Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KGSP 250759
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
259 AM EST Sun Feb 25 2018

.SYNOPSIS...
A cold front will slowly cross the piedmont today and reach
the Carolina coast by Monday morning. Cooler and drier air will
settle southward into the region behind the front on Tuesday before
moisture rapidly returns to the area mid to late week. Cooler and
drier high pressure returns next weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
An active pattern over the near term with a cold front approaching
from the west. This front will push into the NC mtns arnd 12z this
morning and a line of precip ahead will cross over the FA into the
afternoon. Not expecting much fanfare with this feature outside of
some modest rainfall and isol thunder across the the ern zones this
afternoon. The upper levels become more energized with periods of
inline vorticity passing thru. The strongest s/w energy looks to
cross around 21z when the best sfc heating will be ongoing within
the low levels. Cross sections show deepening upward motion
aloft...however there is no good connection with the low-level
forcing during this time. Sfc convergence will remain rather weak
and an inversion will persist at h85-h7 thus with limited
instability and marginal forcing...deep convec is not likely.
However...some areas outside the mtns could see isol low-top general
tstms with muCAPE reaching arnd 300 J/kg.

The front will slow down as it nears the se/rn edge of the FA this
afternoon/evening and will become a focusing zone for additional
precip during the overnight period as it wafts north. Precip will be
beneficial with storm total amts into Monday afternoon ranging from
an inch and a quarter over the SW NC mtns to a half inch over the
I-77 corridor. Cloud over will increase during the afternoon over
non/mtns yet max temps will still reach arnd 15 degrees abv normal
with a component of downslope warming and continued sw/ly flow. Mins
will also reamin well abv normal with persistent cloudiness and some
sfc mixing thru the overnight.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 255 AM EST Sunday: No big surprises seen in the new model
guidance for the first part of the work week. We will be in the
middle of dealing with a final wave of precip at daybreak Monday
as one last swath of upper divergence slides overhead with the
entrance region of the upper jet moving past to the north in the
morning, accompanied by a short wave also moving overhead. The
mid/upper forcing should move out to the east in the afternoon,
taking most of the precip along with it. So, we begin the day with
a high precip probability, but that steadily tapers off thru the
day, leaving only a small chance near the Blue Ridge Escarpment
around sunset owing to low level easterly flow that might keep
some light precip in the upslope regions. Even that small chance
should end by mid-evening. We should finally dry out, temporarily at
least, Monday night and Tuesday as a flat broad upper ridge moves
overhead and pushes sfc high pressure past to the north. The air
mass will be drier for sure, and cooler as well, but still on the
order of ten degrees above normal. The flow remains progressive,
though, and the Gulf opens right back up by late Tuesday with
moisture streaming back northward ahead of the next approaching
upper trof. For the last few days, the model guidance has been
showing the development of isentropic lift Tuesday night and early
Wednesday with moisture return and precip development from the
SW in the pre-dawn hours. See no reason to doubt that plan. The
only question is the timing of precip onset. Suspect that we will
stay dry thru at least midnight, with precip breaking out first in
the southerly upslope regions of the Balsam and Nantahala mtns,
spreading east from there. Fortunately, temps will remain on the
order of ten degrees above normal, so any precip will be all rain.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
As of 130 am Sunday: Starting Wed morning, surface high pressure
moving east off the mid Atlantic coast with low level southerly
upslope flow on the backside of the high up against our NE GA and SC
/ NC mountain areas. This upslope low level flow should persist
during the day Wednesday then shift more from the SW being parallel
to the mountains going into Wed night. The stationary front
initially from south FL to the Mississippi Delta Wed morning will
move north as a warm front and should be across NC by Thursday
morning. The low should be near Chicago Thursday morning as the
associated cold front advances east from the Miss Valley toward our
region. Instability is forecast to be low ahead of the cold front
with 100 to 200 CAPE over the Piedmont from GA to CLT area Thursday
afternoon. 925MB flow is forecast to be from SW 35 to 45 kts
Thursday afternoon along and south of I-85 corridor. After a few
embedded thunderstorms Thursday PM in the piedmont, front moves off
the Carolina coast Thursday evening. Low pressure reaches the Jersey
coast early Friday with rather strong NW Flow over the NC mountains.
Expect some high elevation snow before precip ends on Friday. Dry
high pressure ridging down from Canada will give our area a dry and
seasonably cool weekend.

&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
At KCLT and Elsewhere: The atmos will remain well mixed thru the
period ahead of a cold front and aft front slows and stall by late
afternoon. With good mixing it will be hard for lower stcu to
develop this morning yet MVFR CIGS are likely all locales aft
daybreak...with CIGs developing late morning at KCLT. Not much of a
VSBY concern with good mixing this morning and gusty conds
persisting into the afternoon/evening...but by late in the period
VSBYs will drop into MVFR/IFR with lowering winds and high sfc
saturation due to rainfall. The atmos will become weakly unstable
today and isol tstms are probable...yet not enuf coverage to include
mention in TAFs. There wont be a sigfnt wind shift nor speed change
associated with the FROPA this afternoon...so no issues are
anticipated with non/convec wind shear.

Outlook: The front will remain nearly stalled across the
area Sunday night into Monday morning, with rounds of SHRA and
restrictions. Drier and VFR conditions should return late Monday,
though daybreak restrictions could develop Tuesday morning. Another
wet frontal system will affect the area Wed and Thu.

Confidence Table...

            08-14Z        14-20Z        20-02Z        02-06Z
KCLT       High  98%     High  93%     High  97%     High  96%
KGSP       High 100%     High  86%     High  90%     High  93%
KAVL       High  97%     Med   71%     High  93%     High  97%
KHKY       High  97%     Med   60%     High  87%     Med   67%
KGMU       High 100%     High  90%     High  90%     High  93%
KAND       High 100%     High  84%     High  87%     Med   77%

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:

www.weather.gov/gsp/aviation

&&

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

&&

$$
SYNOPSIS...DEO
NEAR TERM...SBK
SHORT TERM...PM
LONG TERM...DEO
AVIATION...SBK



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.