FXUS62 KGSP 250613

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
213 AM EDT Wed Apr 25 2018

A slowly moving low pressure system exits our region in mid week
and gives our region brief drying. Another moist area of low
pressure crosses the region Thursday through early Friday. High
pressure builds across our area from this weekend into early next


As of 155 AM: The last band of showers anticipated to impact the
piedmont is lifting north of Charlotte early this morning. Any
lingering hydro issues should be along the Rocky River area and
along the Catawba River chain where stages and pool levels will only
slow fall through the day.

Otherwise, water vapor imagery shows the closed upper low crossing
the central and southern Appalachians this morning. Northwest winds
will gradually pick up behind the departing surface low center now
analyzed over the central NC piedmont. Some shower coverage may
persist along the I-40 corridor in the moist northerly flow behind
the surface low today, but rates will be much less than previously.
Anticipate that moist northwest flow may also keep upslope showers
going along the TN line through the day. Shallow ridging will also
develop over the region today as heights fall strongly across the
southern plains. This upstream system will deepen over the MS River
Valley tonight. Persistent near-surface moisture will permit some
fog and low clouds to form both this morning and again tonight
around the region. Max temps will be a touch below climo today, with
mins about a category above climo tonight.


As of 220 PM EDT Tuesday: the short term fcst picks up at 00z on
Thursday with a brief flattening of the upper pattern before another
upper trof digs down across Southern Arkansas. The trof axis is
expected to lift up and over the CWFA late Thurs into early Fri as
another trof dives down the backside of the broader upper trof.
This second trof axis is not expected to reach the fcst area until
early Sat, which is just beyond the short term period. At the sfc,
the large low that has been impacting our region will finally lift
northward and over New England. In the low's wake, weak high pressure
will briefly move over the area from the northwest. The high will be
short-lived as another low develops to our west and approaches the
fcst area Thurs afternoon. The operational models are now in much
better agreement with the timing and placement of this low. It is
expected to move over the CWFA late Thurs/early Fri and lift north
of the area late Friday. As for the sensible fcst, PoPs were increased
for the later half of Thurs as the deeper moisture associated with
the low overspreads the CWFA. They remain high thru early Fri morning
and then taper off during the rest of the day. Some sfc-based instability
is present Thurs afternoon/evening, especially over our southern and
eastern zones, so isolated to scattered thunder is included over those
areas. High temps will be about a category below normal for Thurs and
near normal for Fri. Lows are expected to remain a few degrees above
climatology both days.


As of 230 PM Tuesday: The extended forecast starts at 00z Saturday
with yet another potent shortwave trough rounding the base of the
mean longwave trough over the Southeast states. The medium range
guidance is still not in good agreement on the details of this wave.
The 12z EC still is the further south and least phased of the
deterministic models. It takes the wave all way to the FL Panhandle.
This results in a relatively dry soln. The 12z GFS still on the
wetter side of guidance, keeping showery wx for the area on Saturday
with the shortwave tracking right thru the Carolinas. For now, the
WPC preference is toward the EC soln, and results in only SLGT CHC
PoPs for Saturday. Temps will be near normal.

From Sunday onward, conditions look dry with temps warming above
normal for the start of next week. The eastern trough should finally
start to shift east and an upper ridge will build in from the west.
By next Tuesday, the models are in decent agreement on a fairly
amplified western trough and eastern ridge pattern across the
country. Sfc high pressure will dominate our weather for Monday and



At KCLT and Elsewhere: Showers should impact mainly KHKY this
morning, with the lifting band generally north of KCLT. Developing
IFR to LIFR ceilings will be the main concern given the abundant
near-surface moisture. The conditions may be quite variable however,
with mixing across KHKY in showers, and a light downsloping NW flow
at times farther to the south. Anticipate recovery to VFR throughout
from 13Z to 15Z today. Winds should remain generally N of W and be
become gusty at times at KAVL.

Outlook: Moisture will return quickly to the region on Thursday
ahead of a vigorous southern tier low pressure system. Rain showers
and associated restrictions are likely into Thursday night. A drier
cold front will approach from the northwest early in the weekend.

Confidence Table...

06-12Z 12-18Z 18-24Z 00-06Z
KCLT Med 73% High 96% High 100% High 100%
KGSP Med 74% High 97% High 100% High 100%
KAVL High 85% High 87% High 99% High 80%
KHKY Low 53% Med 74% 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:





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