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Stovepipe

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    February/March 2021 - Frigid or Flop? Pattern/Longterm Forecast Thread.

    in Tennessee Valley

    Posted

    23 minutes ago, Carvers Gap said:

    From the MRX evening disco...Time to put the bat signal up for @Math/Met.  Good set-up? 

      

    
The aforementioned S Plains mid/upper shortwave will eject ENE
across the MS Valley into the TN and OH Valleys during this period
while becoming slightly negatively tilted. This along with a 150+ kt
upper jet will deepen the surface low as it lifts through the
vicinity of the Appalachians and eastern OH Valley. Forcing from the
strong upper jet will lead to a strong, southerly low-level jet Wed
night that will pump strong moisture transport into the S
Appalachians region. This strong moisture transport, isentropic
upglide, and additional dynamic forcing as the surface low
approaches will lead to widespread precip developing north of an
advancing warm front Wed night. Deterministic and ensemble guidance
still differ regarding the exact track of the low and resultant
thermal fields (as is usually the case in the winter), so precip
type at the onset Wed night is low confidence. The GFS is the
coldest solution, the NAM is the warmest, and the GEFS/Euro/CMC
ensemble means are in the middle. Leaned heavily on the ensemble
means and NBM for temps and precip type Wed night into Thurs morning
which suggests a period of snow, sleet, and freezing rain possible
from the Plateau through the N Valley into SW VA, so generally N of
I-40 and W of I-81. Forecast soundings support this idea with a
gradually descending warm nose as the warm front lifts N, but as
mentioned, precip type and location confidence is low. This will be
fine tuned as new guidance arrives over the next 48 hours. One thing
that is certain is that a high end mountain wave will occur across
the E TN mountains and foothills Wed night through Thurs morning
since the low-level jet will be favorably oriented perpendicular to
the terrain, it will be a very strong low-level jet of 60-80 kts,
and an inversion will be in place below 850 mb leading to ducting
values over 20. This will likely lead to 80+ mph gusts downsloping
into the foothills such as Camp Creek. As the mid/upper shortwave
and surface low lift NE Thurs, a strong cold front will cross the
region. We could see a dry slot part of the morning, but expect
precip to quickly return as the strong upper jet maintains strong
frontogenetic forcing ahead of the cold front with continued strong
low-level moisture transport ahead of the boundary. PWATS will be
above the 90th percentile with some elevated instability, so periods
of heavy rain are possible. Warmer air advecting in ahead of the
front will allow any mixed precip in northern areas Thurs morning to
quickly change to rain for the afternoon.

    kASDXHf.jpg

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    • Haha 1

    Presidents Day Snowstorm OBS Thread 2/15/21

    in Tennessee Valley

    Posted

    This Memphis cam in particular is fun to watch.  Cars are having a hard time getting up this hill.  I watched the one in the screeshot slide backwards before giving it another attempt.  Now several vehicles are stuck on the side of the road.  The wind is blowing hard with huge flakes falling.  Wish I could be there.

    TQraLME.jpg

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