Area Forecast Discussion
Issued by NWS Greer, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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
000
FXUS62 KGSP 261050
AFDGSP

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
650 AM EDT Tue Sep 26 2017

.SYNOPSIS...
Dry and warm high pressure will remain across the region through the
middle of week...while Hurricane Maria is forecast to remain off the
East Coast. A fairly dry cold front will cross the area Thursday
while pushing Maria out to sea. A secondary cold front crosses
Friday night bringing much cooler and drier air for the weekend into
early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 645 am: Patchy fog/low stratus will lift/scatter within the
mtn valleys by late morning. Otherwise, Stagnant weather pattern
will persist through the near term, as  upper ridging continues to
yield subsidence/weak mid-level lapse rates, while low level ridging
and the broad pressure pattern around Hurricane Maria supports a
relatively dry N/NE flow. However, surface dewpoints are expected to
be sufficiently high to support some weak/shallow buoyancy this
afternoon. This should allow for a healthy cu field across much of
the area, and we would not be surprised to see a brief shower or two
pop across the high terrain this afternoon, but not enough to
warrant a mentionable pop. Meanwhile, cirrus outflow circulating
around Maria is expected to shift east of the forecast area today,
while thicknesses should see a slight increase. This should spell an
across-the-board increase of 1-2 degrees above yesterday`s max
temps, with mid/upper 80s expected across all of the foothills and
Piedmont, and lower/mid 80s in the mountain valleys. Min temps
tonight will remain 5-8 degrees above climo in most locations.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 250 AM EDT Tuesday: The FA will remain quite dry and warm thru
the short range period. Ulvl ridging will be enhanced somewhat by
the departing TC Maria which will make for a convectively
suppressive atmos. The 00z guidance has actually come in drier for
Thu evening/night and this trend was applied to the grids as the
pre-frontal upstream moisture looks very shallow...not to mention
highly uncertain as to how much will make across the TN/NC spine.
Well above normal temps looks pretty certain however as soundings
show very good insol conds with perhaps just few/sct fair-wx Cu Wed
and a little more cloud coverage across the NC mtns Thu afternoon.
Expect max temps pushing 90 F both days across the non/mtns and low
to mid 80s mtn valleys. Mins will be remain about 10 degrees abv
normal Wed night and a few degrees cooler Thu night as drier/cooler
air begins to work in from the NW.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As of 310 AM EDT Tuesday: No sigfnt changes were made to the going
fcst. The op models and ensembles agree well with the synoptic
pattern evolution which features a cold front crossing the FA Fri
then strong cP high pressure building south over the Midwest. Not
expecting much fanfare in our area ahead of the FROPA late Fri. Very
little to no ulvl dynamic support will be had and the llvl wind
fields are non/conducive for moist flux or mech lift. Believe the NC
mtns will see the best chance of -shra during the afternoon which
will be short-lived pulse type and thermally driven in nature.

Other than that...the sensible wx fcst will focus on temps and
dewpoints thru the period. With the first real cP airmass of the
season...noticeably cooler air will move in Fri and become reinforced
over the weekend as the Canadian high centers east and ridges into
the FA. Expect max temps held 5-8 degrees below normal. Dewpoints
will also drop off sigfnt/ly with values ranging in the mid 50s Fri
to the M40s by Sun. Thus...very pleasant conds are in store Fri-Sun.
A strong dry-onset wedge develops Mon and some measure of moist e/ly
flow will adv into the area. This combo of llft/moisture will likely
result in more cloudiness and a perhaps a shot of some low-end
precip across the srn escarpment. Most areas should remain dry
however.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
At KCLT and elsewhere: VFR is forecast through the next 24 hours at
the main TAF sites. Some fog/low stratus has formed in the French
Broad Valley up and down-valley of KAVL, but it now appears unlikely
to impact the terminal this morning. Otherwise, an area of IFR/low
MVFR stratocu will make a run toward the western NC Piedmont this
morning, but it should stall/scatter/lift before reaching KCLT. NE
winds will increase to around 10 kts at most terminals this morning,
then diminish again this evening. SCT cumulus in the 040-050 range
expected to develop this afternoon near KCLT, possibly expanding as
stratocu and lingering through the evening.

Outlook: Dry conditions are expected most of the week. Under mostly
clear skies and calm conditions, fog and/or low stratus are possible
in the mountain river valleys each of the next few mornings. A
mostly dry cold front will cross the region late in the week.

Confidence Table...

            10-16Z        16-22Z        22-04Z        04-06Z
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  91%
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

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...None.
NC...None.
SC...None.

&&

$$
SYNOPSIS...SBK
NEAR TERM...JDL
SHORT TERM...SBK
LONG TERM...SBK
AVIATION...JDL


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