National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

-- Discussion containing changed information from previous version are highlighted. --
234
FXUS62 KGSP 131930
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
230 PM EST Fri Dec 13 2019

.SYNOPSIS...
A strong upper disturbance will cross the area tonight, bringing one
last round of rain showers. Then high pressure gradually builds in
Saturday through Sunday. Another wet cold front will traverse the
area Monday into Tuesday followed by dry and cool Canadian high
pressure building in Wednesday through Thursday.

&&

.NEAR TERM /THROUGH SATURDAY/...
As of 2:25 PM Friday: temps have warmed above freezing across the
CWFA over the past couple of hours, thus we decided to cancel the
Winter Wx Advisory a bit early. Widespread showers continue across
most of the non-mountain zones with isolated showers over the mtns.

Otherwise, broad upper trofing will continue to amplify over the
Mississippi River Valley this evening and overnight. The upper trof
will take on a more negative tilt as it approaches our fcst area
tomorrow morning. The trof axis is expected to lift over our area
tomorrow afternoon and just to our Northeast as the period ends late
tomorrow. At the sfc, high pressure will continue to drift farther
off the coast of Nova Scotia this evening. Low-lvl winds will remain
NELY, outside of the mountains, as the wedge hangs on and moist
upglide continues well into the evening. At the same time, a broad
low pressure system will lift out of the NE Gulf of Mexico and move
over the Carolina Coast later tonight and into tomorrow morning.
The low will track up the mid-Atlantic Coast thru the day tomorrow,
and move over Western New England tomorrow night. As it does, low-lvl
winds will become SWLY and then WLY as the pressure gradient tightens
and speeds pick up over the area. Currently don`t anticipate winds
reaching Advisory levels, however elevations above 4000ft could see
some 35 to 45 mph gusts tomorrow. In addition, solid-chance to likely
PoPs will linger over the higher terrain thru tomorrow afternoon, due
to the moist return flow from the backside of the above-mentioned
departing low. Temps will change little tonight and thru tomorrow
morning with lows just a few degrees cooler than today`s highs.
With the wedge having dissipated and cloud cover diminishing, highs
tomorrow are expected to climb a few degrees above climatology.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
As of 230 PM EST Friday: Quasi-zonal flow will briefly set up across
the CONUS, as one trough lifts NE out of New England, while another
digs into the Pacific Coast. A modest air mass will build in across
the region Saturday night thru Sunday, resulting clearing skies and
near to slightly above normal temps. Whatever NW flow snow shower
activity there may be lingering Saturday evening, should wrap up by
daybreak Sunday. Only minor snow accums are expected.

The western CONUS upper trough will progress into the Southern
Plains Sunday night thru Monday, inducing cyclogenesis near the
ArkLaTex region. The low pressure system will activate a warm front
across the TN Valley and Carolinas, but will have little moisture to
work with. Deep-layer SWLY flow will likely bring an increase in
high clouds and possibly low stratus by daybreak Monday across
portions of the forecast area. At the very least, strong LLVL WAA
will keep temps about 8-10 deg above normal. Moisture begins to
deepen enough in the SWLY flow for some upslope showers in the
mountains during the aftn hours, but the eastern half of the
forecast area is expected to be largely dry thru the day. Highs will
be in the mid 50s to mid 60s.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
As of 230 PM EST Friday: A progress, positively tilted upper trough
will cross the eastern CONUS Monday night thru Wednesday. The
associated sfc low pressure system will track NE across the OH
Valley to New England, dragging a trailing cold front thru the
Southern Appalachians to the Carolina coast. The front looks like
another anafront (like the one we had earlier this week). This means
the bulk of the forcing and moisture is on the the cold side of the
front. So instability will be lacking once again, and a brief
changeover to snow in the highest peaks on the backside of the
precip is expected. There is some disagreement on the exact timing
of the front, with the GFS a little fast, and new EC coming in a
little slower. But right now, it looks like the highest pops will be
Monday night thru the first half of Tuesday. The front is a little
faster-moving than the previous couple of fropas, and so QPF looks
to be 1-2" across the SWLY upslope flow areas of western NC and the
SC/GA mountains. But the rest of the area looks to get around 0.5".
There is doubt on whether there will be any moisture left for snow
at the tail-end of the precip Tuesday night, but if so, accums would
be very light and confined to the highest elevations near the TN
border.

Temps start out well above normal Monday night just ahead of the
front, but cool to near or slightly below normal by Wednesday
morning with skies clearing out. The center of Canadian high
pressure will settle over the forecast area Thursday, then shift
slightly east to the Outer Banks on Friday. The last few runs of the
GFS continue to be really fast with the next system, having a
southern stream low pressure system cross the area late Friday into
Saturday. But the last few runs of the EC have not shown this system
at all, and keep dry high pressure in control of the Southeast.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
At KCLT and Elsewhere: conditions range from MVFR to LIFR as
precip continues to move across the fcst area from the SW. I
expect a mixture of MVFR to IFR to persist into the evening,
with predominately IFR conditions settling in for the overnight
and early morning tomorrow. Intermittent periods of LIFR will
be possible at most sites beginning around midnight, if not
just before. I used TEMPOs to reflect the most likely periods
of LIFR for the overnight/early morning. Most sites should
return to VFR, or at least MVFR, by late morning, however
MVFR cigs will likely linger over KCLT and KAVL well into the
afternoon. NLY to NELY winds will continue into the evening
outside of the mountains and become light later tonight. They
pick back up out of the SW tomorrow morning and remain SWLY
to WLY thru the day. Winds at KAVL will favor a SELY to SLY
direction thru the evening and become NWLY overnight. They
will remain NWLY thru the remainder of the period.

Outlook: Restrictions may continue well into Saturday as another
trof of low pressure arrives from the west. Dry/VFR conditions
will then return behind a cold front through Sunday and persist
until the next front arrives Monday night or Tuesday.

Confidence Table...

            19-01Z        01-07Z        07-13Z        13-18Z
KCLT       High  86%     Med   77%     High  82%     Med   71%
KGSP       High  86%     Med   76%     Med   68%     Med   75%
KAVL       High  88%     High  82%     Med   73%     Med   72%
KHKY       High  94%     Med   77%     Med   79%     Med   79%
KGMU       High  80%     Med   76%     High  81%     High  81%
KAND       Med   69%     Med   70%     Med   77%     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...ARK
NEAR TERM...JPT
SHORT TERM...ARK
LONG TERM...ARK
AVIATION...JPT