Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 251044

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
644 AM EDT Sun Jun 25 2017

A cold front will settle southeast of the region this morning
with drier and cooler air beginning to spread in from the northwest.
These conditions are expected to persist over the forecast area
through much of the week as high pressure remains to our north.
As the high moves offshore, moist southerly flow will return
towards the end of the week.


As of 630 AM EDT Sunday: Have updated wx grids to add in some
isolated sprinkles generally south of I-40 and west of I-77 this
morning. A very weak shortwave embedded in the flow aloft, as well
as a bit of a finger of an upper jet streak, has allowed some light
rain to form from AL into N GA, with some sprinkles (or at least
light radar returns) spreading up toward the Blue Ridge. These
should be short-lived. Cloud cover remains a little higher than
expected across portions of the Upstate, specifically the Upper
Savannah Valley, and made some adjustments there. Other changes are
mainly for aviation-related parameters.

Otherwise, big change starts today in the wake of a cold front,
which had worked its way south of the forecast area by AFD time.
Longwave upper trough axis just to our west will continue to push
east, with thicknesses decreasing as surface high pressure begins
ridging in from the west. The trough will make little progress
through the period, but the airmass change will be felt in the form
of much lower dewpoints, especially tonight. High temps today will
likely be similar to those yesterday (due to less cloud cover)
except maybe in the mountains, though this is still a handful of
degrees below seasonal normals. Overnight lows tonight will be a
good 5 or so degrees below what we`ll see this morning, and ranging
anywhere from 3-8 degrees below seasonal normal. Overall, a really
pleasant day for late June.


As of 250 AM EDT Sunday: the short-term fcst picks up at 12z on
Monday with longwave upper trofing centered over the Great Lakes
and steep upper ridging in place over the Western CONUS. 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. The shortwave axis is expected to move overhead Tues
afternoon and then offshore by early Wed with heights beginning
to recover in its wake. At the sfc, a lingering frontal bndy will
be located over the SC Coast early Monday and slowly drift offshore
later in the day/evening. The rest of the period is marked by the
Canadian High sliding SE and towards our area on Tuesday before
ending up just to our north by the end of the period, 12z Wed.
As for the sensible fcst, most of the period should be dry. I do
have some slight chance PoPs on Tues as the upper shortwave
approaches the area and produces favorable ascent especially over
the higher terrain. Temps will be 1 to 2 categories below normal
for late June.


As of 235 AM EDT Sunday: the extended fcst picks up at 12z on
Wednesday with an upper shortwave moving off the Atlantic Coast.
As it does, heights begin to rebound over the fcst area as upper
ridging starts to build to our south. Another longwave upper trof
approaches the Great Lakes on Friday and then gradually slides
to our north over the weekend acting to flatten the ridge to our
south. At the sfc, broad high pressure will be centered just to
our north by early Wednesday with below normal temps in place
over the region. The high will slide off the Atlantic Coast on
Thursday putting the CWFA back under warmer and more moist SLY
low-level flow for the end of the work week. A cold front will
approach the fcst area from the west on Saturday, but is not
expected to move thru the CWFA until the end of the period on
Sunday. As for the sensible wx, Wednesday should be dry with the
high over us. Thurs and Fri will see a return to a more typical
summertime pattern with slight to solid chances for TSRA each day.
Chances for widespread TSRA increase on Sat as the front moves
into the fcst area. Temps and dewpts will start out about a category
below normal and steadily warm thru the period with values reaching
normal by the end of the work week.


At KCLT and elsewhere: VFR for all but KAND this morning, where an
area of LIFR cigs has persisted. These cigs aren`t far from
KGSP/KGMU, and even some a county south of KCLT, but with the front
continuing to push southeast, should not impact these other sites,
and should see improvement at KAND in the next couple of hours. But
generally only some passing high to occasionally mid-level clouds
through the period. N winds shoudl prevail through the period,
fairly light this morning but picking up around or just above 5kt
this afternoon, though KAVL should see some low-end gusts.

Outlook: Expect light winds and mostly clear skies through Thursday
as high pressure dominates the weather.

Confidence Table...

            10-16Z        16-22Z        22-04Z        04-06Z
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       Low   44%     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:




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