Webster, North Carolina Weather Forecast Discussion

843
FXUS62 KGSP 131751
AFDGSP
Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
151 PM EDT Sat Sep 13 2025
.SYNOPSIS...
Dry high pressure will persist over the region through the weekend.
A developing low pressure system just off the Carolina coast may
bring rain to our area by the middle of next week.
&&
.NEAR TERM /THROUGH SUNDAY/...
As of midday Saturday, key messages:
1. Slightly more favorable setup for convection Sunday, but any
showers/storms should remain highly isolated and over the mountains.
2. Warmer Sunday, but still with relatively low humidity.
Weak surface ridging will persist over the Eastern Seaboard thru
Sunday. Prog soundings appear drier in our area this afternoon
compared to yesterday, when a couple brief showers did spawn over
the mountains late in the day. Development thus doesn`t look any
more likely than it did then, and coverage was so minimal that a
mentionable PoP is not justified this aftn either, with coverage
looking to be less than 10%.
A weak shortwave is shown to dive south east of the blocking
ridge in the MS Valley, bringing a bit of high altitude cloud
cover; deep convective potential will remain limited by subsidence
inversion. Somewhat better moisture is seen between the top of the
PBL and that inversion, so congested cumulus and a stray shower
appear slightly more likely. Still, coverage is so sparse enough
that PoP again is less than 10% and not reflected in text fcst.
Any cloud cover with the incoming wave does not look significant
enough to impact radiational cooling, so locally dense mountain
valley fog is forecast again.
Light northeast flow east of the mountains will maintain relatively
low humidity each afternoon. 1000-850mb thicknesses and in turn
max temps increase slightly Sunday seemingly as a result of airmass
modification.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 1:35 PM EDT Saturday: The short-term fcst picks up at 00z on
Monday with an asymmetrical omega blocking pattern still in place
across most of the CONUS. On Monday, a Rex block begins to develop
as the southern extent of the upper trof cuts off a closed low and
the low slides westward and underneath the upper ridge. This blocking
pattern is expected to persist over the eastern CONUS for the rest of
the short-term period. At the sfc, broad Canadian high pressure will
get reinforced again from the north as the period begins. Over the
next couple of days, the center of the high will slide SE and over
New England and try to maintain control of our synoptic pattern. At
the same time, most of the model guidance tries to develop another
weak sfc low just off the SE Coast and spread some amount of deeper
moisture over the Carolinas. It remains unclear how far westward
this deeper moisture will spread and what impacts it may have on
our sensible wx. No major changes were made to the fcst with dry
conditions expected on Monday and a slight chance for precip over
the bulk of our fcst area on Tuesday. Any precip that does mater-
ialize should be minimal. Temperatures will start out near, if not
just below, climatology on Monday and cool a bit more on Tuesday.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 1:25 PM EDT Saturday: The extended forecast picks up at 00z
on Wednesday with a Rex-type blocking pattern aloft centered over
our area. This blocking pattern will likely be short-lived, as most
of the long-range guidance has the upper low opening back up to the
NLY flow by early Thursday. On Friday, broad upper trofing appears
to amplify again over the Great Lakes. This trof may cut off another
closed upper low to our north next weekend, but that is currently
just beyond day 7. At the sfc, broad high pressure will be moving
off the New England Coast as the period begins late Tuesday. At the
same time, another weak low tries to develop off the Southeast Coast
and spread deeper moisture inland over our area. It remains unclear
where this low will be centered and much deeper moisture it will bring
to our area, but most of the operational models do develop a weak low
somewhere off the SE Coast. Regardless, by late Thursday this system
is expected to be well to our NE and/or mostly dissipated. By the end
of the period next Friday, another low will strengthen to our NW and
may bring another moist cold front to our area. Overall, the sensible
fcst was not changed appreciably. We still have a slight chance for
precip on Wed across most of our NC zones and a diurnally-driven
slight to solid chance PoP over the higher terrain for Thurs and
Fri. Temperatures warm thru the period with values expected to be
a few degrees above normal by the end of the week.
&&
.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
At KCLT and elsewhere: VFR, excepting another round of morning
mountain valley fog affecting KAVL. Light NE flow will continue,
again excepting KAVL, where mountain effects resulting in VRB
during the mornings and a period of SE this afternoon. Otherwise
winds become light NE`y or VRB tonight and pick back up from the NE
in the morning. Diurnal cu with bases 040-050 thru early evening
and returning at similar levels by 15-16z Sun. A few alto/cirrus
clouds will be seen overnight and Sun morning but not enough to
preclude the valley fog.
Outlook: Mostly dry and VFR Sunday night and Monday, outside
of the potential for morning mountain valley fog and/or low
stratus. Upper low drifting over the region may translate to
better precip chances Mon-Wed and some associated restrictions,
but confidence remains low.
&&
.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.
&&
$$
SYNOPSIS...JPT
NEAR TERM...Wimberley
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...Wimberley

NWS GSP Office Area Forecast Discussion