Area Forecast Discussion
Issued by NWS Greer, SC

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349
FXUS62 KGSP 251504
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1104 AM EDT Mon Sep 25 2017

.SYNOPSIS...
Dry and warm high pressure will remain across the region through the
middle of week...while Hurricane Maria is forecast to remain off the
East Coast. A weak cold front will sweep across the area beginning
late Thursday through early Saturday, bringing drier and much cooler
air to the area over the upcoming weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 1055 AM EDT: Rather thick cirrus has limited insolation
somewhat this morning, keeping observed temperatures running a bit
cooler than forecast temps. However, morning sounding thickness and
850 mb model temp values today suggest that we should reach or
exceed yesterday maxes, so the going forecast looks good.

Otherwise, mean upper ridging will persist along the East Coast
through the period, with only the slow northward movement of
Tropical Cyclone Maria off the coastal Carolinas to disrupt the
larger scale pattern. Streamline trajectories originating from Maria
will continue to support SCT/BKN, mainly thin cirrus across our area
through part of today, but this should have minimal impact upon
temperatures. Persistent NE low level flow will continue to promote
a rather dry boundary layer, while large scale subsidence will yield
poor mid-level lapse rates. Thus, chances for deep convection later
today are virtually nil. Min temps tonight should once again be
roughly 5 degrees above normal.

&&

.SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/...
As of 225 AM Monday: Unseasonably warm and dry conds continue thru
the short range period. Strong h5 ridging to the north will interact
with the subs region of TC Maria and create stg downward supressive
motion across the FA. Low level moisture will be hard to come by as
llvl winds remain n/ly to ne/ly. Layers of Ci will round Maria and
cross overhead thru the period esp across the ern zones...but these
clouds will be too shallow to prevent max temps from reaching arnd
10 degrees abv normal each day. No good chance for convec during the
timeframe with fair-wx Cu the likely cloud type while the subs
inversion persists arnd h8. Thus...no precip is fcst and little in
the way of morning fg/br can be expected even across the mtn
valleys. There is a chance of afternoon low- end gusts with modest
momentum transfers east nearer Maria both Tue and Wed.

&&

.LONG TERM /THURSDAY THROUGH SUNDAY/...
As of 250 AM Monday: Another well above normal temperature day is in
store Thu as an h5 ridge redevelops to the SW in the wake of TC
Maria, which will be heading away from the NC shore. This ridge will
be short lived however as h5 heights begin to fall late in day in
response to strong energy traversing the mean flow across the nrn
CONUS.

A moisture deficient cold front will advance toward the NC
mtns late Thu and with some measure of sw/ly mech lift a few -shra
may develop across the cent/srn NC mtns. Pops are held at slight
during this time as it will be hard to get good coverage of deep
clouds given the limited amount of moisture. The front crosses into
the mtns Thu night and early Fri with little fanfare. By the
afternoon...lift ahead of the front and a little better moisture
pooling will allow for iaol -shra across the NC mtns...Upstate and
NE GA...with little potential for the NC fthills and piedmont
regions. The airmass ahead of the front will be non-conducive for
deep convec however as warm dry air remains abv h7 and cloud
cover increases limiting max temps to seasonal levels. So...will not
expect thunder Fri thru FROPA early Sat.

A definitive fall-like cP airmass will move in behind the front Sat
and persist into early next week. Very dry air indicated by PWATS
arnd 0.5 inches and max temps held 5-8 degrees below normal will
make for very pleasant conds as we move into Oct.

&&

.AVIATION /15Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: VFR conditions are expected through at least
the evening at most terminals, with mainly SCT to BKN cirrus, with
mtn valley fog/low stratus possible again Tue morning. Light NE
winds will increase to around 10 kts by late morning, with some
gusts in the mid/upper teens possible in the Piedmont this
afternoon. Winds diminish again this evening.

Outlook: Dry conditions are expected most of the week. Under mostly
clear skies and calm conditions, fog and/or low stratus are possible
in the mtn valleys each of the next few mornings. A mostly dry cold
front will cross the region late in the week.

Confidence Table...

            15-21Z        21-03Z        03-09Z        09-12Z
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%     Med   72%
KHKY       High 100%     High 100%     High 100%     High  94%
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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...SBK
NEAR TERM...HG/JDL
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...HG/JDL



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