Area Forecast Discussion
Issued by NWS Greer, SC
FXUS62 KGSP 221841
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
241 PM EDT Sat Oct 22 2016
High pressure will build across the region over the weekend. A dry
cold front will move through on Monday...with strong high pressure
building back in through the middle of next week.
.NEAR TERM /THROUGH TONIGHT/...
As of 240 PM: Building dry high pressure will provide clear
conditions across the western Carolinas and NE GA through Sunday. Gusty
northwest winds should continue through the rest of the daylight
hours today. Winds are forecast to weaken to a steady light NW wind
overnight. Winds could become occasionally calm near KCLT, KHKY, and
KAND, possibly allowing thin patchy frost to develop during the pre
dawn hours. Low temperatures are forecast to range from the low 30s
across the mtns to the upper 30s east. A noticeable thermal belt is
expected across the foothills, keeping temps in the low 40s. I will
leave the Frost Advisory in place.
On Sunday, near term guidance indicates that a shallow lee trough
will form during the mid morning hours, resulting in light SW winds
across the foothills and Piedmont by 15z. Light return flow should
remain through the rest of the day. Using a blend of guidance, I
will forecast a high temperature near 70 within the mtn valleys to
the low to upper 70s north to south across the foothills and
Piedmont. Afternoon RH values will generally range in the 20s,
highest east of I-77.
.SHORT TERM /SUNDAY THROUGH TUESDAY/...
As of 215 PM Saturday, a series of short waves digging into the
northeast Conus will act to deepen the long wave trough along the
East Coast during the short term. This will send a dry/reinforcing
cold front into the area on Monday. Cold advection will initially be
rather weak and limited primarily to the mtns, with downslope flow
and anomalously high early day thickness values supporting max temps
of almost 10 degrees above climo Monday afternoon. Thicknesses are
progged to decrease enough by Tuesday such that temps should be very
close to climo Monday night through Tue afternoon. Otherwise, the
air mass will remain very dry, with nary a cloud in the sky expected
through the period.
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 230 PM EDT Saturday...The main feature of interest in the
medium range is a fast-moving trough that will cross the CWFA
Thursday or Thursday night. An accompanying surface low pressure
system will organize over the Midwest on Wednesday, then deepen
gradually and stall over the Great Lakes Thursday into Friday. The
main difference between the 12z GFS and 00z ECMWF is that the GFS
doesn`t considate the upper trough as much as the ECMWF. The result
is that the ECMWF has more Gulf moisture inflow into the system and
has more DPVA across the southern Appalachians. So the GFS wrings
out only a few westerly upslope showers along the TN border. The
ECMWF has much more QPF response, but is probably overdone, even
with the greater moisture and forcing. So I trended toward the low
side of guidance for PoPs for Thursday into Thursday night, but this
still results in a slight increase from previous forecast. Even if
the ECMWF ends up being right, QPF will be fairly light. Otherwise,
the medium range looks dry with near normal to slightly above normal
.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: Building dry high pressure will provide VFR
conditions through the 18z TAF period across the western Carolinas.
Gusty northwest winds should continue through the rest of the
daylight hours. Winds are forecast to weaken to a steady light NW
wind overnight. Winds could become occasionally calm near KCLT,
KHKY, KAND, possibly allowing thin patchy frost to develop during
the pre dawn hours. Near term guidance indicates that a shallow lee
trough will form during the mid morning hours, resulting in light SW
winds across the foothills and Piedmont by 15z.
Outlook: Dry high pressure will continue to spread across the
southeast CONUS on Sunday with another reinforcing Canadian High
moving over the region on Tuesday.
18-24Z 00-06Z 06-12Z 12-18Z
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 High 100% 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:
GA...Frost Advisory from midnight tonight to 9 AM EDT Sunday for
NC...Frost Advisory from midnight tonight to 9 AM EDT Sunday for