Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 190737

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
237 AM EST Sun Feb 19 2017

A warm surface high pressure system will move into the area
through early next 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 will substantial
rain/thunder chances will arrive next weekend.


As of 200 AM EST: The phasing upper trough axis is crossing the
Appalachians early this morning. Associated deformation zone forcing
around the back side of the low circulation is sliding southeast
from Kentucky and central Tennessee back toward the NC/TN line, but
precipitation coverage is not particularly robust in this region.
Will thus keep mainly lower end slight chance to chance PoPs going
in the NC mountains near the TN line through the morning hours
before conditions dry this afternoon. Otherwise, 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 climo.


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 and elsewhere: Lingering lower level moisture under the
passing upper low is contributing to spotty MVFR cigs around the
region. The current thinking is that the lower cloud deck will be
mainly scattered overnight as slightly drier air works in everywhere
but the western mountains. Will feature MVFR fog developing at KAVL
and KAND, with slightly lesser chances at the other foothill and
piedmont sites. Winds will remain NW through the period at KAVL,
while SW winds at the foothill/piedmont sites early will become
northwesterly after 14Z. VFR level stratocumulus and passing higher
clouds should be mainly scattered through the rest of the day before
clearing tonight as the ridge builds firmly overhead.

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...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       High  96%     High  96%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       Med   64%     High  81%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High  94%     High  93%     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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