Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 250721
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
321 AM EDT Mon Mar 25 2024

.SYNOPSIS...
Dry and cool high pressure will persist through Monday night before
unsettled weather returns along a meandering front on Tuesday
and Wednesday.  Clear weather will return by late Thursday,
followed by drier and warmer conditions going into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Upper cloud cover remains high across the wrn zones this morning and
expect increasing opaque cover pushing east through daybreak. This
may be enuf coverage to offset rad cooling and temps within the
freeze warning area may have a hard time actually dropping to 32
degrees in some areas.

The latest guidance doesn/t have a good handle on upper level
moisture, which could have a sigfnt impact on afternoon vertical
dewp mixing and related RH levels. Soundings still indicate a very
dry airmass abv 2 Kft per a stg subs inversion as an upper ridge
axis is slow to push east due to omega blocking across the wrn Atl.
Will be another tricky fcst for fire-wx, esp across the NC mtns
where shallow mixing still brought dewps down into the teens and
lower yesterday even across the valleys. A similar setup is in store
today, yet with better cloud coverage possibly limiting sfc heating
and therefore mixing heights somewhat. Have noticed the raw model
output and some of the MOS guidance had a decent handle on low dewps
yesterday, so blended in a a high ratio of this guidance for today`s
fcst. This still keeps RH values a little higher across the NC mtns
than yesterday due to lower insol, but nonetheless, have RH dropping
into the m20s or lower across the valleys and values into the low
teens to single across the ridges and mtn tops. Winds across the
mtns will pick up this afternoon as well with the valleys seeing low-
end gusts, while the higher elevations abv 4 Kft more easily mix
into stronger energy aloft to realize gusts on the order of 25-35
mph. Will coordinate and see if an SPS for Fire Danger is wanted by
NC land managers this morning.

The fcst remains dry overnight for the most part before pre-frontal
forcing increases and llvl moisture advects in from the ATL. This
will likely create sct rain showers across far NE GA and the sw/rn
NC mtns before daybreak as mech lift also increases. Highs will be
similar to Sun`s values meaning a cat or so below normal as llvl
ne/ly CAA continues before noon and Ci cover hinders heating a
little in areas. Mins will be held abv normal with increasing
mid/low level cloudiness with lows u30s to u40s NE-SW east of the
mtns and arnd 40 F mtn valleys.

&&

.SHORT TERM /TUESDAY THROUGH THURSDAY/...
As of 244 AM EDT Monday: By daybreak Tuesday, a de-amplifying
shortwave trough will be lifting across the Midwest, its attendant
surface front sprawled across the Ohio Valley.  Upstream, guidance
depicts a plume of decent surface-based instability that`ll carry
a more-or-less linear line of showers and embedded thunder right
into the Tennessee Valley, but high pressure over southern Quebec
will have driven enough easterly flow across the Carolinas that
Tuesday model soundings suggest a low-level inversion characteristic
of classical CAD.  It`ll be weak...but should be enough to limit
or even prohibit any sbCAPE from developing over the Carolinas.
So, as the system crosses the Appalachians it`ll be disrupted,
and upon encountering the stable environment east of the mountains,
it`ll struggle to regain any composure.  Zones south of I-85 may be
able to squeeze out a few embedded updrafts Tuesday afternoon and
evening, but by and large the environment just won`t lend itself
to convection.  Most guidance depicts the system simply fizzling out
upon reaching the Carolinas.  QPF response is less-than-impressive,
but will continue into the first part of Wednesday as ill-defined
ripples of synoptic forcing make tracks into the area while the
surface front stalls over the eastern portion of the forecast area.

Wednesday night, a lobe of southern stream energy will translate
across the Mississippi Valley and result in the trough over the
Midwest sharpening somewhat.  This will result in at least an open
wave along the stalled boundary over central NC.  In response,
rain chances will briefly ramp up again Wednesday night and
into Thursday, before the reinvigorated trough lifts northeast
and carries the front with it.  Once again, QPF response looks
like it won`t pose any problem, and with most of the forecast
area ensconced in a postfrontal cP air mass, we`ll likely be
unable to destabilize the atmosphere enough for any thunder.
By Thursday evening, the front should push decidedly east of the
area, ushering in drier air from the west and clearing out skies.
Temperatures through the period should be near normal.

&&

.LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
As of 253 AM EDT Monday: Broad, low-amplitude ridging will develop
across the eastern and central CONUS Thursday night and into the
weekend.  Surface high pressure extending from the central Gulf of
Mexico well up into the central Midwest will dominate the pattern
as it slowly migrates eastward, maintaining dry conditions and a
wide diurnal range, with afternoon temperatures climbing from the
upper 60s on Friday into the upper 70s by Sunday, and lows in the
40s each night.

Early next week, long-range guidance depicts a complex upper
pattern developing, as an upper low over southern California
phases with a compact trough (or closed low) dipping down out of
Saskatchewan.  It`s unclear just yet how this system will affect
the Carolinas...one cluster of ensemble guidance supports the
development of a backdoor cold front, which would push into the
Carolinas on Monday.  However, other solutions run the gamut from
some flavor of dry FROPA to a more warm-sector-y and rainy setup.
Whatever the case may be, it`s more likely than not that some kind
of rainfall will develop by the end of D7.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
At KCLT and elsewhere: VFR flight conds continue thru the 06z TAF
period across all sites. Strong hipres will continue to ridge in
from the NE and dominate the pattern thru the period. Winds may
become more ne/ly at KCLT thru the morning and early afternoon
before veering south of east as the p/grad relaxes. Have low-end
gusts more likely at KAVL this afternoon, but other sites could see
an occasional low-end gusts due to shallow afternoon mixing.

Outlook: Rain chances and possible restrictions return Tuesday into
Wednesday as a cold front moves in. Lingering showers could keep
restrictions in place through Thursday.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Freeze Warning until 9 AM EDT this morning for NCZ035>037-056-
     057-069-072-502-504-506.
     Frost Advisory until 9 AM EDT this morning for NCZ068-070-071-
     082-507>510.
SC...None.

&&

$$

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


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