-- Discussion containing changed information from previous version are highlighted. --
669
FXUS62 KGSP 311036
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
636 AM EDT Fri May 31 2024

.SYNOPSIS...
Dry high pressure centered over the region will keep temperatures
slightly below normal with dry weather persisting through Saturday.
High pressure shifts offshore Sunday with warming temperatures and
increasing moisture. A more active stretch of weather may return
early next week with daily afternoon thunderstorm chances within a
summer like pattern. Another cold front will approach the area late
week.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
630 AM Update...No sigfnt changes made to the fcst. Expect thin Ci
to continue thru the next update with no fog threats.

An ulvl trof axis shifts east today as a strong ridge builds in from
the west and the area comes under the influence of stg subsidence.
This will keep the column mostly dry the period as PWAT values drop
abt 0.9 inches below normal.

Strong convec to the west will bring in a good amt of upper clouds,
but llvl clouds will be limited to the mtn ridges as LCLs become
quite dry east. Surface high pressure becomes reinforced to the
north during the afternoon and srn ridging will advect dry air more
efficiently across the ern zones. Thickness values don/t change much
today and with reduced insol, expect highs held few degrees below
normal.

Surface td/s will vertically mix better across the ern zones due to
a more energized mixed layer, which will lower afternoon RH values
to less than 25 percent east of I-26. Relative humidity will likely
hold in the m30 percent range west. No sigfnt fire-wx issues
anticipated as winds generally remain less than 10 kts with a
limited low-end gust potential.

Decent rad cooling tonight and calming winds will allow min temps to
drop 6-8 degrees below normal across the area. A late morning dense
fog threat is negligible, however, as sfc td/s only increase to the
m40s.
-- End Changed Discussion --

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 204 AM Friday: The short term forecast period starts off
Saturday morning with a tall shortwave ridge extending along the
spine of the Appalachian Mountains. Farther west, a compact shortwave
trough is progged to be located over the Lower Mississippi Valley.
At the surface, sprawling high pressure will still be entrenched
across much of the East Coast with an associated very dry
continental airmass. Forecast PWATs Saturday morning around or below
0.5" would be well below the 10th percentile for early June and near
daily record low values based on Greensboro sounding climatology. As
such, a dry forecast will prevail on Saturday with temperatures
remaining a couple ticks below average. By Saturday night into
Sunday, surface high pressure will quickly slide offshore with weak
southerly return flow returning across the southeast states. At the
same time, the previously mentioned shortwave trough over the Lower
Mississippi Valley will lift northeast across the Ohio Valley and
into the central Appalachians. Associated rain chances will return
across the mountains which will be in closer proximity to a deeper
plume of moisture. Uncertainty exist farther east as to how quickly
moisture will return with return flow trajectories still emanating
out of a local ThetaE minimum in the wake of the departing surface
high. Will carry at least a slight chance of showers and storms
across the Piedmont with the greatest rain chances confined to the
mountains.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 216 AM Friday: A more typical summer pattern appears poised to
return early to middle next week. Persistent onshore flow will
support continued moisture recovery with dewpoints rising back into
the mid 60s amidst 1.5-2" PWATs. Aloft, a weak westerly flow regime
will be draped from the Southern Plains to the Southern
Appalachians. The 00z suite of global guidance depicts several
embedded shortwave perturbations that will slowly make their way
into the area early next week. Exactly how these waves evolves
remains uncertain with GFS and CMC solutions attempting to close off
an upper low while the ECMWF and ICON camp paints several more
progressive/weaker waves. Regardless, the combination of passing
waves and a very moist atmosphere should prove sufficient to
instigate mainly diurnally driven showers and thunderstorms Monday
through Wednesday, especially across the mountains. Forecast
soundings are not overly supportive of a severe weather threat with
very moist profiles, near moist adiabatic lapse rates, and very
tall/skinny CAPE profiles. A couple locally strong water loaded wet
microbursts cannot be ruled out and will need to be assessed on a
daily basis.

By late week, guidance depicts an intense Pacific jet
diving into British Columbia and the Pacific Northwest. This in turn
carves out a deep and negatively tilted trough across the Central
and Northern Plains by Wednesday morning. This trough then swings
across the Great Lakes and into the Ohio Valley. An associated cold
front will race across the Great Plains and towards the region by
Thursday. Guidance begins to diverge at this point with regards to
timing of the front and location/amplitude of the large scale
trough. A more organized severe weather threat could accompany the
front, but will be dependent on eventual evolution of the upper
trough and strength of the front. Another surge of dry continental
air with near daily record low PWATs will bring a return of dry
weather Friday into next weekend.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
At KCLT and elsewhere: VFR trends continue thru the 06Z TAF cycle.
Some mlvl StCu will persist this morning thru daybreak arnd KCLT and
the Upstate terminals, but cloud cover returns to mainly Ci outside
of afternoon FEW/SCT Cu across the NC mtns. Winds remain calm/light
thru daybreak then align ne/ly to ene/ly after inversion break
outside the mtns with speeds generally 6-8 kts. Afternoon winds at
KAVL align se/ly. Winds go variable to calm once again across the FA
tonight.

Outlook: VFR and dry weather through Saturday. Convective chances
return late this weekend and will linger into next week.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$

SYNOPSIS...TW
NEAR TERM...SBK
SHORT TERM...TW
LONG TERM...TW
AVIATION...SBK