Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

FXUS62 KGSP 200806

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
406 AM EDT Tue Mar 20 2018

A complex low pressure system will cross the region from the west
today. Colder air will spill southward into the region behind the
system, with mountain snow showers returning tonight, and scattered
snow showers possibly extending east of the mountains early
Wednesday. Drier high pressure will briefly return over the area on
Thursday, but with another moist low arriving from the west for the


As of 345 AM: A triple point low center moving east of the CLT metro
area will abruptly end thunder chances in the piedmont early this
morning. Only scattered showers should linger near the northern tier
in a region of weak convergence and deeper moisture as a dry slot
begins to work in from the southwest through daybreak. Other than
morning low clouds and fog, conditions should be fairly dry around
the region through the late morning hours until showers redevelop
from the west under the approaching upper trough axis this afternoon
and evening. Some embedded thunder, and possibly small hail toward
evening, are expected with the afternoon convection as lapse rates
steepen aloft.

The closed upper low will move from the central Appalachians tonight
to the Delmarva coast through Wednesday. The complicated surface low
pressure system will continue to occlude overhead, with steadily
cooling temperatures from the high terrain down toward the lower
valleys this evening through the overnight. Snow levels will crash
quickly across the mountains from the west tonight and then cold air
will continue to spill southward west of the low through Wednesday
as northwest upslope flow moisture becomes rather robust and winds
increase. The Winter Storm Watch will be migrated to a Warning for
all but Jackson County, and will tack on an Advisory tier for the
rest of the NC mountains except Transylvania and Henderson for now.
Will feature these counties, along with Rabun GA, in the HWO since
an advisory could be needed at some point. In addition, moisture
breaking containment east of the mountains, along mainly the I-40
corridor but possibly into Charlotte, could produce some snow
showers early Wednesday. It appears too early for an Advisory there.
Will also wrap advisory level wind gusts into the mountain products.


As of 350 AM Tuesday: The northwest upslope flow moisture into the
southern Appalachians will steadily taper off by daybreak Thursday,
but winds in the cold advection will remain quite strong through
most of the night and yield some advisory level gusts. Otherwise,
deep layer northwest flow will continue through Thursday, with drier
surface high pressure briefly setting up through Thursday night.
Another slug of moisture will arrive back into the region from the
northwest Thursday night through Friday, warranting mainly mountain
showers. Temperatures will remain a below climo through the period.


As of 400 AM Tuesday: A flat upper ridge will persist over the
southeast U.S. Saturday through Monday. However, a warm front will
reactivate from the western Carolinas to the upper Midwest. In the
resulting upglide, northern tier temperatures will be interestingly
chilly over the weekend. A rain/snow mix mention will be featured
mainly north of I-40 for primarily Saturday, and then just along the
Blue Ridge for early Sunday. Cool, wedge-like temperatures will be
possible with a fropa on Monday.


At KCLT: Thunderstorms are rapidly ending from the west circa 08Z
this morning, and no additional convection should be needed aside
from a few lingering VCSH. IFR cigs will likely fill in this
morning, then slowly lift to VFR through early afternoon. Another
round of scattered showers, with perhaps isolated thunderstorms, is
expected this afternoon and evening under the passing upper trough.
Expect SW to WSW winds through the day, becoming northerly tonight
with restrictions returning behind the departing low pressure.

Elsewhere: Thunderstorms have ended across KAVL and the foothill
sites, but with lower restrictions likely to continue filling in
through the morning hours given the saturated boundary layer and mid
level drying working in from above. Expect some lifting through MVFR
to perhaps lower VFR by early afternoon. Additional showers will
redevelop from the west with the appraoching trough, but confidence
is currently too low to advertise thunderstorms. Expect mainly SW to
WSW winds east of the mountains, but with NW flow at KAVL and KHKY.
Winds will turn NW to N throughout tonight, with gusts developing
over the high terrain. Mountain snow showers may start to mix in
near KAVL at the end of the period.

Outlook: Colder air wrapping around the exiting system will bring
snow to the mountains through at least Wednesday, and potentially
mixed precip to KHKY and KCLT Wednesday morning, with rain showers
expected elsewhere. MVFR/IFR is anticipated, with VFR returning
gradually Wednesday night through Thursday. Another moist system
will arrive from the west this weekend.

Confidence Table...

            08-14Z        14-20Z        20-02Z        02-06Z
KCLT       Med   77%     Med   77%     High  92%     High  90%
KGSP       Med   66%     High  87%     High 100%     High 100%
KAVL       High  80%     High  95%     High 100%     Med   73%
KHKY       Med   78%     Med   73%     Med   72%     Med   74%
KGMU       Med   70%     High  93%     High 100%     High 100%
KAND       Med   63%     High  93%     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:


NC...Winter Weather Advisory from 8 PM this evening to 8 AM EDT
     Thursday for NCZ053-059-062-063-501-503-505.
     Winter Storm Warning from 8 PM this evening to 8 AM EDT
     Thursday for NCZ033-048>052-058.


AVIATION...HG is the U.S. government's official web portal to all federal, state and local government web resources and services.