Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 191742

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1242 PM EST Sun Feb 19 2017

A warm surface high pressure system will move into the area through
the early part of the week, with strong upper ridging bringing
temperatures close to record highs. A cold front with minimal
moisture will move through the area by midweek, with a dry end to
the work week to follow. The next frontal system with substantial
rain and thunder chances will arrive next weekend.


As of 1230 PM EST: Satellite imagery continues to show clouds banked
up on the W side of the mtns. Seeing some stratocu development
downwind of the mtns...more than expected...but not enough to mess
up the high temp fcst. Temp trend was adjusted for obs, but
otherwise no changes.

A full latitude ridge will build east from the central CONUS this
afternoon through tonight. With downsloping and scattered clouds
permitting decent insolation today, will feature max temperatures a
couple of degrees above guidance but likely just below record highs
this afternoon. Surface high pressure building into the region
tonight will permit fairly good radiating conditions and plenty of
30s mins in the mountains and 40 to 45 east, but still well above


As of 200 AM EST Sunday: The upper pattern remains highly amplified
Mon as a strong h5 ridge axis crosses the FA. Soundings are showing
a well defined subs inver in place that will persist to some degree
thru the period. A sfc high ridges in from the north...however max
temps Mon shud have no problem approaching or even breaking record
highs in a very dry column and weak flow maintained through a deep
layer. On Tue upper heights fall...but they will retain a flat
ridging config as a disconnected weak upper low moves into the wrn
GOM. General downward forcing remains in place while the sfc high
becomes the dominant feature and centers off the Atl coast. This
high will become a player Tue night as it helps hold off a weak
frontal bndry moving toward the NC mtns. The latest guidance has
sigfnt/ly slowed the progression of this bndry and the amount of
available llvl moisture. Pops have therefore been adj down through
the overnight. P/type will not be a concern with partial thicknesses
across the higher elevations remaining quite deep. Max temps on Tue
will be a little cooler than Mon as subs decreases and mid/high
clouds stream in from the NW...yet temps should still reach arnd 10
degrees abv normal.


As of 230 PM EST Saturday:  The medium range fcst period initializes
on Tuesday evening amidst weakening east coast ridging by way
of a progressive northern stream trough, while a close southern
stream upper cyclone moves out of the Rio Grande Valley into the
central Gulf of Mexico.  At the surface, the primary features of
note will be a broad anticyclone along the east coast and a cold
front extending across the Great Lakes region into the OH Valley.
Synoptic pattern evolution moving through the period will be
highlighted by total breakdown of the amplified east coast
upper ridge leading to migration of the elongated surface high
southward near Bermuda.  The aforementioned cold front looks to
stall across the OH Valley, possibly making it as far east as
the Central Appalachians, however not likely intruding into the
Southern Appalachians thanks to the repositioned surface ridge.
Meanwhile, guidance seems to have converged on some details
regarding the closed H5 cyclone moving through the Gulf, which
now looks a bit weaker, strongest in the ECMWF, with good track
agreement to the southeast toward southern FL.  Thus, little
if any impacts are expected across Northeast GA and the Western
Carolinas.  That said, weak moist upglide atop the offshore high
will at least warrant low end pops both Wednesday and Thursday.
Moving along, as the southern stream H5 low moves out of the
picture, a few days of southerly flow are expected across the
southeast states thanks to the Bermuda high, while a west coast
system gains strength and plows through the plains into the MS
River Valley by Friday.  Surface cyclogenesis beneath a modestly
deep upper low looks to yield a rather strong/progressive surface
cold front that will march across central CONUS and into the
Appalachian region either on Friday evening, possibly sometime
on Saturday.  Timing inconsistencies within the op guidance lead
to much uncertainty regarding the details, nevertheless, expecting
a strong and potentially convectively active fropa next weekend.
Behind said front, broad Canadian high pressure looks to dive
southward into the Plains by yielding drier yet cooler conditions
to round out the weekend.   Temperatures are expected to remain
well above normal, cooling to near normal at periods end.


At KCLT...VFR through the period. Satellite imagery shows a few
stratocu developing across the Piedmont, so a FEW050 will be
included to start the fcst. Expect wind to remain out of the NW thru
late afternoon. Cannot rule out a few low-end gusts. The clouds
should clear out and the wind should go light N overnight as high
pressure centered to the N settles over the region. Clear sky
continues Monday morning with light wind...probably out of a NE
direction. The dry air mass should keep fog at bay.

Elsewhere...still seeing low clouds over the mtns, forming in the
WNW upslope flow region near the TN border but blowing up the Fr.
Broad Valley to KAVL. This will keep at least a temporary MVFR
ceiling at that location into the middle part of the afternoon. The
moisture slowly dries up so think the clouds will stay SCT after
about 21Z. Otherwise, just scattered clouds with a base around 050
outside the mtns. Gusty NW wind will abate with sunset and clouds
should also dissipate at that time. Clear sky and light wind
overnight. Cannot rule out brief fog coming off the lake to KAND
around daybreak. Monday should be clear with a light N or NE wind.

Outlook: Expect VFR conditions to continue through early in the week
before another low pressure system gradually brings moisture back to
the area from Tuesday through late week. Precipitation and
associated restrictions remain highly uncertain from mid week on.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  87%     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:



  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      72 2014     16 2015     54 1951      3 2015
   KCLT      76 2014     26 2015     55 1961      8 1958
   KGSP      75 2014     30 2015     55 1961      9 1958
                1916        1900                    1900


  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      75 1939     26 1908     50 1951      4 2015
   KCLT      77 2014     31 2015     59 1939      7 2015
   KGSP      75 2014     33 2015     57 1939      9 2015




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