Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 240728

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
328 AM EDT TUE MAY 24 2016

High pressure will prevail over the Southeast most of this week. A
moist southerly flow will develop by tomorrow, which will lead to
warmer temperatures and mainly afternoon chances of showers and
thunderstorms each day through Friday.


As of 245 AM, lingering mid clouds trapped under a subsidence
inversion will move east across the area through the early morning
and east of the area by noon. Patchy fog, possibly dense in the
mountain valleys, should dissipate quickly after daybreak. Upper
ridging builds into the area today and tonight as surface high
pressure moves east across the area. This results in a weak, but
increasing southwesterly flow. Expect some ridge top cumulus to
develop during the afternoon, with mostly sunny skies elsewhere.
With thicknesses rising, highs today will top out near or a little
above normal. Any ridge top cumulus will dissipate with loss of
heating this evening. However, expect an increase in clouds across
the mountains overnight as a weak short wave moves through the ridge
and into the area. Forecast remains dry, with lows dropping to near
or a couple of degrees above normal. Patchy fog will again be
possible, despite the increasing clouds.


As of 315 AM Tue: High pressure over the South Atlantic coast
will bring south to southwest return flow into the area Wed and
Thu. Diurnal instability will trend upward from day to day, driving
diurnal showers and thunderstorms. Subsidence will keep the Piedmont
sufficiently stable Wed, so PoPs are confined to the mountains then;
they expand to about the I-85 corridor Thu. Minimal shear implies
mainly disorganized pulse storms can be expected with localized
downbursts being the main threat besides lightning. Temps will
rise about a category above climo each day.


As of 300 AM Tue: The late week pattern will be dominated by a
broad upper ridge centered over the mid-Atlantic coast and sfc high
pressure. This by itself would result in rather run-of-the-mill
weather for late May, in which PoPs would be tied to diurnal
instability and temps at or a little above climo. However, the
proverbial fly in the ointment is what appears to be increasing
consensus for a tropical low to move into the Carolinas over
the weekend. Spread on the track thereof is still pretty wide
overall, but the 00z GFS and EC both show landfall near the Grand
Strand. They differ on its position thereafter. Winds do not appear
to be of concern on land at this point, but the nature of moisture
flux varies across the guidance spectrum, so it is difficult to
say whether PoPs would be greatly increased or decreased by the
presence of the system. It is difficult to make a model blend (for
grid production purposes) that does not reflect any influence from
it, though confidence on its track remains moderate at best. My
preferred choice of action at this point is to reflect PoPs only
slightly above climo, with mainly diurnal trends, but elevated
sky cover and slightly cooler temps Sun-Mon.


At KCLT and elsewhere: A BKN area of mid clouds trapped under a
subsidence inversion will slowly dissipate by daybreak, with FEW to
SCT clouds elsewhere. Although patchy fog develops again by
daybreak, KAVL looks to be the only TAF site with restrictions.
Could be VLIFR once again. Expect little in the way of clouds today,
but some afternoon ridge top CU should develop. Mid and high clouds
return from the west tonight. Light and variable to calm winds this
morning will become S to SW by afternoon. Winds become light or calm
this evening.

Outlook: Mainly VFR conditions will prevail through the week, but
patchy morning fog chance continues at KAVL. Scattered afternoon
SHRA/TSRA may return Wednesday, with daily coverage increasing
Thursday and Friday.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High  93%     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 schedule TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:




SHORT TERM...Wimberley
LONG TERM...Wimberley
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