Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 171822
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
222 PM EDT Tue Apr 17 2018

.SYNOPSIS...
Temperatures will warm once again through midweek, but then another
cold front will move through the area on Wednesday night, bringing a
chance of rain to the mountains. Dry and seasonal conditions are
expected for the end of the week.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
As of 2pm EDT Tuesday:  Northwesterly flow aloft and at the surface
continues today on the back side of exiting major system.  Cool and
dry advection has dried airmass considerably with surface dewpoints
down into the low 30s and skies clear.  Gusty surface winds will
continue in the mountains, and decline diurnally overnight outside
the mountains. 850mb flow continues overnight at 30 to 45kts, with a
brief lull Wednesday morning before increasing again Wednesday
afternoon as upstream system approaches the region. Current wind
advisory still looks good to expire at 8pm should some decoupling
occur as models currently indicate.  Upstream system will bring some
scattered light precipitation to the mountains late on Wednesday.
Precipitation should be fairly light with this due to dry airmass.
Temperatures will continue to warm with highs Wednesday 5 to 10
degrees above normal and lows Wednesday above freezing at all
locations, including mountain peaks.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
As of 154 PM EDT Tuesday: The passage of a re-inforcing cold front
Wednesday night will be the primary concern for the latter half
of the week. The front will be driven quickly south/east by the
dampening upper low moving across the Gt Lakes region and should
not reach the mtns until after 00Z Thursday. The front has some
decent low level convergence, but lacks moisture above 700 mb and
also lacks much in the way of mid/upper forcing as it moves across
the region. Expect the frontal passage to account for a chance
of showers close to the TN border, where upslope flow will also
contribute, but very little chance will exist outside the mtns
where the low level forcing will be much weaker. Temps will be
warm enough that all the precip will remain liquid in most places,
but a few wet flakes could mix in around daybreak Thursday above
5k feet as the small chance of precip ends. The upper trof axis
will cross the region on Thursday, which should be another breezy
and dry day. The rest of the fcst will be relatively benign, with
high pressure building in from the NW. The only other issue will
be frost/freeze potential over the mtns early Friday morning,
but as it stands right now, wind looks like it will remain too
stirred up for frost across all but sheltered locations.

&&

.LONG TERM /FRIDAY NIGHT THROUGH MONDAY/...
As of 220 PM EDT Tuesday: A mild and dry Saturday expected as high
pressure builds in from the north. Moisture return ahead of an
approaching low pressure system along the Gulf Coast could bring
some light rain into the western sections of the CWFA late in the
day on Sunday. Temps both days will be a few degrees below normal.

The upper low associated with the surface low will move across the
Lower MS Valley Monday and slowly across the Gulf Coast states
Tuesday as an upper trough crosses the Mid Atlantic. The surface
high that built in over the weekend remains in a cold air damming
pattern both days as the surface low slowly moves east along the
Gulf Coast. The 12Z GFS and Canadian models have trended southward
with the track of the low similar to the 00Z ECMWF. The Canadian and
ECMWF are both basically dry through the period with the low well
south of the area. The GFS is not as far south and keeps precip in
place as moist upglide develops Monday and continues into Tuesday.
Didn`t want to remove PoP completely given the uncertainty, but did
drop any likely PoP across the area back into the chance range. The
presence or lack of precip will also have an effect on temps. Highs
would be much cooler with precip falling into the damming high both
days. For now, have lows near normal and highs 5 to 10 degrees below
normal.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
At KCLT and elsewhere:  Generally good VFR conditions with gusty
winds this afternoon and Wednesday afternoon. Westerly winds most
areas will decline after dark due to boundary layer decoupling,
except at higher elevations like KAVL.  Winds will pick-up again
during the day on Wednesday, backing to be more southwesterly as
upstream system approaches from the west. Wind gusts today and
tomorrow are expected to peak at aerodromes at around 25kts. Skies
will remain mostly clear with very few cumulus this afternoon, and
some high clouds entering from the west on Wednesday.

Outlook: Mostly dry conditions will continue for the rest of the
week. A dry cold front will arrive from the west on Thursday, with
some scattered restrictions possible and some showers in the
mountains.  Winds will be gusty at times in the afternoon through
Thursday.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
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:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Wind Advisory until 8 PM EDT this evening for NCZ033-048>052-
     058-059-062>064.
SC...None.

&&

$$
SYNOPSIS...TDP
NEAR TERM...WJM
SHORT TERM...PM
LONG TERM...RWH
AVIATION...WJM



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