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Dalfy

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Posts posted by Dalfy

  1. STL had a pretty intense band set up about an hr ago - ~25-30dbz. We're back down to light snow. 

    Picture2.jpg

    Our AFD mentions up to an inch in our metro associated with the area of lift. [on an unrelated note: I'm really trying to expand my knowledge of some of these terms they use in the AFD - frontogenesis, isentropic lift. I'm not in any math heavy fields, and I looked through the weather 101 forum without much avail to find a conceptually-focused guides that could help me interpret better. If anyone has any good, beginner-friendly sources I'm all ears and open hands]

    • Like 1
  2. Very nice discussion by STL crew regarding the final days of the arctic air mass: 

    .LONG TERM... (Thursday through Monday)
    Issued at 426 AM CST Tue Feb 16 2021
    
    Deterministic guidance is now in good agreement for Thursday.  Where
    in past runs there were a range of solutions, some producing another
    significant snow storm for the area, the latest GFS and ECMWF both
    keep the entire area dry on Thursday as the trough aloft continues
    to dig into the Gulf of Mexico, resulting in low level cyclogenesis
    along the coast.  The Mid Mississippi Valley is too far back into
    the cold/dry Arctic air on Thursday.  Even the GEFS >0.01 QPF
    probability map has only 10-20% over our far southern counties, and
    the more likely chances down across the Bootheel.  I did leave some
    token slight chance PoPs in for parts of the area on Thursday to
    cover those very low chances in the ensemble, but if the trend
    continues we`ll be able to pull those by this afternoon.
    
    The remainder of the forecast will be characterized by a warming
    trend into the weekend and early next week as the upper level
    pattern shifts.  The persistent eddy in the northern stream that`s
    been hanging over the CONUS and keeping us locked in such a cold
    surface pattern over the past week will finally fill in and move
    east.  This pattern shift will finally shut the door to the Arctic
    which had been left standing open since February 6th and
    temperatures will begin warming back toward normal.  The snow
    pack will slow our moderation down somewhat, and it`s unlikely
    highs will get above freezing until at least Saturday.  However, by
    Monday it could be a balmy mid to upper 40s across the area.
    
    Carney
    

     

     

     

  3. So incredible outside. It hasn't been since, maybe 2016 that I've had the chance to walk through rates as intense as this. Visibility still very low here-maybe a few blocks worth, with a very fine-grain +SN [wind is hard to gauge since I'm deep in the city]. Temp is 3 degrees. Not sure how much we've accumulated since it's all drifted around. 

  4. Glass from  STL, really interesting disco:

    Light snow with pockets of moderate snow cover the majority of
    the CWA early this morning. This snow is occurring in response to
    a broad region of mid level frontogenetic forcing and weak
    isentropic upglide, with a little added help from a weak vort max
    moving across MO at this time. Light snow wavering in intensity is
    expected to persist through mid-morning and could briefly end in
    some areas. The ongoing winter storm will really get going after
    around 15z with the greatest overall intensity centered on this
    afternoon. Guidance is all in good agreement showing a classical
    evolution per conceptual models as the upper trof currently over
    the southern Plains ejects northeastward and becomes negatively
    tilted, leading to a deepening surface low tracking from the
    north- central GOM through the TN Valley. Strong large scale
    forcing associated with the upper trof, stout mid-level
    frontogenetic forcing associated with a cyclonically turning
    branch of the warm conveyor belt, and coupled ULJs will lead to
    robust ascent across southeast and east central MO into west
    central IL. This strong ascent within a deep dendritic growth zone
    will result in high snowfall rates and heavy snow during the
    aforementioned time frame. The HREF, HRRR, and RAP all are showing
    snowfall rates at times of 1+ in/hr. I`m in new territory
    estimating the SLRs as never in my 30+ years forecasting have I
    dealt with a major storm with this cold of an airmass. I am using
    20:1 or greater and they increase with time. This results in
    additional snowfall from 600 am today through midnight of 5-9
    inches within the winter storm warning area, the highest amounts
    along an axis from near Fredericktown to Salem IL. This corridor
    is good agreement with well established techniques from
    climatologies by Goree & Younkin, Browne & Younkin, and Gosselin
    using the track of the 850 mb low center. The model consensus of
    this 850 mb low track is from central AR skirting the bootheel to
    just north of Louisville. Gusty winds with the tightening pressure
    gradient and the light fluffy nature of the snow will bring
    concerns for blowing and drifting. To top this off we remain in
    the throes of bitterly cold air and dangerous wind chills. Travel
    is not recommended. If you become stranded it could result in a
    life-threatening situation. Outside of the warning area, a solid
    2-5 inch snowfall looks in order. The current winter storm warning
    and advisory look on target. The storm system should completely
    exit and area by 06-09z with bitterly cold air and dangerous wind
    chills continuing into Tuesday morning. A few record lows may be
    possible Tuesday morning and the record low maxes today will again
    be shattered. The wind chill warning and advisory in effect until
    noon Tuesday looks good as well.
    
    Tuesday is still looking like a down day with weak surface high
    pressure dominating. Very cold temperatures will continue. There
    could be some flurries around in the morning due to lingering
    stratus.
    
    Glass
    

     

     

    • Like 1
  5. 14 minutes ago, WeatherMonger said:

    Can you make my call as well? :lol:

     

    Only thing out of ILX on Facebook is about the cold. Someone asked them about higher totals, sais LSX had mentioned it but they did not respond.

     

    Went to LSX page and seen this. Cautiously optimistic, yet knowing howbthings usually pan out keeps me a bit pessimistic.

     

    Screenshot_20210214-144906_Facebook.thumb.jpg.b04256488ecc2a0e29cb94882b052a37.jpg

    Nice! Looking like they'll upgrade us soon. 

    EDIT: just happened: 6-9'' call STL metro

  6. 54 minutes ago, Dalfy said:

    STL's criteria is >=6 inches I believe. They haven't updated their AFD or forecast since this morning at 6, before the NW shift; they were calling 4-6'' which is under their warning criteria. 

    "Other potential areas for concern with this forecast are exactly
    what the SLRs will be and whether we might be a tad low on snowfall
    for Monday. Given the very cold air mass, snow ratios should be high
    with dendrites dominating. Present thinking is that storm total snowfall
    amounts will range from 2-3 inches in far northeast MO and west
    central IL to 4-6 inches encompassing the remainder of the CWA.
    These totals agree well with GEFS exceedance guidance using a max
    SLR, and are in the 50-90th percentile of the NBM. Noteworthy is
    our operational NBM data looked a bit light on QPF for Monday. The
    winter weather advisory looks on target for this event considering
    the aforementioned expectations and has been expanded to include
    the remainder of the northern CWA."

    Glass from STL CWA, stuck to his guns in the 1pm update. It's also interesting they're the only CWA to not expand wind chill warnings south of the central portion of their forecast area.

    
    Other potential areas for concern with this forecast are exactly
    what the SLRs will be and whether we might be a tad low on snowfall
    for Monday. Given the very cold air mass, snow ratios should be high
    with dendrites dominating. Present thinking is that storm total snowfall
    amounts will range from 2-3 inches in far northeast MO and west
    central IL to 4-6 inches encompassing the remainder of the CWA.
    These totals agree well with GEFS exceedance guidance using a max
    SLR, and are in the 50-90th percentile of the NBM. Noteworthy is
    our operational NBM data looked a bit light on QPF for Monday. The
    winter weather advisory looks on target for this event considering
    the aforementioned expectations and has been expanded to include
    the remainder of the northern CWA.
    
    
     

     

     

     

     

  7. 6 minutes ago, Snownado said:

    I don't understand why the warnings are so far north along the IN/IL border on the IN side but drop much further south on the IL side. Can anyone explain ?

    STL's criteria is >=6 inches I believe. They haven't updated their AFD or forecast since this morning at 6, before the NW shift; they were calling 4-6'' which is under their warning criteria. 

    "Other potential areas for concern with this forecast are exactly
    what the SLRs will be and whether we might be a tad low on snowfall
    for Monday. Given the very cold air mass, snow ratios should be high
    with dendrites dominating. Present thinking is that storm total snowfall
    amounts will range from 2-3 inches in far northeast MO and west
    central IL to 4-6 inches encompassing the remainder of the CWA.
    These totals agree well with GEFS exceedance guidance using a max
    SLR, and are in the 50-90th percentile of the NBM. Noteworthy is
    our operational NBM data looked a bit light on QPF for Monday. The
    winter weather advisory looks on target for this event considering
    the aforementioned expectations and has been expanded to include
    the remainder of the northern CWA."
  8. 2 hours ago, Air Traffic Control said:

    I heard the cry for lurkers to appear...

    Lurker from about an hour east of the St. Louis city, and seeing that bright pink bulls eye moving slowly to my location is... Well, as a person who grew up in an island with snow a foreign word [or the precursor to the apocalypse], the amount of hype I'm feeling is beyond ecstatic!!

    We still have graupel from last week hanging around - radiant heat has turned the top layer to ice, but it's still majestic to see. About 2" or so - the air not being above freezing since the 5th or so ofFeb helps. Was also a brutal -1°F, too, this morning. I've never been so cold before in my life...

     

    Our AFD from yesterday:

    "As the main surface system passes south and east of the CWA overnight Sunday into Monday, the probability of accumulating snow ramps up mainly along and south of the I-70 corridor. Upper-level divergence from the trough and mid-level frontogenesis will couple with cold air to produce efficient snow-to-liquid ratios. By the time this system departs the CWA Monday afternoon and evening, snowfall will range from 2-5 inches along and south of the I-70 corridor. I continue to have confidence in these totals, as blended and ensemble guidance continue to focus the greatest snow potential and amounts along this corridor."

    Learning moment: never have significant confidence in models >48 hours out, lol. 

    • Haha 1
  9. STL's AFD. They feel confident w/ call for 2-5'' along and south of I70 within their CWA

    Quote
    The other threat we`re focused on is the accumulating snow starting
    across portions of central Missouri Sunday morning and continuing
    through Monday evening. Here, an upper-level trough will eject out
    of the southwestern U.S. and push eastward. A leading impulse within
    this trough will spark precipitation late Sunday morning across
    portions of central Missouri. Higher probability of snow will spread
    eastward, primarily across portions of northeastern Missouri and
    west-central Illinois through the day. Snowfall within this first
    round will be around an inch or less mainly focused in central and
    northeastern Missouri through west-central Illinois.
    
    As the main surface system passes south and east of the CWA
    overnight Sunday into Monday, the probability of accumulating snow
    ramps up mainly along and south of the I-70 corridor. Upper-level
    divergence from the trough and mid-level frontogenesis will couple
    with cold air to produce efficient snow-to-liquid ratios. By the
    time this system departs the CWA Monday afternoon and evening,
    snowfall will range from 2-5 inches along and south of the I-70
    corridor. I continue to have confidence in these totals, as blended
    and ensemble guidance continue to focus the greatest snow potential and
    amounts along this corridor.
    
    
    Elmore

     

  10. STL's AFD

    Quote
    .LONG TERM...  (Sunday through Friday)
    Issued at 419 AM CST Sat Feb 13 2021
    
    The screaming message from last night has not changed 24 hours later
    with bitterly cold air/record temperatures, dangerously cold wind
    chills, and accumulating snowfall the highlights into next week.
    Record low max temperatures Sunday into Monday still look like a
    slam dunk, however I have less confidence in record low temperatures
    due to persistent cloud cover. Still generally all but southeast
    MO and far southwest IL will have mins below zero through Monday
    and the entire CWA may have mins below zero on Tuesday morning.
    
    The increasingly active upper air pattern starting later this
    weekend and continuing into next week will bring accumulating
    snowfall to the region first Sunday into Monday. This first event
    will come in two waves. On Sunday the consensus is the first wave
    will be focused from central MO into west central IL associated with
    a weak impulse in the southwest flow aloft and attendant mid level
    frontogenetic forcing. Snowfall amounts with this wave generally
    look light, around an inch or less. The more substantial snowfall
    will occur with the second wave centered on Sunday night and Monday.
    The best focus for this snowfall will centered along and south of I-
    70 associated with increasing low-mid level frontogenetic forcing
    and increasing large scale forcing occurring ahead of a migrating
    upper trof. Until late Monday the models lack a coherent 850 mb
    low which could offer even greater snowfall potential. However
    this combination of persistent frontogenetical forcing and large
    scale support with the trof, and very cold temperatures yielding
    high snow ratios, should still produce a solid measurable
    snowfall of 2-5 inches across much of the CWA with the highest
    amounts along and south of I-70 in the 4-5 inch range. The NBM and
    GEFS exceedance probabilities support this region for the highest
    snowfalls with good support for 4+ inches. If the amounts stay in
    these ranges then this would be an advisory level event, and
    those headlines would likely becoming later today.
    
    We are still eyeing another system in the Wednesday-Thursday time
    frame. There are some rather significant differences in the
    models with regards to the depth and speed of this next migratory
    upper trof, with some solutions indicating possibly a light snow
    and others a rather classic winter storm. Like last night,
    confidence in the specifics remains low. The very cold, well
    below normal temperatures will continue mid-late week.
    
    Glass
    

     

  11. 3 minutes ago, Hoosier said:

    Raid the stores Houstonians

     

    Inland Harris-
    Including the city of Houston
    429 PM CST Thu Feb 11 2021
    
    
    .SUNDAY NIGHT...Light freezing rain, snow and sleet in the late
    evening and overnight. Little or no snow and sleet accumulation.
    Lows in the upper 20s. Chance of precipitation 60 percent in the
    evening increasing to 80 percent after midnight.
    .WASHINGTONS BIRTHDAY...Mostly cloudy with light freezing rain,
    snow and sleet in the morning, then partly cloudy with a chance
    of light freezing rain, snow and sleet in the afternoon. Snow and
    sleet accumulation up to 1 inch. Colder. Highs in the lower 30s.
    Chance of precipitation 80 percent in the morning decreasing to
    40 percent in the afternoon.

    I feel for all those tech migrants from California. 

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