Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 292117

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
517 PM EDT SUN MAY 29 2016

Abundant moisture will persist over the region as tropical system
Bonnie stalls near the South Carolina coast. The remnants of Bonnie
will drift northeast along the Carolina Coast through the first half
of the week. A weak cold front will then push into the southern
Appalachians from the northwest and stall later in the week.


As of 515 of showers has stalled and has begun to
dissipate along and west of I-26. Another area of showers will
likely drift over the Charlotte metro area during the early evening
hours. I will update the forecast to adjust pops and sky to latest
trends. In addition...I will populate the hourly temp and dewpoints
with observations.

As of 230 PM EDT Sunday: Big story continues to be the remnants of
TD Bonnie. The circulation center is basically one county inland and
can fairly easily be seen  on radar and satellite. Rain bands
continue to spiral around the system with an area of rain butting up
against the foothills and extending into the Upstate/Upper Savannah
Valley. Luckily low levels are still fairly dry with cloud decks up
at 8-10kft, so for the most part only light to occasionally moderate
rain. Looking at MRMS 12-hr QPEs highest totals are just over 1.5"
down in eastern Greenwood County. Soils are easily able to handle
this and overall do not expect much more than 0.5-1" or so. Luckily
for folks in the Charlotte area the I-77 corridor seems to be in a
bit of a lull with just overcast skies with intermittent light rain,
but more dry than rain. Some instability is working its way inland
from the coast around the circulation and may poke into the
Charlotte Metro area this afternoon (seeing a whopping 100 J/kg on
the latest mesoanalysis), so have slight chance thunder across some
of those extreme eastern counties. Other chance of thunder would be
in extreme western zones where clearing skies have allowed sbCAPEs
to climb over 500 J/kg and while convection remains low-topped and
isolated, cannot rule out enough oomph to get some lightning across
the SW NC mountains.

Widespread cloud cover tonight will continue as TD Bonnie meanders
slowly northeast up the SC coast, pushed slowly by a high-wavelength
shortwave passes through the Great Lakes and Appalachians, but
should see some scattering toward daybreak which will allow lows to
drop a few degrees cooler than last night. Very weak flow aloft is
expected during the day tomorrow with again a minimum of instability
across the foothills and western Piedmont but with increasing
instability through the day mainly along the I-77 corridor.
Temperatures will be highly dependent on cloud cover but should
climb back in to the mid 80s across a good chunk of the Upstate, and
upper 80s in the Upper Savannah Valley, but in general pretty close
(within a degree or two) to seasonal normals.


At 230 PM Sunday: On Monday evening weak nearly zonal upper level
flow will extend across the southeast USA, and will persist into
Wednesday, even as modest upper troughing eventually sets up along
he southern portion of eastern seaboard. A very weak upper impulse
appears to slowly cross the western Carolinas and northeast Georgia
on Tuesday and Wednesday.

At the surface, on Monday evening what`s left of tropical storm
Bonnie will be moving slowly northeast along the SC coast toward the
NC coast. Moisture associated with this system will will still be
impacting our area, but the models disagree on whether the moisture
will extend as far east as the mountains, or just to the Interstate
77 corridor.

As Bonnie`s remains move along the NC coast on Tuesday, moisture is
expected to decrease over our area, but not enough to preclude
modest precipitation, and this trend continues into Wednesday.
Precipitation amounts are expected to be quite limited, as
isentropic downglide will be present in the west side of Bonnie`s
remains, however instability will be present both Tuesday and
Wednesday, perhaps supporting a few stronger showers. Temperatures
will run slightly above normal.


At 230 PM Sunday: On Wednesday night an upper trough will be
crossing the upper MS River Valley and and Southern Plains, while
weak upper troughing remains along the southern eastern seaboard.
The northern portion upper trough reaches the Great Lakes by
Thursday, where it remains into Sunday, while the southern portion
reaches the southern MS River Valley. Weak mid level vorticity
appears to reach our area late in the period, though the models
disagree on when and how much.

At the surface, on Wednesday night, moisture associated with tropical
system Bonnie will remain over our area, while a cold front crosses
the MS River Valley. The front reaches the Southern Appalachians
late Thursday, and slowly crosses the foothills and piedmont on
Friday, stalling near the southeastern portion of our are on
Saturday. There is some disagreement between the models on how far
north moisture will linger as a surface wave moves along the stalled
boundary on Sunday. Precipitation amounts are expected to peak with
the arrival of the cold front late in the forecast period, but at
this point do not appear to be excessive. Temperatures are expected
to cool from slightly above normal to near normal.


At KCLT: -SHRA associated with rainbands from TD Bonnie have moved
west, lining up closer to the foothills/I-26 corridor/Upper Savannah
Valley. Have improved conditions at KCLT to VCSH with only TEMPO for
brief MVFR conditions, but otherwise VFR this evening. All guidance
drops cigs to MVFR overnight with some hints at IFR so have moved up
MVFR cigs to 06z. Improved cigs to MVFR and introduced PROB30 TSRA
at 15z Monday as instability increases. Winds should remain N/NE
through the period, with low-end gusts possible this afternoon but
generally 5-10kt through the period.

Elsewhere: As mentioned in the KCLT discussion, rain band will
affect basically all other TAFs except maybe KHKY through the
afternoon before moisture begins to wane, with improving conditions
overnight. Except for the SW NC mountains, any restrictions should
remain to the east toward KCLT overnight so have kept conditions at
other sites VFR, but will need to watch especially KAVL. TSRA
chances not high enough at these sites to introduce PROB30 Monday
just yet, but may need to consider it for after 18z with later
issuances especially for KHKY. As with KCLT, winds generally N/NE
through the period but a little lighter than KCLT due to Bonnie`s
influences a little farther away.

Outlook: Bonnie is expected to move very slowly up the coastal
Carolinas over the next several days. Lingering shower chances into
the early part of the week would be greatest at KCLT. Otherwise,
patchy fog chances continue at KAVL each morning, with scattered
afternoon/evening SHRA/TSRA increasing throughout during the week.

Confidence Table...

            21-03z        03-09Z        09-15Z        15-18Z
KCLT       High 100%     High  98%     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 schedule TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:




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