Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 211434
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1034 AM EDT Fri Oct 21 2016
A cold front will cross the area this morning, ushering in a much
cooler and drier air mass for the weekend. Another cold front will
cross the region on Monday to reinforce the cooler temperatures.
After that front passes, high pressure will control our weather
through the middle of the week.
.NEAR TERM /THROUGH TONIGHT/...
As of 1030 am: The HRRR and NAM12 show a pressure kink in the lee of
the mtns, suggesting a mtn wave will remain through most of daylight
hours. Latest vis sate loop shows some wave clouds over the adjacent
foothills from Caldwell south to Polk Co. Given daytime mixing and
support from a 6-7 mb pressure gradient across the mtns, I have
highlighted the gust winds with a Wind Advisory across the east
facing slopes and adjacent NC foothills hills through 6 PM.
Grandfather Mtn., with a high elevation site, had a gust to 65mph
last observation. Otherwise, a shallow cloud deck exist across
middle and eastern KY/TN under deep dry air. Moist llvl NW flow
should support iso to sct showers along the TN/NC line through much
of the day. Otherwise, the region will remain dry and cool.
630 am update: the cold front has been steadily pushing eastward
across the NC mts early this morning accompanied by scattered rain
showers. Winds are just now starting to veer around to NWLY over
far western NC and increase in speed. Otherwise, the fcst is still
pretty much on track for the rest of today and tonight.
As of 320 am Friday: precip has been fairly slow making its way
into the CWFA early this morning. So far, it has been confined
to the NC/TENN border zones. Cloud cover should continue to
increase thru the morning hours as the cold front pushes farther
east. Overall, the most recent model guidance is trending drier
with this fropa. Likely to categorical POPs are confined to the
NC/TENN border counties with slight to solid chance elsewhere.
By 00z Saturday, drier air will be advecting into the CWFA behind
the front and POPs dwindle. Winds will be gusty today and are
expected to remain out of the NW and blustery, especially over
the higher terrain, well into Saturday. By midday today, wind gusts
are expected to reach the upper 30s kts across the high terrain
and east facing mtn slopes. The strongest gusts will likely occur in
the wake of the mtns, with the forecast development of a mtn wave.
Based on the latest model guidance, I`ve lowered wind speeds a bit
from the previous fcst. Thus a Wind Advisory should not be needed,
however we will monitor trends if the guidance trends upward.
Otherwise, temps will be considerably cooler today and tonight with
highs and lows nearly 20 degrees cooler than yesterday.
.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 230 AM EDT Friday...the balance of the weekend looks cool and
relatively quiet, although Saturday should be a bit breezy. Think
any lingering small chance of precip will not linger past the middle
part of Saturday morning...thereafter sky will gradually clear
across the NC mtns. The main story will be the high temps...which
will be on the order of 7-10 degrees below normal...under a mostly
sunny to sunny sky. This will finally make it really feel like
Autumn across the region at long last.
The axis of the upper ridge will remain to our west through the rest
of the weekend, which will keep the wrn Carolinas under a cool NW
flow, and will support surface high pressure moving across the
Southeast. This should yield another seasonally cool night on
Saturday night with temps getting cold enough for more widespread
frost across the mtns once the wind dies down toward daybreak on
Sunday. There could even be some patchy frost outside the mtns in
the normally cooler and sheltered spots. Temps will moderate quickly
on Sunday afternoon...returning to near normal under sunny sky...and
will not be nearly as cold Sunday night ahead of a reinforcing cold
front dropping down from the NW.
.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 245 AM EDT Friday...not much change in thinking with regard to
the medium range. A reinforcing cold front will move through early
Monday, bringing in another high pressure air mass from the NW. The
timing of the frontal passage will have a big affect on the high
temp fcst that day, which at present remains above normal. This
could easily get knocked back several degrees if the front arrives
Sunday night. Either way, temps will be closer to normal thru
mid-week as surface high pressure moves past to the north.
Confidence slowly erodes through the end of the week as the model
guidance shows the next system moving across the Gt Lakes on
Thursday and pushing a cold front toward our region. There remains
consensus among the operational model solutions that the front will
dry up before arrival, so the fcst was kept dry. This might be more
bad news for people that need rain, but is not atypical of October
across the region.
.AVIATION /15Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: the cold front continues to push eastward
across the NC mts early this morning. A band of light showers
remain confined to the higher terrain, but should spread into the
foothills over the next few hours. The only restrictions included
for TAF period are MVFR cigs at KAVL from roughly 13z thru late
tonight and the possibility of visby restrictions if the site receives
much precip. Persistent gusty winds along and behind the cold front
will be the main concern for the period. Winds will veer around to NWLY
later this morning and remain NWLY for for the remainder of the period.
Speeds will be highest over the higher terrain include KAVL with sustained
speeds in the 15 to 20kt range and gusts around 25kts with some brief
higher gusts likely. The other sites should see slightly weaker values.
Outlook: the pressure gradient will remain tight across the western
Carolinas through Saturday with breezy conditions expected. Dry high
pressure will then spread across the region on Sunday and linger into
early next week.
14-20Z 20-02Z 02-08Z 08-12Z
KCLT High 100% High 100% High 100% High 100%
KGSP High 100% High 100% High 100% High 100%
KAVL Med 78% High 100% High 100% High 100%
KHKY High 100% High 100% High 100% 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 scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:
NC...Wind Advisory until 6 PM EDT this evening for NCZ033-049-050-