Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 170726

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
326 AM EDT Tue Apr 17 2018

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.


As of 315 AM Tuesday: no significant changes since the last update a few
hours ago. The last remaining pockets of light precip appear to have dried
up as the deeper moisture gradually moves farther north. The latest IR
satellite imagery shows mostly clear skies over the southern 2/3 of the
CWFA with lingering stratocu in the 3 to 5kft range over the rest of the
fcst area. Temps have cooled faster than expected and are already hovering
around freezing over parts of the Upstate and Piedmont, although values
range from the upper 30s to the lower 30s. Otherwise, after sunrise temps
should quickly rebound, warming to around 70 degrees across the Upstate
and NW Piedmont, and into the 50s/60s across the mountains. Broad high
pressure over the Gulf of Mexico will keep stout 850mb flow over the area
with strong wind gusts expected again this afternoon and into the evening.
Gusts should taper off later tonight as the pressure gradient weakens and
bndy layer mixing subsides. With heights rising and thicknesses increasing,
we don`t expect any frost/freeze concerns for early Wed with low temps
remaining in the 40s and 50s.


As of 230 AM EDT Tuesday: Shortwave ridging will be in place just to
our west with the departing upper low over New England continuing to
lift out, and another developing upper low working its way down the
MO Valley. With strengthening surface low over the Lower MO Valley
at the beginning of the period, surface pressure gradient will
remain strong and expect breezy conditions with yet again on
Wednesday, with strong winds out of the SW a good 15-20mph.
Temperatures temperatures will rise again a good 5 or so degrees
above seasonal normals in the low-level WAA regime and with
increasing thicknesses. The surface low will work its way east
across the Midwest Wednesday into Wednesday night, dragging a cold
front with it, and though the system will be mainly dry, still looks
like slight to low chance pops Wednesday night are warranted. Behind
the front on Thursday temps will be knocked down almost 10 degrees
from those on Wednesday, still breezy but with winds WNW (with
typical gap wind gusts were applicable). Well below normal Thursday
night and will likely have to consider some freeze products for the
NC mountain zones that are turned on; likely at this point too
breezy for frost concerns but will continue to reevaluate.


As of 300 AM EDT Tuesday: Very quiet to start the extended, with a
really lovely weekend in store across the area. High pressure over
the Northern Plains will work east as the omega-looking wavetrain
pattern progresses. Strong upper ridge over the Plains will slowly
damp during the weekend but mean troughing will remain in place over
our area through the period. Desert Southwest closed low will fill
somewhat as it moves east toward the Southern Plains early Sunday,
taking a bit of a southerly track underneath the ridge. Temperatures
will be 4-5 degrees below seasonal normal, but very pleasant and
dry conditions expected through the weekend.

The Southern Plains upper low and associated surface low will lift
moisture northward from the Gulf into the Lower MS Valley on Sunday,
as the New England upper trough continues to dominate. The upper
ridge forced north over Canada will set up a nicely confluent flow
over Ontario and Quebec. The Northern Plains surface high will
translate east over the Great Lakes Sunday and begin ridging down
the Eastern Seaboard Monday in a fairly strong Classical damming
pattern, with diabatic enhancement as moisture lifts into the Deep
South from the approaching surface low. Global models are trending
more south with the track of the surface low, more over the Gulf
Coast. Also, while 00z GFS and 12z ECMWF still bring/brought precip
up into our area, but new 00z ECMWF is now completely dry for us
Monday into Tuesday, and so to reflect that uncertainty have delayed
onset of pops and then reduced them accordingly. Temperatures on
Monday will definitely feel like we`re in a wedge, with current
guidance 10 degrees below normal.


At KCLT and elsewhere: Expect VFR conditions to prevail through the
06z TAF period. Most sites are already reporting clear skies with KCLT
and KAVL still reporting FEW to SCT low clouds. All sites should remain
mostly clear thru the period with KAVL expected to maintain SCT cigs in
the 3000 to 4000ft range for a few more hours and then clear out. Winds
have begun to diminish across the lower elevations over the past couple
of hours and they should remain below roughly 10kts thru most of the
morning. The only exception is KAVL, where I kept gusts of about 25kts
in the taf thru 00z. After that, gusts should subside for the last 4 to
6 hrs of the period. Otherwise, winds will remain out of the W to SW
in the 10 to 15kt range with gusts up to about 25 kts and subside after
approximately 00Z.

Outlook: Dry and cool conditions will continue into mid week. A dry cold
front will arrive from the west on Thursday, with some scattered restrictions

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:


GA...Freeze Warning until 9 AM EDT this morning for GAZ010.
NC...Frost Advisory until 9 AM EDT this morning for NCZ035>037-056-
     Freeze Warning until 9 AM EDT this morning for NCZ048-051>053-
     Wind Advisory until 8 PM EDT this evening for NCZ033-048>052-
SC...Frost Advisory until 9 AM EDT this morning for SCZ001>003-


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