River Flood Advisory 10, NWS Greenville-Spartanburg, SC

077 
WGUS82 KGSP 280115
FLSGSP

Flood Advisory
National Weather Service Greenville-Spartanburg SC
915 PM EDT Sat Mar 27 2021

...The Flood Advisory is cancelled for the following rivers in North 
Carolina...

  Broad River In NC At Boiling Springs affecting Cleveland County.

NCC045-280215-
/O.CAN.KGSP.FL.Y.0010.000000T0000Z-210328T0115Z/
/BSPN7.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.NO/
915 PM EDT Sat Mar 27 2021

...The Flood Advisory for the Broad River In NC At Boiling Springs 
has been cancelled...

The Flood Advisory is cancelled for
  the Broad River In NC At Boiling Springs.
* At 8:15 PM EDT Saturday the stage was 5.8 feet.
* Flood stage is 12.0 feet.
* Forecast...The river is expected to remain below Action Stage into 
  Sunday.


&&

LAT...LON 3527 8173 3524 8159 3516 8167 3520 8176

$$

RMM

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
451 AM EDT Sat Mar 27 2021

.SYNOPSIS...
A warm front is expected to move northward across the area today,
keeping our weather active through tonight. A strong cold front
should approach from the west late tonight and then move across the
western Carolinas and northeast Georgia on Sunday with another round
of 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 next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 330 AM Saturday: An upper anticyclone continues to dominate
over FL, while a vigorous upper trough digs across the Northern
Plains to the Southwest. An amplifying flow pattern will allow a
warm front to activate across the Gulf States and lift northward
today. Convection is already firing from northern MS to SC
Midlands. The CAMs have had trouble initializing the convection,
but the HRRR has had fairly good run-to-run consistency of the
evolution of the convection thru the day today. If the HRRR is
correct, we will have some discrete, rotating storms this aftn
across western NC, with convection peaking just east of the FA later
in the aftn. But the better severe threat will definitely be to our
west, where all the ingredients are in place. The new Day 1 Outlook
has an Enhanced risk over the Mid-South, with a Marginal risk across
the entire FA (A slight risk does reach the Smokies). In any case,
there are a range of outcomes today, as some CAMs, including the
NAMnest develop a lot more convection early this morning and set up
an in-situ wedge that keeps the better sfc-based CAPE only along
the southern fringes for the rest of the day. Meanwhile, the HRRR
has a lot less morning precip, and has 1500-2000 J/kg of sbCAPE
with 50 kts of 0-6 km bulk shear in the aftn. To make things even
more uncertain, both HRWARW and HRWNMM organize convection into
an MCS over eastern TN that crosses the mountains this aftn and
pushes thru the entire FA. With all that said, I think at least
some damaging wind threat will exist with any convection that
develops. The big question is perhaps is there enough upper support
for intense updrafts. If we manage any supercells, hail and even
an isolated tornado threat cannot be ruled out, but confidence is
still low. Another concern the flooding potential. Fortunately,
storms should have good motion, and I don't see much signal of
training storms. With that said, isolated flooding will be possible,
given the high river levels. Otherwise, expect mostly cloudy skies
and with temps generally 5-10 deg above normal.

Whatever convection does develop, guidance is in good agreement that
a cold pool or in-situ wedge will set up tonight, with additional
scattered showers possible over the wedge overnight. A 50+ kt SWLY
LLJ will begin to work into the NC mountains during the pre-dawn
hours as a cold front approaches from the west. Upslope areas may
see some heavy rain, and highest peaks could see advisory-level
gusts above 45 mph. Lows will be well above normal under cloudy
skies.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY/...
As of 315 AM EDT Saturday: By daybreak on Sunday, our attention
will shift to the next round of showers and thunderstorms expected
to be approaching from east TN. The timing of this convection
will be the key to how Sunday plays out in terms of the severity
of thunderstorms and the high temps. At least the guidance is
in good agreement that showers and storms will be numerous,
if not widespread, at some point during the daytime hours. The
culprit will be a strong cold front driven east by a mid/upper
trof making steady progress across the TN/OH valley. Forcing
should be excellent and moisture more than adequate. A linear
convective mode looks to be favored. The question will be...when
does the line of showers/thunderstorms arrive? The GFS and HRRR
have the line moving into the mtns as early as mid-morning, while
the NAM and the Hi-res WRF variants have a later timing. If later,
we have more of a chance to destabilize to a greater degree east
of the mtns through early afternoon, and thus more of a chance
for severe weather, assuming pre-frontal showers over the Piedmont
don't contaminate the air mass. One plausible scenario would be for
a fairly well organized line of storms to move across the mtns in
the morning hours and then come off the Escarpment during the early
afternoon and then move across the Piedmont of the Carolinas in
the mid/late afternoon. The Slight Risk across the entire forecast
area, shown in the Day 2 Convective Outlook, looks like a safe bet
given the linear nature of the convection, even though the CAMs
have a stronger presentation once the line moves east of the fcst
area. In this scenario, the line would pass with sporadic reports
of wind damage and perhaps some hail just about anywhere across
the fcst area. Another concern would be if we retain enough shear
in the environment to support embedded rotating updrafts. Agree
with the Day 2 that the potential looks better to our east for more
widespread wind damage/tornado threat based mainly on the timing,
but it is certainly possible this intensification could happen
over the I-85 corridor. A flood threat will also exist given the
antecedent conditions, but the linear storm nature favors a short
duration of heavy rain that will limit rainfall amounts. The high
temps Sunday are entirely dependent on the timing of the storms,
but should be above normal. The storms should exit to our east in
the early evening as the cold front passes, with some lingering
westerly flow upslope shower activity along the TN border that
will slowly diminish through late evening.

In the wake of the cold frontal/mid/upper trof axis passage, sfc
high pressure will build in from the west Sunday night as a broad
flat upper ridge moves in from the west on Monday. Sky will clear
and temps will fall back close to normal with a drier air mass.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 450 am EDT Saturday: The upper flow pattern should remain
progressive into the medium range part of the forecast. On Monday
night, the axis of a broad upper trof should move off the East
Coast, taking sfc high pressure along with it. A weak system along
the Gulf Coast will start to lift out to the N/E, but the timing
and extent of the moisture/light precip is uncertain. The forecast
follows closer to the GFS depiction of better precip chances moving
past to the east on Tuesday morning, followed by a relative lull
later in the day. By that time, the upper pattern should already
be amplifying as an upper trof digs over the Rockies. By Tuesday
night and Wednesday, as this next system moves out over the Plains,
the strengthening SW flow aloft will allow for moisture to return
from the Gulf. Important model differences creep in with how
a cold front is handled by Wednesday. The latest ECMWF has the
boundary moving a bit faster and with more moisture/precip in
the warmer air along and ahead of the front, while the GFS has
more of the precip behind the front. The problems would be with
the ECMWF because it would increase the QPF and perhaps renew our
hydro problems/concerns. Any severe storm threat would probably
be greatest that afternoon/evening ahead of the front, which
would cross the region by late evening. Precip chances were kept
in check for the time being. Precip should end from the west by
around daybreak Thursday. The deepening mid/upper trof would cross
the area early Thursday, behind which a cool Canadian high pressure
air mass would build in for the remainder of the period. This air
mass will remind us that it is still early Spring as temps are fcst
to drop back to about ten degrees below normal, possibly with some
frosty mornings late in the week. Temps should moderate over the
next weekend.

&&

.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: A moist warm front will support
lowering cigs/vsbys mainly between 08Z and 15Z mainly in MVFR
range. Scattered showers (and possibly some embedded TS) will
develop this morning as the warm front approaches, but guidance
trending toward better coverage of TSRA in the 17-22z time frame
from west to east, with some storms possibly being strong. Will
continue to handle TS with PROB30 groups. Continued showers possible
behind main convection this evening. Cigs should lift to VFR this
aftn, but some guidance hints that it holds on to MVFR across
the NC Piedmont. Depending on the amount of rainfall, and where
the warm front stalls out, could see development of IFR to LIFR
cigs and some fog, especially in the NC Piedmont tonight. Winds
will be light for the most part thru the period, except around
any convection, favoring a N to NE direction this morning, then
shifting to S or SW this aftn. At CLT, the SW winds will shift to
WNW to NW behind the convective activity late aftn or early evening.

Outlook: Thunderstorms bringing flight restrictions are probable
Sunday. VFR conds return Mon with a couple more moist systems and
flight restrictions possibly affecting the region as early as Tue.

Confidence Table...

            09-15Z        15-21Z        21-03Z        03-06Z
KCLT       Med   75%     High 100%     High  95%     High  82%
KGSP       High 100%     High  83%     High  88%     High  86%
KAVL       High 100%     High  95%     High  93%     High  92%
KHKY       High 100%     High 100%     High  91%     Med   77%
KGMU       High 100%     High  86%     High  93%     High  86%
KAND       High  98%     High  93%     High  98%     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...None.
SC...None.

&&

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

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
524 AM EDT Sat Mar 27 2021

GAZ010-017-018-026-028-029-NCZ033-035>037-048>053-056>059-062>065-
068>072-082-501>510-SCZ001>014-019-280930-
Rabun-Habersham-Stephens-Franklin-Hart-Elbert-Avery-Alexander-
Iredell-Davie-Madison-Yancey-Mitchell-Swain-Haywood-Buncombe-Catawba-
Rowan-Graham-Northern Jackson-Macon-Southern Jackson-Transylvania-
Henderson-Cleveland-Lincoln-Gaston-Mecklenburg-Cabarrus-Union NC-
Caldwell Mountains-Greater Caldwell-Burke Mountains-Greater Burke-
McDowell Mountains-Eastern McDowell-Rutherford Mountains-
Greater Rutherford-Polk Mountains-Eastern Polk-Oconee Mountains-
Pickens Mountains-Greenville Mountains-Greater Oconee-
Greater Pickens-Greater Greenville-Spartanburg-Cherokee-York-
Anderson-Abbeville-Laurens-Union SC-Chester-Greenwood-
524 AM EDT Sat Mar 27 2021

This Hazardous Weather Outlook is for northeast Georgia, piedmont
North Carolina, western North Carolina and upstate South Carolina.

.DAY ONE...Today and tonight.

Scattered to numerous showers and thunderstorms are expected to
develop across the area today as a warm front lifts north through the
region. A few storms may become severe, with the main threats being
damaging wind gusts and large hail to the size of quarters. There
will also be an isolated tornado threat, mainly across the Piedmont
south of I-40.

.DAYS TWO THROUGH SEVEN...Sunday through Friday.

A line of thunderstorms is expected to cross the area from west to
east during the late morning to mid-afternoon hours. Damaging winds
will be the main threat, but a few storms may produce large hail, as
well.

.SPOTTER INFORMATION STATEMENT...

None.

ARK