Area Forecast Discussion
Issued by NWS Greer, SC

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462
FXUS62 KGSP 201743
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
143 PM EDT Fri Apr 20 2018

.SYNOPSIS...
High pressure atop the region to start off the weekend will give way
to increasing moisture on Sunday.  Low pressure will then track east
across the area Monday and Tuesday triggering rounds of rainfall.

&&

.NEAR TERM /THROUGH TONIGHT/...
A quiet near term is store as strong sfc hipres is advanced across
the mid-atl region ahead of an h5 s/w ridge. The column will remain
quite dry and no chance of precip let alone clouds will be had
across the FA. Winds will weaken within the BL as well thus there
will be no sigfnt gust potential as well. Mins will cool off
efficiently tonight within very good rad cooling conds and patchy
frost is possible outside the mtns over the NC piedmont. This frost
shud not be widespread enuf for a FR.Y and will be mentioned in the
HWO. However...a FR.Y will be issued for the srn NC mtns and extreme
NE GA where sfc tdd/s will be low enuf for areas of frost formation.
Mins will drop to or just below normal most locales and max temps
Sat will likely be held a couple degrees below normal within a
reinforcing cP airmass.

&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
As of 330 AM EDT Friday: Quiet conditions are expected to prevail on
Saturday as sfc high pressure continues to build in from the Great
Lakes region/OH Valley, with a piece of it breaking off and settling
along the Carolina/VA coast Saturday afternoon as the next
approaching system slowly tracks across the southern Plains. Aside
from passing clouds throughout the day, overall expect Saturday to
be a pleasant Spring day, with high temperatures in the mid to upper
60s to around 70 degrees across much of the area, though cooler in
spots across the mountains. Overnight lows will trend just a few
degrees below normal. While the seasonal weather would be welcome to
stay longer, it seems latest guidance continues to trend towards a
period of increasing clouds, slightly cooler temperatures and
increasing rain chances, extending into the middle part of next week.

As the upper low to the west is progged to propagate across the
southern plains and eastward across the Deep South within split
flow, moisture from the GOM and isentropic lift will aid in the
development and gradual expansion of rainfall throughout the day on
Sunday, SW to NE across the FA. The onset of precip may be a tad
early in the going forecast per the latest trends of the notable
disagreement both temporally and spatially in regards to the system,
but overall suggestion of precip beginning on Sunday stands. The
aforementioned sfc high pressure is expected to move offshore and
wedge back in across the Carolinas, but with latest trends,
anticipate cooler temperatures to hold off until Monday, as for now
have kept with high temperatures on Sunday to be a bit cooler than
that on Saturday as cloud cover increases. Overnight lows Sunday
night into Monday morning will range in the mid to upper 40s/low 50s
across the Upstate and NW Piedmont, and cooler across the mountains.

&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
As of 350 AM EDT Friday: The medium range forecast begins Monday
morning where guidance continues to place a sfc high near New
England wedging back in across the Carolinas, while to the SW of the
FA, a 500 mb low is progged to be pushing across MS/AL as plenty of
moisture continues to stream in across the FA. This along with the
aid of isentropic lift, do anticipate rain to already be falling
across most of the area at the start of the medium range forecast
period, likely lingering through midweek. This with high
temperatures expected to only reach into the mid to upper 50s/around
60 degrees on Monday (into the 40s across the mountains) - it`ll be
a dreary start to the work week to say the least.

As the system slowly propagates into TN/GA and the Carolinas
throughout the day on Monday, the suggestion of a secondary low
developing off the FL/GA/SC coast Monday night by some of the
guidance continues. Details from latest guidance become a bit foggy
through the end of the medium range, but overall, anticipate this
system will linger across the Carolinas Tuesday into early Wednesday
morning as another upper low is projected to sweep across the Upper
Midwest and combine with the exiting system - allowing for both
systems to join within the main upper trough across the eastern US.
While previous guidance suggested the potential for some
thunderstorm activity Tuesday afternoon, it seems latest guidance
keeps the best instability well south and east of the FA, thus have
kept with only rain (showers) attm. As the aforementioned next
system approaches, guidance remains in disagreement in regards to
the amount of moisture and forcing in place as flow becomes
northwest. Thus, for now have kept with the trend of precipitation
tapering off across the area on Thursday. Will mention, am expecting
higher QPF at the beginning of the week, with a downward trend
through into Thursday. Temperatures will begin to rebound on
Wednesday as the wedge breaks down, with temperatures nearing normal
towards the end of the week.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
At KCLT and elsewhere: A strong sfc high will cross the mid/atl and
ridge in from the northeast thru the period. No flight restrictions
will be had as the column remains very dry thru a deep layer. The
sfc flow will remain weak and aligned ne/ly veering to se/ly across
the non/mtns...and maintained down/valley at KAVL.

Outlook: Flight restrictions may develop late Sunday into Monday as
a warm front lifts northward over the area, bringing deeper moisture
up from the Gulf of Mexico.

Confidence Table...

            17-23Z        23-05Z        05-11Z        11-12Z
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

&&

.FIRE WEATHER...
Dry conditions will continue across the area Saturday. Low RH values
combined with dry fuels across northeast Georgia will create
increased fire danger conditions during the afternoon and evening,
thus a Fire Danger Statement may be issued. Elsewhere, while winds
will remain below SPS thresholds, RH values are expected to fall
below 30 percent across Upstate SC and the NC Piedmont/Mountains
Saturday afternoon.

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...Fire Danger Statement until 8 PM EDT this evening for GAZ010-
     017-018-026-028-029.
     Frost Advisory from midnight tonight to 9 AM EDT Saturday for
     GAZ010.
NC...Frost Advisory from midnight tonight to 9 AM EDT Saturday for
     NCZ048-051>053-058-059-062>065-507-509.
SC...None.

&&

$$
SYNOPSIS...JPT
NEAR TERM...SBK
SHORT TERM...SGL
LONG TERM...SGL
AVIATION...SBK
FIRE WEATHER...SBK



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