277
FXUS62 KGSP 032145
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
545 PM EDT Fri May 3 2024

.SYNOPSIS...
Dry and warm high pressure moves off the Carolina coast as a
front approaches from the west then stalls over our region for
the weekend. This front will result in periodic thunderstorms
and showers starting today and lingering through the weekend. A
general summertime pattern sets up early next week, which will
likely support scattered thunderstorm development each afternoon.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 520 PM EDT: Major change at this update is to reflect precip
coverage in the next few hours, generally supporting lower PoP for
most of the area. Convection has been on a downward trend in the
last hour or so, along the persistent axis near I-77, seemingly
being outflow dominant without enough instability or forcing to
foster new development. Water vapor imagery and RAP analysis depict
weak vort max over the CWA, which maintains some deeper cu west
of that activity. This activity will move into the rain-cooled
region and likely won`t amount to much more, but remains worthy
of an isolated or widely scattered shower mention. In the more
unstable area from the Savannah Valley, Smokies and westward, area
of rain with embedded storms will linger, but diminish nocturnally
to some degree. At this point, main impacts are expected to be
locally heavy rainfall, with whatever severe threat we had having
peaked. The outflow wreaked havoc on our temp and dewpoint grids
thru the evening; it is always tricky to get the grids back on
track when guidance reflects current conditions as poorly as it
did at the top of the hour, but we have done the best we could
using HRRR and short-term consensus blend to make believable
trends for the evening. Confidence is too low to say exactly how,
but the increased sfc moisture from the activity could enhance
low ceiling and fog potential in some areas toward dawn. For now
we retain patchy fog wording in most zones.

CAM guidance still shows an uptick in shower activity overnight
in the continued moist and weakly forced atmos, with continuing
southerly upslope flow. Coverage then continues to pick up through
the day Saturday as forcing becomes better.  Instability and shear
will remain on the weak side, while forecast profiles show an even
more saturated atmosphere. This suggests and even less chance
of strong to severe storms, with a slight uptick in heavy rain
potential. That said, the overall flood risk remains low given the
relatively dry antecedent conditions. Highs will be near normal
due to clouds and precipitation.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 240 PM EDT Friday: The rest of the weekend looks active right
into the first part of next week. A baggy upper trof overhead
on Saturday night slowly lifts northeast with a short wave
passage, and this bit of lingering forcing will be able to keep
shower/thunderstorm activity on a slow wane into the early morning
hours. Guidance suggests that it will never die off entirely,
so the fcst retains some fairly high precip probs. That sets the
stage for Sunday. Models show less forcing, but an uptick in the
available buoyancy in the afternoon. That should make for a more
thermodynamically-driven day, with better than climo coverage
of showers and storms. Forecast soundings off the NAM show some
pulse-severe wind damage potential with mid-level dry air and
a shallow inverted-V, so it would not come as a surprise if it
was a busier day than Saturday. A stronger short wave lifting
northeast over the TN/OH Valley regions on Monday will continue to
support diurnally-enhanced convection, so we continue with above
climo precip probs. Temps look to be on the order of five degrees
above normal.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 143 PM EDT Friday: The bulk of the medium range looks like a
summer preview. After a baggy upper trof moves past Monday night,
we should spend the remaining week underneath a low amplitude,
relatively fast, WSW flow aloft. Within this flow, the model
guidance shows a steady train of short waves moving through, mostly
around peak heating each day, that will enhance our convective
coverage each afternoon/evening. Overall, the air mass shows
little change from one day to the next, as a wavy surface front
will be strung out to our north in the WSW flow. Buoyancy will be
modest and shear will be light, which suggests that chances for
severe storms will be relatively low, but in such a pattern we
eventually seem to manage to crank out a few pulse severe storms
each day. Precip will be spotty and showery, which keeps the heavy
rain threat at bay, but eventually there could be a few spots that
start to see an increased risk of flash flooding, especially if a
more coherent, stronger short wave comes along, such as what the
GFS shows next Friday. Lots of uncertainty, though. Temps will
remain in that 5-10 degree above normal range for most days,
perhaps on the high side of that either Wednesday or Thursday,
which one of those days might get a break in the wave train and
thus reduced shower coverage and higher temps.

&&

.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: Convective activity diminishes somewhat
this evening but returns overnight. Have PROB30s in place for
that. Cig and vsby restrictions develop overnight as well, so
have MVFR to MVFR before 12Z and IFR after 12Z. Light and
variable wind expected overnight with S to SE wind for all but
KAND, where it will be ENE, Saturday.

Outlook: Enhanced moisture will combine with a weak/stalled front
through early next week, resulting in a period of active/mainly
diurnal convective weather each day. There will also be the
potential for restrictions associated with widespread fog and/or low
clouds each morning.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...DEO
NEAR TERM...RWH/Wimberley
SHORT TERM...PM
LONG TERM...PM
AVIATION...RWH