Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 250824

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
424 AM EDT Thu Apr 25 2019

A disturbance pushing into the region will lead to scattered shower
and thunderstorm activity at times late today into Friday. A ridge
building aloft will support generally quiet weather this weekend
into early next week.


As of 335 AM EDT Thursday: Ridge axis starts the day over the area
but moves east as an upper low opens and moves toward the area from
the west. Southwesterly flow increases as a result with increasing
mid and high clouds, and eventually developing Cu or StratoCu. Low
level moisture remains scant until late in the day across the
mountains. Therefore, precip chances only slowly increase across the
mountains during the afternoon. Expect gusty southwest winds across
the area today with highs "only" 10 degrees above normal.

A northern stream short wave begins to phase with the southern
stream short wave as they approach the area from the west tonight.
This slows the system slightly as the combined wave begins to take
on a slight negative tilt by the end of the period. The associated
cold front ends up on the forecast area`s doorstep by then. Deep
moisture and forcing increase after midnight, but instability
remains weak. Show a slow but steady increase in PoP overnight with
likely PoP west and high chance east by daybreak. Have not mentioned
any thunderstorms tonight given the weak instability. That said, the
forcing could overcome this and isolated storms are possible. QPF
amounts could reach the moderate range, up to a half an inch, west
of the French Broad Valley after midnight, but most locations will
see a quarter of an inch or less, with a tenth of an inch or less
for the I-40 and I-77 corridors. After lull in wind gusts outside of
the mountains this evening, gusts pick back up overnight. Gusts
continue across the mountains, especially the higher elevations
through the night, but should remain below advisory levels. Lows
will be 10 to 15 degrees above normal.


As of 335 AM Thursday: Model guidance continues to show the southern
stream disturbance merging across the region as a cold (more of a
cool) front pushes into the region from the west. As the southern
stream energy rides north along the front it will bring much of the
mid and upper level moisture along with it, leaving partly cloudy
skies across much of NE GA through the Upstate of SC and into
portions of the NC Piedmont by Friday afternoon. This pattern will
likely support shower activity gradually coming to an end from SW to
NE late morning into the afternoon. With diurnal heating, expect
sufficient instability for isolated showers and thunderstorms during
the afternoon hours, focused east of the mountains. Strong to
isolated severe thunderstorms are possible with gusty winds possibly
from microbursts being the main threat (small hail also possible)
for eastern portions (see SPC marginal risk) of the forecast area
including Charlotte from about mid afternoon through early evening.
The main ingredients which are supportive of potentially damaging
wind gusts include sufficient CAPE and lingering llvl moisture
combining with steep llvl lapse rates and rapidly descending, drying
mid levels (DCAPE in excess of 1000), and increasing llvl shear.
Gusty winds in general are expected across the area where gusts of
25 to 35 mph will be common due to steep lapse rate/deep mixing
layer and increasing llvl shear. The progressive nature of this
system and lack of deep moisture should limit hydro concerns,
although brief heavy rainfall is possible in thunderstorms. Gusty
northwest winds focused across the mountains and clearing conds are
expected Friday evening into the night as high pressure gradually
pushes into the region. Highs Friday will be in the 60s to mid 60s,
falling into the 40s to near 50 that night. Sunny skies will support
seasonable temperatures in the upper 60s to mid 70s. A cold front
pushing through the region Sunday night will bring increasing clouds
and isolated showers focused across the mountains. Lows will rebound
some Saturday night with lows into the 50s.


As of 420 AM Wed: Relative quiet weather is expected during the
extended period. The weak cold front the pushed into the region
Saturday night will stall along or just north of the region before a
fairly impressive positively tilted ridge stemming from the Gulf of
Mexico builds into the region, assisting the front back to the north
in the form of a warm front. Southwest flow around the ridge will
support gradually increasing moisture and high clouds at times.
Instability and moisture may be enough for diurnally driven
convection focused over the mountains by Tuesday afternoon, possibly
more widespread Wednesday as some mid level energy rides overtop the
ridge. Mostly sunny skies and increasing 500 mb heights will support
summer-like temperatures with widespread highs in the low to mid 80
by early next week with lows in the 50s to low 60s.


At KCLT and elsewhere: VFR conds thru most of the TAF period, but
with lowering cigs and increasing precip chances late. Moisture and
clouds increase steadily through the period as a cold front
approaches from the west. Expect southwesterly gusts again today
with good mixing. Gusts diminish this evening. Have included PROB30
for showers and MVFR late in the period as as precip chances
increase as the front moves in.

Outlook: Periods of showers and thunderstorms associated with a cold
front bring the potential for restrictions Friday. VFR returns for
the weekend into Tuesday as high pressure builds in behind the cold

Confidence Table...

            08-14Z        14-20Z        20-02Z        02-06Z
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:




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