Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
FXUS62 KGSP 221944

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

Brief drying develops on Thursday before a significant cold front
brings chances for rain and thunderstorms Friday night and Saturday.
Overall, daytime temperatures will remain well above normal through
Saturday, with a return to normal for Sunday. Above normal
temperatures and chances for rain return for early next week.


As of 230 PM EST...An upper low will continue to drift SEWD over FL
tonight thru thursday, while an upper ridge builds back in across
the Southeast states. At 850 mb, the circulation around the upper
low will keep a persistent SELY Atlantic fetch into the CWFA. This
will keep plenty of low clouds and fog for the overnight thru
Thursday morning. Forcing remains weak, so only spotty light showers
and patchy sprinkles/drizzle is expected, and mainly favoring the
SELY upslope areas of the Blue Ridge. That`s where PoPs will be
highest (in the chance range, slight chance or less elsewhere).
Temps will only cool slightly under the clouds, into the upper 40s
to mid-50s.

During the day on Thursday, expect the low clouds and fog to
eventually lift and scatter out, revealing some sunshine, especially
in the southern Piedmont. Lingering surface high pressure will nose
in from the east, but temps should be able to warm into the 70s
across the entire Piedmont with nothing to lock in any remaining
cold pool.


As of 240 PM EST Wednesday: Short wave ridging builds over the area
Friday before an upper low developing over the Northern Plains moves
east across the Great Lakes on Saturday dragging a trailing trough
across our area. Southerly low level flow remains over our area
Friday as high pressure moves east and a strengthening cold front
moves into the MS valley. There will be enough low level moisture to
combine with the flow for some isolated showers along the Blue Ridge
Thursday night/Friday morning and scattered showers and isolated
thunderstorms on Friday afternoon. Lows will be 15 to 20 degrees
above normal with highs around 20 degrees above normal but still a
couple of degrees below record levels.

Winds pick up and moisture increases Friday night as the cold front
to our west moves into the mountains toward daybreak. However, deep
moisture is shunted off to the north. The best forcing is also to
our north where the best short wave energy moves through the trough.
Despite the guidance showing some elevated instability ahead of the
front, the NAM and GFS forecast soundings show quite a cap in place
for all but maybe the NC Mountains and I-40 corridor. The best
SBCAPE develops during the afternoon east of our area as the front
quickly moves across the area. There will be quite a bit of bulk
shear and helicity ahead of the front. However, the best instability
and shear do not overlap over our CWFA. Therefore, the chance of any
severe storms is very low, but we will need to keep an eye on this
system as it approaches. There will be some NW flow snow showers
along the TN border in the lingering moisture and developing NW flow
behind the departing front. However, any accums look to be below
advisory level for now. Finally, winds will increase and become
quite gusty across the high elevations ahead of the front Friday
night then all areas on Saturday behind the front. Winds linger
across the high elevations Saturday night. Lows Friday night around
20 degrees above normal fall to near normal Saturday night. Highs
Saturday will be around 10 degrees above normal across the
mountains, and could be earlier in the day than normal, and 15 to 20
degrees above normal elsewhere.


As of 2 PM EST Wednesday...starting to wonder if winter is really
over. The upper pattern looks like it should remain progressive
through the medium range with all the colder air kept well to our
north. In the wake of the Saturday system, expect Sunday will be the
only seasonal day in the first half of next week. We should be under
a flat ridge that supports high pressure at the surface, which
should keep temps merely five degrees above normal. After the
surface high moves off the coast Sunday night, our weather should
get more active through the rest of the period. A short wave moving
over the Srn Plains Sunday night will organize surface low pressure
that moves up the OH valley on Monday. Model guidance is not in very
good agreement as to how organized or deep the low will be, but
there is some agreement that a surface front will lay down across
the area Monday and Monday night. Precip prob slowly ramps up into
the chance range over the mtns and a slight chance east of the mtns.
The models suggest a lull in the action Tuesday morning, so will try
to indicate a break in the low-end precip chance at that time. There
is also some agreement that the old boundary will reactivate Tuesday
night as another low organizes over the Plains. Altho this low will
track over the Midwest/Gt Lakes, it should push a cold front toward
the region on Wednesday. That should bring a chance of precip across
the whole fcst area. Will hold back with including any likely precip
prob due to lack of confidence out on day 7. Temps will gradually
rise through mid-week, getting back up into the well above normal
range for Wednesday.


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...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       Med   77%     Med   71%     Med   69%     Med   65%
KGSP       Med   60%     Med   60%     Med   67%     Med   66%
KAVL       Low   36%     Med   71%     Med   79%     Med   79%
KHKY       Low   51%     Med   64%     Med   66%     Med   77%
KGMU       Med   60%     Med   60%     Med   67%     Low   53%
KAND       High  80%     Med   63%     Med   68%     Low   57%

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:




AVIATION...ARK is the U.S. government's official web portal to all federal, state and local government web resources and services.