Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 192317

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

Warm high pressure will move over the area through the early part of
the week, bringing temperatures close to record highs. Modest
rainfall will move over the area by mid week, followed by brief
drying, before a frontal system arrives next weekend with rain and
thunder chances.


As of 615 PM EST Sunday:  Updated discussion for TAF issuance.
As for the public fcst, things remains on track and no sig changes
were made with this update. Did tweak hourly t/td/sky to better
align with recent obs/sat.

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.

Rather benign springtime weather is expected over the next 24 hours
as a progressive upper pattern brings a full-latitude upper ridge
eastward and supports high pressure moving past to the north. The
only problem is that it isn`t spring, it`s still winter, and now
the trees are blooming and the birds seem confused. Sky should
clear and wind should diminish with sunset. In spite of clear
sky and light wind, low temps will still be on the order of ten
degrees above normal. Sky should be sunny on Monday with more
light wind. High temps will continue well above normal and might
flirt with records, particularly at GSP.


As of 2pm EST Sunday: Upper ridge will be in place over the area
Monday night with light and variable surface flow. Ridge and surface
high move east on Tuesday with light southwesterly flow picking-up
Tuesday afternoon that will gradually increase dewpoints. Airmass
remains convectively stable Tuesday evening with only an outside
chance of a light shower, primarily over the higher terrain. Chances
for precip. improves on Wednesday as boundary layer moisture
continues to improve and with upper flow becoming northwesterly with
some embedded shortwave impulses.  Models develop some marginal
instability with CAPE to 100 j/kg Wednesday afternoon and not a lot
of cap.  Deep layer shear is also marginal. Thus, some widely
scattered marginal convective showers will be possible late on
Wednesday, with any activity rapidly dying after sunset.
Temperatures remain well above normal Tuesday and Wednesday with
clouds increasing with the change in upper flow pattern Tuesday


As of 220 PM Sunday: A quasi-zonal/fairly progressive flow pattern
will be in place across much of the eastern 2/3 of the conus through
the period. SW low level flow will support plenty of warmth early in
the period, as temps are expected to remain around 20 degrees above
climo through the end of the work week. The southerly flow will also
bring about increasing low level moisture, which combined with very
strong insolation could yield positive surface-based buoyancy by Thu
afternoon. Also by this time, global model guidance hints at warm
frontal activation across the central/southern Appalachians and
vicinity, as cyclogenesis commences across the southern Great
Plains. Therefore, isolated-to-widely scattered convection,
including thunderstorms is not out of the question Thu afternoon and

Although the warm front will be long gone by Friday, additional
convection is possible Fri afternoon, particularly in response to
terrain effects, and chance pops will be carried in most locations
by the end of the day. Model guidance is gradually coming into
better agreement regarding the advance into our area of a frontal
boundary associated with aforementioned deepening cyclone early in
the weekend, with late Fri night/early Saturday appearing to be the
most likely time for fropa in our forecast area. Likely pops will be
carried across much of the area during this time. The convective
potential remains the most interesting aspect of this event, and
while it does not appear that the time of day will be conducive to
robust buoyancy, it appears fairly likely that some degree of sbCAPE
will be in place. Meanwhile, shear will likely be adequate for
organized convection, although the latest guidance depicts fairly
unidirectional profiles with a strong-but-not-scary low level jet.
This would certainly makes sense with the better deep layer forcing
passing west and north of the area, but it all honesty it`s still a
bit early to get too far in the weeds with severe wx parameters.

Cooler and much drier air will push into the area for the last
couple of days of the period, although temps are expected to remain
a good 10 degrees above normal through the weekend.


At KCLT:  VFR through the period as high pressure prevails
beneath amplified upper ridging. Thus, skies will remain mostly
skc overnight before high cirrus streams in on Monday.  Winds are
expected to remain light nly overnight and through much of the
morning, before esely veering is expected late in the taf cycle.

Elsewhere:  Trends all similar to that of KCLT above, however with
good radiational cooling tonight, am expecting xover temps to be
threatened a bit.  Specifically at KAVL/KHKY and KAND where mvfr/ifr
fog is possible by around daybreak before clearing to skc/cirrus.

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...

            23-05Z        05-11Z        11-17Z        17-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     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%     Med   66%     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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