Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 231759

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1259 PM EST Thu Feb 23 2017

Brief drying develops today into early Friday before a significant
cold front brings chances for rain and thunderstorms Friday night
and Saturday. Overall, daytime temperatures will remain well above
normal through Saturday, with a return to normal for Sunday. Above
normal temperatures and chances for rain return for early next week.


As of 1250 PM: The region will remain under the influence of
a somewhat nebulous pressure pattern through tonight, with a
shortwave upper ridge centered over the Southeast, while one sfc
low continues to meander eastward out of Florida, and another
swings into the mid-Mississippi Valley. The net result will be
a continuation of the light southeasterly flow we are currently
seeing, and a midlevel inversion which will serve to trap low-level
moisture and also to limit the depth of convection. Low stratus is
expected to move in during the predawn hours, while some fog may
develop and produce appreciable vsby restrictions (particularly if
the stratus does not form as early as anticipated). A few light
showers may develop over the Blue Ridge but not likely bringing
more than a few hundredths. Mins will remain a remarkable 15 to
20 degrees above normal.


As of 230 AM EST Thursday: A closed low pressure system will move
east over Iowa on Friday while a downstream ridge axis persists over
the southeastern U.S. Under the ridge, moist southerly flow will
continue at low levels, providing some weak upslope triggering along
and near the Blue Ridge. However, profiles appear rather warm and
capped aloft so little to no thunder is expected Friday afternoon.
Very warm temperatures are expected throughout the region as the
lingering nose of surface high pressure dissipates and south to
southwest winds predominate along with warming low level thicknesses.

The low pressure system will lift over the Great lakes through
Friday night and send a cold front into the southern Appalachians.
Breezy to windy conditions will ramp up over the higher terrain of
the NC mountains ahead of the front Friday night as 850 mb southerly
flow increases to around 40 kt. Wind gusts are expected to remain
sub-advisory across all but the very highest peaks in the warm
advection flow regime. The strength of the approaching convection
will be the primary issue, as upstream locations from Kentucky to
central/eastern TN are now in the Day 2 convective slight risk. The
feeling is that the pre-frontal convection will largely run out of
steam as it enters the southern Appalachians and encounters lower
instability, but some gustiness along the TN border counties is
quite possible. The passing surface cold front should cross the
mountains by mid morning on Saturday and move east of the Interstate
77 corridor circa 18z. Any stronger areas of 500 to 1000+ SBCAPE
ahead of the cold front should only briefly intersect with our far
eastern piedmont. 850 to 500 mb lapse rates do briefly surge to
about 6.5 deg C/km there and surface to 3 km bulk shear values may
reach 35 to 40 kt in the unidirectional southwesterly flow early
Saturday afternoon. Severe thunderstorms are not currently expected,
however, as the instability should be greatest off to the east.

Deep layer westerly flow will develop over the region behind the
departing cold front late Saturday through Saturday night as snow
levels fall across the higher terrain of the NC mountains. Upslope
moisture, however, appears rather shallow and winds will be more
westerly in the boundary layer over eastern Tennessee. Any high
elevation snow accumulations overnight Saturday night will be quite


As of 205 AM EST Thursday...starting Sunday morning with cool high
pressure over Tennessee transiting east. This high will be moving
off the Carolina coast late Sunday with southerly return flow
moisture beginning over east Texas to Missouri shifting east into
Monday. There should be a surface low pressure over Arkansas early
Monday.  Some models have around a 10kt 925mb South to SSE flow
across GA and SC which would enhance upslope against our mountains
producing some showers out ahead of the approaching system.  Weak
lows will continue to develop and move NE from the lower Mississippi
Valley through Wed night with some instability late Tues and Wed.
The GFS shows 700 to 900 CAPE along and south of I-85 at both 18Z
Tuesday and 18Z Wednesday with mainly speed shear. At 18Z Wed the
925mb wind is forecast to be SW at 30 to 35kts and 700mb wind
slightly more west at speeds near 50kts. Strong to a few severe
possible. Of course, that is nearly a week away and much can change.
At least some areas should get good rain out of this 3 day event.
The cold front moves through late Wed night with dry high pressure
building into our region from the west going into Thursday.

Temperatures near normal Sunday, rising to around 5 degrees above
Monday then 10 to 15 degrees above Tuesday and warmest on Wednesday.


At KCLT and elsewhere: A low VFR cumulus field will last through
the remainder of the afternoon over most of the area. Light SE
winds will continue between mid-Atlantic sfc ridge and low pressure
entering the Ohio Valley. This moist flow appears likely to bring
in IFR stratus and fog in the early morning hours; cigs are expected
to be more impactful than vsby. (Guidance members showing LIFR vsby
tonight seem to do so due to persistence within a similar flow
regime to what was seen this morning; it looks like the stratus
is likely to form early enough to limit the formation of a fog
layer.) An isolated shower can`t be ruled out over the foothills
during the period but chance at TAF sites is too small to mention.

Outlook: Moist southerly to easterly low-level flow will persist
across the area until a cold front pushes thru on Saturday. This
will keep high chances of morning stratus and possibly fog again
Saturday morning. Drier conditions set up on Sunday.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       High 100%     High 100%     High  87%     Med   77%
KGSP       High 100%     High 100%     Med   74%     Med   77%
KAVL       High 100%     High  90%     Med   60%     High  85%
KHKY       High 100%     High  94%     Med   67%     High  88%
KGMU       High 100%     High 100%     Med   78%     Med   75%
KAND       High 100%     High 100%     Med   77%     Med   75%

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:



  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      76 1982     29 1989     54 1922     10 1939
   KCLT      76 2012     29 1901     56 1944     19 2009
                1980                                1978
                1962                                1963
   KGSP      76 2012     36 1966     57 1922     15 1963
                1996        1939


  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      77 1930     26 1947     50 1985      6 1967
   KCLT      80 1982     26 1889     56 1992     16 1967
   KGSP      79 1982     33 1901     57 1909     15 1967




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