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Posts posted by Dalfy

  1. Sleet ending in STL metro within an hour or so it looks like. I think they're anticipating some lingering freezing drizzle to continue into evening minimal ice accumulation. Overall I think we got around or just under a slushy inch, within their call. Got in a little jeb walk yesterday during the first round so I'm about as satisfied as I could be with this storm. 

  2. Really great summary of the two waves for those in the LSX forecast area.

    As was previously discussed, two relatively distinct rounds of
    wintry precipitation will impact the region. The first round, forced
    mainly be isentropic overrunning stimulated by a shortwave amidst
    southwesterly mid-level flow, will draw wintry precipitation into
    the region. Latest short-range ensembles and CAMs now indicate a
    weaker, more confined area (largely along/south of I-70) of wintry
    precipitation with this first round. From a conceptual standpoint,
    this makes sense as the upper-level synoptic forcing and isentropic
    ascent is not impressive by any stretch. Model soundings Wednesday
    evening illustrate a sub-saturated DGZ, with a deep saturated layer
    beneath that amidst modest lift. A stout warm nose that barely peaks
    above freezing aloft can be discerned between I-70 and I-44, but any
    hydrometeors that melt will most likely refreeze as sleet in the
    deep cold layer beneath. Further south still, we will likely see
    more mixing of rain and sleet where the warm layer is deeper. While
    accumulations with this initial round will be lighter compared to
    the next bout on Thursday (as the forcing within the system is so
    weak), the onset timing coinciding with the evening rush hour will
    likely lead to travel impacts.
    Overnight Wednesday into early Thursday morning, what weak
    overrunning and forcing that does exist will further diminish and
    precipitation will become lighter and more scattered across the
    southern CWA. Some model soundings hint at the potential for
    freezing drizzle during this "lull" overnight. A nearly-saturated
    layer extending from near the surface to around 700mb exists
    overnight south of I-70 with some modest lift in the layer. While
    light, a glaze of ice cannot be ruled out for some during this
    relative break in the system.
    The more impressive of the two waves will move into the bi-state
    area during the early morning on Thursday and will re-stimulate
    precipitation areawide in time for the morning commute.
    Deterministic guidance agrees that the orientation and depth of the
    mid-level trough will not be favorable for more robust surface
    cyclogenesis. While a low will be deepening, it will be slow to do
    so given the weak amplification and diffluence in the mid/upper
    levels. As such, moist isentropic ascent and overrunning would be
    the main sources of forcing for this second round. This scenario is
    supported in the isentropic fields among the deterministic guidance,
    which shows more extensive and impressive isentropic lift across the
    Precipitation types will vary across the region tomorrow. North of I-
    70 will see almost exclusively snow, but given the lack of a more
    robust synoptic system any mesoscale banding that would cause more
    intense localized snow totals are highly unlikely. Another aspect
    working against higher snow totals: the DGZ never saturates in any
    notable way, which severely decreases the efficiency of dendritic
    growth. This scenario is further supported by the NBM interquartile
    range for snow not including amounts larger than 4" in the northern
    CWA. There is some raw guidance that suggests higher amounts, but
    they are likely being influenced by sleet contamination. For the
    area that will largely see accumulating snow and not much changing
    precipitation type, a Winter Weather Advisory was issued this
    South of this area, along I-70 south to just south of I-44, a
    corridor of significant sleet is expected to develop and cause
    notable impacts to travel for the morning commute Thursday. Model
    soundings show more notable lift compared to the first wave, with a
    largely-similar thermodynamic profile. NBM probabilities of sleet
    are also relatively high in the mid/late morning through the
    afternoon (topping out at 60%, but may still be too low). Sleet
    accumulations up to 1" can be expected, which would be quite
    impactful. As such, a Winter Storm Warning was issued for the
    areas where sleet accumulations would exceed 0.5".
    Further south still, the depth of the warm nose aloft will be much
    more pronounced, which in turn makes the cold air below it more
    shallow. This would be a much more favorable scenario for freezing
    rain, especially if surfaces cool as precipitation falls with the
    first wave of wintry mix Wednesday evening. That being said,
    accumulations on roadways will still be limited as the sun angle for
    this time of year and barely-freezing conditions will not promote
    efficient accretion. Admittedly, this forecast may be a bit too
    bullish on those ice totals, especially if the above-mentioned
    limitations come to fruition. On elevated surfaces, which would
    be a bit cooler, ice accretion would be more efficient and could
    lead to downed tree limbs and power outages in southeast Missouri
    and southwest Illinois. Given the potential for significant
    impacts and ice accumulations, a Winter Storm Warning more
    specifically for ice was issued across southeast Missouri and
    southwest Illinois.
    Precipitation wanes during the evening Thursday from west to east as
    the system intensifies and ejects east out of the region.
    Temperatures stay below average and skies begin to clear as our
    third winter system in as many weeks comes to an end.
  3. Beautiful outside. Snow is very powdery and blowing everywhere. Rates are not as high as I'd hoped, I may have slept through the best of it, but it's still great to watch. This was a very spread the wealth storm, which I've also appreciated quite a bit. 

  4. We're officially all snow, at 12z, ~4-8 hours earlier than short term guidance forecasted [RGEM, RAP, HRRR] up until 1 or 2 last night. I'm really looking forward to the afd as they also went with short term in suggesting changeover would occur sometime in mid morning through early afternoon. 



    • Like 1
  5. 9 minutes ago, Hoosier said:

    Changeover taking a little longer to happen than most models indicated around here.

    Don't take my word for it but I think it'll be in the next 2-3 hours max. Current wetbulb temps; check the time trend on spc:


  6. Maples' rough estimate of changeover- Jefferson, MO and metro. 1-4am sounds right and earlier than Canadian guidance by 10-12 critical hours. I don't think I'll be able to sleep monitoring this haha:

    .AVIATION...  (For the 06z TAFs through 06z Wednesday Night)
    Issued at 1040 PM CST Tue Feb 1 2022
    A high impact winter storm is imminent with a broad area of
    precipitation stretching from central Illinois southwestward
    through a large portion Missouri. Rain transitioned to all snow at
    KUIN around 02z this evening with the transition affecting KCOU
    between 03z and 04z. Following shortly behind will be KJEF around
    the release of this update. Metro terminals will likely follow
    between 07z and 10z.


  7. For those in LSX: 

    FXUS63 KLSX 020254
    Area Forecast Discussion...Updated
    National Weather Service Saint Louis MO
    854 PM CST Tue Feb 1 2022
    Issued at 830 PM CST Tue Feb 1 2022
    A broad area of precipitation stretches from interior sections of
    central Illinois to southwest Missouri this evening. Coverage and
    arrival time of the precipitation is in good agreement with
    expectations so far.
    Automated surface observations show sub-freezing air making
    progress into portions of northeast Missouri and west-central
    Illinois. Rain transitioned to a brief period of freezing
    rain/sleet around Quincy before changing to all snow around the
    02z hour. Reports of all snow in Hannibal also provide ground
    truth to the advancing cold air.
    What has been evident over the last 3-4 hours is that the cold air
    has run about 20-25 miles further southeast than hourly forecast
    trends previously depicted. Updates have been made to reflect this
    trend with the potential that FZRA/PL could be 1-2 hours ahead of
    schedule, should this trend win out. The only question remains
    the warm nose aloft and how long it holds/erodes tonight into the
    morning period. This trend will need to be monitored through the
    night, as any deviation will have the greatest impact on
    accumulations near the transition zone (southeast MO/southwest

    Current rain snow line:



  8. It seems MBY continues to be at a real battleground with respect to warm layer. 18z RGEM and 12z GGEM maintain warm layer aloft well into Thursday which keeps us mixed for most of the event; NAM, EURO, GFS have trended toward warm layer cooling by late Wednesday night/00z Thursday which keeps us snow for precip thrust from the main low which is resulting in these boosted forecast totals. I'm liking my chances especially given the new 00z guidance, we'll see how RGEM and GGEM trend tonight. EDIT: RGEM came in slightly cooler, with changeover around 6z Thursday.

  9. 24 minutes ago, Chambana said:

    12z euro crushes E Central Illinois and Central Indiana. 

    oops a little behind didn’t see the posts above me pertaining to it. 

    ILX is going to get shellacked. It seems like track is relatively consistent, I'm just hoping the warm nose erodes fast enough for us in St. Louis. 

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