Otherwise, a complex split-
flow upper
lvl pattern will gradually
evolve thru the near-term period. By the end of the period early
Monday, the southernmost upper low/
trof will phase with a more
northern
trof and move across our area. At the surface, broad and
relatively weak high pressure will linger over the Southeast for
most of today/tonight with a complex
sfc low developing over the
Carolinas as the period ends early Monday. As this occurs, a broad
region of deeper
moisture will spread over the
CWFA from the west
and south, yet the more favorable upper-
lvl forcing/support will
remain to our southeast. As for the sensible
fcst, cloud cover will
gradually increase from the SW later this
aftn and evening. With the
weak forcing,
QPF amounts should be minimal with the bulk of it
expected during the last 6
hrs or so of the period early Monday.
Based on the latest temperature profiles, only the higher terrain is
expected to be cold enough to see any appreciable snow, with
accums
less than an inch anticipated for most locations. The Foothills
could see some rain/snow mix during the last few hours of the period
as their temperatures cool, but it`s doubtful that wetbulb temps
will be cold enough to support all snow there. Otherwise, the rest
of the
CWFA will just see light rain showers.
For the Piedmont, most of the guidance sources now show precip
developing in the late morning to mid-afternoon timeframe. This
appears to result initially from the dynamic forcing, but a small
amount of
instability (most
likely well below 100
J/kg) is expected,
owing to strong midlevel lapse rates. This could keep precip going
for a time after the
shortwave axis passes. With the downsloping,
precip is expected to taper off during the morning in the foothills
and portions of the NW
NC Piedmont, though a small chance remains
warranted most of the remainder of the day in the still-lower
elevations, including the I-85 corridor. Temps look
likely to break
into the 50s despite cloud cover. Most if not all of this light
precip thus should be rain. However, the low levels are expected to
be pretty dry, making wet-bulb temp profiles supportive of low snow
levels--if the precip does not evaporate/sublimate entirely above the
surface. This forecaster would be willing to bet that we get at least
a few reports of flakes mixing in with light rain, especially if
precip hangs on until later in the afternoon when the
CAA sets in.
It`s a tricky situation; model soundings and p-type output suggest
the rain
likely will end just as low-level temps become supportive of
snow. Some decent wind gusts (perhaps 20-30 mph) could occur at high
elevations in the NW
flow, but also in the vicinity of any convective
showers Monday afternoon.