Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 241830
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
230 PM EDT Mon Jul 24 2017

.SYNOPSIS...
A surface front will become stationary from west to east across our
region and dissipate into mid week.  High pressure moving by to the
north is expected to provide cooler temperatures on Wednesday.
Another front will move in from the northwest late in the week.

&&

.NEAR TERM /THROUGH TUESDAY/...
As of 210 PM EDT Monday: Afternoon clouds have kept a lid on heating
and convection. However, they are scattering out and moving east
allowing instability to develop. Latest CAM guidance shows best
chance of convection over NE GA and the western Upstate where
heating develop first and instability can develop before sunset.
Have updated PoP to show these trends. Cannot rule out an isolated
severe downburst this afternoon as DCAPE values rise with heating.
However, chance is much lower than yesterday.

Any convection that develops should be diurnal in nature and
diminish quickly with loss of heating this evening. Mountain valley
fog and stratus, some dense, will develop once again. Fog and
stratus should develop in the normally more foggy areas outside of
the mountains as well. Lows will remain above normal similar to this
morning`s readings.

Diurnal convection expected to develop Tuesday with better chances
along and south of the I-85 corridor and the GA, SC, and SWRN NC
mountains where better moisture and instability develop. DCAPE and
sfc delta theta-E values will again be on the high side, so an
isolated severe downburst is possible, mainly in the areas where
better coverage is expected. Highs will rise back into the lower 90s
outside of the mountains and into the upper 80s for many mountain
valleys.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
As of 215 PM Monday: The short term will feature rising heights, as
the upper trough axis pushes away from the area and weakens, while
the upper ridge associated with SW Conus subtropical high builds
back into the area, only to become suppressed again by the end of
the period. Despite this, Wednesday is expected to see temps a
little below climo, as a weak surface boundary associated with a
ridge of high pressure nosing down the East Coast is forecast to
turn the low level flow to the E or SE across the area. This
boundary could provide a focus for diurnal convection, although a
model consensus indicates the wind shift could be south of the
forecast area by the time of peak heating. The highest pops Wed
afternoon will be featured across the extreme southern zones and
along the southern Blue Ridge escarpment, with generally 30 pops
advertised elsewhere.

Height falls commence by the end of the period, as a short wave
trough pushes across the northeast quadrant of the country. Low
level flow is expected to return to the SW across our area by Thu
afternoon, allowing temps to return to normal levels. Otherwise,
standard mid-summer diurnal convective coverage is anticipated Thu
afternoon (40-50% across the Blue Ridge areas, generally 30 percent
elsewhere).

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
As of 155 PM Monday: The medium range begins Thursday evening with
heights falling in the east while the semi-permanent ridge remains
over the desert southwest.  A strong wave or closed 500mb low moving
east to far eastern Canada brings the falling heights to our region
and a surface cold front which will be near the Ohio River early
Friday. As the front approaches from the north on Friday, showers
and storms will be most active with the greatest coverage of any day
in the medium range. The front will be moving slowly south as it
stalls out on Saturday then remain west to east across our region
into the start of next week. 500mb trough becomes rather deep for
this time of the year to start next week and likely give upper
support for moving the surface front south of our area. This would
lower the chances of rain for the Carolinas and northeast GA for
Sunday.  This pattern of amplified trough over the East and big
ridge over the West will result in cooler than normal temperatures
for our area and hotter than normal for Desert Southwest and
Rockies.

Max Temperatures are forecast to be just below normal Friday then
cool to be about 5 degrees below on Monday.  Min Temperatures will
be close to normal with the moisture and clouds.

&&

.AVIATION /19Z MONDAY THROUGH SATURDAY/...
At KCLT and elsewhere: Mid clouds will slowly move east of the area
with developing Cu. Latest guidance keeps best chance of afternoon
convection across the SC sites. Have limited any TS mention to those
locations, but did keep a VCSH at KCLT. Cu diminishes this evening
with cirrus the main clouds overnight. That said, mountain valley
fog/stratus is likely and possible at KHKY/KAND. After any
restrictions burn off Tuesday morning, expect developing Cu once
again. Any convection would be later in the day and more likely for
the SC sites. W to SW wind today becomes light N overnight and NE
Tuesday. KAVL remains NW throughout.

Outlook: Scattered diurnal convection can be expected each day this
week across the region. Chances for morning fog and stratus will
also be possible each day in the mountain valleys.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High 100%     High 100%
KGSP       High 100%     High 100%     High 100%     High 100%
KAVL       High 100%     High  97%     Med   79%     High  92%
KHKY       High 100%     High 100%     High  91%     High  94%
KGMU       High 100%     High 100%     High 100%     High 100%
KAND       High 100%     High 100%     High  91%     High  94%

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...RWH
SHORT TERM...JDL
LONG TERM...DEO
AVIATION...RWH


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