Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 141448

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1048 AM EDT Wed Mar 14 2018

Dry high pressure will build across the area today through Thursday.
Windy conditions will develop during the afternoon and early evening
during this time. A warming trend will commence Thursday through
Friday...before a cold front brings showers and cooler temperatures
to the region to start the weekend.


As of 1030 am: Piedmont snow showers have weakened and moved east of
the area (along with the upper trough axis), giving way to more of a
typical northwest flow snow shower event. Reflectivity associated
with these showers has been steadily diminishing with time, and
overall coverage gradually diminishing. This trend will continue as
moisture depth becomes increasingly shallow and low level flow backs
slightly. Nevertheless, additional accums of up to an inch (with
locally higher amounts where bands become anchored along terrain
features) appear likely in the usual northwest flow areas. Since
trends are not diminishing quite as fast as previously anticipated,
the advisory for the mountains was extended until noon.

Otherwise, the strong CAA behind the reinforcing trough will most
definitely overcome the downsloping NW flow and keep temperatures
very January-like today, with highs 15-20 degrees below seasonal
normals, and not getting above freezing above 3500ft. Strong winds
from the tight pressure gradient will continue across the mountains
through the day. Across the rest of the area, afternoon mixing will
allow additional gustiness to spread across the Piedmont. The
surface high pressure trying to build in from the Gulf Coast will
allow winds to drop off somewhat overnight, though not completely,
with another very cold night (~10 degrees below normal) expected.


As of 235 AM Wednesday...Upper level heights continue to rise early
Thu as a strong subs zone begins to build across the FA. High
pressure will dominate the overall pattern across the srn states
while a dry sfc trof develops over the mtns creating a moderate mtn
wave. The p/grad increases during the day and sfc winds will respond
by mid-day as mixing increases to arnd 6 Kft. The latest NAM and GFS
soundings show uniform w/ly flow thru the mixed layer and a gust
potential of 30-40 kts by the early afternoon across the Upstate and
abt 10 kts higher at KAVL. At this point...A wind adv seems likely
across the higher terrain and possibly over the portions of the
non/mtns. As drier td/s are mixed to the sfc...RH values will once
again approach SPS criteria for fire danger or even RFW. It/s likely
10-hr fuel moisture levels will be in the single digits over many

The atmos will remain dry thru a deep layer Thu night and most of
Fri while winds will relax overnight as the sfc trof pushes east.
Increasing moisture within the BL is noted on the profiles which
shud preclude a sigfnt fire wx threat. A moist warm front will
approach the mtns late in the day and -shra with developing low-end
nrn mtn -snsh could working from the west by the late evening. No
sigfnt sn accums are expected overnight as any precip will change
over to all rain shortly aft sunrise. Max temps will return to
normal levels Thu and likely rise a cat abv normal on Fri. Mins will
be held a few degrees abv normal as well.


As of 315 AM Wednesday...Some uncertainty continues to begin the ext
range with the op models showing varying ideas with the synoptic
pattern. The 00z ECMWF has now strengthened an incoming low pressure
center and drives it off the Atl coast by 12z Sun. The GFS on the
other hand...continues to produce a weak system becoming slowed
by a mlvl ridge axis thereby deviating it/s sfc low NE then
into the FA by Sun morning. In any case and sensible wx-
wise...Sat looks wet...but with the GFS showing a good
convective potential across the srn MS/AL/GA...the amt of
moisture adv ahead of the system is somewhat suspect. So...have
maintained low to mid chance PoPS with likelies only across the
far wrn zones by the afternoon. Hard to tell on deeper
convection as well with winds possibly remaining e/ly thru early
afternoon and probable layered cloud cover. Thus...thunder has
been left out of the fcst for now. Tricky temps as well Sat
depending on whether or not a llvl insitu wedge persists into
mid-day or not. Basically went with strong MOS blend to add
more climo weight which gives temps a couple cats below normal.

The column shud dry out rather deep on Sun as a low amp ridge axis
crosses the region. This will preclude much of a precip threat
however pockets of h5 energy are progged by the GFS to break thru
the ridge by late evening and into the overnight. Still...kept the
FA mostly dry thru the afternoon Mon before a well defined cold
front approaches from the west. The op models have a better handle
on this feature and it now looks like a rainy period late Mon into
Tue before the front moves east of the FA by 18z or so. Temps will
rebound Sun and Mon with highs once again abv normal...and mins shud
be held abt 10 degrees abv normal during this time.


At KCLT and elsewhere: -SHSN continuing across the mountains and
adjacent foothills, so TEMPO groups continue for KAVL and KHKY.
Expect MVFR to possibly IFR conditions if the snow rates pick up.
All other sites should be VFR through the period with only
occasional low VFR stratocu early in the period before the upper
wave lifts. NW winds expected through most of the period. KAVL will
see gusts through the period 25-30kt. Other sites will see winds
pick up with afternoon mixing and gusts generally to about 20kt.
Winds should begin to subside this evening and back around to the
WSW, with timing at KCLT still 06z. Introduced another round of
gustiness late in the period for KCLT.

Outlook: VFR conditions are expected to persist through at least
Thursday. Chances for precipitation and restrictions will gradually
increase from late Friday into the weekend.

Confidence Table...

            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       High  96%     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:


Gusty northwest winds developing in the wake of a strong upper air
disturbance will bring drier air to the region Today. Sustained
mountain winds of 15 to 25 mph, with gusts as high as 40 mph are
expected, while winds/gusts will be about 10 mph less than that in
the foothills/Piedmont. Meanwhile, minimum RH in the 15 to 25
percent range is expected across the Piedmont and foothills, with 25
to 30 percent min RH expected in the mtn valleys. A Fire Danger
Statement has been issued for much of northeast GA, but
otherwise fuels are close but are not dry enough to coordinate any
special Fire Wx products for the rest of the area. With fuels having
another day to dry out, and another dry/windy day anticipated
tomorrow, coordination will be needed later today for potential fire
weather headlines for Thursday.


GA...Fire Danger Statement from 2 PM this afternoon to 7 PM EDT
     this evening for GAZ017-018-026-028-029.
NC...Winter Weather Advisory until noon EDT today for NCZ033-


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