Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 300735
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
335 AM EDT Fri Sep 30 2016

.SYNOPSIS...
A dry southwest flow of air will linger across the region through
this weekend. Progressively warmer temperatures are on tap through
early next week. The path of tropical cyclone Matthew will be
closely watched as it tracks north near the Atlantic coast next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Occasional convection continues to fire in the warm sector and move
N/NE early this morning, mainly near and east of the I-77 corridor.
Some of the cells have been quite strong and/or heavy rain
producers. This activity has been supported by a mid-upper level
speed max digging into the base of the trough extending from upper
low centered over the Ohio Valley. There`s been enough of an
eastward component to cell motion that training hasn`t been much of
an issue, yet. The latest mesoscale guidance suggests some semblance
of convective coverage will persist through daybreak. In fact, the
latest HRRR depicts an uptick in coverage around 12Z. Pops have been
increased to solid chance along much of the I-77 corridor through
sunrise. We aren`t expecting a whole lot out of this activity, but
will certainly need to watch for the training potential, especially
in the urban corridor along I-77.

The aforementioned speed max is expected to lower heights enough
such that the frontal boundary should finally nudge east of the
forecast area by early afternoon, spreading much drier air into the
NC Piedmont and northern foothills. Thus, deep convection in the
near term is expected to peak around daybreak, then diminish through
the morning, with nothing expected this afternoon. Some of the
mesoscale and short term guidance tries to develop some ridge top
convection this afternoon, but forecast soundings look positively
hostile to convective development, so we`re not buying it. Max temps
are expected to be (finally) right around normal, except along the
I-77 corridor, where maxes of a category or so above climo are still
expected. With the dry air mass in place, all areas are expected to
see around to a little below climo min temps tonight.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
At 240 AM Friday: GFS and ECMWF indicate that the center of a H5
closed low will lift north across the Great Lakes region this weekend. The
mid level pattern across the region will likely feature a Bermuda
High and a trof from the Ohio River valley south to the Mississippi
Delta. Short range guidance shows that a dry slot associated with
the Great Lakes low will rotate across the western Carolinas. This
pattern should result in dry conditions and high temperatures
ranging from the mid 70s within the mtn valleys to the low 80s east.

On Monday, it appears that an asymmetrical mid-level omega block
will develop over the northern CONUS, with the ridge axis over the
Mid West and Great Lakes. TC Matthew is expected to be tracking
north near the eastern tip of Cuba by late Monday. Sensible weather
across the CWA will remain unchanged from the dry weekend. High
temperature are forecast to warm a degree or two over values reached
on Sunday.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
As of 250 AM Friday: The path of TC Matthew will gain most of the
attention through the extended period. Both the GFS and ECMWF
indicate that Matthew will track north, tracking parallel along the
Atlantic coast from FL to NC. To the west, the northern tip of a H5
ridge will reach the southern Appalachians, sourced from a high over
Mexico. To the north, another deep low is expected to organize
across the nrn plains. The pattern does not appear to be supportive
of heavy rainfall across the CWA, developing ahead or west of
Matthews track. I will keep the forecast generally dry from Tuesday
through Thursday. Temperatures are forecast to remain between 3 to 5
degrees above normal.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
At KCLT and KHKY, surface front remains virtually stalled just west
of the terminals early this morning, with plenty of low level
moisture in place. This creates the very real potential for another
round of fog and/or low stratus this morning. In fact, KCLT was
already reporting a low MVFR cigs at issuance time, and there`s
plenty of IFR cigs not too far away. Meanwhile, SHRA were near the
KCLT airfield at 0530Z (tempo`d through 07Z), and this may result in
mixing out the lower cigs, at least for a little while. Based upon
observational trends, as well as signals from the guidance, there`s
enough confidence to add a mention of IFR cigs at both terminals
later this morning, but enough uncertainty exists such that these
conditions will be handled largely with tempos. The front is
expected to finally punch through by late morning, so improvement to
VFR should be rapid, with VFR conditions persisting through the end
of the period.

Elsewhere: It`s now looking doubtful that earlier forecast
restrictions will materialize at KAVL. An up-valley wind of 5-10 kts
is expected to persist, which should keep temp/dewpoint spreads
around or above 5 degrees. Suppose a brief IFR cig still cannot be
ruled out (and this is hinted at in the forecast with a tempo for
FEW008/SCT020), but all restrictions have been removed from the
forecast. With drier air lingering behind frontal boundary, all
sites are forecast to see VFR conditions persist for the next 24
hours.

Outlook: VFR conditions expected in most places through the
beginning of next week as dry high pressure settles in over the area.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       Low   55%     High  93%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  85%     High  99%     High 100%     High 100%
KHKY       Med   70%     High  92%     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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...NED
NEAR TERM...JDL
SHORT TERM...NED
LONG TERM...NED
AVIATION...JDL



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