Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 031513
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1113 AM EDT Wed Jun 3 2020

.SYNOPSIS...
Shower and thunderstorm chances will increase Thursday and Friday
ahead of an approaching cold front, with the front likely crossing
the region on Saturday. The front may stall near the southern part
of the area for the latter half of the weekend into early next week,
keeping isolated to scattered showers and thunderstorms in the
forecast.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 11:11 AM...Forecast is in good shape, so no changes will
be made.

Upper ridging and stg downward motion will weaken this afternoon
as a broad h5 trof advances over TN. Heights will fall and a weak
sfc trof will dominate the llvl pattern thru the period. There
will a degree of GOM moisture adv arnd the Atl ridge, however,
and this shud be enuf to instigate -shra/tstms across the NC
mtns during the afternoon and evening. The models still have
varying ideas as to the amt of sfc-based instability and overall
coverage. So...continued to advertise low-end PoPs. The NAM as usual
has abt twice as much sbCAPE as the GFS and believe this is overdone
as mlvl LRs don/t steepen until the overnight period. Still, some
of these pulse storms could become stg and produce hail and stg
outflow winds. Max temps will reach abt 5 degrees abv normal in
good insol and continued sw/ly flow. Mins will also be held abv
normal levels overnight.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 325 am Wednesday: The synoptic pattern will become
increasingly favorable for convective activity across the Southeast
during the short term, as a weakness develops in the subtropical
ridge from the TN Valley into the Deep South. Meanwhile, short term
models depict a plume of relatively steep mid-level lapse rates
(6.5-7 C/km) lingering across the forecast area Thu afternoon. With
low level moisture still on the increase, CAPE of at least 2500-3000
J/kg appears likely during peak heating. The result should be
numerous coverage of convection over the mtns, with SW steering flow
carrying activity into the NC foothills and western Piedmont later
in the afternoon into the evening. Robust instability and moderate
downdraft CAPE will allow for at least a few pulse severe storms,
although low level shear of ~15 kts may allow for some small scale
clustering along cold pools, which would pose a slightly higher
threat of downburst winds. Although cell movement will likely be in
the 10-15 kts range, locally excessive rainfall will be possible in
locations where cells are able to train.

Increasing deep layer moisture Friday will result in weak mid-level
lapse rates/slightly weaker afternoon instability, but PWATs
increasing above 1.5 should make up for the relative weaker
instability. Thus, more of the same is expected for Friday
afternoon/evening, with perhaps slightly higher chances for locally
excessive rainfall, and slightly lower chances for severe
convection. Temps will be a category above climo through the
period.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 335 am Wednesday: With an area of height falls passing over
the northeast Conus early in the medium range, a frontal boundary,
along with pre-frontal/lee surface trough is expected to impact the
forecast area Saturday...likely resulting in another round of at
least scattered, mainly diurnal convection. Lower theta-e air looks
to filter into the area for early next week in the wake of the
boundary, but sufficient moisture/weak instability may linger to
warrant inclusion of token small pops for mainly diurnal showers and
a few storms Sunday and Monday. The expectation of moisture
increasing from the west warrants slightly higher pops for Tuesday.
Max temps will be close to normal, and mins about a category above
climo through the period.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Minimal chance of flight restrictions thru the
TAF period across all sites. A sfc trof will remain over the area
while weak moist adv commences from the southwest. This will enable
fair-wx Cu in the afternoon. Low-end gusts are probable as well in a
well mixed BL. At KAVL...there could be isol afternoon -shra/tstms,
yet the coverage looks too limited for a 06z TAF mention. No good
chance of fg/br outside of mtn valleys this morning, where winds
have become calm and sfc tdd/s are running rather low.

Outlook: Increasing heat and humidity will likely result in a return
of afternoon/evening convection by the end of the week. Otherwise,
VFR conditions each day, and mountain valley fog possible each
night.

Confidence Table...

            15-21Z        21-03Z        03-09Z        09-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High  81%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High 100%     High 100%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:

www.weather.gov/gsp/aviation

&&

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

&&

$$
SYNOPSIS...HG
NEAR TERM...PM/SBK
SHORT TERM...JDL
LONG TERM...JDL
AVIATION...SBK



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