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Area forecast discussion 
National Weather Service Greenville-Spartanburg SC
309 am EDT Mon Oct 24 2016

a dry cold front will cross the Carolinas today from the northwest.
In the front's wake, strong high pressure will quickly build back
over the region and linger through the middle of the week. Another
frontal passage is expected on Thursday.


Near term /through tonight/...
as of 130 am...looks quiet through daybreak as dry high pressure
lingers across the deep south. Clear conditions with light winds
expected, which could allow some fog to develop in the little Tennessee
River valley. Low temperatures across the mtns will reflect an inverse
lapse rate, ranging from around 40 within the valleys to the mid 40s
across the ridges.

Not much change to earlier thinking for the next 24 hours. A dry
backdoor cold front is expected to slip southward across the NC
foothills and Piedmont during the late morning to midday period,
passing across upstate SC during the early afternoon. Sfc winds will
veer as the front approaches during the morning hours. Only a
few cirrus clouds will be possible with the passage of the front.
The timing of weak cold air advection in the wake of the front will favor temps
climbing up to two categories above normal. High pressure will build
back in from the northwest behind the front tonight, but temps are not
expected to be as cool as the air mass was behind the last front. At
this point, the frost threat looks minimal.


Short term /Tuesday through Wednesday night/...
as of 305 am Monday, the short term fcst picks up at 12z on Tuesday
with broad upper trofing gradually moving off the New England coast
as upper ridging slowly spreads farther east in the trof's wake. The
guidance suggests that the ridge will deamplify as it spreads
eastward resulting in a more zonal pattern over the fcst area for
much of the period. By early thurs, another upper trof will begin to
develop to our northwest as the upper ridge amplifies over the western
Continental U.S.. at the sfc, a reinforcing Canadian high will be spreading
over the region by early Tuesday bringing more dry air to the
Carolinas. As the center of the high slides farther southeast late tues and
into Wed, a weak wedge pattern will briefly develop over the County warning forecast area.
This pattern won't persist for long as the next cold front will move
into the area by early thurs and break down any lingering wedge
bndy. As for the sensible fcst, we can expect a dry fcst thru
Wednesday with pops ramping up from the west as the front approaches
early Thursday. Temps should remain near, if not just below, normal
for late October on tues and Wed.


Long term /Thursday through Sunday/...
as of 255 am monday: the medium range fcst picks up at 12z on
Thursday with a fairly progressive upper lvl pattern expected thru
the period. By early thurs, an upper trof axis will be crossing to
our north as strong upper ridging dominates the western Continental U.S..
as we move into Friday, the upper trof is expected to lift NE and
up over New England as more zonal flow briefly sets up over our
region. Beyond this point, the long range models differ significantly
wrt the upper pattern evolution. The latest 00z GFS digs another,
deeper upper trof down across the eastern Continental U.S. Over the weekend
and then develops an embedded 500 mb shortwave in the trof's wake early
Monday. The 12z European model (ecmwf) keeps relatively zonal flow over the southeast
well into Sunday and then generates a stronger looking 500 mb shortwave
over the northern plains and moves it across the fcst area by early

At the sfc, a cold front will be moving into the County warning forecast area from the west
Thursday morning. Models indicate a fairly quick fropa with weak
reinforcing high pressure moving in behind the front by late thurs/
early Friday. Beyond this, the models diverge with the GFS bringing
another cold front down from the Great Lakes on Sat with strong high
pressure overspreading the region after the fropa and lingering well
into next week. The European model (ecmwf) is much slower developing a low and and does
not bring its associated front to our doorstep until late sun/early
Monday. As for the sensible fcst, no significant changes were made
owing to the pattern uncertainty beyond Friday. I kept slight to solid
chance pops for thurs and early Fri with the best chances over the
higher terrain and foothills with forecasted quantitative precipitation forecast amounts remaining below
0.5 inches.


Aviation /07z Monday through Friday/...
at kclt and elsewhere: VFR conditions expected thru taf period.
A dry cold front will slide southward across the western Carolinas
during the day, complicated by the development or presence of a Lee
trof. With little moisture to work with, only a wind shift is
expected with the fropa. Winds will shift from SW to west or west-northwest by
midday, then veer further to northwest Monday evening. The biggest problem
will be a cross-wind at kclt thru the middle part of the day. Have
opted to keep wind direction west-southwest thru much of the daytime hours
because of the Lee trof, with a shift to west-northwest not until 22z based on
the lamp guidance. Only a few wisps of cirrus will stream by from
the west periodically through the period. The other trouble spot
might be kavl. There could be some fog development around daybreak,
but think that will be confined more to the little Tennessee River valley.
Strong winds aloft this morning above a strong temperature inversion
may result in several hours of low level wind shear. Once the
boundary layer deepens, the shear will go away and the wind gusts
will begin, around 16z or so.

Outlook: dry high pressure will persist over the southeast through
Wednesday. Then a fast-moving cold front will cross the area
Thursday or Thursday night, but with limited moisture. Dry
conditions return for next weekend.

Confidence table...

07-13z 13-19z 19-01z 01-06z
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:



Gsp watches/warnings/advisories...


near term...PM
short term...jpt
long term...jpt

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