Scientific Forecaster Discussion
fxus62 kgsp 232328
Area forecast discussion
National Weather Service Greenville-Spartanburg SC
628 PM EST Thu Nov 23 2017
dry high pressure will remain across the region during the next
couple of days. A fast-moving cold front may bring a few showers to
the mountains by Saturday. Another area of dry high pressure builds
in after the front and will persist into the middle of next week.
Near term /through Friday/...
as of 625 PM EST thursday: fair weather will prevail across the wrn
Carolinas and northeast Georgia for at least the next 24 hours,
courtesy of sfc high pressure over the mid-Atlantic region that
slides off the East Coast on Friday. An upper trof axis will cross
overhead this evening with little fanfare, but the resulting northwest flow
at mid-levels does not extend down to the low levels, which remain
dry anyway. Apart from a small chance of fog in the mtn valleys
early Friday morning, most of the region will remain clear/sunny
through the period. Temps should stay close to normal.
Short term /Friday night through Sunday/...
as of 130 PM EST Thanksgiving day: the period will begin with high
pressure in place underneath weak troughing over the coast, with
another sharp shortwave coming across the Great Lakes. As we move
toward Saturday morning, the Great Lakes trough will deepen and push
east, with the southern reaches of the moisture just making it into
the NC mountains. The front pushes across the area during the day,
getting hung up in the mountains as is typical, but then will move
east of the area by Saturday evening. Not much moisture at all to be
squeezed out of this system, with the GFS and NAM remaining the
wettest of the operational models (and even then it's not all that
impressive). Have continued trend of slight chance pops along the
state line in the middle of the day, but really just a quick shot of
some light showers. Overall, Saturday looks like an incredibly nice
day for most of the area, with highs across the Piedmont in the mid
60s, down to the upper 40s at the mountaintops, really about 2-3
degrees above seasonal normals.
The front passes by and cool high pressure builds in from the west
Saturday night into Sunday. Should see a brief uptick in winds
across the mountains Saturday night as the gradient tightens
somewhat. The cooler airmass will result in temps below normal by
about 2-3 degrees, but again really quite nice for Thanksgiving
Long term /Sunday night through Thursday/...
as of 145 PM EST Thanksgiving day: most of the extended is very
quiet, with a slow warming trend as the high pressure (that begins
to ridge into the area at the end of the short term) moves over the
region and modifies. Troughing will remain dominant over the eastern
Seaboard, though by Tuesday morning ridging will build over the
southern states, moving over the southeast coast by Wednesday. This
plus the low-level southerly flow will allow temperatures to slowly
climb from a few degrees below-normal to start the period to a few
degrees above by Wednesday, with plenty of sun to go with it. Coldest
night looks to be Sunday night in the wake of the weekend front.
As we're enjoying the pleasant weather through the middle of the
work week, a cutoff low over The Rockies will push into the plains,
sliding east through the end of the period. The good thing is that
the GFS has trended much closer with the European model (ecmwf) as far as the overall
look of the mass fields, but it is faster with progression of the
system. It initially has this cutoff low phased with a transient
shortwave crossing the northern tier, while the European model (ecmwf) keeps it its
own entity and doesn't move it into the plains until Wednesday
evening (the GFS has it over the mid-south at this point). The GFS
then keeps the low cut off through the end of the week, whereas the
European model (ecmwf) absorbs it into a digging trough coming out of Canada, and in
general keeps it a little farther north with fewer impacts to our
area. The GFS would bring precip into our area overnight Wednesday
night, keeping activity around through the end of the day Thursday.
Have delayed onset of pops and have kept pops much lower than
guidance given these uncertainties. Also, with forecast lows in the
mid 30s Wednesday night across the mountains, this might lead to a
little mixed p-type in these areas, so have kept some light
rain/snow mix in the forecast.
Aviation /00z Friday through Tuesday/...
at kclt and elsewhere: other than perhaps some patchy fog across the
valleys of southwest NC (i.E., Southwest of kavl), VFR is expected
to persist through the period. In fact skies should generally remain
sky clear. Winds are expected to be 3 kts or less through the period.
Directions may favor NE through Fri morning, then perhaps southeast during
Outlook: expect mainly VFR through the forecast period as dry/cool
23-05z 05-11z 11-17z 17-18z
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: