Jump to content

MillerA

Members
 View Profile  See their activity

  • Posts

    318

  • Joined

  • Last visited

 Content Type 

Posts posted by MillerA

    Potential 1/28-1/30 2022 winter storm

    in Southeastern States

    Posted

    GSP Disco - Ouch for the piedmont..They appear not thrilled about advisory level snow. 

      

    SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY/...
As of 230 PM EST Thursday: Guidance continues to indicate that
a midlevel trough will sharpen over the Tennessee Valley Friday
evening, even as a 120kt upper jet shifts over the Carolinas,
amplifying into a split stream pattern aloft. This allows upper
divergence to blossom off the NC coast overnight, and paired
with deep-layer DPVA streaming into the Carolinas, this will
result in rapid, potent cyclogenesis off the central Georgia
coast. Both deterministic and ensemble guidance continues to
favor the eastward, just-offshore track for the developing
surface low, which suppresses a robust warm conveyor belt across
the NC/SC Piedmont and inhibits development of a warm nose
aloft, allowing for a rare rain-snow-only forecast for the NC
Piedmont and SC Upstate.

From perhaps 00Z Saturday onward, strengthening NW flow across the
mountains will result in a widespread rain-snow mix beginning Friday
evening, transitioning to all-snow by midnight.  Lee troughing
east of the mountains appear to result in the development of an
additional circulation over the Piedmont, depicted in the HREF as a
small-scale low pressure system which skirts just north of the NC-SC
border.  As a result, a changeover from rain to snow is expected
across the NC Piedmont and at least the northernmost part of the SC
Upstate, before profiles dry out leading up to daybreak Saturday.
So, at this point, the NC Foothills/Piedmont and SC Upstate are
forecast to see small accumulations, below advisory criteria; the
NC mountains will see more appreciable snowfall.  A Winter Weather
Advisory has been issued for Buncombe and northern Jackson Counties,
while an elevation-dependent Winter Weather Warning-Advisory has
been issued for counties along the NC-TN border.

After daybreak Saturday, the rapid intrusion of dry cP air on the
backside of the departing system will sap profiles of their ability
to produce precipitation, even as Z500 heights rebound.  Gusty winds
embedded in post frontal CAA are likely across the mountains
and, more sporadically, the NC/SC Piedmont. Clear, dry
conditions will maximize radiative cooling Saturday night,
allowing temps to drop into the mid- to low-teens across most of
the forecast area.

    January 20-22 “bring the mojo” winter storm threat

    in Southeastern States

    Posted

    Gsp discussion 

    TERM /THROUGH TONIGHT/...
    As of 1045 AM EST: Upper divergence is ramping up, as indicated
    by cooling cloud temps streaming into the area thanks to right
    entrance region jet dynamics. This forcing is causing more snow
    to fall and seed the low-level moisture across the NC mountains
    (lots of reports of accumulating snow). So far, all the model
    guidance seems to be struggling with this (consensus PoPs are less
    than 15%). So it`s really challenging to assess how much this will
    continue as we head thru the day. For now, think QPF will be very
    light, and will handle with a Special Wx Statement (SPS). But an
    advisory may be needed, if banding sets up (or the snow just stays
    more persistent than expected). Outside the mountains, there`s
    a deeper dry layer preventing the seeder-feeder mechanism at the
    moment. However, both the NAM and GFS fcst soundings show overall
    moistening profiles this aftn, and frontogenesis will ramp up toward
    sunset, as a strong shortwave approaches from the west. The banding
    will be parallel to the frontal zone (SW-NE orientation), but
    the exact placement is still up for debate among the guidance. It
    could very well set up over the southern and central NC mountains,
    extending to the NW NC Piedmont. Then, things will shift SE, and the
    best rates are still expected to be from Greenwood, SC to Cabarrus,
    NC and points E. This is where our current Winter Wx Advisory is,
    and that looks good. With the overall trends in the guidance since
    the 00z runs trending a little higher QPF this evening further
    west into the Piedmont, we may need to expand the advisory. But
    there`s still not enough confidence, and will assess all the 12z
    guidance and the latest radar/satellite trends before making a
    decision. Will handle non-mountain snow/black ice concerns with
    an SPS as well for now.

    Otherwise, temps/dewpts/sky/wind all look good. It`s just the
    PoPs/QPF/SnowAmt we`re really concerned about.

    A strong short wave drops into the area tonight along with a
    strong upper jet streak. This induces cyclogenesis off the SE
    coast. The surface low remains relatively far off shore. The H85
    low is also to our east. This keeps the low level flow weak and E to
    NE. There is quite a bit of low level moisture across the area but
    no significant moisture flux from either the Gulf or Atlantic. There
    is an increase in deep moisture late this afternoon and evening
    though. Given the strong forcing and decent moisture, have trended
    toward the higher precip chances seen in the guidance. That said,
    don`t have any likely PoP west of the I-77 corridor. Expect there
    will be precip moving west to east across the area, but coverage
    and QPF will be limited. Forecast soundings and partial thickness
    values suggest mainly snow for most of the area. Some sleet will
    be possible at onset, with more of a rain/snow mix over NE GA,
    the western Upstate, and the warmer NC valleys to start. Precip
    changes to all snow before ending after midnight.

    Highs today and lows tonight will be well below normal.

     

    • Like 1

    Jan 15-16 Winter Storm

    in Southeastern States

    Posted

    2 minutes ago, MillerA said:

    Gsp noaa weather office has out their afternoon discussion, and have updated local forecast. Enjoy. 

    LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
    As of 240 pm EST Wednesday: The forecast for the weekend remains in
    a state of flux. Readers are advised to continue to manage their
    expectations. On the one hand, confidence continues to increase
    that we will have a winter storm that will probably impact the
    entire forecast area beginning Saturday night and continuing
    through most of Sunday. Precip probs are now into the categorical
    for that time period. On the other hand, details about precip-type
    distribution are very murky in both space and time, and that is
    having a negative impact on confidence. The latest problem is
    the operational GFS solution, which has trended toward moving the
    850 mb low well west of the mtn chain, allowing for strong warm
    advection that would establish a warm nose in most places east
    of the mtns. The result would be a steady changeover/mix to sleet
    and freezing rain, if the operational GFS is correct. It is worth
    noting the 12Z GEFS is still holding onto snow as the most likely
    p-type at GSP, but there is enough of an increase in sleet/freezing
    rain outcomes that places like CLT have an almost equal chance of
    the primary p-type being any one of the four. Meanwhile, the ECMWF
    keeps its 850mb low moving overhead/southeast of the mtn chain. The
    operational ECMWF would allow for a long enough period of time for
    snow to fall east of the mtns before a weaker warm nose pokes up
    from the south to changeover along/S of I-85. Worth considering is
    that in most situations, the warm nose wins across the area south of
    I-85. Still way too early to consider amounts of individual p-types,
    but the trend in the QPF has gone up substantially, which will
    in turn flow down into the precip accums. The forecast guidance
    blend used to create the new fcst will sometimes show a lag that
    does not quickly jump to any new trend, so for the time being,
    the fcst will look more like the cooler ECMWF/Canadian ensembles
    instead of the more icy GFS. High temps will not get out of the
    mid-30s. Eventually, as the system passes, a change back toward
    light snow should happen late Sunday. Model guidance shows a strong
    signal toward a NW Flow Snow event along the TN border Sunday night
    that would continue through Monday and might not taper off until
    Tuesday morning. Temps will remain about 10 degrees below normal
    through Tuesday, with a warming trend into Wednesday. Another
    weaker system may approach from the west Wednesday afternoon,
    but this was downplayed for the time being.

    January 8th-9th threat

    in Southeastern States

    Posted

    Gsp short term. Not putting catawba and iredell into the warnings yet. 

     

    As of 1015 am: Water vapor imagery shows upper low centered near
    Ark-La-Miss junction. Associated cirrus shield will continue
    spilling over the downstream ridge into the forecast area throughout
    the afternoon, resulting in generally mostly cloudy/partly sunny
    conditions. Filtered insolation will likely result in max temps
    around 5 degrees below normal across much of the area this
    afternoon.

    Model consensus carries the surface low south of the I-20 corridor
    late today through Friday morning, with the core of the upper
    low moving near the southern border of TN and NC during this
    time frame. This will place most of the CWA just on the cool side
    of the warm front. Most of the area will start off well above
    freezing in the early evening; moisture will quickly deepen as
    the sfc/upper low encroach on the area before midnight, bringing in
    precip chances from the SW. The strongest dynamic forcing will
    precede the upper low into the area, peaking in the predawn hours
    Friday, with the better moisture lagging the forcing somewhat. The
    best frontogenetic forcing will occur nearer the warm front. Precip
    type still looks quite tricky, mainly east of the mtns, and perhaps
    across the mountain valleys of southwest NC. There will be a lot of
    midlevel dry air to overcome early in the event, and the WAA gives
    us a weak warm nose as well (though not as strong as we often see
    with these sorts of systems). The higher mountains likely will see
    snow through most of the event, but lower elevations and areas
    further south will see some period of sleet, or perhaps even
    freezing rain where the warm nose (along with evaporative cooling
    diminishing it at least locally) is present. Confidence is
    sufficient such that all zones in the Watch were converted to a
    Warning earlier this morning with the exception of Catawba, Iredell,
    and Davie Counties in NC. This area will take longer to see
    accumulation reach any criteria, and with the potential for
    accumulations to go one way or the other, we have held off on
    upgrading there. These areas almost certainly will need an Advisory
    or Warning depending on where their final forecast total ends up.

    With the upper low crossing the area during the day Friday, even as
    winds turn more downslope and moisture becomes more shallow, there
    will remain support for significant precip as the deformation zone
    scrapes the NC Piedmont. Temperatures will be held nearly steady in
    the 30s where the precip is ongoing, and many areas will continue to
    see snow during the day, possibly mixing with rain. Strong lapse
    rates under the low may allow enhanced precip rates and snow will be
    more likely during those periods. The event will transition to
    northwest flow late Friday across the NC/TN border area as PoPs
    continue to drop off east of there.

×
×
  • Create New...