Area Forecast Discussion
Issued by NWS Greer, SC

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795
FXUS62 KGSP 302208
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
608 PM EDT MON MAY 30 2016

.SYNOPSIS...
The remnants of tropical system Bonnie will slowly lift northeast
along the Carolina Coast over the next couple of days. Moisture will
increase ahead of a cold front approaching from the northwest
Thursday and Friday. The front will move through the region on
Saturday but likely stall nearby over the weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 6 pm, widely scattered showers and thunderstorms continue
across the upper Savannah River Valley. I will update the forecast
to increase PoPs along the SC/GA line. Otherwise, the current
forecast appears in good shape.

As of 130 PM: Cumulus have grown over the mountains in the past
90 minutes or so, and showers are now seen on radar over SW NC
and on the Blue Ridge north of I-40. This appears to agree with
most of the meso guidance, and following them, the expectation
remains that this activity will gradually propagate southeastward
into the upper Piedmont. Further upstream, discrete convection is
lining up along a weak boundary near the KY/WV/VA borders. While
these cells will gradually spread south, it appears unlikely they
will reach the NC Mtns before late afternoon, if they survive that
long. We`ll keep an eye on that activity over the next few hrs.

The remnants of former tropical cyclone Bonnie will remain invof
the "Grand Strand" into Tuesday morning, before beginning a gradual
northeastward movement by the end of the day. With the low remaining
on our periphery, northeasterly low level flow will continue over
our CWFA. This will provide enhanced moisture as well as very weak
convergence, which could allow some shower activity to persist
overnight. Plus, morning stratus is expected to develop over the
eastern third of the CWFA. Elsewhere, only cirrus are expected to
be seen overnight, and with winds remaining light, patchy fog is
expected to develop in some areas. Notable visibility restrictions
currently are not anticipated. Mins tonight will be a category or
two above normal.

Despite Bonnie and the boundary sagging southward from KY/VA,
diurnally driven instability will be the main justification for
PoPs. Meso models (namely 4km NAM Nest and the NCEP HiRes WRFs)
depict most activity firing over the higher terrain Tue aftn,
though uncapped profiles are seen over the most of the Piedmont
as well. Hence a mentionable PoP extends throughout the area Tue,
with the best chances along the Blue Ridge once again. Very weak
shear will lead to discrete convection, producing mainly isolated
heavy rainfall and perhaps a few strong gusts.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 215 PM Monday: The remnant Bonnie circulation will lift slowly
northeast along the North Carolina coast Wednesday and Thursday.
Warm and humid air will remain in its wake across the western
Carolinas and northeast Georgia. Scattered, mainly diurnal
convection is expected Wednesday, with best coverage favoring the
mountains. Coverage increases on Thursday with the trend remaining
mainly diurnal and best coverage across the mountains. although
moderate instability is forecast both days, there is very little
shear. This along with moist vertical profiles should limit the
severe thunderstorm potential. However, he light steering flow up
the column will create a heavy rain threat with any thunderstorms
that form. Highs will be up to 5 degrees above normal with lows up
to 10 degrees above normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 215 PM EDT Monday: the medium range fcst picks up at 00z on
Friday with upper ridging off to our east and a southern stream
upper low beginning to cut off over Texas. Over the next couple of
days, this low remains nearly stationary as steep upper ridging
builds over the Western CONUS. By the latter half of the weekend, a
broad upper trof begins to dig down over the Great Lakes as
impressive ridging persists to the west.

At the sfc, a weakly forced cold front will be moving into the CWFA
by early Friday as the remnants of Bonnie finally dissipate off the
NC Coast. The overall sfc pattern is expected to remain weakly
forced with the cold front stalling out over the region late Friday
and Sat. As we approach the end of the period another cold front
will likely develop and move thru the fcst area sometime late Sunday
into Monday with significant differences still apparent between the
long range models. As for the sensible fcst, no major changes were
needed with solid to low end likely chances for numerous showers and
ts each day/evening. Some drying is expected by the end of the
period early next week, however it is not clear exactly how quickly
that second front will move thru the area. Temps will start out just
above climatology and cool a few degrees on Sunday and Monday.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
At KCLT: Enhanced moisture and convergence on the western periphery
of former Tropical Storm Bonnie will maintain a moderately dense
Cu field over the area thru sunset. A chance of SHRA/TSRA exists,
but operational impact is too unlikely to warrant a mention. Winds
will remain generally NE, in fact mostly NNE this aftn. Moist flow
from the Coastal Plain is expected to bring in IFR stratus cigs
early Tue AM. This will take until late morning to dissipate,
likely being replaced quickly by low VFR Cu similar to how cigs
evolved Mon mrng.

Elsewhere: Primary impacts for the aftn will be from TSRA, which
will develop near the Blue Ridge and propagate S and SE. TEMPOs are
included to cover the threat, except at KAND where the chance is
lower. Chances for impactful precip diminish by sunset, though a few
showers may linger over the I-77 corridor and vicinity (including
KHKY) thru much of tonight. The low stratus that is expected
to creep into the NC Piedmont early Tue mrng is not expected to
bring a cig even as far west as KHKY, though some other parts of
the area (namely KAVL/KAND) will see patchy fog near dawn. Winds
will prevail NE, except NW at KAVL due to valley effects.

Outlook: Bonnie`s remnant low is expected to move very slowly
up the coastal Carolinas over the next several days, maintaining
increased precip and morning stratus chances at KCLT. Otherwise,
patchy fog chances continue at KAVL each morning, with scattered
afternoon/evening SHRA/TSRA increasing in coverage throughout
during the week.

Confidence Table...

            22-04Z        04-10Z        10-16Z        16-18Z
KCLT       High 100%     High 100%     Med   72%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High  95%     High 100%
KHKY       High 100%     High 100%     High  86%     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 schedule TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:

www.weather.gov/gsp/aviation

&&

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

&&

$$
SYNOPSIS...JPT
NEAR TERM...NED/Wimberley
SHORT TERM...RWH
LONG TERM...JPT
AVIATION...Wimberley



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