Scientific Forecaster Discussion
fxus62 kgsp 152238
Area forecast discussion
National Weather Service Greenville-Spartanburg SC
538 PM EST Fri Nov 15 2019
a surface low pressure center will linger along the southeast
coastline through Saturday before moving away to the northeast on
Sunday. A couple of weak cold fronts move through the region Monday
and Tuesday. High pressure builds in on Wednesday into Thursday.
Near term /through Saturday/...
as of 535 pm: minor adjustments made to temperatures to coincide
with the latest trends, as the rest of the near term forecast
remains on track.
Previous discussion: a steady rain shield continues to lift
northward over the Piedmont of the Carolinas while also drifting off
to the east as cyclogenesis is underway off the coast, leaving
behind an area of more intermittent light rain showers in the
deformation zone generally along/S of I-85. The sub-cloud layer
across the region remains remarkably dry, so much of the precip was
either very light or only sprinkles. Temps will remain cool,
particularly over the Charlotte Metro area.
Over the next 24 hours, an upper low over MS/Alabama will slowly rotate
past to our south tonight and offshore Saturday. The track of the
low will result in a slow evolution of what we are already observing
today, that is to say, patches of light rain and sprinkles over
the south and east, dry to the north and west, and a tight gradient
of precip probability where an axis of dilatation lies across the
middle of the fcst area. In the south/east area, generally bounded
by I-85, we might see a decrease in precip coverage this evening
as the sfc low moves away off the NC coast, but an increase toward
Saturday morning as the upper low makes its closest pass. Temps
will remain cool and precip amounts light. On Saturday, a surge
in precip prob can be expected over the east as a deformation
zone sets up on the northwest side of the upper low while it deepens
offshore. Amounts will still be light. The clouds and precip will
keep temps well below normal again in the I-77 corridor, but partial
clearing in the afternoon over the mtns and western half of the
fcst area suggests a small rebound back in the direction of normal.
Short term /Saturday night through Monday/...
as of 130 PM EST friday: the short term begins Sunday evening with a
cutoff midlevel low off the southeast coast with a deepening
Nor'easter to impact coastal areas. Pops will be moving out of our
eastern zones at the start of the period, though some lingering
light rain or possibly even some brief flurries could fall Saturday
night across the I-77 corridor before the last of the precip exits.
Surface high pressure to the north will dam down the eastern slopes
of the Appalachians but not strongly, and the cold dome may actually
remain to the north of US. Temperatures for Sunday will be quite a
bit warmer than on Saturday, but still below seasonal normals.
Expect a bit of a breeze during the day, again especially in eastern
zones where the pressure gradient between the damming and the
coastal low will be felt most keenly.
Meanwhile a short wave will dive through the center of the country
Sunday night, digging toward the southern Appalachians on Monday.
New guidance is really drying out this system compared to previous
runs, and the no-pop forecast continues. Expect cloud cover still
especially across the mountains and with that and the upper trough
in place, temperatures will continue below normal through the end of
Long term /Monday night through Friday/...
as of 145 PM EST friday: the extended will begin on the heels of one
shortwave Monday night, with another dropping down the deep upper
trough, with the axis to push through during the day Tuesday.
Guidance continues to agree that even this second front will be dry,
so have pulled back on pops. Surface high building in Tuesday night
into Wednesday will modify as it sags south, and downsloping
component to the surface northwest winds on Wednesday will bring afternoon
highs up a few more degrees, though still a couple of degrees below
Moving into the end of the period, a cutoff low will develop in the
Desert Southwest with a strong trough pushing across Canada, with a
split flow pattern between them. Another front will March through
the center of the country, moving toward the southern Appalachians
Thursday. Some disagreement in how much moisture will be available,
with the operational GFS a little slow and wetter than the ECMWF, so
have some low-end pops and a little bit of mix in the mountains at
the very end of the period, but with Post-frontal high temperatures
actually a little warmer with the downsloping, inching back up above
Aviation /00z Saturday through Wednesday/...
at kclt and elsewhere: prevailing VFR conditions through at least
daybreak Saturday. Light rain will persist off and on, but will
probably not result in a visibility reduction until perhaps
the late afternoon or early evening as better forcing moves
through. Expect a bit of a lull overnight, then another round of
light rain Saturday morning as the upper low passes. Meanwhile,
the mtns and NC foothills will likely stay dry. After daybreak, and
MVFR cloud deck could affect kclt, and is more likely than not to
pass overhead during the afternoon, thus the prevailing MVFR. Other
sites are much less likely to have this restriction. Wind will
remain north to NE through the period, and gusty on Saturday from
Outlook: VFR conditions return Saturday night and Sunday.
22-04z 04-10z 10-16z 16-18z
kclt high 100% high 100% high 100% high 94%
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: