Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 160337

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
1037 PM EST Thu Feb 15 2018

Warmer high pressure will linger to our southeast through the end of
the work week, bringing well above normal temperatures. A cold front
will approach from the northwest on Friday, bringing increased rain
chances. A wave of low pressure will develop along the front over
the weekend, keeping some chance of rain for our area through early
next week.


As of 10pm EST Thursday:  Radar is still clear this evening over the
entire southeast CONUS, and will, thus, keep POPs out of the forecast
through 8Z, despite models putting light precipitation over the
mountains ahead of the next system due in Friday afternoon.

A strong, flattened upper high over the Gulf of Mexico is
maintaining zonal flow aloft and strong southwesterly flow at low
levels that will continue a warm, moist advection pattern until
Friday afternoon when a major cold front will enter the area.  Front
is associated with an upper shortwave which should combine to
produce some precipitation with the frontal passage.  Current timing
on the front has it crossing the southern Appalachia about 2pm, and
progressing towards the southeast across the area, exiting the CWA
by 10pm.  Though models produce some light precipitation ahead of
the front, more significant precip is anticipated along and behind
it.  Even so, upper forcing is weak, and models do not develop much
QPF with the FROPA, with rain most likely in the higher terrain, and
piedmont areas receiving scattered amounts less than a tenth of an
inch.  With good northerly flow behind the front, upslope
enhancement will produce the most precipitation on the northwest
side of the mountain range.

850mb flow has been quite strong all day, and will continue until
FROPA, after which winds will veer to northerly and drop to 10kts or
so.  Pre-frontal temperatures will again be unseasonally warm at 10
to 20 degrees above normal.  Depending on timing of front and extent
of cloud cover, high temperatures may approach records, especially
in piedmont areas.  Tomorrow`s lows at 20 to 30 degrees above
normal, will be at or above record territory for record warm lows,
but will ultimately not count as records as temperatures drop behind
the front, with temperatures dropping quite a bit to the lows of the
day at midnight.


As of 215 PM EST Thursday: The unsettled weather continues through
the short term, along with the temperature swings. At the beginning
of the period, a cold front will be just SE of the area, with CAA
slowly filtering in behind it as an area of cool high pressure
begins building in from the Midwest. Precip lingering behind the
cold front will be broken up by the mountains as the front elongates
E-W across the area. The surface high will cross the mountains,
pushing toward New England Saturday night, and will ridge down the
Eastern Seaboard in a fairly transitory damming pattern for
Saturday. The cold front will push S/SW as a wedge front, with highs
on Saturday at LEAST 15-20 degrees...and in some places pushing 30
degrees...cooler than what we`ll see tomorrow.

Isentropic upglide atop the surface cool dome will allow for
continued cloudiness and perhaps some drizzle or light rain early
Saturday, especially across SW zones. Meanwhile another shortwave
traversing the Plains will lift another slug of moisture up out of
the Gulf and toward the TN Valley, pushing across our area Saturday
afternoon and evening. The bulk of the moisture will lift to the NW
and N as the wedge front erodes Saturday, with the highest QPF
amounts (about an inch) along the TN state line. The the wave will
lift out as quickly as it came in by early Sunday morning.

As is often the case, behind the scouring cold front, temperatures
will be warmer on Sunday than on Saturday, a good 5-6 degrees above
seasonal normals and perhaps as much as 10 degrees warmer than
Saturday`s highs. The best part is that we have a decent chance of
seeing a good amount of sunshine during the day on Sunday as another
surface high crosses the mountains and pushes into NC/VA by Sunday
afternoon. We rinse and repeat at this point as another wave
crossing the Plains lifts moisture out of the Gulf and toward the TN
Valley by the end of the period.


As of 150 PM EST Thursday...The ext range begins with an insitu
wedge and weak isent lift -shra across most of the FA. With little
upper support...these showers will remain low-end. The wedge begins
to break down aft 18z or so and sfc winds become s/ly. Thus...will
expect max temps to reach a couple cats abv normal. The large scale
pattern will remain fairly steady state thu the rest of the period
as a strong ST high slowly advances toward the southeast coast and a
wrn cold front develops over ern TN by Wed. The models continue to
show good mlvl subs/drying with the increased ST ridging. Low-level
flow will remain moist Tue...however with less isent
forcing...showers will be weak and generally confined across the srn
BR in mech lift. With the dry mid-level air and increasing
pre/frontal lift...isol/sct general tstms are possible Wed afternoon
over most locales. All in all...a warm and moist airmass will engulf
the area with max temps arnd 70 F and td/s remaining arnd 60 F


At KCLT and elsewhere:

Brisk 850mb flow is keeping moderate southwesterly winds with gust
of 20 to 25kts.  Gusts make weaken a little list evening, but
strength of flow below inversion will be strong for some gusts to
continue all night.  Winds will make the formation of fog difficult,
except at the more sheltered KAVL site.  Continued moisture
advection will bring some lowered CIGs tonight and tomorrow morning

A cold front passes through from northwest to southeast Friday
afternoon which will veer winds around to northerly by Friday
evening.  Post frontal winds will actually be weaker, at around
10kts.  Frontal passage will also be accompanied by scattered fairly
light showers, which end by 3z.

Outlook: A cold front will bring shower chances to the area
(especially the mtns) Friday afternoon/evening. The weather will
remain periodically unsettled, with periods of restrictions likely
into at least early next week.

Confidence Table...

            03-09Z        09-15Z        15-21Z        21-00Z
KCLT       Med   61%     High  81%     Low   55%     High 100%
KGSP       Med   66%     High  89%     Med   62%     High 100%
KAVL       High 100%     High 100%     High  98%     High  93%
KHKY       High 100%     Low   59%     High 100%     High 100%
KGMU       Med   66%     High  88%     Med   64%     High 100%
KAND       Med   74%     High  98%     Med   68%     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:



  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      74 1989     18 1905     55 2001      5 1943
   KCLT      80 1989     32 1943     60 1909     12 1943
   KGSP      75 1989     30 2016     57 2001     -3 1899


  STATION      HIGH        LOW         HIGH        LOW
  -------  ----------  ----------  ----------  ----------
   KAVL      72 2001     18 1958     51 1990      2 1905
   KCLT      76 1976     28 1969     60 1990     11 1905
   KGSP      80 1911     32 1958     59 1990      9 1958




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