• HVYSNOW: Major US Storm

    From Dumas Walker@21:1/175 to All on Wednesday, January 10, 2024 08:44:00
    FOUS11 KWBC 100955
    QPFHSD

    Probabilistic Heavy Snow and Icing Discussion
    NWS Weather Prediction Center College Park MD
    454 AM EST Wed Jan 10 2024

    Valid 12Z Wed Jan 10 2024 - 12Z Sat Jan 13 2024

    ...Great Lakes and Northeast...
    Days 1-2...

    Strong surface low will be positioned near eastern lower Michigan
    to start the period, but will translate rapidly northeast with
    time through D1. This storm is quite wrapped up owing to an
    anomalous closed mid-level low directly overhead, and a strong
    secondary vorticity maxima rotating northeast into New England
    producing a strongly negative tilt. The vertical stack of the
    primary low will allow a secondary low to develop along the
    occlusion to the east, driving the most intense moisture advection
    into New England and then Canada by the end of D1. This moisture
    transport will remain exceptional, with IVT anomalies from NAEFS
    reaching +6 sigma over ME early on D1 before pivoting off into
    Canada the latter half of the day. This suggests the heaviest
    precipitation will be in northern New England, primarily in the
    higher terrain of ME, as strong accompanying WAA warms snow levels
    above 4000 ft, but WPC probabilities for additional snowfall
    exceeding 4 inches are only 20-30%, and only around Mt. Katahdin
    and Mt. Washington.

    As the low pulls away to the northeast, impressive CAA will
    develop on increasing N/NW winds which will support increasing
    coverage of lake effect snow (LES) downstream of the Great Lakes.
    Overall, LES appears modest in most areas as shortwave ridging
    returns quickly into D2. However, the most impressive LES is
    likely downstream of Lake Ontario into the Tug Hill Plateau where,
    despite this secondary shortwave approaching to locally back the
    mid-level flow to more W/SW, this will still support cool air
    moving across the long fetch of Lake Ontario to support heavy LES.
    WPC probabilities D1 and D2 exceed 80% for 4 inches both days.

    ...Central Plains to the interior Northeast...
    Days 2-3...

    A shortwave diving into the Pacific Northwest Thursday will race
    southeast across the Great Basin to reach the Southern Plains on
    Friday. This will drive a deepening longwave trough across the
    Intermountain West, with this trough pivoting eastward and
    elongating with time. As the primary vorticity maxima associated
    with the potent shortwave rounds the base of this trough and tilts
    negatively before closing off later Friday, the central part of
    the country will become entrenched within a potent and persistent
    trough to support yet another winter storm arcing from the Plains
    into the Northeast beginning Thursday night.

    The surface low is likely to develop Thursday evening in the lee
    of the Southern Rockies in response to PVA/height falls downstream
    of the potent shortwave, and within an area of increasing upper
    diffluence as a jet streak intensifies downstream of the longwave
    trough axis. Moisture will begin to return out of the Gulf on
    moistening 290-295K isentropic upglide, which will combine with SE
    700-500mb flow around the trough to surge PWs to +1 to +2 sigma
    according to NAEFS, highest across the lower MS VLY D2 and into
    the western OH VLY D3. This moisture will be acted upon by
    strengthening synoptic deep layer lift as the upper trough tilts
    negatively, and a coupled jet structure develops overhead and
    efficiently overlaps the greatest height falls. This suggests that
    the surface low will strengthen rapidly as it shifts northeast
    towards the Great Lakes by D3, with a large shield of
    precipitation expanding along its track.

    There remains considerable uncertainty into the exact track of
    this storm both in the deterministic models and the ensemble
    clusters, some of which is likely due to the impacts of the
    preceding storm and where it lays its residual baroclinic
    gradient. However, regardless of the exact track of this system,
    it is likely that along and north of the track, especially beneath
    what should become an intense TROWAL, heavy snowfall will occur.
    The synoptic evolution should support heavy snow bands both within
    the leading WAA, and again within any deformation axis that could
    develop on the NW side of the mature cyclone, especially by D3. It
    is too early to determine exactly where those will setup, but this
    is likely to be a strong and large-scale system with heavy snow
    spreading from portions of the Central Plains through the Great
    Lakes. WPC probabilities D2 for more than 4 inches of snow are
    40-70% in a narrow corridor focused around southeast Nebraska,
    before expanding considerably into D3 reaching above 50% from
    central Missouri through much of the Great Lakes region. Locally
    much higher totals are likely, reflected by WPC probabilities for
    more than 12 inches on D3 exceeding 40% from near Chicago and
    Milwaukee through much of the L.P. of MI.

    Additionally, later on D3, as the primary low occludes to a
    secondary triple point to its east, the best moisture flux should
    shift into New England where once again robust WAA should result
    in heavy snowfall in the higher elevations of Northern New
    England. WPC probabilities for more than 4 inches of snow are
    50-70% in the higher terrain of the Adirondacks, Greens, and
    Whites.

    Regardless of exactly where this system tracks, impacts are likely
    to be substantial as reflected by the WSSI-P indicating already a
    large area of 30-50% probabilities for moderate impacts due to
    snow rate, snow amount, and blowing snow.

    ...The West...
    Days 1-3...

    An extremely active pattern continues across the Pacific Northwest
    and into the Northern Rockies/Great Basin through late week as a
    series of shortwaves drop onshore from the Pacific.

    The first of these systems is moving onshore this morning and will
    drive a surface low/associated cold front through the Pacific
    Northwest and as far southeast as the Central Rockies by
    tonight.This is a potent shortwave but gets sheared out into
    significantly confluent mid-level flow as the longwave trough
    amplifies. This shortwave will dive all the way into the southern
    Great Basin by D2, and while it will weaken within the positively
    tilted trough, and encounter only modest available moisture, heavy precipitation is likely to extend as far southeast as the CO
    Rockies, with snow generally occurring above 1500 ft. WPC
    probabilities for snow exceeding 6 inches eclipse 80% along the
    Cascades and down into the Sierra, as well as into the Blue
    Mountains, higher terrain of the Great Basin, and into the
    Wasatch. Locally, more than 2 feet of snow is possible in the
    highest terrain of the Cascades and Sierra, and with snow levels
    crashing late D1, light snow accumulations are possible across
    many of the lower valleys as well.

    As that first trough digs across the Four Corners and intensifies
    into the next central U.S. low, the pattern begins to shift as the
    primary trough amplifies over Alberta and then digs southward,
    driving a surface cold front into a more NW to SE orientation as
    it drops into WA/ID/MT on Thursday. South of this trough,
    mid-level flow becomes increasingly pinched with W/NW flow
    impinging again into the Cascades and then spilling southeast
    across much of the West as the front sags southward. Although IVT
    will remain modest at less than 250 kg/ms according to NAEFS,this
    increasing moisture being acted upon by intensifying fgen along
    the cold front and amplifying upper diffluence ahead of an
    approaching jet streak should result in widespread snowfall once
    again spreading across the Northwest. As the pattern continues to
    evolve into D3, another shortwave approaching the Pacific
    Northwest coast will drive more impressive mid-level confluence,
    and the overlap of this pinched flow with the eastward translation
    of the upper jet will drive IVT to above 500 kg/ms, resulting in
    much more significant available moisture for precipitation. At the
    same time the cold front will be sharpening and dropping farther
    south, driving better ascent and lowering snow levels to the
    surface as far south as a roughly Portland, OR to Cheyenne, WY
    line. This strong ascent, steep lapse rates beneath the cold pool,
    lowering snow levels, and ample moisture, will produce heavy snow accumulations, spreading southeast with time. On D2 WPC
    probabilities for more than 6 inches exceed 80% in the Cascades,
    Blue Mountains, Salmon River/Sawtooth region, and the Northern
    Rockies, with 2+ feet probable in the higher terrain. During D3
    the greatest WPC probabilities shift south slightly, focusing in
    the OR Cascades and east across the northern Great Basin into the
    Tetons and Wasatch. Again on D3, local totals exceeding 2 feet are
    likely. Additionally, especially by D3, with snow levels
    collapsing towards the surface, moderate accumulations are
    becoming more likely in the valleys and lowlands, with Seattle, WA
    and Portland, OR both featuring 30-40% probabilities for at least
    2 inches of snowfall.

    Finally, the strong cold front moving across Oregon this morning
    will continue to shift rapidly southeast across the Great Basin
    and into the Central Rockies by Thursday morning. This could
    spread convective snow showers and snow squalls across the area,
    with the CIPS snow squall parameter showing values above +1
    spreading as far south as the Four Corners states. Evaluation of
    the fields which drive the snow squall parameter indicate the
    threat has increased this morning as the coverage of overlapping
    sufficient 0-2km RH/925mb fgen/SBCAPE>100 J/kg to support intense
    squalls is more widespread, especially along and immediately
    behind the front. Snow squalls should still generally be
    scattered, but more numerous convective snow showers are also
    likely which could cause brief but significant travel disruptions
    due to gusty winds and heavy snow rates.

    Weiss

    ***Key Messages for Jan. 8-13 Major Winter Storm***
    --Continuing Blizzard Impacts in the Northwest
    Periods of heavy snow will continue through this afternoon in the
    Northwest. An additional 6-12 inches of snow will bring storm
    total accumulations to several feet in the higher elevations of
    the Cascades and Olympics. Gusts to at least 60 MPH will create
    blizzard conditions, continuing considerable travel impacts for
    many mountain passes.

    --Heavy Snow in the Sierra
    Heavy snow rates of 1-2"/hr will cause significant snowfall
    accumulations likely (70-90%) exceeding 12 inches in the Sierra
    today. Strong winds of 40-50 MPH during the heaviest snow will
    produce difficult travel.

    --Snow squalls across the Great Basin and Four Corners
    Snow squalls are likely behind a cold front through tonight. These
    intense bursts of snow pose a significant danger to motorists as
    rates of 1-2"/hr combine with strong wind gusts to produce rapid
    changes in visibility, occasional whiteouts, and possible flash
    freezes on roadways.

    --Significant Central U.S. winter storm begins Thursday night
    Confidence has increased that this system will emerge into the
    Plains Thursday and strengthen into a potent winter storm by
    Friday. Uncertainty continues in the track and intensity of this
    system, but a swath of heavy snow is likely from the Central
    Plains through the Great Lakes where the probability of exceeding
    4 inches is above 70% from eastern Nebraska through lower
    Michigan. Considerable blowing and drifting of this snow in strong
    winds also possible.
    $$
    --- SBBSecho 3.14-Linux
    * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)
  • From Dumas Walker@21:1/175 to All on Thursday, January 11, 2024 08:54:00
    FOUS11 KWBC 110857
    QPFHSD

    Probabilistic Heavy Snow and Icing Discussion
    NWS Weather Prediction Center College Park MD
    356 AM EST Thu Jan 11 2024

    Valid 12Z Thu Jan 11 2024 - 12Z Sun Jan 14 2024

    ...Great Lakes and Northeast...
    Day 1...

    Well-defined shortwave trough over southern WI will quickly shift
    east across MI and the Northeast today given the strengthening jet
    to its south while another impulse over northeast ND will drift
    east across northern MN today. Both will produce Great Lake
    enhanced snow today with 40-60% Day 1 snow probs for >6" over the
    North Shore of MN and 40-60% probs for >4" east of Lakes Erie and
    Ontario for westerly flow lake enhanced snow this
    afternoon/evening in NY.

    ...Central Plains, Great Lakes and interior Northeast...
    Days 1-3...

    A digging trough crossing AZ today will take on a negative tilt
    after crossing the southern Rockies this evening as a
    double-barreled jet becomes more buckled and S-shaped across the
    Great Lakes into Friday. This will drive strong upper level
    divergence and rapid surface cyclogenesis with a deepening area of
    low pressure lifting Friday from the Ozarks through the Midwest
    and over the L.P. of MI Friday night. This is a strikingly similar
    track to the exiting system though it forms farther east over the
    Plains). Snow will rapidly increase in coverage and intensity
    north of the low this evening over the central Plains and then IA
    through MI late tonight through Friday evening. As the low tracks
    away on Saturday, intense lake-effect snow develops, covering all
    five Great Lakes by Saturday night.

    Initial WAA over colder sfc air tonight will likely support a
    wintry mix in the rain to snow transition zone from northeast KS
    into northern IL. North in the snow zone, significant snowfall is
    expected on the northwest side of the low as a deformation band
    forms and slowly pivots across the area, coincident with an
    intense TROWAL as the WCB wraps into the low. High-end potential
    is >18" per PWPF from peak development and lake enhancement in
    southeast WI and northeast portions of the L.P., driven by strong
    UVV into a sufficiently deep DGZ. Day 1.5 snow probs for >8" are
    20-50% from eastern Neb through central IA, increasing on the Day
    2 to 40-90% from the WI/IL border across the L.P. The powerful
    cyclone reaches peak intensity over the L.P. Friday night with
    MSLP in the low 970s making for very strong winds and a blizzard
    threat north and west of the low through this time.

    Strong northwest to west flow on the back side of the low
    envelopes the Great Lakes in the wake with LES beginning off Lake
    Superior Saturday and the rest of the Great Lakes by late Saturday
    night and continuing in earnest through at least Sunday night. Day
    3 snow probs for >6" are 40-80% for typical NW and W snow belts.

    On the eastern side, cold air mass in place will slowly be eroded
    as broad southerly flow once again erodes sub-freezing
    temperatures. The uneven erosion in the column will likely lead to
    a period of snow to freezing rain to rain in most areas outside
    northern Maine as a triple point low moves across the area. Before
    the changeover, several inches of snow will likely accumulate over
    terrain in interior portions of the Northeast with Day 2.5 WPC
    snow probabilities for >6" are 40-80% over the Adirondacks and
    White Mtns.

    ...The West...
    Days 1-3...
    Active winter pattern continues over The West through this weekend.

    A positively-tilted trough digging down the Sierra Nevada early
    this morning crosses Arizona today and the southern Rockies this
    evening. Snow levels around 4000ft along the Mogollon Rim and
    north-central NM ranges along with decent Pacific-sourced moisture
    brings 40-80% Day 1 snow probs for >6" to these areas.

    A shortwave trough digging down British Columbia as it rounds a
    low over northern Alberta is the leading edge of the coldest
    air-mass of the winter season to date, reaching into the interior
    Northwest starting tonight and spreading across the Great Plains
    through Saturday. Northwesterly flow off the coast of British
    Columbia will strengthen as Alberta low and an expansive ridge
    extending north through Alaska funnel Pacific moisture into the
    Northwest and up the Columbia River Gorge today. With a strong
    dome of Arctic high pressure (possibly approaching record high
    pressure observations for the time of year in southwest Canada), a
    plume of moisture running into the boundary, and the added help of
    strong topographic ascent along ranges oriented orthogonally to
    the mean flow, heavy snow mountain snow is expected to develop
    across the southern WA through the OR Cascades into the northern
    Rockies today with snow levels generally 2000ft or less. Day 1 WPC
    PWPF shows high chances (>70%) for >12" of snowfall in the OR
    Cascades and Blue Mountains and moderate (around 50% for the ID
    Bitterroots to the Sawtooth. This focus shifts south through
    Friday before being reinforced by a ridge cutting shortwave trough
    that reaches the OR coast on Saturday with Day 2 probs expanded to
    even larger areas of the OR Cascades, Sawtooth and the Wasatch.

    A vorticity maximum shearing off from a long wave trough over the
    northeast Pacific will develop an area of low pressure that tracks
    towards Oregon coast Saturday morning. This wave will direct an
    atmospheric river to far southern OR through far northern CA
    Friday night with IVT values topping the 97.5 climatological
    percentile. With cold initial conditions from the Arctic air
    spreading south, heavy snow is expected at the onset with snow
    levels in northern CA initially around 3000ft before rising to
    5500ft on Saturday. Day 3 PWPF for >8" is 50-80% over the OR
    Cascades, down the Sierra Nevada, across the ranges of the
    northern Great basin, the Wasatch, and the western CO Rockies. The
    warming onshore flow on Saturday looks to also cause a wintry mix
    over west-central OR where a glaze of ice is possible. Day 3 PWPF
    for >0.25" are 30-40% over the southern Willamette Valley west
    into the Coast Ranges.

    Jackson

    ***Key Messages for Jan 11-14 Major Winter Storm over the Midwest***

    -High Confidence in Major Midwest Snowstorm
    Heavy snow is expected in the Midwest with a powerful winter
    storm. The greatest confidence in heavy snow exists in southern
    and eastern Wisconsin, and western and northern Lower Michigan,
    where over 12 inches of snow is likely (60-80%), causing
    considerable disruption.

    -Blizzard Conditions Possible with Strong Winds
    Strong winds will spread into the Midwest and Great Lakes on
    Friday and Saturday with the unusually powerful low pressure
    system. This will make blizzard conditions possible, particularly
    in exposed areas. Winds will increase on Friday night and the
    drastically reduced visibility will make travel dangerous to
    impossible. Wind gusts of 40 to 50 MPH may also lead to some power
    outages.

    -Lake Effect Snow Persists This Weekend
    While the larger area of snow will begin to diminish on Saturday,
    the arrival of colder air will generate heavy snow downwind of the
    Great Lakes this weekend. Winds will remain strong, posing a risk
    for significant blowing snow.

    -Flooding and Severe Storms in the South and East
    Severe thunderstorms will be possible Thursday and Friday in the
    Gulf Coast and Southeast. Another round of rain in the
    Mid-Atlantic and Northeast will lead to renewed rises on rivers
    and streams and possibly flooding. Moderate coastal flooding is
    also likely in the Mid-Atlantic and Northeast.

    ***Key Messages for mid-January Arctic Blast***

    -Bitter Cold Surges South and Affects Most of U.S.
    The first significant Arctic outbreak of the winter will arrive in
    the northern Rockies and northern Plains Thursday night and
    Friday, before advancing farther south and east through much of
    the Plains and Midwest this weekend. Numerous daily cold records
    are likely in the south-central U.S. on Sunday, Monday, and
    Tuesday.

    -Dangerously Cold Wind Chills Expected
    At the peak of the Arctic outbreak early next week, minimum wind
    chills should fall below zero into Texas and the interior
    Southeast. Wind chills this weekend across the northern Plains and
    northern Rockies should be below negative 30 degrees. This will
    pose an increased risk of frostbite on exposed skin and
    hypothermia. Have a cold survival kit if you must travel.

    -Heavy Snow in the West Friday and Saturday
    Arctic air will gradually lower snow levels in time for the
    arrival of another storm system in the West on Friday. This may
    lead to snow and considerable impacts in valleys in Oregon, Idaho,
    Nevada, and Utah, including the Portland, Boise, and Salt Lake
    City metro areas. Freezing rain is likely Saturday in western
    Oregon.

    -Southern, Northeast Snow Early Next Week
    Snow is likely on the periphery of the advancing Arctic air mass
    from the interior South into the Mid-Atlantic Sunday into Monday
    and possibly over the Northeast into midweek. Stay tuned for
    further details.
    $$
    --- SBBSecho 3.14-Linux
    * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)
  • From Dumas Walker@21:1/175 to All on Friday, January 12, 2024 09:18:00
    FOUS11 KWBC 120925
    QPFHSD

    Probabilistic Heavy Snow and Icing Discussion
    NWS Weather Prediction Center College Park MD
    424 AM EST Fri Jan 12 2024

    Valid 12Z Fri Jan 12 2024 - 12Z Mon Jan 15 2024

    ...Central Plains to the Great Lakes and Interior Northeast...
    Days 1-3...

    A soon-to-be negatively-tilted trough axis over North Texas early
    this morning will continue to rapidly develop as it turns
    northeast over MO today, reaching southern Lake Michigan by this
    evening. Complimentary jet become S-shaped across the Great Lakes
    will drive strong upper level divergence and robust surface
    cyclogenesis with a deepening area of low pressure lifting from
    the Ozarks early this morning to the L.P. of MI tonight. A swath
    of heavy snow from eastern Neb through IA into northern IL will
    continue to slowly pivot northeast downstream of the low, lifting
    over WI and MI through tonight. As the low tracks northeast to
    Quebec on Saturday, intense lake-effect snow will develop,
    covering all five Great Lakes by Saturday night which continues
    into midweek.

    A wintry mix in the rain to snow transition zone through the WAA
    precip continues this morning in a stripe over northern IL before
    the system becomes dominated by just a rain-snow delineation.
    North in the snow zone, significant snowfall is expected on the
    northwest side of the low as a deformation band forms and slowly
    pivots across the area, coincident with an intense TROWAL as the
    WCB wraps into the low with a deep DGZ. The areas of greatest snow
    potential (15-20 inches) remain eastern WI where the pivoting band
    has lake enhancement which is also present over northeast portions
    of the L.P. and in the Huron Mtns of the U.P. where lake
    enhancement turns into lake effect snow. The powerful cyclone
    reaches peak intensity over the L.P. tonight with MSLP in the low
    to mid 970s making for very strong winds and likely blizzard
    conditions north and then west of the low.

    Day 1 WPC probabilities for at least 12 inches after 12Z are
    greater than 50% over southern and eastern WI, northeastern
    portions of the L.P. and the Huron Mtns in the U.P. which is the
    favored snow belt favored in N-NW flow. There, strong northwest to
    eventually west flow on the back side of the low envelopes all of
    the Great Lakes with LES beginning off Lake Superior Saturday and
    the rest of the Great Lakes by late Saturday night and continuing
    in earnest through at least Sunday night with LES persisting over
    all the lakes into Wednesday. Day 2 snow probs for more than 8
    inches are over 50% for typical NW and W snow belts in the U.P.
    including the Porcupine Mtns and 20-40% along the western shore of
    MI, around Buffalo, and the Tug Hill. The powerful wind should
    fracture dendrites which should limit max SLRs despite the deep,
    saturated DGZ. Day 3 snow probs for more than 6 inches are high
    around Buffalo and on the Tug Hill with some additional values in
    the eastern U.P. Westerly flow LES then continues trough
    Tuesday/possibly Wednesday.

    On the eastern side of the approaching front, cold air mass in
    place over the interior Northeast will slowly be eroded as broad
    southerly flow scours out sub-freezing temperatures. The uneven
    erosion in the column will likely lead to a period of snow to
    freezing rain to rain in most areas of eastern NY and interior New
    England outside northern Maine as a triple point low moves across
    the area. Before the changeover, several inches of snow will
    likely accumulate over terrain in interior portions of the
    Northeast with Day 1.5 WPC snow probabilities for more than 6
    inches highest (generally >70%) over the Adirondacks, Green &
    White Mtns, and interior Maine (North Woods).

    ...The West...
    Days 1-3...

    An active wintry pattern will continue throughout much of the
    mountain ranges along the West Coast, much of the Great Basin to
    the Colorado Rockies through this weekend across the boundary of
    Arctic cold air over this region. A shortwave trough pushing into
    WA from BC is rounding a deep low centered over Alberta and send a
    surge of potently cold air over the Northwest today before
    stalling over southern OR where it will persist through this
    weekend. A rich plume of 850-700mb moisture running along this
    boundary, along with topographic lift will allow heavy snow to
    continue over the OR Cascades, across southern ID, northern UT and
    the Wasatch, to the CO Rockies today. Day 1 PWPF for >8" are high
    (over 90%) along the OR Cascades and the Wasatch and moderate
    (40-70%) over southern ID into northern NV. Strong winds are
    expected in this tight baroclinic zone with blizzard warnings up
    in southern ID.

    Meanwhile a compact southern stream low cuts through the North
    Pacific/Alaska ridge tonight, reaching the OR Coast late Saturday.
    This storm system will tap into a conveyor belt of moisture that
    has origins into the subtropics. The combination of anomalous
    moisture and a strong 850mb jet will lead to IVT values
    approaching the 99th climatological percentile being directed at
    southern Oregon and northern California. This brings further heavy
    snowfall in the Oregon Cascades with the footprint expanding south
    through the Sierra Nevada. Confidence is highest in heavy snowfall accumulations along the stationary front from southern Oregon and
    northern Nevada to the Wasatch which is at the nose of the strong
    IVT plume emanating out from the northeast Pacific. Day 2 WPC PWPF
    sports high chances (>80%) for more than 8 inches of snowfall over
    the OR Cascades/Trinity Alps/Sierra Nevada east through the
    northern Great Basin ranges, the Wasatch and the CO Rockies.

    As this wave comes ashore, warm air riding over the Arctic air at
    the surface sets up a significant freezing rain case for northwest
    OR into southwest WA. Day 2 PWPF for more than 0.25 inches of ice
    area 30 to 60% over much of the Willamette Valley south of
    Portland west through the Coastal Ranges.

    Ridging begins to shift east into The West Sunday, with precip
    shifting east. Day 3 PWPF for more than 8 inches is moderately
    high (50-80%) over the Wasatch and CO Rockies south through the
    NBM border in the San Juans. All told, three day totals of over 4
    feet are expected on the highest OR Cascades and Wasatch with 2
    feet or so for the Sierra Nevada and CO Rockies. Also noteworthy
    are low probabilities for more than two inches over the Portland
    metro on both Days 1 and 2.

    ...Mid-South...
    Day 3...

    The southern stream shortwave trough that slices through the North Pacific/Alaska ridge tonight crosses the southern Rockies Sunday
    and rounds the base of the expansive trough over the central part
    of North America Sunday night. Gulf moisture is available to ridge
    up and over the cold front that pushes through Texas and well into
    the Gulf, allowing precip to break out over North Texas/OK before
    crossing AR into TN and northern MS/AL. Sufficient cold air in
    this Arctic airmass allows moisture in the DGZ with SLRs in the
    mid to upper teens. There remains uncertainty with the
    strength/timing of this wave/reinforcing waves with the 00Z ECMWF
    stepping back its QPF footprint over the area, but for now the Day
    3 snow probs for >4" are 10 to 40% from OK across northern AR well
    into western TN. Given the strength of the jet under this trough
    and the particularly cold air, having accumulating snow over this
    area is a good bet, so stay tuned for further updates.

    Jackson


    ***Key Messages for Jan 10-14 Major Winter Storm over the Midwest***

    --Conditions Deteriorate Rapidly Today in Midwest
    Heavy snow will continue to spread across the Upper Midwest today.
    Snowfall rates of 1 to locally 2 inches per hour will lead to
    hazardous travel conditions over much of the region

    --Blizzard Conditions Likely with Strong Winds
    Winds will increase through tonight in the Midwest and Great Lakes
    as the storm system rapidly strengthens. Blizzard conditions are
    likely, particularly in exposed areas. Travel will become
    dangerous to impossible with whiteout conditions. Power outages
    are possible.

    --Lake Effect Snow Persists This Weekend
    While the larger snow area will diminish on Saturday, the arrival
    of colder air will generate heavy, wind-driven snow downwind of
    the Great Lakes this weekend into midweek. Whiteout conditions in
    the blowing lake effect snow are expected in the stronger lake
    effect snow bands.

    --Flooding and Severe Storms in the South and East
    Severe storms will be possible in the South today and damaging
    gusts may occur outside of thunderstorms. Heavy rain in the
    Mid-Atlantic and Northeast tonight and Saturday will lead to
    renewed rises on rivers and streams and possible flooding.
    Moderate coastal flooding is likely in the Mid-Atlantic and
    Northeast Saturday, with significant impacts. Major coastal
    flooding is possible in New Hampshire and Maine.


    ***Key Messages for mid-January Arctic Blast***

    --Bitter Cold Surges South and Affects Most of U.S.
    The first significant Arctic outbreak of the winter arrives into
    the Northwest, the northern Rockies, and northern Plains today,
    before advancing farther south and east this weekend and early
    next week. Numerous daily cold records are likely.

    --Dangerously Cold Wind Chills Expected
    Sub-zero wind chills will affect much of the U.S. and reach into
    portions of the South. Wind chills this weekend across the
    northern Plains and northern Rockies will be below negative 30
    degrees on a widespread basis, and as cold as negative 50 to 60
    degrees on Saturday morning in Montana and the western Dakotas.
    This will pose an increased risk of frostbite on exposed skin and
    hypothermia. Have a cold survival kit if you must travel.

    --Heavy Snow in the West Today and Saturday
    Arctic air will gradually lower snow levels in time for the
    arrival of another storm system in the West today. This will lead
    to snow and considerable impacts in valleys in Oregon, Idaho,
    Nevada, and Utah, including the Portland, Boise, and Salt Lake
    City metro areas. Significant freezing rain is likely Saturday in
    northwestern Oregon.

    --Additional Wintry Precipitation Early Next Week
    Areas of snow, sleet, and freezing rain are likely on the
    periphery of the advancing Arctic air mass from the interior South
    into the Northeast. Stay tuned for further details as the forecast
    may change.
    $$
    --- SBBSecho 3.14-Linux
    * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (21:1/175)