Special Weather Statement, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
654 AM EDT Sun Mar 28 2021

.SYNOPSIS...
A strong cold front will cross our area today, triggering another
round of showers and thunderstorms.  Behind the front, temperatures
will return to normal as high pressure builds in for Monday.
More unsettled weather looks to be in store for the region by the
middle of the week as another strong cold front reaches our region
from the northwest. After that cold front moves through Wednesday
night, expect some cool weather for the end of the week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 645 AM: Convection has slowed and weakened as it tracks
into MRX CWA, but some strong storms will track into the Smokies
here in about an hour. The rest of the area has become quiet, and
the wedge front is showing signs of lifting north. Still not much
sbCAPE along the wedge front, and MUCAPE is at a minimum across
the FA. So I expect the line of storms to continue to weaken until
diurnal heating can add some instability as the line enters the
Piedmont around midday.

As of 330 AM Sunday: A busy day today, with concerns for severe
thunderstorms, flash flooding, and strong gradient winds across
portions of the forecast area.

A frontal band of convection has congealed into a squall line
over central TN, and should pick up forward speed as it tracks
toward the Smokies during the pre-dawn hours. The storms may be
strong enough to knock down some trees as they enter the Smokies
and Little TN Valley around 12z this morning. So a Severe Tstm
Watch has been issued for Graham/Swain/Macon counties till 13z
(9 AM EDT). Meanwhile, warm frontal convection continues to fire
across the FA, with some isolated elevated thunderstorms tracking
thru the NC Piedmont. A weak wedge is holding on, and guidance is
probably too bullish on eroding it. Still, by about 15z, expect
the wedge front to surge north, and gusty SW winds should develop
across the entire area. At this point, the CAMs show the squall
line weakening significantly due to lack of instability. The
southern edge of the line will likely be the strongest, tracking
thru NE GA and into the western Upstate. The line may start to
pick up steam again as it reaches the I-85 corridor around noon,
but sbCAPE still looks to be only a few hundred J/kg. So there
is a below normal confidence on the severe threat, despite the
Slight Risk for our entire area. Given the fast progression of
this convection system, it may be east of the area by 3 PM, and
max temps may not be quite as high as expected. The main threat
with the line will be damaging wind gusts, and the unidirectional
shear should limit any tornado threat. But a brief spin up somewhere
along the line cannot be ruled out.

The flash flood threat will be contingent on the rain rates with
the main line of pre-frontal convection, as the line will be
moving pretty quickly, and there won't be much precip outside of
that. Given the high stream levels from earlier rainfall, will
leave the Flash Flood Watch as is.

Behind the pre-frontal convection, there will be some lingering
clouds and precip, with a secondary line of showers possibly
forming over the NC Piedmont along the actual front. This line
likely won't be severe, as it will have less CAPE to work with. The
bigger concern will be gradient winds picking up within strong
CAA in the NC mountains. Could see NWLY 45-55 mph gusts in the
northern mountains from mid-aftn thru the evening hours. So will
issue a Wind Advisory for Yancey/Mitchell/Avery from 16z to 6z
tonight. Temps will fall quickly tonight, dipping into the 30s to
lower 40s across most of the area.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY/...
As of 155 AM EDT Sunday: The first part of the work week is looking
fairly benign, with a flat mid/upper ridge pushing sfc high pressure
across the region on Monday and off the Mid Atlc/Carolina coast
Monday night. A weak sheared wave moving along the Gulf Coast looks
more and more like it will remain to our south through Monday night
and it won't be until Tuesday that we start getting some moisture
return as the upper pattern starts amplifying with the deepening
trof well to our west. This is something of a delay from what we
were looking at last night. With this trend, it seems like Tuesday
is more likely to remain dry for at least the first half of the
day. Although guidance precip prob is generally accepted, it was
pushed back until late in the day and kept over northeast GA and
SC for the most part. Temps will generally remain close to normal,
maybe a bit below Monday then a bit above Tuesday.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 329 am EDT Sunday: The middle part of the week looks active
and the latter part of the week looks like February. The main player
for the medium range will be a deep and amplifying mid/upper trof
that drops down over the Plains Tuesday night and barrels eastward
Wednesday, finally crossing our region Wednesday night with a strong
cold frontal passage. Out ahead of the approaching trof, moisture
will stream northward from the Gulf with strengthening isentropic
upglide forcing the development of precip Tuesday night and early
Wednesday, thus precip probs ramp up quickly. The best forcing
will be brought to bear across the region mainly on Wednesday,
and with deep moisture in place, precip seems like a good bet. How
much will depend on how quickly the front would move through, but
this will have to be monitored in light of the recent rainfall we
have had across the region. Severe weather will also be a concern,
partly because of the frontal passage which could happen during peak
heating. However, confidence in severe storms is low at the moment
because the ECMWF develops only modest amounts of buoyancy and the
GFS keeps a cool pool over the region once again. After the cold
front blasts through late in the day, a downright seasonally cold
Canadian high pressure air mass will move down across the region for
late in the week. Residual moisture could be squeezed out over the
mtns Wednesday evening in the form of high elevation snow showers,
but the rest of the week will be dry. Temps could be well below
normal for this time of year, and similar to what would be expected
in February. Highs might only be in the lower 50s east of the mtns
on Thursday under strong cold advection, and for the moment, the
entire fcst area looks like it could be below freezing at daybreak
Friday. The large sfc high will control our weather through next
weekend with temps slowly moderating back toward normal.

&&

.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
At KCLT and elsewhere: A wedge front can be seen in the obs,
finally beginning to lift north and should start pushing thru the
Upstate TAF sites and KCLT by 12z. This will bring winds around
out of the S/SW and VFR conditions. Then winds will pick up and
become gusty by 14z at all sites. Still expecting a frontal band
of showers and some embedded tstms crossing the area from west to
east in the 15-20z time frame, based on timing the current radar
trends. The line will have the potential to produce some strong
gusts, and winds will shift slightly to more WSW or W, remaining
gusty. A cold front will push thru and toggle winds to NW, with
gusts continuing thru the evening. MVFR to IFR Cigs will try to hold
on north of the wedge front over KHKY to start the TAF, otherwise,
expect VFR cigs and vsby, except with the convection. Low VFR cigs
start to clear out behind the front this evening.

Outlook: Dry high pressure returns Monday. Then moisture returns
ahead of the next cold front and flight restrictions are likely
across the region Tuesday night thru Wednesday.

Confidence Table...

            11-17Z        17-23Z        23-05Z        05-06Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High  95%     High 100%     High 100%
KAVL       High  94%     High  80%     High  95%     High 100%
KHKY       High  89%     High 100%     High 100%     High 100%
KGMU       High 100%     High  95%     High 100%     High 100%
KAND       High 100%     High  95%     High 100%     High 100%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables are available at
the following link:

www.weather.gov/gsp/aviation

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...Flash Flood Watch through this evening for NCZ033-048>053-058-
     059-062>065-501-503-505-507-509.
     Wind Advisory from noon today to 2 AM EDT Monday for NCZ033-
     049-050.
SC...None.

&&

SYNOPSIS...PM
NEAR TERM...ARK
SHORT TERM...PM
LONG TERM...PM
AVIATION...ARK

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
455 AM EDT SUN MAR 28 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0130 AM     TSTM WND DMG     1 WNW TALLULAH FALLS    34.73N 83.40W
03/26/2021                   RABUN              GA   PUBLIC

            NUMEROUS TREES BLOWN DOWN AT TALLULAH FALLS SCHOOL.
            DELAYED REPORT FROM THURSDAY NIGHT.

&&

PM

Special Weather Statement
National Weather Service Greenville-Spartanburg SC
841 AM EDT Sun Mar 28 2021

NCZ051-052-058-059-281330-
Haywood NC-Graham NC-Swain NC-Northern Jackson NC-
841 AM EDT Sun Mar 28 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN JACKSON...EASTERN
SWAIN...NORTHEASTERN GRAHAM AND NORTHERN HAYWOOD COUNTIES UNTIL 930
AM EDT...

At 840 AM EDT, Doppler radar was tracking a strong thunderstorm 9
miles northeast of Robbinsville, or near Fontana Lake, moving east at
65 mph.

Locations to be impacted include...
Bryson City, Cherokee, Lake Junaluska, Clyde, Maggie Valley, Smoky
Mountains-Balsam Mountain, Smoky Mountains-Big Creek, Smoky
Mountains-Deep Creek, B.R. Parkway-Smoky Mountains To Balsam Gap and
Smoky Mountains-Cataloochee.

Wind gusts up to 40 mph and pea size hail will be possible in these
areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall may flood areas with poor drainage, such as
ditches and underpasses. Avoid these areas and do not cross flooded
roads. Water levels of small streams may also rise rapidly. Seek
higher ground if threatened by flood waters.

&&

LAT...LON 3541 8377 3566 8331 3566 8330 3567 8329
      3579 8307 3577 8299 3579 8296 3574 8295
      3575 8292 3570 8290 3569 8290 3568 8289
      3555 8282 3531 8372
TIME...MOT...LOC 1240Z 248DEG 56KT 3541 8367

WJM