Scientific Forecaster Discussion
fxus62 kgsp 181527
Area forecast discussion
National Weather Service Greenville-Spartanburg SC
1127 am EDT Wed Sep 18 2019
cool surface high pressure will build in today, remaining in place
through Friday. Temperatures will gradually warm again through the
weekend and into early next week.
Near term /through tonight/...
as of 1120 am EDT wednesday: the latest satellite imagery showed the
backdoor cold front now pressing into Georgia with a fairly solid
coverage of low clouds across the forecast area. Easterly upglide
continues to produce a few showers or drizzle focused across the NC
foothills. Forecast looks to be on track for the most part, although
I wouldn't be surprised if cloud cover is more stubborn than
expected (especially foothill locals), leading to highs a few
degrees cooler than forecast.
Otherwise, today we will see the first glimpse of fall, with
Max temperatures for this afternoon expected to climb to just
short of normal (normal in some locations further south).
As Hurricane Humberto continues to pull well away from the Carolina
coast, and dew point Imelda pushes over East Texas/west la, upper ridging will
remain overhead as cool sfc high pressure wedges down through the
mid-Atlantic and into Carolinas. For the rest of the forecast period
and just beyond, this wedge scenario will persist. With isolated
showers lingering, and even possibly a few rumbles of thunder this
afternoon, do expect this activity will taper off from east to west
this afternoon, as cloud cover decreases from east to west tonight.
Min temperatures for early Thursday morning will fall to normal or
just a few degrees below.
Short term /Thursday through Friday night/...
as of 300 am EDT wednesday: damming will be in place across the area
as we start the short term, with upper ridge stretching from the
Gulf Coast to the Great Lakes, Humberto off the East Coast, and a
deepening system in the Pacific NW/rockies. The parent surface high
for the damming will slowly slide SW through the period, briefly
settling over the Carolinas Friday before pushing offshore as we go
into the weekend. Temperatures will remain below-normal through the
period, seasonably cool and quite pleasant, but with a little
warming closer to normal on Friday. Enjoy it, because the heat
returns for the extended.
Long term /Saturday through Tuesday/...
as of 315 am EDT wednesday: as we move into the extended, the
wavetrain will slide east, pushing the upper ridge axis closer to
our area and whatever is left of Humberto farther out to sea. The
surface high will move offshore, and low-level flow will shift out
of the southeast, bringing warm air advection back into the region as thicknesses
begin to increase. This pattern will generally stay in place through
the extended. The Rockies low will cross the northern tier,
deamplifying the ridge but with the upper high stretched all across
the south late this weekend. A cold front will approach the Ohio
Valley early next week, but operational guidance has it falling
apart as it approaches the mountains Monday into Tuesday. The
mountains could see some rain out of it, but the dry spell will
continue across the Piedmont. Temperatures will steadily climb
through the period, reaching 90 (maybe even the lower 90s) in some
areas by the end of the extended.
Aviation /16z Wednesday through Sunday/...
at kclt and elsewhere: with a backdoor cold front south of the area
this morning and low level easterly flow, a mixture of VFR/MVFR
prevails at the taf sites this morning due to low cigs, as isolated
showers (mostly short-lived) showers continue to develop. Through
the morning hours, do expect VFR/MVFR cigs (possible IFR at kavl)
with the easterly flow in place. Late morning into early afternoon,
cigs will begin to improve to VFR, with VFR expected to prevail
through tonight. Patchy Mountain Valley fog will be possible towards
the end of the valid taf period.
East-northeast winds are expected today, with the exception of southeast at kavl, 7 to
12 kts this morning, becoming at or below 10 kts later today.
Outlook: patchy areas of Mountain Valley fog possible each morning.
Otherwise expect VFR with sfc high pressure in place.
15-21z 21-03z 03-09z 09-12z
kclt high 100% high 100% high 100% high 100%
kgsp high 86% high 100% high 100% high 100%
kavl high 100% high 100% high 88% high 83%
khky high 83% high 100% high 100% high 100%
kgmu high 90% high 100% high 100% high 100%
kand Med 79% 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: