Ensemble and deterministic model guidance is maintaining a consistent
significant "all hazards" winter storm signal that migrates eastward
across the central and eastern United States during the January 8th-10th
period. By 12Z on the 9th, a vertically stacked deep-layer low is
forecast by most guidance to be centered in the vicinity of southwestern
Missouri. This will aid in the development of a pronounced surface
cyclone and frontal wave advancing from Texas east across the Gulf Coast
states. In addition, wind fields will be strong at all levels and
upward vertical motion will be substantial. The operational GFS shows
relatively high values of boundary-layer theta-e spreading north across
the warm sector of the previously mentioned surface wave, and mid-level
lapse rates will be fairly steep (>7 C/km), thus there is the
potential for MLCAPE values to range from 1000-2000 J/kg, which is large
for January. However, it's uncertain whether the warm sector will
experience daytime surface insolation due to widespread low-level
cloudiness, and that will likely impact convective mode evolution and
possible tornado intensity. Nevertheless, current forecast wind fields
are exceptionally favorable for long-track violent tornadoes within the
previously mentioned surface warm sector (particularly far eastern Texas, southern Louisiana, southern Mississippi, and southern Alabama and adjacent Georgia and Florida panhandle), with mean 0-1 km streamwise
vorticity >0.02 s-1.
Farther north, a mainly sub-zero
deep-layer airmass will be in place from roughly the mid-Mississippi
Valley northeast across the Great Lakes. In addition, very strong upward
vertical motion is forecast to occur in the vicinity of a northeastward
migrating 700 mb low. Thus, ingredients will likely be favorable for a
band of heavy snowfall, the exact location obviously being a function of
the near-surface freezing line and mesoscale ascent focused near the
previously mentioned 700 mb low. Elsewhere in between the band of heavy
snow to the north and severe weather to the south, heavy rain, gusty
gradient winds, and perhaps embedded elevated thunderstorm activity will
be probable.
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Four-panel plot of 500 mb wind/heights valid 12Z 1/9/2024.
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Four-panel plot of 850 mb wind/heights/temperature valid 12Z 1/9/2024.
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GFS surface theta-e valid 09Z 1/9/2024. Note the northward flux of higher theta-e across southeast Mississippi and immediate surrounding region which is the approximate location of the surface warm sector.
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GFS model forecast sounding representing the severe storm/tornado environment valid 09Z 1/9/2024 in southeast Mississippi.
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GFS 6-hour snowfall accumulation valid 00Z 1/10/2024.
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GFS model forecast sounding representing the heavy snow environment located across Michigan valid 21Z 1/9/2024.
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