAL NEVADA AND FAR
    WESTERN UTAH...
    ...Synopsis... A mid-level trough just off the northern California
    coast will begin to transition into an open wave and take on a
    negative tilt while ejecting toward Idaho today. As this occurs,
    a belt of enhanced mid-level flow will shift eastward toward the
    western Great Basin, overspreading dry areas of NV/UT/ID during peak
    heating hours. Meanwhile, areas of thunderstorms will once again
    affect portions of the Northwest, with isolated dry thunderstorm
    potential expected during the afternoon, evening, and overnight.
    ...Eastern Nevada, western Utah, and eastern Idaho... Beneath the
    belt of enhanced mid/upper flow, vertical mixing processes and
    a favorable surface gradient will favor increased surface winds
    within this corridor during peak heating hours. Areas of 15-25
    mph south-southwesterly winds will become common amidst critically
    low RH values and broad areas of dry fuels in areas unaffected
    by recent rainfall. At this time, it appears that the greatest
    confidence of critical fire weather thresholds being exceeded will
    occur across east-central NV, far west-central UT, although locally
    critical fire weather can be expected as far north as eastern Idaho. ...Northern California through Washington and eastward into western
    Idaho for thunderstorms... The presence of cool temperatures aloft
    associated with the mid-level trough resulted in broad areas of
    wetting thunderstorms especially from central into north-central
    Oregon this afternoon and evening. These wetting downpours have
    undoubtedly altered fuel states in several areas, and widespread
    wetting thunderstorms are also expected to develop and migrate
    from south to north this afternoon and evening also. The isolated
    dry thunder area covers the potential for dry lightning strikes on
    the periphery of wetting thunderstorm cores in areas that continue
    to have cured fuels that can sustain fires.
    ..Cook.. 08/10/2019
    ...Please see www.spc.noaa.gov/fire for graphic product...
    SPC Day 2 Fire Weather Outlook
    Day 2 Fire Weather Outlook NWS Storm Prediction Center Norman OK
    1247 AM CDT Sat Aug 10 2019
    Valid 111200Z - 121200Z
    ...Synopsis... Fire weather conditions will gradually improve
    some as a persistent West Coast mid-level low weakens and migrates northeastward toward the central Rockies. Most of the thunderstorm
    potential evident over OR/CA and vicinity the past few days will
    lessen in the midst of subsidence aloft west of the mid-level trough. Meanwhile, slackening flow aloft over the Great Basin will result
    in weaker winds and a lessened (locally elevated) fire weather
    threat in these areas. A lingering risk of elevated fire weather
    will extend from eastern Idaho into western Wyoming Sunday afternoon. ...Eastern Idaho, far northern Utah, and western Wyoming... As the
    mid-level wave ejects northeastward, a belt of enhanced mid-level
    flow will migrate away from the western Great Basin and reach
    the discussion area during peak heating hours. Vertical mixing
    processes beneath this flow will result in areas of 15-25 mph
    westerly surface flow for several hours. RH values will only flirt
    with critical thresholds on a limited/localized basis, however, and
    should mitigate the overall fire risk. Dry fuels should continue to
    support a risk of fire spread especially with ongoing fires, however.
    An isolated thunderstorm may also occur especially in eastern Idaho
    and vicinity, though coverage atop dry fuels currently does not
    warrant any dry thunder delineations for this outlook.
    ..Cook.. 08/10/2019
    ...Please see www.spc.noaa.gov/fire for graphic product...

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