071
FXUS62 KGSP 040005
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
805 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 745 PM EDT: Still expect most of the area will be free of
measurable precipitation for most of the night. Ridge axis still
present over the SE Coast. Some disorganized bands of convection
continue west of the Appalachians in the more unstable area upstream
of the ridge, generally ahead of approaching shortwave. Little
change in the pattern or vertical profiles tonight, such that
scattered showers and perhaps a few t-storms are expected to
continue in the Smokies and Balsams, south to the Savannah
Valley. The current activity may wane diurnally before new
development occurs overnight. At this point, main impacts from
any storms are expected to be locally heavy rainfall. Outflow from
earlier storms left behind a nearly saturated PBL in some spots,
and some locally dense fog can`t be ruled out in such areas
overnight. However, cloud cover and dry profiles above the PBL
suggest this is a low confidence forecast and perhaps localized
issue. Will monitor temp trends thru the evening for possible
revision to patchy fog wording now included in the fcst. Southerly
flow is weak but should promote moisture advection into the lower
Piedmont, possibly bringing fog and low stratus to those areas
around dawn, but the higher cloud decks may keep that in check.

Possibly more notably, the weak moisture advection may
promote rapid development of convection around or after
daybreak Saturday. Coverage should then increase for that
reason and as forcing from the shortwave increases as the
day continues. 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 /00Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: -SHRA will approach KAVL and KAND this
evening but chance of impacts small enough no mention is made in
their TAFs. Multiple cloud decks above 070 will be seen tonight
largely as a result of either convective debris or clouds forced
by upstream shortwave. Sfc conditions will be moist tonight where
precip outflow occurred Fri aftn, but otherwise low levels remain
rather dry and extent of fog will be limited overnight especially
given cloud cover. Some instability will persist overnight
and new SHRA or even TSRA can`t be ruled out after midnight
near KAVL and the SC sites; S to SE PBL flow will serve as weak
forcing. Restrictions are likely to develop around/after 12z as
that flow replenishes sfc moisture and instability is realized,
even if only as stratocu initially. Deep convection is possible
as soon as mid-morning but more likely in the afternoon nearer
axis of synoptic shortwave. Hence precip impacts are handled with
PROB30s in the morning and TEMPO TSRA in the aftn. Any TSRA will
be capable of torrential rain and so did not shy away from IFR
vsby/cigs therein. Winds generally will remain southerly.

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...Wimberley