305
FXUS62 KGSP 180533
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
133 AM EDT Thu Jul 18 2024

.SYNOPSIS...
A pattern change begins to evolve by Thursday, as a cold front
approaches from the northwest, then becomes stationary across our
region for several days. This will keep shower and thunderstorm
chances elevated through at least early next week.

&&

.NEAR TERM /THROUGH TODAY/...
As of 1238 AM EDT Thursday: Shower activity is continuing to
diminish as a stubborn cell persists over the Upstate. It`s
running out of steam and should be gone in the next hour or so,
but nothing severe. Satellite shows some scattered cloud debris
from storms earlier and are moving out of the area. Low level
stratus and fog is starting to creep into the mountains and is
expected to expand given the high dewpoints and light winds.
Other than that, no major changes to the forecast at this time.

Otherwise, upper troffing will linger to our north over the Great
Lakes while broad upper ridging persists to our west and to our
east. At the sfc, Canadian high pressure will persist to our NW
while the Bermuda High keeps moist, southerly low-lvl flow to our
south. Between these two highs, a weak frontal bndy will linger
over our region thru the near-term period helping to keep things
convectively active. Overnight/Thurs morning, conditions will
remain muggy with temps expected to remain a few degrees above
climatology with a decent chance for patchy fog to develop in the
mtn valleys and over area that received precip.

&&

.SHORT TERM /TONIGHT THROUGH SATURDAY/...
As of 100 PM Wednesday...A pattern change will begin the short range
as a strong Canadian high builds south and traps a frontal zone
against the Bermuda High. The flow around the subTrop ridge will
will allow for very good moist advect each day and cross sections
indicate high saturation thru the mid levels. The high cloud cover
and rather warm mid levels will limit sbCAPE potential each day as
sfc heating is curtailed a cat or so below normal, but diff heating
will allow for robust and longer lived cells. The various guidance
wavers on the exact placement of the sfc convg zone which will be
instrumental in the generation and amt of precip each day. But for
now, expect arnd an inch or so across localized areas FA-wide with
some potential for localized hydro issues depending on where the sfc
convg is enhanced by deeper convec due to mainly to diff heating.
Training cells with high rainfall rates will also be possible as the
mean steering flow aloft aligns with the stationary front thru the
period. Pops were maintained quite a bit abv normal each day with
noctural precip likely continuing to some degree each night.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 200 PM Wednesday...The ext range fcst remains active as the
latest guidance continues to show an activated stationary front
draped across the area. Decent agreement is seen in the mass fields
Sun thru Tue with the GOM wide open for efficient moisture flux each
day. This could be a period of increased hydro issues as antecedent
water level conds by that time may be quite elevated. A lot will
depend on the areas where the front situates as it wafts north and
south thru the period. High PoPs have been maintained thru the
period including abv normal PoPs during the overnight periods. Max
temps will likely be held below normal each day by a few degrees
while mins remain abv normal.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
At KCLT and elsewhere: VFR conditions for most sites to start and a
bumpy outlook for Thursday afternoon. A few lingering showers make
an exit this evening, leaving behind scattered low-level stratus in
areas that received rainfall earlier. First, areas in the mountains
and near KAVL show BR/FG seeping in. Confidence is moderate that
some sort of MVFR or even IFR vsby/cig could encroach on KAVL during
the overnight hours. A TEMPO for this from 09z-12z should suffice.
After daybreak, any lingering BR/FG should trickle out of the area
and all terminals remain at VFR through the rest of the TAF period,
with temporary restrictions during the afternoon hours. A cool front
approaches the area from the NW during the day and into the end of
the period. Second, this provides a moderate to high chance for
widespread TSRA at most terminals. TEMPOs for TSRA run from 19z-00z,
adjusted for specific sites with the mountain terminals having
earlier starts. KAND does not look as favorable for TSRA, so a
PROB30 for now, but will be re-evaluated next issuance. Lastly, the
front brings a wind shift from SW to N/NW. At KCLT, a NW wind is
likely to occur around 20z and shift NE by the end of the TAF
period. Wind speeds remain 5-10kts, with higher gusts possible
around any sites with thunderstorms.

Outlook: Scattered to numerous showers and thunderstorms each aftn/
evening thru the weekend. Morning fog/low stratus possible each day,
especially in the mtn valleys and over areas that received rainfall
from the previous day.

&&

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

&&

$$

SYNOPSIS...DEO
NEAR TERM...CP/JPT/PM
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...CP