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fxus62 kgsp 130545 

Area forecast discussion
National Weather Service Greenville-Spartanburg SC
1245 am EST Wed Nov 13 2019

dry and very cold high pressure will settle over the region through
Thursday. A low pressure system developing along the Gulf Coast will
increase rain chances for the end of the work week through the
weekend, especially for the eastern half of the forecast area.


Near term /through today/...
as of 1240 am: forecast on track with no updates outside of aviation
needed at this time.

Otherwise the very cold air mass continues to build in across the
area. Still some flurries and clouds across the mountains this
evening in the moist, northwesterly flow. However, Sat pix showing the clouds
beginning to shrink in area, and this should continue through the
night with flurries ending. With temperatures dropping quickly thru
the evening, a flash freeze remains a concern for any areas that
don't dry out across the higher terrain, especially above 3000 feet
or so. Thus, the Winter Weather Advisory for the higher terrain will
continue thru tomorrow morning. For the remainder of the fcst area,
most Road surfaces should have dried out. Northwest winds beginning to drop
off, but very cold wind chill values still seen across the
mountains, with cold but above advisory level wind chills elsewhere.
Low temps will approach record low values, and may eclipse them.
Otherwise, cold and dry high pressure will settle over the region
tomorrow with with temps running 20 to 25 degrees below normal for


Short term /tonight through Saturday night/...
as of 200 PM EST tuesday: a cold and dry Arctic airmass will remain
over the area on Thursday, with Max and min temperatures still 15-20
degrees below average. A surface high pressure system moving off the
NE coast will still exert some influence over the area on Thursday,
though cloud cover will increase through the day as Gulf moisture
filters in at mid-levels as an upper trough approaches. Though the
track of a developing Gulf surface low has been uncertain for the
past few days, guidance has some into better agreement that it will
lift northeastward right along the coast of the Carolinas, close
enough inland that the eastern half of our forecast area will
receive plenty of moisture on the back side of the low. Though exact
timing is uncertain, pops ramp up in earnest starting 00z Friday to
high-end chance overnight.

On Friday, the upper trough base and a closing upper low will swing
towards the forecast area, placing the eastern half of the County Warning Area in an
area of upper diffluence/divergence aloft. This has the potential to
increase rainfall rates/coverage during the morning on Friday,
though again exact timing and quantitative precipitation forecast totals are still challenging to
pin down. The good news is that it appears that the coldest air and
the moisture will not see enough overlap in our area to produce any
winter weather through the event. There is some suggestion that as
the upper low crosses the forecast area on Saturday, there may be
some quantitative precipitation forecast response in the southern zones of our County Warning Area despite the main
surface coastal low lifting up towards the northeast. The Prospect
of this last bit of upper forcing from the upper low producing quantitative precipitation forecast
response seems dubious at best, though the European model (ecmwf) has hung onto it
for the past few model runs. The public forecast therefore won't
advertise it, but this could be a tricky part of the forecast over
the next couple days. Max and min temperatures will rebound Friday
and Saturday to levels just about 5 degrees below average


Long term /Sunday through Tuesday/...
as of 155 PM EST tuesday: the departing, closed low off the
southeast coastline on Saturday night should move safely away over
the offshore waters through Sunday. Meanwhile, a longwave trough
will carve out from The Rockies to the plains, with shallow
ridging in place over the forecast area through Sunday.
Generally dry profiles and moderating temperatures will result,
but a lingering cloud band could persist into Sunday along/east
of I-77 depending on moisture wrapping west from the offshore

The deepening trough will likely go neutral tilt near the
Mississippi River valley on Monday, then lift across the southeast
through Tuesday. A 100+ kt upper jet rounding the approaching trough
Sunday night into Monday should produce divergence forcing mainly
over the coastal plain of the Carolinas. Moisture return east of the
trough is highly uncertain. There are some hints of weak, transient,
moist upglide Monday or Monday night, but this might just produce
clouds and little to no precipitation. Will thus keep pops capped in
the slight chance range early next week. Temperatures will continue
to slowly rebound, but generally remain 5 to 10 degrees below climo
on Monday and at least a category below on Tuesday.


Aviation /06z Wednesday through Sunday/...
at kclt and elsewhere: VFR conds and light winds will prevail
thru the taf period as high pressure settles into the region.
Asheville gusts are expected to drop rapidly over the next few
hours. Otherwise a few low end gusts are possible just about
anywhere after sunrise through 18z. Return flow behind the high may
support few/sct MVFR and high cigs near the end of the taf period.

Outlook: a low pressure system may bring rain and associated
restrictions to the area later Thursday into Friday. VFR expected
to return sometime this weekend.

Confidence table...

05-11z 11-17z 17-23z 23-00z
kclt high 100% low 55% high 89% high 100%
kgsp high 100% Med 70% high 100% high 100%
kavl high 100% high 95% high 94% high 95%
khky high 100% high 95% high 100% high 100%
kgmu high 100% Med 75% high 100% high 100%
kand high 100% high 100% high 89% 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:



records for 11-13
maximum temperature min temperature
station high low high low
------- ---------- ---------- ---------- ----------
kavl 75 1964 32 1906 58 1929 13 1911
kclt 81 1931 40 1920 63 1879 21 2013
kgsp 81 1909 40 1920 61 1929 20 1906

Records for 11-14

Maximum temperature min temperature
station high low high low
------- ---------- ---------- ---------- ----------
kavl 76 1999 32 1906 60 1929 16 1986
kclt 80 1879 37 1976 63 1961 21 2013
kgsp 79 2007 36 1976 62 1929 20 1906


Gsp watches/warnings/advisories...
NC...Winter Weather Advisory until 7 am EST this morning for ncz033-



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