Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 190227

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1027 PM EDT Mon Sep 18 2017

High pressure will remain in control of the weather pattern across
northeast Georgia and the western Carolinas through much of the
week, leading to above normal temperatures and generally below
normal precipitation chances. Meanwhile, Hurricane Jose will remain
over the western Atlantic with no impacts expected across the
southern Appalachians and surrounding areas.


As of 1025 PM: A narrow ridge will remain over the southern
Appalachians and vicinity through Tuesday. This will partially be
reinforced by Hurricane Jose as it continues to move north over the
open Atlantic, not far off the NC/VA coast. Another round of fog/low
stratus is expected to begin developing after midnight, with
observational and numerical guidance trends indicating that coverage
of the goo should be similar, if not a bit less than on Monday
morning. Mins will be in the mid 50s mountain valleys and lower to
mid 60s over most of the Piedmont.

The ridge will weaken a bit Tuesday as a shortwave moves into the
mid-upper Ohio Valley. With reduced subsidence, thermo profiles from
the models indicate deep convection is a bit more likely throughout
the CWFA. That said, with no significant forcing mechanisms, the
models do not spit out much QPF over the area overall, keeping
what they do produce over the mountains/foothills; PoPs reflect
this. Max temps will be a degree or so warmer than today, 1 to 2
categories above climo.


As of 230 PM EDT Monday: Guidance in good agreement with a weak
upper trough developing over Carolinas through the Short Range. A
series of weak short waves will rotate through the trough and across
the area Wednesday and Thursday. At the surface, a weak lee trough
develops and remains in place both days. The atmosphere becomes
unstable as mid level lapse rates steepen. However, instability
remains weak with LFC levels staying relatively high as low level
moisture increases but not significantly. Therefore, still expect
the diurnal convection with the best chances to be across the
mountains where the instability is more likely to be tapped with
lesser chances elsewhere. Thursday has a better overall chance than
Wednesday. Highs will be nearly steady 5 to 10 degrees above normal
while lows 5 degrees above normal Wednesday morning rise a couple of
degrees Thursday morning.


There has been very little change to the forecasted pattern
and sensible weather since the overnight package which means we
continue to expect very pleasant conditions across the area through
at least early next week.  By Friday the region is forecasted to
be within a region of weak upper-level troughiness that extends
from the central Gulf Coast towards the closed upper-level low
associated with TC Jose off the New England coast.  With the spine
of the surface high pressure ridge running down the Appalachians,
a light easterly (upslope) flow combined with support from the
upper-level weakness will result in a slight chance for afternoon
showers across the favorable mountain slopes through Saturday.
Temperatures will remain a few degrees above normal.

Towards the end of the weekend into early next week, guidance is
still suggesting Hurricane Maria will move NW and then due N across
the far Western Atlantic underneath a sprawling upper-level ridge
over the eastern ConUS.  With the upper-level ridge overhead and
Maria off to our SE, the region will experience subsident/clearing
skies, near zero precip chances, and light NEly flow. While
temperatures will remain slightly above normal, dewpoints will
pleasantly drop into lower to middle 50s across the mountains with
upper 50s and lower 60s east of the mountains.


At KCLT and Elsewhere: More or less status quo on the aviation front
over the next 24 hours, with early morning valley fog/low stratus
potential being the primary concern. Observational and statistical
guidance trends suggest Tue morning will see similar timing and
magnitude of flight restrictions in the mtn valleys as on Monday
morning, when KAVL remained VFR. Based upon climatology, and
occurrence of restrictions in recent mornings, do not feel
comfortable with a VFR forecast at KAVL, but restrictions are
limited to MVFR conditions within a tempo from 10-12Z. Elsewhere,
other than a tempo for MVFR at KHKY, a VFR forecast will be carried,
although cannot completely rule out a brief period of MVFR visby at
the other sites.

Outlook: Isolated, mainly high terrain diurnal showers will
remain possible through early week, with better mountain shower
coverage building Wednesday through Friday. Morning mountain valley
fog/stratus are also expected each day.

Confidence Table...

            02-08Z        08-14Z        14-20Z        20-00Z
KCLT       High 100%     High 100%     High  98%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High  91%     High 100%     High 100%
KHKY       High 100%     High  95%     High  92%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High  95%     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 and ensemble forecasts
are available at the following link:




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