Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 221802
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
102 PM EST Wed Feb 22 2017

.SYNOPSIS...
A weak frontal boundary passes east of our area today.
This will be followed by brief drying on Thursday before a more
significant cold front brings additional chances for rain and
thunderstorms late Friday or Saturday. Overall, daytime temperatures
will remain well above normal through the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
1230 PM EST update...The temp gradient is tightening up across the
Piedmont, as low stratus erodes from the SE. Areas to the north
remain socked in. So tried my best to reflect this in the hourly
temps for this afternoon. Areas in the northern NC foothills may end
up not reaching their forecast max temp, while areas to the south
may exeed them. Otherwise, little change was made with this update.

930 AM EST update...Still some patchy light rain and drizzle out
there on radar an in the obs, but overall precip has been decreasing
across the CWFA this morning as we lose upper support. In the low
levels, persistent SELY flow will keep plenty of low clouds around.
The latest VIS imagery shows the edge of the clouds roughly along
the GSP/CAE CWA border. If this can erode a little to the north, our
southern zones will have more insolation and hence, a bump up in max
temps. The NAM-based temp forecast looks too warm, but I did adjust
temps up slightly along the SE fringe. PoPs will continue to
decrease, but a lingering slight chc to low-end chance can be
expected near the Blue Ridge and to the NW closer to a northern
stream trough.

630 AM EST Update...weak upglide precip shield persists across the
wrn half of the FA this morning. Expect a gradual decrease in
coverage thru the remainder of the morning...with lingering isol
pockets of -ra/dz into the early afternoon. Temps and td/s remaining
rather steady state...with slow rises in hr/ly temps thru mid
morning.

A low-level wedge or insitu-wedge has become entrenched across the
FA this morning making for steady state conds wrt to temps/tds and
to some degree, winds. Atlantic moisture flux continues in the h92-
h85 layer and with negligible forcing aloft...very light -shra
continues to band over the area. The short range models generally
agree the escarpment area will be the best focusing zone for precip
chances thru the morning and the afternoon. This makes sense and
have adj official pops with a blend of CONSShort guidance. Max temps
shud range from arnd 60 mtn valleys to near 70 across the far srn
zones where the wedge bndry could see see more breaks in the
clouds...and perhaps a couple general tstms. Min temps tonight have
been adj up a little with continued llvl moisture flux and no good
mechanism to degrade or force the sfc wedge east. There will be
better ridging aloft pushing in from the SW however and this will
help reduce the pop potential...basically leaving slight to low end
chances along the escarpment area thru daybreak.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
As of 230 AM EST Wednesday: Surface high pressure will stretch from
the western Atlantic to the southern Appalachians on Thursday, with
any deeper moisture confined to the far southeast coastline near the
Florida system, or to the north along the warm front stretched out
across the Virginias. In between, a shortwave ridge will develop
over the forecast area Thursday through Friday as an upstream low
pressure system moves into the central plains. Deeper layer moisture
thus looks relatively sparse across the region in this late week
period. However, fairly abundant surface to 850 mb moisture will
continue along with light southerly flow to provide some measure of
upslope triggering. Instability looks fairly limited, but steady
dewpoint recovery could allow isolated to scattered diurnal showers
and embedded garden-variety thunderstorms to form. Expect max temps
15 degrees above climo on Thursday afternoon, and even warmer on
Friday ahead of the approaching cold front.

Moisture pooling along the cold front approaching from the west
should reach the southern Appalachians Friday night but then
gradually dry up as the boundary moves east through the piedmont by
midday Saturday. The southerly low-level jet ahead of this system
should be capped at about 35 to 40 kt as the pre-frontal convection
crosses the region early Saturday. The veered nature of the winds
will further deep layer shear. The best strong thunderstorm chances
for our area will be east of I-77 around 18Z, but better SBCAPE
values will remain off to the east across the NC central and eastern
piedmont through Saturday afternoon. Temperatures will tumble from
the west through the afternoon.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
As of 130 AM EST Wednesday:  Starting Saturday evening. The cold
front moves off the East Coast Saturday evening as some shallow
upslope moisture banks up against the Tennessee border with much
cooler air moving in with NW to NNW Flow. Only the GFS shows any
significant moisture with the NW Flow. The Canadian only has a hint
of any low level moisture while the EC has nothing but dry air with
the flow from the Great Lakes Region. Will not expect much to occur
and drying out before sunrise Sunday. Cooler surface high pressure
will be centered over Alabama to Tennessee around 18Z Sunday.

High pressure moves off the Carolina coast late Sunday night and
Monday with return flow southerly moisture starting across the SE
States. Warm front located over the Gulf States early Monday reaches
the Ohio Valley late Monday night. The cold front advances across
the Mississippi Valley on Wednesday bringing showers and perhaps
storms to our area late Wed night which is after the end of the
current forecast. As the warm front moves north, a slug of moisture
crosses the southern Appalachians late Monday night into early
Tuesday. That will be the best chance of any rainfall until the
prefrontal rain ahead of the cold front reaches our area on
Wednesday.

Temperatures will be near normal Sunday rising to around 5 degrees
above on Monday rising to 10 to 12 degrees above normal Tuesday.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
At KCLT...The wedge boundary can be seen just SE of the terminal at
time of 18z TAF issuance. The consensus of the guidance is that the
boundary will probably lift just north of the airport, and allow
winds to turn out of the ESE by late afternoon. The boundary layer
south of the front will warm enough to lift the cloud bases to
around 3500 ft by peak heating. But until then, there is a small
chance of an MVFR cig between 1500-3000 ft. After sunset, cigs are
expected to lower into at least the low MVFR range, with fog also
possible toward daybreak. Conditions are expected to start improving
late Thursday morning to VFR by the end of the 18z TAF period.

Elsewhere: IFR/MVFR stratus is slowly lifting and eroding, with VFR
conditions possible, at least in the Upstate sites, for a few hours
late aftn into early evening. A few light showers may develop within
the persistent moist SELY flow, but too low of coverage to warrant a
mention in any of the TAFs at this time. Cigs will lower and likely
drop to LIFR overnight with areas of fog also possible. Conditions
should start to improve late Thursday morning, but may not get to
VFR until after 18z. Winds will be light thru the period, generally
favoring a NE direction (except SE at KAVL).

Outlook: Moist southerly to easterly low-level flow will persist
across the area until a cold front pushes thru on Saturday. This
will keep high chances of morning stratus and possibly fog each day
thru Saturday morning.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       Med   75%     Med   69%     Med   68%     Med   64%
KGSP       Med   60%     Low   56%     Med   67%     Med   70%
KAVL       Low   41%     Med   70%     High  81%     High  81%
KHKY       Low   54%     Med   64%     Med   66%     Med   74%
KGMU       Med   60%     Low   58%     Med   67%     Low   59%
KAND       Med   79%     Med   66%     Med   70%     Low   59%

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...DEO
NEAR TERM...ARK/SBK
SHORT TERM...HG
LONG TERM...DEO
AVIATION...ARK



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