Severe Thunderstorm Warning 24, NWS Greenville-Spartanburg, SC

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
252 PM EDT Sat May 5 2018

.SYNOPSIS...
A weak front will linger over our region this weekend bringing a
chance of showers and thunderstorms mainly for the mountains. Moist
southerly flow and upper level trough on Monday will bring a better
chance of showers and storms.

&&

.NEAR TERM /THROUGH SUNDAY/...
As of 235 PM EDT: widespread cirrus continues to stream across the
region this afternoon with sct to bkn decks of low to mid-lvl clouds
moving over the higher terrain from SW to NE. The latest RADAR images
are showing a few isolated cells beginning to pop up over the mtns,
yet the bulk of the sh and ts activity remains to our west over Tennessee.

Otherwise, upper level heights will lower thru the period in response
to an eastward moving h5 trof progged to swing across Tenn and into the
Carolinas by early tomorrow. This will push a relatively weak cold front
into the NC mtns tonight and help kick off additional shra/tstms activity.
Model sbCAPE values range into moderate levels across the higher terrain
with layered shear values remaining on the low-end. Thus, significant
organization is not expected...however a few strong pulse storms are possible
with hail and gusty outflows being the main threats. Outside the mountains,
instability will be kept in check with a shallow warm layer persisting.
Still expect mostly isolated -SHRA as the pre-frontal lift increases across
the Piedmont into the late afternoon and evening, with a few general tstms
possible.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/...
As of 145 PM EDT Saturday: High-amplitude upper trough will be
stretched down the Appalachians as we start the short term period,
with an exiting shortwave trough traveling up the downstream SW flow
aloft toward the Mid-Atlantic and New England, with an incoming
shortwave working its way down the NW flow on the upstream side of
the trough axis. We will be in a relative lull in precip Sunday
night between these two systems, with lows just a few degrees above
seasonal normals. The secondary shortwave will dig down while a weak
surface front, pushed by a surface high across the Great Lakes,
pushes toward our area, swinging winds around to the N and NE during
the day on Monday. The front will provide focus for convective
activity and though, as is the case in the near-term, upper shear
and related dynamics are weak, enough instability in the warm and
moist airmass will remain for another afternoon of scattered to
numerous thunderstorms (most numerous over the mountains where
mechanical lift will add to the weak synoptic lift), though nothing
severe expected. Typical general thunderstorm threats of brief heavy
downpours (basin-average QPF <1"), gusty winds, and lightning will
be the main concerns.

Behind the surface front, the Great Lakes high will cross the
Appalachians and ridge down the Eastern Seaboard with CAD onset
Monday night. Not a particularly strong damming event, but this
combined with lingering cloudiness associated with the upper
shortwave - that will briefly cut off Monday night into Tuesday over
the Southeast - will drop highs a few degrees for Tuesday, bringing
us back to below-normal territory for the first time in several
days. Could see some weak convection across the mountains or extreme
SE zones, around the periphery of the damming high, but nothing of
significance.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
As of 200 PM EDT Saturday: The upper weakness will be exiting the
area with shortwave ridging building for midweek before  yet another
trough pushes a front toward the area. Surface high pressure from
the damming will push offshore as well, and with winds switching
around to S, expect some upslope showers (possibly thunder) to
develop across the SW mountains Wednesday afternoon, with seasonal
temperatures for highs. Ridging over the Caribbean will prevent the
next shortwave from digging far into the Southeast, so best dynamics
remain well to the north as it and the weak surface front push
toward the area for Thursday afternoon. Have trended pops higher
across the mountains (to likely) for now, and with continued low-
level WAA, should see another uptick in afternoon highs back to
above normal. The surface front will likely hang up across the
northern tier, crossing the mountains as a surface trough and very
weak wind shift as we move toward the end of the week, but no
airmass change so the wind shift will really only add a downsloping
component with additional increases in afternoon highs as we move to
the end of the period. Isolated to scattered convection possible
each afternoon in a more diurnal pattern as the Caribbean ridge
builds northward.

&&

.AVIATION /19Z SATURDAY THROUGH THURSDAY/...
At KCLT and Elsewhere: expect VFR conditions to prevail thru the 18z
TAF period. Broad area of high clouds will persist thru the afternoon
and gradually lower as a weak cold front approaches and crosses the
area tonight and tomorrow. Still expecting precip to be confined mainly
across the NC Mtns and Foothills where coverage will range from isolated
to sct over the next several hours. Isolated to Sct tstms are also likely
across the higher terrain while the lower elevations remain mostly capped.
The shower and ts chances were handled with TEMPO and PROB30 groups at
KAVL and KHKY with PoPs being too low to mention SHRA or TSRA elsewhere.
Winds will remain predominately SLY thru the overnight before veering
around to WLY and then NWLY Sunday morning and afternoon.

Outlook: Isolated to scattered showers and thunderstorms are possible
again Sunday afternoon and evening as a stalled cold front lingers over
the area. Some temporary restrictions are possible. Somewhat unsettled
conditions will persist into early next week, with mainly afternoon chances
for SHRA and TSRA.

Confidence Table...

            00-06Z        06-12Z        12-18Z        18-00Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High 100%     High 100%     High 100%
KHKY       High 100%     High 100%     High 100%     High 100%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     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 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...JPT
SHORT TERM...TDP
LONG TERM...TDP
AVIATION...JPT

Hazardous Weather Outlook
National Weather Service Greenville-Spartanburg SC
556 AM EDT Sat May 5 2018

GAZ010-017-NCZ033-035-048>053-058-059-062>065-068-501>510-SCZ001>003-
061000-
Rabun-Habersham-Avery-Alexander-Madison-Yancey-Mitchell-Swain-
Haywood-Buncombe-Graham-Northern Jackson-Macon-Southern Jackson-
Transylvania-Henderson-Cleveland-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-
556 AM EDT Sat May 5 2018

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

.DAY ONE...Today and Tonight.

Isolated thunderstorms will develop this afternoon across the higher
elevations of the Carolinas and Northeast Georgia. The greatest
threat will be cloud to ground lightning with small hail and gusty
outflow winds possible.

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

..Sunday...No hazardous weather is expected at this time.
..Monday...No hazardous weather is expected at this time.
..Tuesday...No hazardous weather is expected at this time.
..Wednesday...No hazardous weather is expected at this time.
..Thursday...No hazardous weather is expected at this time.
..Friday...No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

None.

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