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Mailman

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  1. .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/...
    A series of shortwaves withing SW flow will increase wintry precipitation
    chances Monday into Tuesday as the longwave central U.S. trough axis
    shifts slightly eastward. At the sfc, a low will develop and deepen 
    as it moves from the Mississippi Delta towards the northeast U.S., 
    with cold air filtering into the region Tuesday as it moves farther 
    east of the Upper Ohio River Valley. 
    
    Confidence remains high in accumulating snowfall for much of the 
    region and the second wave late Monday into Tuesday being the more 
    significant punch. The combination of colder air, strong 
    frontogenetic forcing and jet support will help produce potentially 
    heavy snow around and to the north/west of Pittsburgh, a Winter 
    Storm Watch was issued. Additional headlines are likely for the rest 
    of the region as confidence increases in the timing and the type of 
    impacts expected.
    
    That said, granular details for each wave remain inconsistent between
    models and from run to run for both incoming waves. Among the varying
    details through the event include positioning of a mid-level 
    frontogenetic zone; strength of ascent and associated connections to
    a briefly coupled jet; strength and shifting of a baroclinic zone 
    southeast of Pittsburgh leading to more of a wintry mix or freezing 
    rain; efficiency of freezing rain accumulation; and potential dry 
    slotting within the SW flow reducing accumulation efficiency. 
    
    Increasing sfc high pressure and shortwave ridging will develop in
    the wake of the exiting shortwave/low Tuesday night, with single
    digit temperature likely for most locations.
  2. .LONG TERM /MONDAY THROUGH FRIDAY/...
    The sw flow over the Upper OH is forecast to continue next week with
    a series of crossing shortwaves within flow defining precip chances,
    the most significant indicated for Tuesday. With plentiful boundary 
    layer moisture evident in relatively warmer swly flow, ascent 
    provided from a northern stream open wave, assisted by coupled jet 
    and coincident near sfc frontogenesis will prime the region with the 
    ingredients necessary for a widespread precipitation event on 
    Tuesday. 
    
    While longer range solution output varies in terms of snow 
    accumulations (GFS vs. ECMWF), a couple of considerations should be 
    noted. The first is that both models indicate the location of the 
    mid-level low west and north of the forecast area. With the region 
    located within the warm sector, this would imply the potential for a 
    wintry mix across portions of the region (especially south of I-80) 
    as warm advection hinders overall snow growth efficiency and 
    introduces other hazards such as sleet/freezing rain. GEFS plumes for
    PIT hint at this hindrance as the operational GFS snow accumulation 
    output is much higher than majority of other members. Other 
    considerations include the anticipated quick progression of the storm
    which implies a rather progressive, open wave in conjunction with 
    anticipated dry slotting. This translates to precipitation 
    diminishing rather rapidly later Tuesday. Nonetheless, hazardous 
    wintry weather should be anticipated, especially early Tuesday, and 
    headlines may be required. This will bear watching through the course
    of the weekend with more updates to follow.
  3. .LONG TERM /MONDAY THROUGH THURSDAY/...
    The southwest flow ovr the Upr OH is forecast to continue next week
    with shortwaves within flow defining precip chc, the most 
    significant indicated for Tuesday. Current depictions are for the mid
    level low to dig toward the Great Lakes, thus limiting snow and 
    overall precip potential via warm advection and dry slotting. Still, 
    mixed precipitation including freezing rain is expected with such a 
    scenario, development which will have to be monitored.
    
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