Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 240712

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
312 AM EDT Sat Jun 24 2017

Light showers will linger Saturday morning as the front slowly
crosses the area. Thunderstorms may redevelop later this morning
just ahead of the cold front over the piedmont and foothills.
Unseasonably cool and dry conditions will spread over the forecast
area in the wake of the front on Sunday and persist through the
middle of next week.


As of 230 AM EDT Saturday: Remnants of Cindy are rapidly moving
northeast; just in the past couple of hours the closed circulation
over WV has been absorbed by the larger trough stretching down the
Eastern Seaboard. Initial band of convection has moved east into
central NC, but as the front continues to drop into the Piedmont
today, should see an increase in convection along it especially for
the Upstate. While deep-layer shear will be confined to the north,
instability will increase quite a bit today in the warm sector,
especially with a little cooling of temperatures aloft resulting in
increased lapse rates. High PW values around 2" will remain south of
the front, so with sbCAPEs progged between 1500-2000 J/kg but
general lack of shear, expect that really only damaging winds will
be the threat today (and lightning of course). New CAM guidance
coming in has some convection, perhaps some strong, developing
across the NC Piedmont through mid-afternoon, then blowing up
convection across the Upstate just after peak heating. Timing of the
frontal passage will be critical, because by this point the front is
really trucking and should be pushing quickly out by 00z.

With the high PWs, there remains the concern for isolated flash
flooding, especially with soil moisture remaining fairly high. Not
enough concern for a Flash Flood Watch but will have to be
monitored, but for now 12-hr QPF for today averages only about 0.5".

Temperatures today will be slightly lower than yesterday and below
seasonal norms, but with plentiful surface moisture in place to make
it feel nice and muggy. Improvement begins tonight though with
dewpoints dropping off and low temps near seasonal normals (instead
of 5 above), with the improving trend continuing into the short term.


As of 305 AM EDT Saturday: the short-term fcst picks up at 12z on
Sunday with longwave upper trofing moving across the Great Lakes and
steep upper ridging over the West Coast. The upper lvl pattern is
not expected to change much thru the period with the trof axis
remaining to our north and the ridge persisting to our west. By
early Tuesday, an upper shortwave will dig southward on the backside
of the upper trof providing increased upper-lvl divergence just
ahead of it. At the sfc, a lingering cold front will be located just
to our south to start the period. The model guidance is slow to move
the bndy farther south and offshore due to the persistent SLY flow
from the Bermuda High. By Monday afternoon, what`s left of the bndy
has finally moved offshore as the Canadian High slides SE and
towards our area. As for the sensible fcst, there is only some brief
slight chance PoP over our southeastern-most zones Sunday afternoon
with the rest of the period expected to be dry. Temps will be
slightly below normal for late June.


As of 225 AM EDT Saturday: the extended fcst picks up at 12z on
Tuesday with a reinforcing upper shortwave digging southward on the
backside of a broad upper trof. The axis of the shortwave will move
over the fcst area Tuesday afternoon and then lift NE by early Wed.
As it does, heights begin to rebound as upper ridging begins to
build to our south and persist over the region into the weekend. At
the sfc, broad high pressure will be centered just to our NW by
early Tuesday with below normal temps over the region. The high will
slide SE and over the fcst area early Wednesday and then slide off
the Atlantic Coast on Thursday. This will put the CWFA back under
warmer and more moist SLY low-level flow for the rest of the period.

As for the sensible wx, the period should be mostly dry with some
slight chance PoPs for Tuesday afternoon/evening and some slight to
solid chance PoPs for Thurs and Fri when we get back under more
moist southerly flow. Temps and dewpts will start out well below
normal and steadily warm thru the period with values reaching
climatology by the end of the work week.


At KCLT and elsewhere: All TSRA has moved out of the area for
tonight, though -SHRA/VCSH lingers. Expect MVFR cigs to develop at
most sites through the early morning hours, though only enough to
warrant TEMPO for the NC TAFs. Another round of convection should
fire later today as the front approaches from the west, with best
chances for Upstate TAFs and KCLT this afternoon, but with rapid
clearing/drying expected after 00z. S/SW winds will continue 5-10kt
with occasional low-end gusts early in the period, but as the
remnants of Cindy continue to lift NE, the gradient will slacken and
winds will subside. For now only anticipate the wind shift to NW at
KAVL at the end of the period.

Outlook: The cold front will slide south of the area early Sunday,
with drier weather developing through most of next week.

Confidence Table...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       High  94%     High  96%     High 100%     High 100%
KGSP       High  83%     High  87%     High 100%     High 100%
KAVL       High  83%     High  81%     High 100%     High 100%
KHKY       High  95%     High 100%     High 100%     High 100%
KGMU       High  90%     High  86%     High 100%     High 100%
KAND       High  85%     High  82%     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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