Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 280702

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
302 AM EDT Tue Mar 28 2017

A cold front will approach from the northwest today and settle
southeast of the area tonight into Wednesday. Drier weather will
develop as high pressure builds southward from eastern Canada along
the east coast. Moisture will gradually return on Thursday, with
abundant moisture setting up by Friday as a strong low pressure
system moves east from the Mississippi River Valley. Drier weather
will return for the weekend.


As of 250 AM EDT: The lead convective band ahead of the better upper
support is driving quickly into the I-77 corridor of the western
Carolinas early this morning. Strong convection remains possible in
piedmont sections through 5 am as mid level lapse rates steepen up
and low level flow backs slightly. The secondary band of convection
driving southward from central and eastern Tennessee continues to
push mainly across northern AL and northern GA into the more
unstable air. Western sections of our forecast area should see
mainly rain/showers through the early morning hours as thunder
chances erode.

Otherwise, water vapor imagery shows the upper level wave lifting
northeast over the Ohio Valley, with the trailing trough axis
rapidly approaching the southern Appalachians early this morning.
The upper trough axis will cross the northern tier this moving and
be generally east of the area by 18Z. Mid level drying will also
work in quickly from the west through the later morning hours.
However, the surface cold frontal passage will be a bit delayed and
scattered shower/thunderstorm redevelopment along the passing front
is expected this afternoon, especially along and east of I-77.
Westerly downsloping flow will work against coverage in most other
locations. Upper ridging will develop tonight as the surface cold
front gradually settles off to the southeast by daybreak Wednesday.


As of 255 AM EDT Tuesday: Upper ridging will build over the area
through Wednesday east of a strong closed low moving across north
Texas. The passing surface cold front will settle well south of the
region and high pressure will nose down east of the Appalachians
from the Great Lakes/eastern Canada through Wednesday night. Despite
the fropa, good insolation will boost temps back into the upper 70s
to lower 80s east of the mountains Wednesday afternoon.

The upstream low pressure system will lift northeast through the
southern plains on Thursday with persistent ridging downstream
across the southeast. Very weak upglide may get reestablished over
the developing cold air damming as early as late Wed. night, with
PoP increasing gradually through Thursday. Will lean toward the
cooler MOS temps for Thursday afternoon with cold air damming onset
quite possible.


As of 255 AM EDT Tuesday: Heights will fall from the mid Mississippi
river valley and the lower OH valley toward the TN river valley
through the day on Friday. This trough should cross our region
Friday night. Improving upglide moisture will get established well
east of this system by Thursday evening and deeper moisture will
arrive mainly Friday through Friday night. The surface low pattern
should evolve in a Miller B type fashion, with gradual erosion of
the wedge layer and instability steadily uncovered from south to
north during the day Friday. This will make thunderstorms quite
possible, and severe weather not out of the question Friday as the
southerly low level jet ramps up.

Dry ridging will return over the southeast Saturday through Sunday.
Temperatures should run generally 5 to 10 degrees above climatology
in most areas over the weekend. Atlantic moisture return around the
high pressure, and associated with upslope flow, may bring some
clouds back into the picture Monday, and possibly light
rain/showers. Temperatures should thus be a bit cooler Monday
afternoon, with less diurnal range.


At KCLT: Convection working east from the NC foothills into the
piedmont will require a TEMPO for TSRA as thunderstorms strengthen
after 07Z under the steepening lapse rates aloft. Anticipate a
period of moderate rain behind the convection before the showers
gradually taper off from the west through 11Z. Ceilings should
gradually settle down in the MVFR range with the steadier rain. IFR
is possible but not likely at this point. Anticipate some recovery
to lower end VFR by mid to late morning, with the trailing surface
cold front then approaching from the northwest for the afternoon
hours. Will time the PROB30 for TSRA along the front to mainly the
17Z to 21Z period. Surface winds will be southwesterly with possible
low end gusts this afternoon, turning WNW with fropa during the
evening hours.

Elsewhere: Thunderstorm chances will be best around KHKY through the
early morning hours, with mainly light to moderate rain across the
Upstate TAF sites and KAVL as the ongoing convection moves east.
Gusts are likely in the stratiform rain zone before winds toggle
back toward southwesterly ahead of the cold front approaching from
the northwest. Coverage along the approaching boundary this
afternoon should be less than at KCLT as drier mid level air works
in from the west. Anticipate mainly MVFR cigs this morning,
recovering to VFR by late morning, and with tempo MVFR for any isold
showers/thunderstorms that might form. Southwest winds will be gusty
at times ahead of the front, turning northwest with fropa later this
evening. Winds will remain NW at KAVL throughout.

Outlook: Drier conditions should briefly return Wednesday before
another storm system begins affecting the region Thursday through
Friday. Drier conditions will return again for the weekend.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       Med   79%     High  85%     High 100%     High 100%
KGSP       High  95%     High  96%     High 100%     High 100%
KAVL       Med   66%     High  96%     High 100%     Med   75%
KHKY       Low   42%     Med   75%     High 100%     High 100%
KGMU       High  96%     High  87%     High 100%     High 100%
KAND       High  90%     High  80%     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:




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