Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 220747
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
347 AM EDT Wed Mar 22 2017
Cooler air will returns to the area behind a departing cold front.
The cooler and drier air mass remains through the end of the work
week. Another cold front moves across the area Monday bringing rain
back to the forecast.
.NEAR TERM /THROUGH TONIGHT/...
As of 300 AM EDT Wednesday...A deep upper trough will exit off the
East Coast today, with an upper ridge building across the Plains. A
large area of Canadian high pressure will build in across the Great
Lakes to the Carolinas under the NWLY flow aloft. The high should
push a frontal boundary well south of the area, allowing for mostly
sunny skies today. The 850 mb CAA will subside, but I do expect a
few marginal NELY wind gusts today across the Piedmont, with more
frequent gusts in the mountains. Temps will still manage to get into
the mid to upper 60s this afternoon, which is near normal. Temps may
be slightly above normal in the southern tier, which will have the
warmest start to the day.
Tonight, the axis of the surface high will settle across the
Piedmont, with skies remaining mostly clear. A consensus of the
guidance brings temps into the lower 30s across the northern
foothills and NW piedmont of NC tonight, resulting in a light
freeze. Lingering winds and dry air seems to preclude frost
development. So will go with a Freeze Warning for the I-40 corridor
east of the mountains.
.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 220 AM EDT Wednesday: Guidance in good agreement through the
short range. Upper ridge builds into the area through Friday then
the axis begins sliding off shore Friday night. Surface high
pressure builds into the area Thursday in a cold air damming pattern
and remains in place Thursday night. The center of the high slides
off shore Friday but the ridging remains in place even as it takes
on more of and east-west orientation through Friday night.
The guidance is also now in agreement on a dry forecast through
Friday. In fact, there is also less in the way of clouds through
then as well. Therefore, expect highs Thursday to be slightly warmer
than previously forecast, but still quite around 10 degrees below
normal given the air mass and low thickness values. Lows Thursday
night will be a few degrees below normal, keeping frost concerns
going for the NC Foothills and Piedmont and eastern Upstate. Highs
Friday will be near to slightly below normal.
Low level moisture and upslope flow develops on Friday night and may
lead to isolated showers near the Blue Ridge over the NC/SC/GA
borders. Lows will be 5 to 10 degrees above normal.
.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 340 AM EDT Wednesday: Guidance in good agreement through the
medium range. The first of a series of upper lows moves from the mid
MS valley Saturday, to between the Great Lakes and OH valley Sunday,
then into New England Monday. A second upper low over the southern
plains Monday opens up and crosses the area as a weakening short
wave on Tuesday.
At the sfc, deep moisture increases from west to east Saturday and
Sunday as a cold front associated with the first upper low moves
toward the area. Precip chances slowly increase across the mountains
Saturday then spread across the area Saturday night and maximize on
Sunday. The front then washes out as it moves into the area from the
north on Monday. Precip chances taper of Sunday night and Monday in
response. Deep moisture and weak forcing return Tuesday as a weak
front moves in from the west with the second upper low/short wave.
Precip chances ramp back up in response.
Temps remain nearly steady 5 to 10 degrees above normal Saturday and
Sunday, rising to 10 to 15 degrees above normal Monday, before
dropping a few degrees Tuesday.
.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
At KCLT and elsewhere: Dissipating remnants of last evening`s
convection continues to shift east, with rain ending at all TAF
sites by 07z or 08z. N to NE winds will increase as a cold front
sags south of the area. This flow should advect some drier air into
the area and with mixing and lingering mid and high clouds, should
limit fog development. However, given the wet ground at all sites,
periods of light winds with clearing skies may result in patchy
ground fog, that could impact any of the airports thru daybreak.
However, confidence is too low to mention at this time, and whatever
does develop is not expected to be persistent. The increased mixing
may actually produce IFR or MVFR stratus cigs occasionally. The site
that the models hit hardest with that is at KAND, where I will put a
tempo for MVFR cigs. After daybreak, skies should clear and NE winds
will become marginally gusty, especially at the NC sites, with gusts
continuing thru the afternoon.
Outlook: Low level moisture begins to return from the south Thursday
thru Friday, resulting in a gradual increase in shower chances and
low cigs into the weekend.
07-13Z 13-19Z 19-01Z 01-06Z
KCLT High 98% High 100% High 100% High 100%
KGSP High 90% High 96% High 100% High 100%
KAVL High 100% 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...Freeze Warning from midnight tonight to 9 AM EDT Thursday for