Area Forecast Discussion
Issued by NWS Greer, SC

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534
FXUS62 KGSP 280604
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
204 AM EDT Fri Apr 28 2017

.SYNOPSIS...
Warm and humid high pressure will build in through the end of the
work week. A front will move into the area late this weekend,
increasing chances for showers and thunderstorms on Sunday. Another
front will approach by the middle of next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 150 AM EDT: Mid and upper level drying atop a very moist
boundary layer is leading to areas of fog developing across the
region, and dense fog could become more widespread by daybreak.
Given the spatial and temporal variability to the patchy dense
fog, will continue to feature Special Weather Statements through
the early morning hours, but a Dense Fog Advisory could be
needed at some point.

Otherwise, deep layer southwesterly flow is in place aloft over the
southeast, with a weak surface boundary stalled over the western
Carolinas. Any thermal/moisture contrast across this boundary should
continue to dissipate through the day. Upper level heights will
gradually rise over the area as an offshore ridge axis becomes
resurgent. Little to no upper level triggering should be avialable
through the period. Very warm profiles in the 5 to 10 kft layer
should effectively cap off deep convection, which is fortunate since
elevated CAPE above the capping looks very robust this afternoon.
Will keep any any isolated shower mention confined to the immediate
southerly upslope areas this afternoon. Temperatures should rebound
solidly into the 80s today, with some lower mountain valleys just
about as warm as piedmont sections this afternoon in the southwest
flow. Another mild night with areaas of fog is expected again
tonight.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY/...
As of 200 AM Friday: Stacked Bermuda High ridging dominates the
pattern over the FA thru the short range. By Sat afternoon...a 593
DM high will be positioned off the Atl coast and the associated llvl
high will ridge into wrn GA. Return flow around the sfc high will
bring just enuf moisture to the area for mainly upslope -shra/tstms.
The NAM is still dry during this time...so pops are held low. The
models show mod/stg sbCAPE in a low shear environ...so expect some
pulse stg/svr storms into the late afternoon. Max temps will be in
the mid to upper 80s non mtns. On Sun...the sfc ridging eases off
slightly...but enuf to allow better GOM moisture flux across the wrn
zones. Max temps will be a bit lower due to increased moisture...but
td/s remain high. Soundings show much less instability...but shear
will be slowly increasing thru the overnight period. Think there
will be enuf destabilization for another round of pulse type tstms
with a bit better coverage than Sat.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
As of 235 PM EDT Thursday...the extended fcst picks up at 00z on
Monday with steep upper ridging centered just off the Atlantic Coast
and a deep upper trof moving across the Southern Plains and into the
Mississippi River Valley. As the trof approaches our area, it is
expected to lift NE and up over the Great Lakes by early Tuesday.
Over the next 24 hrs or so, the trof lifts farther NE over southern
Ontario/Quebec as heights begin to recover over the southeast.
During the remainder of the period, a southern stream upper trof
amplifies over the ArkLaTex region and encroaches upon our fcst area
by the end of the period late Thursday. At the sfc, warm sly flow
will persist across the area into early Monday. The next frontal
system will move thru the fcst area sometime Monday morning to
Monday afternoon bringing with it a good chance for widespread
showers and ts. Drying high pressure will overspread the area in the
front`s wake on Tues with another frontal system approaching the
CWFA by the end of the period on Thurs.

&&

.AVIATION /06Z FRIDAY THROUGH TUESDAY/...
At KCLT: Lingering stratocumulus has served to keep developing fog
and stratus at bay thus far early this morning, but drying aloft
should allow a quick transition down into LIFR conditions through
daybreak. Low clouds and fog will be slow to scatter through the
morning hours, with recovery to VFR not likely until around 16Z.
Expect some low end gusts in the SSW flow with mixing this
afternoon. Warm profiles aloft should preclude any afternoon
convection near the airfield.

Elsewhere: Low clouds and fog have already developed at the mountain
and foothill TAF sites, with LIFR to VLIFR conditions likely through
daybreak given the drying aloft atop a moist boundary layer.
Anticipate very slow recovery through the morning hours, with lower
end VFR conditions not likely until around 16Z most locations.
Expect S to SW winds generally less than 10kt throughout, but with a
few low end gusts possible with mixing this afternoon.

Outlook: Areas of fog will be possible each morning as the near
surface layer remains moist through the weekend. Diurnally-based
showers and thunderstorms will possible Saturday and Sunday, with
more organized thunderstorms possible by Monday.

Confidence Table...

            06-12Z        12-18Z        18-24Z        00-06Z
KCLT       Med   61%     Med   78%     High  93%     High 100%
KGSP       Med   61%     Med   65%     High  91%     High  97%
KAVL       Low   53%     High  83%     High  98%     High  97%
KHKY       Low   50%     Med   66%     High  80%     High 100%
KGMU       Med   65%     Low   55%     High  90%     High 100%
KAND       Low   55%     High  84%     High  90%     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...LEV
NEAR TERM...HG
SHORT TERM...JPT
LONG TERM...JPT
AVIATION...HG



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