Here was GSPs update as of 6:40am
.NEAR TERM /THROUGH FRIDAY/...
As of 640 AM:
Water vapor imagery shows upper low centered near
Ark-La-Miss junction. Abundant
cirrus are spreading
downstream
within diffluent
flow, between the low and a low-
amplitude upper
ridge with its axis now over the
CWA. Continued eastward movement
of the
ridge axis should allow the
cirrus to fill in across the
CWA as both features migrate eastward. This
likely won`t occur
fast enough to keep today from being a fairly sunny day, if not
a tad cooler than yesterday.
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
timeframe. 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 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. This is
reflected in
QPF having trended slightly lower for the Piedmont. For
the higher terrain and Escarpment, however, now that more of
the
hi-res guidance encompasses the event,
QPF has increased in
response to the
upslope flow occurring ahead of the low. Precip
type still looks quite tricky. 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 freezing rain and/or sleet where the warm nose
(along with evaporative cooling diminishing it at least locally)
is present. Our confidence has sufficiently increased on the
northern
NC mountains and foothills meeting Winter Storm
Warning
criteria from snow alone that a portion of the old
Watch area has
been upgraded to
Warning. Rabun County, Georgia is forecast to have
accumulations right at the split of advisory/
warning, and with
WFO
Peachtree City having decided to go
Warning for their counties,
we upgraded Rabun to
Warning for simplicity of messaging. The
remaining
Watch areas 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 some support for precip across most of the area, but
particularly in 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.
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