934 
FXUS62 KGSP 162153
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
553 PM EDT Sun Oct 16 2022

.SYNOPSIS...
Warm temperatures will be coming to an end for a few days.  Expect 
scattered showers through tonight along and north of Interstate 85 
ahead of a strong cold front which crosses our region on Monday. The 
coldest air of the season so far will reach the area and bring about 
widespread night time and early morning freezing temperatures and 
frost for most of the week. Temperatures will warm to near normal 
next weekend.

&&

.NEAR TERM /THROUGH MONDAY/...
As of 545 PM EDT Sunday: We're currently seeing a broad area of
sct to numerous showers (but no lightning) to our west and north
associated with the approaching cold front and subsequent broad 
area of low-lvl convergence. The leading edge of this front will 
approach the southern Appalachians this evening, increasing the 
chances for showers and isolated/widely sct thunderstorms, mainly 
from mid-evening thru the early morning hours. The highest PoPs 
(generally 60-80%) will be advertised across the mtns and northern 
areas, where the deepest forcing is forecast, and some (albeit very 
weak) instability is expected. PoPs taper off considerably to 20% or 
less across southern zones where forcing is weak and instability is 
basically non-existent. Can't rule out a marginal severe storm or 
two developing in the strongly sheared and slightly more unstable 
air mass over east TN late this afternoon/evening and making a run 
toward western NC, but the overall threat is quite low in light of 
the weak buoyancy. 

Otherwise, an expansive long wave trof covers much of the NE CONUS, 
with a speed max digging south into the upper Mississippi Valley. 
Associated height falls will further deepen the trof through the 
near-term, enhancing frontogenesis along the baroclinic zone that
extends from the OH Valley into the lower Mississippi Valley. Cold 
advection will develop over the mtns by daybreak Monday, as the front 
slides east of the fcst area during the afternoon. We can't rule out 
a small window of iso/sct shower development across eastern areas 
Monday afternoon before the drier/stable air spills in behind the 
front. High temperatures over the mtns on Monday are expected to be 
slightly below climatology in the cold advection regime, but another 
day of above-normal temperatures are expected outside the mtns as 
downslope flow will offset any weak cold advection that develops 
there during the day.

&&

.SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/...
As of 130 PM Sunday: Very broad upper low will set up shop over the
Great Lakes region into Ontario/Quebec through the period. Rapid
height falls will be associated with this setup following a clean
fropa Monday night. Stout CAA will filter in behind the front and
allow temperatures to drop 8-12 degrees below normal with some
locations in the mountains dipping 15+ degrees below normal. Gusty
northwesterly winds will also traverse across the CFWA Monday
night and should offset any frost development. Nonetheless,
a Freeze Watch has been issued for the western NC mountains and
Rabun County in northeast GA as the coldest air since mid-April
enters the region. As a matter of fact, the air will be so cold
that if any residual moisture lingers along the TN Border Monday
night into Tuesday morning, a few snow flurries can't be ruled
out along the favorable northwest facing slopes.

Strong Canadian high centered over the central CONUS will continue
to spew CAA into the region on Tuesday, while much colder air aloft
settles over the East Coast. Expect temperatures on Tuesday to be
12-18+ degrees below-normal despite mostly sunny skies. The pressure
gradient relaxes a bit by Tuesday night, while the cold air still 
hangs around. Freeze Warnings and Frost Advisories will likely be 
issued for most, if not all of the CFWA Tuesday night as overnight 
lows dip well into the 20s across the mountains and in the low to 
mid 30s elsewhere. The base of the upper low will swing across the 
area on Wednesday and allow for temperatures to uptick a few degrees 
as heights slowly begin the recovery process, but values will remain 
10-15 degrees F below-normal for highs.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
As of 230 PM Sunday: The axis of the upper low will lift off to
the northeast Wednesday night, but surface high pressure will remain
in control as good radiational cooling conditions settle over the
region Wednesday night. As a result, the coldest night should be
Wednesday night as most locations will be at or below freezing,
with the usual warm spots even flirting with the freezing mark. Some
record lows could be in jeopardy due to this unusual surge of cold
air. Despite the upper low lifting northeast, well into Canada
by Thursday, broad upper troughiness will linger over the region
through the end of the work week. This will only keep below normal
in the CFWA through Friday before finally rebounding back to normal
values by the weekend, and even slightly above normal by D7. High
pressure will remain in control through much of the period, but
should slide offshore by Thursday and winds will veer to a south
to southwesterly component and will play a key role in temperatures
bouncing back. Dry conditions will prevail through the medium range.

&&

.AVIATION /22Z SUNDAY THROUGH FRIDAY/...
At KCLT and elsewhere: SW winds of around 10 kts, with perhaps some 
low-end gusts across the Piedmont are expected through the 
afternoon along with slowly increasing mid/high clouds. Shower 
chances will increase tonight in association with a strong cold 
front that will approach the area from the northwest. Shower chances 
will be highest at KAVL and KHKY...and lowest farther south at KAND. 
For now, the SHRA mention has been limited to Prob30s, but tempos 
will most likely be needed at some point for KAVL/KHKY, and perhaps 
for other sites. Isolated to widely scattered TS will also be 
possible, but that potential is limited to Prob30 at KHKY for now. 
Otherwise, VFR conditions should prevail through the period, with 
restrictions expected to be limited to any periods of heavier 
rainfall.  

Otherwise, SW winds will weaken to around 5 kts overnight before 
increasing to 10-15 kts at the Piedmont/foothills sites and becoming 
gusty during the daylight hours. At KAVL, winds will become NW @ 
10-15 kts behind the front around sunrise and become gusty through 
the daylight hours. Skies will generally clear and any rain chances 
end by sunrise.   

Outlook: Cool and dry high pressure will build into the region 
through the week. Frost/freeze conditions could impact operations 
each morning from Tuesday onward, but with VFR conditions still 
likely at most sites.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Freeze Watch from late Monday night through Tuesday morning 
     for GAZ010.
NC...Freeze Watch from late Monday night through Tuesday morning 
     for NCZ033-048>053-058-059-062>065-501-503-505.
SC...None.

&&

$$
SYNOPSIS...DEO
NEAR TERM...JDL/JPT
SHORT TERM...CAC
LONG TERM...CAC
AVIATION...JDL/JPT