Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 291422
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1022 AM EDT Thu Sep 29 2016

.SYNOPSIS...
A stationary front will remain across the Midlands of South Carolina
and central North Carolina today. Meanwhile, an upper level low will
drop south into the Ohio Valley and linger there through the end of
the week.

&&

.NEAR TERM /THROUGH FRIDAY/...
As of 956a EDT Thursday:  Latest mesoanalysis has a triple-point low
just west of Charlotte, with a cold front as defined by surface
moisture gradient curving towards the northwest and southwest from
there, and a warm front towards the east.  Airmass east of the front
is somewhat unstable with CAPE currently around 1000 j/kg, and
likely to increase with afternoon heating.  With strong upper
system, deep layer shear along the cold front is around 50 kts, and
less ahead of the front.  The combination of shear and instability
is of some concern today over the extreme eastern parts of the CWA,
and western North Carolina, though the moist sector will continue to
edge eastward during the day.  While capping dosen`t look that
strong, main problem with any convection is that initiation may be
well east of the area as fronts progress during the day.
Mesoanalysis already shows line of best surface moisture convergence
well east of the area, well ahead of the dewpoint gradient. CAMS are
not at all enthusiastic about the prospects of strong storms this
afternoon, with both the NCAR and SPC SSEO having practically no
strong updrafts this afternoon in the CWA.  If any convection does
develop this afternoon, it is most likely along the warm front where
moisture convergence is slightly better, with fast northeast storm
motion and the prospect of severe events. SPC forecast has a
marginal risk for this afternoon over the eastern 6 counties of the
CWA.

Fog over eastern counties is gradually beginning to lift, and should
disperse over the next hour.

Temperatures will be trending cooler behind the front and down
towards seasonal normal for a change.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
As of 230 AM EDT Thursday...The large upper low will wobble/meander
over the Ohio Valley during the Short Term, keeping the CWFA under a
pronounced dry slot on its SW side. Given the trend in the upper low
track, thicknesses don`t fall as much as previous model runs had
suggested. So temps were nudged up slightly for Friday and Saturday.
Max temps will be about one or two categories above normal (except
slightly cooler in the western half of the NC mountains). Min temps
will be around normal. Dry conditions are expected and skies should
be mostly clear thru the period, but the stalled front will linger
just to our east on Friday.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
As of 300 AM EDT Thursday...An upper low should gradually fill and
open up into the westerlies somewhere over the Great Lakes sunday
and monday. From there model disagreement becomes quite large, with
how deep the northern stream trough digs in the Northeast states.
The 00Z ECMWF has a consolidated trough become progressive and exit
off the East Coast on Tuesday. The GFS and Canadian keep a large, yet
weak closed low, and drift it much more slowly. This also has an
impact on the possible track of T.C. Matthew. The GFS continues to
favor a quicker track out of the tropics and taking it somewhere
along the East Coast. While the ECMWF has the trough miss Matthew,
causing Matthew to only drift slowly north to the Bahamas at Day 10.
What this means for our forecast area is despite the large
disagreement in the upper level pattern, the sensible weather
forecast is similar. Basically, a large surface high will gradually
build in under the filling upper low across the Great Lakes, and
wedge down into the Carolinas by Monday thru Wednesday. Northeasterly
low-level flow should remain fairly dry (though cannot rule out some
stratus and a small chance for precip). I will keep a dry forecast
with temps remaining slightly above normal.

&&

.AVIATION /15Z THURSDAY THROUGH MONDAY/...
At KCLT: Widespread IFR conditions around the airfield and have held
onto this until 14z. Convection chances at the airfield are not high
enough to include in the TAF but will continue to reevaluate.
Southerly winds should pick up this afternoon to near 10kt, and
lower again later tonight.

Elsewhere: IFR conditions continue at KHKY but VFR at other sites.
Have included VCTS for KHKY briefly this afternoon, but no
convection expected at other sites. Wind trends similar in
speed/direction to KCLT as well, but with a wind shift late in the
period bringing winds around to the W and NW. Conditions favorable
tonight/early Friday morning for restrictions at KAVL/KHKY and have
trended this way in the TAF.

Outlook: Dry high pressure will build in slowly behind the front,
which should bring VFR conditions in most places through the
beginning of next week.

Confidence Table...

            14-20Z        20-02Z        02-08Z        08-12Z
KCLT       Med   77%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     Med   68%     Med   72%
KHKY       High  83%     High 100%     High  91%     High  85%
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 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...ARK
NEAR TERM...WJM
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...TDP



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