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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KGSP 070656
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
256 AM EDT Fri May 7 2021

.SYNOPSIS...
A cold front will cross the region from the west today. Drier high
pressure will return over the weekend. Another cold front will
approach from the west Sunday night and then move slowly across
the region Monday into early Tuesday. High pressure will set up
by mid- week, but with a moist low pressure system returning from
the west Wednesday night into Thursday.

&&

.NEAR TERM /THROUGH TONIGHT/...
An upper level trof will continue to cross the area thru the period.
The associated low freezing levels is helping to produce small hail
in a cell across Cabarrus Co and there could be periodic weak storms
developing overnight as upper energy remains quite strong, altho
moisture is limited. With continued upslope flow, expect -shra
across the wrn NC mtns this morning lingering into the early
afternoon. Also, a few -snsh are possible across elevations abv 5
Kft with limited or no accum.

Expect a dry and breezy day today as an area of hipres builds across
the Deep South and produces a fairly tight p/grad across the FA
during max mixing. Soundings continue to indicate deep mxing up 8
Kft and winds at the top of the mixed layer will be arnd 35 kts.
Don/t expect winds of that magnitude mixing to the sfc as winds
decrease abt 10-15 kts toward the sfc, but with good monentum
transfer due to uniform flow, winds should gust into the 25-30 mph
range across most areas. Gusts approaching 40 kts over the higher NC
mtn elevations are also likely and will mention winds and possible
trees down in the HWO. With the deep mixing will also come low sfc
td/s. Went on the low side of guidance and vertically mixed lower
values thru the afternoon. Max temps will struggle a cat or so below
normal in CAA flow, so afternoon RH values will be tricky. For now,
believe RH levels will lower into the 25-30 percent range. A FDS is
in effect for the non/mtns of NC and will likely expend this to
include the SC zones and portions of NE GA. Mins tonight will drop
to arnd 10 degrees below normal as colder Canadian air continues to
advect into the region.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 300 AM EDT Friday: By the start of the short-term on Saturday
morning, a broad 500mb trough is lifting out of the Mid-Atlantic
as it pushes offshore, and heights over the Carolinas are rapidly
rising.  A stout ridge is positioned over the Central Plains and
building into the eastern CONUS.  At the surface, high pressure
creeps into the Southeast, with the center of the high passing well
south of our CWA...through south/central MS/AL/GA, from the looks of
things.  So, we`ll maintain steady westerly surface flow throughout
Saturday, remaining mostly dry except on the northern and western
fringes of the high, especially the Appalachians where upslope flow
will produce some light, scattered showers as NW flow interacts with
moisture associated with a developing low to the west.  So, PoPs
should move from west to east into the forecast area.  Expecting a
high a few degrees below normal owing to deep CAA associated with
the continued NW flow.

Saturday night, flow becomes more southerly as the high passes
east of us, and so moisture advection will pick up and moisten
the environment ahead of an advancing cold front Sunday night.
This front looks to be on our doorstep by Sunday at daybreak, with
PoPs already ramping up by then.  Little chance of thunder with
this system; with poor fropa timing and limited moisture, we won`t
see much instability so the likely scenario is just some showers.
Thanks to the reversed surface flow and decent insolation for much
of the day, Sunday`s high will jump to barely above-normal.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 230 am EDT Friday: A northern stream trough will move from the
Great Lakes to the East Coast Monday through Tuesday. This system
will push a cold front through the region, but with somewhat limited
deeper moisture along the passing frontal zone. PoPs will be fairly
high in western sections Monday, but with some drying crossing the
mountains and points east through Monday night. Additional downslope
drying will occur on Tuesday, with PoPs limited mainly to southern
tier sections as the boundary departs. Near climo temperatures on
Monday will cool at least a category under cold advection on Tuesday.

A flat upper ridge will transit the Appalachians Wednesday, with
surface high pressure crossing the central Appalachians and building
southward across the forecast area. Cool thicknesses will lead to
well below climo temperatures. There is reasonably good consensus on
the next digging upper wave approaching from the Mississippi Valley
starting Wednesday night. Abundant deeper moisture ahead of this
system will return Wednesday night and likely cross the area on
Thursday. Moist upglide will keep temperatures on the cool side due
to in situ cold air damming from the departing offshore surface
high. Heavy rainfall will be possible for our area, depending on the
position of a surface wave wrapping toward the southeast coast along
the stalled wedge boundary. Instability could get uncovered from the
southern tier during the afternoon hours, with elevated instability
possible throughout. Will shade to higher PoPs and lower max temps
given the wedge like setup Thursday.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: An upper level trof crossing the area will
generate a few brief -shra and possibly some thunder this morning
possibly at KAVL and east toward KCLT. Otherwise, VFR conds and
expect the atmos to remain mixed overnight. Deeper mixing will
develop by mid-morning and nw/ly gusts are likely in the 20-25 kt
range thru the afternoon before tapering off arnd 00z, except at KAVL
where low-end to moderate gusts will continue thru the period.

Outlook: Predominately VFR conditions are expected thru the
weekend. The next system to bring restrictions is looking like it
will arrive on Monday of next week.

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  97%     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 are available at
the following link:

www.weather.gov/gsp/aviation

&&

.FIRE WEATHER...
Steep lapse rates underneath a passing shortwave trough will allow
very good mixing this afternoon and dewpoints could drop more than
most model guidance suggests. Modest flow in the mid-levels will be
brought down to the surface as gusts potentially range between 25-30
mph. While fuels remain moist following recent heavy rains, the
meteorological conditions are marginally conducive to elevated fire
danger. Thus, in coordination with land managers a Fire Danger
Statement will be issued for most areas outside the mtns.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
GA...None.
NC...Fire Danger Statement from noon EDT today through this evening
     for NCZ035>037-056-057-068>072-082-501>510.
SC...None.
-- End Changed Discussion --

&&

$$
SYNOPSIS...HG
NEAR TERM...SBK
SHORT TERM...MPR
LONG TERM...HG
AVIATION...SBK
FIRE WEATHER...GSP